WO2017043063A1

WO2017043063A1 - Diffusion plate and imaging device provided with same

Info

Publication number: WO2017043063A1
Application number: PCT/JP2016/004018
Authority: WO
Inventors: 拓巳井場
Original assignee: パナソニックＩｐマネジメント株式会社
Priority date: 2015-09-10
Filing date: 2016-09-02
Publication date: 2017-03-16
Also published as: JP2017054017A

Abstract

Apexes (310) of lenses (31) are positioned to be shifted from base positions (4) positioned virtually in row and column directions, and the base positions (4) include a plurality of grid points (40) as reference positions for the apexes (310) of the lenses (31), first grid lines (41) linking two of the grid points (40) adjacent in the row direction, and second grid lines (42) linking two of the grid points (40) in the column direction. The directions of the first and the second grid lines (41, 42) match with the radial directions of the beam diameters of light in a first and a second direction, the first grid lines (41) are shorter than the beam diameter in the first direction, and the second grid lines (42) are shorter than the beam diameter in the second direction. As a consequence thereof, the interference fringe and irregularities in light distribution are reduced, and a highly uniform diffusion plate (3) is realized.

Description

Diffusion plate and imaging device provided with diffusion plate

The present invention relates to a diffusing plate for diffusing and irradiating a subject with laser light within an angle of view, and an imaging apparatus including the diffusing plate.

Conventionally, in an imaging apparatus, a diffusion plate that diffuses incident light uniformly is used in a lens array formed by arranging a large number of lenses adjacent to each other.

In particular, when coherent light having a uniform phase, such as a laser diode, is incident on a lens array in which a plurality of lenses are regularly arranged, the light passing through each lens causes interference due to diffraction. Therefore, interference fringes are generated on the diffusion plate, and the uniformity of light is impaired.

Therefore, in order to prevent the occurrence of interference fringes, a diffusion plate having the following configuration has been proposed (see, for example, Patent Document 1 and Patent Document 2).

The diffusing plate of Patent Document 1 randomly arranges two or more kinds of lenses having different curved surfaces in a two-dimensional manner. As a result, a desired diffusion angle and uniform diffused light intensity are obtained.

Further, the diffusion plate of Patent Document 2 includes a lens array having a basic arrangement in which a plurality of lenses are arranged so that the vertex intervals of a plurality of adjacent lenses are all equal. Then, the vertices of the plurality of lenses are arranged so as to be randomly located in a circle having a radius of 0.5 L (L: lens vertex interval) or less centered on the position of the vertex in the basic arrangement. Thereby, the influence of the diffracted light peculiar to the laser beam caused by the periodic regular arrangement of the lenses is reduced.

In other words, the diffuser plate of Patent Document 1 randomizes two or more types of lenses having different curved surfaces in a two-dimensional manner without defining the relationship between the beam diameter and the basic arrangement of the lens and the shift amount of the vertex position of the lens. Is arranged. On the other hand, the diffusion plate of Patent Document 2 is arranged such that the vertices of a plurality of lenses are randomly located in a circle having a radius of 0.5 L or less centered on the position of the vertex in the basic arrangement. This reduces the occurrence of light unevenness due to interference fringes.

However, none of the diffusion plates disclosed above can sufficiently reduce uneven light distribution within a desired irradiation range. That is, when the light from the light source is incident on the diffusion plate, the unevenness in the light distribution due to the non-uniformity of the light source cannot be sufficiently reduced.

Further, the diffusion plate disclosed in Patent Document 1 uses a lens having two or more different curved surfaces, that is, a lens having two or more different vertex positions that are not on the same plane. Therefore, the processing difficulty of the lens is high and the processing is difficult.

JP 2014-203032 A JP 2007-108400 A

The present invention provides a diffusion plate that can reduce light unevenness due to interference fringes and unevenness in light distribution, and an imaging device including the diffusion plate.

That is, the diffusion plate of the present invention includes a lens array in which a plurality of lenses are arranged adjacent to each other on a plane based on a basic arrangement, and the vertex positions of the plurality of lenses are virtually arranged in the row direction and the column direction. Arranged at random from the basic layout. The basic arrangement includes a plurality of lattice points that are reference positions of the vertices of a plurality of lenses, a first lattice line that connects two lattice points adjacent in the row direction among the plurality of lattice points, and a first lattice line And a second grid line connecting two grid points adjacent in the column direction among the plurality of grid points. Further, the direction of the first grating line is aligned with the radial direction of the beam diameter in the first direction of the incident light, and the direction of the second grating line is the radial direction of the beam diameter in the second direction of the incident light. The length of the first grating line is set shorter than the length of the beam diameter in the first direction of the incident light, and the length of the second grating line is set in the second direction of the incident light. It is set shorter than the length of the beam diameter. The vertices of the plurality of lenses are arranged at random shifts from the respective lattice points.

