JP6316940B2 - Optical element having wavelength selectivity and lamp device using the same - Google Patents

Description

  The present invention relates to an optical element having wavelength selectivity and a lamp device using the optical element.

  In the case of obtaining light of a specific color from a light source, the conventional technology uses a configuration in which light emitted from a white light source is temporarily shielded by an exterior part including a pigment, and light having a necessary wavelength is selectively transmitted (for example, patents). Reference 1). Further, as a technique related to an optical element having wavelength selectivity, Patent Document 2 discloses an optical element that gives wavelength selectivity to outgoing light by continuously changing the thickness of a multilayer film laminated on a light guide plate. Have been described. Further, Patent Document 3 describes an optical device that propagates image information by forming a reflective volume hologram on a light guide plate.

JP-A-6-234602 JP 2002-72010 A JP 2008-20770 A

  In the configuration of Patent Document 1, since a part of the light source light is absorbed by the exterior component including the pigment, the light use efficiency is lowered.

  In Patent Document 2, at least two types of low-refractive index materials and high-refractive index materials different from the substrate material are required, and there is a problem that the cost of the process of forming by changing the film thickness is high.

  In Patent Document 3, there is a problem that the reflection type volume hologram has angle selectivity, and the wavelength selectivity cannot be maintained with respect to a wide range of incident angles equal to or greater than the critical angle.

  In order to solve the above problems, for example, the configuration described in the claims is adopted. For example, an optical element having wavelength selectivity includes a transparent substrate that propagates light, and diffraction gratings formed on the upper and lower surfaces of the transparent substrate, and receives white light from the end surface of the transparent substrate. In addition, light having a specific wavelength is emitted from the diffraction grating on the upper surface or the lower surface. Alternatively, the optical element having wavelength selectivity has a configuration in which the exit surface of the lens is convex, and a blazed diffraction grating that emits light of a specific wavelength is formed on the exit surface.

  The lamp device of the present invention includes a light source, a lens unit that collects light emitted from the light source, and a light guide disposed on an outer periphery of the lens unit, and an inner peripheral surface of the light guide In this configuration, a diffraction grating that selectively emits light of a specific wavelength is formed.

  According to the present invention, an optical element which can be applied to a light source having a wide emission angle distribution, has no light absorption loss, and has a single material and low wavelength selectivity can be obtained. Further, by using this optical element, a lamp device with a simple structure and high light utilization efficiency can be realized.

Sectional drawing which shows a mode that the structure of the light-guide plate of Example 1, and a light guide. In Example 2 (type B diffraction grating), a light ray diagram of diffracted light when blue light is incident. The figure which shows the efficiency of each diffracted light radiate | emitted from the board | substrate upper surface. The figure which shows the efficiency of each diffracted light reflected on a board | substrate upper surface. The figure which shows the propagation efficiency of the designated order light. In Example 2 (type B diffraction grating), a ray diagram of diffracted light when red light is incident. The figure which shows the efficiency of each diffracted light radiate | emitted from the board | substrate upper surface. The figure which shows the efficiency of each diffracted light reflected on a board | substrate upper surface. The figure which shows the propagation efficiency of the designated order light. The figure which shows the wavelength dependence of the output efficiency and propagation efficiency in Example 2 (type B diffraction grating). The figure which shows the emitted light intensity distribution with respect to propagation distance (before area compensation). The figure which shows the area ratio of the diffraction grating area | region for equalizing luminescence intensity. The figure which shows the emitted light intensity distribution with respect to propagation distance (after area compensation). The figure which showed the emission spectrum for every propagation distance. In Example 3 (type R diffraction grating), the figure shows the efficiency of each diffracted light emitted from the upper surface of the substrate when red light is incident. The figure which shows the efficiency of each diffracted light reflected on a board | substrate upper surface. The figure which shows the propagation efficiency of the designated order light. In Example 3 (type R diffraction grating), the figure shows the efficiency of each diffracted light emitted from the upper surface of the substrate when blue light is incident. The figure which shows the efficiency of each diffracted light reflected on a board | substrate upper surface. The figure which shows the propagation efficiency of the designated order light. The figure which shows the wavelength dependence of the output efficiency and propagation efficiency in Example 3 (type R diffraction grating). The figure which shows the emitted light intensity distribution with respect to propagation distance (before area compensation). The figure which shows the area ratio of the diffraction grating area | region for equalizing luminescence intensity. The figure which shows the emitted light intensity distribution with respect to propagation distance (after area compensation). The figure which showed the emission spectrum for every propagation distance. FIG. 6 shows a configuration of a diffractive lens of Example 4. The figure which shows the lens data of the 1st example which makes the number of ring zones = 659. The figure which shows the lens data of the 2nd example which makes the number of ring zones = 220. Sectional drawing which shows the structure of the lamp device of Example 5. FIG.

