JP2011185782A - Polarization image sensor and manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarization image sensor that reduces crosstalk generated between a fine filter and the corresponding light receiving element, to enhance image quality. <P>SOLUTION: The polarization image sensor 50 includes an image sensor 7 in which a plurality of light receiving elements 6 is arrayed on one-dimensional or two-dimensional basis, microlenses (optical elements) 3 arranged opposed to respective light receiving elements 6 of the image sensor 7, a polarization filter 1 composed of minute filters 21, 22 having at least two or more types of different polarization characteristics, in a plurality of regions corresponding to the light receiving elements 6 of the image sensor 7. Connections are established between respective minute filters 21, 22 and respective microlenses 3 by transparent resin members 2. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a polarization image sensor, and more particularly to a technique and a manufacturing method for reducing crosstalk between a micro filter and a light receiving element.

  Conventionally, in order to obtain information on an object that cannot be obtained with a normal black-and-white image or color image, it has been studied to use a special filter mounted on a general-purpose image sensor. This is called image sensing. As an example, image acquisition is performed by combining a polarization filter with an image sensor, and information such as object distortion and surface tilt that cannot be obtained with a normal black-and-white or color image by image processing. The way to get it is being considered. Since polarized light is divided into two orthogonal components, when acquiring a polarization image, it is necessary to acquire images corresponding to the two components. As the method, the image is acquired in two steps by changing the filter, or, as disclosed in Patent Document 1, two components are separated by a polarization beam splitter or the like, and two image sensors are used. There is a way to get images. On the other hand, in Patent Document 2, as shown in FIG. 4, a polarizing filter 401 of a type in which filters 403, 405, and 406 that transmit different polarized light are arranged corresponding to individual pixels of the image sensor 402 is provided in the image sensor 402. By attaching it, it is possible to acquire polarized images of different components simultaneously from one image sensor.

However, the actual image sensor has a shape as shown in FIG. 5, and when the polarizing filter 401 is attached, a plurality of adjacent pixels (light receiving units) 31 of the opposing image sensor 402 are arranged. There is a problem in that the image quality deteriorates because the light circulates from the filter (crosstalk). In order to prevent crosstalk, it is necessary to make the polarizing filter 401 as close to the image sensor 402 as possible. Is already about 2 to 3 μm, so that the crosstalk component remains even when the polarizing filter 401 is brought into close contact with the surface of the image sensor 402. Further, since the pixel size of the image sensor 402 is usually about several microns, it is difficult to accurately align the polarizing filter 401 and the image sensor 402, which causes crosstalk.
Similarly, countermeasures are being studied for multi-channel optical connections that have crosstalk problems. For example, in Patent Document 3, a resin substrate having a large number of fine holes is used as a waveguide to prevent crosstalk between adjacent light receiving elements and a light source, but the interval between light receiving elements is on the order of 100 μm. However, the same technique has a problem that it is difficult to use the pixel spacing of the image sensor.

The present invention has been made in view of such a problem, and is compatible with a micro filter by optically connecting an optical element corresponding to a pixel of an image sensor and a corresponding micro filter by a transparent resin member. An object of the present invention is to provide a polarization image sensor that improves image quality by reducing crosstalk generated with a light receiving element.
Another object is to provide a manufacturing method capable of easily aligning a filter and an image sensor.

In order to solve this problem, the present invention provides an image sensor in which a plurality of light receiving elements are arranged one-dimensionally or two-dimensionally, an optical element arranged to face each of the light receiving elements, A polarizing image sensor comprising: a polarizing filter that is arranged in a plurality of regions corresponding to the light receiving elements of the image sensor and configured by at least two kinds of micro filters having different polarization characteristics, each micro filter And the optical elements are connected by a transparent resin member.
According to a second aspect of the present invention, the micro filter is a wire grid.
According to a third aspect of the present invention, a color filter is laminated between the light receiving element and the optical element.
According to a fourth aspect of the present invention, the color filter is disposed in close contact with the polarizing filter.
According to a fifth aspect of the present invention, the image sensor is a backside illumination type.
Claim 6 is a method of manufacturing a polarization image sensor according to any one of claims 1 to 5, wherein a pattern separated for each pixel by a transparent thermoplastic resin is formed on the polarization filter, And a step of placing the polarizing filter on the image sensor and a step of applying heat to the thermoplastic resin at a temperature equal to or higher than a temperature at which the thermoplastic resin softens.

According to the present invention, the light that has passed through the minute region of the filter is guided through the resin member and reaches the pixels of the image sensor, so that the occurrence of crosstalk can be reduced.
Further, since the connection portion is formed by reflow of the resin member, the manufacturing is easy, and the alignment position is corrected in a self-aligning manner, so that the alignment can be easily performed.
Since the wire grid is used as the polarizing filter, the thickness of the filter itself is thin, the distance between the light receiving element of the image sensor and the filter is narrowed, and crosstalk can be reduced.
Further, by forming the color filter on the polarizing filter side, the distance between the filter and the light receiving element can be narrowed, and the light utilization efficiency can be improved while reducing crosstalk.
Further, since the backside illumination type in which the distance from the sensor surface to the light receiving element is short is used as the image sensor, it is possible to improve the light utilization efficiency while reducing crosstalk.

(A) is sectional drawing which shows the structure of the polarization image sensor which concerns on one Embodiment of this invention, (b) It is a figure explaining the optical path of incident light. (A) is a diagram showing step 1, (b) is a diagram showing step 2, (c) is a diagram showing step 3, (d) is a diagram showing step 4, and (c) 'is alignment in step 3. The shifted figure, (d) ′, is a figure in which the alignment is corrected. (A) is a diagram showing a case where a wire grid is used as a polarizing filter, (b) is a diagram showing an example in which a color filter on the image sensor side is moved to the polarizing element filter side, and (c) is a back surface on the image sensor. It is a figure which shows the structure using an irradiation type | mold. It is a figure which shows the structure of patent document 2. FIG. It is a figure explaining a mode that crosstalk occurs.

  Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the components, types, combinations, shapes, relative arrangements, and the like described in this embodiment are merely illustrative examples and not intended to limit the scope of the present invention only unless otherwise specified. .

FIG. 1A is a cross-sectional view showing a configuration of a polarization image sensor according to an embodiment of the present invention. The polarization image sensor 50 includes an image sensor 7 in which a plurality of light receiving elements 6 are arranged one-dimensionally or two-dimensionally, a microlens (optical element) 3 disposed to face each light-receiving element 6, and an image sensor. And a plurality of regions corresponding to the seven light receiving elements 6, the polarizing filter 1 including the microfilters 21 and 22 having at least two different polarization characteristics, and each microfilter 21 and 22 and each microlens. 3 was connected by a transparent resin member 2.
That is, the polarization image sensor 50 of the present embodiment is characterized in that the corresponding minute regions of the minute filters 21 and 22 and one pixel of the image sensor 7 are individually connected by a transparent resin member. In the case of such a configuration, as shown in FIG. 1B, incident light 10 to 13 that has passed through the minute regions of the minute filters 21 and 22 are guided through the resin member 2 and the light receiving element ( Since the pixel reaches 6), the occurrence of crosstalk can be reduced.
In order to create such a shape, a structure such as a microlens separated in units of pixels is formed on the surface of the image sensor 7, and a thermoplastic resin pattern separated in units of pixels is also formed on the polarizing filter side. After aligning and superposing them, the thermoplastic resin may be reflowed by heating.

  Further, if a wire grid is used as the polarizing filter 1, the thickness of the polarizing filter itself can be reduced and the distance between the light receiving element 6 of the image sensor 7 and the polarizing filter 1 can be reduced, so that crosstalk can be further reduced (see FIG. 3 (c)). In a color image sensor, since the color filter 4 is usually formed on the surface of the image sensor 7, the distance between the polarization filter 1 and the light receiving element 6 can be obtained by forming the color filter 4 on the polarization filter 1 side. The light utilization efficiency can be improved by narrowing (see FIG. 3B). If a backside illumination type with a short distance from the sensor surface to the light receiving element 6 is used as the image sensor, the light utilization efficiency can be further improved (see FIG. 3D).

