JP4366107B2 - Optical device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical device having a member in an optical path.
[0002]
[Prior art]
Patent Document 1 is an example of disclosure in which a partition wall is provided for optical path separation in a focus detection unit of a single-lens reflex camera. Providing a partition wall in the focus detection unit has an advantage that the focus detection visual field can be densely arranged because the interval between the plurality of optical paths can be narrowed.
[0003]
Patent Document 2 is a disclosure example in which a partition for optical path separation is provided in a compound eye imaging apparatus. When the compound eye imaging device is provided with a partition wall, the optical axis interval of the compound eyes can be arbitrarily set. In addition, since the distance between the plurality of optical paths can be reduced, there is an advantage that the parallax generated by the compound eye can be reduced and the registration shift generated depending on the distance of the object can be suppressed.
[0004]
Patent Document 3 discloses a technique for forming a prism group for controlling the reflection angle of light rays on the side surface of an optical path.
[0005]
[Patent Document 1]
JP-A-1-282513
[Patent Document 2]
JP 7-154663 A
[Patent Document 3]
JP 9-269405 A
[0006]
[Problems to be solved by the invention]
The wall surface for separating the optical path of the optical system from the external space should be coated with light absorption, or the reflection of light, such as making the wall surface rough, can be kept low, or the reflected light can be scattered. The device is made to control and make it inconspicuous. However, it is difficult to sufficiently suppress reflection by painting, and the ghosting can be suppressed at a high level with conventional methods, such as simply changing the direction of reflected light can cause new ghosts. There was no.
[0007]
In Patent Document 3, a technique for forming a prism group for controlling the reflection angle of light rays on the side surface of an optical path is used. In the technique of Patent Document 1 described above, the surface reflection of a light shielding member having a shape whose longitudinal direction is the optical axis direction is sensor direction. Therefore, ghosts and flares are likely to occur, and as a result, it is difficult to obtain high focus detection accuracy.
[0008]
Further, the technique disclosed in Patent Document 2 described above has a problem that ghosts and flares are likely to occur due to surface reflection at a partition wall for optical path separation, and as a result, it is difficult to obtain a high-quality image.
[0009]
The present invention has been made in view of such conventional problems, and an object thereof is to reduce reflected light and scattered light on the wall surface of the optical path.
[0010]
[Means for Solving the Problems]
In order to achieve the first object, the invention according to claim 1 is arranged between a plurality of optical paths that pass through the split field lens and enter the sensor of the focus detection field of view, and prevents crossing of the light beams between the optical paths. In the optical device having the two optical path separating members, the opposing wall surfaces of the two optical path separating members absorb light in a transparent medium having a mirror layer having a mirror surface and a refractive index substantially equal to that of the prism layer. By providing a light absorbing layer in which the body is dispersed so that there is no air layer between each other, the light incident on the inside of the prism layer is incident from the mirror surface facing the incident direction and refracted, and then the light absorption An optical path separating member that is guided to a layer or is totally reflected by a mirror surface that is not opposed to the incident direction of light after being refracted and guided to the light absorption layer, and the prism layer is disposed on a wall surface other than the facing wall surface. Formed and not.
[0011]
(Function)
According to invention of Claim 1 thru | or 2, it is possible to reduce the reflected light in the wall surface of an optical path.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
1 to 9 are diagrams for explaining a first embodiment of the present invention. In the first embodiment, the wall structure of the optical path used in the focus detection unit of the single-lens reflex camera is taken as an example.
[0013]
FIG. 1 is a cross-sectional view of a focus detection unit having a plurality of focus detection fields, and FIG. 2 is an exploded perspective view thereof. The focus detection unit is housed in the lower part of the mirror box of the single-lens reflex camera, and the focus detection light beam is guided through the main mirror and the sub mirror.
