The paper proposes a luminaire design for installation in suspended ceiling systems. The proposed layout reflects current requirements for luminaires used in such ceilings. The developed luminaire employs RuSID LEDs of Russian manufacture, SID 3030 EMC series, and a Russian-made LRD‑040‑0400‑000‑01-D driver as the power supply. The design process explicitly accounts for the spacing between the LEDs and the diffuser. A relationship has been established between the luminaire's photometric parameters and how close the LEDs are to the luminaire's output aperture ("window"). This relationship supports the development of similarly configured luminaires while meeting specified light-distribution requirements. It is particularly relevant for suspended ceiling applications, where ceiling shapes and dimensions vary widely and therefore call for purpose-built structural solutions in the luminaire.
The practical value of the work lies in developing a unified luminaire concept for public lighting, suitable for suspended ceiling systems of different tiers and structural types, with due regard for how the position of the LEDs inside the housing affects the light distribution of the engineered product. The work presents both basic design principles for semiconductor-based luminaires and a parallel design method tailored to luminaires. The scientific and applied contribution is aimed at improving approaches to modern luminaire engineering and at formulating foundational principles for a structured design methodology for LED luminaires used in public lighting.

1. Burmister, Ye. Luminaire / Russian Federation Patent for Invention RU 2548473 C2, 20 Apr. 2015. Appl. No. 2013105494/12, 16 Jun. 2011.
2. Romanov, O. V., Melnik, D.A. Device for mounting a suspended luminaire on a stretch ceiling / Russian Federation Utility Model Patent RU 159929 U1, 20 Feb. 2016. Appl. No. 2015112235/05, 3 Apr. 2015.
3. Vorozheykin, G. Yu. Suspended luminaire / Russian Federation Utility Model Patent RU 226233 U1, 28 May 2024. Appl. No. 2024102822, 11 Feb. 2024.
4. Vladimirov, I. A., Stavinov, V.I. Modular luminaire for a suspended ceiling / Russian Federation Patent for Invention RU 2418236 C1, 10 May 2011. Appl. No. 2009130706/07, 11 Aug. 2009.
5. Ceiling luminaires in modern architectural and engineering design // Eurasian Science distance-learning portal [online resource]. URL: https://e-nauka.kz/potolochnye-svetilniki-v-sovremenno/ (accessed 15 Feb. 2026).
6. Standard GOST 34819‑2021. Luminaires. Photometric requirements and test methods: interstate standard / Order of the Federal Agency for Technical Regulation and Metrology No. 28‑st, 20 Jan. 2022; effective 1 Jul. 2022; developed by LLC "VNISI". Moscow: Russian Institute for Standardization, 2022. 54 p.
7. Aizenberg, Yu. B. Fundamentals of luminaire design: university textbook / Yu. B. Aizenberg. Moscow: Energoatomizdat, 1996. 704 p.
8. Baineva, I.I. Calculation and design of luminaires with LEDs: university textbook / I.I. Baineva. Saransk: Mordovia State University, 2019. 156 p.
9. Varfolomeyev, L.P. On the efficiency of using LEDs in lighting installations [Ob effektivnosti primeneniya svetodiodov v osvetitel'nyh ustanovkah] // Svetotekhnika, 2012, No. 6, pp. 22–25.
10. Bogdanov, A.A. Control of parameters and quality of light emitting diodes as well as their compound products in high-volume production // Light & Engineering, 2015, Vol. 23, # 2, pp. 49–59.
11. Marinichev, D. V., Nizovskiy, L. V., Orlovskiy, V. N., Kholodilov, V.I. Design features and parameters of the cooling system for a high-power LED luminaire [Ob osobennostyah konstrukcii i parametrah sistemy ohlazhdeniya moshchnogo osvetitel'nogo pribora na svetodiodah] // Svetotekhnika, 2013, No. 3, pp. 29–32.
12. Ivliyev, Yu. V. LED ceiling luminaire / Russian Federation Patent for Invention RU 2551437 C2, 27 May 2015. Appl. No. 2013115815/07, 9 Apr. 2013.
13. Nesterkina, N. P., Kovalenko, O. Yu., Zorkin, N. A., Zhuravlyova, Yu. A., Turkin, A.N. Experimental combined irradiator [Eksperimental'nyj kombinirovannyj obluchatel'] // Svetotekhnika, 2026, No. 1, pp. 9–13.
14. Kuznetsov, Ye. A., Nesterkina, N. P., Zhuravleva, Yu. A., Mikayeva, S.A. Lighting of public premises [Osveshchenie obshchestvennyh pomeshchenij] // Automation. Modern Technologies, 2022, Vol. 76, No. 8, pp. 352–354.
15. Danilko, A. V., Karev, A. V., Kornyakov, S.O. Accounting for non-uniformity of chromaticity in the manufacture and operation of LED luminaires [Voprosy uchyota neodnorodnosti cvetnosti izlucheniya pri proizvodstve i ekspluatacii osvetitel'nyh priborov so svetodiodami] // Svetotekhnika, 2022, No. 3, pp. 4–9.
16. Delyan, R. A., Erokhin, M. M., Markova, S. N., Potapov, A. S., Savitskaya, A., Terekhov, G. P., Turkin, A.N. Choosing a method for approximating the spectral distribution of colour LEDs and comparing their parameters and characteristics in nominal mode // Light & Engineering, 2023, Vol. 31, # 3, pp. 52–60.
17. RuSID – Russian LED manufacturer. SID‑3030 (3 V) EMC series [online resource]. URL: https://www.rusid.pro/medium-power-leds/seria-sid‑3030–3v-emc (accessed 15 Feb. 2026).
18. Bugrov, V. Ye., Vinogradova, K. A. LED optoelectronics: university textbook / V. Ye. Bugrov, K.A. Vinogradova. St. Petersburg: ITMO University, 2013. 174 p.
19. Long, T., Liu, M., Shen, X. Computer-aided study of the effect of structural parameters on the efficiency of LED luminaires with a reflector [Komp'yuternoe issledovanie vliyaniya konstruktivnyh parametrov na KPD svetil'nikov so svetodiodami i otrazhatelem] // Svetotekhnika, 2013, No. 3.

1. Watson, N.R., Scott, T.L. and Hirsch, S.J. Implications for distribution networks of high penetration of compact fluorescent lamps // IEEE transactions on power delivery, 2009, 24(3), pp. 1521–1528. Doi: 10.1109/TPWRD.2009.2014036
2. International Electrotechnical Commission, 2000. Electro-magnetic Compatibility (EMC)-Part 3: Limits-Section 2: Limits for Harmonic Current Emissions. IEC 61000‑3‑2.
3. Verderber, R.R., Morse, O.C. and Alling, W.R. Harmonics from compact fluorescent lamps // IEEE Transactions on industry applications, 1993, 29(3), pp. 670–674. Doi: 10.1109/28.222443
4. Pileggi, D. J., et al. The effect of modern compact fluorescent lights on voltage distortion // IEEE Transactions on Power Delivery 8.3,1993, pp. 1451–1459. Doi: https://doi.org/10.1109/61.252672
5. Arseneau, R. and Ouellette, M. The effects of supply harmonics on the performance of compact fluorescent lamps // IEEE Transactions on Power Delivery, 1993, 8(2), pp. 473–479. Doi: 10.1109/ICHPS.1992.559043
6. Topalis, F.V. Efficiency of energy saving lamps and harmonic distortion in distribution systems // IEEE Transactions on Power Delivery, 1993, 8(4), pp. 2038–2042. Doi: 10.1109/61.248319
7. Chen, M.T. and Fu, C.M. Characteristics of fluorescent lamps under abnormal system voltage conditions. Electric power systems research, 1997, 41(2), pp. 99–107. Doi.org/10.1016/S0378‑7796(96)01165‑0
8. Nassif, A.B. and Xu, W. Characterizing the harmonic attenuation effect of compact fluorescent lamps. IEEE Transactions on power delivery, 2009, 24(3), pp. 1748–1749. Doi: 10.1109/TPWRD.2009.2021022
9. Ćuk, V., Cobben, J.F.G., Kling, W.L. and Timens, R.B. An analysis of diversity factors applied to harmonic emission limits for energy saving lamps // In Proceedings of 14th International Conference on Harmonics and Quality of Power-ICHQP, 2010, pp. 1–6. IEEE. Doi: 10.1109/ICHQP.2010.5625406
10. Calleja, A.J., Alonso, J.M., Ribas, J., Corominas, E.L., Rico-Secades, M. and Sebastián, J. Design and experimental results of an input-current-shapers based electronic ballast // IEEE transactions on power electronics, 2003, 18(2), pp. 547–557. Doi: 10.1109/IAS.1999.799967
11. Dalla Costa, M.A., Do Prado, R.N., Seidel, A.R. and Bisogno, F.E. Performance analysis of electronic ballasts for compact fluorescent lamp // In Conference Record of the 2001 IEEE Industry Applications Conference. 36th IAS Annual Meeting (Cat. No. 01CH37248), Vol. 1, pp. 238–243, IEEE. Doi: 10.1109/IAS.2001.955417
12. Wu, T.F. and Yu, T.H. Off-line applications with single-stage converters // IEEE Transactions on Industrial Electronics, 1997, 44(5), pp. 638–647. Doi: 10.1109/41.633461
13. Do Prado, R.N., Bonaldo, S.A., Moreira, M.C. and Vidor, D.L. Electronic ballast with a high power factor for fluorescent lamps // In PESC Record, 1996, 27th Annual IEEE Power Electronics Specialists Conference, Vol. 2, pp. 1215–1220, IEEE. Doi: 10.1109/PESC.1996.548736

