Circularly polarized light source and illumination

Abstract

To provide a highly efficient circularly polarized light source and illumination. [Solution] Of the light emitted from light source 1, the portion that passes through the polarizing beam splitter 2 is converted to circularly polarized light 6 by passing through the λ / 4 phase difference plate 3. The light that undergoes total internal reflection by the polarizing beam splitter 2 passes back and forth through the λ / 4 phase difference plate 4 by the mirror 5, rotating its polarization direction by 90°, and as a result of passing through the polarizing beam splitter 2, it is converted to circularly polarized light 7 with the same rotation as circularly polarized light 6.

Description

Technical Field

[0001] The present invention relates to a light source that generates circularly polarized light and emits it to the outside, and lighting.

Background Art

[0002] In recent years, circularly polarized light has attracted attention, and research and development of highly efficient circularly polarized light sources have been actively carried out.

[0003] The most famous method is to circularly polarize linearly polarized light extracted from light emitted from a light source with a polarizing plate using a λ / 4 retardation plate. When this method is applied to LEDs, which are currently the mainstream light sources, since the emitted light of the LEDs is unpolarized, the conversion efficiency to circularly polarized light is estimated to be 50%. If an LD is used, since the emitted light itself is linearly polarized, it is possible to remove the polarizing plate and achieve a conversion efficiency of 100%. However, an LD is expensive compared to an LED, and its light is excellent in directivity and straightness, so it is not suitable for lighting applications.

[0004] It has been known for quite some time that right-handed circularly polarized light promotes photosynthesis more than left-handed polarized light, as shown in Non-Patent Document 1. Patent Document 1 is a known example of a right-handed polarized light source developed for use in plant cultivation, in which a diffusive reflector, a polarization beam splitter, and a λ / 4 retardation plate are arranged in front of the light source. This is a method of taking out circularly polarized light by converting it into circularly polarized light by passing it through a polarization beam splitter and creating linearly polarized light that is reflected by the diffusive reflector to disrupt the polarization and recursively passes through the polarization beam splitter. A Wollaston prism in which calcite having birefringence is bonded is used for the polarization beam splitter, resulting in an expensive system. Further, as described in Patent Document 2, the extraction efficiency decreases because there is light that reciprocates through the optical elements many times.

[0005] Patent Document 2 is an improvement on Patent Document 1 and describes three methods, but the first embodiment is relevant to the present invention. A light-emitting element such as an LED is placed between a polarizing beam splitter that transmits s-polarized light and a polarizing beam splitter that transmits p-polarized light, and λ / 4 phase difference plates are placed outside them. This makes it possible to generate the desired circularly polarized light with higher efficiency than Patent Document 1. However, Patent Document 2 is designed for light sources for plant cultivation and emits light from both sides of a planar light source, and is not suitable for lighting that is installed on the ceiling and emits light from one side. In addition, regardless of what polarizing beam splitter is used, the structure is complex and therefore expensive, and using two of them is disadvantageous in terms of cost.

[0006] In recent years, research has been conducted on using chiral materials as circularly polarized light-emitting materials, as described in Non-Patent Document 2, but it does not yet appear to have reached the level of practical application. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 5951190 [Patent Document 2] Patent No. 5973944 [Non-patent literature]

[0008] [Non-Patent Document 1] Limnology and Oceanography, Vol. 2, p. 113 (1957). [Non-Patent Document 2] Toyota Research Report, No. 74, p. 208 (2021). [Non-Patent Document 3] Biosci., Biotechnol., Biochem., Vol. 86, p. 1173 (2022). [Non-Patent Document 4] Journal of the Japanese Society of Cataract Surgery, Vol. 29, p. 13 (2017). [Overview of the project] [Problems that the invention aims to solve]

[0009] The objective of this invention is to provide a highly efficient and practical circularly polarized light source and illumination using it. While circular polarization is used in displays and the like, another important objective of this invention is to realize a light source and illumination that can at least suppress photoaging, and ideally even rejuvenate, living organisms, including humans. Therefore, we would like to explain the inventor's view on the relationship between living organisms and circular polarization.

[0010] Traditionally, this has been justified by the ability of living organisms to perceive circularly polarized light, but the inventors believe that circularly polarized light became important to living organisms due to the stable utilization of light energy.

