Optical system device, and optical element

Abstract

A purpose of the present invention is to provide an optical system device and optical element that are free from the problem of peeling and enable a first optical element and a second optical element to be freely combined.　The optical system device provided with a first optical element 1 having periodically arranged linear concave lenses 11, a second optical element 2 having periodically arranged linear convex lenses 21 in a direction perpendicular to the concave lenses 11, and an irradiation unit 3 that irradiates light of wavelength λ from the first optical element 1 side. When a concave lens 11 and a convex lens 21 are arranged facing each other, m and n are natural numbers greater than or equal to 1, the focal length of the concave lens 11 is f1, the focal length of the convex lens 21 is f2, the pitch of the concave lens 11 is P1, and the pitch of the convex lens 21 is P2, the distance L1 between the irradiation unit 3 and a first focal plane 111 of the concave lens 11, and the distance L2 between the irradiation unit 3 and a second focal plane 211 of the convex lens 21 respectively satisfy formulas 1 and 2.

Description

Optical system device and optical element

[0001] The present invention relates to an optical system device and an optical element.

[0002] A three-dimensional measurement sensor using the time-of-flight (TOF) method is being adopted in mobile devices, vehicles, robots, etc. This measures the distance of an object from the time it takes for the light irradiated from a light source to be reflected back from the object. If the light from the light source is uniformly irradiated on a predetermined area of the object, the distance at each irradiated point can be measured and the three-dimensional structure of the object can be detected.

[0003] The above sensor system consists of a light irradiation unit that irradiates light on an object, a camera unit that detects the light reflected from each point of the object, and an arithmetic unit that calculates the distance of the object from the signal received by the camera.

[0004] Since the camera unit and the arithmetic unit can use existing CMOS imagers and CPUs, the unique part of the above system is the light irradiation unit consisting of a laser and an optical filter. In particular, a diffusion filter that shapes the beam by transmitting laser light through a microlens array and performs uniform irradiation in a controlled area on the object is a characteristic component of the above system.

[0005] For example, the present inventors have reported an optical system device and an optical element that can irradiate light with high contrast even when irradiating a non-circular dot pattern (for example, Patent Document 1).

[0006] International Publication Number WO2024 / 106359

[0007] However, the optical element has problems that peeling easily occurs at the boundary of the layers when dicing or when heat is applied. Also, since the first lens and the second lens are laminated, there is a problem that they cannot be freely combined. Therefore, an object of the present invention is to provide an optical system device and an optical element that have no problem of peeling and can freely combine the first lens and the second lens.

[0008] In order to achieve the above object, the optical system device of the present invention includes a first optical element having line-shaped concave lenses that transmit light with a wavelength λ and are arranged periodically, a second optical element arranged in a direction perpendicular to the concave lenses and having line-shaped convex lenses that transmit light with a wavelength λ and are arranged periodically, and an irradiation unit having a light source that irradiates light with a wavelength λ to the plurality of concave lenses and the plurality of convex lenses. The first optical element and the second optical element are arranged such that the concave lenses and the convex lenses face each other. The irradiation unit irradiates light from the side of the first optical element. Let m and n be natural numbers of 1 or more, the focal length of the concave lens be f １ , the focal length of the convex lens be f ２ , the pitch size of the concave lens be P １ , the pitch size of the convex lens be P ２ . Then, the distance L １ between the irradiation unit and the first focal plane of the concave lens, and the distance L ２ between the irradiation unit and the second focal plane of the convex lens satisfy the following formulas 1 and 2 [Formula 1] [Formula 2] and is characterized by this.

[0009] In this case, it is preferable that the distance between the first focal plane and the second focal plane of the first optical element and the second optical element is within 10 μm, and more preferably, the first focal plane and the second focal plane are at the same position.

[0010] Further, the first optical element and the second optical element preferably satisfy that the pitch P １ of the concave lens and the pitch P ２ of the convex lens satisfy mP １ ２ = nP ２ ２ .

[0011] Further, in the irradiation unit, the light sources are arranged in a square array, and the first optical element and the second optical element can be made to satisfy that the pitch P １ of the concave lens and the pitch P ２ of the convex lens satisfy P １ = P ２ .