The temperature dependence of the radiation of freshwater ice at a frequency of 15 GHz has been experimentally investigated. The temperature range adjacent to the ice-water phase transition point has been studied. The measurements were carried out at an air temperature of 294 K. The ice temperature varied from 266 K to 273 K. Radiometer central frequency was 15 GHz. The derivative of the radio radiance or brightness temperature on the ice temperature varies from – 0.2 to – 0.7. The change of the derivative near the phase transition point was explained by the influence of liquid water in ice. A significant temperature difference between ambient air and ice leads to an increase in the mass of liquid water in ice. Liquid water is formed in micro cavities in the volume of ice. Water can also form on the air-ice boundary, while the temperature in the ice volume remains negative. The layer of liquid water at the ice-air interface, as well as its inclusions in ice cavities, make a significant contribution to the self-radiation of the thermodynamic system under study, since the signal frequency is close to the maximum frequency of the liquid water spectrum. The observed effect can be used for radiometric monitoring of the state of snow and ice formations and registration of the initial stages of ice melting

1. Debye, P. Polar Molecules / New York: The Chemical Catalogue Company, Inc., 1929, 172 p.
2. Cole, K.S., Cole, R.H. Dispersion and Absorption in Dielectrics I. Alternating Current Characteristics // Journal of Chemical Physics, 1941, # 9, pp. 341–351.
3. Devidson, D.W., Cole, R.H. Dielectric relaxation in glycerol, propylene glycol and n-propanol // Journal of Chemical Physics, 1951, # 19, pp. 1484–1490.
4. Havriliak, S., Negami, S. J. A complex plane analysis of α-dispersions in some polymer systems // Journal of Polymer Science, Part C: Polymer Letters, 1966, # 1(14), pp. 99–117.
5. Gaiduk, V.I. Molecular-model-based calculation of the complex permittivity of ice // Journal of Communications Technology and Electronics, 2008, # 53(6), pp. 676–688.
6. Kalmykov, Yu. P., Coffey, W. T., Crothers, D. S. F., Titov, S.V. Microscopic models for dielectric for dielectric relaxation in disordered systems // Physical Review E, 2004, # 70, 041103.
7. Byrne, D. J., Coffey, W. T., Kalmykov, Yu. P., Titov, S.V. Theory of anomalous dielectric relaxation // Journal of Physics: Conf. Series, 2019, # 1322, 012037.
8. Salzmann, C.G., Loveday, J.S., Rosu-Finsen, A., Bull, C.L. Structure and nature of ice XIX // Nature Communications, 2021, # 12, 3162.
9. Gasser, T.M., Thoeny, A.V., Plaga, L.J., Köster, K.W., Etter, M., Böhmer, R., Loerting, T. Experiments indicating a second hydrogen ordered phase of ice VI // Chemical Sciences, 2018, # 9, pp. 4224–4234.
10. Tao, Y.H., Dai, X., Moggach, S.A., Clode, P.L., Fitzgerald, A.J., Hodgetts, S.I., Harvey, A.R., Wallace, V.P. The spectrum of Ih ice using terahertz time-domain spectroscopy// Journal of Chemical Physics, 2024, # 160(21), 214503.
11. Risse1, N., Mario Mech, M., Prigent C., Spreen, G., Crewel, S. Assessing sea ice microwave emissivity up to submillimetre waves from airborne and satellite observations// The Cryosphere, 2024, # 18, pp. 4137–4163.
12. Li, Q., Yao, R., Tan, V.B.C., He, F., Zhao, H., Bai, T. A review of efficient thermal application for ice detection and anti de-icing technology// Applied Thermal Engineering, 2025, # 263, 125366.
13. Bordonskiy, G.S. Features of the electromagnetic properties of ice near the temperature of the waterice phase transition // Physics of the Solid State, 2005, # 47(4), pp. 691–695.
14. Bubukin, I.T., Stankevich K.S. Measurements of the reflectivity and permittivity of water in the film layer of the sea surface in the millimetre wave band // Journal of Communications Technology and Electronics, 2013, # 58, pp. 673–681.
15. Gavrilin, S.N. Dependence of water radiation on temperature at microwaves // Physica Scripta, 2025, # 100(1), p. 015966.
16. Gavrilin, S.N., Parfentyeva, N.A., Burmistrov E.R. Water surfaces microwave radiation at 15 GHz: application in remote sensing and radiometry // Light & Engineering, 2025, Vol. 33, # 5, pp. 119–125.
17. Hufford, G. A model for the complex permittivity of ice at frequencies below 1 THz // International Journal of Infrared and Millimetre Waves, 1991, # 12, pp. 677–682.

The article evaluates the effectiveness of tuneable spectral radiation modes depending on the stage of the vegetative period of cucumber plants of the variety "Svyatogor F1" under photo-culture conditions. Photobiological studies were conducted in an experimental hydroponic setup at a photosynthetic photon flux density (PPFD) of (200 ± 10) μmol/(s·m²). The concept and experimental design were developed jointly with specialists from the Agrarian Institute of the Ogarev Mordovia State University and JSC TEPLICHNOYE.
For the photobiological studies, experimental 150 W LED samples with an adjustable spectrum were manufactured at JSC Ardatov Lighting Plant using Osram's blue LEDs with a dominant wavelength λd = 450 nm, red LEDs – λd = 660 nm, farred LEDs – λd = 730 nm, and white LEDs with CCT equal to 5000 K and Ra = 70. The digital bidirectional DALI protocol provided smooth regulation of the radiation output of each of the four LED modules from 0 % to 100 % and the ability to receive feedback from the power source.
It was found that increasing the B radiation share to (50–55) % with a decrease in the R share by (20–25) % and the G share by (5–10) % during the vegetative growth stage of cucumber plants of the variety "Svyatogor F1" contributed to the formation of stronger seedlings with improved biometric parameters, which subsequently resulted in increased yield.
The feasibility of using the dynamic spectral composition of radiation as an effective method for controlling the growth and development of cucumber plants of the variety "Svyatogor F1" under photo-culture conditions was experimentally demonstrated.

