JPH05259422A - Solid-state image sensor - Google Patents

Abstract

PURPOSE:To improve sensitivity characteristics of a solid-state image sensor. CONSTITUTION:Upon application of a voltage between a transparent polymer layer 4 and a transparent electrode layer 5, a thin film 4a of the transparent polymer layer 4 is attracted by the electrostatic force produced in an electrode 5a of the transparent electrode layer 5 and thereby the thin film 4a is bent to exhibit convex lens function for converging incident light onto a light receiving part 2. Consequently, sensitivity of CCD can be enhanced for weak incident light and the sensitivity can appropriately be controlled according to the amount of light by controlling the applying voltage variably.

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 used in electronic cameras and the like.

[0002]

2. Description of the Related Art Conventionally, a CCD image sensor using a charge-coupled device such as a CCD has been widely used as a solid-state image pickup device used in an electronic camera or the like. However, the sensitivity is increased when the amount of light is small. In this case, when the light amount is large, blooming, smear, etc. are likely to occur, and the dynamic range for the light amount cannot be increased. Further, since the light receiving area of the light receiving portion is determined at the manufacturing stage, the dynamic range cannot be changed as it is.

Therefore, a sensitivity control electrode is provided on a part of the surface of the light-receiving portion, and when the incident light amount level is small, the photoelectric conversion operation is performed with the sensitivity of the image pickup device, and when the incident light amount level is large, the sensitivity control is performed. It has been proposed that a negative voltage is applied to the working electrode to deplete the lower light-receiving portion, thereby substantially reducing the light-receiving area and thereby changing the dynamic range (Japanese Patent Laid-Open No. Sho 64).
-69050).

Further, when photoelectric conversion elements having different light receiving areas are arranged in parallel and the incident light quantity level is small, the signal obtained by the photoelectric conversion element having a large light receiving area is read, and when the incident light quantity level is large, the signal is large. A device in which the dynamic range is changed by reading a signal obtained by a photoelectric conversion element having a light receiving area (Japanese Patent Laid-Open No. 1-31406).
No. 6, gazette) is also proposed.

There is also a microlens called an on-chip microlens that is fixed above each light-receiving section to focus the incident light to enhance the sensitivity.

[0006]

However, in the first conventional example, it is necessary to change the design of the internal structure of the solid-state image sensor (CCD) in order to variably control the dynamic range, and the structure becomes complicated and the cost increases. There is a problem that it is easy, and it is difficult to sufficiently enhance the linearity of the sensitivity by controlling the applied voltage of the sensitivity control electrode arranged in a part of the light receiving portion.

Further, in the case where the light receiving area is changed in two steps as in the second conventional example, the sensitivity can only be switched in two steps, and only one signal of the light receiving sections having different light receiving areas is used. Since it can only be read, the light receiving area per unit area is substantially reduced, and the sensitivity of the solid-state imaging device is reduced. Further, in the third conventional example, unlike the above conventional example, the sensitivity can be increased with respect to the inherent sensitivity of the photoelectric conversion element, but the dynamic range cannot be changed.

The present invention has been made in view of such conventional problems, and variably controls the density of the light incident on the light receiving portion to dynamically change the sensitivity in accordance with the light amount. An object of the present invention is to provide a solid-state imaging device that solves the above problems as a range changing structure.

[0009]

Therefore, in the solid-state image pickup device according to the present invention, a resin having a light-transmitting property which is deformable by electrostatic force is formed on each light-receiving surface of the solid-state image pickup device having a plurality of photoelectric conversion elements. A layer and a translucent electrode layer including an electrode that generates an electrostatic force by applying a voltage between the resin layer and attracts the resin layer to deform it into a lens shape. The amount of light that passes through the resin layer and the electrode layer that deforms according to the applied voltage and enters the light receiving portion is variably controlled.

For example, the electrode layer, the resin layer, and the light receiving portion are
The resin layers may be laminated in this order, and the resin layer that is deformed by the applied voltage may have a function of a convex lens that focuses incident light on the light receiving portion side. Alternatively, the resin layer, the electrode layer, and the light receiving portion may be arranged in this order, and the resin layer that is deformed by the applied voltage may have a function of a concave lens that diffuses incident light to the light receiving portion side.

[0011]

In the case where the electrode layer, the resin layer and the light receiving portion are laminated in this order, when a voltage is applied between the resin layer and the electrode layer, the resin layer is attracted by the electrode and curved so as to be convex toward the incident light side. Therefore, the incident light is refracted in the direction in which the light is converged on the light receiving portion, and the function of the convex lens is achieved. As a result, the density of light incident on the light receiving section increases, and the sensitivity increases.

