JP5152655B2 - Imaging device - Google Patents

Description

  The present invention relates to an imaging device that measures a distance between a host vehicle and a preceding vehicle, for example.

  For example, as shown in Patent Document 1, as a three-dimensional measurement technique using an image, a correlation between a plurality of images obtained by capturing an object from different positions with a stereo camera is obtained, and the stereo camera mounting position and focal length are calculated from parallax with respect to the same object. Image processing by a stereo method for obtaining a distance by the principle of triangulation using camera parameters such as is known.

  In the stereo method described in Patent Document 1 and the like, it is necessary to arrange two imaging devices. In order to measure the inter-vehicle distance between the host vehicle and the preceding vehicle using this stereo method, it is necessary to dispose the imaging device on the upper part of the vehicle such as a room mirror. In addition, since the displacement between the two image pickup devices causes a difference in distance measurement, a robust structure that is not easily affected by heat and vibration is required as a housing for holding the two image pickup devices, which increases the size. For this reason, a large occupied area is required in order to mount the two imaging devices around the room mirror, and it is difficult to mount the two imaging devices on the vehicle.

In order to solve the problem of increasing the size of the imaging device by the stereo method, Non-Patent Document 1 discloses a distance measurement method for processing an image photographed by one imaging device and measuring an inter-vehicle distance from a preceding vehicle. ing. In this distance measurement method, the height y from the road surface of the imaging device mounted on the vehicle, the focal length f of the lens of the imaging device, and the image of the road surface at the position where the front vehicle projected by the lens on the imaging device is present. From the distance z from the optical axis, the distance x from the own vehicle to the position where the preceding vehicle is present is calculated from the similarity of the triangle by the following equation.
x = f · y / z
JP 2008-39491 A Automotive Technology days 2007 Autumn Seminar proceedings hosted by Nikkei Electronics

  The distance measurement method shown in Non-Patent Document 1 can measure distances with a so-called monocular lens, but the measurement range depends on the focal length. In other words, when a lens with a short focal length is used, distance measurement at a close position can be performed, but there is a problem that resolution decreases in distance measurement at a long distance.

  The present invention solves this problem, and can measure the distance between the host vehicle and the preceding vehicle by a monocular instead of the so-called stereo method and can easily attach the vehicle to a vehicle from a distant vehicle to a nearby vehicle. An object of the present invention is to provide an imaging apparatus capable of measuring a wide range of distances.

An image pickup apparatus according to the present invention includes a lens array having a plurality of lenses on the same substrate, an image pickup unit having a plurality of image pickup areas for receiving a light beam transmitted through each lens of the lens array and shooting a subject image, the imaging device and a signal processing apparatus for processing an image signal of an image of a subject captured by the imaging unit, the plurality of lenses of the lens array have different focal lengths from each other, the imaging unit includes a plurality The imaging region is a single unit provided on the same plane, and the signal processing device includes a deviation amount from an optical axis of an image captured in each imaging region of the imaging unit, and the preset imaging The distance ahead of the imaging device is calculated from the height of the device from the road surface and the focal length of each lens.

  Between the lens array and the imaging unit, there is a filter that is divided into a plurality of regions according to each light beam passing through each lens of the lens array, and at least one of the filters transmits a vertically polarized component And a distance ahead of the imaging device is calculated from a vertically polarized image captured by the imaging unit.

  It is desirable to have a light-shielding unit that separates each light beam transmitted through each lens of the lens array and enters the filter.

  In addition, the polarizer region of the filter is formed of a multilayer structure in which a plurality of transparent materials having different refractive indexes are stacked on a transparent substrate, and has a one-dimensional periodic uneven shape that is repeated in one direction for each layer. Features.

  Furthermore, the polarizer region of the filter may be constituted by a wire grid polarizer.

  The present invention can reduce the size of the imaging device by measuring the distance to the front with a single eye instead of the so-called stereo method with one imaging device. It is possible to measure well and to inform the driver of attention information in advance.