[0014]
In FIGS. 1 and 2, L2 is an optical axis of an objective lens (not shown) that is folded back by a submirror, 10 is located behind the objective lens (not shown), and separates a focus detection light beam to remove an unnecessary light beam. A field mask that serves as a mask, 20 is a split field lens that guides an image formed on the primary imaging plane to a sensor that is a light receiving means, and 30 is a light beam and a second focus of a central focus detection field that is a first focus detection field. This is a light shielding plate for separating the light flux in the peripheral focus detection visual field, which is the detection visual field, and preventing the light flux other than the effective light flux corresponding to each focus detection visual field from entering the sensor.
[0015]
40 is a mirror that reflects light on the surface to bend the focus detection light beam incident on the focus detection unit toward the sensor, 50 is an infrared cut filter for removing infrared light, and 60 is for separating the focus detection light beam. The aperture stop 70 is a re-imaging lens having a plurality of pairs of lenses for forming an image on the sensor.
[0016]
Reference numeral 80 denotes a sensor holder for holding the sensor, and 90 denotes a sensor as a light receiving means for detecting an image for performing a focus detection operation, and a plurality of pairs of line sensors are formed.
[0017]
Reference numeral 100 denotes a light shielding member having an aperture through which only an effective light beam necessary for focus detection passes in order to remove as much as possible the effective light beam corresponding to each focus detection field of view, and 110 denotes a focus detection unit and a focus detection unit of the camera. A light shielding sheet 120 that closes the gap between the mounting portions is a main body block that holds each component constituting the focus detection unit and shields external light.
[0018]
Here, the central focus detection field for focus detection of the region on the optical axis, which is the first focus detection field, passes through the aperture 14-1 of the field mask and the lens 21-1 of the divided field lens, and then the perforated diaphragm 60. Of the re-imaging lens corresponding to the opening 62-1, and the light path is guided to the light receiving portions 91-1 to 91-4 as the light receiving elements of the sensor 90. ing.
[0019]
In addition, the peripheral focus detection visual field for detecting the focal point in the area outside the optical axis, which is the second focus detection visual field, passes through the aperture 14-2 of the field mask and the lens 21-2 of the split field lens, An optical path that passes through the opening 62-5 and is guided to the light receiving portions 91-11 to 91-12 of the sensor 90 by the lens portion of the re-imaging lens corresponding to the opening 62-5.
[0020]
In the above configuration, the main body block 120 is provided with various positioning portions for positioning various focus detection unit components and a fixing portion for fixing. First, the infrared cut filter 50 is located on the right side of FIG. Thus, the positioning is fixed to the main body block 120.
[0021]
The light shielding plate 30 is adhered and fixed to the inside of the main body block 120 by the light shielding plate positioning fixing portion 31 and the light shielding plate positioning fixing portion 123 of the main body block 120.
[0022]
Further, the light shielding plate 30 has a wall surface 32 and a wall surface 33 for preventing an unnecessary light beam other than an effective light beam in each focus detection visual field that has passed through the split field lens 20 from entering a sensor in another focus detection visual field. Between the wall surface 32 and the wall surface 33, an opening 34 for allowing the photometric light beam to pass is formed. The light shielding plate 30 can narrow the distance between the light flux in the central focus detection visual field and the light flux in the peripheral focus detection visual field, so that the focus detection visual field can be densely arranged.
[0023]
After the position adjustment is performed, the divided field lens 20 is bonded and fixed to the main body block 120 by the divided field lens fixing portion 124 of the main body block 120.
[0024]
The field mask 10 is fixed to the main body block 120 by engaging the pair of field mask fixing elastic claws 10-1 with the pair of field mask fixing holes 127 of the main body block 120.
[0025]
The light shielding sheet 110 is fixed to the main body block 120 by being sandwiched between the field mask 10 and the main body block 120. Further, the rear light shielding part 112 of the light shielding sheet 110 is fixed by the light shielding sheet rear light shielding part fixing part 129 of the main body block 120.
[0026]
The mirror 40 is positioned and fixed to the main body block 120 from the right side of FIG. On the surface of the mirror 40, a light shielding mask portion 41 having a mask shape for shielding unnecessary light fluxes for each focus detection field of view is added. As a result, when the focus detection light flux is bent with respect to the sensor, Unnecessary light flux passing through the gap between the light shielding plate 30 and the mirror 40 is shielded.