1. Zakurin, A.O., Shchennikova, A. V., Kamionskaya, A.M. Artificial light culture in protected ground plant growing: Photosynthesis, photomorphogenesis, and prospects of LED application [Iskusstvennoye osveshcheniye pri vyrashchivanii rasteniy v zashchishchennykh gruntakh: fotosintez, fotomorfogenez i perspektivy primeneniya svetodiodov] // Russian J. Plant Physiolgy, 2020, Vol. 67, # 3, pp. 413–424.
2. Kuleshova, T.E., Udalova O.R., Balashova I.T., Anikina L.M., Kononchuk P. Yu., Mirskaya G.V., Dubovitskaya V.I., Vertebny V.E., Khomyakov Yu.V., Panova G.G. Features of the influence of the radiation spectrum on the productivity and biochemical composition of test fruit and leafy vegetable crops [Osobennosti vliyaniya spektra izlucheniya na produktivnost' i biokhimicheskiy sostav issleduyemykh plodovykh i listovykh ovoshchnykh kul'tur] // Journal of Technical Physics, 2022, Vol. 92, # 7, pp. 1060–1068.
3. Kim, H.H., Goins, G.D., Wheeler, R.M., Sager, J.C. Green-light Supplementation for Enhanced Lettuce Growth under Red and Blue Light Emitting Diodes// HortScience, 2004, Vol. 39, # 7, pp. 1617–1622.
4. Goggin, D.E., Steadman, K.J. Blue and green are frequently seen: responses of seeds to short- and midwavelength light // Seed Science Research, 2012, # 22, pp. 27–35.
5. Li, Y., Liu, Z., Shi, Q., Yang, F. and Wei M. Mixed red and blue light promotes tomato seedlings growth by influencing leaf anatomy, CO2, assimilation and endogenous hormones //Scientia Horticulture, 2021, 290 (1), p. 110500.
6. Vasilenko, V.F., Kuznetsov, E.D. Physiological and ecological aspects of the use of chemical and light regulation of plant growth // Bulletin of agricultural science, 1990, # 7, pp. 63–68.
7. Gomez, C., Mitchell, C.A. Growth responses of tomato seedlings to different spectra of supplemental lighting //HortScience, 2015, Vol. 50, p. 112.
8. Chia, P.L., Kubota, C. End-of-day far-red light quality and dose requirements for tomato rootstock hypocotyl elongation // HortScience, 2010, V. 45, p. 1501.
9. Yang, Z.C., Kubota, C., Chia, P.L., Kacira, M. Effect of end-of-day far-red light from a movable LED fixture on squash rootstock hypocotyl elongation // Sci. Hort. 2012, Vol. 136, p. 81.
10. Chinchilla, S., Izzo, L.G., van Santen, E., Gomez, C. Growth and physiological responses of lettuce grown under pre-dawn or end-of-day sole-source light-quality treatments // Horticulturae, 2018, Vol. 4, p. 8.
11. Goto, E. Effects of light quality on growth of crop plants under artificial lighting // Environ, Control Biol. 2003, Vol. 41, p. 121.
12. Tallman, G., Zeiger, E. Light quality and osmoregulation in Vicia guard cells: evidence for involvement of three metabolic pathways // Plant Physiology, 1988, Vol. 88, p. 887–895.
13. Makeev, N.A. Experimental assessment of the possibility of using a dynamic spectrum of radiation in growing the Yamal tomato variety // Young scientist, 2026, # 6, (609), pp. 65–69.
14. Rakutko, S.A., Rakutko, E.N., Vas'kin, A.N. Influence of the ratio of red and far-red radiation on the growth and development of tomato seedlings (Solanium Lycopersicum) // International journal of applied and fundamental research, 2016, # 8, pp. 136–140.
15. Tikhomirov, A.A., Molokeev, M.S., Velichko, V.V. Photobiological efficiency of radiation in the PAR region for radish cenosis using an irradiator with LEDs with an adjustable spectrum // Svetotekhnika, 2023, # 6, pp. 40–45.
16. Tikhomirov, A.A., Molokeev, M.S., Velichko, V.V. Photo-biological Effectiveness of PAR for Radish Plant Communities Irradiated Using an LED Source with an Adjustable Spectrum // Light & Engineering, 2024, Vol. 32, # 2, pp. 70–77.
17. Kurshev, A.E., Bogatryrev S.D., Zheleznikova O.E., Lyulev A.O. Determination of the optimal ratio of the levels of red and far-red radiation when growing cucumber plants using photoculture technology // Light & Engineering. – 2025. – No. 1. – P. 43–47.
18. Kurshev, A.E., Bogatyrev, S.D., Zheleznikova, O.E., Lyulyov, A.O. Optimal Ratio of Red and Far-red Irradiations for Cucumber Plants Growing by Light-culture Technology // Light & Engineering, 2025, Vol. 33, # 2, pp. 90–95.
19. Skobeltsina, A.V. Biological features of woody plants adaptation in conditions of urbanized territories [Biologicheskiye osobennosti adaptatsii drevesnykh rasteniy k usloviyam urbanizirovannykh territoriy] // Dissertation on competition of a scientific degree Ph. D. in biological science, Chita, 2011, 130 p.
20. Ivanov, L.A., Ivanova, L.A., Ronzhina, D.A. Regularities of changes in the specific density of leaves in plants of Eurasia along the gradient of aridity // Reports of the Academy of Sciences, 2009, Vol. 428, # 1, pp. 135–138.
21. Prikupets, L.B., Boos, G.V., Terekhov, V.G., Tarakanov, I.G. Research into Influence from Different Ranges of PAR Radiation on Efficiency and Biochemical Composition of Green Salad Foliage Biomass // Light & Engineering, 2018, Vol. 26, # 4, pp. 38–47.

1. Berger, J. The Art of Seeing / Translated from English by E. Schragi, St. Petersburg: Cloudberry, 2012, 184 p.
2. Lepecki, A. Exhausting Dance. Performance and the Politics of Movement / Andre Lepecki, Moscow: OOO "Art Guide", 2021, 208 p.
3. Itten, J. The Art of Colour / Translated from German; 2nd edition; Preface by L. Monakhova, Moscow: Publisher D. Aronov, 2001, 96 p.
4. Matyushin, M.V. Colour Handbook. The Pattern of Variability of Colour Combinations / Moscow: Publisher D. Aronov, 2007, 72 p.
5. Arvatov, B. Art and Production. A Collection of Articles / Moscow: V-A-C Press, 2018, 184 p.
6. Graeber, D. Bullshit Jobs: A Treatise on the Spread of Meaningless Labour / David Graeber. Moscow: Ad Marginem Press, 2020, 440 p.
7. Hal Foster, Rosalind Krauss, Yve-Alain Bois, Benjamin H.D. Buchloh, and David Joselit. Art Since 1900 Modernism, Antimodernism, Postmodernism / Moscow: Ad Marginem Press, 2015, 816 p.
8. Bereznitskaya N. Making Light Itself Visible / (October 26, 2011) https://di.mmoma.ru/news?mid=2631&id=1083
9. Ferschild, M.D. Models of Colour Perception. 2nd edition // Rochester Institute of Technology, Munsell Colour Science Laboratory, 2006, 439 p.
10. Varfolomeev, L.P. Elementary Lighting Engineering / Edited by Professor J,.B. Aisenberg / Moscow: "Znak", 2008, 220 p.
11. Bishop, C. Radical Museology, or Are Museums of Contemporary Art Really That "Modern"? / Claire Bishop; with illustrations by Dana Perzhovsky, Moscow: OOO "Ad Marginem Press", 2014, 96 p.
12. Groys, B. On the New. Experience in the Economics of Culture / Moscow: Ad Marginem Press, 2015, 240 p.

