Optical system device

Abstract

The purpose of the present invention is to provide: an optical system device that provides a high contrast for a dot pattern even when light sources are arranged in a hexagonal pattern and lenses are square or of a similar shape; and an optical system device capable of shortening the distance between a lens and a light source.　Provided is an optical system device comprising: an optical element in which lenses, through which light having a wavelength of λ is transmitted and which each have a width of P in the x direction passing through the center of the optical axis and a width of (√3)P / 2 in the y direction, are arranged in a regular hexagonal pattern at a pitch of P in the x direction passing through the center of the optical axis; and an irradiation unit in which light sources for irradiating a plurality of the lenses with light having a wavelength of λ are arranged in a regular hexagonal pattern at a pitch of P in the x direction. When f represents the focal length of the lenses and n represents a natural number greater than or equal to 1, the distance L1 between the irradiation unit and the focal position of the optical element satisfies formula 1.

Description

optical system equipment

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

[0002] Three-dimensional measurement sensors using the time-of-flight (TOF) method are being adopted in mobile devices, cars, robots, etc. This method measures the distance to an object from the time it takes for light from a light source to be irradiated onto the object, reflected, and returned. If the light from the light source is irradiated uniformly over a specified 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 transmitter (Tx module) that irradiates light onto an object, and a receiver (Rx module) that detects light reflected from each point on the object. The transmitter is mainly composed of an irradiation unit that irradiates light and an optical element that controls and irradiates the light to a predetermined area. The receiver is mainly composed of a camera unit that receives light and a calculation unit that calculates the distance to the object from the signal received by the camera unit. Here, the camera unit and calculation unit of the receiver can use an existing CMOS imager and CPU, so the characteristic part of the above system is the transmitter.

[0004] The optical elements of the transmitter include, for example, a diffusion filter that transmits light from the irradiating unit, shapes the light, and irradiates a target within a predetermined range with uniform light. The diffusion filter is typically a microlens array with randomly arranged lenses.

[0005] On the other hand, TOF requires long-distance measurement, and the irradiated light must have sufficient intensity and contrast to enable such measurements. However, diffusion filters are not suitable for long-distance measurements because the irradiated light has a high uniformity, but the light intensity and contrast are low.

[0006] Therefore, as a transmitter that can save power and transmit a strong light signal, an optical system device is being considered that uses an optical element to control and irradiate the light of an irradiating section into a dot pattern, which is a distribution of multiple dot lights. A dot pattern has a lower resolution than a diffusion filter, but the light intensity and contrast of each dot are higher. An optical system device that irradiates a dot pattern includes an optical element with a regular arrangement of lenses at a predetermined pitch P, and an irradiating section arranged at a predetermined distance from the optical element. Here, the optical element and the irradiating section are defined by λ, where λ is the wavelength of the light from the light source, n is a natural number greater than or equal to 1, and L is the distance between the optical element and the light source of the irradiating section. ０ Then, they are arranged so as to satisfy the following formula A (for example, Patent Document 1).

[0007] WO 2021 / 229848

[0008] In recent years, there has been a demand for smaller and thinner optical devices. To achieve this, the distance L between the microlens and the light source must be ０ It is necessary to reduce the distance L ０ In order to reduce the value, it is sufficient to reduce the pitch P of the lenses of the optical element according to the formula A.

[0009] On the other hand, the lens pitch P is restricted by the light source pitch, and therefore the lens pitch depends on the light source pitch and arrangement. Conventional light sources use VCSELs (Vertical Cavity Surface Emitting Lasers), which are expected to produce high output with low power consumption. Hexagonal arrangements are the mainstream for VCSELs, while quadrangular arrangements are costly. Therefore, it is conceivable to use a hexagonal planar shape for the lens, but with a hexagonal planar shape, it is difficult to design the irradiated dot pattern to be square. Therefore, it is preferable to use a square or a shape similar to this for the planar shape of the lens.

[0010] In the case of a hexagonal array VCSEL light source and a square lens plane shape, there has been a conventional design in which the short side of the lens is set to the minimum pitch P of the light source and the long side is set to the second pitch (√3)P (see Figure 57 in Reference 1). However, in this case, in order for both the minimum pitch P and the second pitch (√3)P to satisfy formula A, it is necessary to make n in formula A a multiple of 3. Then, the distance L ０ This increases the size and thickness of the optical system, which becomes an obstacle to making the optical system smaller and thinner.

[0011] Therefore, the present invention aims to provide an optical system device that has a high contrast dot pattern even when the light sources are arranged in a hexagonal pattern and the lens plane is rectangular or has a shape similar to that, and that can reduce the distance between the lens and the light source.