According to this configuration, the vertex positions of the plurality of lenses are arranged at random shifts from the positions of the regularly arranged grid points. That is, in the lens array, based on the beam diameter, the basic arrangement of the plurality of lenses in the lens array and the shift amount of the vertex positions of the plurality of lenses with respect to the plurality of lattice points of the basic arrangement are set.

The length of the first grid line (distance between grid points in the row direction), or the length of the beam diameter in the first direction at the time of incidence and the length in the radial direction of the beam diameter in the second direction, When the length of the two grid lines (distance between grid points in the column direction) is long, the irradiation light becomes non-uniform due to the non-uniformity of the light source.

Therefore, the length of the first grid line or the second grid line is made shorter than the length of the beam diameter in the first direction and the length of the beam diameter in the second direction at the time of incidence. Thereby, the interference fringes between the light rays emitted from the openings of the respective lenses can be reduced. Furthermore, unevenness in light distribution within a desired irradiation range can be reduced and uniformity can be improved. That is, light unevenness due to interference fringes and light distribution unevenness due to non-uniformity when light from the light source enters the diffusion plate can be reduced. As a result, it is possible to provide a diffusion plate that can diffuse incident light with high uniformity.

Further, an imaging apparatus of the present invention includes the diffusion plate. Thereby, it is possible to provide an imaging device capable of photographing a subject with uniform diffused light.

FIG. 1 is a schematic diagram illustrating an imaging apparatus according to an embodiment of the present invention. FIG. 2 is an enlarged view showing a part of the diffusion plate according to the imaging apparatus of the embodiment. FIG. 3 shows the result of the simulated Example 1 in the case where the length of the grid line of the basic arrangement (distance between adjacent grid points) is set based on a predetermined length of the beam diameter of incident light. FIG. FIG. 4 is a diagram illustrating the results of the simulated Example 1 in the case where the lengths of the grid lines of the basic arrangement are set based on predetermined lengths having different beam diameters of incident light. FIG. 5 shows the result of simulated Example 1 in the case where the length of the grid line of the basic arrangement (distance between adjacent grid points) is set based on predetermined lengths with different beam diameters of incident light. FIG. FIG. 6 is a diagram illustrating a result of simulation of Example 1 in the case where the lengths of the grid lines of the basic arrangement are set based on predetermined lengths having different beam diameters of incident light. FIG. 7 is a diagram illustrating the results of a simulated example 1 in the case where the lengths of the lattice lines in the basic arrangement are set based on predetermined lengths having different beam diameters of incident light. FIG. 8 is a diagram illustrating an arrangement of Example 2 in which the vertex positions of the lenses with respect to the lattice points of the basic arrangement are shifted by a predetermined amount in the row direction and the column direction. FIG. 9 is a diagram showing the results of Example 2 in which the uniformity of light distribution in a range corresponding to the angle of view is simulated when the vertex position of the lens is shifted with respect to the lattice points of the basic arrangement shown in FIG. is there. FIG. 10 is a diagram illustrating an arrangement of Example 2 in which the vertex positions of the lenses with respect to the lattice points of the basic arrangement are shifted by a predetermined amount different in the row direction and the column direction. FIG. 11 is a diagram showing the results of Example 2 in which the uniformity of light distribution in a range corresponding to the angle of view is simulated when the vertex position of the lens is shifted with respect to the lattice points of the basic arrangement shown in FIG. is there. FIG. 12 is a diagram illustrating an arrangement of Example 2 in which the vertex positions of the lenses with respect to the lattice points of the basic arrangement are shifted by a predetermined amount different in the row direction and the column direction. FIG. 13 is a diagram showing the results of Example 2 in which the uniformity of light distribution in a range corresponding to the angle of view is simulated when the vertex position of the lens is shifted with respect to the lattice points of the basic arrangement shown in FIG. is there. FIG. 14 is a diagram illustrating an arrangement of Example 2 in which the vertex positions of the lenses with respect to the lattice points of the basic arrangement are shifted by a predetermined amount different in the row direction and the column direction. FIG. 15 is a diagram showing the results of Example 2 in which the uniformity of light distribution in a range corresponding to the angle of view is simulated when the vertex position of the lens is shifted with respect to the lattice points of the basic arrangement shown in FIG. is there. FIG. 16 is a diagram illustrating an arrangement of Example 2 in which the vertex positions of the lenses with respect to the lattice points of the basic arrangement are shifted by a predetermined amount different in the row direction and the column direction. FIG. 17 is a diagram showing the results of Example 2 in which the uniformity of light distribution in a range corresponding to the angle of view is simulated when the position of the apex of the lens is shifted with respect to the lattice point of the basic arrangement shown in FIG. It is.

Hereinafter, a diffusion plate and an imaging apparatus including the diffusion plate according to an embodiment of the present invention will be described with reference to the drawings.

(Embodiment)
Hereinafter, a diffusion plate and an imaging device including the diffusion plate according to the present embodiment will be described with reference to FIG.

FIG. 1 is a schematic diagram showing an imaging apparatus according to the present embodiment.

As shown in FIG. 1, the imaging device 1 of the present embodiment includes at least a light source 2, a diffusion plate 3, a camera unit (not shown), and the like.

The light source 2 is composed of a semiconductor laser diode, for example, and irradiates the subject with light within a desired range. The diffusion plate 3 diffuses the light beam emitted from the light source 2 and converts it into diffused light having a predetermined diffusion angle and uniform light intensity. The camera unit receives reflected light from the subject and images it.

It should be noted that the semiconductor laser diode that is the light source 2 of the present embodiment has a characteristic that the shape in the radial direction of the beam that is the irradiation light is substantially elliptical (including elliptical). Therefore, in the following description, the beam diameter in the first direction is the major axis of the ellipse, and the beam diameter in the second direction is the minor axis of the ellipse.

Further, the diffusion plate 3 of the present embodiment is composed of, for example, a diffusion plate of a distance image camera of the TOF (Time Of Flight) method. Note that the range image camera of the TOF method first irradiates a subject with a laser beam diffusely within an angle of view. Next, the reflected light from the subject is received by a two-dimensional image sensor, and the time is measured. And it is a camera which calculates the distance to a to-be-photographed object from the flight time of light, and produces a three-dimensional distance distribution image.

Next, the configuration of the diffusion plate 3 of the present embodiment will be described with reference to FIG.

FIG. 2 is an enlarged view showing a part of the diffusion plate according to the imaging apparatus of the embodiment.

As shown in FIG. 2, the diffusing plate 3 includes a lens array 30 in which a plurality of lenses 31 are arranged adjacent to each other on a plane based on a grid-like basic arrangement 4 indicated by broken lines.

Hereinafter, the basic arrangement 4 will be described in detail.

The basic arrangement 4 is virtually arranged in a grid in the row direction and the column direction. The basic arrangement 4 includes a plurality of lattice points 40, a first lattice line 41, a second lattice line 42, and a lattice 43 having a predetermined shape. The plurality of lattice points 40 are provided at the intersections of the first lattice lines 41 and the second lattice lines 42 that extend in the row direction and the column direction, and the respective positions of the vertices 310 of the plurality of lenses 31 that constitute the lens array. It becomes the reference position. The first grid line 41 connects two

grid points

40, 40 adjacent in the row direction among the plurality of grid points 40. The second grid line 42 is orthogonal to the first grid line 41 and connects two

grid points

40, 40 adjacent to each other in the column direction among the plurality of grid points 40. The lattice 43 is formed of, for example, a right-angled square region surrounded by a pair of first lattice lines 41 arranged in parallel and a pair of second lattice lines 42 arranged in parallel.

The first lattice line 41 is connected in a direction that matches the radial direction of the beam diameter 50 in the first direction of the light 5 incident on the diffusion plate 3 shown in FIG.

The second grid line 42 is connected in a direction that matches the radial direction of the beam diameter 51 in the second direction of the light 5 incident on the diffusion plate 3 shown in FIG.

The length of the first grid line 41 is set to be shorter than the length of the beam diameter 50 in the first direction of the light 5 incident on the diffusion plate 3.

The length of the second grating line 42 is set to be shorter than the length of the beam diameter 51 in the second direction of the light incident on the diffusion plate 3.

Further, the vertex positions of the plurality of lenses 31 are randomly shifted from the respective lattice points 40 of the corresponding basic arrangement 4.

At this time, in the present embodiment, the length of the first lattice line 41 is set to 0 or more and 1/5 or less with respect to the beam diameter 50 in the first direction, for example. Note that the length of the first grid line 41 of 0 (zero) corresponds to the case where the first grid line 41 is not shifted. The length of the second grid line 42 is set to, for example, 0 or more and 1/5 or less with respect to the beam diameter 51 in the second direction. Note that the length of the second grid line 42 is 0 (zero), which corresponds to the case where the second grid line 42 is not shifted.

Further, in the present embodiment, the vertices 310 of the plurality of lenses 31 are randomly shifted from the plurality of lattice points 40 of the corresponding basic arrangement 4 on the basis of a shift amount determined by assigning a predetermined shift amount. Arranged.

