JPH09102905A - Image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide proper exposure and to stabilize object field depth by adjusting the quantity of light excepting for the storage period for electric charges to fix aperture during a storage period. SOLUTION: Light received by a light receiving part 18 is sent to a light quantity detection circuit 22 for light quantity detection, the quantity of light is detected, and a signal based on that quantity of light is sent to an iris aperture adjusting part 24. Based on that signal, the adjusting part 24 drives a light quantity adjusting means 4 and changes the area of the aperture and the proper exposure can be provided. The quantity of light of a subject is received by the light receiving part 18 is detected 22 and the aperture of the iris is decided corresponding to that detected quantity of light. The iris aperture is always kept appropriate during the storage period. Therefore, the satisfactory image of appropriate exposure and stable object field depth can be provided for each frame. In this case, the quantity of light can be controlled for the period for moving the electric charges stored in an optic/electric converting part to a transfer part or for the period from the end of transfer period to the start of storage.

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 having an image pickup means for periodically accumulating and transferring photoelectrically converted charges.

[0002]

2. Description of the Related Art In a normal video camera, the amount of exposure to an image pickup means when shooting a moving image is controlled by controlling an aperture value by a diaphragm device. The degree of change in the aperture value is set so that it gradually changes to the desired aperture value over a period of several fields in order to prevent the image from flickering due to the rapid change in the exposure amount that accompanies the rapid change in the aperture value. Has been done.

An image pickup method in a conventional image pickup device will be described with reference to FIG. FIG. 4 is a schematic diagram of a CCD, which is an example of an image sensor. Reference numeral 30 in the drawing denotes a pixel which is a photoelectric conversion unit. A plurality of pixels 30 are arranged in the vertical and horizontal directions, and accumulate a certain amount of electric charge according to the amount of exposed light. That is, since there is a limit to the amount of charge that can be stored, the optical system is set to an appropriate exposure value by adjusting the aperture value or time value. 32 is pixel 3
This is a vertical register for vertically transferring and reading the charges accumulated in 0. The charge accumulated in the pixel 30 is transferred to the vertical register 32 and read by a charge read command (not shown). Reference numeral 34 is a horizontal register for transferring and reading the charges read out by the vertical register 32 in the horizontal direction. The charges accumulated in the pixels 30 are simultaneously accumulated in the vertical register 32 during a V blank period described later.
Read out after being transferred to.

Next, the operation of the CCD will be described with reference to FIG. In Figure 1, the image information is continuously acquired (exposed),
The timing of capturing an image with a video camera having a CCD as an image sensor for reading the image is shown. C1 in the figure
C2, C3, ... Denote image information obtained by photoelectric conversion by the CCD, respectively, in periods t0'-t1, t1'-t.
Charges converted from light by the pixel 30 are stored at 2, t2'-t3, .... Periods t1-t1 ', t2-t
2 ', t3-t3', ... Are V blank periods in which the accumulated charges are transferred to the passage for reading the charges. No charges are read during this V blank period. S1, S2, S3, ... Show image information read from the image pickup device corresponding to C1, C2, C3 ,. That is, the image information C1 accumulated in the period t0'-t1 in the figure is transferred to the vertical register 32 shown in FIG. 3 in the next V blank period t1-t1 ', and then the next period t1'-t2.
Is read through the vertical register 32 and the horizontal register 34. Further, C2 is accumulated in the above t1'-t2. Similarly, a continuous image is obtained by periodically repeating the operation of reading S2 for C2, S3 for C3, .... The vertical axis of FIG. 1 (a) shows the aperture, and in a normal video camera, the aperture is generally changed gently as shown in FIG. 1 (a) to prevent image flickering due to a sudden change in aperture area. So, I try to prevent unnaturalness when viewed as a movie.