[0011] If a photosynthetic organism had photosynthetic properties dependent on linearly polarized light, it would have to adjust its optical settings to optimize for linear polarization, thus consuming energy. On the other hand, current D-circularly polarized chlorophyll has an efficient biological system that automatically utilizes half of the light for photosynthesis, regardless of the optical axis, and this is a rational reason to consider as the reason why plants use circularly polarized light for photosynthesis.

[0012] The sugars synthesized by living organisms are of the D type, and as shown in Non-Patent Document 1 and Patent Document 1, right-handed circularly polarized light is important for photosynthesis and plant development. Patent Document 1 shows that when komatsuna (Japanese mustard spinach) is irradiated only with left-handed circularly polarized light, it causes weight loss, suggesting that left-handed circularly polarized light may not be utilized for photosynthesis.

[0013] Since life is thought to have built efficient systems during the process of evolution, it is reasonable to assume that left-handed circularly polarized light, which is not used in photosynthesis, is also being utilized effectively in some way. On the other hand, enzymes and energy sources such as ATP are used in the metabolic cycle of amino acids, and no involvement of light has been reported. In Japan, there is a proverb that says "sleeping children grow," and since growth hormone is secreted during sleep at night to promote growth, it seems that the biological system has built a biosynthesis chemical system for amino acids, proteins, etc. that does not use light in order to make effective use of nighttime hours. However, since the body comes first, there is room for various considerations as to why this amino acid synthesis system does not use light.

[0014] Based on the above, the inventors have concluded that left-handed circularly polarized light, which is not used in photosynthesis, is used for body protection and defense. For example, Non-Patent Document 3 states that the synthesis of L-ascorbic acid, which protects the body from reactive oxygen species generated during photosynthesis in plants, is closely related to light, becoming more active the stronger the light intensity, and conversely, becoming inactive at night when there is no light. However, it is stated that the details of the synthesis mechanism are unknown as the research has just begun, but based on what has been considered so far, it is appropriate to think that L-ascorbic acid makes effective use of light by utilizing left-handed circularly polarized light that is not used in photosynthesis. If this is the case, it can also explain why L-ascorbic acid synthesis is inactive at night.

[0015] The bodies of living organisms are composed of proteins, and life activities are carried out by the various physical functions of proteins, such as their mechanical and optical properties. However, in recent years, it has become recognized that aging is the result of a breakdown in the homochirality of the amino acids that make up proteins (Non-Patent Literature 4).

[0016] As Non-Patent Document 4 points out, normal amino acids are levorotatory (L-type), but aging is understood as a state in which the denaturation of normal L-amino acids into dextrorotatory (D-type) increases, resulting in racemization. This disruption of the beautiful amino acid sequence of normal proteins makes it impossible to maintain physical properties such as mechanical and optical properties, and thus the body is unable to perform normal functions. Such disruption of amino acid homochirality has been observed in various age-related diseases such as cataracts, age-related macular degeneration, Alzheimer's disease, skin hardening, and arteriosclerosis.

[0017] Non-patent document 4 clarifies that cataracts are a disease in which the lens of the eye undergoes D-denaturation of L-aspartic acid, leading to racemization, disruption of the beautiful amino acid sequence, and clouding. According to Non-patent document 4, racemization of L-aspartic acid has already begun even in the lenses of children, and the inventors believe that normalizing amino acids is an important issue even for young people.

[0018] The optical isomerism of amino acids stems from circular dichroism, which is the rotational dependence of the circular polarization of their ultraviolet absorption peak (and the wavelength range of its tail). Specifically, L-amino acids are levorotatory due to their high absorption rate of right-handed circularly polarized light, while D-amino acids are dextrorotatory due to their high absorption rate of left-handed circularly polarized light. Of the amino acids that make up living organisms, only glycine lacks a chiral carbon and is therefore not an optical isomer.

[0019] Based on the above, photoaging can be redefined as the photochemical change of L-amino acids to D-amino acids due to light absorption, and it is certain that right-handed circularly polarized light has a greater photodegradation effect on L-amino acids than left-handed circularly polarized light. Furthermore, since left-handed circularly polarized light has the effect of converting D-amino acids to L-amino acids, a healing effect can also be expected. If amino acids also exhibit the complete rotational selectivity suggested in photosynthesis in Patent Document 1, then left-handed circularly polarized light is highly likely to be a healing light for living organisms, possessing a healing effect that maintains the normal state of L-amino acids.