[0012] In order to achieve the above object, the optical system device of the present invention comprises an optical element in which lenses that transmit light of wavelength λ and have a width P in the x direction passing through the center of the optical axis and a width (√3)P / 2 in the y direction are arranged in a regular hexagonal array with a pitch P in the x direction about the center of the optical axis, and an irradiation unit in which light sources that irradiate a plurality of the lenses with light of wavelength λ are arranged in a regular hexagonal array with a pitch P in the x direction, and １ is expressed by the following formula 1 The present invention is characterized in that:

[0013] In this case, the optical element preferably has a lens whose xy plane has a quadrangular shape, for example, a rectangular shape.

[0014] In addition, the distance L １ However, the following formula 2 It is preferable to satisfy the following.

[0015] In addition, the distance L １ However, the following formula 3 It is preferable to satisfy the following.

[0016] In addition, the distance L １ is expressed by the following formula 4 It is preferable to satisfy the following.

[0017] The optical system device of the present invention can provide an optical system device that has high contrast dot patterns even when the light sources are arranged in a hexagonal array and the lenses are rectangular or have a shape similar thereto, and can also provide an optical system device that can shorten the distance between the lens and the light source.

[0018] FIG. 1 is a schematic cross-sectional view showing an optical system device of the present invention. FIG. 2 is a plan view showing an optical system device of the present invention. FIG. 3 is a plan view showing an optical system device of the present invention. FIG. 4 is a plan view showing an optical system device of the present invention. FIG. 5 is a diagram showing a light distribution in the far field of an irradiation unit used in a simulation. (a) A schematic plan view of the optical system device of the present invention, and (b) a projection view thereof, in simulation 1. (a) A schematic plan view of a conventional optical system device, and (b) a projection view thereof, in simulation 1. (a) A schematic plan view of the optical system device of the present invention, and (b) a projection view thereof, in simulation 2. (a) A schematic plan view of the conventional optical system device, and (b) a projection view thereof, in simulation 2.

[0019] The optical system of the present invention will be described below. As shown in Figure 1, the optical system of the present invention is mainly composed of an optical element 1 having periodic lenses 11 and an irradiation unit 2 having a periodic light source that irradiates light of wavelength λ.

[0020] The optical element 1 transmits light of wavelength λ and has lenses with a width P in the x direction passing through the optical axis center and a width (√3)P / 2 in the y direction, arranged in a regular hexagonal array with a pitch P in the x direction about the optical axis center. The regular hexagonal array of lenses means, in other words, that the lenses are periodically arranged with a pitch P in the x direction and a pitch (√3)P / 2 in the y direction perpendicular to the x direction, as shown in FIG. 2 , with adjacent rows in the x direction being shifted by P / 2 from each other. For convenience, in this specification, the direction of the optical axis of the optical element 1 is referred to as the z direction, and the x direction, y direction, and z direction are assumed to be perpendicular to each other. The optical axis center refers to the intersection of the xy plane and the optical axis.

[0021] The lens 11 has a focal point at a predetermined distance f (f>0) from the lens 11. In this specification, the focal length means the distance between the focal point and the lens surface closest to the focal point, as shown in Fig. 1. It is preferable that the focal point of the lens 11 is located on the irradiation side of the lens 11.

[0022] The shape of the lens 11 can be freely designed to match the dot pattern. For example, the shape of the lens 11 can be a spherical lens or an aspherical lens. The shape of the lens 11 can also be a convex lens or a concave lens. The lens 11 can be any lens that functions as a lens, and for example, a Fresnel lens, a DOE lens, a metalens, or the like can be used.

[0023] Furthermore, the shape of the xy plane of the lenses 11 (hereinafter referred to as the planar shape) may be any shape as long as the optical axis centers of the lenses 11 are arranged in a regular hexagonal array at a pitch P in the x direction. For example, as shown in Figure 2, the planar shape of the lenses 11 may be a square or a shape similar thereto. Furthermore, when the planar shape of the lenses 11 is a square, a rectangle is preferable, but it is also possible to make them a parallelogram or a rhombus as shown in Figures 3 and 4. Furthermore, shapes similar to a square include those in which the sides of the square have a wave shape such as a sine wave, a rectangular wave, a triangular wave, or a sawtooth wave, as shown in Figure 5.

[0024] Furthermore, the optical element 1 may be made of any material that can form a lens that transmits light of wavelength λ, such as a resin such as polydimethylsiloxane (PDMS) or glass. The optical element 1 may be manufactured by any method that can mold the lens 11, such as an imprint method or injection molding.

