CN115685413A - Micro-lens array and projection device - Google Patents

Abstract

The invention provides a microlens array and a projection apparatus, which have good cut-off characteristics and inhibit the generation of diffraction bright spots. The microlens array has: a substrate that is transparent to the wavelength of use; and a plurality of aspherical lenses formed on a first surface of the base, centers of the aspherical lenses being located at two or more different positions in a direction orthogonal to the first surface, and a deviation of pitches of an area excluding 25% of both ends of the aspherical lenses arranged in an arbitrary one-dimensional direction in a plane of the first surface from an average of all pitches is less than 7.5%.

Description

Micro-lens array and projection device

Technical Field

The invention relates to a micro lens array and a projection device.

Background

A technique is known in which a plurality of concave lenses are formed on the surface of a transparent base material, and light is diffused by utilizing a refraction phenomenon of light (see, for example, patent documents 1 and 2). Fig. 1 is a schematic diagram of a conventional lens array, where (a) is a plan view and (B) is a vertical sectional view. In the known diffuser plate having the array of the concave lenses LNS, the depths of the concave lenses LNS are dispersed to d1, d2, \8230, and the center coordinate C positions of the concave lenses LNS are dispersed in the in-plane direction. In fig. 1 (a), as a reference, the equally spaced positions in the X-Y plane are indicated by circles of broken lines. The center coordinates C of the concave lenses LNS are deviated from the center of the equally spaced positions in both the X and Y directions as compared with the equally spaced positions, and the pitches are dispersed as P1, P2, \8230; \ 8230in the X-Y plane. By varying the depth d and pitch P of the concave lens LNS, the occurrence of diffracted light in only a specific direction is suppressed.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 6424418

Patent document 2: japanese patent No. 6680455

Disclosure of Invention

Problems to be solved by the invention

The inventors have found that if the pitch of the lenses arranged in an arbitrary one-dimensional direction is varied in the microlens array, it is difficult to provide a favorable cutoff characteristic for the distribution of diffused light. Further, it was found that diffraction spots may occur depending on the degree of depth variation.

The invention aims to provide a microlens array which has good cut-off characteristics and can inhibit the generation of diffraction bright spots.

Means for solving the problems

In one embodiment of the present invention, a microlens array includes: a substrate that is transparent to the wavelength of use; and a plurality of aspherical lenses formed on the first surface of the base material,

the center of the aspherical lens is at two or more different positions in a direction orthogonal to the first surface,

in the first surface, the average pitch deviation of the regions other than 25% of both ends of the aspherical lenses arranged in an arbitrary one-dimensional direction with respect to the entire pitch is less than 7.5%.

Effects of the invention

A microlens array having a good cut-off characteristic and suppressing the generation of diffraction bright spots is realized.

Drawings

Fig. 1 is a schematic diagram of a conventional lens array.

Fig. 2 is a schematic cross-sectional view and a top-view image of a microlens array of an embodiment.

Fig. 3 is a sample image of a microlens array of an embodiment.

Fig. 4 is a cross-sectional view X-X' of fig. 3.

Fig. 5 is a diffusion profile of the microlens array of fig. 3.

Fig. 6 is a diagram showing a simulation result of the aspherical lens array.

Fig. 7 is a simulation diagram of a diffusion distribution when the depth deviation of the aspherical lens is changed.

Fig. 8 is a simulation diagram of a three-dimensional intensity distribution and a two-dimensional intensity distribution when the depth deviation of the aspherical lens is changed.

Fig. 9A is a plan view of an actually manufactured sample.

Fig. 9B is an actual measurement of the lens depth at the line I-I' of fig. 9A.

Fig. 9C is an analysis result of the measured values of fig. 9B.

Fig. 9D is a diagram showing the upper limit of the depth variation of the aspherical lens.

Fig. 10 is a diffusion profile in the Y direction for the sample of fig. 9A.

Fig. 11 is a simulation diagram of a diffusion distribution when the in-plane pitch variation of the aspherical lens is changed.

Fig. 12 is a graph showing the variation of the cut-off band as a function of the pitch deviation.