[0005]

In recent years, as information equipment such as computers has become more sophisticated, there are increasing opportunities to handle continuous images taken by a video camera or the like on the screen of the computer. In this case, there are many opportunities to handle continuous images for each unit image such as one frame. However, in the case of capturing continuous images with a normal video camera, as described above,
In order to prevent image flicker due to abrupt change in exposure amount due to abrupt change in aperture value, it is set so that it gradually changes to a desired aperture value over a period of several frames. In many cases, the proper exposure was not always obtained when focusing on the image.

That is, when one frame of an image is extracted and viewed as a still image, it is necessary that the aperture value is appropriate at each shooting moment, but with such a gradual change, the aperture value changes moment by moment. There is a problem in that it is difficult to match the brightness of the subject, and there is a high possibility that the aperture value is not always appropriate. In addition, as shown in FIG. 1A, since the aperture value changes during the exposure period of the image sensor, the depth of field is not stable and the image quality as a still image deteriorates. There was a problem.

Therefore, in order to avoid the above-mentioned problems, it is possible to rapidly change the aperture value according to the brightness of the subject. However, when an electromagnetic means such as a voice coil motor is used as a power source for the operation of the diaphragm device that changes the aperture value, a high current is required together with a high-speed operation of the diaphragm device, and the influence of this large current causes a problem during reading. It is known that noise is added to image information S1, S2, S3, ... And image quality is deteriorated.

A first object of the present invention is to maintain a constant depth of field without changing the aperture value for each unit image in images obtained continuously, and to provide unit images of consecutive images. It is an object of the present invention to provide an image pickup apparatus capable of preventing deterioration of image quality when viewing one frame. A second object of the present invention is to provide an image pickup apparatus capable of preventing noise from being added to image information being transferred due to a large current or the like required for high-speed operation of the light amount adjusting means, and mitigating image deterioration due to noise. It is to be. A third object of the present invention is to prevent the occurrence of noise caused by the high-speed operation of the light amount adjusting means when the actual exposure period can be set by an electronic shutter or the like, and to mitigate the deterioration of the image due to the noise. Is to provide.

[0009]

According to the present invention, there is provided a photoelectric conversion section for converting light into electric charge and storing the electric charge, and a transfer section for transferring and reading the stored electric charge. There are provided an image pickup unit that periodically performs, a light amount adjustment unit that adjusts the incident light amount of the photoelectric conversion unit, and a control unit that performs control for executing the light amount adjustment operation by the light amount adjustment unit outside the accumulation period.

[0010]

According to the present invention, by adjusting the light quantity outside the charge accumulation period, the aperture during the accumulation period becomes constant, proper exposure is obtained, and the depth of field is stabilized.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a diagram showing the configuration of the image pickup unit of the image pickup apparatus. In FIG. 1, reference numeral 1 denotes the entire image pickup unit of the image pickup apparatus. Reference numeral 2 is an image pickup device such as a CCD having the configuration of FIG. Reference numeral 4 is a light amount adjusting means for limiting the amount of light incident on the image pickup device 2. Reference numeral 6 is an A / D converter for converting an analog signal of the image pickup device 2 into a digital signal, 8 is a process circuit for converting image information obtained by the image pickup device 2 into an RGB signal, etc. 10 is a whole image pickup portion of the camera It is the system controller that controls. 1
Reference numeral 2 is a monitor unit, and 14 is a recording unit. 16 is an image sensor 2
It is a high-frequency component detection circuit that detects a high-frequency component from the signal obtained by and generates a signal for focusing. 18
Is a light receiving section for detecting the light quantity. Reference numeral 20 denotes a focusing lens drive unit that drives a focusing lens 28, which will be described later, based on a signal from the high frequency component detection circuit 16. Reference numeral 22 is a light amount detection circuit that detects the light amount obtained by the light receiving unit 18 and generates a signal for setting the light amount to an appropriate value. Reference numeral 24 denotes an aperture opening adjusting section which drives the light amount adjusting means 4 based on the signal from the light amount detecting circuit 22. Reference numeral 26 is an optical system for forming a subject image on the image sensor 2, and 28 is a focusing lens.

