JPS62178093A - Image pickup device - Google Patents

Abstract

PURPOSE:To compensate color temperature effectively even in the case of quick photographing under a fluorescent lamp by providing a means which sets a color temperature compensation level value in accordance with a detected phase position. CONSTITUTION:The luminance change signal of a light source detected by a photosensor 22 is inputted to a timing pulse generator 23, and the peak point of the luminance level is detected to generate a pulse. This output pulse is supplied to a CPU 25, and the CPU 25 detects individual phases to obtain the most suitable color temperature compensation level during the exposure period. The compensation value obtained by the CPU 25 in this manner controls level adjusting circuits 14 and 15 through switch circuits 26 and 27. Thus, the color temperature is compensated surely even in the case of photographing under the light source whose color temperature is changed periodically.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an imaging device having a color temperature compensation function that sets an appropriate state according to a change in color temperature of a light source.

[Conventional technology]

When a general TV camera performs white balance, it is in the same state as when it was shot under 1/1'libe 1゛, ≠,; The color signal level is compensated so that .

FIG. 4 is a circuit block diagram mainly of the signal processing system of a conventional television camera. Conventional television cameras generally have an exposure time of 1/60 second for the image sensor per field, but if you photograph a fast-moving subject and record it on a VTR, the still image will be clearer than it is without pre-screening. In order to reproduce a clear image, a method has been considered in which the exposure time for each field is set to be shorter than 1/6o second.

In Fig. 4, 1 is a lens optical system, 2 is a shutter,
3 is an image sensor, 4 is an amplifier, 5 is a demodulation circuit, 6 is an arithmetic circuit, 7 and 8 are level adjustment circuits, 9゜10 is a subtraction number M, 1
1.12 is a white balance circuit, 13 is a process circuit, 14.15 is a level adjustment circuit, 16 is a color temperature setting circuit, 17 is a modulation circuit, 18 is an addition circuit, 19 is a shutter drive circuit, 20 is a CPU, 21 is a This is a shutter speed setting circuit.

1-iF'above-'Ir 〃训京wat-Takashi IF Matsu 1 Haa 8! Imaging light obtained through the 7-lens optical system 1 is irradiated onto the image sensor 3 via the shutter 2. The image pickup charge accumulated by this image pickup element 3 for one screen is transferred to the CPU 2.
The output video signal is read out by a read clock supplied from 0, and the output video signal is supplied to a demodulation circuit 5 via an amplifier 4. This demodulation circuit 5 performs processing according to the color filter configuration of the image sensor 3, and finally three primary color signals of G, R, and H are obtained.

These three primary color signals are supplied to an arithmetic circuit 6, and the R and B signals are supplied to level adjustment circuits 7 and 8, respectively.

In the arithmetic circuit 6, the R, G, and B signals are multiplied by appropriate coefficients and synthesized to form a luminance signal. The arithmetic expression at that time is Y=O63OR+0.59G+0, IIB. Further, the outputs of the level adjustment circuits 7 and 8 are inputted to the positive polarity input sides of the subtraction circuits 9 and 10, and the luminance signal output of the arithmetic circuit 6 is inputted to the other negative polarity input side. From circuits 9 and 10, color difference signals (RY), (B-Y
) are obtained respectively. These color difference signals 1-Y), (B-Y
) is supplied to the white balance circuit 1.1.12.

Here, the reference level (0 level) and level it (i2
Then, set the control signal such that the difference becomes O to level 1!
: ■ Feedback to the adjustment circuits 7 and 8. However, the white balance adjustment in the level adjustment circuits 7 and 8 is performed when an image of a white object is captured. White balanced color difference signal (R-Y).

(B-Y) is further subjected to color temperature compensation in level adjustment circuits 14 and 15. Here, poor reproducibility of color vectors due to differences in color temperature of light sources such as fluorescent lamps, sunlight, and incandescent lamps is corrected. Further, since the level adjustment circuits 14 and 15 are controlled by the color temperature setting circuit 16 with appropriate correction values according to the light source used, the user can specify the type of light source to the color temperature setting circuit 16. . The outputs of the level adjustment circuits 14 and 15 are supplied to the modulation circuit 17 and subjected to quadrature two-phase modulation at the color subcarrier frequency fsc, and the output signal is input to one input terminal of the adder circuit 18.

On the other hand, the luminance signal is input to the other input terminal of the addition circuit 18 via the process circuit 13 for signal processing, and is added to the color signal. The television signal obtained in this way (
For example, the NTSC signal) is supplied to a monitor or a recording/reproducing device such as a VTR.