  Embodiments of the present invention will be described below with reference to the drawings.

In the first embodiment, a basic configuration will be described using a light guide plate as an example of an optical element.
FIG. 1 is a cross-sectional view showing the configuration of the light guide plate of this embodiment and how light is guided. The light guide plate includes a transparent light guide plate substrate 101 and a diffusion plate 120, and a light source 102 such as a white LED is disposed on an end surface of the light guide plate substrate 101. The light guide plate has a long shape extending in the light guide direction, but in FIG. 1, the light guide plate is divided into three regions 104, 105, and 106 in the longitudinal direction using broken lines.

  The end surface of the light guide plate substrate 101 is cut obliquely, and is an incident surface on which the white light 103 from the light source 102 enters. The incident direction of the light beam having the highest intensity among the incident light is set to be a predetermined incident angle θ0 (a value intermediate between the critical angle of total reflection in the substrate 101 and 90 °). Blaze diffraction gratings (sawtooth grooves) are formed on the upper and lower surfaces of the light guide plate substrate 101, and light having a specific wavelength is emitted from the blazed diffraction grating on the upper surface while propagating through the substrate 101. . The shape of the blazed diffraction grating, that is, the grating depth and the grating pitch are different depending on the grating regions 104, 105, and 106 in the propagation direction of the substrate 101. Accordingly, light of different wavelengths λ1, λ2, and λ3 can be emitted from the respective grating regions 104, 105, and 106.

  The light emitted from the light guide plate substrate 101 is set so that the diffraction efficiency of transmitting the upper surface at a specific wavelength is larger than that of other wavelengths due to the wavelength dependence of the diffraction angle of the blazed diffraction grating. In this case, since it is a condition that basically does not generate outgoing light at a near wavelength, the outgoing angle of the outgoing light is an outgoing angle with a large grazing of the substrate surface. For this reason, in order to enable the observer to recognize the emitted light directly facing the light guide plate surface, a diffusion plate 120 for diffusing the emitted light is disposed on the emission surface with an air gap interposed therebetween. Further, in order to support the diffusing plate 120, the supporting member 121 is disposed so as not to hinder the emission of light. On the other hand, in order to reduce the amount of light loss due to the transmitted light on the lower surface of the light guide plate substrate 101, an inclined surface is provided on the lower surface in a direction orthogonal to the traveling direction of light so that incident light rays are totally reflected and propagated. . As another configuration, a metal reflection film 122 may be coated on the lower surface.

  The shape of the diffraction grating will be described in detail. In the grating region 104, the blazed diffraction grating 107 on the upper surface and the blazed diffraction grating 108 on the lower surface are parallel to each other in the inclination directions of the grating surfaces, and the grating pitch and the grating depth are equal. Similarly, in the grating region 105, the grating surfaces of the upper surface blazed diffraction grating 109 and the lower surface blazed diffraction grating 110 are parallel to each other, and the grating pitch and the grating depth are equal. The same applies to the lattice region 106. When viewed from the incident light 103, the blazed diffraction grating 107 on the upper surface is inclined in the direction in which the incident angle of the incident light is increased, whereas the blazed surface on the lower surface of the grating region 104 is inclined. The grating surface of the diffraction grating 108 is inclined in the direction in which the incident angle of incident light decreases. The same applies to the lattice regions 105 and 106.

  By making the shape of the blazed diffraction grating up and down the same in one grating region, even if the diffraction angle by the lower surface blazed diffraction gratings 108, 110, 112 changes to θ1, θ2, θ3, the opposed upper surface blazed diffraction grating 107 , 109, 111 are diffracted in the reverse direction. As a result, the incident angle returns to the original incident angle θ0, and basically diffracted light can be stably propagated through the light guide plate substrate 101.

