JPH0113786B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field to which the invention pertains] The present invention relates to a solid-state imaging device that is a solid-state image sensor consisting of a plurality of elements and that obtains high resolution by equivalently increasing the number of elements. In particular, it relates to a solid-state imaging device suitable for radiometers and the like mounted on artificial satellites.

[Description of prior art]

In an imaging device using a solid-state image sensor composed of a plurality of elements, when the imaging range is fixed, the number of elements per image sensor must be increased in order to improve resolution. Currently, one-dimensional line sensors that use CCDs (charge transfer devices) as elements have 2048 elements, and two-dimensional area sensors have up to 500 x 500 elements. In visible and near-infrared radiometers for remote sensing using large-screen facsimiles or satellites, image sensors with a larger number of elements are desired in order to improve resolution.

On the other hand, as a technique for improving resolution without increasing the actual number of elements, a technique for equivalently increasing the number of elements is known. This includes a method of arranging and combining sensor element chips, and a method of optical synthesis. As for the former method of arranging and combining sensor element chips, there is a simple method of arranging image sensor chips in series, but this method causes bit loss between the chips and requires a large imaging area for the optical system. There are drawbacks. To eliminate this drawback, it is necessary to take measures such as using a large number of optical fibers.

This conventional method is shown in FIG. 1, in which the arrays of elements are different from each other by 1/2 pixel to create a one-dimensional solid-state image sensor of a multi-array type consisting of one set of two rows. In other words, line sensors 2 and 3 are placed on the same silicon wafer 1 with a width of 1/2 pixel different.
Making a chip image sensor. The photoelectric conversion output from one array is delayed by a memory, and this is superimposed on the photoelectric conversion output from the other array to obtain a series of conversion outputs in time series.

However, this method requires a complicated manufacturing process in order to manufacture an image sensor with a modified arrangement. In addition, the manufacturing process for two-dimensional area sensors becomes more complicated, making it impossible to obtain a practical product at a practical price. It is also possible to use two individual image sensors and arrange them with a difference of 1/2 pixel, but since the width of one pixel is about 14 μm,
Accurate alignment is quite difficult.

Among the above-mentioned methods, as an optical synthesis method, as shown in FIG. 2, there is a method in which a plurality of optical systems 4 are provided and synthesis is performed using a multi-lens. Imaged object 5
The incident light of each optical system corresponding to each part is photoelectrically converted by the solid-state image sensor 6 of each system, and each conversion output is obtained by an amplifier circuit 7, a delay circuit 8, and a synthesis circuit 9. Although this method is practical because it can use currently used solid-state image sensors, it is complicated because it requires optical systems corresponding to the number of images to be combined, that is, the number of optical systems corresponding to the improvement in resolution. Particularly in satellite-mounted radiometers, this increases the weight and space occupied by the optical system, which is a fatal drawback.

[Purpose of the invention]

An object of the present invention is to solve the drawbacks of these conventional structures and provide a lightweight, high-resolution imaging device using a conventional solid-state image sensor as is.

[Features of the present invention]

The present invention provides a high-resolution solid-state imaging device that realizes an equivalent multi-element solid-state image sensor by adding a simple light-shielding structure and its operation control means.

That is, the present invention is characterized in that a mask that partially transmits light is placed over each element constituting one pixel, and the light-transmitting portion of this mask is changed periodically to improve resolution.

The present invention provides photoelectric conversion means including a plurality of solid-state elements arranged at predetermined intervals, optical means for guiding incident light from an object to be imaged to the surface of the solid-state image sensor, and Each one of these is placed
It is configured to partially transmit the incident light for each solid-state image sensor constituting each pixel, and to change the position of the portion that transmits the incident light on each of the solid-state image sensors at a plurality of positions. a light shielding means; a position control means for controlling the change of the portion of the means through which incident light is transmitted simultaneously and periodically for each of the solid-state image sensors; The apparatus is characterized by comprising a signal processing means for processing the output.

[Explanation based on examples]

FIG. 3 is a diagram showing an example of a mask used as a light shielding means in the apparatus according to the embodiment of the present invention. This is a mask for a two-dimensional area sensor, with 1 pixel or 1
This is to divide each element into four parts for use. The grid 10 corresponding to one pixel is divided into four parts, and an opening 11 through which light passes is provided in one grid in an area corresponding to 1/4 of the divided pixels, and a shielding part is provided in the other 3/4 pixel area. 12. It is preferable that the aperture 11 be made somewhat smaller than the quadrant area, taking into consideration errors in the pixel size of the solid-state image sensor and edge effects. The entire grid has this configuration corresponding to each pixel.

