JP2000125310A - Solid-state image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid-state image pickup device capable of supplying an image with satisfactory color balance, without causing troublesome problems of switching of mechanical filters and color S/N ratio. SOLUTION: The ratio of sensitivity balance of each color is made e.g. to set at S(R):S(G):S(B)=1:1:1 so as to uniformize the S/N ratio of each color by adjusting the shape of micro lenses 12, that is adjusting the curvatures in the order r(R), r(G), r(B), located in front of light-receiving elements 16a in response to a photoelectric conversion efficiency different from each color of the light-receiving elements 16a, caused by interposing color filters 14 in this solid-stage image pickup device 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state imaging device for providing a color image by photoelectrically converting light obtained by subjecting incident light from a field into three primary colors, RGB, by an imaging means, and more particularly to, for example, the present invention. The present invention is suitably applied to a solid-state imaging device including an imaging unit in which charge-coupled devices are two-dimensionally arranged.

[0002]

2. Description of the Related Art Conventionally, when a light receiving element of a solid-state image pickup device performs color image pickup, it performs photoelectric conversion by receiving incident light from an object scene transmitted through a color filter. In this case, a problem is how to reproduce the color of the subject. In this color reproduction, the light applied to the subject, the type of illumination, and the like are involved as important factors. The factor for these is generally expressed in color temperature.

In the case of color imaging, solid-state imaging devices faithfully reproduce colors by separating them into three colors (RGB). For this reason, when an image is captured under sunlight outdoors and under illumination of a white lamp indoors, the color balance is naturally changed because the color balance is not particularly considered. In practice, for example, when incident light having a color temperature of 5000K to 6000K is normally incident and a charge-coupled device (CCD) is used in a solid-state imaging device, the color balance is determined by the level of the obtained imaging signal for each RGB of each color. It is known that the ratio has a relationship of R: G: B = 0.7: 1: 0.8. As described above, since the color balances are different, when the white balance is obtained by the signal processing unit at the subsequent stage, the level ratio is set to R: G: B =
The gain is adjusted so that it becomes 1: 1: 1.

[0004]

However, a noise component of a specific color is emphasized by the above-described gain adjustment. Images with different S / N ratios for each color
There is a problem that the image becomes bad in N. Each time a color image is taken, it is necessary to correct the color according to the color temperature.
When color correction is performed optically for this problem, various color temperature conversion filters in which the density of a color filter is adjusted are used. This color temperature conversion filter includes a type that is fitted in front of the imaging lens and a type that is built in between the imaging lens and the color separation filter and that rotates the turret to select desired characteristics. However, these methods have the trouble of mechanically changing the color temperature conversion filter.

The present invention solves the drawbacks of the prior art and provides a solid-state imaging device capable of supplying an image with a good color balance without causing troubles of troublesome mechanical filter switching and color S / N. The purpose is to:

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an image pickup means in which a plurality of light receiving elements for generating an electric signal corresponding to incident light are two-dimensionally arranged; Each of the elements has a color separation filter segment arranged in accordance with the separation color, and each of the color filter segments converts incident light from the object scene to one of the colors in each of the separation colors. A color separation filter that is decomposed into incident light and is incident on each of the plurality of light receiving elements; and a color separation filter that is disposed on the side of the light receiving element on the side of the incident light and has a shape corresponding to each photoelectric conversion efficiency of the separated color of the light receiving element. And an optical member.

Here, the light guide member is shaped so as to maximize the amount of the incident light in the separation color in which the sensitivity of the light receiving element is the lowest, and the irradiation amount of the incident light increases as the sensitivity of each of the other separation colors increases. Is preferable. For example, in the case of color separation into primary color signals, the color R, B, and B should be shaped so that the most incident light can be obtained according to the sensitivity of the light receiving element.
It is preferable that the shape is such that the irradiation amount of the incident light is reduced in the order of G. Thereby, the obtained RGB signals can be evenly balanced.

The light guide member is a light condensing means for condensing the incident light on the side of the incident light of the color separation filter corresponding to the light receiving element. It is desirable to use light condensing means formed according to the sensitivity of each light receiving element. From this, since the amount of light incident on the light receiving element is adjusted for each separation color, as a result, sensitivity control is performed.