  In addition, since distance measurement is performed based on information from a lens array having a plurality of lenses having different focal lengths, a wide range of distance measurement from far to near can be performed with high accuracy.

  Furthermore, by performing distance measurement using a vertically polarized image of the road surface, the road surface can be photographed in a state where the influence of sunlight reflection is reduced, and distance measurement can be performed stably.

  Also, the polarizer region of the filter is formed of a multilayer structure in which a plurality of transparent materials having different refractive indexes are laminated on a transparent substrate, and has a one-dimensional periodic uneven shape that is repeated in one direction for each layer. The polarizer region can be produced with high accuracy.

  1 and 2 show a schematic configuration of an optical system of an imaging apparatus 100 according to the present invention, FIG. 1 is an exploded perspective view, and FIG. 2 is a sectional view. As shown in the figure, the optical system 1 of the image pickup apparatus 100 picks up an image of a road surface, and is formed by laminating a lens array 2, a light shielding spacer 3, a polarizing filter 4, a spacer 5, and a solid-state image pickup unit 6. ing.

  The lens array 2 has two lenses 21a and 21b. The two lenses 21a and 21b are independent from each other, the lens 21a is formed by a single lens or a lens group having a focal length different from the focal length f2 (f2> f1), and the optical axes 7a and 7b are arranged. They are arranged in parallel. Here, assuming that the direction parallel to the optical axes 7a and 7b of the lenses 21a and 21b is the Z axis, one direction perpendicular to the Z axis is the X axis, and the direction perpendicular to the Z axis and the X axis is the Y axis, the lenses 21a and 21b. Are arranged on the same XY plane.

  The light-shielding spacer 3 has two openings 31a and 31b, and is provided on the side opposite to the subject side with respect to the lens array 2. The two openings 31a and 31b are penetrated with a predetermined size centering on the optical axes 7a and 7b, respectively, and the inner wall surface is subjected to antireflection treatment of light by blacking, roughing or matting.

  The polarizing filter 4 has two polarizer regions 41 a and 41 b having a polarization plane different by 90 degrees, and is provided on the opposite side of the light blocking spacer 3 from the lens array 2. The two polarizer regions 41a and 41b are provided in parallel with the XY plane around the optical axes 7a and 7b, respectively. The polarizer regions 41a and 41b convert non-polarized light whose electromagnetic field vibrates in unspecified directions into linearly polarized light by transmitting only vibration components in the direction along the polarization plane.

  The spacer 5 is formed in a rectangular frame shape having an opening 51 through which regions corresponding to the polarizer regions 41 a and 41 b of the polarizing filter 4 pass, and is provided on the side opposite to the light shielding space 3 with respect to the polarizing filter 4. Yes.

  The solid-state imaging unit 6 has two solid-state imaging elements 62 a and 62 b mounted on a substrate 61 having a signal processing unit 8, and is provided on the opposite side of the polarization filter 4 with respect to the spacer 5. Imaging regions where the subject images are actually formed by the two solid-state imaging devices 62a and 62b are provided on the same plane parallel to the XY plane with the optical axes 7a and 7b as the centers. The solid-state imaging devices 62a and 62b do not have a color filter inside when performing monochrome sensing, and a color filter may be disposed at the previous stage when sensing a color image.

  As described above, the optical system 1 of the image pickup apparatus 100 has two optical systems for taking a vertically polarized image and a horizontally polarized image from the road surface so that foreign matters such as dust do not enter the image pickup regions of the solid-state image pickup devices 62a and 62b. The space from the lens array 2 to the solid-state imaging unit 6 is sealed.