[0012] Furthermore, the illumination unit has a hexagonal arrangement of light sources, and the first optical element and the second optical element are located at the pitch P of the concave lens. １ and the pitch P of the convex lens ２ ga 2P １ =√3P ２ or √3P １ = 2P ２ It is also possible to satisfy this requirement.

[0013] Also, distance L １ and L ２ However, see equations 3 and 4 below [Equation 3] [Formula 4] It is preferable to satisfy the following conditions.

[0014] Furthermore, it is preferable to include a spacer for adjusting the distance between the first optical element and the second optical element. For example, the spacer may consist of a first spacer integrally formed with the first optical element and a second spacer integrally formed with the second optical element and capable of fitting into the first spacer. In this case, it is preferable that the first spacer and the second spacer have a shape that allows them to fit together so that the first optical element and the second optical element do not move in the planar direction.

[0015] Furthermore, the optical element of the present invention comprises: a first optical element having a line-shaped concave lens that transmits light of wavelength λ and is periodically arranged; and a second optical element having a line-shaped convex lens that is arranged in a direction perpendicular to the concave lens, transmits light of wavelength λ and is periodically arranged, wherein the first optical element and the second optical element are arranged so that the concave lens and the convex lens face each other, and the distance between the first focal plane of the concave lens and the second focal plane of the convex lens is 10 μm or less.

[0016] In this case, m and n are natural numbers greater than or equal to 1, and the size of the pitch of the concave lens is P. １ The size of the pitch of the convex lens is P ２ Therefore, mP １ ２ = nP ２ ２ It is preferable to satisfy the following conditions.

[0017] Furthermore, it is preferable that the first focal plane and the second focal plane are in the same position.

[0018] Furthermore, it is preferable to include a spacer for adjusting the distance between the first optical element and the second optical element. For example, the spacer may consist of a first spacer integrally formed with the first optical element and a second spacer integrally formed with the second optical element and capable of fitting into the first spacer. In this case, it is preferable that the first spacer and the second spacer have a shape that allows them to fit together so that the first optical element and the second optical element do not move in the planar direction.

[0019] The optical system and optical elements of the present invention do not have the problem of delamination because the first optical element and the second optical element are separated. Furthermore, because they are separated, the first optical element and the second optical element can be freely combined.

[0020] This is a schematic cross-sectional view showing the optical system of the present invention. This is a perspective view showing the first optical element and the second optical element according to the present invention. This is a perspective view showing an optical element having a spacer according to the present invention. This is a diagram showing the orientation distribution in the far field of the irradiation unit used in the simulation. This is a projection view of the dot pattern of the optical system of the present invention. This is a schematic cross-sectional view showing the manufacturing method of the first optical element of the present invention. This is a schematic cross-sectional view showing the manufacturing method of the second optical element of the present invention.

[0021] The optical system of the present invention will be described below. As shown in Figure 1, the optical system of the present invention mainly consists of a first optical element 1, a second optical element 2, and an illumination unit 3.

[0022] As shown in Figure 2, the first optical element 1 has line-shaped concave lenses 11 that transmit light of wavelength λ and are arranged periodically. Furthermore, as shown in Figure 1(a), the concave lenses 11 have a focal length f on the second optical element 2 side. １ (f １ >0) It has a focal length that is far apart. In this specification, the focal length f １This refers to the distance between the lens surface furthest from the focal point and the focal point, as shown in Figure 1(a). In this specification, the direction of the line of the concave lens 11 is conveniently defined as the Y direction, as shown in Figure 2. The material of the first optical element 1 can be any material that can form a line-shaped concave lens 11 that transmits light of wavelength λ, and for example, resins such as silicone resins, epoxy resins, or acrylic resins can be used. Specifically, polydimethylsiloxane (PDMS) can be given as a material for the first optical element 1.

[0023] As shown in Figure 2, the second optical element 2 has line-shaped convex lenses 21 that transmit light of wavelength λ and are arranged periodically. Furthermore, as shown in Figure 2, the convex lenses 21 are arranged such that the direction of their lines is perpendicular to the direction of the lines of the concave lenses 11. Also, as shown in Figure 1(b), the convex lenses 21 have a focal length f on the first optical element 1 side. ２ (f ２ >0) It has a focal length that is far apart. In this specification, the focal length f ２ This refers to the distance between the focal point and the lens surface closest to the focal point, as shown in Figure 1(b). In this specification, for convenience, the direction of the line of the convex lens 21 is defined as the Y direction, perpendicular to the X direction, as shown in Figure 2. The material of the second optical element 2 can be any material that can form a line-shaped convex lens 21 that transmits light of wavelength λ, and for example, resins such as silicone resins, epoxy resins, or acrylic resins can be used. Specifically, polydimethylsiloxane (PDMS) can be given as a material for the second optical element 2.

[0024] The concave lens 11 and the convex lens 21 can have any shape as long as they can focus light in a linear shape; for example, lenticular lenses can be used. Furthermore, Fresnel lenses, DOE lenses, metalenses, etc., can also be used for the concave lens 11 and the convex lens 21, as long as they can focus light in a linear shape. Additionally, the concave lens 11 and the convex lens 21 may have an anti-reflective coating to prevent reflection of light from the illumination unit 3.

[0025] Furthermore, as shown in Figure 1(a), the first optical element 1 may have a base material 19 on the opposite side from the second optical element 2 for manufacturing reasons or other reasons. The base material 19 can be any material that transmits light of wavelength λ. Also, as shown in Figure 1(b), the second optical element 2 may have a base material 29 on the opposite side from the first optical element 1 for manufacturing reasons or other reasons. The base material 29 can be any material that transmits light of wavelength λ.

[0026] Furthermore, the medium between the first optical element 1 and the second optical element 2 can be any medium as long as it has a sufficient refractive index difference between it and the first optical element 1 and the second optical element 2. For example, a gas such as air can be used. Alternatively, the medium may be a resin or the like.

[0027] As shown in Figure 1, the irradiation unit 3 has a light source 7 that irradiates multiple concave lenses 11 and convex lenses 21 with light of wavelength λ. The irradiation unit 3 can be any type of light source 7 that can irradiate multiple concave lenses 11 and convex lenses 21 with light of wavelength λ. The irradiation unit 3 may also be a single light source or a multi-light source. Alternatively, a multi-light source may be created by passing light from a single light source through an aperture in which multiple pores are formed. When the irradiation unit 3 is composed of multiple light sources, it is preferable that the light sources 7 be formed on the same plane, as this allows for precise adjustment of the distance and angle between the first optical element 1 and the second optical element 2 and the irradiation unit 3. A specific example of the irradiation unit 3 is a VCSEL (Vertical Cavity Surface Emitting Laser) which can be expected to produce high output with low power. VCSELs include single-emitter VCSELs which have one light source 7 that can irradiate light in a direction perpendicular to the light-emitting surface, and multi-emitter VCSELs which have multiple light sources 7. Furthermore, it is preferable that a light-absorbing film is formed on parts other than the light source 7, as this prevents noise from being introduced due to reflected light.

[0028] When the illumination unit 3 has multiple light sources 7, even if the illumination unit 3 and the first optical element 1 and the second optical element 2 are relatively translated, it is necessary to arrange them so that the number of light sources 7 for each concave lens 11 of the first optical element 1 and the number of light sources 7 for each convex lens 21 of the second optical element 2 are the same in a plan view. Therefore, let j be a natural number of 1 or more, and set the size of the pitch of the concave lens 11 of the first optical element 1 to P. １ Therefore, the irradiation unit 3 has a pitch of the light source 7 with respect to the periodic direction of the concave lens 11, which is jpP １ or P １ The elements can be arranged regularly using / j. Similarly, if k is a natural number greater than or equal to 1, the pitch of the convex lens 21 can be set to P. ２ Therefore, the irradiation unit 3 sets the pitch of the light source 7 to kP with respect to the periodic direction of the convex lens 21 of the second optical element 2. ２ or P ２ You can arrange them regularly using / k.

[0029] Furthermore, when the light sources 7 of the illumination unit 3 are arranged in a square pattern, the pitch P of the concave lens 11 of the first optical element 1 is... １ and the pitch P of the convex lens 21 ２ P １ = P ２ This can be done. Also, if the light source 7 of the irradiation unit 3 is arranged in a hexagonal configuration, the pitch P of the concave lens 11 １ and the pitch P of the convex lens 21 ２ 2P １ =√3P ２ or √3P １ = 2P ２ It can be done this way.

[0030] [Positional relationship between the illumination unit and the first optical element 1 and the second optical element 2] As shown in Figure 1, the optical system is arranged such that the distance L between the illumination unit 3 and the first focal plane 111 of the concave lens 11 is... １ The distance L between the illumination unit 3 and the second focal plane 211 of the convex lens 21. ２ However, if the following equations α and β are satisfied, the incident light can be converted into a dot pattern with high contrast. Here, m and n are natural numbers greater than or equal to 1, and P １ P is the size of the pitch of the concave lens 11. ２ λ is the pitch size of the convex lens 21, λ is the wavelength of light incident from the irradiation unit 3, f１ The focal length of the concave lens 11 is f ２ is the focal length of the convex lens 21, and a, b, c, and d are coefficients indicating the allowable error. The first focal plane 111 is the plane perpendicular to the optical axis (z-direction) of the concave lens 11 and located at the focal point of the concave lens 11. The second focal plane 211 is the plane perpendicular to the optical axis (z-direction) of the convex lens 21 and located at the focal point of the convex lens 21. The concave lens 11 and the convex lens 21 are formed such that the first focal plane 111 and the second focal plane 211 are parallel. Also, distance L １ , L ２ This term represents the distance light travels in a vacuum in the same amount of time it travels through a medium (optical path length). If N is the refractive index of the medium and L is the actual distance, then it is expressed as the product NL. [Equation α] [Formula β]

[0031] Furthermore, the coefficient a in equation α is preferably small, such as a=1, a=0.5, a=0.3, and a=0.1. Similarly, the coefficient b is also preferably small, such as b=1, b=0.5, b=0.3, and b=0.1. Furthermore, the coefficient c in equation β is preferably small, such as c=1, c=0.5, c=0.3, and c=0.1. Similarly, the coefficient d is also preferably small, such as d=1, d=0.5, d=0.3, and d=0.1. When the coefficients of equations α and β are a=b=c=d=1, equations α and β become equations 1 and 2 below, respectively. [Equation 1] [Formula 2] It is designed to satisfy the following conditions.

[0032] More preferably, distance L １ and L ２ However, see equations 3 and 4 below [Equation 3] [Formula 4] It is better to satisfy the following conditions.

[0033] Furthermore, it is preferable that the distance between the first focal plane 111 and the second focal plane 211 of the first optical element 1 and the second optical element 2 is within 10 μm, as this makes it easier to simultaneously satisfy equations 1 and 2 or equations 3 and 4. More preferably, the first focal plane 111 and the second focal plane 211 are in the same position.

[0034] The distance between the first focal plane 111 and the second focal plane 211 can be adjusted in any way, but for example, a spacer 4 can be used to adjust the distance between the first optical element 1 and the second optical element 2. The spacer 4 can be made up of, for example, a first spacer 41 integrally formed with the first optical element 1 and a second spacer 42 integrally formed with the second optical element 2 and fittable into the first spacer 41, as shown in Figure 3. In this case, as shown in Figure 3(a), it is preferable that the first spacer 41 and the second spacer 42 are shaped so that they can be fitted together so that the first optical element 1 and the second optical element 2 do not move in the planar direction. Here, the planar direction means the direction in the XY plane (the direction perpendicular to the Z direction). The planar shape of the first spacer 41 and the second spacer 42 (shape in the XY plane) can be a trapezoid that is convex toward the center side of the first optical element 1 or the second optical element 2, as shown in Figure 3(a). Then, the first spacer 41 can be placed on both ends of the surface of the first optical element 1 where the concave lens 11 is located, and the second spacer 42 can be placed on both ends of the surface of the first optical element 2 where the convex lens 21 is located. The orientation of both the first spacer 41 and the second spacer 42 can be the same as the line direction of the concave lens 11 and the convex lens 21, or both can be orthogonal to the line direction. When the first spacer 41 and the second spacer 42 are fitted together, the lines of the convex lens 21 and the concave lens 11 can be automatically aligned perpendicular to each other.