Further, the light guide member uses a light shielding member that shields the image pickup means and opens only the light receiving region of the light receiving element, and the light shielding member is the light receiving region in the separated color having the lowest sensitivity of the light receiving element. It is advantageous to maximize the aperture ratio and to decrease the aperture ratio as the sensitivity of each of the other separated colors increases. For example, when performing color separation into primary color signals, the aperture ratio of the light receiving area is maximized with the color R according to the sensitivity of the light receiving element, the light quantity of the incident light is made larger than the normal light quantity, and the light quantity is increased in the order of the colors B and G. Should be reduced. As a result, the amount of incident light is adjusted for each color as described above, and thus sensitivity control is performed.

The shape of the light-collecting means may be defined by the curvature of the light-collecting surface of the light-collecting means or the size of the cross-sectional area of the incident light passing through the light-collecting means.

Incidentally, the light receiving element may be applied to a so-called honeycomb arrangement in which the center of the geometrical shape of the light receiving element is shifted by half the pitch in the row direction and the column direction.

The solid-state imaging device according to the present invention is a light-guiding member in which the shape of the light-guiding member is taken into consideration in accordance with the photoelectric conversion efficiency different for each color of the light-receiving element caused by passing through each color separation filter in the color separation filter segment. By forming this light guide member on the front surface of the light receiving element, the ratio of the sensitivity balance of each color, for example, S (R): S (G): S (B) = 1:
The S / N ratio of each color is made 1: 1 so that it can be made uniform.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the solid-state imaging device according to the present invention will be described below in detail with reference to the accompanying drawings.

In the solid-state imaging device according to the present invention, for example, a shape of a micro lens as an on-chip lens, a shielding member, or the like, which is arranged on an imaging unit (the front surface of the light receiving element), is changed according to a color through a color separation filter. It is characterized in that the sensitivity for each color is made uniform by making the incident light amount in inverse proportion to the sensitivity of the different light receiving elements different so as to be received.

The solid-state imaging device 10 is provided with a color signal processing unit (not shown) in addition to the microlens 12, the color filter 14, and the imaging unit 16, which form part of an optical system. The color signal processing section includes a gamma conversion section, an A / D conversion section, and a signal processing section. In the present embodiment, the imaging unit 16 including the features of the present invention and members around the imaging unit 16 will be described. In the solid-state imaging device 10, the light receiving element of the imaging unit 16 may be any image sensor such as a charge coupled device (CCD) or a metal oxide semiconductor (MOS).

The micro lens 12 is a lens provided for each element for condensing incident light transmitted through the optical system so as to efficiently supply the light to each light receiving element. Micro lens 12
Is a cross section taken along the breaking line AA shown in FIG. 1 (a) (FIG. 1 (b)
On the surface 18a of the transparent member 18 as shown in FIG. In this embodiment, the microlens 12 is used for color temperature of daytime photographing (5000K to 6000K) and color temperature of tungsten (W) light used for strobe photographing (6000K).
Since the sensitivity ratio S of the signal obtained for each RGB at the color temperature at which shooting is most frequent is 0.7, 1, 0.8, respectively,
Contrary to the magnitude of the sensitivity ratio S (S (G)> S (B)> S (R)), make the lens curvature r (r (R)> r (B)> r (G)) smaller in order. (See FIG. 1 (b)). The curvature relationship of this lens is such that a lens having a larger curvature forms a larger lens. That is, as shown in FIG.
12 is the largest, and the micro lens 12 of the color G is the smallest. This lens is formed on the surface 18a of the transparent member 18 by arranging the lens member 20 in the same manner as in a conventional method and subjecting the lens member 20 to a heat treatment.

The color filters 14 are, for example, three primary colors RG
Filters B for color separation are two-dimensionally arranged corresponding to each light receiving element. The color filter 14 in FIG.
The case of a vertical stripe pattern is shown. The color filters corresponding to the respective light receiving elements are all of the same size (see FIG. 1B). The microlenses 12 are not shown in the plan view of FIG. 1A in order to avoid complication of the drawing.

The imaging unit 16 includes a two-dimensionally arranged light receiving element 16a.
Are formed immediately below the color filters. In this case, each light receiving element 16a is provided corresponding to the opening 17a of the light shielding member 17. In this case, the opening 17 shown in FIG.
a have the same opening area without being limited to the color. Except for the area of the opening 17a, all light is shielded. Therefore, the light shielding member 17 is
The transfer gate 16a for transferring the signal charges from a to the vertical transfer path 16d, the electrode section 16c for supplying a timing signal (drive signal) to the transfer gate 16a and the vertical transfer path 16d, and the vertical transfer path 16d are all shielded from light. The light blocking member 17
A material such as aluminum is used.