That is, the sensitivity is variably controlled in the direction of increasing the sensitivity by increasing the applied voltage. In addition, resin layer, electrode layer,
In the case where the light receiving portions are arranged in this order, when a voltage is applied between the resin layer and the electrode layer, the resin layer is attracted by the electrodes and curved so as to be concave toward the incident light side. It acts as a concave lens by refracting in the direction of diffusion.
As a result, the density of light incident on the light receiving portion is reduced, and thus the sensitivity is reduced.

That is, by increasing the voltage applied to the electrodes,
It is variably controlled to decrease the sensitivity.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on illustrated embodiments. In FIG. 1 showing a first embodiment, a FIT / IT type CCD, which is a substrate of a solid-state image pickup device according to the present invention, includes a light-shielding portion 1 in which a layer of light-shielding Al, poly-Si or the like is interposed and a photoelectric conversion element Photo detectors and the like) and light-receiving portions 2 are alternately arranged in the column direction.
(Green) filter layer 3a, R (red) filter layer 3
b, B (blue) filter layers 3c are provided alternately with each other in the column direction.

A mechanism for variably controlling the amount of light incident on the light receiving portion 2 is provided on the surface of the FIT / IT type CCD.
That is, the transparent polymer layer 4 formed of a resin layer having a light-transmitting property is fixed on the upper side of the color filter layer 3.
A portion of the transparent polymer layer 4 facing the light receiving portion 2 is formed into a thin film 4a that is easily deformable, and a portion of the glass substrate facing the thin film 4a is formed as a recess on the upper side of the thin film 4a. The transparent electrode layer 5 formed by attaching the electrode 5a is fixed. The transparent polymer layer 4 and the electrode 5a
A voltage control circuit 6 whose output voltage is variably controlled is connected between and, and when a voltage is applied from the voltage control circuit 6, an electrostatic force having a strength corresponding to the magnitude of the applied voltage is generated. The thin film 4 of the transparent polymer layer 4 which is generated and has a strength corresponding to the electrostatic force
a is attracted to the electrode 5a side and is curved.

Next, the operation of the solid-state image pickup device having such a configuration will be described. Under an imaging condition where the amount of incident light is small, the output voltage of the voltage control circuit 6 is largely controlled. This allows
A strong electrostatic force is generated in the electrode 5a, and the thin film 4a is attracted with a strong force as shown in FIG. 2 to largely bend in the direction of the electrode 5a. In this state, when the incident light passes through the electrode 5a of the transparent electrode layer 5 and the thin film 4a of the transparent polymer layer 4, it is refracted by the convex lens action of the curved thin film 4a so as to be focused toward the light receiving portion 2.

Therefore, the light receiving section 2 receives the light having a high density by converging the incident light rays, and as a result, the sensitivity can be sufficiently improved even under the condition that the amount of the incident light is small. For example, when light that travels straight in a state where no voltage is applied is incident on the light receiving unit 2, several 10% of the total light that is proportional to the aperture ratio is incident, and the CCD sensitivity in this state is 1 ISO sensitivity.
If the voltage is applied and the light receiving unit 2 receives a double amount of light, the ISO sensitivity doubles to 200.

Under the image pickup condition in which the amount of incident light is large, the output voltage of the voltage control circuit 6 is controlled to be low or zero. When the output voltage is controlled to be small, the electrode 5
Since the electrostatic force generated on a is small and the curvature of the thin film 4a is small, the focusing rate to the light receiving unit 2 is small, and the sensitivity is reduced as compared with the case where the amount of incident light is small. In the state where the output is controlled to zero, no electrostatic force is generated on the electrode 5a,
Since the thin film 4a is not curved as shown in FIG. 1, the incident light passes straight through the thin film 4a, and the sensitivity becomes the minimum sensitivity peculiar to the light receiving section 2.

If the amount of light received by the light receiving portion 2 in the example similar to the above embodiment is 1/2 compared with the case where the applied voltage is zero, the ISO sensitivity becomes 50 which is 1/2. ..
In this way, by controlling the density of the light incident on the light receiving portion in the increasing direction, the dynamic range can be changed by controlling in the direction of increasing the sensitivity of the photoelectric conversion element. The sensitivity can be controlled, and in particular, a high sensitivity can be ensured and a good image can be obtained even under the condition that the amount of incident light is small.

