JPH08181906A - Image pickup device - Google Patents

Abstract

PURPOSE: To obtain an image pickup device picking up a video image with less noise and high quality. CONSTITUTION: When a luminance level detection circuit 9 detects that a signal level of a video signal subject to photoelectric conversion by a CCD 4 is lower than a prescribed level, a gate circuit 11 is set through and the video signal once stored in a memory 8 is added to a video signal received thereafter by an adder 7 till a prescribed level is obtained. The processing above is applied to each video signal obtained by changing an image forming position on a light receiving face of the CCD 4 by a VAP 1 and the results are composited by a signal processing circuit 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup device for picking up an image of a subject.

[0002]

2. Description of the Related Art At present, an image pickup device for printing or a computer using a solid-state image pickup device such as a CCD arranged two-dimensionally has a shortage of total pixels as compared with a one-dimensional pixel arrangement such as a scanner. However, there is a problem that the resolution of the obtained image is low and a high quality output image cannot be obtained. To solve such a problem, by synthesizing images of four frames, which are obtained by shifting the image forming position of the optical image formed on the light receiving surface of the solid-state image pickup device in units of 1/2 pixel vertically and horizontally, for example, Attempts have been made to reconstruct a high definition image with four times the number of pixels.

For example, a method of displacing a CCD horizontally and vertically by using a piezoelectric element described in JP-A-64-69160, and between an image pickup lens system and a CCD described in JP-A-63-284979. A method of improving apparent resolution by a method using the provided optical optical path displacing means is disclosed. In addition, JP-A-4-3114
In 48, Vari-Angle-Prism (VA
P) is used.

However, the signal processing method of such an image pickup apparatus is the same as the conventional one except for the portion for combining images as described above. That is, the dynamic range of brightness change in the natural world has a width of up to 100,000 lux, while the range of brightness change that can be reproduced by a solid-state image sensor such as a CCD is limited.

Therefore, in a conventional video camera or the like, a diaphragm mounted in front of the solid-state image pickup device adjusts the amount of light emitted to the solid-state image pickup device. Further, when the amount of incident light is not sufficient and the output signal level of the solid-state image sensor does not reach a predetermined value even when the diaphragm is fully opened, it is amplified by an automatic gain control (AGC) circuit.

[0006]

However, in the above conventional example, when the illuminance of the subject is insufficient, the AG
When a large gain is added to the output of the solid-state image sensor due to C,
Along with this, the noise component was also amplified and the S / N was lowered. Therefore, there is a problem that the result of combining the images also leads to the deterioration of the image quality.

In order to solve this problem, a method that has been often used in the past is to slow down the read speed of the solid-state image pickup device so that the solid-state image pickup device can store sufficient electric charge even in low illuminance. Since the noise generated in the solid-state image sensor of No. 2 increases as the amount of stored charge increases,
The effect of improving S / N was not obtained so much.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and in an image pickup device, a photoelectric conversion means for photoelectrically converting an optical image into a video signal and the photoelectric conversion means are provided. An image forming optical system for forming an optical image, image forming position changing means for changing the image forming position of the optical image on the photoelectric converting means by the image forming optical system, and a video signal output from the photoelectric converting means. Integrating means for integrating over time,
The detecting means for detecting the signal level of the video signal integrated by the integrating means, and the photoelectric conversion means when the image forming position changing means changes the image forming position of the optical image on the photoelectric converting means to a predetermined position. Storage means for storing a plurality of video signals having different image-forming positions obtained by photoelectric conversion by the conversion means; and the integration until the detection means detects that the signal level of the video signal has reached a predetermined level. The control means performs integration by the means and controls so that the integrated video signal is stored in the storage means, and the combining means that combines the video signals stored in the storage means. .

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a block diagram of the configuration of an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes Vari, which is an image forming position changing means.
-Angle-Prism (VAP), 2 is a diaphragm, 3 is an imaging lens system which is an imaging optical system, and 4 is a CCD (Cha) which is a photoelectric conversion means.
rge-coupled device), 5 is double correlation sampling (C
DS) circuit, 6 is an A / D converter.

Reference numeral 7 is an adder which is an integrating means, 8 is a first frame memory, 9 is a brightness level detecting circuit which is detecting means, 10 is an MPU which is controlling means, 11 is a gate circuit,
12 is a switch.

Further, 13-1 is a second frame memory,
Reference numeral 13-2 is a third frame memory, 13-3 is a fourth frame memory, and 13-4 is a fifth frame memory. A storage means is configured by the frame memories 13-1 to 13-4.

Reference numeral 14 is a signal processing circuit as a synthesizing means, and 15
Is an output terminal, 16 is a VAP control circuit, 17 is a horizontal direction V
AP actuator, 18 is a vertical direction VAP actuator, and 19 is a luminance evaluation detection circuit.

Next, the operation of the embodiment of the present invention will be described with reference to FIG. C through VAP1, diaphragm 2, and imaging lens system 3
The optical image formed on the light receiving surface of CD4 is photoelectrically converted,
After noise is removed by the double correlation sampling circuit 5,
The digital signal is converted by the A / D converter 6. The digital signal is supplied to the CCD 4 in the brightness evaluation detection circuit 19.
The brightness information of the optical image incident on is detected and transferred to the MPU 10. The MPU 10 controls the diaphragm 2 using the brightness information. When the amount of light incident on the CCD 4 is sufficiently large and the output signal of the CCD 4 is saturated, the diaphragm 2
Due to this, the amount of incident light is adjusted appropriately.

The CCD signal converted into a digital signal by the A / D converter 6 is temporarily stored in the first frame memory 8 through the adder 7. Memory 8
The image data stored in is transferred to the switch 12 through the gate circuit 11.

The brightness level detection circuit 9 detects the brightness level of the image data, the amount of incident light is small, and the brightness level of the image data stored in the first frame memory 8 is less than a predetermined value. In this case, the MPU 10 opens the gate circuit 11 and stops the signal transmission to the switch 12 and thereafter. At this time, C stored in the first frame memory 8
The CD signal is fed back to the adder 7, added with the newly input CCD signal, and stored again in the first memory 8.

When the brightness level detecting circuit 9 detects that the brightness level of the CCD signal stored in the first frame memory 8 has reached a predetermined value by repeating the above integration operation, the gate circuit 11 is connected. The integrated CCD signal is transferred to the switch 12.

On the other hand, the VAP control circuit 16 uses the MPU 10
Based on the program, the image forming position of the optical image on the light receiving surface of the CCD 4 is the first position which is the first position, and the second position which is horizontally displaced from the first position by 1/2 pixel. , A third position horizontally / vertically displaced from the first position by 1/2 pixel, and a fourth position vertically displaced from the first position by 1/2 pixel. To do.

The output of the switch 12 is 0 to 3
Are connected to the memories 13-1 to 13-4, respectively, and are controlled so as to switch to 0, 1, 2, 3 respectively at the above-mentioned image forming positions. It Such an image-forming position changing operation and a switch operation are performed each time the integration operation is completed. Due to the integration operation and the imaging position changing operation as described above, the CCD 4
The image signals of are sequentially stored in four frame memories while being improved in S / N by integration. Then, the signals are combined in the signal processing circuit 14 and output from the output terminal 15.

In this embodiment, VAP is used to change the image forming position on the light receiving surface of the CCD, but it goes without saying that any method may be used.

Here, assuming that a still image is taken,
The optical image is constant regardless of changes over time, and the inter-frame correlation is almost 1. On the other hand, noise generated in a solid-state image sensor such as CCD is random, and the inter-frame correlation is very low. Therefore, with such a configuration, it is possible to capture a good S / N image even when the subject illuminance to be captured is low, and it is possible to provide a high-quality still image. Further, since the automatic gain control device is unnecessary, the circuit scale can be reduced and the cost can be reduced.

[0022]

As described above, according to the present invention, in the image pickup device, photoelectric conversion means for photoelectrically converting an optical image into a video signal,
An imaging optical system for forming an optical image on the photoelectric conversion means, an imaging position changing means for changing the imaging position of the optical image on the photoelectric conversion means by the imaging optical system, and the photoelectric conversion means. From the photoelectric conversion means by the image forming position changing means, an integrating means for temporally integrating the video signal outputted from the detecting means, a detecting means for detecting the signal level of the video signal integrated by the integrating means, and an optical image on the photoelectric converting means by the image forming position changing means. Storage means for storing a plurality of image signals having different image-forming positions obtained by photoelectric conversion by the photoelectric conversion means when the image-forming position of the image signal is changed to a predetermined position; The control means for performing integration by the integration means until it is detected that the signal level has reached a predetermined level, and for controlling the integrated video signal to be stored in the storage means, and the storage means. It was was configured as having a synthesizing means for synthesizing the video signal.

With this structure, an image with a good S / N can be captured, and a high-quality still image can be provided. Further, since the automatic gain control circuit is unnecessary, the circuit scale can be reduced and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a configuration block diagram of an image pickup apparatus according to an embodiment of the present invention.

[Explanation of symbols]

 1 VAP 7 adder 9 brightness level detection circuit

Claims (5)

[Claims] 1. A photoelectric conversion means for photoelectrically converting an optical image into a video signal, an imaging optical system for forming an optical image on the photoelectric conversion means, and an optical system on the photoelectric conversion means by the imaging optical system. Image formation position changing means for changing the image formation position of the image, integration means for temporally integrating the video signal output from the photoelectric conversion means, and detection of the signal level of the video signal integrated by the integration means. A detecting unit and an image forming position obtained by photoelectrically converting by the photoelectric converting unit when the image forming position of the optical image on the photoelectric converting unit is changed to a predetermined position by the image forming position changing unit. Storage means for storing a plurality of different video signals, and integration by the integration means until the detection means detects that the signal level of the video signal has reached a predetermined level, and the integrated video signal is recorded as described above. An image pickup apparatus comprising: a control unit that controls the storage unit to store the image signal; and a synthesizing unit that synthesizes the video signals stored in the storage unit. 2. The image pickup apparatus according to claim 1, wherein the storage unit is composed of a plurality of storage units. 3. The image pickup device according to claim 1, wherein the signal level is a brightness level. 4. The image pickup device according to claim 1, wherein the photoelectric conversion means is a CCD (Charge-coupled device). 5. The image pickup device according to claim 1, wherein the image forming position changing means is a VAP (Vari-Angle Prism).