JPS6346074A - Image pickup device - Google Patents

Abstract

PURPOSE:To prevent deterioration of video signals by performing specified processing after logarithmically compressing photoelectrically converted signal without making gamma correction. CONSTITUTION:A signal processing circuit 50 having logarithmic compression characteristic (LOG) is provided in place of a signal processing circuit that includes a gamma correction circuit of 0.45 gamma characteristic. Accordingly, the output of an image pickup element is logarithmically compressed without gamma corrected, and recorded in a recording section 42. In this case, even when reproduced by a monitoring TV section 48 having 2.2 gamma characteristic, not so large image deterioration is felt as a cathode-ray tube itself is making light emission display.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an imaging device, and particularly to a signal processing method for an imaging device.

(Prior Art) In order to accurately reproduce the gradation of a subject, or in other words, to reproduce beautiful colors or images with sufficiently high resolution, the entire system, from the imaging device to the final monitor such as a television receiver, must be Gamma of comprehensive characteristics °°1
It is necessary to make it a pa.

On the other hand, the brightness of a cathode ray tube used in a monitor is not linear with respect to the input voltage, and although it depends on the brightness of the surroundings in which the cathode ray tube is viewed, the gamma characteristic is generally about 2.2. Therefore, in conventional imaging devices, it has been determined that gamma correction is to be performed so that the overall gamma characteristic of the entire system is 1, that is, the gamma characteristic is 0.45.

Such a processing system is shown in FIG. In FIG. 6, 40 indicates an image sensor, and 41 indicates a signal processing circuit including a gamma correction circuit with a gamma characteristic of 0.45. The imaging device 40 and the signal processing circuit 41 constitute an imaging section 43. Reference numeral 42 denotes a recording section that records signals output from the imaging section 43. 44
indicates a recording system including an imaging section 43 and a recording section 42.

Reference numeral 45 represents a reproducing unit that reproduces the signal recorded by the recording unit 42, and 48 represents a monitor unit including a cathode ray tube 46 having a gamma characteristic of 2.2.

[Problem to be solved by the invention]

Here, a conventional gamma correction circuit is configured as shown in FIG. 7-a, for example. In the figure, 101 is an input terminal, and 102 is an output terminal. A video signal obtained from an image pickup tube or solid-state image sensor is input to the terminal 101, and after gamma correction is performed by the circuit, it is output from the output terminal 102. be done. D1-D3 are diodes, R1-R3゜R8
is a resistor, E1 to E3 are voltage sources, and the voltage is the 7th-
As shown in Figure b. Such a gamma correction circuit is the seventh
Approximate gamma correction characteristics were achieved, as shown in Figure b.

Correction is performed by the gamma correction circuit configured as described above, and the recorded signal is reproduced by a device other than a cathode ray tube, such as a printer that prints the video signal on paper or a printing plate-making machine. Since this differs from the gamma characteristics of a cathode ray tube, the video signal from the imaging device is first subjected to inverse gamma correction, and then the video signal is processed, such as masking, to match the characteristics of the printer.

In other words, if the input level of the video signal is X, the gamma characteristic is γ
The output of the gamma correction circuit is Xγ, and the printer performs inverse gamma correction by taking the logarithm of this output.

fL　o　g　x’=γfl　o　g　x.

That is, processing as shown in the above equation is performed. Here, since X indicates the output of the image sensor, 9ogx corresponds to, for example, the density of the printer's ink, and is a signal suitable for processing such as masking, and printing is performed.

However, it is generally difficult for gamma correction circuits to faithfully reproduce gamma characteristics, and as shown in FIGS.
As shown in Figure b, an approximate method is used. For example, applying the aforementioned inverse gamma correction on the printer side to the gamma correction performed on the imaging device side is a major cause of video signal deterioration. It had become.

An object of the present invention is to provide an imaging device that solves this problem.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention includes a photoelectric conversion means for photoelectrically converting a subject image, and a means for performing predetermined processing after logarithmically compressing the photoelectrically converted signal without performing gamma correction. do.

[Effect]

Instead of gamma correction, a video signal is obtained which is logarithmically compressed and then subjected to predetermined processing.

〔Example〕

The present invention will be explained in detail below using the drawings.

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

In FIG. 1, elements having the same functions as those shown in FIG. 6 are designated by the same reference numerals, and explanations thereof will be omitted.

In place of the signal processing circuit including a gamma correction circuit with a gamma characteristic of 0.45 shown in FIG. 6, this embodiment is characterized by providing a signal processing circuit 50 having a logarithmic compression characteristic (LOG).

Therefore, in this embodiment, the output of the image sensor 40 is logarithmically compressed and recorded in the recording unit 40 without being subjected to gamma correction.

In this case, even if the image is reproduced on the monitor unit 48 having a gamma characteristic of 2.2, the cathode ray tube performs its own luminescent display, so you will not notice much image deterioration.

Furthermore, when a signal recorded by the device having the configuration shown in FIG. 1A is reproduced by the reproducing unit 45 shown in FIG. Since the reproduced signal corresponds to the density of the printer's ink and is suitable for processing such as masking, the masking processing section 57 performs the masking processing without applying reverse gamma correction as in the conventional method. Then, printing processing is performed in the printing section 51.

Similarly, the same applies when a signal recorded by the device having the configuration shown in FIG. 1a is reproduced by the reproducing unit 45 shown in FIG. Masking processing is performed in the masking processing section 57 without applying inverse gamma correction as in the past, and the masking processing is performed by the inverse logarithmic conversion section 55, and after being returned to an uncompressed video signal, the transmission operation is performed by the transmission section 56. will be carried out.