[0020] Here, let's consider the photoexcitation of amino acid molecules. First, upon photoexcitation, the tetrahedral structure becomes a planar excited molecule, and the switching of one functional group (presumably hydrogen) above and below the plane will likely result in the switching between L-form and D-form. At this time, for circularly polarized light, there is a rotational property that determines which form is stable (in the low-energy state), leading to selectivity. Considering the situation of photosynthesis, it is thought that in left-handed circularly polarized light, it is easier to become L-form, and in right-handed circularly polarized light, it is easier to become D-form.

[0021] It is a matter of concern that the saccharides in the human body are dextrorotatory and should undergo a conversion from dextrorotatory to levorotatory upon irradiation with left-handed circularly polarized light. Since the DNA and RNA of genes are based on pentoses, 2-deoxy-D-ribose and D-ribose respectively, the L-conversion by light is indeed a cause for concern. However, considering that genes have a repair mechanism and DNA has a double-stranded structure in the living body but the two gene molecules are free in the liquid, it is thought that the sequence disorder like that of proteins will not occur and the adverse effects are small. Especially for RNA, since it is a single gene molecule free in the cell fluid, it seems that there is no effect of the L-conversion of D-ribose.

[0022] To summarize the above, for the stable and efficient utilization of light energy, life has evolved to utilize circularly polarized light. The inventor believes that right-handed circularly polarized light is used for energy acquisition in photosynthesis, and left-handed circularly polarized light is used to remove and improve the harmful effects of light such as reactive oxygen species and photoaging generated in photosynthesis. Also, the mysterious phenomenon that amino acids are levorotatory and saccharides are dextrorotatory in life can be reasonably explained.

[0023] Particularly in animals that do not perform photosynthesis, there seems to be no problem in removing the right-handed circularly polarized light necessary for photosynthesis. The left-handed circularly polarized light of the light source and lighting can be expected to at least suppress photoaging and, at best, have an improving and restorative effect. Therefore, the inventor believes that the practical application of a highly efficient circularly polarized light source is important for the improvement of human health.

[0024] In the future, measuring the absorption coefficients of various circularly polarized light sources in amino acids and other substances, and confirming their effects through experiments, will be crucial. Furthermore, while right-handed circularly polarized light is unnecessary in animals compared to plants, it is possible that animals may evolve to effectively utilize this unnecessary light. Therefore, the role of right-handed circularly polarized light in animals is a research topic that cannot be ignored. [Means for solving the problem]

[0025] For light sources usable for indoor lighting, a configuration in which circularly polarized light is emitted efficiently from one side, rather than from both sides as in Patent Document 2, is desirable. Therefore, a polarizing beam splitter (PBS) is used to completely separate s-polarized and p-polarized light. In a typical PBS, p-polarized light is transmitted through the PBS. Therefore, a λ / 4 phase difference plate is placed below the PBS to obtain the desired circularly polarized light (mainly left-handed circularly polarized light). On the other hand, the totally reflected s-polarized light is reflected back to the PBS by an optical system with a λ / 4 phase difference plate and mirrors placed above the PBS. At this time, the polarization direction of the s-polarized light rotates by 90° as it passes back and forth through the λ / 4 phase difference plate, becoming p-polarized light, which is then transmitted through the PBS to become the desired circularly polarized light. In reality, there are small losses, but the conversion to circularly polarized light is approximately 100% efficient. [Effects of the Invention]

[0026] By using a polarizing beam splitter (PBS), a λ / 4 phase difference plate, and mirrors, it is possible to achieve a circularly polarized light source by linearly polarizing incident light in one direction with nearly 100% efficiency, making it suitable for lighting applications. Left-handed circular polarization, in particular, has at least an inhibitory effect on photoaging, and in the best case, a photorejuvenating effect can be expected, contributing to the improvement of the user's health. [Brief explanation of the drawing]

[0027] [Figure 1] Figure 1 is a basic configuration diagram of the circularly polarized light source (illumination) of the present invention. [Figure 2] Figure 2 shows an example in which a diffuser plate is added to the configuration in Figure 1. [Figure 3] Figure 3 shows an example in which a polarizing plate is inserted between the PBS and the phase difference plate in Figure 1. [Figure 4]Figure 4 shows an example in which a polarizing plate is inserted between the PBS and the phase difference plate in Figure 2. [Modes for carrying out the invention]