  A blazed diffraction grating can obtain diffracted light with a diffraction efficiency of 100% in principle at an incident angle and wavelength satisfying the diffraction conditions if the reflectivity of the interface is 100% due to total reflection or the like. . Under such conditions, light can propagate with 100% efficiency through the light guide plate substrate 101 facing the blaze diffraction grating.

  Further, the blazed diffraction grating is not formed on the entire surface of the light guide plate substrate 101 but discretely formed in a plurality of regions along the propagation direction. This is because the intensity of the emitted light is made uniform regardless of the propagation distance. For example, in the grating region 104, regions (hereinafter referred to as sub-lattice regions) in which grating grooves (blazed diffraction gratings 107 and 108) are formed are provided intermittently, and flat regions 117 and 118 in which no grating grooves are formed are arranged therebetween. The interval (the width of the flat region) is gradually narrowed in the direction in which light propagates. In the grating region 105, the number of gratings in the rightmost sub-grating region (blazed diffraction gratings 109 ′ and 110 ′) in the figure is increased, but this is because the interval between the sub-grating regions (the width of the flat region) becomes zero. Is. Since the light emitted from the light guide plate is emitted from the sub-grating region (blazed diffraction grating) at a constant rate, if the grating is formed on the entire surface, the intensity of the emitted light is reduced at a position where the propagation distance is long. Therefore, the intensity of the emitted light can be made uniform regardless of the propagation distance by discretely arranging the sub-lattice regions and changing the intervals (gradually narrowing).

  Note that the intensity of the emitted light can be made uniform by gradually increasing the area of the sub-lattice region. That is, the interval between the sub-lattice regions (the width of the flat region) may be constant, and the number of lattices in the sub-lattice region may be gradually increased according to the propagation distance. However, in order to obtain the light diffraction effect, a predetermined number of continuous lattices (several tens of lattices) is necessary, and it should not be less than this in any region.

  In each of the grating regions 104, 105, and 106, light of different wavelength components is emitted from the upper surface, so that the diffraction conditions are changed by changing the shapes of the blazed diffraction grating (grating pitch and grating depth). For example, when the incident light 103 from the light source 102 has three wavelength components λ1, λ2, and λ3, the grating region 104 mainly emits light in the vicinity of the wavelength λ1. As a result, the light beam 113 incident on the next grating region 105 is dominated by the remaining light beams having the wavelengths λ2 and λ3. In the grating region 105, light of wavelength λ2 is mainly emitted. As a result, the light beam 114 incident on the next grating region 106 is dominated by the remaining light of wavelength λ3, and the grating region 106 mainly emits light of wavelength λ3.

  In FIG. 1, the boundary positions of the sub-grid region and the flat region on the upper surface and the lower surface are shifted by a predetermined amount so that the diffracted light traveling from the sub-grid region on the lower surface is incident on the corresponding sub-lattice region on the upper surface again. doing. In this way, all light rays traveling from the lower surface sub-grid region to the upper surface are incident on the upper surface sub-grid region, and the reflection angle from the upper surface returns to the original incident angle θ0, and the light guide plate substrate 101 has Can be stably propagated.

  Thus, according to the present embodiment, a light guide plate that emits light of a desired wavelength can be provided by forming diffraction gratings having a predetermined shape on the upper and lower surfaces of the transparent substrate. Since the light guide plate of this embodiment uses a transparent substrate, there is no light absorption loss, and it can be realized with a single material at low cost.

  In the second embodiment, a light guide plate that selectively emits light having a blue wavelength will be described as a specific example of the first embodiment. In the light guide plate of Example 2, in order to selectively emit light having a blue wavelength, an opposed blazed diffraction grating having a medium refractive index of 1.5, a grating pitch of 2.4 μm, and a grating depth of 0.32 μm is used. Yes. Hereinafter, the shape of the diffraction grating is referred to as “type B”.

FIG. 2 is a ray diagram of diffracted light when blue light is incident on a type B diffraction grating.
The incident light is blue light having a wavelength of 0.45 μm, and the incident angle θ0 is 50 °. Of the light diffracted on the lower surface of the substrate, the second to diffracted light from the second order diffracted light can be emitted from the upper surface of the substrate, and the first and lower diffracted light cannot be emitted and are totally reflected. Of the first-order diffracted light reflected from the upper surface, the −1st-order diffracted light component is incident on the lower surface of the substrate again at the same incident angle of 50 ° as the original incident light. That is, this component becomes stable propagation light. Hereinafter, the intensity (efficiency) of each diffracted light will be compared.

