Imaging device
A liquid crystal aperture with a patterned region and controlled electric fields addresses the challenge of capturing clear and 3D images by enabling precise distance measurement and image reconstruction, enhancing image clarity and depth perception.
Patent Information
- Application Number
- JP2023152255
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2023-09-20
- Publication Date
- 2025-04-02
AI Technical Summary
Existing imaging technologies struggle to capture clear images across the entire screen or create 3D images without blurring, as they lack the ability to accurately measure distance information from the lens to the imaging target.
The use of a liquid crystal aperture with a patterned region and controlled electric fields to form a coded diaphragm pattern, allowing for precise distance measurement and image reconstruction, including a configuration that supports high-speed switching between coded aperture patterns.
Enables the creation of clear, all-focus images and 3D images by accurately measuring distances, overcoming blurring issues and enhancing image clarity and depth perception.
Smart Images
Figure 2025044586000001_ABST
Abstract
Description
[Technical field]
[0001] The present invention relates to an imaging device using a coded imaging method. [Background technology]
[0002] Imaging with a camera involves capturing a two-dimensional image from a three-dimensional world. In a normal camera, the image at the focal point is displayed clearly, but as the distance from the focal point increases, the image becomes blurred.
[0003] On the other hand, there is a demand for full-screen display, which allows clear images to be displayed on the entire screen, or for obtaining 3D images. To realize such demands, information on the distance between each position of the imaging target and the lens is required.
[0004] Non-Patent Document 1 describes a technique for measuring and calculating distance information while taking a picture with a camera by using a specially shaped coded aperture. Non-Patent Document 2 describes a technique for using a pair of a pattern for dealing with image blur and a pattern for acquiring distance information as a coded aperture. [Prior art documents] [Non-patent literature]
[0005] [Non-Patent Document 1] Image and Depth from a Conventional Camera with a Coded Aperture Anat Levin Rob Fergus et al. [Non-Patent Document 2] Coded Aperture Pairs for Depth from Defocus and Defocus Deblurring Changyin Zhou Stephen Lin Shree K. Nayar Summary of the Invention [Problem to be solved by the invention]
[0006] There is a method of taking a picture using a specially shaped aperture pattern (hereafter also called a coded aperture pattern) as an imaging technology that can measure the distance from the lens to the subject and obtain distance data to form a three-dimensional image or an all-focus image simply by taking a picture. In other words, this method makes it possible to calculate the distance from the lens to the pixel by taking a picture using this coded aperture pattern.
[0007] If this coded aperture pattern is made of liquid crystal, the degree of freedom in pattern formation can be increased. Hereinafter in this specification, this is also referred to as a liquid crystal aperture. A liquid crystal aperture has the advantage of being very small in size compared to normal liquid crystal display devices. Also, color images and gray displays are not necessary, and only black and white displays are sufficient. Instead, a clear difference between white and black displays is required. In other words, a large contrast is required between displays and black displays.
[0008] An object of the present invention is to realize a liquid crystal diaphragm suitable for forming such a coded diaphragm pattern. [Means for solving the problem]
[0009] The present invention is intended to solve the above problems, and the main specific means are as follows.
[0010] (1) An imaging device having a lens, an optical sensor that receives light, and an aperture disposed adjacent to the lens between the lens and an object to be imaged, the aperture being composed of a liquid crystal aperture having a liquid crystal layer sandwiched between a first substrate and a second substrate, a peripheral light-shielding frame, and a patterned region formed therein, the first substrate having a lower layer electrode, an interlayer insulating film, and an upper layer electrode formed in that order, the upper layer electrode having a first electrode formed in an area including the center of the patterned region, and a second electrode disposed with a gap from the first electrode, the gap and the lower layer electrode overlap in a plan view, a first light-shielding film constituting the light-shielding frame is formed around the second substrate, a first columnar spacer is formed between the first light-shielding film and the first substrate in a plan view, and a second columnar spacer is formed between the first electrode and the second substrate in a plan view.
[0011] (2) The imaging device described in (1), characterized in that a common electrode is formed on the second substrate, and when a first pattern is formed in the pattern area, the liquid crystal layer is controlled by an electric field between the upper electrode and the common electrode.
[0012] (3) a common electrode is formed on the second substrate; The imaging device according to (1), wherein when a second pattern is formed in a pattern region, the liquid crystal layer is controlled by an electric field between the lower electrode and the common electrode.