Specifically, the shift amount in the row direction of the vertices 310 of the plurality of lenses 31 with respect to the plurality of lattice points 40 of the basic arrangement 4 is within a range of 1/5 to 1/15 of the length of the first lattice line 41. Set to Similarly, the shift amount in the column direction of the vertices 310 of the plurality of lenses 31 with respect to the plurality of lattice points 40 of the basic arrangement 4 is set within a range of 1/5 to 1/15 of the length of the second lattice line 42. Is done.

Next, a procedure for randomly shifting the positions of the apexes 310 of the plurality of lenses 31 described above will be described with reference to FIG.

In the following description, the length of the first grid line 41 within the range of 1/5 to 1/15 and the length shifted from the grid point 40 will be described as “shift amount Ra1”. Similarly, the length of the second grid line 42 within the range of 1/5 to 1/15 and the length shifted from the grid point 40 will be described as “shift amount Ra2”.

First, a procedure for shifting the position of the apex 310 of the lens 31 in the radial direction of the beam diameter 50 in the first direction will be described.

In this case, first, any one of “0 (no deviation)”, “+ Ra1”, “−Ra1” along the radial direction of the beam diameter 50 in the first direction with respect to each of the lattice points 40 of the basic arrangement 4. Is assigned to the apex 310 of each lens 31 as the actual shift amount in the first direction. Note that the above “+” indicates a case of deviation from the corresponding lattice point 40 in the right direction in FIG. 2 and “−” in the left direction in FIG.

The specific allocation method (variation method) will be described below.

First, the maximum absolute value of the shift amount Ra1 is set as “maximum shift amount Ra1max”. Then, after assigning the shift amount Ra1, a statistical distribution of the actual shift amount of the position of the vertex 310 of each lens 31 with respect to the lattice point 40 is taken. At this time, a numerical value of the shift amount Ra1 is assigned to each lattice point 40 so that a value of 1 / 2.5 or more of “Ra1max” of the statistical distribution becomes a normal distribution with a standard deviation of 1σ. . As a result, the position of the apex 310 of the lens 31 is shifted to vary the actual shift amount in the first direction.

Next, a procedure for shifting the position of the apex 310 of the lens 31 in the radial direction of the beam diameter 51 in the second direction will be described.

In this case, first, any one of “0 (no deviation)”, “+ Ra2”, “−Ra2” along the radial direction of the beam diameter in the second direction with respect to each of the lattice points 40 of the basic arrangement 4. Is assigned to the apex 310 of each lens 31 as the actual shift amount in the second direction. Note that the above “+” indicates an upward direction in FIG. 2, and “−” indicates a downward direction in FIG.

The specific allocation method (variation method) will be described below.

First, the maximum absolute value of the shift amount Ra2 is defined as “maximum shift amount Ra2max”. Then, after assigning the shift amount Ra2, a statistical distribution of the actual shift amount of the position of the vertex 310 of each lens 31 with respect to the lattice point 40 is taken. At this time, a numerical value of the shift amount Ra2 is assigned to each lattice point 40 so that a value of 1 / 2.5 or more of “Ra2max” of the statistical distribution becomes a normal distribution with a standard deviation of 1σ. . As a result, the position of the vertex 310 of the lens 31 is shifted to vary the actual shift amount in the second direction.

As described above, the positions of the vertices 310 of the plurality of lenses 31 are randomly shifted from the lattice points 40 of the basic arrangement 4 to be varied.

Specifically, as shown in FIG. 2, for example, the shift amount of the apex 310a of the lens 31 is (0, 0). The shift amount of the apex 310b of the lens 31 is (+ Ra1, + Ra2). The shift amount of the apex 310c of the lens 31 is (+ Ra1, 0). Further, the shift amount of the vertex 310d of the lens 31 is (−Ra1, −Ra2).

The reason why the shift amount varies with a standard deviation of a value of 1 / 2.5 or more of the maximum shift amount is that interference below the lower limit value 1 / 2.5 affects measurement accuracy such as distance. This is because fringes are generated on the intensity distribution. For this reason, it is preferable that the standard deviation is 1 / 2.5 or more of the maximum shift amount.

Further, in the present embodiment, the plurality of lenses 31 are configured by lenses having substantially the same (including the same) radius of curvature. Further, the positions of the apexes 310 of the plurality of lenses 31 in the lens length (thickness) direction are assumed to be substantially on the same plane (including the same plane). In addition, the position in the length (thickness) direction of the lens is a position in a third direction orthogonal to the first direction and the second direction. This eliminates the need to prepare a plurality of processing profiles, for example, during profile processing for manufacturing a lens 31 mold. In addition, since the depth at which the die is cut can be made substantially the same (including the same), the processing becomes easy. Furthermore, it becomes easy to cut and process the glass constituting the lens 31 directly. As a result, the diffusion plate can be efficiently manufactured with high productivity and processing accuracy.