[0027]
The re-imaging lens 70 is positioned by a pair of fitting holes and is bonded and fixed to the main body block 120.
[0028]
The porous diaphragm 60 is positioned on the re-imaging lens 70 by the positioning unit 61. The porous diaphragm 60 is held between the re-imaging lens 70 and the main body block 120 and held by the main body block 120.
[0029]
As shown in Japanese Patent Laid-Open No. 3-23506, the sensor holder 80 adjusts the tilt of the sensor caused by an error in the manufacturing process of the sensor 90.
[0030]
The sensor holder 80 is fitted to a sensor holder by a pair of sensor holder fitting semi-cylindrical shafts 82 and a pair of sensor holder fitting bearing grooves 130 of the main body block 120 having a pair of identical central axes for positioning adjustment. The body block 120 is swingably positioned around the semi-cylindrical shaft 82. Then, after various adjustments such as sensor tilt adjustment are performed, the main body block 120 is bonded and fixed.
[0031]
The sensor 90 can move freely within the sensor bonding surface with respect to the sensor holder 80. The sensor 90 is adhesively fixed to the sensor holder 80 after various adjustments such as sensor tilt adjustment are performed together with the sensor holder 80.
[0032]
The light shielding member 100 is bonded and fixed to the sensor holder 80.
[0033]
FIG. 3 is a diagram illustrating a part of an optical path diagram of the focus detection unit. FIG. 3 shows a cross section including the photographing optical axis of the single-lens reflex camera, and the folding of the optical path by the mirror 40 is developed. Further, in the figure, only a part of the ghost light beam is illustrated, and the effective light beam is not illustrated.
[0034]
In the focus detection unit of the present embodiment, the light beam incident on the focus detection unit passes through the field mask 10 shown in FIG. 2, passes through the split field lens 20, passes through the infrared cut filter 50, and passes through the aperture stop 60. , Passes through the re-imaging lens 70, and enters the sensor 90 to detect the focus.
[0035]
In FIG. 3, ghost light beams 160 and 161 are reflected by the wall surface 32, and the ghost light beam 162 is reflected by the inner wall of the main body block 120. The ghost beam 162 can be cut almost in an objective lens (not shown) or a mirror box of a single-lens reflex camera. On the other hand, it is difficult to cut the ghost beams 160 and 161 on the objective lens side, and in order not to deteriorate the focus detection accuracy, it is extremely important to suppress the reflection on the wall surface 32 to be low.
[0036]
FIG. 4 is a detailed view showing the structure of the wall surface 32. The wall surface 32 is composed of two layers of a prism layer 32a and a light absorption layer 32b, and effectively reduces the reflected light on the prism layer side. The prism layer 32a is composed of a large number of triangular prisms having mirror-like slopes, and the pitch is preferably about 10 μm to 300 μm and the apex angle is preferably 60 degrees to 130 degrees. In the structure shown in FIG. 4, the apex angle is 90 degrees. . It is made of a transparent resin such as polycarbonate, acrylic, polyester, or PET. Or the composite body which produced and joined the prism layer and the base material of the flat plate with a different material may be sufficient. The reason why all the prism surfaces are mirror surfaces is to transmit or reflect incident light without scattering.
[0037]
The two wall surfaces 32 and 33 of the light shielding plate 30 have the same structure, and the prism layer is formed only on the opposite side of the wall surfaces 32 and 33, respectively. This is because the surfaces of the wall surfaces 32 and 33 on which the prism layer is not formed are not incident on the light receiving portion of the sensor even if there is reflected light, and this is not a problem.
[0038]
One light absorption layer 32b has a structure in which a sufficient amount of light absorber is dispersed in a transparent medium such as a tree species. The prism layer 32a can be printed, painted, or joined by a resin layer. It is added to the back side. The light absorber is composed of, for example, carbon particles. When the prism layer is a composite of two resin layers, this light absorption layer may be a base material that supports the prism layer.
