JPH07143411A - Solid-state image pickup element - Google Patents

Abstract

PURPOSE:To obtain a solid-state image pickup element in which no shading is in an output with an open aperture without increased production cost. CONSTITUTION:An area of a sensor opening section 12a located at the surrounding of a solid-state image pickup element 10 in which an on-chip micro lens 18 is provided on each light receiving sensor 12 is designed larger than the area of a sensor opening section 12a in the middle of the element. The luminous quantity incident from the surrounding light decreases when an aperture of an image pickup lens of the image pickup device provided with the element 10 is open because of the decreased surrounding light, but the sensitivity increased because the opening area of the sensor 12 is large so as to cancel the increase and the decrease with each other and a uniform video output is obtained outdoor and indoor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state image pickup device, and more particularly to a so-called on-chip microlens solid-state image pickup device in which a condenser lens is mounted on each pixel composed of a light receiving sensor.

[0002]

2. Description of the Related Art In recent years, "semiconductor" image pickup devices, so-called solid-state image pickup devices, have been widely used in image pickup devices such as video cameras. FIG. 8 shows a schematic configuration of a general image pickup apparatus, and a taking lens 80 is provided in front of the apparatus. The input light image that has entered the device through the taking lens 80 and the optical filter 82 is converted into an electric signal by the solid-state image pickup device 10, and the signal processing circuit 84 is provided.
Is output to the outside as a video signal. In the figure, 86 is a clock driver for driving the solid-state image sensor 10, 88 is a timing generation circuit, and 90 is a synchronization signal generation circuit.

FIG. 9 shows a plan view of a conventional solid-state image pickup device 20 with an on-chip microlens, and FIG. 10 shows a cross section thereof. The solid-state imaging device 20 includes a large number of light receiving sensors 22 (hereinafter, referred to as sensors) including photodiodes.
And a vertical shift register 24 and a horizontal shift register 26 for taking out the electric charges of the respective sensors 22 in order, and for further concentrating the light from the outside above the respective sensors 22 to guide them to the respective sensors 22. A convex condenser lens (on-chip microlens) 28 is provided.
Further, generally, the opening areas of the sensor openings 22a formed on the element surface 20a of the solid-state imaging element 20 are formed so as to be equal over the entire area of the element.

[0004]

By the way, in the taking lens 80 as shown in FIG. 8, when the aperture of the lens is set to the open side, the aperture efficiency is lowered and the amount of light in the peripheral portion with respect to the central portion of the lens is reduced. Is reduced and so-called peripheral dimming occurs. In a camera or the like using the conventional solid-state image sensor 20 as described above, when the diaphragm of the taking lens 80 is opened, a shading phenomenon occurs in which the four corners of the screen are dark.

To solve this problem, Japanese Patent Laid-Open No. 63-1
Japanese Patent No. 47365 discloses a solid-state imaging device in which a condenser lens having a different refractive index or diopter (lens strength) depending on the position of a pixel is arranged to reduce variations in the amount of incident light over the entire area. . However, this device has a problem in that it is difficult to mold the lens and the manufacturing cost is high because a large number of condenser lenses having different curvatures are integrally covered over the entire element portion.

In view of the above circumstances, it is an object of the present invention to provide a solid-state image pickup device which is easy to manufacture and can suppress the shading phenomenon.

[0007]

In order to achieve the above object, according to the present invention, in a solid-state image pickup device in which an on-chip microlens is provided on a light-receiving sensor which constitutes a pixel, a position is provided in the peripheral portion of the solid-state image pickup device. There is provided a solid-state imaging device, wherein the opening area of the light-receiving sensor is larger than the opening area of the light-receiving sensor located at the center of the solid-state imaging device.

[0008]

It is possible to increase the light receiving sensitivity by the amount that the opening area of the light receiving sensor in the peripheral portion of the solid-state image sensor is larger than the opening area of the light receiving sensor located in the central portion. As a result, even if the amount of incident light on the peripheral part of the shooting lens decreases with the decrease in aperture efficiency when the shooting lens is open, it is offset by the increase in the photosensitivity, and there is a difference between the central part and the peripheral part as a whole. There is no light reception.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A solid-state image sensor according to the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view of a solid-state image pickup device according to the present invention. The left side shows the element appearance of the central portion in the chip horizontal direction (arrow A direction), and the right side shows the element appearance of the peripheral portion in the horizontal direction. . In the figure, 10 is a solid-state image sensor (chip), 12 is a sensor which is composed of a photodiode and each is a pixel, 14 is a vertical shift register for taking out electric charges of the sensor 12 in order, and 16 is a horizontal shift register.