  As shown in the block diagram of FIG. 3, the signal processing unit 8 provided on the substrate 61 of the solid-state imaging unit 6 of the imaging apparatus 100 includes signal preprocessing units 81 a and 81 b, image memories 82 a and 82 b, and a distance calculation unit 83. An arithmetic processing unit 84, a road surface state determination unit 85, a road surface information storage unit 86, a road surface information recognition unit 87, and an output unit 88. The signal preprocessors 81a and 81b perform shading correction and the like for correcting the sensitivity unevenness of the image signals output from the individual image pickup devices 62a and 62b of the solid-state image pickup unit 6 so that the vertically polarized image and the horizontally polarized image of the road surface are stored in the image memory. 82a and 82b. The distance calculation unit 83 calculates the distance from the imaging device to the front position using either the vertically polarized image or the horizontally polarized image stored in the image memories 2a and 2b. The arithmetic processing unit 84 calculates the deflection ratio between the vertically polarized image and the horizontally polarized image stored in the image memories 82a and 82b. The road surface state determination unit 85 determines the road surface state based on the polarization ratio calculated by the arithmetic processing unit 84. The road surface information storage unit 86 stores characters and signs to be written on the road surface in advance. The road surface information recognition unit 87 captures one or both of the image memories 82a and 82b, for example, an image stored in the image memory 82a, and compares the characters and signs stored in the road surface information storage unit 86 with the characters and signs. recognize. The output unit 88 outputs the distance to the front position calculated by the distance calculation unit 83, the road surface state determined by the road surface information determination unit 85, and the characters and signs recognized by the road surface information recognition unit 87 to a display device (not shown).

  Each component of the optical system 1 of the imaging apparatus 100 will be described in detail.

The lens array 2 of the optical system 1 is manufactured by the reflow method shown in FIG. 4A, the ion diffusion method shown in FIG. 4B, the ink jet method shown in FIG. 4C, the gray scale mask method shown in FIG. . In the reflow method shown in FIG. 4A, a cylindrical photoresist pattern 212 is produced on the surface of a glass substrate 211 by photolithography, and then the transparent substrate 211 is heated to cause the resist to flow, and the lens shape 213 is caused by surface tension. It is a method of producing. In addition, the ion diffusion method shown in FIG. 4B is a method in which ions such as Tl ⁺ are diffused in a glass substrate 211 on which a mask matched to the lens shape is formed to cause a stepwise change in refractive index. In the ink jet method shown in FIG. 4C, a small amount of resin material 215 is dropped at a predetermined position using an ink jet printer head 214, and a lens shape is produced by surface tension. These methods use the shape and refractive index distribution that occur naturally by surface tension and ion diffusion as lenses. In the gray scale mask method shown in FIG. 4D, the lens shape 213 is formed by controlling the shape of the resist 217 formed on the glass substrate 211 by the transmittance distribution given to the gray scale mask 216. This method can produce various shapes compared to other methods.

  The reflow method and the gray scale mask method shown in FIG. 4 show that the lens shape is made with a photoresist, but a lens made with a photoresist usually has insufficient transmittance and resistance to humidity and light irradiation. Since there are problems such as weakness, the resist pattern is used after being transferred to the substrate material by anisotropic dry etching. However, in the anisotropic dry etching process, a large shape change may occur between the resist shape and the shape after etching, and it is difficult to produce a lens with little error with respect to the target shape. Further, this shape change varies depending on the type of etching apparatus, etching conditions, and the type of substrate material. In particular, since the transmittance, wavelength range, and refractive index, which are important parameters for evaluating a lens, are limited by the type of substrate, it is possible to manufacture a lens having high shape accuracy for various substrate materials. That is important.

  Moreover, you may use the grinding | polishing used for normal lens manufacture, or the mold method which manufactures a metal mold | die and encloses a resin material. Further, as shown in FIG. 5A, a plurality of lens arrays 22 may be stacked via a spacer 23 or the like to form lenses 21a and 21b having focal lengths different from f1 and f2. By combining a plurality of lens arrays 22 in this way, the shape of each lens can be simplified and manufactured for use. Further, as shown in FIG. 5B, the lens shape of the plurality of lens arrays 22 may be changed. For example, since the amount of incident light varies depending on the polarization direction, iris adjustment may be performed by changing the lens aperture.