  FIG. 3A is a diagram showing the efficiency of each diffracted light emitted from the upper surface of the substrate. Of the diffracted light (second order to eleventh order) emitted from the upper surface, the second order diffracted light is emitted with an efficiency of about 45%, but the other order lights have a low efficiency (nearly 0).

  FIG. 3B is a diagram showing the efficiency of each diffracted light reflected from the upper surface of the substrate. First-order diffracted light is reflected into the substrate with an efficiency of 40%, and then second-order diffracted light is reflected with an efficiency of about 10%.

  FIG. 3C is a diagram illustrating the propagation efficiency of the specified order light. When the intensity of the original incident light is 1, the efficiency of each order light generated as a result of the first-order diffracted light reflected on the upper surface being diffracted on the upper surface is obtained. From this, it can be seen that the −1st order diffracted light component has an efficiency of about 20%, and this propagates stably.

  From this, it can be seen that in the type B diffraction grating, the emission efficiency from the upper surface is high (about 45%) with respect to the incidence of blue light, and conversely the propagation efficiency in the substrate is low (about 20%).

  The above is the case where the incident light is blue light. Next, the case where the incident light is red light will be described for comparison.

  FIG. 4 is a ray diagram of diffracted light when red light is incident on the same type B diffraction grating as FIG. The incident light is red light with a wavelength of 0.65 μm, and the incident angle θ0 is the same 50 °. From the second-order diffracted light to the seventh-order diffracted light can be emitted from the upper surface of the substrate, and in this case, the first-order diffracted light and the like cannot be emitted and are totally reflected.

  FIG. 5A is a diagram showing the efficiency of each diffracted light emitted from the upper surface of the substrate. The second-order diffracted light has the largest amount of light, but its efficiency is about 9%, which is considerably smaller than that of the blue light (about 45%).

  FIG. 5B is a diagram showing the efficiency of each diffracted light reflected on the upper surface of the substrate. First-order diffracted light is reflected into the substrate with an efficiency of about 80%.

  FIG. 5C is a diagram showing the propagation efficiency of the specified order light. The efficiency of each order light generated as a result of the first-order diffracted light reflected on the upper surface being diffracted on the upper surface is obtained. From this, it can be seen that the −1st order diffracted light is diffracted with an efficiency of approximately 80% and propagates at the same incident angle as the incident light.

  From this, it can be seen that in the type B diffraction grating, when red light is incident, the emission efficiency from the upper surface is low (about 9%), and most of the light propagates in the substrate.

  FIG. 6 is a diagram illustrating the wavelength dependence of the emission efficiency and the propagation efficiency in a type B diffraction grating. Here, the wavelength of incident light is varied from 0.4 to 0.7 μm, and the incident angle θ0 is averaged in the range of 45 ° to 75 °. In the case of the type B diffraction grating, the blue light (wavelength near 0.45 μm) has higher emission efficiency than the red light (wavelength near 0.65 μm), and conversely, the propagation efficiency is low.

Next, a change in the emission intensity (light emission intensity) with respect to the propagation distance in the light guide plate will be described.
FIG. 7A is a diagram showing a light emission intensity distribution with respect to a propagation distance, and shows a case where diffraction grating regions are continuously formed for comparison (before area compensation). It is assumed that the substrate is 3 mm thick and type B diffraction gratings are continuously formed on the upper and lower surfaces of the substrate. The logarithm of the light emission intensity per unit length with respect to the propagation distance, assuming that light is emitted uniformly from the amount of light emitted per propagation length. Although blue light (wavelength: 0.45 μm) has a high emission intensity at a propagation distance of 0 (the vertical axis is a logarithmic display, the difference on the drawing appears small), the intensity rapidly decreases with the propagation distance. Even at other wavelengths, the emission intensity rapidly decreases with the propagation distance.

  FIG. 7B is a diagram showing the area ratio of the diffraction grating region for making the emission intensity uniform. The ratio of the area of the diffraction grating region at each propagation distance is changed and set so that the emission intensity shown in FIG. 7A is uniform with respect to the propagation distance. Assuming a propagation distance of 100 mm, the light emission intensity is suppressed by setting the area ratio of the grating region to about 10% at the light incident position (distance = 0), and the ratio is gradually increased from that to be set to 100% at the terminal position. doing.