FIG. 2 is a sectional view of the element taken along the line BB of FIG. As shown in this figure, a convex on-chip microlens (pixel lens) 18 for concentrating the light from the outside and guiding it to each sensor 12 is provided above each sensor 12.

The solid-state image pickup device 10 constructed as described above.
According to the present embodiment, the opening 12a of the sensor 12 formed on the surface 10a of the element portion has a square shape in the central portion, while the peripheral portion has a rectangular shape, and the opening area is central. The peripheral part is set to be larger than the part. Further, the curvatures of the on-chip microlenses 18 provided corresponding to the respective sensors 12 are all the same and are formed to have the same lens characteristics (refractive index, diopter, etc.).

Solid-state image pickup device 10 formed as described above
The action of will be explained.

FIG. 3 (a) shows the focusing form of the on-chip microlens 18 when the F-number of the lens of the taking lens 80 (FIG. 8) is increased and the so-called diaphragm is narrowed. ) Shows a conventional solid-state imaging device as a comparative example. It should be noted that in the conventional element shown in the figure, the opening area of the sensor is set to be equal in both the central portion and the peripheral portion, and P and P ′ are taken through the taking lens 80 and the optical filter 82 (FIG. 8). The light rays are incident on the sensors 12 and 12 '.

In the state in which the diaphragm is narrowed in this way, there is no dimming of the periphery of the taking lens 80, and almost the same amount of light is obtained in the central portion and the peripheral portion of the lens. Further, the trajectories of the light rays P and P ′ toward the on-chip microlenses 18 and 18 ′ become substantially parallel due to the increase in aperture efficiency.

In this state, the light rays P and P'which are incident on the on-chip microlenses 18 and 18 'are similarly converged by the uniformed lens characteristics over the entire element, and the sensors 12 and 12' are almost completely converged. It is collected inside. Therefore,
Whether in the case of the conventional element or the element of this embodiment,
There is no difference in the sensor light condensing degree between the central portion and the peripheral portion of the chip, and as a result, it is possible to obtain the same sensitivity inside and outside. On the other hand, the amount of light passing through the central portion and the peripheral portion of the taking lens becomes almost the same as the F value increases, so that the video signal externally output via the signal processing circuit 84 (FIG. 8) of the camera. As shown in FIG. 4, even in the case of (a) the device of this embodiment and (b) the conventional device, uniform output waveforms can be obtained inside and outside.

5 (a) and 5 (b), when the F value of the lens of the taking lens 80 is reduced and the diaphragm is opened,
The condensing form of the on-chip microlens 18 in the device of this embodiment and the conventional device is shown.

As shown in the figure, when the diaphragm is open, the trajectories of the light rays P and P'toward the on-chip microlenses 18 and 18 'are not parallel, and as a whole, they are conical from the taking lens 80. It is a collection of light rays that diffusely emit. Therefore, in this state, the light is incident on the on-chip microlenses 18 and 18 'in an inclined state with respect to the vertical line from the element surface, and it is difficult to completely collect the light in the sensors 12 and 12'. Therefore, in the case of the conventional element shown in (b), there is no difference in the amount of light received by the sensor 12 'between the central portion and the peripheral portion of the chip, and as a result, the same sensitivity is obtained inside and outside. On the other hand, in the case of the element of this embodiment shown in (a), the peripheral area sensor is formed to have a larger opening area than the central area sensor. The amount increases and the sensitivity increases.

Here, since the photographic lens 80 is in the aperture open state as described above, the amount of light passing through the peripheral portion of the lens becomes smaller than that at the central portion due to the reduction of the aperture efficiency, and compared with the central portion. The periphery becomes dark, so-called peripheral dimming. However, in the case of the solid-state image sensor of the present embodiment, since the sensor sensitivity of the peripheral portion of the chip is high as described above, the peripheral dimming of the photographing lens is canceled and the signal processing circuit 84 of the camera is canceled. The video signal externally output via the output signal has a uniform output waveform inside and outside as shown in FIG.