Fig. 13 is a diagram illustrating a method of determining the cutoff band.

Fig. 14 is a simulation diagram of a two-dimensional intensity distribution when the pitch deviation in only the Y direction of the aspherical lens is changed.

Fig. 15 is a graph showing changes in the relative pitch ratio of samples prepared by changing the maximum pitch shift in the Y direction.

Fig. 16A is a diagram showing the actual measurement result of the diffusion characteristic when the maximum pitch variation in the Y direction is changed.

Fig. 16B is a simulation of the diffusion characteristics corresponding to fig. 16A.

Fig. 17 is an enlarged view of a partial region of fig. 16A.

Fig. 18 is a diagram for explaining a method of determining the slope as the cutoff characteristic.

Fig. 19 is a graph showing the analysis result of fig. 17.

Fig. 20 is a schematic diagram of a projection apparatus to which a microlens array of an embodiment is applied.

Detailed Description

In the embodiment, in the micro lens array having a plurality of aspherical lenses formed on the first surface of the base material transparent to the use wavelength, the center positions of the aspherical lenses are deviated in the direction orthogonal to the first surface, and the pitch deviation of the aspherical lenses is suppressed in the surface of the first surface. Specifically, as described later, the average pitch deviation of the regions other than 25% of both ends of the aspherical lenses arranged in an arbitrary one-dimensional direction in the plane of the first surface with respect to the entire pitch is suppressed to less than 7.5%, and more preferably, to 5.0% or less. By suppressing the pitch variation in the surface of the aspherical lens, the cut-off characteristic of the diffusion distribution is improved. Further, the diffraction bright point is suppressed by making the center deviation of the aspherical lens, that is, the lens depth deviation, a predetermined ratio or more with respect to the average value deviation.

Fig. 2 shows an example of the microlens array 10 according to the embodiment. Fig. 2 (a) is a schematic cross-sectional view of the microlens array 10, and (B) is an image viewed from above.

As shown in fig. 2 (a), the microlens array 10 has a plurality of aspherical lenses 13 formed on a first surface 101 of a substrate 11 transparent to a use wavelength. In this example, the aspherical lens 13 is a concave lens having a paraboloid. The center 14 of the aspherical lens 13 is located at two or more different positions in a direction orthogonal to the first surface 101, in this example, in the depth direction of the base material 11. That is, the depth d of the aspherical lens 13 varies.

On the other hand, the pitch P between the centers 14 of the aspherical lenses 13 is substantially constant. So-called "substantially constant"This means that the pitch variation is suppressed to be smaller than a predetermined variation. The pitch shift in the present specification represents an absolute value of a maximum difference that a ratio of randomly distributed relative pitches in all pitches of the lens in the one-dimensional direction can satisfy, assuming that an average pitch of a region excluding 25% of both ends in all pitches in any one-dimensional direction is 1, and is expressed as σ _p . In the microlens array 10, when the lenses are arranged while looking in an arbitrary one-dimensional direction, the pitch deviation σ of the aspherical lenses 13 of the regions other than 25% of both ends _p Is suppressed to less than 0.075, i.e. a deviation from the average pitch of less than 7.5%.

In fig. 2 (B), a white dot at the center of each aspherical lens 13 indicates the lens center. The microlens array 10 includes a square array of aspherical lenses 13, and has substantially constant pitches in the X direction (horizontal direction of the drawing) and the Y direction (vertical direction of the drawing). The absolute value of the pitch is related to the diffusion angle for that direction. In the example of fig. 2 (B), the aspect ratio of the pitches in the X direction and the Y direction is set to be larger than 1, but when a square projection image is formed, the pitch of the aspherical lens 13 may be designed to be the same value in the X direction and the Y direction. In any case, the pitch variation of the aspherical lens 13 is suppressed to less than 7.5%, more preferably to 5.0% or less in the one-dimensional directions such as the X direction and the Y direction, and the lens arrangement is substantially regular in the in-plane direction.

