JP2000209489A - Image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To hardly cause halation even in the exposure of a long time and to provide an appropriate exposure by smoothly changing the exposure from 1/60 seconds to 1/30 seconds. SOLUTION: The output of an A/D converter 4 is supplied to a field memory 5 and one of the terminals of an adder 6 and video signals delayed by one field in the field memory 5 are supplied to the other terminal of the adder 6. The signals are added in the adder 6 and the image pickup signal level of a solid-state image pickup element 1 is detected from the output of the adder 6 in a photometry circuit 7. In a solid-state image pickup element driving circuit 8, the exposure time of a desired solid-state image pickup element 1 is increased/ decreased so as to equalize lightness set by a lightness level setting circuit 9 with the output of the photometry circuit 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus, and more particularly, to an image pickup apparatus characterized in an exposure control section of a solid-state image pickup device.

[0002]

2. Description of the Related Art Hitherto, imaging apparatuses having an imaging element for photoelectrically converting a subject image and outputting it as an electric signal have been used in the field of medical television camera apparatuses such as TV cameras and electronic endoscopes, and industrial television camera apparatuses. Widely used. In such an image pickup apparatus, an image of a subject is photoelectrically converted by performing charge accumulation and transfer by an image pickup device to perform image pickup.

In the above-mentioned image pickup apparatus, various apparatuses have been proposed which are provided with sensitivity improving means for improving the sensitivity by changing the exposure period when the subject image is dark or the like so that a good subject image can be obtained. In particular, medical TV camera devices and industrial TV camera devices that are externally attached to an endoscope are intended to image the inside of a body or a lumen. The problem of shortage has been improved by an exposure method called long-time exposure.

[0004]

However, in the conventional long-time exposure, as shown in, for example, Japanese Patent Application Laid-Open No. 4-56484, the exposure time is simply set to a normal imaging cycle.
This is extended stepwise from / 60 seconds to 1/30 seconds, and has the following problems.

(1) When the subject is entirely dark, there is a practical aspect, but when there is a portion where the difference in brightness is relatively large, if the subject has an exposure time of 1/30 second, The bright portion was saturated, resulting in an image with so-called overexposure.

(2) The exposure time is reduced from 1/60 second to 1
Since the exposure time ratio was extended stepwise to / 30 seconds, the ratio of the exposure amount at the switching point was doubled, so that the exposure amount was not always appropriate.

The present invention has been made in view of the above circumstances, and it is difficult to cause overexposure even during long-time exposure, and the exposure amount from 1/60 second to 1/30 second is smooth. It is an object of the present invention to provide an imaging device capable of obtaining an appropriate exposure amount by changing to (1).

[0008]

According to the present invention, there is provided an image pickup apparatus comprising: a solid-state image pickup device for picking up an image of a subject; a field memory for storing a video signal from the solid-state image pickup device for one field period; An adder for adding an output delayed by one field period and an undelayed video signal that does not pass through the field memory; a photometer for measuring the brightness of a signal from the solid-state image sensor; and a brightness for setting a brightness level in advance A solid-state image sensor having drive level setting means, and exposure time setting means for setting an exposure time of the solid-state image sensor from an output from the photometric means and an output from the brightness level setting means. And a driving unit.

In the image pickup apparatus of the present invention, the solid-state image pickup device driving means picks up an image at a plurality of different times with the same or different exposure times, and the adder outputs the output delayed by one field period stored in the field memory and the output. By adding a video signal that does not pass through the field memory and is not delayed, overexposure is unlikely to occur even during long-time exposure,
In addition, an appropriate exposure amount can be obtained by smoothly changing the exposure amount from 1/60 seconds to 1/30 seconds.

[0010]

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

FIGS. 1 to 3 relate to an embodiment of the present invention. FIG. 1 is a configuration diagram showing a configuration of an image pickup apparatus. FIG. 2 is an explanatory diagram for explaining a dynamic range of the solid-state image pickup device of FIG. FIG. 3 is a timing chart for explaining the operation of the imaging apparatus of FIG.

In this embodiment, an external TV camera detachably attached to an eyepiece of an endoscope (not shown) as an image pickup means will be described as an example. However, the present invention is not limited to this. It may be an imaging means.