An analysis of the applicability of the ABC recombination model to describing the current dependence of the internal quantum efficiency (IQE) demonstrates its inadequacy. The main criticisms are as follows:
– The use of a secondary parameter for quantum-well device structures, namely the excess carrier concentration, as the argument in the current dependence of IQE, especially under the assumption of equal electron and hole concentrations in the space-charge region;
– Auger recombination and radiative recombination are partial components of a unified inter-band recombination process and therefore cannot be treated as independent processes; – The ABC model unjustifiably ignores the fundamental mechanism of tunneling current formation; – In the ABC model, the origin of the nonradiative current is attributed to the Shockley – Read – Hall recombination mechanism, whereas in the device structure it is governed by the Sah – Noyce – Shockley mechanism.
Based on this critical analysis, it is concluded that an adequate model describing the IQE – current dependence should be developed on the basis of the physical mechanisms governing the fundamental currents in quantum-well device structures:
– The recombination current via defect levels in quantum wells, Jt;
– The inter-band recombination current, JB;
– The tunnelling current, JT.
Such a model should also account for the unified mechanism responsible for the formation of the radiative component of inter-band recombination, (1‑p)・JB, and the nonradiative component, p・Jb, where p is the partition coefficient dependent on JB. A general expression for the current dependence of IQE is proposed as follows:
ηIQE=(1‑p)・ JB /(Jt+JB+JT).

1. Armitage, R., Feezel, D., Kioupakis, E., Rajan, S., Li, X., Rahman, S.I., Pant, N. Impact of Quantum Well Thickness on Efficiency Loss in InGaN/GaN LEDs: Challenges for Thin-Well Designs // 2025. DOI: https://doi.org/10.60893/figshare.apl.c7727126
2. Marcel Schilling, Jan Ruschel, Hyun Kyong Cho, Jens Rass, Jakob Höpfner, Tim Wernicke, Sven Einfeldt and Kneiss, M. Effect of quantum well number on the efficiency and degradation of AlGaN-based far-UVC LEDs emitting at 233 nm and 226 nm // Semicond. Sci. Technol., 2025, 40, 045004 (8pp). DOI: https://doi.org/10.1088/1361-6641/adbf40
3. Hongping Zhao, Guangyu Liu, Jing Zhang, Jonathan D. Poplawsky, Volkmar Dierolf, and Nelson, T. Approaches for high internal quantum efficiency green In-GaN light-emitting diodes with large overlap quantum wells // OSA. July 2011. Vol. 19, No. S4 / OPTICS EXPRESS A994.
4. Tak, T., Chow, Y.C., Nakamura, S., DenBaars, S.P., Weisbuch, C., and Speck, J.S. Unexpected origin of the quantum efficiency reduction in long-wavelength (In, Ga)N light-emitting diodes // Phys. Rev. Appl.2025. 23. 034002. DOI: https:// doi.org/10.1103
5. Jong-In Shim and Dong-Soo Shin. Measuring the internal quantum efficiency of light-emitting diodes: towards accurate and reliable room-temperature characterization // Nanophotonics, 2018, 7(10), pp. 1601–1615. DOI: https://doi.org/10.1515/nanoph-2018-0094
6. Shin D-S, Han D-P, Oh J-I, Shim J-I. Study of droop phenomena in InGaN-based blue and green light-emitting diodes by temperature-dependent electroluminescence // Appl. Phys. Lett. 2012; 100:153506.
7. Lin GB, Shan Q, Wang Y, et al. "U-turn" feature in the efficiency versus current curve of GaInN/GaN light-emitting diodes // Appl. Phys. Lett. 2014, 105:221116.
8. Han D-P, Zheng D-G, Oh C-H, et al. Nonradiative recombination mechanisms in InGaN/GaN based light-emitting diodes investigated by temperature-dependent measurements // Appl. Phys. Lett. 2014, 104:151108.
9. Wang, Y., Pan, M., Li, T. Comprehensive study of internal quantum efficiency of high-brightness GaN-based light-emitting diodes by temperature-dependent electroluminescence method // Proc. SPIE 2014; 9003:90030D.
10. Titkov, I.E., Karpov, Y.S., Yadav, A., et al. Temperature-dependent internal quantum efficiency of blue high-brightness light-emitting diodes // IEEE J Quantum Electron, 2014; 50:911.
11. Dai, Q, Shan, Q, Wang, J, et al. Carrier recombination mechanisms and efficiency droop in GaInN/GaN light-emitting diodes // Appl. Phys. Lett. 2010, 97:133507.
12. Karpov, S. ABC-model for interpretation of internal quantum efficiency and its droop in III-nitride LEDs: a review // Opt. Quant. Electronics, 2015, 104:091110.
13. Aurelien David et al. Review -The Physics of Recombinations in III-Nitride Emitters // ECS Journal of Solid State Science and Technology, 2020, Vol. 9, 016021.
14. Shukun Li, Guo Yu, Rui Lang, Menglai Lei, Huanqing Chen, Muhammad Sadidiqui, Akbar Khan, Linghai Meng, Hua Zong, Shengxiang Jiang, Peijun Wen, Wei Yang, Xiaddong Hu. Analytical models of electron leakage currents in gallium nitride-based laser diodes and light-emitting diodes // Optics Express. 2022. Vol. 30, No. 3, 3974
15. Voitsekhovsky, A.V., Gorn, D.I. Recombination mechanisms in InGaN/GaN structures with quantum wells at high excitation levels // Izv. Vysdsch. Uch. Zav.: Fizika, 2015, Vol. 58, # 82, pp. 171–173.
16. Shanshan Wang, Menglin Huang, Su-Huai Wei, Xin-Gao Gong, and Shiyou Chen. Generalized A(n) BC Recombination Model in Semiconductors with Multilevel Defects // Journal Am. Chem. Soc. 2025 Oct 8, 147 (40), pp. 36825–36836. DOI: https://doi: 10.1021/jacs.5c13336
17. Hopkins, M.A., Allsopp, D.W.E., Kappers, M.J., Oliver, R.A., and Humphreys, C.J. The ABC model of recombination reinterpreted: Impact on understanding carrier transport and efficiency droop in InGaN/GaN light emitting diodes // JOURNAL OF APPLIED PHYSICS, 2017, # 122, 234505.
18. Ivan B. Karomi1, Ammar T. Zakar, and Al-Ghamdi Mohammed S. ABC recombination model for quantum dot laser // IOP Conf. Series: Materials Science and Engineering, 2021, 126. DOI: https://doi:10.1088/1757-899X/1126/1/012004
19. Zang, M., Bhattacharya, P., Singh, J., Hinckley, J. Direct measurement auge recombination in In0.1Ga0.9N/GaN quantum wells and its impact on the efficiency of In0.1Ga0.9N/GaN multi-play quantum well light emitting diodes // Appl. Phys. Lett., 2009, # 95, 201108.
20. Wang, J., Wang, L., et al. An improved carrier rate model to evaluate internal quantum efficiency and analyse efficiency droop origin of InGaN based light-emitting diodes // J. Appl. Phys., 2012, 112: 023107.
21. Bochkareva, N.I., Zhirnov, E.A., Efremov, A.A., Rebane, Yu.T., Gorbunov, R.I., and Shreter Yu.G. Tunnel-Recombination Currents and Electroluminescence Efficiency in InGaN/GaN LEDs // SEMICONDUCTORS, 2005, Vol. 39, # 5, pp. 894–899.
22. Bulyarsky, S.V., Vostretsova, L.N., Ribenek, V.A. Tunnelling recombination in GaN/InGaN LEDs with a single quantum well // Nanosystems: Phys. Chem. Math., 2024, 15 (2), pp. 204–214. DOI: 10.17586/2220-8054-2024-15-2-204-214
23. Shockley, W. The Theory of p-n Junctions in Semiconductor and p-n Junction Transistors // Belt Syst. Tech. J., 1949, Vol. 28, pp. 435–489.
24. Sah, C.T., Noyse, R.N., Shokley, W. Carrier Generation and Recombination in p-n Junction Caracteristics // Proc. IRE, 1957, Vol. 45, pp. 1228–1243.
25. Schubert, F.E. Light-Emitting Diodes // Translated from English and edited by A.E. Yunovich, Moscow, 2nd ed., FIZMATLIT, 2006, 496 p.
26. Manyakhin, F.I., Varlamov, D.O., Krylov, V.P., Morketsova, L.O., Skvortsov A.A., and Nikolaev, V.K. Physic-mathematical model of the voltage – current characteristics of light-emitting diodes with quantum wells based on the Sah – Noyce – Shockley recombination mechanism // Journal of Semiconductors, 2024, 45. DOI: 10.1088/1674-4926/23120044
27. Manyakhin, F.I., Varlamov, D.O., Krylov, V.P., Morketsova, L.O., Skvortsov A.A., and Nikolaev, V.K. Mechanism of current-voltage dependence of quantum well light-emitting diodes // Journal of Material Research, 2025. DOI: 10.1557/s43578-025-01639-y
28. Dubovik, V.I., Ushakov, D.V. Calculation of Auger recombination coefficients in a quantum-sized Inx-Ga1‑xAsyP1‑y/InP heterostructure // https://elib.bsu.by/handle/123456789/286403 (date of access is 21.09.2025).
29. Felix Nippert, Sergey Yu. Karpov, Gordon Callsen Bastian Galler, Thomas Kure, Christian Nenstiel, Martin Straßburg, Hans-Jürgen Lugauer, and Hoffmann, A. Temperature-dependent recombination coefficients in InGaN light-emitting diodes. Hole localization, Auger processes and the green gap // Appl. Phys. Lett., 2016, Vol. 109, 161103. DOI: https://doi.org//10.1063/1.4965298
30. Manyakhin, F.I. et al. Influence of the nature of the distribution of recombination centres in the space charge region of the p – n junction on the parameters of the current – voltage characteristics within the classical Shockley and Shockley – Noyce – Sah models // Semiconductor Science and Technology, 2025, Vol. 40, # 1, 015017. DOI: https://doi.org/10.1088/1361-6641/ad929e
31. Manyakhin, F.I. et al. Electrophysical Reasons for Limiting the Operating Modes of Quantum Well Light Emitting Diodes // Light & Engineering J., Vol. 33, # 4, 2025, pp. 103–112.

