JP2006189676A - Lens array and optical equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens array with less graininess, and also, which hardly generate a pattern having a sense of incongruity. <P>SOLUTION: The lens array 3 includes a plurality of 1st lens parts M<SB>2.4</SB>and M<SB>2.6</SB>which are irregularly arranged, and at least one 2nd lens part M<SB>N2.4</SB>. Each 1st lens part is formed in a position within a prescribed extent centering one of a plurality of regularly arranged virtual points (white circle), and also, around a 1st dot (black dot) having a one-to-one correspondence relation with the virtual point, and also, the 2nd lens part is formed around a 2nd dot (black dot) having no one-to-one correspondence relation with the virtual point. Alternatively, the 2nd lens part occasionally exists beyond the prescribed extent. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a lens array used as a focusing screen of a camera.

As a focusing plate of a camera, a diffusing plate configured by regularly arranging microlenses on a plane may be used (see Patent Document 1). In such a diffuser plate, spread corresponding to the F-number of the microlens due to divergence after being condensed by the microlens, spread due to diffraction of the microlens itself, and discrete due to diffraction due to the regular arrangement of the microlenses. The light distribution characteristic is determined by the total light amount distribution.
Therefore, with such a diffuser plate, it can be determined as image blur when the focus of the photographic lens deviates from the surface of the diffuser plate, which is the focal plane, and the function as a focus plate is fully achieved, but the blur image has a diffraction pattern. Therefore, there is a drawback that an unnatural image is observed. For example, when observing a subject that shines in a dot shape, a multi-point diffraction pattern-like blurred image appears, and when a general subject is observed, a two-line blurred image appears due to the influence of the diffraction pattern.

As a device for making a blurred image of a diffuser plate in which microlenses are regularly arranged on a plane more natural, a diffuser plate in which microlenses are randomly or irregularly arranged has been proposed (Patent Document 2). reference). Specifically, as shown in FIG. 7, the center position of the microlens is randomly determined within a predetermined range centered on each lattice point of the virtual lattice points On _{/ m} regularly arranged. As shown in the drawing, randomly arranged microlenses M _{n · m} (only the center position is indicated by dots in the figure) are obtained.
JP-A-5-53174 (paragraph 0002, FIG. 23, etc.) Japanese Patent No. 2503485 (Claims, FIGS. 1 to 5 etc.)

  However, when the microlenses are randomly arranged, even if the arrangement range is limited as proposed in Patent Document 2, a portion where the distance between the centers of adjacent microlenses becomes large is generated. In this case, the image may appear to have coarse graininess, or some image unevenness (such as wrinkles) may be connected macroscopically and look like a pattern.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a lens array that has little graininess and is less likely to cause an uncomfortable pattern so that a natural image can be observed.

  The lens array of the present invention as one aspect includes a plurality of first lens portions and at least one second lens portion that are irregularly arranged. And each 1st lens part is a position within the predetermined range centering on any one among several virtual points arranged regularly, and has a one-to-one correspondence with this virtual point. The second lens portion is formed around the first point, and the second lens portion is formed around the second point having no corresponding relationship.

  The lens array of the present invention as another aspect includes a plurality of first lens portions and second lens portions that are irregularly arranged. Each first lens portion is formed around a first point existing within a predetermined range centered on one of a plurality of regularly arranged virtual points, and the second lens portion. Is formed around a second point existing outside the predetermined range.

  Furthermore, the lens array of the present invention as another aspect includes a plurality of first lens portions and second lens portions that are irregularly arranged. Each first lens portion is formed in a first polygonal shape, and the second lens portion has a second polygonal shape different from the first polygonal shape.

  As another aspect, the method of manufacturing a lens array having a plurality of irregularly arranged first lens portions and second lens portions according to the present invention includes a plurality of regularly arranged virtual points. A first step of determining the center position of each first lens unit based on the distance between the centers of two first lens units adjacent to each other or from the center to the boundary of each first lens unit And a third step of determining the center position of the second lens unit based on the distance.

  According to the present invention, the center position is determined based on the regularly arranged virtual points (i.e., the center position exists within a predetermined range centered on the virtual point having a one-to-one correspondence with the virtual point, A lens array having a second lens portion other than the first lens portions that are irregularly arranged (or formed in a common polygonal shape) is formed, so that the lens is composed only of the first lens portion. A lens array in which the inconvenience caused by the array is eliminated by the second lens unit can be realized.

  Specifically, with the first lens unit alone, it is possible to eliminate the drawbacks that the graininess is conspicuous and the image unevenness such as blurring appears as an uncomfortable pattern.

  Before describing the embodiment of the present invention, the principle of generating a grainy and uncomfortable pattern when the focusing screen, which is a microlens array, is viewed through the finder optical system of the camera will be described with reference to FIGS. To do. A pattern having graininess and a sense of incongruity is one in which the partial wrinkling of the focusing screen when viewed through the viewfinder optical system is observed in black grains or as a pattern.

  FIG. 6 shows an example of a microlens array 30 in which microlenses (centers thereof) are randomly or irregularly distributed around each lattice point of regularly arranged virtual lattice points. Here, when the pitch of the virtual lattice point O shown in FIG. 7 is P and the coefficient is K, the center position of each microlens is a circle determined by a radius r = K · P centered on the virtual lattice point On · m. Are arranged randomly or irregularly within the range (predetermined range). The coefficient K is a value that maximizes 0.2 to 0.3. That is, the predetermined range is a range of radius r ≦ 0.3P with the virtual lattice point as the center.

  When the center positions of the microlenses are varied randomly or irregularly in this way, the distance between the microlenses (center-to-center distance) takes various values as shown in FIG. For example, when the radius r = 0.3P, the maximum is 1.6P and the minimum is 0.4P.

FIG. 5 shows a cross-sectional shape of a microlens array 30 in which microlenses are irregularly arranged. The distance between the centers of the microlenses 31 and 32 and the distance between the centers of the microlenses 33 and 34 are standard distances (for example, 20 μm), but the distance between the centers of the microlenses 32 and 33 is the standard distance. Bigger than In this case, when the distance from the center of the microlens of interest (here, the microlens 33) to the boundary with the adjacent microlens 32 is X and the radius of curvature of the microlens 33 is Rc, the boundary The inclination θ of the tangent line of the microlens 33 at
θ = sin ⁻¹ (X / Rc)
It is represented by Accordingly, the light beam 43 that is vertically incident near the boundary of the microlens 33 is refracted on the surface of the microlens 33, and when the refractive index of the material of the microlens array 30 is N,
Δ = θ−sin ⁻¹ (N · sin θ)
Only deflected. Here, Δ represents the deflection angle.

If the deflection angle Δ (for example, when fe is the focal length of the eyepiece lens, the angle represented by tan ⁻¹ (2 / fe)) is large, the finder optical system causes the image to be distracted. The part appears to be blackish, and the graininess is conspicuous, or some image irregularities are connected macroscopically and look like scratches or defects.

  In other words, the greater the distance X from the center of the microlens of interest to the boundary with the adjacent microlens, the greater the deflection angle Δ of the light incident on the microlens, which is affected by the viewfinder optical system and Does not reach the eyes.

  Therefore, if the distance X from the center of the microlens of interest to the boundary of the microlens is evaluated, it is possible to evaluate the easiness of being cut.

In FIG. 6, when the target microlens is M _{2 · 4} , the adjacent microlenses M _{2 · 6} , M _{2 · 5} , M _{2 · 3} , M _{2 · 2} , M _{1 · 3} , M The shape of the boundary between _{1 and 5} is a regular hexagon when these microlenses are regularly arranged, but deformed when they are randomly or irregularly arranged as described above. Hexagonal.

A line segment L _{2 · 4−2 · 6 obtained} by projecting the boundary between the micro lenses M _{2 · 4} and M _{2 · 6} (curve having a curvature in a direction perpendicular to the paper surface of the drawing) onto a plane parallel to the paper surface of the drawing is It passes through the midpoint of the line segment M2 _{, 4-2, 6} that connects the center of the microlens M2 _{, 4 and} the center of the microlens M2 _{, 6} to the line segment M2 _{, 4-2, 6} It is an orthogonal line segment and is determined if the coordinates of each point of the microlens are given.