[0025] The irradiation unit 2 has light sources 20 that irradiate multiple lenses 11 with light of wavelength λ, arranged in a regular hexagonal array at a pitch P in the x direction. The irradiation unit 2 and the optical element 1 are preferably arranged so that the optical axis direction of the light sources 20 of the irradiation unit 2 coincides with the optical axis direction of the lenses 11 of the optical element 1. The light sources 20 may be any type that can irradiate multiple lenses 11 with light of wavelength λ. A specific example of the irradiation unit 2 is a VCSEL (Vertical Cavity Surface Emitting Laser), which is expected to achieve high output with low power consumption. A VCSEL has multiple light sources 20 that can irradiate light in a direction perpendicular to the light-emitting surface.

[0026] [Positional Relationship Between Irradiation Unit and Optical Element] As shown in FIG. 1, the distance L between the irradiation unit 2 and the focal plane of the optical element 1 is １ can convert incident light into a dot pattern with high contrast when the following formula α is satisfied. Here, n is a natural number equal to or greater than 1, P is the pitch of the lens in the x direction, λ is the wavelength of light incident from the irradiation unit 2, f is the focal length of the lens 11, and a and b are coefficients indicating the allowable error. The focal plane means a plane that is perpendicular to the optical axis (z direction) of the lens 11 and is located at the focal position of the lens 11. In addition, the distance L １ means the distance (optical path length) that light travels in a vacuum in the same time as it travels through a medium, and is expressed as the product NL, where N is the refractive index of the medium and L is the actual distance.

[0027] Here, the smaller the values ​​of the coefficients a and b in formula α are, the more preferable they are, i.e., 1, 0.5, 0.3, and 0.1. When the coefficients of formula α are a=b=1, formula α becomes formula 1 below.

[0028] In addition, the distance L １ can most effectively enhance the light when the following formula 2 is satisfied, where a=b=0.

[0029] In addition, the smaller the value of n in the formula α, the smaller the distance L between the irradiation unit 2 and the focal plane of the optical element 1. １ becomes small, and when n=1, the following equation β is obtained.

[0030] Here, the smaller the values ​​of the coefficients a and b in formula β are, the more preferable they are, i.e., 1, 0.5, 0.3, and 0.1. When the coefficients of formula β are a=b=1, formula β becomes formula 3 below.

[0031] In addition, the distance L １ is the shortest distance between the irradiation unit 2 and the focal plane of the optical element 1 when the light can be most reinforced when the following formula 4 is satisfied, where a=b=0.

[0032] If the pitch P is too small compared to the wavelength λ of the light from the light source 20, diffraction becomes difficult to occur. Therefore, as long as the light distribution angle of the light source 20 includes a sufficient number of lenses 11 to cause diffraction, the pitch P should be sufficiently larger than the wavelength λ of the light from the light source 20, for example, 5 times or more, and preferably 10 times or more.

[0033] [Simulation 1] A simulation was performed for the optical system device of the present invention and a conventional optical system device as a comparative example. In this simulation, the same irradiation unit was used for both optical system devices. As shown in Figures 7(a) and 8(a), the irradiation unit has a plurality of light sources 20A arranged in a regular hexagonal array at a pitch P in the x direction. The light sources 20A of the irradiation unit irradiate light with a pitch P of 20 μm (P=20), a wavelength of 940 nm (λ=0.94), and a batwing light distribution as shown in Figure 6. The distance L between the irradiation unit and the focal position of the optical element was １ The following formula 2 was used. The simulation was performed using optical simulation software BeamPROP (manufactured by Synopsys).

[0034] As shown in Figure 7(a), the optical element 1A of the optical system device of the present invention was an optical element in which lenses 11A were arranged in a regular hexagonal array with a pitch P around the optical axis in the x direction. The lenses 11A of the optical element 1A transmitted light of wavelength λ (λ = 0.94) and had a width of 20 μm in the x direction and a width of 10√3 μm in the y direction passing through the optical axis. The lenses 11A also had a refractive index of 1.5 and a focal length f of 10 μm.

[0035] The distance L between the irradiation unit and the focal position 9 of the optical element 1A１ is the distance 426 μm [L １ = 2 x 20 ２ / (2×0.94)=426).

[0036] 7B shows an image projected 1 m ahead from the optical element 1A. The average contrast of each dot at this time was 14.40.

[0037] As shown in Figure 8(a), the optical element 1B used in the conventional optical system device was a square array of lenses 11B arranged around the optical axis at a pitch P in the x direction and √3P in the y direction. The lenses 11B of the optical element 1B transmit light of wavelength λ (λ = 0.94) and have a width of 20 μm in the x direction and 20√3 μm in the y direction passing through the optical axis. The lenses 11B also have a refractive index of 1.5 and a focal length f of 12 μm.