In the image pickup apparatus according to the present embodiment, as shown in FIG. 1, a video signal picked up by a solid-state image pickup device 1 in an external TV camera is supplied to a sample hold circuit 3 via a buffer circuit 2. . Sample hold circuit 3
Then, the signal of the solid-state imaging device 1 is converted into baseband,
The signal is input to the A / D converter 4.

The output of the A / D converter 4 is supplied to a field memory 5 and one terminal of an adder 6, and the other terminal of the adder 6 is supplied with a video signal delayed by one field in the field memory 5. These signals are added by the adder 6 and supplied to the subsequent image processing circuit 10, where the desired image processing (color separation, white balance, AG) is performed.
C, enhancement, etc.), output to the D / A converter 11, and output to the monitor via a buffer (not shown).

The output of the adder 6 is supplied to a photometric circuit 7, which detects the image signal level of the solid-state image sensor 1 and supplies the detected information to a solid-state image sensor drive circuit 8.

In the solid-state image pickup device driving circuit 8, the brightness set by the brightness level setting circuit 9 and the light metering circuit 7
And the exposure time of the desired solid-state imaging device 1 is increased or decreased so that the output of the solid-state imaging device 1 becomes equal. At this time, for example, 1/30
In order to obtain an exposure amount equivalent to a long exposure time of 2 seconds, both the A field and the B field are imaged at an exposure amount of 1/60 second, and these images are added by the adder 6 to obtain 1 / This is equivalent to the exposure amount in 30 seconds.

Although the photometric circuit 7 detects the image signal level of the solid-state image sensor 1 from the output of the adder 6,
The present invention is not limited to this, and the level of the imaging signal of the solid-state imaging device 1 may be detected from the output of the A / D converter 4 or the output of the field memory 5.

Next, the expansion of the dynamic range of the solid-state imaging device 1 by the above configuration will be described with reference to FIG. FIG. 2 is a graph showing the brightness level of the subject on the horizontal axis and the output level of the solid-state imaging device 1 on the vertical axis.

In general, when an image of a subject is picked up using the solid-state image pickup device 1, there is a saturation level Vsat as shown by the line (a), and it is not possible to obtain any more output. Therefore, for example, when the subject is imaged in 1/30 second, the output of the solid-state imaging device 1 becomes a polygonal line as shown by the line (b) with respect to the brightness level of the subject, and is saturated at the same exposure time. Only signals below the level can be reproduced.

On the other hand, if the same subject is imaged in 1/60 second, the line becomes a broken line as shown by the line (c), and the output level is halved with respect to the imaging in 1/30 second. However, it can have a wide dynamic range.

Therefore, 1/60 images taken at different times
By adding the video signals based on the exposure time of second, an output level equivalent to the video signal captured at 1/30 second can be obtained and an image having a wide dynamic range can be obtained as shown by the broken line in the figure. be able to.

Next, how the video signals are added will be described with reference to FIG.

As shown in FIG. 3A, the A / D converter 4 outputs A and B fields alternately. Also, this output is input to the field memory 5 and delayed by one field to obtain an output as shown in FIG.

Accordingly, the adder 6 outputs (A1 + B1), (A2 + B1), and (A) as shown in FIG.
2 + B2)... At this time, if the exposure time is 1/60 second, the output from the adder 6 can obtain the same brightness as the signal captured with the exposure time of 1/30 second, and the exposure time is 1/80 second. In this case, the output from the adder 6 can obtain the same brightness as the signal captured with an exposure time of 1/40 second.

Specifically, the brightness set by the brightness level setting circuit 9 is, for example, 1/4 in the image being picked up.
Assuming that the exposure time corresponds to the brightness at the exposure time of 0 second, the exposure time at the A field and the B field becomes 1/80 second, and the output from the adder 6 becomes the brightness set by the brightness level setting circuit 9.

The brightness setting value set by the brightness level setting circuit 9 to the solid-state image sensor driving circuit 8 is 1/2 of the brightness in the normal exposure mode of 1/60 second.

By imaging in this manner, a video signal imaged with an exposure time between 1/60 seconds and 1/30 seconds is imaged with an exposure time of 1/120 seconds to 1/60 seconds. It is possible to obtain equivalently by adding the obtained video signals, and it is possible to perform continuous light control.