By arranging the aspherical lenses 13 regularly in the X-Y plane, the cutoff characteristics of the diffusion distribution of the microlens array 10 can be improved. By causing a certain degree or more of deviation in the depth position of the center 14 of the aspherical lens 13 of the microlens array 10 in the direction orthogonal to the X-Y plane (i.e., the first plane 101), the occurrence of diffraction bright spots can be suppressed. Hereinafter, (1) the deviation in the direction orthogonal to the first surface 101 and (2) the regularity of the in-plane arrangement of the first surface 101 of the aspherical lens 13 will be described in detail.

< deviation in the direction orthogonal to the first surface >

Fig. 3 is a top view image of a sample of the microlens array 10 of the embodiment, and fig. 4 is a schematic view of the X-X' section of fig. 3. As shown in fig. 3, the plurality of aspherical lenses 13 are regularly arranged in the X-Y plane. In the Z direction orthogonal to the X-Y plane, the center 14 of the aspherical lens 13 is at two or more different positions, and therefore the conic coefficient, the radius of curvature, and the like of each aspherical lens 13 are different.

As shown in the cross-sectional profile of fig. 4, the pitch P between the centers 14 of the aspherical lenses 13 is approximately constant, but the depths are deviated as d1, d2, d3, \8230that. In the sample of fig. 3, the difference Δ d between the depths d1 and d2 is about 8 μm.

The aspherical lens 13 having substantially uniform in-plane pitches of the first surface 101 and having variations in depth or height of the lens in a direction perpendicular to the first surface 101 is formed by wet etching a glass substrate subjected to pretreatment. In the pretreatment, a part of the inner region of the glass substrate may be modified by irradiating a pulsed laser beam to a certain position of the glass substrate, and the glass substrate may have a density distribution in the thickness direction at least at the position irradiated with the pulsed laser beam, or a predetermined wedge-shaped recess may be formed on the surface of the glass substrate by a chemical or physical method (for example, see WO 2019/189225). In the wet etching, as shown in fig. 4, etching is performed so that a flat surface does not remain between the adjacent aspherical lenses 13. This is because, if a flat surface remains, light travels straight without being diffracted, and 0 th order light is generated, which becomes a bright point.

When the aspherical lens 13 is formed as a convex lens, a plurality of concave surfaces having a constant pitch and a varying depth may be formed on a substrate by the above-described method, and then the substrate may be used as a mold to form a convex lens array.

Although the aspherical lenses 13 of the microlens array 10 of fig. 3 have sufficient variation in the depth or height direction, it is unclear how the extent of the variation in the depth or height of the aspherical lenses 13 affects the diffraction bright points. Therefore, how the deviation of the lens center position in the direction orthogonal to the first surface 101 affects the diffraction bright point is investigated.

Fig. 5 is a diffusion profile in the Y direction of the microlens array 10 of fig. 3. The horizontal axis is the diffusion angle (°), and the vertical axis is the relative intensity. The diffusion profile of the microlens array 10 has a rectangular pulse shape. If ordinary ground glass is used for the diffusion plate, the laser light becomes a diffusion distribution in a gaussian distribution shape in the far field. In contrast, the microlens array 10 of fig. 3 is designed to diffuse light to a rectangular field of view. In this example, the Field angle (FOV: field of View) in the Y direction is 45 °.

In the embodiment, when referring to the "FOV" of the microlens array 10, it means an angular range in which the relative intensity of the diffusion distribution becomes 0.5 or more. The relative intensity is an intensity at which an average intensity in a range of a diffusion angle of-10 ° to +10 ° is normalized to 1. The FOV of the diffusion distribution in the X direction of the microlens array 10 measured based on this definition is 60 °, and the FOV in the Y direction is 45 ° as described above. The steepness of the rise of the diffusion distribution indicates the cutoff characteristic, but the cutoff characteristic will be described later, and the suppression of the diffraction bright point is considered here.

In the microlens array 10 that diffuses light to a rectangular field of view, it is preferable that the intensity distribution at the top of the diffusion distribution is flat (flat). This is because if the intensity of the diffracted light is locally strong, a diffraction bright spot is generated, and brightness unevenness occurs in the projected image. There should be a range of suitable depth deviations where the top of the diffusion profile is close to flat. Therefore, it is examined by simulation how the diffraction spot is affected by the degree of the depth deviation of the aspherical lens 13.