The relevance of the topic of the article is caused by the concern of the authors and a number of specialists in recent years about the tendency to impoverish the architectural appearance of mass housing, including through the elimination of summer premises. The work considers how economic restrictions affect spatial solutions and lead to a simplification of the architectural forms of buildings, up to the formation of simple parallelepiped volumes.
The construction of housing without balconies and loggias was preceded by a phased decrease in the rates of insolation of apartments in residential buildings. Insolation well-being is determined in our country by the Federal Law and sanitary-hygienic requirements [1, 2]. Foreign studies are based on the European EN12665 standard [3–7].
The domestic system of reducing insolation hours quickly led to the revival of the economy and maximum benefit to builders, investors and developers due to the proliferation of densely populated housing 'parallelepipeds' without summer premises, and of all comfort classes [8]. In this regard, the purpose of this study is an economic analysis of the geometry of architectural solutions of houses with and without summer rooms, which directly affect the simplification of the volumetric-spatial appearance of a high-density dwelling. To achieve the goal, graph-analytical tasks were set to identify the minimum distances between the facades of buildings of different heights and having the same geometric characteristics, but differing in the absence or presence of loggias and balconies. When performing calculations of interfacial distances, methods for determining the duration of insolation, provided for by the regulatory framework, were used. The subject of the study was the effect of additional horizontal dimming on the required inter-facade distances.

1. Federal Law No. 52-FZ of March 30, 1999: On Sanitary and Epidemiological Welfare. National Association of Scientists (NAU) # VI (11), 2015 / MEDICAL SCIENCES 29 population // http://www.consultant.ru/document/ cons_doc_LAW_172734/.
2. Sanitary rules and norms of SanPiN 2.2.1/2.1.1. 1076‑01: Hygienic requirements for insolation and sun protection of premises of residential and public buildings and territories // Moscow: Ministry of Health of Russia, 2002.
3. Sinoo, M.M. Light Conditions in Nursing Homes: Visual Comfort and Visual Functioning of Residents // Eindhoven: University of Technology, 2016.
4. Darula, S., Christoffersen, J., Malikova, M. Sunlight and insolation of building interiors // Energy Procedia, 2015, Vol. 78, pp. 1245–1250.
5. Christa van Santen. Light Zone City. Light planning in the Urban Context / Brikhäuser – Publishers for Architecture, 2006, 127 p.
6. Brandi Ulrike, Geissmar-Brandi Ch. Light for Cities. Lighting Design for Urban Spaces. A Handbook / Brikhäuser – Publishers for Architecture, 2007, 168 p.
7. Turner, P.L, van Someren, E.J.W, Mainster, M.A. The role of environmental light in sleep and health: Effects of ocular aging and cataract surgery // Sleep Medicine Reviews, 2010, 14 (4), pp. 269–280.
8. Pushilina, Yu.N., Chebotarev, P.N. Insolation standards and its impact on the appearance of residential buildings [Standarty teploizolyatsii i ikh vliyaniye na vneshniy vid zhilykh zdaniy] // International Scientific Journal Symbol of Science, 2015, # 6, ISSN 2410-700Х, pp. 355–356.
9. Vasilieva, A.V. Directives and creativity: images and architecture of facades of Soviet residential buildings in the 1930s [Direktivy i tvorchestvo: obrazy i arkhitektura fasadov sovetskikh zhilykh domov 1930‑kh godov] // Theory and History of Architecture, 2022, # 1 (5), pp. 55–64. DOI: 10.22227/2712-8237.2022.1.55-64
10. Popovsky, Yu.B. History of sanitary and epidemiological rationing of insolation of residential premises in the USSR and the Russian Federation [Istoriya sanitarno-epidemiologicheskogo normirovaniya solnechnoy radiatsii zhilykh pomeshcheniy v SSSR i Rossiyskoy Federatsii] // National Association of Scientists, 2015, # 6–3 (11), pp. 27–30.
11. Shmarov, I., Zemtsov, V., Korkina, E. Insolation – the practice of rationing and calculation [Insolyatsiya – praktika normirovaniya i rascheta] // Housing construction, 2016, # 2.
12. Karpenko, V.Е. Artificial light panorama as expression planning structure of the city [Panorama iskusstvennogo osveshcheniya kak vyrazitel'naya struktura gorodskogo planirovaniya] // Architecture and Modern Information Technologies, 2012, # 1 (18), p.9.
13. Pronina, T.V. Formation of the appearance of multi-story residential complexes in largest cities // IOP Conference Series: Materials Science and Engineering. International Science and Technology Conference 'FarEastCon 2019', 2020, p. 032001.
14. Solodilova, L.A. Impact of insolation requirements on the quality of the architectural environment // Light & Engineering, 2025, Vol. 33, # 4, pp. 66–72.
15. Solodilova, L.A. Impact of mass housing forms of ownership on the architectural appearance of the buildings // Science Prospects. TGASU, Tambov, 2021, # 1(136), pp. 38–40.

1. Bogdanova, S.V., Ermakova, A.N., Zubenko, E.E. 3-D visualization and control system for LED lighting of vertical farms [Sistema 3D-vizualizatsii i upravleniya svetodiodnym osveshcheniyem vertikal'nykh ferm] // Certificate of state registration of the computer program, 2122745, 1998, Bulletin No. 33.
2. Sedyshev, V.V. Automated energy-saving greenhouse // Bulletin of the Orenburg State Agrarian University, 2025, Vol. 113, # 3, pp. 105–112. https://doi.org/10.37670/2073‑0853‑2025‑113‑3‑105‑112
3. Modern greenhouse farming / Digest. Russian State Agrarian University – Moscow Timiryazev Agricultural Academy, 2025, Issue 6 (68), 18 p.
4. Terekhov, V.G. Irradiation system for an automated multi-tiered phyto-installation of the CITY FARM type // Light & Engineering, 2019, Vol. 27, # 6, pp. 106–111.
5. Shirobokova, T.A. Improving the LED Lighting System for Livestock Buildings / FSBEI HE Udmurt State Agrarian University, Dissertation… Doctor of Technical Sciences, 2025.