  FIG. 7C is a diagram showing a light emission intensity distribution after area compensation. Here, the area ratio of the diffraction grating region shown in FIG. 7B is set to compensate the emission intensity distribution. The vertical axis represents linear coordinates. Compared with the emission intensity distribution of FIG. 7A, the change with respect to the propagation distance is relaxed. The emission intensity of blue light (wavelength 0.45 μm) is larger than other wavelengths in the range up to a propagation distance of 50 mm.

  FIG. 7D is a diagram showing an emission spectrum for each propagation distance. Blue light (wavelength 0.45 μm) is dominant in the section where the propagation distance is short (distance 0 to 30 mm), and red light (wavelength 0.65 μm) becomes dominant when the propagation distance becomes long (distance 80 to 100 mm). Come.

  According to the present embodiment, it is possible to provide a light guide plate that selectively emits light having a blue wavelength, and to make the light emission intensity distribution with respect to the propagation distance uniform.

  In the third embodiment, a light guide plate that selectively emits light having a red wavelength will be described as a specific example of the first embodiment. In the light guide plate of Example 3, in order to selectively emit light having a red wavelength, an opposing blazed diffraction grating having a medium refractive index of 1.5, a grating pitch of 2.4 μm, and a grating depth of 0.21 μm is used. Yes. Hereinafter, the shape of the diffraction grating is referred to as “type R”. Hereinafter, a case where red light is incident on a light guide plate having a type R diffraction grating is compared with a case where blue light is incident.

  First, the case where red light (wavelength 0.65 μm) is incident at an incident angle of 50 ° will be described. The ray diagram is the same as FIG. 4 having the same grating pitch and wavelength.

  FIG. 8A is a diagram showing the efficiency of each diffracted light emitted from the upper surface of the substrate when red light is incident. First-order diffracted light is emitted from the upper surface with an efficiency of 40% or more.

  FIG. 8B is a diagram showing the efficiency of each diffracted light reflected from the upper surface of the substrate. The 0th order light and the 1st order diffracted light are reflected into the substrate with an efficiency of about 25% to 20%.

  FIG. 8C is a diagram illustrating the propagation efficiency of the specified order light. The efficiency of each order light produced as a result of the first-order diffracted light reflected from the upper surface being diffracted by the upper surface is shown. Accordingly, the −1st order diffracted light component has an efficiency of about 20%, and becomes propagation light at the same incident angle as the incident light. In FIG. 8B, the 0th-order light also has the same amount of light, and when combined, the light propagating at the original incident angle is estimated to be about 40%.

  From this, it can be seen that in the type R diffraction grating, the emission efficiency from the upper surface and the propagation efficiency in the substrate are approximately the same (about 40%) with respect to the incidence of red light.

  Next, for comparison, a case where blue light (wavelength 0.45 μm) is incident at an incident angle of 50 ° will be described. The ray diagram is the same as FIG. 2 having the same grating pitch and wavelength.

  FIG. 9A is a diagram showing the efficiency of each diffracted light emitted from the upper surface of the substrate when blue light is incident. Although the 2nd to 11th order diffracted lights are emitted from the upper surface, the efficiency is 3% or less (the total of each order light is about 8%), which is considerably smaller than the case of the red light (40% or more). Become. .

  FIG. 9B is a diagram showing the efficiency of each diffracted light reflected on the upper surface of the substrate. First-order diffracted light is reflected into the substrate with an efficiency of 80% or more.

  FIG. 9C is a diagram illustrating the propagation efficiency of the specified order light. The efficiency of each order light generated as a result of the first-order diffracted light reflected on the upper surface being diffracted on the upper surface is obtained. From this, it can be seen that the −1st order diffracted light is diffracted with an efficiency of approximately 80% and propagates at the same incident angle as the incident light.

  From this, it can be seen that in the type R diffraction grating, when blue light is incident, the emission efficiency from the upper surface is low (about 8%), and most of the light propagates in the substrate.

  FIG. 10 is a diagram showing the wavelength dependence of the emission efficiency and propagation efficiency in a type A diffraction grating. The wavelength of incident light is changed from 0.4 to 0.7 μm, and the incident angle θ0 is averaged in the range of 45 ° to 75 °. In the case of a type A diffraction grating, red light (near wavelength 0.65 μm) has higher emission efficiency than blue light (near wavelength 0.45 μm), and conversely, propagation efficiency is low.