  Further, a method of photographing with a plurality of lenses with respect to one image sensor is known as a compound eye system. Such a compound eye system is known as a method for thinning an imaging apparatus. That is, an image pickup apparatus that forms an image of a subject image on a solid-state image pickup device via a lens system is widely used in a digital still image pickup apparatus, an image pickup apparatus for a mobile phone, and the like. In recent years, imaging devices are required to achieve both high pixel count and thin thickness. In general, as the number of pixels increases, the lens system is required to have high resolution, and thus the thickness of the imaging device in the optical axis direction tends to increase. On the other hand, by reducing the pixel pitch of the image sensor and reducing the size of the image sensor even with the same number of pixels, it is possible to scale down the lens system and realize an image pickup device that achieves both high pixel count and thinning. An attempt to do so is underway. However, since the sensitivity and saturation output of the solid-state imaging device are proportional to the pixel size, there is a limit to reducing the pixel pitch. A so-called monocular system is generally used as an imaging device, which includes one lens system in which one or more lenses are arranged along an optical axis and one solid-state imaging device arranged on the optical axis. is there. On the other hand, in recent years, in order to reduce the thickness of the imaging apparatus, a plurality of lens systems arranged on the same plane and a plurality of lenses arranged on the same plane corresponding to the plurality of lens systems on a one-to-one basis. There has been proposed an imaging apparatus including a plurality of imaging areas. This imaging apparatus is called a compound eye type because it includes a plurality of imaging units including a pair of lens systems and a single imaging region. Such a compound eye type imaging apparatus is described in, for example, Japanese Patent No. 3397758, and can achieve high pixels and thinning. Accordingly, the lens array 2 is provided with two lenses 21 a and 21 b, enters the lenses 21 a and 21 b, passes through the polarizer regions 41 a and 41 b of the polarization filter 4, and enters the solid-state imaging devices 62 a and 62 b of the solid-state imaging unit 6. By synthesizing images obtained with light, a high-quality image can be obtained and the thickness can be reduced.

  Next, the polarizer regions 41a and 41b of the polarizing filter 4 will be described with reference to the perspective view of FIG. The polarizer regions 41a and 41b are made of a polarizer made of, for example, a photonic crystal, and as shown in FIG. 6, a transparent high refractive index medium layer 412 and a transparent substrate 411 on which periodic groove arrays are formed. The low refractive index medium layers 413 are alternately stacked while preserving the shape of the interface. As shown in FIG. 6, each of the high refractive index medium layer 412 and the low refractive index medium layer 413 has periodicity in the X direction orthogonal to the groove rows of the transparent substrate 411, but is parallel to the groove rows. It may be uniform in the Y direction, or may have a periodic or aperiodic structure with a length greater than the X direction. Such a fine periodic structure (photonic crystal) can be produced with high reproducibility and high uniformity by using a method called a self-cloning technique described in JP-A-10-335758. it can.

As shown in the perspective view of FIG. 7A, the polarizer regions 41a and 41b made of the photonic crystal are orthogonal coordinates having a Z axis parallel to the optical axes 7a and 7b and an XY axis orthogonal to the Z axis. The system comprises a multilayer structure in which two or more transparent materials are alternately laminated in the Z-axis direction on one substrate 411 parallel to the XY plane, for example, an alternating multilayer film of Ta ₂ O ₅ and SiO ₂ . Each film | membrane has uneven | corrugated shape in polarizer area | region 41a, 41b, and this uneven | corrugated shape is periodically repeated in one direction in XY plane, and is formed. As shown in FIG. 7B, the polarizer region 41a has a groove direction parallel to the Y-axis direction, and the polarizer region 41b has a groove direction parallel to the X-axis direction. The directions of the grooves are different by 90 degrees between the polarizer region 41a and the polarizer region 41b. That is, from the input light incident on the XY plane, the polarization components having different polarization directions are transmitted by the polarizer region 41a and the polarizer region 41b, and equal amounts of non-polarized components are respectively transmitted by the polarizer region 41a and the polarizer region 41b. It is designed to be transparent. Note that, although two types of concave and convex grooves are provided in the polarizing filter 4, a plurality of concave and convex grooves may be provided. Thus, by forming the polarizer regions 41a and 41b with a photonic crystal, the polarizer regions 41a and 41b can be used stably for a long period of time with excellent ultraviolet deterioration.