Fig. 6 is a diagram showing a simulation result of the aspherical lens array. As the substrate 11 transparent to visible light, "D263T eco" glass (manufactured by SCHOTT corporation) having a refractive index of 1.5230 with respect to D-line was used. The diffusion pattern obtained in the optical measurement was observed on a screen 103mm away, and the measurement minimum resolution was set to 0.5 μm, the wavelength of the measurement light was set to 940nm, and the beam diameter was set to 3mm. Next, a plurality of aspherical lenses 13 are disposed on the base 11. The conic coefficient of the aspherical lens 13 was set to-1, the pitch in the X direction was set to 100 μm, the pitch in the Y direction was set to 83 μm, and the pitch deviation between the X direction and the Y direction was set to 0. Further, the depth deviation of the aspherical lens 13 was set to 2.00 μm. The depth deviation is 1 σ when the depth of the aspherical lens 13 of the microlens array 10 follows a normal distribution, and is a deviation (standard deviation) from a median or a mean.

The FOV in the X direction of the microlens array 10 obtained by the simulation was 52.9 °, and the FOV in the Y direction was 43.2 °. When the depth deviation of the aspherical lens 13 is set to 2.0 μm, the relative intensity slightly increases at both ends of the top of the diffusion distribution in the X direction and the Y direction, but the peak values at both ends of the top do not fluctuate (fluctuate) greatly and are almost flat. When the top of the diffusion profile is referred to as "flat", it means that a diffraction bright point is suppressed in the intensity profile, or that the substantial entirety of the fluctuation of the top of the diffusion profile converges between 0.8 and 1.2 in the relative intensity.

Next, under the above conditions, the diffusion distribution is obtained by changing only the depth variation of the aspherical lens 13. Fig. 7 shows the simulation results in which the depth deviation (1 σ) of the aspherical lens 13 was changed in seven ways, i.e., 0.00 μm, 0.40 μm, 0.80 μm, 1.20 μm, 1.60 μm, 2.00 μm, and 2.40 μm.

According to the simulation results of fig. 7, the vertical variation of the relative intensity at both ends of the top part becomes large when the depth deviation (1 σ) is 0.00 μm, 0.40 μm, and 0.80 μm, but the relative intensity is substantially converged between 0.8 and 1.2 when the depth deviation is 1.20 μm or more. Thus, the depth variation is larger than 0.80. Mu.m, preferably 1.20 μm or more, more preferably 1.60 μm or more, further preferably 2.00 μm or more, and further preferably 2.40 μm or more. This can suppress the relative intensity in the FOV range to 1.2 or less, and make the intensity distribution nearly uniform.

Fig. 8 shows a three-dimensional intensity distribution (upper layer) and a two-dimensional intensity distribution (lower layer) in the X-Y plane when the aspherical lens 13 has a depth variation (1 σ) of 0.00 μm, 0.80 μm, 1.60 μm, and 2.40 μm. When the depth variation is 0.00 μm or 0.80 μm, the edge peaks along the diffusion region are more numerous, and a stripe-like intensity difference appears inside the diffusion region. The fringes within the peak, diffuse area along the edge are caused by the generation of diffracted bright spots. On the other hand, when the depth variation is 1.60 μm, the intensity distribution in the diffusion region, particularly in the central portion, becomes uniform. When the depth deviation is 2.00. Mu.m, the intensity distribution becomes uniform as a whole including the edge region.

As is clear from the simulation results of fig. 7 and 8, the influence of the diffraction spot can be suppressed by making the depth deviation (1 σ) of the aspherical lens 13 larger than 0.80 μm. The depth variation of the aspherical lens 13 is preferably 1.20 μm or more, more preferably 1.60 μm or more, further preferably 2.00 μm or more, and further preferably 2.40 μm or more. On the other hand, if the depth deviation is too large, the diffusion profile is not flat-topped but approaches a gaussian profile shape. When a rectangular diffusion region is realized by the microlens array 10 in which the aspherical lenses 13 are arranged in a square, the shape of the diffusion distribution is more preferably flat-topped than gaussian. As will be described later with reference to fig. 9D, the depth variation (1 σ) is preferably less than 6.00 μm, and more preferably 4.00 μm or less.

