JPH09168156A - Image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep white balance constant by correcting a color change at image pickup based on a high speed shutter through arithmetic operation under lighting of a fluorescent light by a commercial power supply with a frequency different from an image frequency. SOLUTION: A CCD solid-state image pickup element 12 receives an incident image pickup light from an image pickup lens 11 and an output signal is fed to an A/D converter 14 via an automatic gain adjustment circuit 13. The A/D converter 14 converts an analog image pickup signal into, e.g. a 10-bit digital image pickup signal and gives it to a camera core 15. The camera core 15 generates an output signal with respect to three primary colors and provides an output of a video signal via a video driver 16. A timing signal generating circuit 17b gives a timing signal TG to the CCD solid-state image pickup element 12, which is activated by using the signal as an electronic shutter. A CPU 19 detects a change in light quantity over plural fields via a detection circuit 18 to calculate a gain of each color to make white balance constant and gives a command it to the camera core 15.

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 in which a solid-state image pickup element (hereinafter referred to as CCD) functions as an electronic shutter, and particularly under a fluorescent lamp illumination using a commercial power source having a frequency different from an image frequency. The present invention relates to an image pickup apparatus that corrects a color change when an image is taken by a shutter.

[0002]

2. Description of the Related Art Conventionally, in a video camera using a CCD, for example, 60 image signals are transmitted per second, and the signal charge due to incident light accumulated in the pixels of the CCD is stored in one field. Read every period (1/60 seconds). At that time, by the function of the electronic shutter, the charge is once swept out within the period of one field, and then 1
By reading out the charges accumulated by the end of the field period, for example, a blur-free image can be obtained for a fast-moving subject.

[0003]

However, in a commercial power source area of 50 Hz such as eastern Japan, this 50 Hz
When an image is taken by the high-speed shutter using the above-described conventional image pickup device under the fluorescent lamp illumination which is turned on by the power supply of No. 1, the emission timing of the fluorescent lamp and the image pickup timing are deviated. For this reason, there is a problem in that the color-dependent light emission characteristics of the fluorescent lamp change over time, which causes a color change in the image as described below. That is, a commercial power source of 50 Hz has a cycle of 1/50 second (20
Since the fluorescent lamp that has a sine waveform of (msec) is turned on by the negative power supply voltage as shown in FIG. 2B, the period is 1/100 sec (10 msec). It will discharge and emit light.

On the other hand, in the video camera,
The vertical synchronization signal V-sync is, as shown in C of FIG.
Every 1 field period, 1/60 seconds (16.67m
This is a pulse signal transmitted every second). Therefore, the emission intensity of the fluorescent lamp and the vertical synchronization signal V-sync of the video camera
And are matched in a cycle of 3 fields.

Here, when the shutter speed of the electronic shutter is 1/100 second, as shown by D in FIG. 2, from the charge sweeping out in the pixels of the CCD to the charge reading by the vertical synchronizing signal V-sync. The charge accumulation timing is 1/100 second (10 msec).
As a result, the respective storage timings are sequentially out of phase with respect to the light emitting cycle of the fluorescent lamp, but since they are the same time as the light emitting cycle of the fluorescent lamp, they match the light emitting intensity of the fluorescent lamp for one cycle. It becomes the accumulated timing. Therefore, 1 /
In the charge reading by the electronic shutter for 100 seconds, the color unevenness at each accumulation timing becomes substantially uniform.

On the other hand, when the shutter speed of the electronic shutter is 1/500 second (2 msec), each accumulation timing becomes 1/5 shorter than the light emission cycle of the fluorescent lamp. The storage timing will be displaced for every three fields with respect to the light emission cycle of the fluorescent lamp.

The emission characteristics of the fluorescent lamp, as shown in FIG. 3, change in emission intensity for each color, that is, red, green, and blue, as time elapses from the start of emission. Therefore, if the accumulation timing is displaced with respect to the light emission cycle of the fluorescent lamp, not only the light emission intensity of the fluorescent lamp but also the spectral characteristics will change, and color unevenness will occur. Thus, there is a problem that the output image becomes very difficult to see due to the color unevenness changing sequentially for every three fields.