FIG. 2 is a diagram for explaining the manufacturing process of the polarization image sensor of the present invention.
First, a pattern separated for each pixel by the transparent thermoplastic resin 2 is formed on each of the microfilters 21 and 22 (FIG. 2A) (FIG. 2B). The shape of the pattern may be circular or quadrangular, but the patterns are separated to such an extent that adjacent patterns are not combined during reflow. Any resin member may be used as long as it is transparent, thermoplastic, and easily patterned. Here, a type of acrylic photoresist that can be used as a microlens after reflow is used. Next, a pattern formed of the thermoplastic resin 2 on the fine filter is disposed on the image sensor 7 (FIG. 2C). At this time, alignment is performed with respect to the light receiving element 6 of the image sensor 7 so that a predetermined minute filter is disposed. When the resin member 2 is finally reflowed by heating, the image sensor 7 and the filter are coupled in units of pixels (FIG. 2D). At the time of reflow, a force acts so that the surface area becomes smaller due to the surface tension. Therefore, even if misalignment occurs, for example, as shown in FIG. 2 (d) ′).

FIG. 3A is a diagram showing a case where a wire grid is used as a polarizing filter. The wire grid 23 is a polarizing filter in which fine metal wires are arranged in an array, and an aluminum fine wire pattern having a thickness of about 0.2 μm and a period of 150 can be used for visible light. When the wire grid is used, the filter itself can be made very thin. For example, when the light 14 reaches the light receiving element 6 through the path shown in FIG. 3A, two filters having different polarization characteristics in the thickness direction are used. Although the light that has passed through the region reaches the light receiving element 6, the filter thickness of the wire grid 23 is thin, so that the influence of the light passing through such a path can be reduced.
FIG. 3B is a diagram illustrating an example in which the color filter on the image sensor side is moved to the polarizing element filter side. With such a configuration, the optical path length in the image sensor 7 can be shortened, so that the light reflected or absorbed by the metal of the wiring layer 5 is reduced and the light utilization efficiency can be improved.
FIG. 3C is a diagram showing a configuration using a backside illumination type for the image sensor. Also in this case, the optical path length in the image sensor is shortened, and the influence of the wiring layer 5 is completely eliminated, so that the light use efficiency of the polarization image sensor 53 can be improved.

DESCRIPTION OF SYMBOLS 1 Polarization filter, 2 Resin member, 3 Micro lens, 4 Color filter, 5 Wiring layer, 6 Light receiving element, 7 Image sensor, 10-13 Incident light, 20 Substrate, 21, 22 Fine filter, 23 Wire grid, 50-53 Polarized image sensor

JP 2000-035403 A JP 2007-086720 A JP 2008-199055 A

Claims (6)

An image sensor in which a plurality of light receiving elements are arranged one-dimensionally or two-dimensionally, an optical element arranged to face each of the light receiving elements, and a plurality of regions corresponding to the light receiving elements of the image sensor, A polarization image sensor comprising a polarization filter composed of at least two kinds of micro filters having different polarization characteristics,
A polarization image sensor, wherein each microfilter and each optical element are connected by a transparent resin member.   The polarization image sensor according to claim 1, wherein the micro filter is a wire grid.   The polarization image sensor according to claim 1, wherein a color filter is laminated between the light receiving element and the optical element.   The polarization image sensor according to claim 1, wherein the color filter is disposed in close contact with the polarization filter.   The polarization image sensor according to any one of claims 1 to 4, wherein the image sensor is a backside illumination type. A method for manufacturing a polarization image sensor according to any one of claims 1 to 5,
Forming a pattern separated for each pixel by a transparent thermoplastic resin in the polarizing filter;
Disposing the polarizing filter on the image sensor;
Applying heat above the temperature at which the thermoplastic resin softens to the thermoplastic resin;
A method of manufacturing a polarization image sensor, comprising:

Images