[0039]
There is no air layer between the prism layer 32a and the light absorption layer 32b, and the refractive indexes of both are about 1.5, which are substantially equal. Therefore, the light incident on the prism layer 32a is guided to the light absorption layer 32b with almost no reflection at the interface between the prism layer 32a and the light absorption layer 32b, is attenuated in the light absorption layer 32b, and the light energy is converted into heat. Converted.
[0040]
Rays 1 and 5 shown in FIG. 4 are obtained by extracting some of the ghost beams 160 and 161 shown in FIG. The light beam 1 is incident from the mirror surface 3 facing the light incident direction of the prism layer 32a, refracted by the refractive index difference between the resin and air, and then guided to the light absorption layer 32b. Similarly, the light beam 5 is incident from the mirror surface 3 facing the light incident direction, refracted at the interface, and then the mirror surface not facing the light incident direction. 4 In FIG. 5, the light is totally reflected by the effect of the refractive index difference with air and guided to the light absorption layer 32b.
[0041]
FIG. 9 is a graph showing the reflectivity of Fresnel reflection occurring at the interface between air and resin as a function of incident angle. Rp represents the reflectance of P-polarized light, and Rs represents the reflectance of S change. When the incident angle is zero degrees, that is, normal incidence, the reflectivity is about 4%. However, at an incident angle of 80 degrees, the P-polarized light increases by 30% and the S-polarized light increases by about 50%. The reflectivity is about 40%.
[0042]
In the behavior of the light beam as described above, the Fresnel reflection due to the difference in refractive index occurs only when the light beam enters the mirror surface 3, and the optical path does not branch at the other interface. Since the incident angle to the inclined surface 3 is as small as about 0 to 40 degrees, it can be seen from FIG. 9 that the reflectance is about several percent. Moreover, since the surface reflected light 2 on the mirror surface 3 does not go in the direction of the re-imaging lens 70 as shown in FIG. 4, they do not generate ghost or flare. Therefore, a highly accurate focus detection result can be obtained.
[0043]
However, in the case where the mirror 40 for bending the optical path is arranged as in the focus detection unit of the present embodiment, the surface reflected light on the mirror surface 3 does not pass through the mirror 40 and is directly re-imaging lens. It is necessary to set so that it does not go to 70. As indicated by an arrow A in FIG. 1, the reflected light is not directed to the re-imaging lens 70 by having a ridge line in a direction that bisects the optical axis folded by the mirror and the original optical axis. You can
[0044]
Further, as indicated by an arrow B in FIG. 5, ridge lines may be formed concentrically around the point P1. With such a configuration, a Fresnel lens manufacturing method can be used for mold manufacturing and resin molding. The focus detection unit shown in FIG. 5 is the same as the focus detection unit shown in FIG. 1 except for the direction of the ridgeline of the light shielding plate 30.
[0045]
The example in which the prism layer 32a and the light absorption layer 32b are separately formed has been described above. However, if a light absorber is contained inside the prism layer 32a, the prism itself can also absorb light by its action. FIG. 6 is a diagram showing this structure. The prism layer 32c having a large number of specular slopes 6 and 7 is formed by mixing a light absorber such as carbon particles with a transparent resin such as polycarbonate, acrylic, polyester, or PET. The light beam 8 is incident from the mirror surface 6 facing the light incident direction of the prism layer 32c, refracted by the refractive index difference between the resin and air, and then absorbed in the prism layer 32c. Similarly, the light ray 9 is incident from the mirror surface 6 facing the light incident direction, refracted at the interface, and then attenuates the refractive index difference from the air at the mirror surface 7 not facing the light incident direction. It is totally reflected by the action and absorbed inside the prism layer 32c.
[0046]
Further, as shown in FIG. 7, the slope 11 and the slope 12 may have different slopes in the shape of the prism constituting the prism layer. When the light beam from the split field lens 20 directly hits the inclined surface 12, the incident angle to the inclined surface 12 becomes large, so that a considerably strong reflection occurs due to the Fresnel reflection characteristic shown in FIG. Therefore, what is important here is to set an angle at which such reflected light is not generated, and even if reflected light is generated, it is taken again from the inclined surface 12 into the prism layer 32d and is not made ghost light. is there.