The paper aims to measure experimentally the transmittance coefficients (TC) of different materials in the sub-terahertz range at a frequency of 97.8 GHz to justify choice of materials when designing sub-terahertz range systems. Despite the publications existed on this topic the experimental data obtained in the work are important, since the composition of materials, as well as the weave structure of fabric composition, change over time which leads to values of the TC differing from those measured 20 years ago. The measurements were carried out at a frequency of 97.8 GHz using a pass-through scheme with a Tera‑1024 matrix camera and an IMPATT-diode generator. For polymer, structural and radio-absorbing materials the influence of the layers number (1–3) on the measurement results was investigated, while for 19 textile materials the difference between air-dry and moisture conditions was studied. Teflon and foam plastic are shown to have a TC of T≈1.0, while the radio-absorbing material provides attenuation of >21 dB. Air-dry fabrics generally transmit radiation almost completely (T = 0.87–0.99), and moistening reduces the TC by (2–70) times. The expanded relative uncertainty for measurements was (1.22–12.15) % with a coverage factor of k = 2 (95 % confidence level). The results of the completed work allow predicting quantitatively the losses of sub-terahertz radiation in real materials and justify their selection in sub-terahertz range systems. The limitations of the work are a fixed frequency and a qualitative assessment of moistening. Further studies are planne

1. Chan, W.L., Deibel, J., Mittleman, D.M. Imaging with terahertz radiation // Reports on Progress in Physics, 2007, Vol. 70, # 8, pp. 1325–1379. DOI: 10.1088/0034-4885/70/8/R02
2. Hu, B.B., Nuss, M.C. Imaging with terahertz waves // Optics Letters, 1995, Vol. 20, # 16, pp. 1716–1718. DOI: 10.1364/OL.20.001716
3. Nikolaev, N.V., Ilyin, V.V., Sokolov, A.M., Matskevich, E.E. Application of terahertz (sub-terahertz) inspection systems in integrated security systems // Security Issues, 2021, # 4, pp. 39–49. DOI: 10.25136/2409-7543.2021.4.36822
4. Li, X., Li, J., Li, Y., Ozcan, A., Jarrahi, M. Highthroughput terahertz imaging: progress and challenges // Light: Science & Applications, 2023, Vol. 12, # 1, pp. 233. DOI: 10.1038/s41377-023-01278-0
5. Sulimsky, E.S., Stroev, N.N., Astakhov, S.P., Vlasenkova, A.A., Timofeeva, N.S. Device for changing the energy distribution in the aperture plane of a conical emitter for a millimetre range radio imaging system // Russian Federation Patent No. 2728249 C1. Published July 28, 2020.
6. Astakhov, S.P., Stroev, N.N., Yakimenko, I.A., Sulimsky, E.S. The results of the experimental study of the method of directional radiation pattern transformation of a conical horn radiator operating in millimetric (sub-THz) band // Light & Engineering, 2021, Vol. 29, # 6, pp. 157–161. DOI: 10.33383/2021-058
7. TeraSense. Terahertz imaging cameras // URL: https://terasense.com/products/sub-thz-imaging-cameras/ (accessed: 20.03.2026).
8. TeraSense. Terahertz sources // URL: https://terasense.com/products/terahertz-sources/ (accessed: 20.03.2026).
9. Shin, S.H., Lucyszyn, S. Benchmarking a commercial (sub-)THz focal plane array against a custom-built millimetre-wave single-pixel camera // IEEE Access, 2020, Vol. 8, pp. 191174–191190. DOI: 10.1109/ACCESS.2020.3030617
10. Mittleman, D.M., Jacobsen, R.H., Nuss, M.C. T-ray imaging // IEEE Journal of Selected Topics in Quantum Electronics, 1996, Vol. 2, # 3, pp. 679–692. DOI: 10.1109/2944.571768.
11. Withayachumnankul, W., Fischer, B.M., Lin, H., Abbott, D. Uncertainty in terahertz time-domain spectroscopy measurement // Journal of the Optical Society of America, B, 2008, Vol. 25, # 6, pp. 1059–1072. DOI: 10.1364/JOSAB.25.001059
12. Withayachumnankul, W., Naftaly, M. Fundamentals of measurement in terahertz time-domain spectroscopy // Journal of Infrared, Millimetre, and Terahertz Waves, 2014, Vol. 35, # 8, pp. 610–637. DOI: 10.1007/s10762-013-0042-z
13. Chang, T., Zhang, X., Zhang, X., Cui, H.L. Accurate determination of dielectric permittivity of polymers from 75 GHz to 1.6 THz using both S-parameters and transmission spectroscopy // Applied Optics, 2017, Vol. 56, # 12, pp. 3287–3292. DOI: 10.1364/AO.56.003287
14. Piesiewicz, R., Jansen, C., Wietzke, S., Mittleman, D., Koch, M., Kürner, T. Properties of building and plastic materials in the THz range // International Journal of Infrared and Millimetre Waves, 2007, Vol. 28, # 5, pp. 363–371. DOI: 10.1007/s10762-007-9217-9
15. Zhao, G., ter Mors, M., Wenckebach, W.T., Planken, P.C.M. Terahertz dielectric properties of polystyrene foam // Journal of the Optical Society of America, B, 2002, Vol. 19, # 6, pp. 1476–1479. DOI: 10.1364/JOSAB.19.001476
16. Bjarnason, J.E., Chan, T.L.J., Lee, A.W.M., Celis, M.A., Brown E.R. Millimetre-wave, terahertz, and midinfrared transmission through common clothing // Applied Physics Letters, 2004, Vol. 85, # 4, pp. 519–521. DOI: 10.1063/1.1771814
17. Dunayevskiy, I., Bortnik, B., Geary, K., Lombardo, R., Jack, M., Fetterman, H. Millimet0er- and submillimetre-wave characterization of various fabrics // Applied Optics, 2007, Vol. 46, # 24, pp. 6161–6165. DOI: 10.1364/AO.46.006161
18. Ellison, W.J. Permittivity of pure water, at standard atmospheric pressure, over the frequency range 0–25 THz and the temperature range 0–100 °C // Journal of Physical and Chemical Reference Data, 2007, Vol. 36, # 1, pp. 1–18. DOI: 10.1063/1.2360986

This study proposes a novel design method for compact, high-flexibility freeform lenses to generate high-quality rectangular light spots for electrical skylight systems. By employing rectangular grid partitioning, the design overcomes typical issues in conventional systems such as structural complexity and non-uniform illuminance. The resulting lens offers improved illuminance uniformity and sharp edge definition without increasing the system's physical size. To optimize performance, three key innovations are introduced: (i) a down-sampling modelling technique that enhances simulation precision while reducing computation time; (ii) an energy surface clipping method that removes rays undergoing total internal reflection, improving light distribution; and (iii) a UV surface construction approach that merges discrete points into a smooth freeform surface, effectively minimizing edge distortion. The proposed design was validated through optical simulations and experimental implementation using LUXEON C white LEDs. Results demonstrate its effectiveness in forming well-defined, uniform rectangular light spots. Additionally, the design's scalability was tested under extended light source conditions and for larger target areas. Genetic algorithms were employed to optimize LED array configurations, further enhancing optical performance. This work provides a scalable and efficient optical solution for electrical skylight applications, offering high-quality lighting effects suitable for integration into architectural and enclosed environments.