Next, a change in the emission intensity (light emission intensity) with respect to the propagation distance in the light guide plate will be described.
FIG. 11A is a diagram showing a light emission intensity distribution with respect to a propagation distance, and shows a case where diffraction grating regions are continuously formed for comparison (before area compensation). It is assumed that the substrate is 3 mm thick and type R diffraction gratings are continuously formed on the upper and lower surfaces of the substrate. Although red light (wavelength 0.65 μm) has a high emission intensity at a propagation distance of 0 (the vertical axis is a logarithmic display, the difference on the drawing appears small), the intensity rapidly decreases with the propagation distance.

  FIG. 11B is a diagram showing the area ratio of the diffraction grating region for uniformizing the emission intensity. The ratio of the area of the diffraction grating region at each propagation distance is changed and set so that the light emission intensity shown in FIG. 11A is uniform with respect to the propagation distance. Assuming a propagation distance of 100 mm, the light emission intensity is suppressed by setting the area ratio of the grating region to about 10% at the light incident position (distance = 0), and the ratio is gradually increased from that to be set to 100% at the terminal position. doing.

  FIG. 11C is a diagram showing a light emission intensity distribution after area compensation. Here, the area ratio of the diffraction grating region shown in FIG. 11B is set to compensate the emission intensity distribution. Compared with the emission intensity distribution of FIG. 11A, the change with respect to the propagation distance is relaxed. The emission intensity of red light (wavelength 0.65 μm) is larger than other wavelengths in the range up to a propagation distance of 80 mm.

  FIG. 11D is a diagram showing an emission spectrum for each propagation distance. In the section where the propagation distance is short (distance 0 to 60 mm), the red light is dominant, and when the propagation distance is long (distance 90 to 100 mm), the blue light becomes dominant.

  According to the present embodiment, it is possible to provide a light guide plate that selectively emits light having a red wavelength, and to make the light emission intensity distribution with respect to the propagation distance uniform.

In Example 4, a diffractive lens will be described as an example of an optical element.
FIG. 12 is a diagram showing a configuration of the diffractive lens of the present example. (A) is a cross-sectional shape of a conventional lens 200 ′ for comparison, (b) is a cross-sectional shape of the lens 200 of the present embodiment, and (c) is an enlarged view of a lens exit surface. In this embodiment, a blazed diffraction grating 203 is formed on the exit surface 202 of the lens. A refracting action is imparted to the lens by the diffractive action of the blaze diffraction grating, and the lens is made thinner without changing the overall shape of the exit surface 202. That is, the incident surface of the lens can be a meniscus shape that is a concave surface 201 instead of the conventional flat surface 201 ′ shape, and the lens thickness t at the center of the optical axis is changed from 22.7 mm to 15.44 mm. Reduced to -32% thinner. In the present embodiment, since the shape of the exit surface is not changed, it is suitable for an application to be used without changing the appearance of the lens, such as a headlight for an automobile. The light distribution characteristics of the diffractive lens 200 are the same as those of the conventional lens 200 ′ because higher-order components of the diffracted light are averaged.

  Hereinafter, two specific examples of the lens data of the diffractive lens are shown. By using higher-order diffracted light in the diffractive lens, it is possible to change the diffraction grating shape for realizing the same thin shape, that is, the relationship between the grating pitch (ring zone width) and the grating depth (ring zone depth). it can.

  FIG. 13 is a diagram showing lens data of the first example in which the number of annular zones = 659. (A) is basic lens data, (b) is the size of the ring width p at each radial position, and (c) is the actual annular zone shape near the center of the lens. It can be seen that the diffraction grating (ring zone) is formed while maintaining the base shape of the emission surface.

  FIG. 14 is a diagram showing lens data of a second example in which the number of annular zones = 220. (A) is basic lens data, (b) is the size of the ring width p at each radial position, and (c) is the actual annular zone shape near the center of the lens. By reducing the number of ring zones as compared with FIG. 13, the zone width and ring zone depth are increased.

  According to the present embodiment, by using a lens having a diffraction grating formed on the exit surface, the lens can be significantly reduced in thickness, and the lens molding time and cost can be reduced.