[0047]
FIG. 8 is a view in which such a viewpoint is further advanced, and the tip portion of the peak of the prism layer 32e has a sharp edge so as not to generate ghost light, and conversely, the valley portion 13 is rounded. The surface accuracy of the slope can be improved by reducing the flow resistance of the resin.
[0048]
As described above, the shape of the prism is appropriately determined and may be variously modified. The prism layer may be an assembly of prisms having different shapes.
[0049]
As described above, when the partition using the prism layer according to the present invention is provided in the focus detection unit, the occurrence of ghosts and flares can be suppressed, and the focus detection visual field can be densely arranged without reducing the focus detection accuracy. .
[0050]
(Second Embodiment)
10 to 14 are diagrams for explaining a second embodiment of the present invention. In the second embodiment, the wall surface structure of the optical path used in the compound eye imaging apparatus is taken as an example.
[0051]
FIG. 10A is a top view illustrating a schematic configuration of the compound-eye imaging apparatus. FIG. 10B is a schematic cross-sectional view taken along line 1B-1B in FIG. FIG. 10C is a top view of the semiconductor chip 503 in FIG. FIG. 201D is a schematic cross-sectional view illustrating a state where the imaging module in FIG. 201B is connected to an external electric circuit. FIG. 14 is an exploded perspective view of the imaging module.
[0052]
10A to 10D, 560 is an infrared cut filter, 501 is a light transmissive member as a first substrate, and 506 is a light blocking property on the upper surface of the light transmissive member 501 via an infrared cut filter 560. A diaphragm light shielding layer formed by offset printing or the like, for example, 512 is a compound eye optical element having a compound eye lens composed of an infrared cut filter 560, a diaphragm light shielding layer 506 and convex lenses 600a and 600c, and a convex lens 600b and a convex lens 600d not shown. It is.
[0053]
In this embodiment, a compound eye optical element including a compound eye lens having four convex lenses is formed. However, the number of lenses is appropriately determined and is not limited to this embodiment.
[0054]
Further, 810a to 810d are diaphragm apertures formed in the diaphragm light-shielding layer 506, and it is more preferable that the lenses 600a to 600d are coaxial with the apertures 810a to 810d, respectively.
[0055]
Reference numeral 503 denotes a semiconductor chip. Reference numeral 522 denotes a spacer that defines the distance between the compound-eye optical element 512 and the semiconductor chip 503, and 509 denotes an adhesive that adheres the compound-eye optical element 512 and the semiconductor chip 503 via the spacer 522.
[0056]
Reference numeral 513 denotes an electrode pad as an external terminal for outputting a signal from a light receiving element or light emitting element such as a CMOS type image pickup device or a CCD image pickup device to the outside, and 508 prevents optical crosstalk of the four convex lenses. Therefore, the barrier ribs are formed in a space surrounded by the compound-eye optical element 512, the spacer 522, and the semiconductor chip 503. The partition wall 508 can reduce the distance between the plurality of optical paths by the compound-eye optical element 512. Therefore, the parallax generated by the compound eye can be reduced, and the registration shift generated depending on the distance of the object can be suppressed.
[0057]
Further, 516 is a microlens that increases the light collection efficiency of each light receiving element, 820a to 820d are a plurality of two-dimensionally formed light receiving element arrays on the semiconductor chip 503, and 514 converts an output signal from each light receiving element array into a digital signal. A / D conversion circuits 515 are timing generators that generate timing signals for photoelectric conversion operations of the respective light receiving element arrays. Reference numerals 822a and 822b denote light receiving elements.
[0058]
Further, reference numeral 517 denotes a multilayer printed board which is an external electric circuit board, 520 denotes a bonding wire for electrically connecting an electrode pad 513 (not shown) and an electrode pad on the multilayer printed board 517, and 521 denotes an electrode pad 513. And a heat or ultraviolet curable resin for sealing the periphery of the bonding wire 520. In the present embodiment, an epoxy resin that is a thermal ultraviolet curable resin is used.