Next, the operation will be described. Optical system 26,
A subject image, which has passed through the focusing lens 28 and whose light amount is appropriately adjusted by the light amount adjusting means 4, is formed on the image pickup element 2.
The image formed by the image sensor 2 is replaced with electric charges and read out, and is output to the A / D converter 6. The image information digitized by the A / D converter 6 is further processed by the process circuit 8 and then sent to the system controller 10. Image information is output from the system controller 10 to the monitor 12 or the recording unit 14 as necessary. Further, the image information is also used for focus detection.

Next, the focus detection operation will be described.
First, all or part of the image information for focus detection is sent from the system controller 10 to the high frequency component detection circuit 16, where it is processed for high frequency detection. Then, a signal based on the result is output to the focusing lens drive unit 20. The focusing lens drive unit 20 drives the focusing lens 28 to perform a focusing operation. Since the high-frequency component becomes the largest in the focused state, the focusing operation repeats the above-described operation to detect the position where the high-frequency component becomes the largest.

Next, the operation of adjusting the light quantity will be described.
The light received by the light receiving unit 18 is sent to the light amount detection circuit 22 for detecting the light amount, and the light amount is detected. The light amount detection circuit 22 outputs a signal based on the detected light amount to the aperture opening adjusting unit 2
Output to 4. The diaphragm aperture adjuster 24 drives the light amount adjuster 4 according to the signal to change the aperture area to obtain proper exposure. The light amount adjusting means 4 may be, for example, a diaphragm device that changes the area of the opening by rotation using a stepping motor or a voice coil motor of a light shielding member, or the light transmittance such as electrochromy is changed by voltage or the like. It may be a diaphragm with possible physical properties.

FIG. 1B shows the timing of shooting a moving image by the above-mentioned light amount adjusting operation. The vertical axis in the drawing represents the aperture of the diaphragm, which is the area of the aperture in the case of the diaphragm device in which the light shielding member is opened and closed, and represents the light transmittance converted into the aperture area in the physical property diaphragm. The light amount of the subject image received by the light receiving unit 18 is detected by the light amount detection circuit 22 and this opening is determined according to the detected light amount. This process is shown in Figure 1.
Since it is performed in real time in the V blank period of t1-t1 ', t2-t2', ... Of (b), the aperture opening is always properly fixed in the accumulation period of t0'-t1, t1'-t2 ,. . Therefore, it is possible to obtain a good image with proper exposure and stable depth of field for each frame.

Further, as described above, when the electromagnetic driving means such as the stepping motor or the voice coil motor is used, it is known that the current flowing during driving adds noise to the image information being transferred and the image quality is deteriorated. There is.
However, by determining the characteristics of the stepping motor or the voice coil motor so that the aperture is opened and closed within the V blank period, it is possible to prevent the deterioration of the image quality due to the addition of noise.

Next, a second embodiment of the present invention will be described. The configuration of the imaging device according to the second embodiment is the first
The same configuration as that shown in FIG. 2 described in the above embodiment is used. The present embodiment is a case where an electronic shutter is used for light amount adjustment. FIG. 3 is a diagram showing the relationship between the exposure and the aperture of the image sensor according to the second embodiment. The horizontal axis of the figure represents the passage of time. The photographing timing is a period for transferring the charge accumulated in the image sensor 2 during a substantially constant period t0'-t1, t1'-t2, t2'-t3, ... It is divided into V blank periods of periods t1-t1 ', t2-t2', t3-t3 ', ... Which are periods for transferring the charges accumulated in the pixels to the vertical register. These two periods are performed continuously with no gap. The timing indicated by ES in the drawing is an electronic shutter that clears the electric charge accumulated in the image sensor 2. The actual exposure is performed during the period t0 ″ − during which electric charges are accumulated after the electronic shutter is opened.
t1 (D1), t1 "-t2 (D2), t2" -t3
(D3), ... Then, the charges accumulated in the image sensor 2 in D1 are transferred to the vertical register in the subsequent V blank period and read out in the period T1. Similarly, the operation of reading D2 at T2, D3 at T3, ... Is periodically performed. The electronic shutter function of the image sensor 2 is controlled by the system controller 10.