In the present embodiment, a plurality of lenses 31 are formed adjacent to each other so that a boundary ridge line between the lenses 31 is formed in the effective diameter portion of the lens 31. Therefore, a flat surface having no diffusion effect is not formed in the gap between the lens 31 and the lens 31. Thereby, the light 5 incident on the diffusion plate 3 can be diffused efficiently.

In the present embodiment, the lattice 43 of the basic arrangement 4 is formed in a rectangular shape. In this case, the lenses 31 adjacent to each other are arranged so as to form a boundary ridgeline. Thereby, the diffused light of the irradiation range close | similar to the rectangular shape suitable for the angle of view of the imaging device 1 can be obtained with the diffusion plate 3 of the said shape.

It should be noted that there is no adjacent lens 31 outside the lens 31 at the outermost edge of the lens array 30. Therefore, only the lens 31 other than the outermost edge portion of the lens array is configured to contact via the boundary ridge line.

As described above, in addition to the conventional interference fringe reduction effect, the diffuser plate of the present embodiment can further reduce light distribution unevenness within a desired irradiation range. Thereby, it is possible to realize a diffusion plate from which diffused light with higher uniformity can be obtained. That is, it is possible to obtain a diffusion plate that can reduce unevenness due to interference fringes and unevenness in light distribution due to nonuniformity when light from a light source enters the diffusion plate.

In addition, the imaging apparatus according to the present embodiment includes the diffusing plate, so that the subject can be photographed with more uniform diffused light.

Example 1
Hereinafter, simulation results of Example 1 in which the diffusion plate 3 described in the above embodiment is designed under the following conditions will be described with reference to FIGS.

FIGS. 3 to 7 show the light distribution in the case where the length of the grid line of the basic arrangement (distance between adjacent grid points) is set based on the predetermined lengths of the different beam diameters of the incident light. It is a figure which shows the result of Example 1 which simulated the characteristic.

3A to 7A show light distribution diagrams of an irradiation range wider than the irradiation range corresponding to a desired angle of view. FIGS. 3B to 7B show the relative light distribution in the row direction of FIG. FIGS. 3C to 7C show the relative light distribution in the column direction of FIG.

The uniformity shown in the figure is evaluated based on the following calculation. That is, the uniformity is calculated by the ratio between the maximum value and the minimum value of light in the area excluding the edge of the screen (rectangular frame). Specifically, the uniformity is evaluated by a ratio within a length range of about 92% in length and width in the center excluding the screen edge.

Furthermore, the light distribution charts shown in FIGS. 3A to 7A show that the whiter the higher the relative intensity of the diffused light and the blacker the lower the relative intensity of the diffused light.

The simulation of Example 1 was performed under the following conditions.

First, the distance between the grid points 40 in the row direction in the basic arrangement 4 is set to 0.28 mm, and the distance between the grid points 40 in the column direction is fixed to 0.20 mm. Next, only the beam diameter in the first direction of the laser diode that is the light source 2 and the length in the radial direction of the beam diameter in the second direction are changed.

Based on the above conditions, the ratio of the length of the first grid line / the beam diameter in the first direction and the length of the second grid line / the beam diameter in the second direction is set to a predetermined value, and the simulation is performed. did. The results are shown in FIGS. This corresponds to a simulation in which the distance between the lattice points 40 of the diffusion plate 3 is changed.

At this time, the uniformity of the light distribution in the range corresponding to the angle of view, specifically, the minimum / maximum value of the intensity of the irradiated light within the range corresponding to the angle of view was evaluated as the uniformity.

Hereinafter, the simulation results of FIGS. 3 to 7 will be described individually.

First, FIG. 3 shows the uniformity when the length of the first grating line / the beam diameter in the first direction is 1/12 and the length of the second grating line / the beam diameter in the second direction is 1/8. And simulated. As a result, the uniformity of light distribution was 64%.

Next, FIG. 4 shows the uniformity when the length of the first grating line / the beam diameter in the first direction is 1/10, and the length of the second grating line / the beam diameter in the second direction is 1/7. Was simulated. As a result, the uniformity of light distribution was 62%.

Next, FIG. 5 shows the case where the length of the first grating line / the beam diameter in the first direction is 1/7, and the length of the second grating line / the beam diameter in the second direction is 1 / 5.5. Uniformity was simulated. As a result, the uniformity of light distribution was 50%.

Next, FIG. 6 shows the uniformity when the length of the first grating line / the beam diameter in the first direction is 1/5 and the length of the second grating line / the beam diameter in the second direction is 1/4. Was simulated. As a result, the uniformity of light distribution was 36%.

Next, in FIG. 7, the length of the first grating line / the beam diameter in the first direction is set to 1/4, and the length of the second grating line / the beam diameter in the second direction of the light is set to 1 / 3.5. The uniformity of the case was simulated. As a result, the uniformity of light distribution was 10%.

From the above simulation results, the following was found.

That is, the ratio of the length of the first grating line / the beam diameter in the first direction and the length of the second grating line / the beam diameter in the second direction is less than 1/5 as shown in FIGS. If it is increased, the light quantity ratio in the range corresponding to the angle of view is reduced. Accordingly, a relatively dark place increases in the range of the angle of view. As a result, it can be seen that a large amount of uneven light distribution occurs and the uniformity of the light distribution decreases.

In the field of irradiating the subject with imaging light, the light intensity ratio between the central portion (maximum light amount) and the four corners (minimum light amount) in the range corresponding to the angle of view is about 45 to 50% as the uniformity of light distribution. Is needed.

Considering the above result and an appropriate light quantity ratio, the ratio of the length of the first grating line / the beam diameter in the first direction and the length of the second grating line / the beam diameter in the second direction is 1/5 or less. Considered desirable.

(Example 2)
Hereinafter, Example 2 in which the diffusion plate described in the above embodiment is designed under the following conditions will be described with reference to FIGS.

8, 10, 12, 14, and 16 show the lens of the diffuser plate when the position of the vertex 310 of the lens with respect to the lattice point 40 of the basic arrangement is shifted by a predetermined ratio in the row direction and the column direction, respectively. An example of an array configuration is shown. Here, the predetermined ratio is a ratio of the shift amount in the row direction / the length of the first grid line and the shift amount in the row direction / the length of the second grid line.

On the other hand, FIG. 9, FIG. 11, FIG. 13, FIG. 15 and FIG. 17 are diagrams showing the results of Example 2 in which the light distribution characteristics are simulated for the configuration examples of the lens arrays designed with the different ratios. . In addition, (A) of each said figure has shown the light distribution map of the irradiation range wider than the irradiation range corresponded to a desired angle of view. (B) of each figure has shown the relative light distribution in the row direction of (A). (C) of each figure has shown the relative light distribution in the column direction of (A). In addition, the uniformity shown in each figure is evaluated by calculating the ratio of the maximum value and the minimum value of light in the area excluding the edge of the screen (rectangular frame), as in the first embodiment. Yes.

The light distribution shown in FIGS. 9, 11, 13, 15, and 17 (A) shows the intensity distribution diagram of the diffused light in the necessary irradiation range, and the white areas indicate higher relative intensity. Yes.

That is, in Example 2, the beam diameter and the basic arrangement of the lens array were fixed, and only the shift amount Ra of the vertex of the lens was changed for simulation. The shift amount Ra is a generic term for the shift amount Ra1 and the shift amount Ra2.

The simulation of Example 2 was performed under the following conditions.

First, the ratio of the row-direction shift amount Ra1 / first grid line length and the row-direction shift amount Ra2 / second grid line length is set to the same one value. That is, as the ratio, different values such as 1/5 and 1/6 are not set, and “0 (no deviation)” or “± Ra of one value” is set.

Hereinafter, a configuration example of the lens array of FIGS. 8 to 17 and a simulation result thereof will be individually described.

First, FIGS. 8 and 9 are uniform when the ratio of the shift amount in the row direction / the length of the first grid line is 1/6, and the ratio of the shift amount in the column direction / the length of the second grid line is 1/6. The sex was simulated. As a result, the uniformity of light distribution in the range corresponding to the angle of view was 50%.

Next, FIG. 10 and FIG. 11 show the ratio of the maximum value of the shift amount of the vertex of the lens in the row direction / the length of the first grid line to 1/5, the maximum value of the shift amount in the column direction / the second grid line. The uniformity when the length ratio was 1/5 was simulated. As a result, the uniformity of light distribution was 46%.

Next, FIG. 12 and FIG. 13 show the ratio of the maximum value of the shift amount in the row direction of the vertex of the lens / the length of the first grid line to 1/4, the maximum value of the shift amount in the column direction / the second grid line. The uniformity when the length ratio of ¼ was set to ¼ was simulated. As a result, the uniformity of light distribution was 42%.

Next, FIG. 14 and FIG. 15 show the ratio of the maximum value of the shift amount of the vertex of the lens in the row direction / the length of the first grid line to 1/3, the maximum value of the shift amount in the column direction / the second grid line. The uniformity when the length ratio was 1/3 was simulated. As a result, the uniformity of light distribution was 38%.

Next, FIG. 16 and FIG. 17 show the ratio of the maximum value of the shift amount in the row direction of the vertex of the lens / the length of the first grid line to 1/2, the maximum value of the shift amount in the column direction / the second grid line. The uniformity was simulated when the ratio of the lengths was 1/2. As a result, the uniformity of light distribution was 35%.

From the above simulation results, the following was found.