  The opening areas and transmission axes of the polarizer regions 41a and 41b can be freely designed according to the size and direction of the groove pattern to be processed on the transparent substrate 411 first. The groove pattern can be formed by various methods such as electron beam lithography, photolithography, interference exposure, and nanoprinting. In any case, the direction of the groove can be determined with high accuracy for each minute region. Therefore, it is possible to form a polarizer region in which micropolarizers having different transmission axes are combined, and a polarizer in which a plurality of polarizer regions are arranged. In addition, since only a specific region having a concavo-convex pattern operates as a polarizer, if the peripheral region is flat or isotropic concavo-convex pattern in the plane, light can be used as a medium having no polarization dependency. To Penetrate. Therefore, a polarizer can be formed only in a specific region.

  An imaging device is arranged in the polarizer regions 41a and 41b of the polarization filter 4 so that either groove direction is parallel to the road surface, and the vertically polarized image and the horizontal polarization of the road surface reflected light in the polarizer regions 41a and 41b. Get an image.

  Next, a manufacturing method of the light shielding spacer 3 will be described with reference to a perspective view of FIG. As shown in FIG. 8A, a coating 312 for shielding ultraviolet rays is applied to the outer surface of a photosensitive glass substrate 311 containing silver, and the coating 312 is formed by patterning in a portion 312 where the light shielding wall 32 is to be formed. remove. After the photosensitive glass 311 is irradiated with ultraviolet rays, the paint 312 is removed. By this ultraviolet irradiation, as shown in FIG. 8B, silver is deposited on the portion 312 of the glass substrate 311 where the ultraviolet light is directly irradiated to form the light shielding wall, and is blackened to form the light shielding portion 313. Is done. The light shielding portion 313 is also formed inside the glass of the portion 312 where the light shielding wall 32 is to be formed. In this state, portions other than the portion 312 where the light shielding wall 32 of the glass substrate 311 is to be formed are removed by machining or etching, and two openings 31a and 31b and a light shielding portion 313 are provided as shown in FIG. A light shielding wall 32 is formed. In this way, the light-shielding spacer 3 having the two openings 31a and 31b can be easily manufactured. By arranging the openings 31a and 31b of the light shielding space 3 corresponding to the polarizer regions 41a and 41b of the polarizing filter 2, it is possible to reliably prevent light from leaking into the adjacent polarizer regions. Moreover, since the inner wall surfaces of the openings 31a and 31b are blackened, stray light reflected by the inner wall surfaces can be prevented from entering the solid-state imaging elements 62a and 62b of the solid-state imaging unit 6.

  Next, processing when the imaging apparatus 100 is mounted on a vehicle such as an automobile and the distance between the host vehicle and the preceding vehicle is measured will be described with reference to the schematic diagram of FIG.

First, one of the polarizer regions 41a and 41b of the polarizing filter 4 of the imaging device, for example, the imaging device 100 is arranged so that the groove direction of the polarizer region 41b is parallel to the road surface, and is mounted on the vehicle. An image of the road surface at the position where the vehicle 200 exists is taken. By this photographing, there is a vehicle ahead by the light incident on the lenses 21 a and 21 b of the lens array 2, transmitted through the polarizer regions 41 a and 41 b of the polarization filter 4 and incident on the solid-state imaging devices 62 a and 62 b of the solid-state imaging unit 6. When the image of the road surface at the current position is stored in the image memories 82a and 82b, the distance measuring unit 83 projects the front vehicle projected by the lens 21a onto the solid-state imaging device 62a of the solid-state imaging unit 6 stored in the image memory 82a. 200 is read from the image memory 82a, the distance from the optical axis 7a of the read image, the height y from the road surface of the imaging device 100 set in advance and the lens 21a, for example, A distance x from the own vehicle to the position where the preceding vehicle 200 exists is calculated from the focal distance f1 by the following formula from the similarity of the triangle.
x = f1 · y / z
In this way, the inter-vehicle distance x to the preceding vehicle 200 can be measured. The measurement range of the distance x depends on the focal lengths f1 and f2 of the lenses 21a and 21b. That is, when a lens with a short focal length is used, the distance measurement at a close position can be performed, and the resolution is deteriorated for the measurement at a long distance. In contrast to this, the lens array 2 is provided with two optical systems of lenses 21a and 21b having different focal lengths, and an image photographed by the optical system of the lens 21b having a long focal length is used for a far distance, and in the near place. By measuring an inter-vehicle distance x to the front vehicle 200 using an image captured by the optical system of the lens 21a having a short focal length, a wide range distance from the far front vehicle 200 to the adjacent front vehicle 200 is measured. Can do. For example, when the vehicle is running, an image taken with the optical system of the lens 21b having a long focal length is used, and when stopping or starting running, an image taken with the optical system of the lens 21a having a short focal length is used. good. Or you may switch the optical system of the lens 21b with a long focal distance, and the optical system of the lens 21a with a short focal distance by the speed of a vehicle.