[0028] Figure 1 shows a basic embodiment of the present invention, in which a polarizing beam splitter (PBS) 2 and a λ / 4 phase difference plate 3 are arranged in front of a light source 1 such as an LED. A λ / 4 phase difference plate 4 and a mirror 5 are arranged in order opposite to the PBS 2 on the opposite side of the λ / 4 phase difference plate 3. The position of the light source 1 is generally between the PBS 2 and the λ / 4 phase difference plate 4, but it may be shifted towards the mirror 4. In addition, the optical axis of the light source 1 is tilted so that the reflected light from the PBS 2 to the light source 1 is reflected back to the light source 1 as little as possible. Various types can be used for the PBS 2, but considering cost and simplicity, multilayer optical film (MOF) or multilayer dielectric thin film types are preferable. It goes without saying that any optical components described as plates can also be in the form of films.

[0029] In operation, the light emitted from light source 1 that passes through PBS2 is converted to circularly polarized light 6 by passing through λ / 4 phase difference plate 3. The light totally reflected by PBS2 passes back and forth through λ / 4 phase difference plate 4 by mirror 5, causing its polarization direction to rotate by 90°, making it possible to pass through PBS2. As a result, it is converted to circularly polarized light 7 with the same rotation as circularly polarized light 6.

[0030] In the embodiment shown in Figure 1, by making the λ / 4 phase difference plate 3 rotatable instead of integrating the PBS2 and the λ / 4 phase difference plate 3, it becomes possible to create any circularly polarized state.

[0031] In that case, it would be considered useful for plant cultivation. Specifically, it would be ideal to make right-handed circularly polarized light dominant during development to increase photosynthesis and promote growth, and then increase left-handed circularly polarized light components as the plant approaches the time of harvest to increase antioxidants such as vitamin C. However, detailed studies are actually needed for each individual plant.

[0032] The second embodiment is one in which a diffuser plate 8 is placed below the λ / 4 phase difference plate 3 in the embodiment shown in Figure 1. When used for illumination, this embodiment will be the basic configuration. By using left-handed circularly polarized light, it is possible to at least suppress photoaging in the user, and in the best case, a photorejuvenation effect can be expected. If the photorejuvenation effect is confirmed, left-handed circularly polarized lighting will become the mainstream in the future and will make a great contribution to improving human health.

[0033] The third embodiment is one in which a polarizing plate 9 is inserted between PBS2 and λ / 4 phase difference plate 3 in the embodiment shown in Figure 1 to remove unwanted circularly polarized components. Currently, the inventors do not recommend this embodiment. The reason is not simply that the addition of the polarizing plate 9 increases costs, but rather that, currently, the contribution of right-handed circularly polarized light to the human body is unknown, and even a small amount of right-handed circularly polarized light can reduce unnecessary risks.

[0034] The fourth embodiment is an embodiment in which a polarizing plate 9 is inserted between PBS2 and λ / 4 phase difference plate 3 in the embodiment shown in Figure 2 to remove unwanted circularly polarized components. For the same reasons as the third embodiment, this is not currently recommended. [Explanation of Symbols]

[0035] 1. Light source (LED, etc.) 2. Polarizing Beam Splitter (PBS) 3 λ / 4 retardation plate 4 λ / 4 retardation plate 5 Mirror 6. Circularly polarized light that is directly transmitted through PBS and converted. 7. Circularly polarized light converted after reflecting PBS and then off the mirror. 8. Diffuser 9 Polarizing plate

Claims

1. A first optical system consisting of a polarizing beam splitter plate and a λ / 4 phase difference plate and a second optical system consisting of a mirror and a λ / 4 phase difference plate are arranged to face each other. A light source and lighting device characterized in that the light from the light source is irradiated onto a polarizing beam splitter and arranged to separate its polarization.

2. A light source and illumination device characterized in that a diffuser plate is placed on the outside side of the first optical system according to claim 1.

3. A light source and illumination device characterized in that a polarizing plate is inserted between the polarizing beam splitter and the λ / 4 phase difference plate of the first optical system according to claims 1 and 2.

4. A light source and illumination device characterized in that the λ / 4 phase difference plate of the first optical system is rotatable, according to claims 1, 2, and 3.

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