Fig. 9A is a top view of the microlens array 10A actually manufactured, fig. 9B is an actual measured value of the depth deviation along the line I-I' of fig. 9A, and fig. 9C is a histogram of the actual measured value of the depth deviation. As a result of measuring the depths of the 63 aspherical lenses 13 along the line I-I' of fig. 9A, as shown in fig. 9B, the in-plane pitch is substantially constant, and only the depths of the aspherical lenses 13 are varied.

The aspherical lenses 13 of the microlens array 10A had a median depth of 29.275 μm, an average value of 29.486 μm, a maximum value of 37.634 μm, a minimum value of 25.139 μm, and a depth deviation (standard deviation) of 2.643 μm. Since the depth variation that can suppress the influence of the diffraction bright spot depends not on the relative relationship with the absolute value but on the average value, the average value is represented by μ, and a value (σ/μ) obtained by dividing the standard deviation σ by the average value is introduced as a new index. The value of σ/μ in the microlens array was 0.090 (2.643/29.486).

Fig. 9D is a diagram showing the upper limit of the lens depth variation. If the depth variation is 6.00 μm or more, the flatness of the top portion of the diffusion profile becomes insufficient. The new index at this time has a value of 0.203. That is, if the value of the new index is less than 0.203, the flatness of the top of the diffusion profile is maintained. When the depth deviation is 4.0 μm or less (the new index σ/μ is 0.136 or less), the top of the diffusion profile becomes flatter.

Fig. 10 is a diffusion distribution in the Y direction of the microlens array 10A of fig. 9A. At a value of 0.090 of the new index σ/μ, the relative intensity of the top of the diffusion profile converges between 0.8 and 1.2, with sufficient depth deviation for bright point suppression. This also applies to the case where the microlens array 10A is a convex lens array, and by giving appropriate height deviation to the convex aspherical lenses, it is possible to keep the variation in the relative intensity of the top of the diffusion profile between 0.8 and 1.2.

From the above consideration, by dispersing the center position of the aspherical lens 13 at two or more different positions in the direction perpendicular to the surface of the microlens arrays 10, 10A on which the aspherical lens 13 is formed, the diffraction bright point can be suppressed. The top of the diffusion distribution can be flattened by dividing the positional deviation in the direction orthogonal to the lens formation surface, that is, the depth deviation (1 σ), by the average value (μ), to obtain a value (σ/μ) greater than 0.027, preferably 0.041 or more, more preferably 0.054 or more, further preferably 0.068 or more, and further preferably 0.081 or more, and less than 0.200.

< regularity of in-plane arrangement of aspherical lens >

Next, the regularity of the lens arrangement on the first surface 101 of the base material 11 was examined. As described later, it is advantageous for the cutoff characteristic to adopt a regular arrangement in the two-dimensional plane in which the aspherical lens 13 is arranged. The cutoff characteristic of the microlens array 10 is a rapid change in light diffusion or light blocking in a predetermined direction.

Fig. 11 is a simulation diagram of the diffusion distribution when the pitch deviation of the aspherical lens 13 is changed. As described above, the pitch deviation represents the absolute value of the maximum difference that a ratio of randomly distributed relative pitches can be obtained in all pitches of a predetermined region (region excluding 25% of both ends) in the plane of the first surface 101, assuming that the average pitch in each of the X direction and the Y direction is 1, and is expressed as σ _p (refer to fig. 2). In the simulation, the FOV in the Y direction was set to 45 °, and the diffusion characteristics were calculated by changing the pitch variation in the Y direction to 0.0%, 5.0%, 7.5%, 10.0%, 15.0%, 20.0%, and 25.0%.

A part of the area on the front side of the diffusion profile is shown in an enlarged manner. As the pitch variation in the plane becomes larger, the rise or fall of the diffusion distribution becomes more gradual, and the cut-off characteristic deteriorates. In particular, when the in-plane pitch deviation exceeds 10.0%, the steepness is lost in the lower part of the diffusion distribution.

FIG. 12 is a graph plotting the cut-off band as a function of pitch deviation from the simulation results of FIG. 11. The cut-off band in an embodiment is the angular width required for the intensity of the diffusion profile to change to a specified level. The definition of a more accurate cut-off band is explained with reference to fig. 13.

Fig. 13 is a diagram illustrating a method of determining the cutoff band. The "cut-off band" of an embodiment is the angular width required for the relative intensity to vary between 0.2 and 0.8. The relative intensity of the diffusion distribution is the same as defined in the study of the depth deviation of the aspherical lens 13, and is the intensity when the average of the intensities (light amounts) in the range of the diffusion angle of-10 ° to +10 ° is normalized to 1. The angular widths at which the relative intensity changes from 0.2 to 0.8 or from 0.8 to 0.2 are determined on the negative side and the positive side of the diffusion distribution, respectively, and the larger of the two angular widths is taken as a cut-off band.

The smaller the cut-off band, the steeper the rise and fall of the diffusion distribution, and the better the cut-off characteristic. The larger the cut-off band, the more gradual the rise and fall of the diffusion distribution, and the more deteriorated the cut-off characteristics.

Returning to fig. 12, the larger the pitch deviation of the aspherical lens, the larger the cut-off band (°) becomes, so it is preferable to keep the pitch deviation small and the cut-off band small. In the simulation example of fig. 12, the pitch deviation of the aspherical lens 13 is preferably less than 0.075 (or 7.5%), more preferably 0.050 (or 5.0%) or less, at which the cut-off band starts to increase sharply.

Fig. 14 is a two-dimensional electromagnetic field simulation result when the pitch deviation of the aspherical lenses 13 of the microlens array 10 is changed only in the Y direction. When the pitch variation in the Y direction is 0.0% or 5.0%, the bleeding in the Y direction, which is the longitudinal direction of the paper surface, is small. When the pitch deviation in the Y direction reached 10%, bleeding occurred in the Y direction. As the pitch variation is larger, the bleeding pattern in the Y direction becomes more remarkable. The stringe mode is remarkable, meaning that the lower part of the diffusion distribution is relaxed. Since the axes in the X direction and the Y direction are determined by any method, the same applies to the pitch deviation in the X direction.

As is clear from the simulation results shown in fig. 12 and 14, the in-plane pitch variation of the microlens array 10 is preferably less than 7.5%, and more preferably 5.0% or less.

Up to this point, the cutoff band has been studied as a cutoff characteristic based on simulation. Next, the cutoff characteristics were examined based on the actually prepared samples.

Five samples were prepared with the reference pitch in the Y direction set at 84 μm and only the pitch variation varied. The sample a having a pitch deviation of 0.0% in the Y direction is designed so that all the centers of the aspherical lenses 13 are equally spaced in the Y direction. The sample b having a pitch deviation of 5.0% in the Y direction was designed such that the pitches were randomly distributed between the minimum pitch 79.8 μm and the maximum pitch 88.2 μm in the Y direction so that the maximum deviation in the Y direction was 0.05.

Sample c having a pitch variation in the Y direction of 7.5%, sample e having a pitch variation in the Y direction of 15.0%, and sample g having a pitch variation in the Y direction of 25.0% were prepared in the same manner as described below. Samples a, b, c, e, g correspond to pitch deviations a, b, c, e, g in the simulation of FIG. 11.

Fig. 15 is a graph depicting the relative pitch ratio of about 40 rows (about 40 aspherical lenses arranged in the Y direction) of the five samples produced. In all samples, the desired pitch deviation in the Y-direction was achieved. These samples were used to determine diffusion characteristics.