Although the apex of the deformed hexagonal hits the farthest position on the boundary from the center of the microlens M _{2 · 4,} the coordinates of the position and the line segment L _{2 · 4-2 · 6,} the microlens M _{2 · 4} This is the intersection of the line segment L _{2 · 4 · 1 · 5} , which is obtained by projecting the boundary of M _{1 · 5} onto a plane parallel to the paper surface of the figure, and is obtained by calculation.

Therefore, the distance X between the center of the microlenses M _{2 and 4} and the apex position of the deformed hexagon is determined if the coordinates of each point of the microlens are given, and whether or not the distortion occurs at that portion. Can be evaluated. In FIG. 6, the distance X between the center of the micro lens M _{2 · 4} and the apex on the side of the micro lens M _{2 · 6} and M _{1 · 5} is a predetermined threshold (for example, the pitch of the virtual lattice points is P, micro When the radius of curvature of the lens is Rc, it is larger than (a distance expressed by (0.5 + 0.2 · (Rc / 40) ⁴ ) · P), and it can be determined that the warp tends to occur here.

FIG. 1 shows a plan view of a microlens array that is Embodiment 1 of the present invention. As shown in FIG. 6, the microlens array 3 is centered in a range of radius r = 0.3P centering on each lattice point (indicated by a white circle in the figure) of regularly arranged virtual lattice points. A plurality of first microlenses (first lens portions) M _{2 · 4} , M _{2 · 6} , M _{2 ·} having a deformed hexagonal shape whose positions (indicated by black dots in the figure) are determined randomly or irregularly ₅ , M _{2 · 2} , M _{1 · 3} , M _{1 · 5,} and a second microlens (second lens portion) M _{N2 · 4} having a deformed pentagonal shape indicated by a dotted line in the figure .

  Here, the first point, which is the center position of each first microlens, has a one-to-one correspondence with each virtual lattice point. Whether or not each first point has such a correspondence relationship is whether or not the center of the radius r = 0.3P including each first point substantially coincides with each virtual lattice point. This can be determined by verification. On the other hand, the second point, which is the center position of the second microlens, does not have a corresponding relationship with such a virtual lattice point, and is included in the range of the radius r = 0.3P in this embodiment. There is no point. However, the second point may be included in the range of radius r = 0.3P as long as it does not have a corresponding relationship with the virtual lattice point.

Here, in this embodiment, the deformation hexagonal microlenses M _{2 · 4, which} are determined to generate the distortion described in FIG. 6, are positioned at the apex positions on the microlenses M _{2 · 6} and M _{1 · 5} side. This corresponds to the addition of two microlenses M _{N2 · 4} . By adding the second microlens M _{N2 · 4} , a portion where the warp was likely to occur without this is filled, and the occurrence of the warp is prevented.

  As described above, the distance between the center of each first microlens and the apex of the deformed hexagon of the microlens is evaluated, and it is determined that the tilt is likely to occur, that is, the distance is larger than the threshold value. In this case, if a second microlens is added so as to include or include the vertex position, the occurrence of warpage can be prevented over the entire surface of the microlens array 3.

  As described above, in the configuration in which the first microlenses are arranged at random positions around the regularly arranged virtual lattice points, the number on the data is two-dimensional for each first microlens. Therefore, if the calculation for the evaluation is sequentially performed for each first microlens, processing by a computer program is possible even if the number of the first microlenses is large.

  FIG. 2 shows a flow of a microlens design method (manufacturing method) of this embodiment including the evaluation calculation.

  In step (abbreviated as S in the figure) 1, a plurality of regularly arranged virtual lattice points as shown in FIG. 7 are set.

  Next, in step 2, a range of radius r = 0.3P centering on each virtual lattice point is set for each virtual lattice point so that the bias is reduced as a whole of the microlens array, that is, a so-called probability. A first point which is the center position of each first microlens is distributed randomly or irregularly. Then, the boundary shape (deformed hexagonal shape) of each first microlens centered on the first point is determined.

  Next, in step 3, as described above, the distance between the center of each first microlens and the apex on the boundary of the microlens is calculated, and it is determined (evaluation) whether the distance is greater than a threshold value. I will do it.