With such a configuration, the imaging unit 16
For example, when the same light amount is supplied to the light receiving element 16a via the microlens 12, the light receiving element 16a can adjust the light amount supplied by the microlens 12, so that
The difference in signal charge caused by the difference in color of the color filter 12 can be eliminated. Each light receiving element 16a that has generated a uniform signal charge transfers a signal charge according to a drive signal from the electrode section 16c via a transfer gate 16b to a vertical transfer path 16d.
Output to The vertical transfer path 16d transfers signal charges in accordance with the drive signal from the electrode section 16c to the horizontal transfer path 16e shown in FIG.
Send to The horizontal transfer path 16e supplies signal charges to the color signal processing unit according to the drive signal. If there is no difference in signal processing for each color in the color signal processing unit, the light receiving element 16a
Since there is no difference in the signal charges obtained in step (1), the obtained RGB signals have uniform color balance. For this reason, it is not necessary to amplify the obtained RGB signal according to the difference for each color as has been performed so far.
As a result, the color S / N generated to balance the color
It is possible to completely eliminate the possibility that the ratio will decrease.

In the above-described embodiment, the shape of the microlens 12 has been described as being defined by the curvature r. However, the shape is not limited to the curvature r. May be defined by the size of the cross-sectional area through which.

Next, another embodiment of the solid-state imaging device 10 will be described. Common parts are given the same reference numerals,
Description is omitted. In the present embodiment, the micro lens 12 is
Form the same size. Therefore, when the same amount of light is incident, the light intensity reaching the light receiving element 16a is increased as described above, despite the fact that the light beams having the same width are supplied to the respective light receiving elements 16a as shown in FIG. Depends on color. Therefore, a difference occurs in the signal charges obtained for each color. The size of the opening 17a of the light shielding member 17 is adjusted so that the same signal charge is generated even through the color filter 12 for each color of the light receiving element 16a. The size of the opening 17a is determined by the opening area A
Alternatively, it can be represented by the aperture ratio Ap.

The size of the opening 17a is the same as described above, since the sensitivity ratios S of the signals obtained for each RGB at the color temperature at which the photographing frequency is highest are 0.7, 1, 0.8, respectively. Contrary to the size (S (G)> S (B)> S (R)), the opening area (A (R)
> A (B)> A (G)). When the size of the microlenses 12 is made the same in this way, FIG.
FIG. 3 shows a cross section taken along the same breaking line AA as the imaging section 16 in FIG. In this cross section, the size of the opening area A cannot be directly shown, but when the length L of one side of the opening 17a is represented by L for each color, the length L is L (R)> L (B )> L (G)). By adjusting the size of the opening 17a in this manner, the micro lens
As in the case of forming by adjusting the curvature of 12, the photoelectric conversion is performed so as to eliminate the difference in the sensitivity ratio. When the same amount of light is uniformly irradiated as described above, the generated signal charges do not differ depending on the color, so that it is not necessary to electrically adjust the color balance by signal processing. Since the difference in color S / N, which has been a problem in the past, is eliminated, the image thus obtained can be provided as a well-balanced image.

In the above-described embodiment, the case where the color filter 14 and the light receiving element 16a are arranged in a corresponding square is described, but the present invention is not limited to this arrangement.
The present invention can also be applied to a so-called honeycomb arrangement in which the centers of the geometric shapes of the light receiving elements 16a are shifted by half the pitch in the row and column directions (see FIG. 4). As shown in FIG. 4, by adjusting the size of the microlens 12, the light receiving element 16a can be made into a high sensitivity light receiving element and a low sensitivity light receiving element. At this time, a high-sensitivity light-receiving element and a low-sensitivity light-receiving element are preferably arranged in consideration of a decrease in the amount of light due to the color filter 14 (not shown). Specifically, for example, a high-sensitivity light-receiving element may be disposed at a position corresponding to the colors R and B, and a low-sensitivity light-receiving element may be disposed at a position corresponding to the color G. Also in this honeycomb arrangement, the aperture ratio Ap of the light receiving element 16a may be changed according to the sensitivity for each color. The obtained signal charges are vertically transferred for the high-sensitivity light-receiving element and the low-sensitivity light-receiving element, respectively, so as not to disturb the arrangement of the light-receiving element 16a at the horizontal position of the high-sensitivity light-receiving element and the low-sensitivity light-receiving element. Read via 16L. By reading out the signal charges in this manner, an image pickup unit having a honeycomb arrangement is provided.
The image obtained from 16 can be provided as an image with good color balance.