That is, the ratio of the maximum value of the shift amount in the row direction of the vertex of the lens / the length of the first grid line, and the ratio of the maximum value of the shift amount in the column direction / the length of the second grid line are 1/4 to As it becomes 1/2, the darker area increases. As a result, it can be seen that a large amount of uneven light distribution occurs and the uniformity of the light distribution decreases.

In the field of irradiating the subject with imaging light, as described in the first embodiment, the light distribution ratio between the central portion (maximum light amount) and the four corners (minimum light amount) is 45 to 50 as the uniformity of light distribution. % Is needed.

Considering the above results and an appropriate light quantity ratio, the amount of shift in the row direction of the position of the apex of the lens relative to the basic arrangement / the ratio of the length of the first grid line, and the amount of shift in the column direction / second grid line It is considered that the length ratio is preferably 1/5 or less.

Note that the diffusion plate and the imaging device including the diffusion plate of the present invention are not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.

For example, in the above embodiment, the semiconductor laser diode is described as an example of the light source, but a light emitting diode (LED) may be used, for example. Even in this case, the same effect as described above can be obtained.

In the above-described embodiment, the case where the beam of the light 5 incident on the diffusion plate is elliptical has been described as an example. However, for example, a circular shape or a square shape may be used. Even in this case, the same effect as described above can be obtained.

In the above embodiment, the configuration in which the diffusion plate is applied to a distance image camera of the TOF (Time Of Flight) system has been described as an example. However, the present invention may be applied to, for example, a projector. Even in this case, the same effect as described above can be obtained.

In the above embodiment, the configuration in which the diffusing plate is disposed to face the light source has been described as an example. However, the present invention is not limited to this. For example, a collimating lens may be installed between the light source and the diffusion plate. Thereby, even in the case where the light from the light source is incident on the diffusion plate in parallel, the present embodiment can be similarly applied.

As described above, the diffusing plate of the present invention includes a lens array in which a plurality of lenses are arranged adjacent to each other on a plane based on a basic arrangement, and the vertex positions of the plurality of lenses have a row direction and a column. Arranged at random from the basic arrangement virtually arranged in the direction. The basic arrangement includes a plurality of lattice points that are reference positions of the vertices of a plurality of lenses, a first lattice line that connects two lattice points adjacent in the row direction among the plurality of lattice points, and a first lattice line And a second grid line connecting two grid points adjacent in the column direction among the plurality of grid points. Further, the direction of the first grating line is aligned with the radial direction of the beam diameter in the first direction of the incident light, and the direction of the second grating line is the radial direction of the beam diameter in the second direction of the incident light. The length of the first grating line is set shorter than the length of the beam diameter in the first direction of the incident light, and the length of the second grating line is set in the second direction of the incident light. It is set shorter than the length of the beam diameter. And it is good also as a structure which arrange | positions the vertex of a some lens at random from each lattice point.

Usually, the length of the first grid line or the length of the second grid line is longer than the radial direction of the beam diameter in the first direction and the radial direction of the beam diameter in the second direction at the time of incidence. Then, the irradiation light becomes non-uniform due to non-uniformity of the light source.

In the diffusion plate of the present invention, the length of the first grating line is 1/5 or less of the beam diameter in the first direction, and the length of the second grating line is smaller than the beam diameter in the second direction. It is preferable that it is 1/5 or less.

According to this configuration, even if there is non-uniformity in the light emitted from the light source, it can be uniformly diffused by the diffusion plate.

Further, the diffusion plate of the present invention is configured such that the vertices of the plurality of lenses are randomly shifted from the plurality of lattice points based on the amount of displacement determined by assigning a predetermined amount of displacement to each of the plurality of lattice points. Be placed. The shift amount in the row direction of the vertices of the plurality of lenses with respect to the plurality of lattice points is 1/5 to 1/15 of the first lattice line, and the column direction of the vertices of the plurality of lenses with respect to the plurality of lattice points. The shift amount is preferably 1/5 to 1/15 of the second lattice line.

According to this configuration, the light of the individual lenses can be appropriately overlapped while maintaining the effect of reducing the interference fringes. Thereby, the uniformity of diffused light can be improved.

Specifically, when the vertex positions of the respective lenses are randomly arranged, first, the shift amount is obtained with reference to the first grid line and the second grid line. Then, for each lens, it is assigned whether to shift the length of the vertex position from the lattice point by the amount of shift (actual shift amount = shift amount) or not shift at all (actual shift amount = 0). The actual shift amount is determined, and the vertex positions of the lenses are randomly arranged.

At this time, if the amount of shift is increased beyond the upper limit of 1/5, the amount of overlap of light spreading through each lens decreases. This makes it impossible to obtain a uniform intensity distribution up to the periphery. On the other hand, below the lower limit value 1/15, the grid is too close to the regularly arranged lattice. Thereby, when the light which spreads through each lens overlaps, an interference fringe (diffraction pattern) arises. Therefore, the above effect can be obtained by setting within the range of 1/5 to 1/15.