Fig. 16A shows the actual measurement results of the diffusion characteristics of the five samples. Fig. 16B is a diagram in which pitch deviations a, B, c, e, and g corresponding to fig. 16A are extracted from the simulation result of fig. 11. When the actual measurement result of fig. 16A is compared with the simulation result of fig. 16B, the tendency of the diffusion distribution as a whole is the same. In fig. 16A, from the viewpoint of measurement resolution, the cutoff band cannot be accurately calculated as compared with fig. 16B, and therefore, there is a concern that a significant difference in cutoff characteristics due to pitch variation may be buried by the above-described uncertainty. Therefore, as a new indicator of the cutoff characteristic, a slope (gradient) [ deg/a.u. ] that can be compared fairly using the nearest similar values of the predetermined relative intensity and diffusion angle is introduced.

Fig. 17 is an enlarged view of a region of the diffusion characteristic of fig. 16A from-28 ° to-17 ° in diffusion angle. The measured results for the five samples determined the slope, respectively.

Fig. 18 is a diagram illustrating a method of determining the slope. The average of the intensities (light amounts) in the angular range of the diffusion angle-10 ° to +10 ° was normalized to 1. On the negative side and the positive side of the diffusion distribution, points having the closest approximation values with relative intensities of 0.2 and 0.8 are connected, and the slope of the straight line is obtained. The smaller of the absolute values of the two obtained slopes is taken as the slope.

Fig. 19 shows the results of analysis of the diffusion characteristics of samples a, b, c, e, and g in fig. 17.

For each sample, based on the measured values of the diffusion properties, the following were determined:

a most similar value (1) of relative intensity 0.2;

the diffusion angle at the nearest approximation value (1);

a most similar value (2) of relative intensity 0.8; and

the diffusion angle at the nearest approximation value (2).

The slope is the difference between the most similar values of the relative intensities 0.2 and 0.8 divided by the difference in the diffusion angle at each of the most similar values.

There was no significant difference between the in-plane pitch variation of 0.0% and that of 5.0%. When the pitch deviation exceeds 7.5%, the cut-off band increases, the slope decreases, and the cut-off characteristic deteriorates significantly. Therefore, in order to make the slope of the diffusion distribution larger than 0.139 (for example, 0.14 or more), the in-plane pitch variation is preferably suppressed to less than 7.5%.

As described above, it was also confirmed that the in-plane pitch variation is preferably less than 7.5%, more preferably 5.0% or less, based on the measured data. The results are consistent with the simulation results of fig. 12.

In fig. 11 to 19, although the study is focused on the Y direction of the microlens array 10, the same result can be obtained also in the X direction, and the same cut-off characteristic as in the Y direction can be obtained. In the microlens array 10, by making both ends in the X direction and the Y direction excepting both endsAverage pitch deviation (σ) from all pitches of regions other than 25% _p ) Less than 7.5%, appropriate cut-off characteristics can be obtained. When light is diffused into a rectangular region, a projected image with less blurring can be obtained.

As described above, in the microlens array 10, the depth or height position of the aspherical lens 13 is sufficiently shifted. By suppressing the average pitch variation with respect to the entire pitch of a predetermined region (region excluding 25% of both ends) of the aspherical lens 13 in the plane to less than 7.5% in addition to the variation in the depth or height direction, the microlens array 10 having a good cut-off characteristic with suppressing a diffraction bright point is realized.

< application example of microlens array >

Fig. 20 is a schematic diagram of a projection apparatus 20 to which the microlens array 10 of the embodiment is applied. The projection device 20 includes a light source 21, a lens 22, and a microlens array 10. The Light source 21 is, for example, a Light Emitting Diode (LED). The light emitted from the light source 21 is collimated into parallel light by the lens 22 and enters the microlens array 10. The microlens array 10 is arranged such that a first surface 101 of the array on which the aspherical lenses 13 having concave surfaces are formed is a light incident side. In this example, the microlens array 10 is used as a diffusion plate.

The microlens array 10 diffuses the incident parallel light in the X direction and the Y direction with a predetermined FOV, and projects the diffused light onto the screen 25. When a laser light source is used instead of the LED as the light source, the collimating lens 22 may be omitted. When a color projection image is obtained, the microlens arrays 10 may be arranged for each of the red light source, the green light source, and the blue light source, and the light emitted from each microlens array 10 may be combined by a prism or the like and projected onto the screen 25.