The CPU 20 is supplied with shutter speed information desired by the operator from the shutter speed setting circuit 21 .

The shutter drive circuit 19 operates the shutter 2 at the timing of a shutter drive pulse from the CPU 20.

FIG. 5 is a timing chart showing the shutter timing of the circuit block diagram of FIG. 4.

FIG. 5(a) shows a vertical synchronizing signal serving as a reference timing for imaging and reading of the image sensor 3, and the frequency is 60 Hz. 5(1)) is delayed by a predetermined time (T1 seconds) from the timing of the vertical synchronization signal so that the exposure time of 12 seconds from the shutter speed set by the shutter speed setting circuit 21 is completed immediately before reading out the accumulated charge. This is a pulse to make the FIG. 5 (cy) shows how the image sensor 3 is exposed in this way.
The accumulated signal weight is read out by drive pulses from the CPU 20, and the above-described processing is performed to generate a television signal.

[Problem that the invention seeks to solve]

In the conventional device described above, there is no problem if the light source is one whose color temperature does not change over time, such as sunlight or an incandescent lamp, but if the color temperature does not change over time, such as with a fluorescent lamp, there is no problem. When the shutter speed is long such as 1/15 or 1/30 seconds, the periodic color temperature changes are averaged, so a fixed control value from the color temperature setting circuit 16 is sufficient. For example, 1/250,115
When the time is as high as 00 seconds, the timing of the shutter open state differs depending on the position in the light emission cycle of the fluorescent lamp. Actual measurements show that the color temperature may vary by several hundred degrees. If this happens, then what? It is no longer possible to set the color humidity to a fixed value, and each image has a different hue. ``Tako's invention was made to solve these problems, and in particular, it was developed to effectively compensate for color temperature even when photographing at high speed under fluorescent light. The purpose is to provide an imaging device that can.

[Means for solving problems]

For a light source whose color temperature changes periodically, the imaging device according to the present invention detects at which phase position within the cycle when the actual imaging period is set to a period shorter than one field. and means for setting a color temperature compensation level value in accordance with the detected phase position.

[For production]

In this invention, even when imaging under a light source whose color temperature changes periodically, the phase of the color temperature change of the light source is detected in advance, and the actual imaging timing, which is shorter than one field, is the phase of the change. The relative relationship between the two is determined, and color temperature compensation is performed as appropriate according to the phase relationship using a previously known color temperature compensation level value.

〔Example〕

FIG. 1 is a circuit block diagram of a television camera equipped with a color temperature compensation device according to an embodiment of the present invention, in which 22 is an optical sensor, 23 is a timing pulse generator, 24 is a selection switch, 25 is a CPU, and 26° 27 is a switch circuit. Components with the same numbers as in FIG. 4 have the same or equivalent functions. Since the operation of the signal processing system is the same as that shown in FIG. 4, the explanation will be omitted.

In this invention, for example, when detecting periodic color temperature changes in fluorescent lamps, etc., the level changes are detected by applying the fact that, in the case of fluorescent lamps, there is generally a correlation between brightness level and color temperature. Detected by optical sensor.

FIG. 2 is a diagram showing the operation waveforms of FIG. 1, and the operation of FIG. 1 will be explained using each operation waveform of FIG. 2.

Luminance change signal C second of the light source detected by the optical sensor 22
2(a)) is input to the timing pulse generator 23, which detects, for example, the peak point of the brightness level and generates a pulse (FIG. 2(b)).

This output pulse is supplied to the CPU 25. Further, a desired shutter speed is inputted to the shutter speed setting circuit 21.

FIG. 2(b) shows a fluorescent lamp brightness timing signal, which is supplied from the timing pulse generator 23 to the CPU 25. FIG. 2(e) shows a 60H2 vertical synchronization signal fv which is generated within the CPU 25 and serves as a reference for creating timings for exposure and readout of the image sensor 3.

FIGS. 2(d) and 2(e) show delay pulses and exposure timing. This figure 2 is a diagram when the emission period of the fluorescent lamp is, for example, about 50 Hz, but due to the difference in frequency with the vertical synchronization signal fv, the fluorescent lamp timing during the exposure period T2 gradually shifts in phase. , phase θSl+θe1→θ84
+ θo4. Here, the phase θ8 is the phase at the start of exposure. is the phase at the end of exposure.

By detecting these respective phases, the CPU 25
The most suitable color temperature compensation level value is obtained during the exposure period. The compensation values thus determined by the CPU 25 control the level adjustment circuits 14 and 15 via switch circuits 26 and 27, respectively.