[0035] Furthermore, when the distance between the first focal plane 111 and the second focal plane 211 is within 10 μm, the pitch P of the concave lens 11 is such that the first optical element 1 and the second optical element 2 are... １ and the pitch P of the convex lens 21 ２ ga mP １ ２ = nP ２ ２ It is preferable to satisfy the following conditions.

[0036] [Simulation] Next, using a first optical element 1 and a second optical element 2 in which the first focal plane 111 of the concave lens 11 and the second focal plane 211 of the convex lens 21 are in the same position, the distance L between the illumination unit 3 and the first focal plane 111 of the first optical element 1 is calculated. １ and the distance L from the second focal plane 211 of the second optical element 2. ２The light intensity distribution in the far field was simulated for the case where equations 3 and 4 below are satisfied. The optical simulation software BeamPROP (Synopsys) was used for the simulation. [Equation 3] [Formula 4]

[0037] The irradiation unit 3 is a single light source that emits light with a wavelength of 940 nm (λ = 0.94) and a light distribution as shown in Figure 4. The first optical element 1 and the second optical element 2 transmit light of wavelength λ. As shown in Figure 1(a), the first optical element 1 has a line-shaped concave lens 11 in the Y direction that is periodically arranged in the X direction, and the second optical element 2 has a line-shaped convex lens 21 in the X direction that is periodically arranged in the Y direction perpendicular to the X direction. As shown in Figure 1(a), the concave lens 11 has a refractive index of 1.53 and a focal length f １ The pitch is 5 μm, P １ is 32 μm (P １ =32), a periodically arranged arrangement was used with a depth of 5.6 μm. Furthermore, as shown in Figure 1(c), the convex lens 21 had a refractive index of 1.53 and a focal length f ２ Pitch P is 70 μm ２ is 32 μm (P ２ (=32) A periodically arranged arrangement with a height of 31.8 μm was used.

[0038] Figure 5 shows the projection images obtained from the simulation. Figure 5(a) is a planar projection at a distance of 1 m (4.8 m in the X direction, 2.0 m in the Y direction), and Figure 5(b) is a planar projection of a distant view. In both cases, the dots were very sharp. Furthermore, the contrast was 123.2, indicating that the contrast could be significantly improved compared to conventional methods.

[0039] [Manufacturing Method for Optical Elements] The manufacturing methods for the first optical element 1 and the second optical element 2 will be described below. The concave lens 11 of optical element 1 and the convex lens 21 of the second optical element 2 may be manufactured in any way, but for example, they can be manufactured using the imprint method.

[0040] First, the method for manufacturing the concave lens 11 will be described. The concave lens 11 is formed on the substrate 19 using a well-known technique such as the imprint method (concave lens formation step). For example, as shown in Figure 6(a), the material 11a for the concave lens 11 is coated onto the substrate 19 to a predetermined thickness using a well-known method such as a spin coater (first coating step). The material 11a can be any material that can form a concave lens 11 that transmits light of wavelength λ, and for example, resins such as silicone resins, epoxy resins, or acrylic resins can be used. Specifically, photocurable polydimethylsiloxane (PDMS) can be used as the material 11a. Next, as shown in Figure 6(b), a first mold 51 having a convex lens pattern in the shape of the inverted concave lens 11 is prepared, and the first lens pattern is transferred to the coated material 11a by applying pressure (first transfer step). The coated pattern is then cured by irradiating it with a UV light or the like (first curing step). Next, as shown in Figure 6(c), the first mold 51 can be released to form the concave lens 11 on the substrate 19. Although not shown, if a pattern for forming the first spacer 41 is also formed on the first mold 51, the first spacer 41 can also be formed integrally on the substrate 19.