As described above, the second embodiment is characterized in that the electronic shutter function of the image pickup device is utilized, whereby the time value in exposure can be adjusted, and the first value can be adjusted together with the adjustment of the aperture value. It is possible to shoot with a wider variety of exposures than in the first embodiment. For example, when a fast-moving subject is photographed, the time value can be reduced to photograph a moment when the movement of the subject is stopped on the image sensor. Therefore, one continuous image
When viewed as a unit image of a frame, a good image without blurring can be obtained.

The opening on the vertical axis in FIG. 3 represents the amount of light at the opening. The present invention is characterized in that the aperture is kept constant during actual exposure as shown in FIG. 3, but the aperture is gently changed during periods other than during actual exposure. In this way, by making the aperture constant during the actual exposure, for example, in a diaphragm device that opens and closes using a motor of a light shielding member, the shape of the aperture is stable, so that a good image with a stable depth of field is obtained. Obtainable.

When the opening is changed rapidly,
A diaphragm device using a motor as a power source needs a large current, and a diaphragm having physical properties needs to rapidly apply a high voltage. It is known that such a rapid change in current or the like in an electric circuit causes noise in image information being transferred as described above, resulting in deterioration of image quality. However, as in the present embodiment, the change in the opening is made as gradual as possible so that the change in the current or the like when changing the opening is made gradual and the generation of noise is suppressed, so that the deterioration of the image quality can be prevented.

[0021]

As described above, according to the image pickup apparatus of the present invention, the following effects can be obtained. According to the invention of claim 1, proper exposure can be performed for each unit image such as one frame of a moving image, and further, since the diaphragm aperture is fixed, an image with a stable depth of field can be obtained.
According to the second aspect of the present invention, it is possible to prevent a large current from flowing through the circuit while the image information is being read from the image pickup element, reduce noise added to the image information, and prevent deterioration of image quality due to noise. According to the third aspect of the present invention, the opening can be changed more gently than in the case where the opening is driven within the V blank period. Therefore, noise may be added to the image information due to the influence of the current or the like accompanying the rapid opening change. It is possible to prevent deterioration of image quality due to noise.

[Brief description of the drawings]

FIG. 1 is a timing chart showing an operation of a first embodiment of the present invention and a conventional image sensor.

FIG. 2 is a block diagram showing first and second embodiments of the present invention.

FIG. 3 is a timing chart showing the operation of the image sensor according to the second embodiment of the present invention.

FIG. 4 is a configuration diagram schematically showing a conventional image sensor.

[Explanation of symbols]

2 image sensor 4 light quantity adjusting means 10 system controller 18 light receiving section 22 light quantity detecting circuit 24 aperture opening adjusting section 30 pixels 32 vertical register 34 horizontal register C1 to C6 photoelectrically converted image information S1 to S6 read out image information t0 ′ -T1, ..., t5'-t6 accumulation period t1-t1 ', ..., t6-t6' transfer period (V blank period) ES electronic shutter

Claims (3)

[Claims] 1. An image pickup unit having a photoelectric conversion unit for converting light into charges and storing the charges, and a transfer unit for transferring and reading out the accumulated charges, and an image pickup unit for periodically performing the accumulation and transfer, An image pickup apparatus comprising: a light amount adjusting unit that adjusts an incident light amount of a photoelectric conversion unit; and a control unit that controls to perform the light amount adjusting operation by the light amount adjusting unit outside the accumulation period. 2. The image pickup device according to claim 1, wherein the control unit executes the light amount adjusting operation during a period in which the charges accumulated in the photoelectric conversion unit are transferred to the transfer unit. 3. The image pickup apparatus according to claim 1, wherein the control means controls a period from the end of the transfer period to the start of the accumulation, and the light amount adjusting operation is executed during this period.