On the other hand, in the case of the conventional element, since there is no difference between the sensor sensitivity of the peripheral portion and the sensor sensitivity of the central portion, it is affected by peripheral dimming, and the external output is as shown in FIG.
As in (b), the shading state occurs in which the output level from the peripheral sensor decreases.

As described above, according to this embodiment, since the sensor opening area in the peripheral portion is larger than that in the sensor in the central portion, a uniform video signal output without shading can be obtained regardless of the aperture of the taking lens. . Further, all the on-chip microlenses forming the solid-state imaging device of the present embodiment are formed in the same shape, and the above-described effects can be obtained by simply changing the aperture area of the sensor, so that compared with the conventional device. The cost does not increase.

Although the present invention has been described by taking the example of the solid-state image pickup device in which the sensor opening areas are different between the peripheral portion and the central portion of the chip, as another embodiment, each pattern of FIG. As shown in (a) and (b), the sensor opening area may be gradually increased from the central portion to the peripheral portion thereof, or may be gradually increased for every predetermined number of pixels. In the illustrated embodiment, the sensor opening area is different between the element peripheral portion and the element central portion in the chip horizontal direction, but as shown in the pattern (c), the chip vertical direction is shown. There may be a difference in the sensor opening area between the peripheral part and the central part in
The present invention may be applied in both directions as in the pattern (d).

The solid-state image sensor according to the present embodiment is effective in suppressing shading when the aperture of a normal photographing lens is opened as described above, but is also effective for a photographing lens having a short exit pupil distance. However, there is a problem that the signal output of the peripheral portion is reduced due to the reduction of the angle of the light beam incident on the peripheral portion of the chip, and by applying the present invention to this problem as well, shading can be reduced.

[0024]

As described above, according to the present invention, the aperture area of the light receiving sensor located in the peripheral portion of the solid-state image sensor is made larger than the aperture area of the sensor located in the central portion of the solid-state image sensor. By increasing the sensitivity, it is possible to obtain an image output without shading without being affected by peripheral dimming even when the aperture of the taking lens is opened, and without increasing the manufacturing cost.

[Brief description of drawings]

FIG. 1 is a plan view of a solid-state image sensor according to an embodiment of the present invention.

FIG. 2 is a device cross-sectional view taken along the line BB of FIG.

3A and 3B are views showing a light collecting state in the element when the diaphragm of the taking lens is narrowed, FIG. 3A is a cross-sectional view of the element of the present example, and FIG.

FIG. 4 is a diagram showing a video signal output waveform corresponding to FIG.

5A and 5B are views showing a light collecting state in the element when the diaphragm of the taking lens is opened, FIG. 5A is a cross-sectional view of the element of this example, and FIG.

6 is a diagram showing a video signal output waveform corresponding to FIG.

FIG. 7 is a diagram showing an opening pattern as an embodiment different from FIG.

FIG. 8 is a block diagram showing a configuration of a solid-state imaging device.

FIG. 9 is a plan view of a conventional solid-state image sensor.

FIG. 10 is an element cross-sectional view taken along the line BB of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Solid-state image sensor (chip) 12 ... Light receiving sensor 12a ... Opening 14 ... Vertical shift register 16 ... Horizontal shift register 18 ... On-chip microlens (pixel lens) 80 ... Photographing lens

Claims (5)

[Claims] 1. In a solid-state image sensor having an on-chip microlens provided on a light-receiving sensor that constitutes a pixel, the aperture area of the light-receiving sensor located in the peripheral part of the solid-state image sensor is located in the central part of the solid-state image sensor. The solid-state imaging device is characterized in that it has a larger opening area than the sensor. 2. The solid-state image sensor according to claim 1, wherein an opening area of the light-receiving sensor gradually increases from a central portion of the solid-state image sensor to a peripheral portion thereof. 3. The solid-state image sensor according to claim 1, wherein the aperture area of the light-receiving sensor is increased stepwise for each predetermined number of pixels from the central part of the solid-state image sensor to its peripheral part. . 4. The solid-state image sensor according to claim 2, wherein the central part and the peripheral part respectively correspond to the central part and the peripheral part in the horizontal direction of the solid-state image sensor. 5. The solid-state imaging device according to claim 2, wherein the central part and the peripheral part correspond to the central part and the peripheral part in the vertical direction of the solid-state imaging device, respectively.