How to operate this mask (A) parallel translation; (B) rotation; (C) Replacing masks with different patterns, (D) Switching of amorphous semiconductors, There are four ways.

The above (A) is a parallel movement horizontally and vertically by one divided pixel, as shown in Figure 4.
If on the sensor 1 pixel 13, the aperture 11 of the mask in FIG.
It comes to the position of pixel part b. At the next timing, it is moved to the third part c and then to the fourth part d, completing the imaging of one scene. In this case, the third
The mask shown in the figure requires extra light shielding portions 15 each having a width of 1/2 pixel or more on the vertical and horizontal edges.

As shown in FIG. 5, the mechanical operation for this parallel movement is performed by attaching the shielding mask 18 to a fixture 19, and using a support rod 20 connected to this fixture 19 and a cam 17 rotating around a rotation shaft 21. This is done using a mechanism.

The method (B) using rotation is effective for a two-dimensional sensor in which the number of pixels and pixel width are symmetrical in the vertical and horizontal directions, and FIG. 6 is a diagram of an area sensor for explaining this method. The opening 11 of the mask shown in FIG. 3 is initially located at the 1/4 bit portion e of the sensor pixel 13 (0° phase). When the mask is rotated 90 degrees clockwise about the position of the mask that coincides with the center 22 of the sensor, the mask opening 11 will be located at the 1/4 pixel portion f of the sensor. At the next 90° rotation (180° phase), the next 1/4 pixel portion g is located, and at the subsequent 90° rotation (270° phase), it is at the 1/4 pixel portion h. Imaging is performed at each position to complete one scene.

The above (C) mask replacement method uses four types of masks whose mask openings are located at 1/4 pixel portions a, b, c, and d above the sensor 1 pixel 13 shown in FIG. This is a method that replaces the following one after another.

The above method (D) by switching an amorphous semiconductor mask is a method in which an amorphous semiconductor element is used as a mask instead of using the above-described mask provided with an opening. As shown in FIG. 7, this amorphous semiconductor element exhibits a switching characteristic in which the light transmittance reaches a threshold voltage Th with respect to a control voltage. As shown in FIG. 8, such elements are divided into quarter pixels and arranged in a grid pattern corresponding to the image sensor. Each grid 10
Lead wires 32 are taken out from each of the 1/4 bit portions 31, connected in parallel, and a control voltage is applied to them. This control voltage performs switching between light transmission and shielding of each 1/4 pixel portion 31.

In each of the four methods shown in (A) to (D) above, the number of divisions of the mask grid corresponding to one pixel of the area sensor was explained as four divisions, but this means that the number of divisions n can be set to any resolution. It is possible to increase the amount.

FIG. 9 is a block diagram of a device according to an embodiment of the present invention. The incident light guided through the optical system 4 is guided to the solid-state image sensor 6 by the light shielding mask 18, so that only the incident light corresponding to 1/n pixels×total number of pixels is guided to the solid-state image sensor 6. The light shielding mask 18 is connected to the control time signal generation circuit 3
According to the timing pulse by driver 3
4. The image sensor is a 500 x 500 pixel CCD area sensor with a light shielding mask of 18
divides one pixel into n parts. The one in which n is 4 is shown in FIG. The movement method is rotary.

The driver 34 operates according to the time signal (timing) shown in FIG. 10, and the light shielding mask 18 rotates at 0°, 90°, 180°, and 180° at timings _t1 , _t2 , _t3 , and _t4 , respectively.
Rotates 270°. At timing _t1 , incident light of 1/4 × (500 × 500) pixels enters the CCD sensor, is photoelectrically converted,
The output is scanned and output sequentially under the control of the time signal generation circuit 33, and is led to the subsequent signal processing circuit 39 through the amplifier 7. Next, mask 18
After rotating by 90 degrees, at timing _t2 , the incident light of the next 1/4×(500×500) pixels is converted and output. Similarly, at timings t ₃ and t ₄ , the phase advances by 180° and 270°, respectively, and the signals for one scene are arranged in time series and output. After signal processing such as AD conversion, if long-distance transmission is required, such as with a satellite-mounted radiometer,
The signal is transmitted by the transmitting circuit 42.

On the receiving side, the data passes through a receiving circuit 43 and is processed by a data processing circuit 45 using a timing signal similar to that on the transmitting side by a time control signal generating circuit 44 on the receiving side. The output signal of the data processing circuit 45 is converted into an image signal by an image signal conversion circuit 46, and an image is reproduced on a monitor television 47.

In the time series signal shown in FIG. 10, timing t ₁ ~
_t4 is the mask control timing, and each timing includes 500 x 500 bits of image information, resulting in a total of 4 x 500 x 500 bits of image information. On the receiving side, using a delay circuit included in the data processing circuit 45, the time-series signal (image information) is summarized into 2 x 500 bits corresponding to one horizontal line of the actual image, and is processed by scanning 2 x 500 vertical lines. , 1 Mbits for one scene (horizontal 2 x 500 bits, vertical 2 x 500 bits)
Synthetic playback of bits) is performed. To explain this in detail, the time-series signal is scanned in the following order on the receiving side. The first timing t ₁ of the time series in Figure 10
The first bit is sent alternately, then the first bit at timing _t2 , and the _second bit at timing t1, and up to the 500th bit at timing _t2 becomes the first horizontal line of the reproduced image. The first bit at timing _t4 is alternately followed by the first bit at timing _t3 ,
It becomes the second horizontal line up to the 500th bit at timing _t3 . Similarly, 1000 horizontal lines each consisting of 1000 bits are scanned one after another.

[Explanation of effects]

As explained above, according to the present invention, an image sensor can be manufactured without developing a new chip, by using a conventional sensor, and by complicating or modifying the optical system, increasing the weight and occupying space. By adding a simple light-shielding mask and its operation controller, the resolution can be increased to any desired degree without the need for it.

In particular, in applications such as radiometers mounted on geostationary satellites, which have plenty of imaging time and require high resolution, it is necessary to compensate for the decrease in the light-receiving area of each pixel, that is, the decrease in the utilization efficiency of the image sensor. In addition, the resolution can be improved by utilizing the optical integration time of the sensor without requiring high resolution in the optical system.

According to the present invention, a lightweight and high-resolution imaging device can be realized.

[Brief explanation of drawings]

Figure 1 is a structural diagram of a one-dimensional line sensor using the conventional 1/2-bit multiple array method. FIG. 2 is a block diagram of an imaging device using a conventional multi-lens composition method. FIG. 3 is a diagram showing an example of a light shielding mask according to an embodiment of the present invention. FIG. 4 is an explanatory diagram of parallel movement in the embodiment of the present invention. FIG. 5 is an example of an operation structure for performing the parallel movement. FIG. 6 is an explanatory diagram of rotational movement in the embodiment of the present invention. FIG. 7 is a characteristic diagram of an amorphous semiconductor used as a mask. FIG. 8 is a partial structural diagram of a mask made of an amorphous semiconductor according to an embodiment of the present invention. FIG. 9 is a circuit block diagram of a device according to an embodiment of the present invention. FIG. 10 is a diagram showing image signal timing. 1... Silicon wafer, 2, 3... Light receiving element, 4
...Optical system, 5. Imaged object, 6. Solid-state image sensor, 7. Amplifier, 8. Delay circuit, 9. Signal synthesis circuit, 10. Light shielding mask grating, 11. Light shielding mask opening, 12. Light shielding. Shielding part of the mask, 13...
Sensor 1 pixel, 17...Cam, 18...Light shielding mask, 19...Mask fixture, 20... Support rod, 21...
Axis, 22...Center of symmetrical sensor, 31...1/4 bit of amorphous semiconductor, 32...Lead wire, 33,
34... Time signal generation circuit, 34... Driver, 39
...signal processing circuit, 42...transmission circuit, 43...reception circuit, 45...data processing circuit, 46...image signal conversion circuit, 47...monitor television.

Claims (1)

[Scope of Claims] 1. A photoelectric conversion means including a plurality of solid-state image sensors arranged at predetermined intervals; an optical means for guiding incident light from an object to be imaged to the surface of the solid-state image sensor; and the above-mentioned solid-state image sensor. Each of the solid-state image sensors arranged on the surface of the element and constituting one pixel partially transmits the incident light, and the position of the part that transmits the incident light on each of the solid-state image sensors is set at a plurality of locations. a light shielding means configured to be able to change its position; a position control means for periodically controlling changes in a portion of the means through which incident light is transmitted for each of the solid-state image sensors; A high-resolution solid-state imaging device comprising: signal processing means for processing the output of each of the solid-state imaging devices according to control timing.