[0013] (4) An imaging device having a lens, an optical sensor that receives light, and an aperture disposed adjacent to the lens between the lens and an object to be imaged, the aperture being configured as a liquid crystal aperture having a rectangular outer shape, a liquid crystal layer sandwiched between a first substrate and a second substrate, and a pattern area defined by a peripheral light-shielding frame, the pattern area being a polygon having five or more sides or a circle, the pattern area having scanning lines extending in a first direction and arranged in a second direction, video signal lines extending in the second direction and arranged in the first direction, pixels being formed in areas surrounded by the scanning lines and the video signal lines, the pitch of the pixels in the first direction and the second direction being 30 μm or less, and within the pattern area, a columnar spacer defining the distance between the first substrate and the second substrate is formed only in a first region including a center portion, and the width of the first region in the first direction is 30% or less of the width of the pattern area. [Brief description of the drawings]
[0014] [Figure 1] This is an optical model of an imaging device that uses a lens. [Diagram 2] 1 is an example of a coded aperture pattern. [Diagram 3] 13 is another example of a coded aperture pattern. [Figure 4] FIG. 1 is a cross-sectional view of an imaging system using an aperture having a coded aperture pattern. [Diagram 5] 1 is an example of a coded aperture pattern. [Figure 6] This is an example of an aperture that adjusts the amount of light. [Figure 7] FIG. 4 is a plan view showing the shape of an upper layer electrode. [Figure 8] FIG. 4 is a plan view showing the shape of a lower layer electrode. [Figure 9] FIG. 13 is a plan view showing an example of a divided lower electrode. [Figure 10] FIG. 6 is a cross-sectional view taken along line AA in FIG. 5, illustrating the problem area in FIG. [Figure 11] FIG. 2 is a plan view showing a coded aperture pattern according to the first embodiment of the first embodiment. [Figure 12] 12 is a cross-sectional view of FIG. 11 taken along line B-B. [Figure 13] FIG. 11 is a plan view showing a coded aperture pattern according to the second embodiment of the first embodiment. [Figure 14] 14 is a cross-sectional view taken along CC in FIG. 13. [Figure 15] FIG. 11 is a plan view showing a coded aperture pattern according to the third embodiment of the first embodiment. [Figure 16] FIG. 16 is a cross-sectional view taken along the line DD in FIG. [Figure 17] FIG. 16 is a more detailed cross-sectional view taken along the line DD of FIG. [Figure 18] FIG. 11 is a plan view of a liquid crystal diaphragm showing a second embodiment. [Figure 19] FIG. 11 is a plan view of a liquid crystal aperture according to a third embodiment. [Figure 20] FIG. 20 is a plan view of the pixel in FIG. [Figure 21] FIG. 20 is a cross-sectional view of the liquid crystal diaphragm in FIG. 19. [Figure 22] 20 is a plan view showing another example of the pixel of FIG. 19. [Figure 23] FIG. 11 is a plan view of another liquid crystal diaphragm according to the third embodiment. [Figure 24] 24 is a cross-sectional view of FIG. 23 . [Diagram 25] FIG. 13 is a plan view of still another liquid crystal diaphragm according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0015] A camera is a means of capturing a 3D image as a 2D image. To reconstruct a 3D image or an all-focus image from this captured 2D image, it is necessary to know the distance from each imaging point to the center of the lens. Figure 1 shows an optical model of a camera using a lens. In Figure 1, when an object at a distance u is measured using a lens with a focal length of f, all incident light is focused on a plane v according to the lens law shown in (Equation 1).
[0016]
number
[0017] If the position p of the imaging plane coincides with v, a focused image is obtained, but if it is shifted forward or backward, the projected light rays are projected as a circle of size b, as shown in (Equation 2). This circle is sometimes called the circle of confusion.
[0018]
number
[0019] In (Equation 2), a indicates the size of the aperture. If the size of b exceeds the size of the pixel, the image will be blurred. Since the camera depth of field is limited, objects at a depth far from the focal position will be blurred in the image. The size of this blur depends on the distance from the camera to the object, as shown in (Equation 1) and (Equation 2). Therefore, by measuring the blur, it is possible to estimate the distance from the camera to the object. This method is called Depth From Defocus (DFD). For example, Levin et al. have proposed a coded aperture pattern as shown in Figure 2 to effectively measure distance using DFD.
[0020] Incidentally, an image captured by a camera is an image that includes various degradation factors compared to an all-focus image (an ideal image without blur in the entire screen). These degradation factors are expressed as a general blur function PSF (Pont Spread Function). Here, if the blur function is represented by k, the image j captured by the camera can be expressed as the convolution of the all-focus image i and the blur function k as shown in (Equation 3).
[0021]
number
[0022] That is, the all-focus image i can be restored by deconvolving the captured image j. Since obtaining the all-focus image i requires calculating the distance to each imaging point, the restoration of the all-focus image is equivalent to the restoration of the distance from the lens center to the imaging point.
[0023] Equation 4 is an inverse Fourier transform of equation 3.
[0024]
number
[0025] Here, the inverse function of the PSF, K -1 If is known, the frequency image I of the all-in-focus image can be obtained as shown in (Equation 5).
[0026]
number
[0027] Then, by inversely transforming I, the all-focus image i can be restored. As mentioned above, restoring the all-focus image i is equivalent to measuring the distance from the lens center to each imaging point of the subject. When an image is captured through the coded aperture pattern 30, the influence of the coded aperture pattern 30 becomes dominant on the blur function PSF.
[0028] However, the blur function k suitable for reproducing a general all-in-focus image is different from the blur function k suitable for distance measurement using a DFD. The blur function is determined by the coded aperture pattern 30. In order to perform accurate distance measurement and reproduce an all-in-focus image using this, Zhou proposes using a coded aperture pattern suitable for distance measurement using a DFD and a coded aperture pattern that is a pair of data for reproducing an all-in-focus image, as shown in Figure 3.
[0029] Imaging devices that enable distance measurement using DFD, or reproduction of all-in-focus images using distance data, and even reproduction of three-dimensional images, are required to be capable of handling a variety of coded aperture patterns, and, when multiple coded aperture patterns are used, to have a configuration that allows high-speed switching between patterns.
[0030] The present invention uses a liquid crystal diaphragm to realize a configuration that satisfies such requirements, and also realizes a liquid crystal diaphragm that meets such requirements and an imaging device that uses the same. EXAMPLES
[0031] Fig. 4 is a cross-sectional view of a case where a subject 40 is photographed using the lens 10. In Fig. 4, the subject 40 is on the right side of the lens 10, and an optical sensor 50 onto which an image is projected is on the left side. Hereinafter, the subject 40 may be referred to as the subject 40. However, in this case, the subject 40 refers not only to a small object, but also to a broad object including the background surrounding the object. A semiconductor imaging element such as a CMOS image sensor or a CCD image sensor is used as the optical sensor 50.
[0032] Generally, in lens 10, the refractive index increases as the distance from the center increases. Also, the spherical aberration increases as the distance from the center increases. However, since Fig. 4 is a cross-sectional view for the purpose of explanation, the spherical aberration of lens 10 is ignored. The same applies to Fig. 4 and subsequent figures.
[0033] In FIG. 4, light that leaves the center of the subject 40, as shown by the dotted line, is refracted by the lens 10 and focused at the center of the optical sensor (hereinafter also simply referred to as the sensor) 50. Light that leaves the upper end of the subject 40 and passes through the center of the lens 10 travels straight and forms an image at the lower end of the sensor 50, as shown by the solid line. Light that leaves the upper part of the subject 40 and does not pass through the center of the lens 10 is refracted by the lens 10 and forms an image at the lower part of the sensor 50, as shown by the two-dot chain line. On the other hand, light that leaves the lower end of the subject 40 and passes through the center of the lens 10 travels straight and forms an image at the upper end of the sensor 50, as shown by the solid line. Light that leaves the lower part of the subject 40 and does not pass through the center of the lens 10 is refracted by the lens 10 and forms an image at the upper part of the sensor 50, as shown by the one-dot chain line.
[0034] In Fig. 4, an aperture 20 is disposed between the lens and the subject, close to the lens. This aperture has a coded aperture pattern 30. In addition, a second aperture 21 that determines the amount of light passing through is present outside the coded aperture pattern 30. In this specification, the coded aperture pattern 30 and the second aperture are collectively referred to as the aperture. However, the second aperture 21 is not essential. It is also possible for the outer frame of the coded aperture pattern 30 to serve as the second aperture 21.
[0035] Fig. 5 is a plan view of the diaphragm 20 formed by a liquid crystal diaphragm. The liquid crystal diaphragm is configured such that a TFT substrate on which electrodes etc. are formed and a counter substrate on which a light-shielding film etc. are formed are sealed at their peripheries with a sealant, and liquid crystal is disposed inside. In Fig. 5, a light-shielding film 201 is formed in a frame shape. The light-shielding film 201 is manufactured by the same process and with the same material as a black matrix used in liquid crystal display devices etc. The light-shielding film 201 is formed on the counter substrate.