[0059]
The light-transmitting member 501 includes a convex lens 600a such as a resin-made spherical Fresnel convex lens or a circular axisymmetric aspherical Fresnel convex lens that can correct the curvature of field particularly well as compared with a normal optical system using a continuous surface. ˜600d is formed by a method such as a replica manufacturing method, injection molding, compression molding or the like.
[0060]
Further, when it is desired to obtain a color image, a green transmission (G) filter, a red transmission (R) filter, and a blue transmission (B) filter are arranged for each convex lens 600a to 600d.
[0061]
In the semiconductor chip 503, for example, a microlens 516 that collects light on the light receiving element so that even a low-luminance object can be easily imaged, and optical crosstalk between the light passing through the convex lens 600a and the light passing through the convex lens 600c are generated. A partition wall 508 for preventing the above is formed. Actually, a partition is provided between the convex lenses and the like.
[0062]
FIG. 10D shows a multilayer printed circuit board 517 which is an external electric circuit board, a bonding wire 520 for electrically connecting the multilayer printed circuit board 517 side and the electrode pad 513, and the electrode pad 513 and the bonding wire. A thermal ultraviolet curable resin 521 for sealing the periphery of 520 is shown. By performing sealing with the adhesive 509 and the thermal ultraviolet curable resin 521, it is possible to prevent ingress of dust and intrusion of humidity in the air.
[0063]
Here, the mechanism of processing of the electric signal converted in the light receiving regions 820a to 820d of the imaging module will be described with reference to FIGS.
[0064]
FIG. 11 is a diagram showing the positional relationship between the object image of the compound eye lens mounted on the imaging module and the imaging region.
[0065]
In FIG. 11, 320 a, 320 b, 320 c and 320 d are four light receiving element arrays of the semiconductor chip 503. Here, in order to simplify the description, it is assumed that each of the light receiving element arrays 320a, 320b, 320c, and 320d has 8 × 6 pixels.
[0066]
The number of pixels can be determined as appropriate, and is not limited to this embodiment. The light receiving element arrays 320a and 320d output a G image signal, the light receiving element array 320b outputs an R image signal, and the light receiving element array 320c outputs a B image signal. The pixels in the light receiving element arrays 320a and 320d are white rectangles, the pixels in the light receiving element array 320b are hatched rectangles, and the pixels in the light receiving element arrays 320c are black rectangles.
[0067]
Reference numerals 351a, 351b, 351c, and 351d are object images. For pixel shifting, the centers 360a, 360b, 360c, and 360d of the object images 351, 352, 353, and 354 are each 1 in the direction from the center of the light receiving element array 320a, 320b, 320c, and 320d to the center 320e of the entire light receiving element array. / 4 pixels are offset.
[0068]
As a result, when each light receiving element array is back-projected onto a plane at a predetermined distance on the subject side, a pixel shift relationship is established.
[0069]
FIG. 12 is a diagram illustrating the positional relationship of pixels when the imaging region of FIG. 11 is back-projected onto an object. Also on the subject side, the backprojected images of the pixels in the light receiving element arrays 320a and 320d are white rectangles 362a, and the backprojected image of the pixels in the light receiving element arrays 320b are hatched rectangles 362b. The backprojected image of the pixel is indicated by a black rectangle 362c.
[0070]
The back-projected images of the centers 360a, 360b, 360c, and 360d of the object image overlap as a point 361, and the pixels of the light receiving element arrays 320a, 320b, 320c, and 320d are back-projected so that the centers do not overlap. . The white rectangles output the G image signal, the hatched rectangles output the R image signal, and the blacked rectangles output the R image signal. As a result, the image sensor having a Bayer color filter on the subject. Sampling equivalent to is performed.
[0071]
In comparison with an imaging system that uses a single photographic lens, if the pixel pitch of the individual imaging element is fixed, a Bayer arrangement method in which an RGBG color filter is formed on a semiconductor chip 503 as a set of 2 × 2 pixels is used. In comparison, in this method, the size of the object image is 1 / √4. Along with this, the focal length of the photographing lens is shortened to about 1 / √4 = 1/2. Therefore, it is extremely suitable for reducing the thickness of the imaging device.
[0072]
Next, the function and structure of the partition will be described in detail. FIG. 13 is a detailed view of the partition 508.