[0038] The distance L between the irradiation unit and the focal position 9 of the optical element 1B １ is the distance 426 μm [L １ = 2 x 20 ２ / (2×0.94)=426).

[0039] 8B shows an image projected 1 m ahead from the optical element 1B. The average contrast of each dot in this case was 6.62.

[0040] When comparing the optical system of the present invention with the conventional optical system, １ Although the average contrast is the same at 426 μm, the optical system of the present invention has a higher average contrast than the conventional optical system, and it can be seen that the dots in the projected image are clearer.

[0041] [Simulation 2] Next, a simulation was performed on the optical system device of the present invention and a conventional optical system device as a comparative example. In this simulation, the distance between the irradiation unit and the focal position of the optical element was the same in both optical system devices. Also, the distance L between the irradiation unit and the focal position of the optical element １ The following formula 2 was used. The simulation was performed using optical simulation software BeamPROP (manufactured by Synopsys).

[0042] As shown in Fig. 9(a), the irradiation section of the optical system device of the present invention used a plurality of light sources 20B arranged in a regular hexagonal array in the x direction at a pitch P. The light sources 20B of the irradiation section emitted light with a pitch P of 20√3 µm (P = 20√3) and a wavelength of 940 nm (λ = 0.94), with a batwing light distribution as shown in Fig. 6.

[0043] As shown in Figure 9(a), the optical element 1C of the optical system device of the present invention uses lenses 11C arranged in a regular hexagonal array with a pitch P around the optical axis in the x direction. Lenses 11C of the optical element 1C transmit light of wavelength λ (λ = 0.94) and have a width of 20√3 μm in the x direction and a width of 30 μm in the y direction passing through the optical axis. Lenses 11C have a refractive index of 1.5 and a focal length f of 10 μm.

[0044] The distance L between the irradiation unit and the focal position 9 of the optical element 1C １ is the distance 1277 μm [L １ = 2 × (20√3) ２ / (2×0.94)=1277).

[0045] 9B shows an image projected 1 m ahead from the optical element 1C. The average contrast of each dot at this time was 41.96.

[0046] As shown in Fig. 10(a), the irradiation section of the conventional optical system device used a plurality of light sources 20A arranged in a regular hexagonal array in the x direction at a pitch P. The light sources 20A of the irradiation section emitted light with a pitch P of 20 µm (P = 20) and a wavelength of 940 nm (λ = 0.94), with a batwing light distribution as shown in Fig. 6.

[0047] 10(a), the optical element 1B of the conventional optical system device was configured with lenses 11B arranged in a square array with a pitch P in the x direction and √3P in the y direction around the optical axis center. The lenses 11B of the optical element 1B transmit light of wavelength λ (λ=0.94) and have a width of 20 μm in the x direction and 20√3 μm in the y direction passing through the optical axis center. The refractive index of the lenses 11B was 1.5 and the focal length f was 12 μm.

[0048] The distance L between the irradiation unit 2 and the focal position 9 of the optical element 1B １ is the distance when n = 6 in the above formula 2, which is 1277 μm [L １ = 6 x 20 ２ / (2×0.94)=1277).

[0049] 10B shows an image projected 1 m ahead from the optical element 1B. The average contrast of each dot in this case was 28.61.

[0050] When comparing the optical system of the present invention with the conventional optical system, １ Although the average contrast is the same at 1277 μm, the optical system of the present invention has a higher average contrast than the conventional optical system, and it can be seen that the dots in the projected image are clearer.

[0051] 1, 1A, 1B, 1C Optical element 2 Irradiation unit 9 Focal position 10 Substrate 11 Lens 20 Light source 51 Mold

Claims

1. An optical element is provided in which lenses that transmit light of wavelength λ and have a width P in the x direction passing through the optical axis center and a width (√3)P / 2 in the y direction are arranged in a regular hexagonal array with a pitch P in the x direction around the optical axis center, and an irradiation unit in which light sources that irradiate multiple lenses with light of wavelength λ are arranged in a regular hexagonal array with a pitch P in the x direction, where f is the focal length of the lens and n is a natural number greater than or equal to 1, and the distance L between the irradiation unit and the focal position of the optical element is １ is expressed by the following formula 1 An optical system device characterized by satisfying the above.

2. The optical system according to claim 1, wherein the optical element has a lens whose xy plane has a rectangular shape.

3. The optical system according to claim 1, wherein the optical element has a lens whose xy plane has a rectangular shape.

4. The distance L １ However, the following formula 2 4. The optical system according to claim 1, wherein the following is satisfied:

5. The distance L １ However, the following formula 3 4. The optical system according to claim 1, wherein the following is satisfied:

6. The distance L １ is expressed by the following formula 4 4. The optical system according to claim 1, wherein the following is satisfied:

Images