1. Yasukouchi Akira, Maeda Takafumi, Hara Kazuyoshi, et al. None-visual effects of diurnal exposure to an artificial skylight, including nocturnal melatonin suppression // Journal of physiological anthropology, 2019, Vol. 38, # 1. https://doi.org/10.1186/s40101‑019‑0203‑4
2. Markus Canazei, Wilfried Pohl, Harald R. Bliem, et al. Artificial skylight effects in a windowless office environment // Building and Environment, 2017, Vol. 124, # 11, pp. 69–77.
3. Canazei, M., Laner, M., Staggl, S., et al. Room – and illumination-related effects of an artificial skylight // Lighting Research & Technology, 2016, Vol. 48, # 5, pp. 539–558. https://doi.org/10.1177/14771 53515577852
4. CoeLux Srl. Experience the sky from the first fully open MRI system, retrieved April 28, 2024 from https://www.coelux.com/en/news/experience-the-sky-fromthe-first-fully-open-mri-system‑11556.
5. Qingdao Yeelink Information Technology Co., Ltd. Smart Lighting Made Easier Yeelight, retrieved April 28, 2024, from https://www.yeelight.com/home.
6. Fournier, F., Rolland, J. Design methodology for high brightness projectors // Journal of Display Technology, Vol. 4, # 1, pp. 86–91.
7. Minano, J.C., Benitez, P., Blen, J., et al. High-efficiency freeform condenser overcoming rotational symmetry limitations // Optics express, 2008, Vol. 16, # 25, pp. 20193–20195.
8. Sun, L.W., Jin, S.Z., et al. Design of free-form micro-lens for LED general illumination // 2009 Asia Communications and Photonics conference and Exhibition (ACP), Shanghai, China, pp. 1–10.
9. Liu, Z., Liu, S., Wang, K., et al. Optical Analysis of Colour Distribution in White LEDs With Various Packaging Methods // IEEE Photonics Technology Letters, 2008, Vol. 20, # 24, pp. 2027–2029.
10. Shuang, Z., Kai, W., Fei, C., et al., Lens design of LED searchlight of high brightness and distant spot // Journal of the Optical Society of America, A, Optics, image science, and vision, 2011, Vol. 28, # 5, pp. 815–820.
11. Zongyuan, L., Kai, W., Xiaobing, L., et al. Precise optical modelling of blue light emitting diodes by Monte Carlo ray-tracing // Optics express, 2010, Vol. 18, # 9, pp. 9398–9412.
12. Sun, L., Jin. S., Cen, S. Freeform micro-lens for illumination applications // Applied optics, 2009, Vol. 48, # 29, pp. 5520–5521.
13. Jin-Jia Chen, Te-Yuan Wang, Kuang-Lung Huang, et al. Freeform lens design for LED collimating illumination // Optics express, Vol. 20, # 10, pp. 10984–10955.
14. Feng, Z., Cheng, D., Wang, Y. Iterative freeform lens design for optical field control // Photonics Research, 2021, Vol. 9, # 9, pp. 1775–1783.
15. Ge Aimiing, Wang Wei, Du Zhengqing, et al. High-energy-efficiency optical system for an LED headlamp architecture // Applied Optics, 2013, Vol. 52, # 34, pp. 8320–8321.
16. Wang, K., Wu, D., Chen, F., et al. Angular colour uniformity enhancement of white light emitting diodes integrated with freeform lenses // Optics letters, 2010, Vol. 35, # 11, pp. 1860–1861.
17. Xianglong Mao, Hongtao Li, Yanjun Han, et al. Two-step design method for highly compact three-dimensional freeform optical system for LED surface light source // Opt. Express, 2014, Vol. 22, # S6, pp. A1491-A1506.
18. Ries, H., Muschaweck, J. Tailored freeform optical surfaces // Journal of the Optical Society of America, A, 2002, Vol. 19, # 3, pp. 590–595.
19. Jetter, R., Ries, H. Optimized tailoring for lens design // Proc. of SPIE, 2005, Vol. 5875, # 1, pp. 58750A (1–8).
20. Ries, H., Muschaweck, J. Tailoring freeform lenses for illumination // Proc. of SPIE, 2001, Vol. 4442, pp. 43–50.
21. Liu, P., Wang, H., Wu, R., et al. Uniform illumination design by configuration of LEDs and optimization of LED lens for large-scale colour-mixing applications // Applied Optics, 2013, Vol. 52, # 17, pp. 3998–4005.
22. Sun, L.W., Jin, S.Z. Proceedings of the 9th international PCIM China conference: design and implementation of a high efficiency power structure for LED street lights // Optics Express, 2010, Vol. 20, # 10, pp. 39–40.
23. Duerr Fabian, Benitez Pablo, Minano Juan C. Analytic freeform lens design in 3D: coupling three ray sets using two lens surfaces // Optics Express, 2012, Vol. 20, # 10, pp. 10839–10840.
24. Shang Wang, Kai Wang, Fei Chen, et al. Design of primary optics for LED chip array in road lighting application // Opt. Express, 2011, Vol. 19, # S4, A716-A724.
25. Matt, B. Design of free forms to uniformly illuminate polygonal targets from extended sources via edge ray mapping // Applied optics, 2020, Vol. 59, # 22, pp. 6490–6496.
26. Heemels, A., Koning, D.B, Möller, M., et al. Optimizing freeform lenses for extended sources with algorithmic differentiable ray tracing and truncated hierarchical B-splines // Optics express,2024, Vol. 32, # 6, pp. 9730–9746.
27. Kai Wang, Sheng Liu, Xiaobing Luo, and Dan Wu. Freeform Optics for LED Packages and Applications / © 2017 Chemical Industry Press., Published 2017 by John Wiley & Sons, Singapore Pte. Ltd.

The prospects for a rapid, non-contact quality-control method for salmon fillets based on visible-hyperspectral imaging are analysed. It is shown that the traditional method of quality assessment using the reference SalmoFan colour scale, applied to rainbow trout and Atlantic salmon fillets, is prone to the inherent risks of visual inspection, specifically subjectivity and metamerism, and introduces significant error when analysing other salmonid species, particularly sockeye salmon. The proposed method involves capturing spectral images of the fillet surface, converting the reflectance spectra to CIE 1964 chromaticity coordinates, and classifying them. This process enables the construction of maps showing the spatial distribution of colour characteristics that reflect carotenoid content. It has been established that the hyperspectral approach can provide an objective, reproducible, non-contact, and high-throughput assessment of product quality. The proposed method enables the development of a quality assessment and control system for salmonid fillets of distinct species on a unified methodological and instrumental basis, and, in the future, allows for the identification of the contribution of numerous factors to the current state of the product.