[0073]
The light beams reaching the adjacent light receiving element arrays without exiting the convex lenses 600a to 600d and entering the corresponding light receiving element arrays 820a to 820d need to be blocked by the partition 508. For example, the luminous flux that exits the convex lens 600a and reaches the light receiving element array 820c, or the luminous flux that exits the convex lens 600c and reaches the light receiving element array 820a. Therefore, in the compound eye imaging device, an antireflection structure using prisms is formed on both sides of the wall surface.
[0074]
In FIG. 13, reference numeral 204 denotes a light beam emitted from the convex lens 600a, and 205 denotes a light beam emitted from the convex lens 600c. If there is no antireflection structure, reflected light indicated by 206 or 207 is generated, and the light returns to the light receiving element array 820a or the light receiving element array 820c to become a ghost or flare. The partition wall 508 effectively removes such reflected light.
[0075]
In the figure, 201 and 202 are prism layers, and 203 is a light absorption layer. As in the first embodiment, the prism layers 201 and 202 are made of a transparent resin such as polycarbonate, acrylic, polyester, or PET. Or the composite body which produced and joined the prism layer and the base material of the flat plate with a different material may be sufficient.
[0076]
The prism layer has mirror surfaces 208 and 209 facing in the light incident direction and mirror surfaces 210 and 211 not facing in the light incident direction. The reason why the prism surfaces are mirror surfaces is to transmit or reflect incident light without scattering.
[0077]
On the other hand, the light absorption layer 203 has a structure in which a sufficient amount of light absorber is dispersed in a transparent medium such as a tree species, and the prism layer 201 is printed by a technique such as printing, painting, or joining of resin layers. And between the prism layers 202. When the prism layer is a composite of two resin layers, this light absorption layer may be a base material that supports the prism layer. Further, the light absorption layer 203 may be an adhesive layer for integrating the prism layer 201 and the prism layer 202.
[0078]
There is no air layer between the prism layers 201 and 202 and the light absorption layer 203, and the refractive index is about 1.5 for all three, which are almost equal. Therefore, the light incident on the prism layers 201 and 202 is guided to the light absorption layer 203 with almost no reflection at the interface between the prism layers 201 and 202 and the light absorption layer 203, attenuates in the light absorption layer 203, Energy is converted into heat. Therefore, it is possible to obtain a high quality image without generating ghost and flare.
[0079]
(Third embodiment)
In the third embodiment, the wall surface structure of the optical path used for the lens barrel of the lens unit is taken as an example. The lens unit is used in various optical devices such as a camera, a microscope, a telescope, and a scanner. FIG. 15 is a sectional view of a lens barrel of a lens unit for explaining a third embodiment according to the present invention.
[0080]
The lens barrel of the lens unit has a cylindrical wall surface, and an antireflection structure using a prism is formed on the wall surface. In the figure, 301 is an imaging lens, L1 is the optical axis of the imaging lens 301, and 302 is a wall surface that separates the optical path from the external space.
[0081]
When the light beam hitting the wall surface is reflected after exiting the imaging lens 301, it becomes a ghost or flare and is superimposed on the formed object image, thereby reducing the contrast of the object image. The wall 302 effectively removes such reflected light.
[0082]
In the figure, 303 is a prism layer, and 304 is a light absorption layer. As in the first embodiment, the prism layer 303 is made of a transparent resin such as polycarbonate, acrylic, polyester, or PET. Or the composite body which produced and joined the prism layer and the base material of the flat plate with a different material may be sufficient.
[0083]
The prism layer has a mirror surface facing the light incident direction and a mirror surface not facing the light incident direction. The reason why the prism surfaces are mirror surfaces is to transmit or reflect incident light without scattering.
[0084]
The light absorption layer 203 has a structure in which a sufficient amount of light absorber is dispersed in a transparent medium such as a tree species, and is added to the prism layer 303 by a technique such as printing, painting, or joining of resin layers. Is done. When the prism layer is a composite of two resin layers, this light absorption layer may be a base material that supports the prism layer.