Further, as compared with the structure in which the structure on the solid-state image sensor (CCD) side is changed to change the sensitivity, it is easier to obtain a highly accurate linear control characteristic, and the solid-state image sensor needs to be redesigned. Since there is no need to change only the part fixed to the surface, there is a great cost advantage in manufacturing. FIG. 3 shows a solid-state imaging device according to the second embodiment of the present invention. In this case, contrary to the above embodiment, the light receiving section 2
A transparent electrode layer 5 is provided immediately above the transparent polymer layer 4, and a transparent polymer layer 4 is provided thereon in an overlapping manner. More specifically, the layer obtained by polymerizing the transparent polymer layer 4 and the transparent electrode layer 5 in the above example is fixed to the color filter layer 3 as it is upside down. Other configurations are the same as those in the above-mentioned embodiment, and the same reference numerals are given.

Next, the operation of the solid-state image pickup device having such a configuration will be described. The output voltage of the voltage control circuit 6 is largely controlled under the imaging condition where the amount of incident light is large. As a result, as shown in FIG. 4, the thin film 4a is attracted to the electrode 5a side by a strong force and curved, and in this state, the incident light transmits the transparent electrode layer 5a.
When passing through the electrode 5a of the transparent polymer layer 4 and the thin film 4a of the transparent polymer layer 4, the curved thin film 4a refracts so as to diffuse to the light receiving portion 2 due to the concave lens action.

Therefore, the light receiving section 2 receives the light of which the incident light rays are diffused to reduce the density, and as a result, the sensitivity can be lowered even under the condition that the incident light amount is large. Further, under the image pickup condition where the amount of incident light is small, the output voltage of the voltage control circuit 6 is controlled to be low or zero. When the output voltage is controlled to be small, the curvature of the thin film 4a is small, so that the focusing rate to the light receiving unit 2 is small and the sensitivity is increased as compared with the case where the amount of incident light is large. In particular,
In the state where the output is controlled to zero, the incident light goes straight through the thin film 4a, and the sensitivity becomes the maximum sensitivity peculiar to the light receiving unit 2.

As described above, by controlling the density of the light incident on the light receiving portion in the decreasing direction, the sensitivity of the photoelectric conversion element can be controlled in the decreasing direction to change the dynamic range. Can be controlled to an appropriate sensitivity. Further, in the first and second embodiments, the layer obtained by polymerizing the transparent polymer layer 4 and the transparent electrode layer 5 only needs to be turned upside down and replaced. Therefore, such a polymerized layer is prepared. In this case, it is sufficient to change the fixed surface according to the desired direction of changing the sensitivity, so that the manufacturing cost is great.

[0024]

As described above, according to the present invention, the amount of light received by the light receiving portion can be variably controlled by controlling the applied voltage, so that a wide range from weak incident light to strong incident light can be obtained. Photoelectric conversion over a range is possible,
The dynamic range can be changed so as to obtain an appropriate sensitivity according to the amount of light, and the structure is simple, the reliability is excellent, and the cost merit is large.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration of a solid-state imaging device according to a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view of an essential part showing the operation of the above embodiment.

FIG. 3 is a sectional view showing a configuration of a solid-state image pickup device according to a second embodiment of the present invention.

FIG. 4 is an enlarged sectional view of an essential part showing the operation of the above embodiment.

[Explanation of symbols]

 2 light receiving part 4 transparent polymer layer 4a thin film 5 transparent electrode layer 5a electrode 6 voltage control circuit

Claims (3)

[Claims] 1. A light-transmitting resin layer which is deformable by electrostatic force and a voltage is applied between the resin layers on the surface of each light-receiving portion of a solid-state image pickup device having a plurality of photoelectric conversion elements. An electrode layer having a light-transmitting property, which includes an electrode for generating an electrostatic force to attract the resin layer and deform it into a lens shape, is disposed so as to overlap the resin layer and the electrode layer that deform according to the applied voltage. A solid-state imaging device having a structure for variably controlling the amount of light that passes through and is incident on the light receiving unit. 2. The electrode layer, the resin layer, and the light receiving portion are laminated in this order, and the resin layer which is deformed by the applied voltage has a function of a convex lens for focusing incident light to the light receiving portion side. The solid-state imaging device according to claim 1. 3. The resin layer, the electrode layer, and the light receiving portion are arranged in this order, and the resin layer which is deformed by the applied voltage has a function of a concave lens for diffusing incident light to the light receiving portion side. The solid-state imaging device according to claim 1.