[0036] A common electrode is formed on the opposing substrate in a planar shape. A pixel electrode facing the common electrode is formed on the TFT substrate. In Fig. 5, a columnar spacer 210 is arranged in the frame portion so as to overlap the light-shielding film 201 and to define the distance between the TFT substrate and the opposing substrate.
[0037] A coded aperture pattern 30 is formed inside a frame formed by a light-shielding film 201. In Fig. 5, a lower layer electrode 101 and an upper layer electrode 103 are formed on the TFT substrate with an insulating film sandwiched therebetween in order to display the coded aperture pattern 30. The lower layer electrode 101 and the upper layer electrode 103 are fixed patterns. This cross-sectional structure on the TFT substrate side is shown in Fig. 17, for example.
[0038] As the aperture that determines the amount of light to be used, the frame formed of a light-shielding film in FIG. 5 can be used.
[0039] Fig. 7 shows an example of the coded aperture pattern 30 formed when only the upper layer electrode 103 is turned ON. The example in Fig. 7 is a combination of three rectangular and two L-shaped regions. Fig. 7 shows an example in which all five regions are turned ON, but a different coded aperture pattern 30 can be obtained by turning OFF any one, or two to four patterns. In order to prevent light leakage, it is desirable that the gap formed by the upper layer electrode 103 is covered by the lower layer electrode 101 in a plan view.
[0040] Fig. 10 is a cross-sectional view showing a problem when a liquid crystal aperture is used. Fig. 10 corresponds to the cross-sectional view taken along the line AA in Fig. 5. In Fig. 10, the counter substrate 200 is disposed on the lower side, and the TFT substrate 100 is disposed on the upper side. In Fig. 10, a light-shielding film 201 is disposed around the counter substrate 200, and a resin overcoat film 202 is formed to cover the light-shielding film 201. In Fig. 10, columnar spacers 210 are formed on the counter substrate 200 around the TFT substrate 100 and the counter substrate 200 to control the distance between the TFT substrate 100 and the counter substrate 200. In addition, the counter substrate 200 and the TFT substrate 100 are bonded to each other around the periphery by a sealant 150, and liquid crystal 300 is sealed inside.
[0041] In FIG. 10, there is no columnar spacer in the pattern region. The liquid crystal layer thickness d1 at the center is smaller than the layer thickness d2 at the periphery. In other words, both the TFT substrate 100 and the counter substrate 200 are convex toward the center of the pattern region. This shape is necessary to maintain the sealing characteristics of the liquid crystal, but the problem is that the size of d1 varies. Since d1 is the layer thickness of the liquid crystal layer 300 at the center, the variation of d1 means that the layer thickness of the liquid crystal layer 300 varies. This causes the transmittance of the liquid crystal to vary. If the transmittance of the liquid crystal varies, sufficient contrast cannot be maintained, and the reliability of the aperture cannot be ensured.
[0042] On the other hand, in the area where the columnar spacers are arranged, the liquid crystal cannot be controlled, and light leakage occurs. In the configuration of Fig. 10, the area where the columnar spacers 210 are arranged in the periphery overlaps with the light-shielding film 201 in a plan view, so the problem of light leakage does not occur.
[0043] Fig. 11 is a plan view showing a first embodiment of the first embodiment that addresses this problem. Fig. 11 differs from Fig. 5 in that columnar spacers 210 are arranged only in the area overlapping the rectangular upper layer electrode 103 arranged in the center. By arranging the columnar spacers 210 not over the entire pattern area but only in the central area, a decrease in the contrast of the entire coded aperture pattern 30 is prevented. On the other hand, arranging the columnar spacers 210 in the central area is most effective in addressing the variation in thickness of the liquid crystal layer 300.
[0044] Fig. 12 is a cross-sectional view taken along the line BB in Fig. 11. In Fig. 12, a columnar spacer 210 is disposed in the center of the pattern region, so that the thickness of the liquid crystal layer 300 is almost constant over the entire surface. The other configurations in Fig. 12 are the same as those described in Fig. 10. Note that in Fig. 12, the columnar spacer 210 is made of a transparent material.
[0045] 12, the columnar spacers 210 cause light leakage in the central region. However, it is possible to reduce the area of the region (A1) where the columnar spacers 210 are arranged. Furthermore, by making this portion of the coded aperture pattern 30 a white pattern instead of a black pattern, it is possible to reduce the light leakage caused by the columnar spacers 210.