SUMMARY OF THE INVENTION In view of the above points, an object of the present invention is to provide an image pickup device capable of correcting a color change when an image is picked up by making a CCD function as a high-speed electronic shutter.

[0009]

According to the present invention, the above-mentioned object is to obtain an image pickup output signal by amplifying an image pickup means to which image pickup light enters through an image pickup optical means and an output signal from the image pickup means. In an image pickup apparatus including an amplification unit that generates an image output signal from the amplification unit, and an image processing unit that generates an image signal based on the image output signal from the amplification unit, the image pickup output signal from the amplification unit is detected to obtain three primary colors. A light amount detection unit that generates each light amount information, and the light amount information from the light amount detection unit detects the periodic light amount change of each of the three primary colors, and based on this light amount change, the white balance of the image signal. It is achieved by including a light amount change correction unit that corrects the image pickup output signal so that is constant.

According to the above construction, when the accumulation timing of the image pickup means with respect to the cycle of change of the emission intensity of the fluorescent lamp illumination is shifted and the respective light amounts of the three primary colors of the fluorescent lamp illumination are respectively changed, this change in light amount is detected, Moreover, since the image pickup output signal corresponding to the amount of change in the light amount is corrected, the white balance of the image pickup output signal input to the image processing means can always be kept constant.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. The embodiments described below are preferred specific examples of the present invention,
Although various technically preferred limits are given, the scope of the present invention is not limited to these embodiments unless otherwise specified in the following description.

FIG. 1 shows the configuration of an embodiment of an image pickup apparatus according to the present invention. The image pickup apparatus 10 includes an image pickup lens 11 as an image pickup optical unit on which image pickup light is incident and a solid-state image pickup device (CCD) 12 as an image pickup unit. Furthermore, an automatic gain adjusting circuit 13 as an amplifying means, which performs various processes based on the output signal from the CCD 12, an A / D converter 14, a camera core 15,
A video driver 16 as image processing means, a timing circuit 17, a detection circuit 18 as light amount detection means, and a CPU 19 as light amount change correction means are provided.

The automatic gain adjustment circuit 13 has a well-known structure, and amplifies the output signal from the CCD 12 to adjust the gain and sample and hold the signal.
An image pickup signal for one image is output. The A / D converter 14 converts an input analog signal into a digital signal and outputs the digital signal. The A / D converter 14 digitizes the image pickup signal from the automatic gain adjustment circuit 13 and outputs a 10-bit image pickup output signal, for example. It has become.

The camera core 15 includes an A / D converter 14
An output signal for the three primary colors is output based on the image pickup output signal from the CPU and the control signal from the CPU 19. The video driver 16 outputs a video signal to a television receiver, a video recorder or the like (not shown) based on the output signals of the three primary colors from the camera core 15.

The timing circuit 17 includes a video driver 1
6, a video drive signal generation circuit 17a for generating a video drive signal to be output to 6 and a timing signal generation circuit 17 for generating a timing signal for the electronic shutter of the CCD.
b and a sync signal generating circuit 17c for generating a vertical sync signal for the CCD are included, and are configured as, for example, one IC. The detection circuit 18 uses the image pickup output signal from the camera core 15 for the CPU 19 for one image.
The light amount information of the three primary colors is detected within the range specified by.

The CPU 19 is adapted to detect the light amount change amount based on the light amount information from the detection circuit 18. That is, for example, as shown in G of FIG.
Detects the amount of change in the light amount at the accumulation timing of each field that changes in a three-field cycle, calculates the gain of each color that makes the white balance of the imaging output signal constant, and controls the camera core 15 to control the camera core 1.
The gain adjustment of the signals of the respective colors output from 5 is performed. At that time, the CPU 19 makes one cycle (3
Each field X1, X2, X3 in the field)
The amount of change in the light amount is stored, and the white balance of the imaging output signals of the fields Y1, Y2, and Y3 in the next cycle (three fields) is adjusted, so-called feedforward is performed to correct the change in each color due to the change in the light amount. It is like this.