  In step 4, the center position of the second microlens for adding the second microlens is determined so as to include the vertex position determined that the distance is greater than the threshold value. The center position of the second microlens may be a vertex position where the distance is determined to be greater than a threshold value, or may be an appropriate position based on the vertex position.

  Further, in step 5, a mold for transferring the shape of each microlens is manufactured based on the above calculation data. When manufacturing a mold by engraving each microlens using a bite with a spherical tip, the position of the bite is controlled two-dimensionally using this data, and the entire surface of the original plate is engraved. The mold can be easily manufactured. In addition, when a mold is manufactured by providing a large number of pinholes by patterning with a resist on a metal plate and immersing this in a plating tank to grow a spherical plating layer centered on each pinhole, A resist exposure mask may be manufactured so that a pinhole is provided at the center position of the first and second microlenses.

  After the mold is manufactured in this way, in step 6, the shape of the microlens is transferred to the resin using the mold to manufacture a microlens array.

FIG. 3 is a plan view of a microlens array 3 ′ that is Embodiment 2 of the present invention. In this embodiment, in FIG. 6, two microlenses M _{2 · 6} , M _{1 ·} , which are adjacent to the target microlenses M _{2 · 4} and which are related to the apex of the deformed hexagon that is determined to be prone to bend. ₅ , the second centered on the midpoint of the line segment connecting the center of the microlens M _{2 · 6} and the center of the microlens M _{2 · 4} with a larger center-to-center distance with the microlens M _{2 · 4} . This corresponds to the addition of the micro lens M _{M2 · 4} .

  In the present embodiment, the first microlens has a hexagonal shape, while the second microlens has a quadrangular shape.

Similarly to the first embodiment, the first microlens (first lens portion) M _{2 · 4} , M _{2 · 6} , M _{2 · 5} , M _{2 · 2} , M _{1 · 3} , M _{1 · 5} The first point (indicated by a black dot in the figure) having a one-to-one correspondence with each regularly arranged virtual grid point (indicated by a white circle in the figure) This is a point determined randomly or irregularly within a radius r = 0.3P centering on each lattice point. On the other hand, the second point (indicated by a black dot in the figure) which is the center of the second microlens (second lens portion) M _{M2 · 4} does not have the correspondence and is not included in the range. Is a point. However, the second point may be included in the range of radius r = 0.3P as long as it does not have a corresponding relationship with the virtual lattice point.

Thus, instead of the evaluation of the distance X described in the first embodiment, the distance between the centers of the two first microlenses adjacent in the state shown in FIG. 6 is a predetermined threshold (for example, (0. 5 + 0.2 · (Rc / 40) ⁴ ) · Distance greater than (P), and if greater than the threshold, a second microlens between the first microlenses The center of the second microlens may be set at a midpoint position between the centers or an appropriate position based on the midpoint position.

Also in the present embodiment, by adding the second microlens M _{M2 · 4} , the apex portion where the warpage was likely to occur without this is filled, and the occurrence of the warpage of the portion can be prevented. Then, by performing such evaluation and addition of the second microlens on the entire microlens array, it is possible to prevent the occurrence of warpage on the entire surface of the microlens array.

When the microlens arrays described in the first and second embodiments are viewed, between the two first microlenses with the second microlens in between (for example, between M _{2 · 4 and} M _{2 · 6} , The distance between the centers of M _{2 · 5 and} M _{1 · 5 is} between the two adjacent first microlenses (for example, M _{2 · 4} -M _{2 · 2)} without interposing the second microlens between them. it can be seen larger than the center distance between between and _{M 1 · 3 -M 2 · 2} ).

  FIG. 4 shows a single-lens reflex digital camera using the microlens array 3 (3 ') described in the above embodiments as a focusing screen (diffuser plate).