[0041] Next, the manufacturing method of the convex lens 21 will be described. The convex lens 21 is formed on the substrate 29 using a well-known technique such as the imprint method (convex lens formation step). For example, as shown in Figure 7(a), the material 21a of the convex lens 21 is coated onto the substrate 29 to a predetermined thickness using a well-known method such as a spin coater (second coating step). The material 21a can be any material that can form a convex lens 21 that transmits light of wavelength λ, and for example, resins such as silicone resin, epoxy resin, or acrylic resin can be used. Specifically, photocurable polydimethylsiloxane (PDMS) can be used as the material 21a. Next, as shown in Figure 7(b), a second mold 52 having a convex lens pattern in the shape of the convex lens 21 inverted is prepared, and the convex lens pattern is transferred to the coated convex lens 21 material 21a by applying pressure (second transfer step). The coated pattern is then cured by irradiating it with UV light or the like (second curing step). Next, as shown in Figure 7(c), the second mold 52 can be released to form the concave lens 11 on the substrate 29. Although not shown, if a pattern for forming the second spacer 42 is also formed on the second mold 52, the second spacer 42 can also be formed integrally on the substrate 19.

[0042] Furthermore, by combining the first optical element 1 and the second optical element 2 manufactured in this manner, an optical element as shown in Figure 3(b) can be manufactured. Specifically, this optical element consists of a first optical element 1 having a line-shaped concave lens 11 that transmits light of wavelength λ and is arranged periodically, and a second optical element 2 having a line-shaped convex lens 21 that is arranged perpendicular to the concave lens 11, transmits light of wavelength λ, and is arranged periodically. The first optical element 1 and the second optical element 2 are arranged so that the concave lens 11 and the convex lens 21 face each other, and the distance between the first focal plane 111 of the concave lens 11 and the second focal plane 211 of the convex lens 21 is within 10 μm. Preferably, the first focal plane 111 and the second focal plane 211 are at the same position. Also, let m and n be natural numbers of 1 or more, and the pitch of the concave lens 11 be P １ The size of the pitch of the convex lens 21 is P ２ Therefore, mP１ ２ = nP ２ ２ It is better to manufacture it to meet the requirements.

[0043] In order to keep the distance between the first focal plane 111 and the second focal plane 121 within 10 μm, the spacing between the first optical element 1 and the second optical element 2 can be adjusted in any way, for example, by using a spacer 4. The spacer 4 can be one that consists of a first spacer 41 integrally formed with the first optical element 1 and a second spacer 42 integrally formed with the second optical element 2 and fitted into the first spacer 41, as shown in Figure 3. In this case, as shown in Figure 3(a), it is preferable that the first spacer 41 and the second spacer 42 are shaped so that they can be fitted together so that the first optical element 1 and the second optical element 2 do not move in the planar direction. Here, the planar direction means the direction in the XY plane (the direction perpendicular to the Z direction). The planar shape of the first spacer 41 and the second spacer 42 (shape in the XY plane) can be a trapezoid that is convex toward the center of the first optical element 1 or the second optical element 2, as shown in Figure 3(a). Then, the first spacer 41 is placed on both ends of the surface of the first optical element 1 where the concave lens 11 is located, and the second spacer 42 is placed on both ends of the surface of the first optical element 2 where the convex lens 21 is located. It is preferable that the orientation of both the first spacer 41 and the second spacer 42 be the same as the line direction of the concave lens 11 and the convex lens 21, or that both be manufactured in a direction perpendicular to the line direction. By fitting the first spacer 41 and the second spacer 42 together, the lines of the convex lens 21 and the concave lens 11 can be automatically aligned perpendicular to each other.