[0046] Fig. 13 is a plan view showing a second embodiment of the first embodiment, which addresses the problem of variation in the gap between the TFT substrate 100 and the counter substrate 200 in the liquid crystal aperture. Fig. 13 differs from Fig. 11 in that black columnar spacers 220 are arranged in place of transparent columnar spacers 210 in the area overlapping the rectangular upper layer electrode 103 arranged in the center. The other configurations are the same as those in Fig. 11.
[0047] FIG. 14 is a cross-sectional view taken along CC in FIG. 13. In FIG. 14, the columnar spacer 220 is disposed in the center of the pattern region, so the layer thickness of the liquid crystal layer 300 is approximately the same across the front surface. The other configurations in FIG. 14 are the same as those described in FIG. 10. In FIG. 14, the columnar spacer 220 is black, so there is no effect of light leakage that passes through the spacer itself. The light leakage is only due to the effect of disturbance in the light distribution of the liquid crystal molecules around the columnar spacer 220 caused by the presence of the columnar spacer 220. Therefore, when the region where the columnar spacer 220 is disposed is displayed in black, the effect of light leakage can be reduced compared to the configuration of the first embodiment.
[0048] Fig. 15 is a plan view showing a third embodiment of the first embodiment, which addresses the problem of variation in the distance between the TFT substrate 100 and the counter substrate 200 in the liquid crystal aperture. Fig. 15 differs from Fig. 13 in that a light-shielding film 201 is formed so as to overlap the portion of the central upper electrode 103 where the black columnar spacer 220 is arranged. This makes it possible to eliminate light leakage caused by the columnar spacers 220 or 210. However, it is necessary to design the coded aperture pattern 30 so that the portion where the light-shielding film 201 is formed always becomes a black pattern.
[0049] 15, a black pattern is displayed on the counter substrate 200 side, overlapping with the upper layer electrode 103 formed in the center. That is, the light-shielding film 201 is formed on the counter substrate 200, and the upper layer electrode 103 is formed on the TFT substrate 100. Therefore, when the TFT substrate 100 and the counter substrate 200 are overlapped, an alignment error occurs. This error needs to be estimated to be about 10 μm. Therefore, in order to prevent the light-shielding film 201 from protruding from the upper layer electrode 103 in a plan view when the TFT substrate 100 and the counter substrate 200 are combined, it is better to design the diameter of the light-shielding film 201 to be smaller than the upper layer electrode 103 by about 10 μm on each side in both the vertical and horizontal directions.
[0050] 15, the distance dx between the x-direction end of light-shielding film 201 and the x-direction end of upper layer electrode 103 is 10 μm or more, and the distance dy between the y-direction end of light-shielding film 201 and the y-direction end of upper layer electrode 103 is 10 μm or more. In other words, the diameter of light-shielding film 201 in the x direction is 20 μm or more smaller than the diameter of upper layer electrode 103 in the x direction, and the diameter of light-shielding film 201 in the y direction is 20 μm or more smaller than the diameter of the upper layer electrode in the y direction. Note that the x direction can also be referred to as a first direction, and the y direction can also be referred to as a second direction perpendicular to the first direction.
[0051] Fig. 16 is a DD cross-sectional view of Fig. 15. Fig. 16 differs from Fig. 14 of the second embodiment in that a light-shielding film 201 is formed in the center of the counter substrate 200. Therefore, in the third embodiment, light leakage can be completely suppressed in the portion where the columnar spacers 220 are arranged. Another feature of Fig. 16 is that all the columnar spacers 220 are arranged so as to overlap with the light-shielding film 201, so that all the columnar spacers 220 can have the same height. In Fig. 14, if all the columnar spacers 220 have the same height, the layer thickness d1 of the liquid crystal at the center becomes smaller than the layer thickness d2 at the periphery by the amount of the light-shielding film 201.
[0052] Fig. 17 is a detailed cross-sectional view corresponding to the cross section taken along line DD in Fig. 15. Fig. 17 differs from Fig. 16 in that Fig. 17 shows a cross-sectional view of a lower electrode 101, an interlayer insulating film 102, and an upper electrode 103 formed on a TFT substrate 100. The cross-sectional configuration of the electrodes on the TFT substrate 100 is similar to that in the first and second embodiments. Note that a common electrode is formed in a planar shape on the opposing substrate 200, but is omitted in Fig. 17.
[0053] In FIG. 17, a lower layer electrode 101 is formed on a TFT substrate 100. An interlayer insulating film 102 is formed to cover the lower layer electrode 101, and an upper layer electrode 103 is formed on the interlayer insulating film 102. The upper layer electrode 103 formed in the center of the TFT substrate 100 overlaps with the columnar spacer 220 and the light-shielding film 201 formed on the counter substrate 200 in a plan view. In FIG. 17, a voltage that produces a black display is applied to the upper layer electrode 103 formed in the center of the TFT substrate 100. The light-shielding film 201 formed by overlapping also produces a black display, but the end of the upper layer electrode 103 extends outward by dx on one side beyond the end of the light-shielding film 201. This is to absorb the combination error of the TFT substrate 100 and the counter substrate 200.
[0054] In the third embodiment shown in FIGS. 15, 16 and 17, the black columnar spacers 220 are used as the columnar spacers, but the transparent columnar spacers 210 may also be used. EXAMPLES
[0055] In the first embodiment, a liquid crystal diaphragm with a rectangular outer shape is used as the diaphragm 20. Incidentally, since a lens has a spherical surface, it is easier to achieve precision if the shape of the diaphragm is a circle or a polygon close to a circle. In the example of the first embodiment, if the diaphragm for adjusting the amount of light is made close to a circle, it is necessary to prepare a second diaphragm for the light-shielding frame 21 separately.
[0056] Example 2 has a configuration in which a nearly circular second aperture and a coded aperture pattern 30 are formed within the same liquid crystal aperture. In FIG. 18, the outer shape of the liquid crystal aperture is rectangular. A sealant and a light-shielding film 201 are formed in a frame shape, and columnar spacers are further arranged. A circular light-transmitting region is formed on the inside, which corresponds to the second aperture. A coded aperture pattern 30 is formed within the second aperture. The coded aperture pattern 30 is as described in Example 1. FIG. 18 shows the configuration of embodiment 1 of Example 1.
[0057] 18, light-shielding frame 21 defining the circular light-transmitting region may be formed by lower layer electrode 101 or upper layer electrode 103, or may be formed by light-shielding film 201. Note that, although the light-transmitting region defined by light-shielding frame 21 in FIG. 18 is circular, it is not limited thereto and may be a polygon having five or more sides as necessary.
[0058] In this way, according to the second embodiment, all of the components required for the diaphragm can be configured by a single liquid crystal diaphragm. EXAMPLES
[0059] In the first embodiment, the lower layer electrode 101 and the upper layer electrode 103, which are fixed patterns, are configured in two layers, and thus the coded aperture pattern 30 is formed. By dividing the lower layer electrode 101 and the upper layer electrode 103 in various ways, coded aperture patterns 30 of various shapes can be formed even with fixed electrodes.
[0060] On the other hand, in a liquid crystal display device, pixels are formed in a matrix in the effective area to form an image. The difference between a liquid crystal display device and a liquid crystal diaphragm is that, although color images and grayscales are not necessary in a liquid crystal diaphragm, the coded diaphragm pattern to be formed is small in shape. However, in recent years, with the development of high-definition technology, it is possible to manufacture with a pixel pitch of 30 μm or less, and pixel pitches up to about 10 μm have been developed as necessary. If the pixel pitch is high-definition of 30 μm or less, it is possible to form a small image such as the coded diaphragm pattern 30 by using a matrix structure. Note that a pixel pitch of 30 μm or less means that the pixel pitch is 30 μm or less in both the extending direction of the scanning lines and the extending direction of the video signal lines. An example of forming the coded diaphragm pattern 30 by using a liquid crystal diaphragm having a matrix structure will be described below.
[0061] Fig. 19 is a plan view of the liquid crystal aperture. In Fig. 19, the TFT substrate 100 and the counter substrate 200 are bonded at their peripheries with a sealant, and liquid crystal is sealed inside. A peripheral light-shielding region 21 and a pattern region 22 are formed in the region where the TFT substrate 100 and the counter substrate 200 overlap.
[0062] The TFT substrate 100 is formed to be larger than the counter substrate 200, and a portion of the TFT substrate 100 that does not overlap with the counter substrate 200 is a terminal region 160. In the terminal region 160, a driver IC 165 that drives the liquid crystal diaphragm and the like are arranged.
[0063] 19, on the TFT substrate 100, scanning lines 151 extend in the horizontal direction (x direction) and are arranged in the vertical direction (y direction). Signal lines 152 extend in the vertical direction and are arranged in the horizontal direction. Pixels 153 including pixel electrodes are formed in the areas surrounded by the scanning lines 151 and the signal lines 152. A voltage is applied between the pixel electrodes 153 and a common electrode formed on the opposing substrate to orient the liquid crystal molecules in a required direction, thereby performing a shutter action against light.
[0064] In the region where the TFT substrate 100 and the counter substrate 200 overlap, a frame-shaped peripheral light-shielding region 21 is formed by a light-shielding film (hereinafter also referred to as a black matrix) around the periphery of the counter substrate 200. A light-shielding region is also formed in the pattern region 22, but the light-shielding region formed in the pattern region 22 is formed by a liquid crystal aperture, and its position and shape are variable. On the other hand, the frame-shaped light-shielding region 21 formed in the counter substrate 200 is formed by a black matrix, and therefore its shape is constant.
[0065] 20 is a plan view of a pixel 153. In FIG. 20, a pixel electrode 154 is formed in an area surrounded by a scanning line 151 and a signal line 152. A TFT (Thin Film Trnsistor) that is switched by a scanning signal is formed between the pixel electrode 154 and the signal line 152. The TFT is formed of a gate electrode 110 branched from the scanning line 151, a semiconductor film 111, a drain electrode 112 branched from the signal line 153, and a source electrode 113, and the source electrode 113 is connected to the pixel electrode 154 via a through hole 114. A signal is sent to the pixel electrode 154 via the signal line 152 and the TFT to open or close the pixel 153, thereby forming the coded aperture pattern 30.
[0066] Fig. 21 is a cross-sectional view of the liquid crystal diaphragm. In Fig. 21, a liquid crystal layer 300 is sandwiched between a TFT substrate 100 on which a pixel electrode 154 is formed and a counter substrate 200 on which a common electrode 203 is formed. The TFT substrate 100 and the counter substrate 200 are bonded with a sealant 150. A pixel 153 of the liquid crystal diaphragm is formed between the pixel electrode 154 and the common electrode 203.
[0067] A frame-shaped light-shielding film 21 made of a black matrix is formed around the periphery of the counter substrate 200. The TFT substrate 100 is formed larger than the counter substrate 200, and the portion where the TFT substrate 100 does not overlap with the counter substrate 200 is a terminal region 160, in which a driver IC 165 is arranged.
[0068] Since liquid crystal can control only polarized light, a first polarizing plate 410 is attached to the TFT substrate 100 side, and a second polarizing plate 420 is attached to the counter substrate 200 side. Therefore, when a liquid crystal diaphragm is used, the use of the polarizing plates causes a loss of light.
[0069] 21 omits the gap between the TFT substrate 100 and the counter substrate 200, i.e., the columnar spacers 210 for keeping the liquid crystal layer thickness constant. However, if the columnar spacers in the pattern region 22 were not present, the liquid crystal layer would fluctuate and the contrast would deteriorate, as described in FIG. 10 of the first embodiment.
[0070] On the other hand, the pixel pitch of the liquid crystal diaphragm is very small, at 30 μm or less, in order to accommodate small patterns. However, the diameter of the columnar spacer 30 cannot be reduced proportionally to the pixel pitch. In that case, as shown in FIG. 22, the ratio of the columnar spacers 210 and 220 to the size of the pixel 153 becomes large, which affects the transmittance of the pixel and makes it impossible to form an accurate pattern.
[0071] Therefore, as explained in Example 1, the influence of the columnar spacers is reduced by concentrating the columnar spacers in the center of the pattern region 22 and designing the pattern so that this portion displays black or white. In Fig. 23, black columnar spacers 220 are used as the columnar spacers, and a light-shielding film 201 made of a black matrix is formed by overlapping the black columnar spacers. That is, this is an application of the third embodiment of Example 1. However, the columnar spacers may be made of a transparent material.
[0072] Fig. 24 is an E-E cross-sectional view of Fig. 23. In Fig. 24, the TFT substrate 100 and the counter substrate 200 are bonded with a sealant 150. A liquid crystal layer 300 is sandwiched inside. The gap between the TFT substrate 100 and the counter substrate 200 is maintained by the peripheral sealant 150 and a columnar spacer 220 arranged in a narrow region at the center of the pattern region 22.
[0073] A3 in Fig. 24 is the width of the sealant 150. In Fig. 24, a columnar spacer 220 may be disposed inside and very close to the sealant 150. In this case, the outer end of A2 in Fig. 24 coincides with the position of the columnar spacer very close to the sealant.