In the microlens array 10, the center positions of the plurality of aspherical lenses 13 (see fig. 2) formed on the first surface 101 are shifted in the direction (Z direction) orthogonal to the first surface 101, and are arranged substantially regularly in the plane (X-Y plane) of the first surface 101. In the region other than 25% of both ends in the plane of the first surface 101 of the aspherical lens 13, the pitch shift is suppressed to less than 7.5%, and more preferably 5.0% or less, and therefore, a projected image with a steep diffusion distribution and little blur can be obtained. Further, the Z-directional deviation of the aspherical lens 13 suppresses diffraction spots, and a uniform intensity distribution can be obtained.

The present invention has been described above based on specific configuration examples, but the present invention is not limited to the above configuration examples. Each aspherical lens 13 of the microlens array 10 may be a convex lens having a paraboloid. In this case, the vertex position of the convex lens is shifted, and the pitch shift in the plane is suppressed to less than 7.5%. The microlens array including the array of convex aspherical lenses 13 can be manufactured from a resin or the like using the microlens array 10 manufactured in the embodiment as a mold.

The microlens array 10 of the embodiment can be applied not only to a projection apparatus but also to an illumination apparatus, an imaging system, and the like. The wavelength selectivity may be obtained by adjusting the pitch itself while suppressing the pitch variation of the aspherical lenses in the plane. In this case, since light having a specific wavelength can be diffused, it is suitably applied to a color projection apparatus.

Description of the reference symbols

10. A 10A microlens array;

11. a substrate;

13. an aspherical lens;

14. a center;

20. a projection device;

21. a light source;

22. a lens;

25. a screen;

101. a first side.

Claims (10)

1. A microlens array having:

a substrate that is transparent to the wavelength of use; and

a plurality of aspherical lenses formed on the first surface of the base material,

the center of the aspherical lens is at two or more different positions in a direction orthogonal to the first surface,

in the plane of the first surface, an average pitch deviation of a region excluding 25% of both ends of the aspherical lenses arranged in an arbitrary one-dimensional direction with respect to the entire pitch is less than 7.5%.

2. The microlens array of claim 1,

the aspheric lens is configured as a square grid,

the pitch deviation is less than 7.5% in a first direction and a second direction orthogonal to each other in a plane of the first surface, respectively.

3. The microlens array according to claim 1 or 2,

the pitch deviation is 5% or less.

4. The microlens array according to any one of claims 1 to 3,

a value σ/μ obtained by dividing a value of 1 σ when the central position of the aspherical lens in the direction orthogonal to the first surface follows a normal distribution by the average value μ is larger than 0.027.

5. The microlens array of claim 4,

the value σ/μ obtained by dividing the value of 1 σ by the average value μ is 0.040 or more and less than 0.200.

6. The microlens array according to any one of claims 1 to 5,

when an average light amount of the microlens array in which a diffusion angle of diffused light is in a range of-10 degrees to +10 degrees is normalized to 1 and relative intensity is plotted as a function of the diffusion angle, a slope between a value of the relative intensity of 0.2 and 0.8 is 0.14 or more.

7. The microlens array according to any one of claims 1 to 6,

when the average light amount of the microlens array in which the diffusion angle of diffused light is in the range of-10 degrees to +10 degrees is normalized to 1 and the relative intensity is plotted as a function of the diffusion angle, the maximum relative intensity in the angular range in which the value of the relative intensity is 0.5 or more is 1.2 or less.

8. The microlens array according to any one of claims 1 to 7,

the aspherical lenses disposed on the first surface are continuous without a flat surface between aspherical lenses adjacent to each other.

9. A projection apparatus has:

a light source; and

the microlens array of any one of claims 1 to 8 disposed on an exit side of the light source,

the microlens array diffuses and projects light emitted from the light source.

10. The projection apparatus according to claim 9,

the aspherical lens is a concave lens, and the microlens array is arranged such that the first surface is a light source side.

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