[0044] 1. First optical element 2. Second optical element 3. Irradiation unit 4. Spacer 7. Light source 11. Concave lens 11a. Material 19. Substrate 21. Convex lens 21a. Material 29. Substrate 41. First spacer 42. Second spacer 51. First mold 52. Second mold 110. Concave lens layer 111. First focal plane 210. Convex lens layer 211. Second focal plane

Claims

1. The optical element comprises: a first optical element having line-shaped concave lenses that transmit light of wavelength λ and are arranged periodically; a second optical element having line-shaped convex lenses arranged perpendicular to the concave lenses and that transmit light of wavelength λ and are arranged periodically; and an illumination unit having a light source that irradiates a plurality of the concave lenses and a plurality of the convex lenses with light of wavelength λ, wherein the first optical element and the second optical element are arranged so that the concave lenses and the convex lenses face each other, and the illumination unit irradiates light from the side of the first optical element, with m and n being natural numbers of 1 or more, and the focal length of the concave lens being f １ The focal length of the convex lens is f ２ The size of the pitch of the concave lens is P １ The size of the pitch of the convex lens is P ２ Therefore, the distance L between the irradiating portion and the first focal plane of the concave lens is １ , the distance L between the irradiating portion and the second focal plane of the convex lens ２ However, see the following equations 1 and 2 [Equation 1] [Formula 2] An optical system characterized by satisfying the following conditions.

2. The optical system according to claim 1, characterized in that the distance between the first focal plane and the second focal plane of the first optical element and the second optical element is 10 μm or less.

3. The first optical element and the second optical element have a pitch P of the concave lens １ and a pitch P of the convex lens ２ such that mP １ ２ = nP ２ ２ The optical system device according to claim 1 or 2, characterized in that it satisfies the above conditions.

4. The optical system according to claim 1 or 2, characterized in that the first optical element and the second optical element have the same focal plane and the same focal plane.

5. The illumination unit has a square arrangement of light sources, and the first optical element and the second optical element are arranged at the pitch P of the concave lens. １ and the pitch P of the convex lens ２ P １ = P ２ The optical system according to claim 1 or 2, characterized in that it satisfies the following conditions.

6. The illumination unit has a hexagonal arrangement of light sources, and the first optical element and the second optical element are located at the pitch P of the concave lens. １ and the pitch P of the convex lens ２ ga 2P １ =√3P ２ or √3P １ = 2P ２ The optical system according to claim 1 or 2, characterized in that it satisfies the following conditions.

7. Distance L １ and L ２ However, see equations 3 and 4 below [Equation 3] [Formula 4] The optical system according to claim 1 or 2, characterized in that it satisfies the following conditions.

8. The optical system according to claim 1 or 2, further comprising a spacer for adjusting the distance between the first optical element and the second optical element.

9. The optical system according to claim 8, characterized in that the spacer comprises a first spacer integrally formed with the first optical element and a second spacer integrally formed with the second optical element and capable of fitting into the first spacer.

10. The optical system according to claim 9, characterized in that the first spacer and the second spacer are shaped to fit together so that the first optical element and the second optical element do not move in the planar direction.

11. An optical element comprising: a first optical element having a line-shaped concave lens that transmits light of wavelength λ and is periodically arranged; and a second optical element having a line-shaped convex lens arranged in a direction perpendicular to the concave lens, which transmits light of wavelength λ and is periodically arranged, wherein the first optical element and the second optical element are arranged so that the concave lens and the convex lens face each other, and the distance between the first focal plane of the concave lens and the second focal plane of the convex lens is 10 μm or less.

12. Let m and n be natural numbers greater than or equal to 1, and let P be the size of the pitch of the concave lens. １ The size of the pitch of the convex lens is P ２ Therefore, mP １ ２ = nP ２ ２ The optical element according to claim 11, characterized in that it satisfies the following conditions.

13. The optical element according to claim 11 or 12, characterized in that the first focal plane and the second focal plane are in the same position.

14. The optical element according to claim 11 or 12, further comprising a spacer for adjusting the distance between the first optical element and the second optical element.

15. The optical element according to claim 14, characterized in that the spacer comprises a first spacer integrally formed with the first optical element and a second spacer integrally formed with the second optical element and capable of fitting into the first spacer.

16. The optical element according to claim 15, characterized in that the first spacer and the second spacer are shaped to fit together so that the first optical element and the second optical element do not move in the planar direction.

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