[0074] An advantage of the third embodiment is that the coded aperture pattern 30 can be easily changed. In addition to the coded aperture pattern 30, the aperture that determines the amount of incoming light can also be easily formed by one liquid crystal aperture. FIG. 25 is a plan view showing an example of this configuration. In FIG. 25, the outer shape of the liquid crystal aperture is rectangular, but a circular pattern area is formed by the peripheral light-shielding film 21. The coded aperture pattern is formed within the circular pattern area. Note that the pattern area is not limited to a circle, and may be configured as a polygon having 5 or more sides.
[0075] Furthermore, instead of using the peripheral light-shielding film 21, a black display can also be used to form an aperture that regulates the amount of incoming light. [Explanation of symbols]
[0076] 10...lens, 20...diaphragm, 21...frame made of light-shielding film, 22...pattern area 22, 30...coded aperture pattern, 40...image capture target, 50...optical sensor, 100...TFT substrate, 101...lower layer electrode, 102...interlayer insulating film, 103...upper layer electrode, 110...gate electrode, 111...semiconductor film, 112...drain electrode, 113...source electrode, 114...through hole, 150...sealing material, 151...scanning line, 152...signal line, 153...pixel, 154...pixel electrode, 160...terminal area, 165...driver IC, 200...opposite substrate, 201...light-shielding film (black matrix), 202...overcoat film, 203...common electrode, 210...columnar spacer, 220...black columnar spacer, 300: liquid crystal layer, 410: first polarizing plate, 420: second polarizing plate
Claims
1. An imaging device having a lens, a light sensor that receives light, and an aperture disposed adjacent to the lens and between the lens and an imaging target, the diaphragm is composed of a liquid crystal layer sandwiched between a first substrate and a second substrate, a peripheral light-shielding frame, and a liquid crystal diaphragm in which a pattern region is formed; A lower layer electrode, an interlayer insulating film, and an upper layer electrode are formed on the first substrate in this order; the upper layer electrode has a first electrode formed in an area including the center of the pattern area, and a second electrode disposed with a gap between the first electrode and the second electrode; When viewed in a plan view, the gap and the lower electrode overlap, a first light-shielding film constituting the light-shielding frame is formed around the second substrate, and a first columnar spacer is formed between the first light-shielding film and the first substrate in a plan view; 2. An imaging device comprising: a first electrode and a second substrate, the first electrode and the second substrate being electrically connected to each other through a first insulating film;
2. 2. The imaging device according to claim 1, wherein, in a plan view, no columnar spacer is formed between the upper electrode and the second substrate except in a portion where the first electrode is formed.
3. 2. The imaging device according to claim 1, wherein the second columnar spacer is black.
4. 2 . The imaging device according to claim 1 , wherein a second light-shielding film is formed on the second substrate so as to overlap the first electrode of the first substrate in a plan view.
5. 5. The imaging device according to claim 4, wherein, in a plan view, an outer periphery of the second light-shielding film is located inside an outer periphery of the first electrode.
6. 6. The imaging device according to claim 5, wherein the second columnar spacer overlaps with the second light-shielding film.
7. 2. The image pickup device according to claim 1, wherein the first electrode and the second electrode form a part of a coded aperture pattern.
8. 2. The imaging device according to claim 1, wherein the second electrode is further divided into a plurality of electrodes.
9. A common electrode is formed on the second substrate, 2. The image pickup device according to claim 1, wherein, when a first pattern is formed in the pattern region, the liquid crystal layer is controlled by an electric field between the upper electrode and the common electrode.
10. A common electrode is formed on the second substrate, 2. The image pickup device according to claim 1, wherein, when a second pattern is formed in the pattern region, the liquid crystal layer is controlled by an electric field between the lower electrode and the common electrode.
11. An imaging device having a lens, a light sensor that receives light, and an aperture disposed adjacent to the lens and between the lens and an imaging target, the diaphragm has a rectangular outer shape, is configured as a liquid crystal diaphragm in which a liquid crystal layer is sandwiched between a first substrate and a second substrate, and in which a pattern area is formed that is defined by a peripheral light-shielding frame; The pattern area is a polygon having 5 or more sides or a circle, In the pattern region, scanning lines extend in a first direction and are arranged in a second direction, video signal lines extend in the second direction and are arranged in the first direction, pixels are formed in regions surrounded by the scanning lines and the video signal lines, and a pitch of the pixels in the first direction and the second direction is 30 μm or less, a columnar spacer defining a distance between the first substrate and the second substrate is formed only in a first region including a central portion of the pattern region; 11. An imaging device, comprising: a first region having a width that is equal to or smaller than 30% of a width of the pattern region in the first direction;
12. 11. An imaging device, comprising: a first region having a width that is equal to or smaller than 30% of a width of the pattern region in the second direction;