  Next, an operation when the imaging apparatus 100 detects a road surface state will be described.

  First, the imaging device is arranged such that one of the polarizer regions 41a and 41b of the polarizing filter 4 of the imaging device 100, for example, the groove direction of the polarizer region 41b is parallel to the road surface, and is mounted on a vehicle, for example. Shoot the road surface. The light incident on the lens 21a of the lens array 2 by this photographing enters the polarizer region 41a of the polarizing filter 4 through the light shielding spacer 3, and only the light of the vertical polarization component is emitted from the polarizer region 41a to the solid state of the solid-state imaging unit 6. The light enters the image sensor 92a. Further, the light incident on the lens 21b of the lens array 2 enters the polarizer region 41b of the polarizing filter 4 through the light shielding spacer 3, and only the light of the horizontal polarization component is captured by the solid-state imaging unit 6 in the polarizer region 41b. Incident on element 92b. The image signals photographed by the solid-state imaging devices 92a and 92b are processed by the signal preprocessing units 81a and 81b of the signal processing unit 8, and the vertically polarized images and the horizontally polarized images are stored in the image memories 82a and 82b, respectively. The arithmetic processing unit 84 calculates the polarization ratio between the vertical polarization image and the horizontal polarization image stored in the image memories 82 a and 82 b and outputs the polarization ratio to the road surface state determination unit 85. The road surface state determination unit 85 determines the wet state of the road surface from the magnitude of the polarization ratio between the input vertical polarization image and the horizontal polarization image, and determines the polarization ratio between the input vertical polarization image and the horizontal polarization image and a preset reference value. The presence or absence of a road surface defect is determined based on whether or not the polarization ratio input in comparison exceeds a reference value.

A road surface wetness determination process by the road surface state determination unit 85 will be described with reference to the schematic diagram of FIG. As shown in FIG. 10 (a), the wet road surface becomes a mirror surface when water accumulates on the uneven portions of the surface, and the reflected light from this mirror surface exhibits polarization characteristics. In this case, if the reflectances of the vertical polarization component and the horizontal polarization component of the reflected light are Rs and Rp, the reflected light intensities Is and Ip with respect to the incident light of the light intensity I are expressed by the following equations, and the incident angle dependency is shown in FIG. 11 as shown.
Is = Rs · I
Ip = Rp · I
Thus, the horizontal polarization component of the reflected light at the mirror surface has a reflected light intensity of zero when the incident angle is equal to the Brewster angle (53.1 degrees), and the vertical polarized light component gradually increases as the incident angle increases. Show properties.

  On the other hand, as shown in FIG. 10 (b), the road surface at the time of drying has a rough surface, so that irregular reflection is dominant, the reflected light does not show the polarization characteristics, and the reflected light intensity of each polarization component is almost equal ( Rs = Rp). Therefore, it is possible to extract information on road surface moisture from the luminance information of the vertically polarized image and the horizontally polarized image based on the polarization characteristics.

Specifically, as shown in the following formula, the reflected light intensity Is of the vertical polarization component and the reflected light intensity Ip of the horizontal polarization component, that is, the ratio H of the image luminance is obtained.
H = Is / Ip = Rs / Rp
Since the ratio H between the reflected light intensities Is and Ip does not depend on the incident light intensity I, it is possible to stably extract the polarization characteristic while removing the influence of the luminance fluctuation of the outside world.
A luminance average value of the polarization ratio H is obtained, and the wet state of the road surface is determined from the magnitude of the value. For example, when the road surface is dry, the vertical polarization component and the horizontal polarization component are substantially equal, so the polarization ratio H is about 1. In addition, when the road surface is completely wet, the horizontal polarization component is considerably larger than the vertical polarization component, so that the polarization ratio H is a large value. In addition, when the road surface is slightly wet, the polarization ratio H is an intermediate value thereof. Therefore, the wet state of the road surface can be calculated from the value of the polarization ratio H.

  The wet state of the road surface determined by the road surface state determination unit 85 and the presence or absence of a defect are output from the output unit 88 to a display device (not shown) and displayed. In this way, the moving vehicle can take a picture of the wet state of the road surface, and can issue caution information such as a slip caution.

  On the other hand, the road surface information recognition unit 87 reads, for example, a vertically polarized image stored in the image memory 82a, and recognizes characters and signs displayed on the road surface by comparing the read image with characters and signs stored in the road surface information storage unit. The recognized characters and signs are output from the output unit 88 to the display device and displayed. In this way, it is possible to reliably detect information such as an upper limit speed display and a stop display displayed on the road surface, a white line that divides the lane, and the like, and provide more advanced driving assistance to the driver.

  The advantage of reading the vertically polarized image by the road surface information recognition unit 87 will be described with reference to FIG. In FIG. 12, 101 is a rearview mirror, 102 is a car ceiling, 103 is a car windshield, 104 is a dashboard, 104a is an upper surface of the dashboard, and the imaging device 100 is mounted on the rear surface of the room mirror 101. Yes. The light from the sun 105 enters the driver's seat of the automobile and is reflected by the upper surface portion 104a of the dashboard 104. The reflected light is incident on the inner surface of the windshield 103, and the reflected light reflected here again is the imaging device 100. When the light is incident on the image pickup device 100, there is a problem of reflection from the windshield 103 that significantly lowers the contrast of an image that should be originally obtained by the imaging apparatus 100. This is particularly noticeable when a highly reflective object such as a map book or towel is placed on the upper surface 104 a of the dashboard 104.

  Since such reflected light from the glass is polarized light whose light vibration direction is only one direction (horizontal polarization component), the windshield 103 is obtained by taking out the vertically polarized image by the road surface information recognition unit 86 of the imaging device 100. It is possible to take an image of the road surface state in a state where the influence of reflection from the road is reduced. Similarly, it is also possible to cut a horizontal polarization component among the components of road surface reflected light accompanying sunlight.

  In the above description, the case where the polarizer regions 41a and 41b of the optical filter 4 are formed of, for example, a photonic crystal has been described. However, wire grid polarizers may be used as the polarizer regions 41a and 41b. This wire grid type polarizer is a polarizer formed by periodically arranging thin metal wires, and has been conventionally used in the millimeter wave region of electromagnetic waves. The structure of the wire grid polarizer has a structure in which fine metal wires that are sufficiently thin compared to the wavelength of the input light are arranged at intervals that are sufficiently short compared to the wavelength. It is already known that when light is incident on such a structure, polarized light parallel to the metal thin wire is reflected and polarized light orthogonal thereto is transmitted. With respect to the direction of the fine metal wire, since it can be produced by changing each region independently in one substrate, the characteristics of the wire grid polarizer can be changed for each region. If this is utilized, it can be set as the structure which changed the direction of the transmission axis for every polarizer area | region 41a, 41b.