  The interchangeable lens 1 can be attached to the camera body 2 via a mount. The light transmitted through the interchangeable lens 1 is reflected by the quick return mirror 21 and forms an image on the focusing screen 3 during viewfinder observation. The light imaged on the focusing screen 3 is guided to the observer's eye E through the penta roof prism 22 and the eyepiece 23 constituting the finder optical system while spreading by the diffusing action of the focusing screen 3. At the time of photographing, the quick return mirror 21 is retracted from the photographing optical path, and the light from the interchangeable lens 1 forms an image on the image sensor 25 such as a CCD sensor or a CMOS sensor via a low-pass filter 24 and is photoelectrically converted. The signal from the image sensor 25 is subjected to various processes by a signal processing circuit (not shown) to generate an image signal. This image signal is displayed on a display (not shown) provided in the camera body 2 or recorded on a recording medium (not shown) such as a semiconductor memory.

  According to the present embodiment, it is possible to observe a high-quality finder image without observing the graininess of the focusing screen 3 or showing a pattern with a sense of incongruity such as squinting in finder observation. In particular, it is possible to reduce graininess, which is often noticeable when an interchangeable lens having a small F-number and a small diameter is attached to the camera body.

  In the present embodiment, a camera using a microlens array as a focusing screen has been described. However, the present invention is also applicable to an optical device other than a camera that uses a lens array for purposes other than the focusing screen. be able to.

1 is a plan view of a microlens array that is Embodiment 1 of the present invention. FIG. 3 is a flowchart showing a manufacturing process of the microlens array of the first embodiment. 1 is a plan view of a microlens array that is Embodiment 1 of the present invention. FIG. Schematic of the single-lens reflex digital camera which is Example 3 of this invention. Explanatory drawing which shows the generation principle of the graininess in a microlens array. Explanatory drawing which shows the evaluation principle of the generation | occurrence | production place of the distortion in a micro lens array. The figure which shows the virtual lattice point arrange | positioned regularly. The figure which shows the micro lens (center position) irregularly arrange | positioned.

Explanation of symbols

1 Interchangeable lens 2 Camera body 3, 3 'Micro lens array (focus plate)
25... Image sensor 31, 32, 33, 34, M _{n. m} micro lens

Claims (11)

A plurality of irregularly arranged first lens portions and at least one second lens portion;
Each of the first lens portions is a position within a predetermined range centered on any one of a plurality of regularly arranged virtual points, and has a one-to-one correspondence relationship with the virtual points. Formed around the point of 1,
The lens array, wherein the second lens portion is formed around a second point having no correspondence. A plurality of irregularly arranged first lens portions and second lens portions;
Each of the first lens portions is formed around a first point existing within a predetermined range centered on one of a plurality of regularly arranged virtual points,
The lens array, wherein the second lens portion is formed around a second point existing outside the predetermined range. 3. The lens array according to claim 1, wherein the predetermined range is a range of the following radius r centered on the first point. 4.
r≤0.3P
Here, P is the arrangement pitch of the virtual points. A plurality of irregularly arranged first lens portions and second lens portions;
Each of the first lens portions is formed in a first polygonal shape,
The lens array, wherein the second lens portion has a second polygonal shape different from the first polygonal shape.   The center-to-center distance between the two first lens parts sandwiching the second lens part is larger than the center-to-center distance between the two first lens parts adjacent to each other. The lens array according to any one of 1 to 4.   6. The lens array according to claim 1, wherein the lens array has an action of diffusing and emitting incident light.   An optical apparatus comprising the lens array according to claim 1. A focusing screen which is the lens array according to any one of claims 1 to 6,
An optical system for guiding light emitted from the focusing screen to the eyes of an observer. A method of manufacturing a lens array having a plurality of irregularly arranged first lens portions and second lens portions,
A first step of determining a center position of each of the first lens units based on a plurality of regularly arranged virtual points;
A second step of obtaining a distance between the centers of the two first lens portions adjacent to each other or a distance from the center to the boundary in each of the first lens portions;
And a third step of determining a center position of the second lens portion based on the distance.   In the third step, when the center-to-center distance between the two first lens parts is larger than a predetermined value, the center position of the second lens part arranged between the two first lens parts is determined. The method of manufacturing a lens array according to claim 9. In the third step, the center of the second lens unit disposed between the first lens unit having a distance from the center to the boundary larger than a predetermined value and the first lens unit adjacent to the first lens unit. The lens array manufacturing method according to claim 9, wherein the position is determined.