The camera core 15, the detection circuit 18, and the CPU 19 are connected to the serial communication bus 20 so that they can be input and output, and the timing signal generation circuit 17b and the synchronization signal generation circuit 17 of the timing circuit 17 are connected.
c is connected to the serial communication bus 20 so that it can be input. Further, the detection circuit 18 is connected to the camera core 15 by
/ D data bus 21 is connected.

Imaging device 10 according to an embodiment of the present invention.
Is configured as described above, and operates as follows. When the image is taken by the CCD 12,
The output signal from the CCD 12 is an automatic gain adjustment circuit 13
Is input, amplified, adjusted so as to have a constant gain, sampled and held, and an image pickup output signal representing one image is generated. This imaging output signal is A
It is input to the / D converter 14 and digitized. The digitized image pickup output signal is input to the camera core 15 and the detection circuit 18, and the light amount information of each of the three primary colors is detected within the range designated by the CPU 19 for one image represented by the image pickup output signal. These light quantity information is C
The light amount change amount is input to the PU 19 and the light amount change amount is detected based on each light amount information, and a control signal that makes the white balance of the image pickup output signal constant is output to the camera core 15 to perform gain adjustment for each color of the image pickup output signal. Done.

As a result, the signal of each color based on the image pickup output signal whose color change is corrected so that the white balance becomes constant is output from the camera core 15 to the video driver 16. Then, when the video signal is the video driver 16
Is input to a television receiver or a video recorder (not shown), and an image whose periodic color change is corrected is reproduced or recorded. Thus, even when a high-speed shutter is used under fluorescent lamp illumination in a commercial power source area of 50 Hz, for example, a color due to a fluorescent lamp emission characteristic due to a deviation of the accumulation timing due to the high-speed shutter with respect to a change in emission intensity of the fluorescent lamp. The change is the detection circuit 18 and the CPU 19
The white balance of the image pickup output signal can be held constant.

In the above-described embodiment, the case where the image frequency is 60 Hz and the power source frequency is 50 Hz has been described, but the present invention is not limited to this, and when the image frequency and the power source frequency are different, the high-speed shutter emits light from the fluorescent lamp. Obviously, the present invention can be applied when a color change based on characteristics occurs.

[0021]

As described above, according to the present invention,
With a simple configuration, it is possible to easily perform color correction at high speed shutter. Further, since the color correction can be performed only by software, it is possible to easily cope with the change of the model and the cost can be reduced.

[Brief description of the drawings]

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

FIG. 2 is a time chart showing a relationship between a commercial power supply of 50 Hz and an imaging timing in a conventional imaging device.

FIG. 3 is a graph showing the color-dependent light emission characteristics of a fluorescent lamp with a commercial power supply of 50 Hz.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Imaging device 11 Imaging lens (imaging optical means) 12 Solid-state imaging device (imaging means) 13 Automatic gain adjustment circuit (amplification means) 14 A / D converter 15 Camera core 16 Video driver (image processing means) 17 Timing circuit 18 Detection circuit (Light quantity detection means) 19 CPU (Light quantity change correction means) 20 Serial communication bus 21 A / D data bus

Claims (3)

[Claims] 1. An image pickup unit to which image pickup light is incident via an image pickup optical unit, an amplifying unit for amplifying an output signal from the image pickup unit to generate an image pickup output signal, and an image pickup output from the amplifying unit. In an image pickup apparatus including an image processing unit that generates an image signal based on a signal, a light amount detection unit that detects the image pickup output signal from the amplification unit and generates light amount information of each of the three primary colors; and the light amount detection unit. The amount of light from the means is used to detect the amount of periodic change in the amount of light of each of the three primary colors, and based on the amount of change in the amount of light, the amount of light that corrects the imaging output signal so that the white balance of the image signal becomes constant. An image pickup apparatus comprising: a change correction unit. 2. The light quantity change correction means stores a correction value for one cycle relating to the light quantity change, and uses this correction value as a white balance value for each field of the image pickup output signal for the three primary colors. A method for correcting a change in light amount
The imaging device according to. 3. The light quantity change correction means stores a correction value for one cycle relating to the light quantity change, and corrects the light quantity change of the three primary colors for the next cycle by feedforward. Imaging device.