  As a method for manufacturing this wire grid, a thin metal can be left by forming a metal film on a substrate and performing patterning by lithography. As another manufacturing method, a groove is formed on the substrate by lithography, and a metal is formed by vacuum deposition from a direction perpendicular to the direction of the groove and inclined from the normal line of the substrate (a direction oblique to the substrate surface). It can produce by doing. In vacuum deposition, particles flying from the deposition source hardly collide with other molecules or atoms in the middle of the deposition, and the particles travel linearly from the deposition source to the substrate. On the other hand, at the bottom part (concave part) of the groove, the film is shielded by the convex part and hardly formed. Therefore, by controlling the amount of film formation, a metal film can be formed only on the convex portion of the groove formed on the substrate, and a thin metal wire can be produced. The wire metal used in the wire grid polarizer is preferably aluminum or silver, but the same phenomenon can be realized even with other metals such as tungsten. In addition, as lithography, optical lithography, electron beam lithography, X-ray lithography, and the like can be given. However, when an operation with visible light is assumed, the interval between thin lines is about 100 nm, and thus electron beam lithography or X-ray lithography is more preferable. . Also, vacuum deposition is desirable for metal film formation. However, since the directionality of particles incident on the substrate is important, sputtering in a high vacuum atmosphere or collimation sputtering using a collimator is also possible.

It is a disassembled perspective view which shows schematic structure of the optical system of the imaging device of this invention. It is sectional drawing which shows schematic structure of an imaging device. It is a block diagram which shows the structure of the signal processing part of an imaging device. It is a schematic diagram which shows the preparation methods of a lens array. It is sectional drawing which shows the other structure of a lens array. It is a perspective view which shows the structure of the polarizer area | region of a polarizing filter. It is a perspective view which shows the structure of a polarizing filter. It is a perspective view which shows the preparation methods of a light shielding spacer. It is a schematic diagram which shows a process when measuring a distance between vehicles. It is a schematic diagram which shows the wet state of a road surface. It is a characteristic view which shows the incident angle dependence of the vertical polarization component and horizontal polarization component with respect to incident light. It is a layout view showing a state where the imaging device is mounted on a car.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100; Imaging device, 1; Optical system, 2; Lens array, 3; Light-shielding spacer, 4; Polarization filter, 5; Spacer, 6: Solid-state imaging unit, 7: Optical axis, 8;
21; Lens, 31; Opening, 41; Polarizer region, 51; Opening, 61; Substrate,
62; solid-state imaging device, 81; signal preprocessing unit, 82; image memory, 83; arithmetic processing unit,
84; Road surface state determination unit, 85; Road surface information storage unit, 86; Road surface information recognition unit,
87: Output unit.

Claims (5)

A lens array having a plurality of lenses on the same substrate, an imaging unit having a plurality of imaging areas for capturing a subject image by receiving a light beam transmitted through each lens of the lens array, and a subject imaged by the imaging unit An image pickup apparatus including a signal processing device that processes an image signal of an image,
A plurality of lenses of the lens array have different focal lengths from each other,
The imaging unit is a single unit in which the plurality of imaging regions are provided on the same plane,
The signal processing device is configured to calculate the imaging device based on a deviation amount from an optical axis of an image captured in each imaging region of the imaging unit, a height from the road surface of the imaging device, and a focal length of each lens. An imaging apparatus characterized by calculating a distance ahead.   Between the lens array and the imaging unit, there is a filter that is divided into a plurality of regions according to each light beam passing through each lens of the lens array, and at least one of the filters transmits a vertically polarized component The imaging apparatus according to claim 1, further comprising: a polarizer region that calculates a distance ahead of the imaging apparatus from a vertically polarized image captured by the imaging unit.   The imaging apparatus according to claim 2, further comprising a light shielding unit that separates each light beam transmitted through each lens of the lens array and enters the filter.   The polarizer region of the filter is formed of a multilayer structure in which a plurality of transparent materials having different refractive indexes are laminated on a transparent substrate, and has a one-dimensional periodic uneven shape repeated in one direction for each layer. The imaging device according to claim 2.   The imaging device according to claim 2, wherein the polarizer region of the filter is configured by a wire grid polarizer.

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