[0085]
FIGS. 16A, 16B, and 16C are views for explaining the assembly process of the wall surface.
[0086]
The wall 302 is cylindrical, but is assembled from a flat material. As shown in the plan view of FIG. 16A and the perspective view of FIG. 16B, a flat prism sheet 302 ′ serving as the wall surface of the optical path is formed as 302 ″ in FIG. 16C. Roll to end up in a closed cylinder.
[0087]
Since both the prism layer 303 and the light absorption layer 304 are made of resin, such molding is possible by utilizing their flexibility.
[0088]
There is no air layer between the prism layer 303 and the light absorption layer 304, and the refractive indexes of both are about 1.5, which are substantially equal. Therefore, the light incident on the prism layer 303 is guided to the light absorption layer 304 with almost no reflection at the interface between the prism layer 303 and the light absorption layer 304, attenuates in the light absorption layer 203, and the light energy is converted into heat. Converted. Therefore, it is possible to obtain a high-contrast object image having the original MTF characteristic of the optical system without generating ghost and flare.
[0089]
【The invention's effect】
As described above, according to the present invention, it is possible to reduce the reflected light on the wall surface of the optical path. As a result, ghosts and flares were not generated in the object image, and an object image accurately representing object information could be obtained.
[0090]
In the imaging system, the original MTF characteristic of the optical system can be obtained. In the focus detection system, high focus detection accuracy can be obtained. Further, in the compound eye imaging apparatus, a high-quality image can be obtained. Became.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a focus detection unit having a plurality of focus detection fields of view.
FIG. 2 is an exploded perspective view of the focus detection unit shown in FIG.
FIG. 3 is a diagram illustrating a part of an optical path diagram of a focus detection unit.
4 is a detailed view showing the structure of a wall surface 32. FIG.
5 is a cross-sectional view of a focus detection unit showing a modification of the structure of the wall surface 32. FIG.
FIG. 6 is a view showing a modification of the wall surface structure.
FIG. 7 is a view showing a modification of the wall surface structure.
FIG. 8 is a view showing a modified example of the structure of the wall surface.
FIG. 9 is a graph showing the reflectivity of Fresnel reflection occurring at the interface between air and resin as a function of incident angle.
10A is a top view illustrating a schematic configuration of a compound eye imaging apparatus, FIG. 10B is a schematic cross-sectional view taken along line 1B-1B in FIG. 10A, and FIG. FIG. 10D is a schematic cross-sectional view illustrating a state where the imaging module of FIG. 10B is connected to an external electric circuit.
FIG. 11 is a diagram illustrating a positional relationship between an object image of a compound eye lens and an imaging region.
12 is a diagram illustrating a positional relationship of pixels when the imaging region in FIG. 11 is back-projected onto an object.
FIG. 13 is a detailed view of a partition wall 508;
FIG. 14 is an exploded perspective view of the imaging module.
FIG. 15 is a cross-sectional view of a lens unit.
FIGS. 16A, 16B, and 16C are diagrams for explaining a process of assembling a wall surface.
[Explanation of symbols]
30 Shading plate
32a, 32d, 32e Prism layer
32b Light absorption layer
32c Prism layer
32, 33 wall surface
508 Bulkhead
201, 202 Prism layer
203 light absorption layer
302 Prism sheet
303 Prism layer
304 Light absorption layer

Claims (1)

In an optical device having two optical path separation members that are disposed between a plurality of optical paths that pass through a split field lens and enter a sensor of a focus detection visual field, and prevent crossing of light beams between the optical paths,
The opposing wall surfaces of the two optical path separating members are a prism layer having a mirror surface and a light absorbing layer having a refractive index substantially equal to that of the prism layer and having a light absorber dispersed in a transparent medium. By providing so that there is no air layer between them, the light incident on the inside of the prism layer enters from the mirror surface facing the incident direction and is refracted and then guided to the light absorption layer or incident after being refracted. What optical path separating member der guided to the light absorbing layer is totally reflected at the mirror surface not facing the direction optics is the wall surface other than the wall surface of the facing, characterized in that does not form the prism layer apparatus.

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