  In Example 5, a lamp device using the optical element (light guide plate) having wavelength selectivity of Examples 1 to 3 will be described.

  FIG. 15 is a cross-sectional view showing the configuration of the lamp device of this embodiment. The lamp device includes a light source 300, a lens unit 301, a light guide 302, and a reflector 303. The lens part 301 has a convex exit surface, and the light guide 302 is arranged in a ring shape on the outer periphery of the lens part 301. A blazed diffraction grating 304 is formed on the inner peripheral surface of the light guide 302. As described in the first to third embodiments, the blazed diffraction grating 304 selectively emits light having a specific wavelength according to the diffraction conditions.

  The light source light emitted from the light source 300 and reflected by the reflector 303 is collected by the lens unit 301. The light that has passed through the central portion of the lens portion 301 is emitted as the main illumination light 310 as it is. On the other hand, light that has passed through the periphery of the lens unit 301 enters the blazed diffraction grating 304, and part of the diffracted light propagates through the light guide 302 and exits forward as ring-shaped sub-illumination light 311. When the light source 300 is white light, the main illumination light 310 is white light, but the ring-shaped sub illumination light 310 can be illumination light having a specific wavelength determined by the diffraction grating shape. At this time, if the ring-shaped diffraction grating shape is made different at the circumferential position, the sub illumination light 310 of different colors (for example, red and yellow) at the circumferential position can be obtained. Since the colored sub illumination light 310 is generated by the diffraction action, there is no absorption loss in the light guide plate 302 and the light transmission efficiency is excellent.

  According to the present embodiment, it is possible to realize a lamp device having a simple structure that can efficiently emit illumination light of a plurality of types of colors while using one light source.

101: a light guide plate substrate,
102: light source,
103, 113, 114: incident light,
104, 105, 106: lattice region,
107-112: Blaze diffraction grating (sub-grating region),
117, 118: flat region,
120: diffusion plate,
121: a support member;
122: Metal reflective film,
200: diffractive lens,
201: incident surface,
202: emission surface,
203: Blaze diffraction grating,
201: incident surface,
300: Light source,
301: Lens part,
302: Light guide,
303: reflector,
304: Blaze diffraction grating
310, 311: Illumination light.

Claims (8)

A transparent substrate that propagates light from the light source ;
A blazed diffraction grating formed on the first surface and the second surface of the transparent substrate,
From the end surface of the transparent substrate, incident white light from the light source, it emits light of a specific wavelength from the blaze diffraction grating of the second surface of the blazed diffraction grating or the transparent substrate of the first surface of the transparent substrate ,
Wherein the corresponding inclination direction of the grating surface of the blazed diffraction grating of the second surface of the transparent substrate and the blazed diffraction grating of the first surface of the transparent substrate are parallel to each other, an optical having a wavelength selectivity element. An optical element having wavelength selectivity according to claim 1,
One of the first surface of the transparent substrate and the second surface of the transparent substrate is inclined in a direction in which the incident angle of incident light increases, and the other has a smaller incident angle of incident light. wherein the lattice plane in the direction is inclined, an optical element having wavelength selectivity. An optical element having wavelength selectivity according to claim 1,
The optical element having wavelength selectivity , wherein the blazed diffraction grating is discretely formed in a plurality of regions along the light propagation direction of the transparent substrate . An optical element having wavelength selectivity according to claim 3 ,
An optical element having wavelength selectivity , wherein an interval between regions where the blazed diffraction grating is formed is gradually narrowed along a light propagation direction . An optical element having wavelength selectivity according to claim 3 ,
Characterized in that gradually increased lattice number of the area in which the blazed diffraction grating is formed along the propagation direction of light, an optical element having wavelength selectivity. An optical element having wavelength selectivity according to claim 1 ,
A plurality of grating regions having different grating pitches or grating depths of the blazed diffraction grating are disposed along the light propagation direction of the transparent substrate,
An optical element having wavelength selectivity , wherein light having different wavelengths is emitted from each of the grating regions . An optical element having wavelength selectivity according to claim 1,
An optical element having wavelength selectivity , characterized in that a diffusion plate for diffusing outgoing light is provided in the vicinity of the first surface of the transparent substrate. An optical element having wavelength selectivity according to claim 7 ,
An optical element having wavelength selectivity , wherein a metal reflection film is provided on the second surface of the transparent substrate.

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