In addition, the diffusion plate of the present invention is a normal one in which the variation of the deviation amount from the plurality of lattice points of the basic arrangement for each vertex of the plurality of lenses is a standard deviation with a value of 1 / 2.5 or more of the maximum displacement amount. It is preferable to make it vary according to the distribution.

According to this configuration, the position of the apex of each lens can be varied more than a certain amount by allocating the amount of deviation from the basic arrangement. Thereby, it is possible to prevent the apexes of the lenses from being arranged in a regular arrangement in which diffused light interference easily occurs. As a result, the effect of reducing the occurrence of interference fringes is improved.

In the diffusing plate of the present invention, it is preferable that the plurality of lenses have the same radius of curvature and the apexes of the plurality of lenses are located on the same plane.

According to this configuration, it is not necessary to prepare a plurality of processing profiles, for example, at the time of profile processing for manufacturing a lens mold. Further, since the depth of cutting the mold can be made substantially the same, the processing becomes easy. Furthermore, it becomes easy to directly cut and process the glass constituting the lens.

In the diffusing plate of the present invention, it is preferable that the lenses other than the outermost edge of the lens array are adjacent to each other so that a boundary ridge line between the lenses is formed.

According to this configuration, the lenses other than the outermost edge portion of the lens array are formed adjacent to each other so that a boundary ridge line between the lenses can be formed. Therefore, a plane having no diffusion effect is not formed in the gap between adjacent lenses. Thereby, the light incident on the lens array of the diffusion plate can be diffused efficiently.

Moreover, it is preferable that the imaging apparatus of the present invention includes the above diffusion plate. Thereby, it is possible to provide an imaging device capable of photographing a subject with uniform diffused light.

The present invention can be applied to, for example, a diffusion plate having a lens array for a TOF-type distance image camera that creates a three-dimensional distance distribution image, and an imaging device including the diffusion plate.

DESCRIPTION OF SYMBOLS 1 Imaging device 2 Light source 3 Diffusion plate 4 Basic arrangement 5 Light 30 Lens array 31

Lens

310, 310a, 310b, 310c, 310d Vertex 40 Lattice point 41 First grating line 42 Second grating line 43 Lattice 50 Beam diameter in the first direction 51 Beam diameter in the second direction

Claims

A lens array in which a plurality of lenses are arranged adjacent to each other on a plane;
The vertex positions of the plurality of lenses are arranged randomly shifted from the basic arrangement virtually arranged in the row direction and the column direction,
The basic arrangement is a plurality of grid points that are reference positions of the vertices of the plurality of lenses, and
A first grid line connecting two grid points adjacent in the row direction among the plurality of grid points;
A second grid line that is orthogonal to the first grid line and connects two grid points adjacent in the column direction among the plurality of grid points, and
The direction of the first grating line is aligned with the radial direction of the beam diameter in the first direction of incident light, and the direction of the second grating line is aligned with the radial direction of the beam diameter of the incident light in the second direction. The length of the first grating line is set shorter than the length of the beam diameter in the first direction of the incident light,
The length of the second grating line is set shorter than the length of the beam diameter in the second direction of the incident light,
The diffusing plate is arranged such that vertices of the plurality of lenses are randomly shifted from respective lattice points.
The length of the first grid line is 1/5 or less of the beam diameter in the first direction, and the length of the second grid line is 1/5 or less of the beam diameter in the second direction. The diffusion plate according to claim 1.
The vertices of the plurality of lenses are randomly shifted from the plurality of grid points based on a shift amount determined by assigning a predetermined shift amount to each of the plurality of grid points,
The shift amount in the row direction of the vertices of the plurality of lenses with respect to the plurality of lattice points is a length of 1/5 to 1/15 of the first lattice line,
2. The diffusion plate according to claim 1, wherein the shift amount in the column direction of the vertices of the plurality of lenses with respect to the plurality of lattice points is 1/5 to 1/15 of the second lattice line.
The variation in the amount of deviation from the plurality of lattice points of the basic arrangement for each vertex of the plurality of lenses can be varied so as to follow a normal distribution in which a value of 1 / 2.5 or more of the maximum amount of displacement is a standard deviation. The diffusion plate according to claim 1.
2. The diffuser plate according to claim 1, wherein the plurality of lenses have the same radius of curvature, and the plurality of lenses have vertexes located on the same plane.
The diffuser plate according to claim 1, wherein the lenses other than the outermost edge portion of the lens array are adjacent to each other so that a boundary ridge line between the lenses is formed.
An imaging device comprising the diffusion plate according to claim 1.