1. Buttle, L. G., et al. The effect of feed pigment type on flesh pigment deposition and colour in farmed Atlantic salmon, Salmo salar L // Aquaculture Research, 2001. Vol. 32, # 2, pp. 103–111.
2. Kondratiuk, V., et. al. Effect of feeding conditions on the quality traits of rainbow trout //Acta fytotechn zootechny, 2021, Vol. 24, # 3, pp. 256–264.
3. Ljungqvist, M. G., Dissing, B. S., Nielsen, M. E., Ersbøll, B. K., Clemmensen, L. K. H., & Frosch, S. (2012). Classification of Astaxanthin Colouration of Salmonid Fish using Spectral Imaging and Tricolour Measurement // Technical University of Denmark, 2012, D T U Compute. Technical Report No. 2012–08, Multivariate image analysis for quality inspection in fish feed production.
4. Nofima study reveals impact of mechanical delousing on salmon fillet pigmentation // Aquaculture North America. URL: https://www.aquaculturenorthamerica.com/nofima-study-reveals-impact-of-mechanical-delousing-on-salmon-fillet-pigmentation/] (date of access: 01.04.2025).
5. Yeşilayer, N. Comparison of Flesh Colour Assessment Methods for Wild Brown Trout (Salmo trutta macrostigma), Farmed Rainbow Trout (Oncorhynchus mykiss), and Farmed Atlantic Salmon (Salmo salar) // Pakistan Journal of Zoology, 2020, Vol. 52, # 3.
6. Khoshnoudi-Nia, S., Moosavi-Nasab, M. Prediction of various freshness indicators in fish fillets by one multispectral imaging system // Sci Rep 9, 14704, 2019. https://doi.org/10.1038/s41598‑019‑51264‑z
7. Sáez, M. I. et al. Assessing the potential of algae extracts for extending the shelf life of rainbow trout (Oncorhynchus mykiss) fillets // Foods, 2021, Vol. 10, # 5, p. 910.
8. Teimouri M., et. al. The effects of dietary supplement of Spirulina platensis on blood carotenoid concentration and fillet colour stability in rainbow trout (Oncorhynchus mykiss) //Aquaculture, 2013, Vol. 414, pp. 224–228.
9. Pu, R. Hyperspectral remote sensing: fundamentals and practices // CRC Press, 2017, 380 p. https://doi.org/10.1201/9781315120607
10. Tejada-Casado, M. et al. Reflectance and colour prediction of dental material monolithic samples with varying thickness // Dental Materials, 2022, Vol. 38, # 4, pp. 622–631.
11. Cherubini, F. et al. Application of a hyperspectral camera for colorimetric measurements on polychrome surfaces in a controlled environment and evaluation of three image processing software for displaying colorimetric data: Pros and cons of the methodology presented // Colour Research & Application, 2023, Vol. 48, # 2, pp. 210–221.
12. Khokhlov, D.D., Pozhar V.E. Spectral endoscopy: technical means and methods //Light & Engineering, 2022, Vol. 30, # 6, pp. 7–14.
13. Zolotukhina, A.; et. al. Evaluation of Leaf Chlorophyll Content from Acousto-Optic Hyper-spectral Data: A Multi-Crop Study // Remote Sensing 2024, Vol. 16, p. 1073. doi:10.3390/RS16061073
14. Touil, M. et al. Acousto-optically driven lens-less single-shot ultrafast optical imaging // Light: Science & Applications, 2022, Vol. 11, # 1, p. 66.
15. Machikhin, A. S. et al. Minimizing aberrations of a near-infrared acousto-optic video spectrometer by optimizing the tuneable filter parameters // Journal of Optical Technology, 2019, Vol. 86, # 12, pp. 794–798.
16. Gurevich, M.M. Colour and Its Measurement. Leningrad: Academy of Sciences of the USSR // Leningrad Branch, 1950.
17. Siegmund, E. SalmoFan™ colour scale: principles and application //Aquaculture North America, 2015. URL: https://ericsiegmund.com/fireant/2015/03/12/150312_salmofan/ (date of access: 01.04.2025).
18. State Standard R 58165–2018. Fish, Non-Fish Objects, and Products Derived from Them. Methods of Colour Determination // Moscow: Standartinform, 2018. 16 p.
19. Albendea, P. et al. Effect of feeding acid oils on European seabass fillet lipid composition, oxidative stability, colour, and sensory acceptance //Aquaculture Nutritionm, 2023, V. 2023, # 1, p. 6415693.
20. Kimiya, T., et. al. VIS/NIR spectroscopy for nondestructive freshness assessment of Atlantic salmon (Salmo salar L.) fillets // Journal of Food Engineering, 2013, Vol. 116, # 3, pp. 758–764.
21. Schubring, R. Quality assessment of fish and fishery products by colour measurement. Handbook of seafood and seafood products analysis // CRC Press, 2009, pp. 413–442.
22. Medeiros, E.C., Almeida, L.M., Filho J.G.d.A.T. Computer vision and machine learning for tuna and salmon meat classification // Informatics, MDPI, 2021, Vol. 8, # 4, p. 70.
23. Dissing, B. S. et al. Multispectral imaging for determination of astaxanthin concentration in salmonids // PloS one, 2011, Vol. 6, # 5, p. e19032.

The subject of the research is colour measuring instruments. The aim of the work is to classify colour measuring instruments and the fields of colorimetry. The methodology and methods of the research are based on the basic concepts, principles and methods of scientific research, such as the principle of systematicity, the principle of cause-and-effect relationships, methods of a systems approach and comparative analysis, and the intellectualization of information processes. The research is based on classification as a method that allows for the description of a multi-level, branched system of elements and their relationships. As a results: the classification of spectral and integral colour measuring instruments for non-luminous colour objects can be compared with the classification of optoelectronic devices and systems. However, in modern realities, some adjustments are necessary. Therefore, the author's classification was proposed. Also, based on the research, a classification of systems, types, and devices of technical colorimetry is presented. Practical significance of the work is that classification was prepared in such a way as to create the most comprehensive overview of the main technical colorimetric systems, devices, and instruments; explain the difference between a colour space and a colour system; consider the methods of colour registration. The presented material should help researchers, using colour digital recorders in their experiments, eliminate colour loss and, consequently, measurement errors already at the recording stage.

1. Yoshi Ohno. CIE Fundamentals for Colour Measurements // IS&Ts NIP16: 2000 International Conference on Digital Printing Technologies, 2000. pp. 540–545. DOI:10.2352/ISSN.2169-4451.2000.16.1. art00033_2
2. Zhbanova, V.L. Features of digital colorimetry application in modern scientific research // Light & Engineering, 2021, Vol. 29, # 3, pp. 146–158. DOI: 10.33383/2021-028
3. Schults, E.V., Monogarova, O.V., Oskolok, K.V. Digital Colorimetry: Analytical Possibilities and Prospects of Use // MOSCOW UNIVERSITY CHEMISTRY BULLETIN, 2018, Vol. 74, # 2, pp. 55–62. DOI: 10.3103/S002713141902007X
4. Meshkov, V.V., Matveev, A.B. Fundamentals of Lighting Engineering. Part 2. Physiological Optics and Colourimetry. 2nd ed. [Osnovy svetotehniki. Ch. 2. Fiziologicheskaya optika i kolorimetriya. 2‑e izd.] / Moscow: Energoatomizdat, 1989, 432 p.
5. Judd, D., Wyszecki, G. Colour in Science and Technology [Cvet v nauke i tehnike] / Moscow: Mir, 1978, 592 p.
6. Krivosheev, M.I., Kustarev, A.K. Colour measurements [Cvetovye izmereniya] / Moscow: Energo-atomizdat, 1990, 240 p.
7. Ivens, R.M. Introduction to Colour Theory [Vvedenie v teoriyu cveta] / Translated from English, Moscow: Mir, 1964.
8. Domasev, M.V., Gnatyuk, S.P. Colour, colour management, colour calculations and measurements [Cvet, upravlenie cvetom, cvetovye raschety i izmereniya] / St. Petersburg: Piter, 2009, 224 p.
9. Lozhkin, L.D., Voronoy, A.A., Soldatov, A.A. Transformation of the CIE colour space into a strictly uniform colour spase based on tensor calculus [Preobrazovanie cvetovogo prostranstva MKO v strogo ravnokontrastnoe na osnove tenzornogo ischisleniya] // Physics of wave processes and radio engineering systems, 2016, Vol. 19, # 4, pp. 50–59.
10. Zhbanova, V.L. Research into Methods for Determining Colour Differences in the CIE LAB Uniform Colour Space // Light & Engineering, 2020, Vol. 28, # 3, pp. 53–59. DOI: 10.33383/2019-005
11. Zhbanova, V.L. Evaluation and selection of colour spaces for digital systems // Light & Engineering, 2020, Vol. 28, # 6, pp. 86–94. DOI: 10.33383/2020-024
12. Zhbanova, V.L. Development and research of optical-electronic colour separation systems for matrix photodetectors [Razrabotka i issledovanie optikoehlektronnyh sistem cvetodeleniya dlya matrichnyh fotopriemnikov] / Dissertation, Moscow, 2015, 124 p.
13. Yakushenkov, Yu.G. Theory and calculation of optical-electronic devices [Teoriya i raschet optiko-ehlektronnyh priborov] 4th ed. / Moscow: Logos, 1999, 480 p.
14. Parvulyusov, Yu.B., Rodionov, S.A., Soldatov, V.P., Shekhonin, A.A., Yakushenkov, Yu.G., Yakushenkov, Yu.G. Design of optical and electronic devices [Proektirovanie optiko-ehlektronnyh priborov] / A textbook for universities 2nd ed. M.: Logos, 2000, 488 p.
15. Shchetinin, E. Yu. Model for detecting objects in infrared images obtained by unmanned aerial vehicles [Model' obnaruzheniya ob"ektov v izobrazheniyah infrakrasnogo spektra, poluchennyh bespilotnymi letatel'nymi apparatami] // Applied Informatics, 2025, Vol. 20, # 1, pp. 16–27. DOI: 10.37791/2687-0649-2025-20-1-16-27

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