The circuit for adding the video signal comprising the field memory and the adder is not limited to the position described in the above configuration.
It may be arranged in the middle of or after 0.

As described above, in the present embodiment,
The A and B fields are imaged with an exposure time that is half the exposure time corresponding to the brightness set by the brightness level setting circuit 9, and the output from the adder 6 is set to the brightness set by the brightness level setting circuit 9. Therefore, the brightness set by the brightness level setting circuit 9 can be continuously varied.

In the long-time exposure mode (1/30 second), the dynamic range of the solid-state image sensor is expanded by adding the image pickup signals obtained during the exposure time (1/60 second) in the normal exposure mode. In particular, it is possible to reliably prevent the occurrence of overexposure and the like even in an image with intense brightness, which is a feature of an image in the field of an endoscope.

[Supplementary Notes] (Supplementary note 1) A solid-state imaging device for imaging a subject, a field memory for storing video signals from the solid-state imaging device for one field period, and a one-field period stored in the field memory are delayed. An adder for adding an output and an undelayed video signal that does not pass through the field memory; a light meter for measuring the brightness of a signal from the solid-state imaging device; and a brightness level setting unit for setting a brightness level in advance. A solid-state imaging device driving unit that has an exposure time setting unit that sets an exposure time of the solid-state imaging device from an output from the photometric unit and an output from the brightness level setting unit, and that controls driving of the solid-state imaging device. The solid-state imaging device driving means performs imaging at the same or different exposure times at a plurality of different times.

(Supplementary Note 2) The image pickup apparatus according to supplementary note 1, wherein the photometry means measures the brightness of a signal from the solid-state imaging device from an output of the adder.

(Supplementary Note 3) The signal of the solid-state imaging device input to the photometric means is one of a plurality of signals input to the adder. Imaging device.

(Supplementary Note 4) The setting amount set by the brightness level setting means is １ ／ of a brightness level measured by using a signal output from the adder. Item 3. The imaging device according to Item 2.

(Appendix 5) The exposure time for long-time exposure is 1
3. The imaging apparatus according to claim 1, wherein the imaging time is 30 seconds.

(Supplementary Note 6) The exposure amount from 1/30 second to 1/60 second is exposed by the solid-state image pickup device driving means and the adder for 1 / N (real number of 60 ≦ N ≦ 120) seconds. 2. The imaging device according to claim 1, wherein the imaging device is obtained by adding video signals captured in time.

[0037]

As described above, according to the image pickup apparatus of the present invention, the solid-state image pickup device driving means picks up images at the same or different exposure times at a plurality of different times, and the adder stores one field stored in the field memory. Since the output delayed for a period is added to the video signal that is not delayed without passing through the field memory, overexposure is unlikely to occur even during long-time exposure, and the exposure amount ranges from 1/60 to 1/30 seconds. Has the effect that a proper exposure can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a configuration of an imaging device according to an embodiment of the present invention;

FIG. 2 is an explanatory diagram illustrating a dynamic range of the solid-state imaging device in FIG. 1;

FIG. 3 is a timing chart for explaining the operation of the imaging device of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Solid-state image sensor 2 ... Buffer circuit 3 ... Sample-hold circuit 4 ... A / D converter 5 ... Field memory 6 ... Adder 7 ... Photometry circuit 8 ... Solid-state image sensor drive circuit 9 ... Brightness level setting circuit 10 ... Image processing Process circuit 11: D / A converter

Claims (1)

[Claims] 1. A solid-state imaging device for imaging a subject, a field memory for storing a video signal from the solid-state imaging device for one field period, an output delayed by one field period stored in the field memory, and the field memory. An adder that adds a video signal that is not passed through without delay, a light meter that measures the brightness of the signal from the solid-state imaging device, a brightness level setting unit that sets a brightness level in advance, A solid-state imaging device driving unit that has an exposure time setting unit that sets an exposure time of the solid-state imaging device from an output and an output of the brightness level setting unit, and controls the driving of the solid-state imaging device. The imaging device is characterized in that the imaging is performed at a plurality of different times at the same or different exposure times.