Figure 3 explains the color temperature compensation level value.
FIG. 3(a) shows the fluorescent lamp timing corresponding to the timing (in FIG. 2), which is normally 1150 seconds or 1/60 second. Now, assume that the above-mentioned exposure timing is from time t8 to 1 degree.

Then, the maximum brightness level of each fluorescent lamp is set to phase 0°.
Then, the phase of tSv te becomes θ8°θ0.

In addition, the blinking interval of the fluorescent lamp is divided into, for example, three stages depending on the difference in color temperature, and the highest brightness, that is, the highest color temperature is in the area A,
It is assumed that the intermediate brightness, that is, the intermediate color temperature part is a region B1, and the lowest brightness, that is, the lowest color temperature part is a region C, and each color temperature becomes lower in the order of A, B, and C.

As an algorithm for determining the color temperature compensation level value, phase θ8. Both of the above regions A and B of θ0.

If it is included in one of the stages of C, the color temperature is corrected accordingly, and if the respective phases are included in different regions, the color temperature compensation level value is calculated as the average value of the two for simplicity. You may also do this by taking . In order to perform more precise color temperature compensation, the color temperature compensation level value may be determined by weighting it depending on the proportion of each area occupied by the exposure period.

Furthermore, once the CPU 25 knows the set shutter speed, the type of light source, and the light emission phase of the light source, these calculations can be performed programmatically by detecting the timing of the PG pulse after the motor is locked.

Further, in the above embodiment, a fluorescent lamp (50 or 60 Hz) was used as an example, but it is not limited to this, and any frequency light source can be used. In that case, the type of light source can be selected by pressing the selection switch 24 input via the CP and control accordingly.
It would be good if it was done by U25.

Further, in the present invention, the high-speed shutter is mechanically realized by a shutter mechanism, but the present invention is not limited to this, and an equivalent operation can be performed by a method using a sequence of exposure and readout of the image sensor.

Furthermore, in this invention, the type of color temperature compensation is A,
Although there are three types of buildings, B and C, the structure is not limited to this, and for simplicity, two types may be used, and in consideration of higher shutter speed, multiple types of stages t)7 may be provided. .

Furthermore, when taking pictures using an AC power source, if we take into account that the cycle of the AC power source is synchronized with the change in brightness of the fluorescent lamp, the optical sensor used in this invention is no longer necessary, and more accurate images can be obtained. Changes in brightness level (phase changes) can be detected.

〔Effect of the invention〕

As explained above, the present invention performs substantial imaging for a light source whose color temperature changes periodically for a period shorter than one field, and detects at which phase position within the period this imaging period is located. and a means for setting a color temperature compensation level value according to the detected phase position, it is possible to reliably perform color temperature correction even when photographing under a light source whose color temperature changes periodically. Furthermore, when the TV multiplied signal corrected in this way is recorded on the VTR 1 or the like, the color temperature remains constant even during frame-by-frame playback of still images, resulting in a remarkable improvement in image quality.

[Brief explanation of drawings]

FIG. 1 is a circuit block diagram of a television camera equipped with a color temperature compensation device according to an embodiment of the present invention, FIG. 2 is an operation waveform diagram of FIG. 1, and FIG. 3 is an explanatory diagram of color temperature compensation level values. FIG. 4 is a circuit block diagram of a conventional television camera, and FIG. 5 is an operational waveform diagram of FIG. 4. In the figure, 1 is a lens optical system, 2 is a shutter, 3 is an image sensor, 4 is an amplifier, 5 is a demodulation circuit, 6 is an arithmetic circuit,
7 and 8 are level adjustment circuits, 9 and 10 are subtraction circuits, 11.
12 is a white balance circuit, 13 is a process circuit, 1
4. 15 is a level adjustment circuit, 16 is a color temperature setting circuit,
17 is a modulation circuit, 18 is an addition circuit, 19 is a shutter drive circuit, 20 is a CPU, 21 is a shutter speed setting circuit, 22 is an optical sensor, 23 is a timing pulse generator, 2
4 is a selection switch, 25 is a CPU, and 26.27 is a switch circuit.

Claims (1)

[Claims] In an imaging device that is equipped with a color temperature compensation means that sets an appropriate state according to changes in the color temperature of the light source and that performs substantial image capture in a period shorter than one field period, it is The present invention is characterized by comprising means for detecting at which phase position within the cycle the substantial imaging period is, and means for setting a color temperature compensation level value according to the detected phase position. Imaging device.