With the above-described configuration, the variation of the sensitivity ratio which differs for each color is improved by adjusting the shape of the member disposed on the front surface of the light receiving element, and as a result, the color balance can be made uniform. Become like Since this uniform color balance is obtained by the shape of the members, the gain adjustment that has been performed in the most frequent color balance adjustment can be eliminated. Further, since the obtained signals are balanced in color, it is possible to eliminate variations in the color S / N ratio caused by gain adjustment for each color, and to provide a high-quality image. .

In each of the embodiments described above, the case where the three primary colors RGB are used in the primary color separation filters has been described. However, the present invention is not limited to the above-described embodiments. By making the shape of the light guide member different according to the different photoelectric efficiency of the light receiving element along with each color separation filter also in the color separation filters such as complementary colors, the electric signal level of each color actually obtained is made the same. The difference in color balance can be eliminated.

[0026]

As described above, according to the present invention, the shape of the light guide member is considered in accordance with the photoelectric conversion efficiency different for each color of the light receiving element caused by passing through each color separation filter in the color separation filter segment. Forming a light guide member,
By disposing this light guide member on the front surface of the light receiving element, the sensitivity balance ratio of each color can be made uniform, so that even if the gain is corrected, the correction result does not differ for each color. Each balance can provide the same signal. In addition, an image having a good color S / N ratio can be easily obtained without performing a complicated operation such as mounting a color conversion filter at the time of photographing.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an arrangement and a shape of a microlens applied to an imaging unit of a solid-state imaging device according to the present invention.

FIG. 2 is a plan view schematically showing the microlens when the imaging unit is viewed from above, focusing on the microlens of FIG. 1;

FIG. 3 is a cross-sectional view schematically illustrating the imaging unit when the imaging unit in FIG. 1 is cut along a break line AA.

FIG. 4 is a plan view schematically showing an arrangement relationship when the microlens of FIG. 1 is applied to an imaging unit having a honeycomb arrangement.

[Explanation of symbols]

 10 Solid-state imaging device 12 Micro lens 14 Color filter 16 Imaging unit 17 Light shielding member 18 Transparent member 20 Lens member 16a Light receiving element 16b Transfer gate 16c Electrode unit 16d Vertical transfer path

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5C024 AA01 DA01 EA04 EA08 FA01 GA11 GA31 5C065 AA01 AA03 BB01 CC01 DD01 EE05 EE06 EE11

Claims (6)

[Claims] 1. An image pickup means in which a plurality of light receiving elements for generating an electric signal according to incident light are two-dimensionally arranged, and a color arranged in accordance with a separation color corresponding to each of the plurality of light receiving elements. Each of the color filter segments has a separation filter segment, and each of the color filter segments separates incident light from the object field into incident light of any one of the separated colors and makes the light incident on each of the plurality of light receiving elements. A solid-state imaging device comprising: a color separation filter; and a light guide member disposed on the side of the incident light of the light receiving element and having a shape according to each photoelectric conversion efficiency of the separated color of the light receiving element. . 2. The apparatus according to claim 1, wherein the light guide member has a shape that maximizes the amount of the incident light in the separated color having the lowest sensitivity of the light receiving element, and has a sensitivity of each of the other separated colors. A solid-state imaging device having a shape in which the irradiation amount of the incident light decreases as the height increases. 3. The device according to claim 1, wherein the light guide member is a light condensing unit that condenses the incident light on the side of the incident light of the color separation filter corresponding to the light receiving element. A solid-state imaging device comprising: a light-collecting unit that is formed in accordance with the sensitivity of each light-receiving element to incident light of the separated color. 4. The device according to claim 1, wherein the light guide member uses a light shielding member that shields the imaging unit and opens only in a light receiving region of the light receiving element. A solid-state imaging device wherein the aperture ratio of the light receiving region in the separated color having the lowest sensitivity of the element is maximized, and the aperture ratio is reduced as the sensitivity of each of the other separated colors increases. 5. The apparatus according to claim 3, wherein the shape of the light-collecting means is defined by a curvature of a light-collecting surface of the light-collecting means or a size of an incident cross-sectional area passing through the light-collecting means. A solid-state imaging device characterized by the above-mentioned. 6. The apparatus according to claim 1, wherein the light receiving elements are arranged such that the centers of the geometric shapes of the light receiving elements are shifted by half a pitch in a row direction and a column direction. Solid-state imaging device.