Next, the embodiment shown in FIG. 1a will be described in detail using FIGS. 2 and subsequent figures.

FIG. 2 is a block diagram showing the configuration of the imaging section 43 shown in the first diagram of the present invention.

In FIG. 2, 1 is a solid-state image sensor, such as a CCD or M
An O3 type XY address system or the like can be applied.

The arrangement of color filters of such an element 1 is shown in FIG. 2
is a low pass filter. The output of the filter 2 is output as a luminance signal to an edge enhancement circuit 5 via a delay circuit 3 and a logarithmic compression circuit 4. Reference numeral 3 denotes a delay circuit which corrects the phase shift of the luminance signal caused by the low pass filter 2 and keeps the phase relationship of the luminance signal with respect to the chroma signal always constant.

Circuit constants are set in advance so that the amount of delay caused by the low pass filter 2 and delay circuit 3 matches the amount of delay caused by low pass filters 18 and 19, which will be described later.

4 is a logarithmic compression circuit, and a low pass filter 2
This is to apply logarithmic compression to the output of . 5 is a contour compensation circuit that performs emphasis to raise high frequency characteristics.

6.7.8 are sample and hold circuits for separating the R, G, and By color signals, and 9 to 11 are R, G, and By circuits, respectively.
A balance circuit for white balancing each color signal of B, and logarithmic compression circuits 13 to 15 apply logarithmic compression to each color signal.

16 and 17 are subtraction machines, respectively RG.

Forms a BG signal. Reference numeral 18 and 19 are low pass filters, which are used to limit the color difference signal band to, for example, 500 KHz or less.

20 is a luminance signal, two color difference signals, a synchronization signal, etc., for example, NT.
This is an encoder for forming SC signals.

According to the embodiment described above, both the luminance signal and the color signal are logarithmically compressed without being subjected to gamma correction, and then converted into, for example, an NTSC signal by the encoder 20.

In the embodiment described above, the encoder 20 is used to
Next, using FIG. 4, we will discuss an embodiment that is configured to generate an SC signal, but is equipped with a recording device that modulates the luminance signal and chrominance signal that are input to the encoder 20 described above and records them on a disk-shaped magnetic sheet. explain.

FIG. 4 is a block diagram showing the configuration of such an embodiment.

In FIG. 4, 23 is a terminal to which the output of the contour emphasizing circuit 5 shown in FIG.
15 is a matrix circuit that outputs the color difference signals R-Y and B-Y, 26 is an FM modulator for the luminance signal Y, 27 is a recording amplifier, and 28 is a circuit that outputs the two color difference signals R-Y and B-Y line-sequentially. 29 is an F switch for line sequential color difference signals.
M modulator, 30 is a level adjustment circuit, 31 is a head, 32
is a magnetic sheet, 33 is a motor, 34 is a head feeding mechanism,
35 is a system controller.

The luminance signal that has been FM-modulated in a relatively high band by the FM modulator 26 and the line-sequential color difference signal that has been FM-modulated in a relatively low band by the FM modulator 29 are frequency-multiplexed by a recording amplifier and then output to the head. 31, the information is recorded on a sheet 32 which is being rotated at a constant speed by a motor 33. This mixed signal has a frequency spectrum as shown in FIG.

The system controller 35 moves the head eight times via the head feed mechanism 34 on a track specified by an operation section (not shown).

According to this embodiment, the output of the image pickup tube or image sensor is logarithmically compressed and recorded on the magnetic sheet without γ conversion. Therefore, when the video signal reproduced from the sheet is processed by a reproduction device such as a printer that does not use a cathode ray tube, there is no need to provide an inverse gamma correction circuit, and deterioration of the video signal can be prevented. The same applies to the above-mentioned electric transmission device. On the other hand, when the image is reproduced using a device using a cathode ray tube, there is no significant image deterioration.

Furthermore, in the above embodiment, the color difference signal was obtained after the R, G, and B color signals were logarithmically compressed by the logarithmic compression circuit 13.14.15. Logarithmic compression may be performed by circuits 13°, 14, and 15.

〔Effect of the invention〕

As explained above, according to the present invention, the level of the signal photoelectrically converted by the photoelectric conversion means is logarithmically compressed without applying gamma correction. There is no need to perform correction, and signal deterioration due to such correction or reverse correction can be prevented.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an imaging device according to a first embodiment of the present invention and the configuration of a device used together with the imaging device. FIG. 2 is a block diagram showing the configuration of the imaging section 43 shown in FIG. 1. 3 is a plan view showing the color filter pattern of the image sensor 1 shown in FIG. 2, FIG. 4 is a block diagram showing the configuration of the recording section 43, and FIG. 5 is the device shown in FIG. 4. FIG. 6 is a block diagram showing the configuration of a conventional imaging device. 1----1 solid-state image sensor 2-11 counting compression circuit

Claims (2)

[Claims] (1) An imaging device comprising: photoelectric conversion means for photoelectrically converting a subject image; and means for performing predetermined processing after logarithmically compressing the photoelectrically converted signal without performing gamma correction. (2) The means for performing the processing comprises means for logarithmically compressing the signal, means for modulating the logarithmically compressed signal by the means, and means for recording the signal modulated by the means on a medium. An imaging device according to claim 1, characterized in that: