JPS59196664A - Image pickup device used together with lighting fixture - Google Patents

Abstract

PURPOSE:To improve the distortion of an unnatural picture such as white level collapse or black level collapse even under a ligting source by providing a gamma characteristic control means to an image pickup device used together with a lighting source so as to approach an input and output characteristic in a signal processing circuit to a flat characteristic. CONSTITUTION:An output signal from an image pickup device 1 is separated into a luminance signal Y and chrominance signals R, G, B through a sample- holding circuit 2, the band is limited through LPFs 3-6 and then the result enters variable gamma circuits 7-10. When a power switch 25 for a strobo control circuit is turned on, a main capacitor in the strobo control circuit 25 is charged and also a high level signal is impressed to the variable gamma circuits 7-10 so as to change the gamma characteristic. Then, the image of a lighted object is converted into an electric signal by an image pickup device, and the gamma correction larger than the normal value is applied by the variable gamma circuits 7-10 and the result is led to a recorder 22.

Description

TECHNICAL FIELD The present invention relates to improving the image quality of an imaging device, particularly an imaging device used with an illumination device.

(Prior art) The signal voltage-emission output characteristic of a color picture tube can be approximated by the relational expression L-&Er, where E is the signal voltage, L is the emission output, and k is a constant.If this is expressed logarithmically, γ is its slope, and this is called the gamma characteristic of the picture tube. For color picture tubes, γ = 2.2 as shown in Figure 1, so if you directly apply a signal voltage proportional to the brightness of the subject obtained by a camera to a picture tube with non-linear characteristics, the brightness of the screen will change. Of course, a color image with distorted hue and saturation is reproduced, so in a color TV system, before applying the signal to the picture tube, the input characteristics are adjusted to 1/2 on the camera side as shown in Figure 2.
Through a nonlinear circuit that is squared, correction is made so that the overall characteristics, including the characteristics of the picture tube, are exactly linear. Here, we assume an Sv (still video) system in which a still image is taken with a camera that has undergone the above-mentioned γ correction and recorded on some kind of recording medium, and when using it with a strobe synchronized, γ If the characteristics are left as they are, the following problems will occur.

Figure 6 shows the relationship between the distance and the amount of reflected light when a strobe is emitted.The amount of light decreases in inverse proportion to the square of the distance, so for example, A.

In the case where the subject at points B and C3 are included in the photograph, if the proper exposure is obtained for the subject at distance B, the subject at point A will be too bright and white, and the subject at point C will be too dark and blurred. This results in an image that is difficult to see. This is because the dynamic range of video cameras is extremely narrow compared to silver halide film.

(Objective) An object of the present invention is to provide an imaging device capable of correcting such an unnatural screen with strong contrast to a visually natural image.

(Example) The present invention will be described in detail below based on examples.

FIG. 4 is a block diagram of an imaging device according to an embodiment of the present invention. Reference numeral 1 denotes an imaging device such as an OCD, and its output signal passes through a sample and hold circuit 2 and is separated into a luminance signal, Y2, color signals R, G, and BK, respectively.

Further, after passing through the LPFs 3 to 6 and being band limited, the 0 electric signals entering the variable gamma circuits 7 to 1o are converted into R-Y and B-Y color difference signals by the matrix circuit 16,
By the switch circuit 14, R-Y, B-Y, R-Y, .
After becoming a line-sequential color difference signal of . After passing through 16, HPFj 7, LPF 1F
3 and is synthesized by a mixing circuit 19 and sent to a recording amplifier 20.
The recording signal becomes a recording signal of a desired level, and is recorded by the head 21. 11 and 12 are a strobe control circuit and a strobe, respectively. 25 is a power switch for the strobe control circuit, and in this embodiment, this electrode switch, EJ variable gamma circuits 7 to 10, etc. have gamma characteristics fl.
i! are forming the means of control. 23 is a driver circuit of the imaging device 1, and 24 is a clock generator that supplies drive timing pulses to the driver circuit 23.

Figure 5 (Al is a diagram showing an example of the configuration of a variable γ circuit, Figure 5 (b) is a diagram showing an example of γ characteristics when power is not supplied to the strobe control circuit, Figure 5 (C) is a diagram showing an example of the γ characteristic when power is not supplied to the strobe control circuit. FIG. 2 is a diagram showing an example of γ characteristics when power is being supplied to the strobe control circuit.

In the figure, 44 is an input terminal, 27-61 are resistors, 32-64
is a diode, 65-67 is a switch circuit, 68-43
Fi constant voltage sources output potentials E1 to E6, respectively. 45
46 is a γ characteristic switching input terminal, and 46 is an output terminal.

FIG. 6 is a diagram showing an example of the configuration of the strobe control circuit 11 shown in FIG.
8 is a diode, 49 is a main capacitor, 50 is a trigger capacitor, 51 is a trigger switch, 52 is a trigger transformer, 56 is a trace/disconnect switch, 54 is a photometric circuit, 5
5 is an AND gate, and 56 is a timer circuit that outputs a high level signal only during the vertical scanning period in synchronization with the vertical synchronizing signal.

Further, a release signal for starting recording by the recording device is input to the input terminal of the AND gate 55.

In this embodiment, recording actually starts in response to the release signal from the 2U vertical synchronization signal, and a timer circuit is provided for this purpose, but it is not shown in the figure. Great.

Next, the operation of the modified embodiment shown in the circuits of FIGS. 4 to 6 will be explained.

When a power switch (not shown) is turned on, power supply to the entire imaging device is started.

As a result, the output of the imaging device begins to be supplied to the recording device. When the switch 25 is turned on in this state, high voltage is applied to the main capacitor 49 via the sixth illustrated converter 47, and charging is started.

Further, in conjunction with this, a high level signal is input to the γ characteristic switching input terminal 45 of each of the biteable gamma circuits 7 to 1o. Therefore, while a low level signal is applied to this terminal 45, the switches 65 to 67 are connected to the power supplies 68 to 40, respectively, whereas when a high level signal is applied to the terminal 45, the switches 35 to 67 are connected to the power supplies 68 to 40, respectively. It is connected to power supplies 41-46.

Therefore, the output voltage level from the output terminal 46 with respect to the incoming voltage level applied to the input terminal 44 has a γ characteristic that changes as shown by the broken line approximation in FIG. 5 (cl).

That is, in this embodiment, when the illumination light source is not used, γ2o is about 45 to 0.55 as shown in FIG. 2 or FIG. 5(b), and the illumination light source control circuit is turned on. 72 as shown in FIG. 5(b) or FIG.
It has been switched to a γ characteristic of around 0.6.

As a result, it was confirmed that the increase in contrast caused by illumination light sources such as strobes could be alleviated, and a more visually natural image could be obtained.

Incidentally, FIG. 8 is a diagram showing an example of the overall γ characteristic including the receiver when γ is set to 20.3 as in the example shown in FIG. Of course, the characteristic curve shown in FIG. 8 differs slightly depending on whether the brightness signal or color signal is used, or the γ characteristic specific to the imaging device.

Now, after charging of the main capacitor shown in Fig. 6 is completed, when the release button (not shown) is pressed, the recording device starts recording and the Antogame 1-55 (Fig. 6)
A high level signal is input to the switch 51 during the vertical scanning period, and the primary side of the transformer 52 is short-circuited, so a high voltage is applied to the trigger electrode of the strobe 120 and the strobe 12 is turned on.
Ii luminescence-jru. Then, the reflected light from the subject is detected by the 109 circuit 54, and when the photometric level exceeds the H level, the switch 56 is turned OFF and the light emission of the L strobe is stopped.

Such a light emitting operation is completed in approximately several QQPsec.

In addition, the image of the subject with this blurred illumination is captured (converted into an electrical signal by a device, and then subjected to larger γ correction than usual by variable gamma circuits 7 to 10, respectively) as a luminance signal and a line-sequential color difference signal. The signals are guided to a recording device 22 and recorded after being modulated.

In the above embodiments, illumination using a strobe light has been described, but it goes without saying that the present invention is also effective when illuminating with ordinary tungsten light or the like.

FIG. 9 is a diagram showing a second embodiment of the present invention ψ, which is a power switch for controlling power supply to illumination light 17@57 such as a tungsten light source, and this switch 58 and the light source The level of the connection point in FIG. 5 is input to the - terminal 45.

In this case, the AT source switch 58 and the variable gamma circuit 7~
10 functions as γ characteristic control means.

Furthermore, in these embodiments, the γ characteristics are switched when power supply to the illumination light source or strobe control circuit starts.
This switching may be performed automatically in the illumination photographing mode before the video signal of the illuminated object is input to the gamma characteristic control means.

Therefore, for example, as in the third embodiment shown in FIG. 10, the fact that the charge level of the main capacitor 49 reaches a predetermined voltage is detected by a detection means consisting of a resistor 59, 60 and a comparator 61, and the output of this comparator 61, that is, the illumination light source. A high level may be input to the terminal 45 of the gamma circuit in response to the completion of preparation.

In this case, the comparator 61 and the variable gamma circuits 7 to 1
0 etc. function as a γ characteristic control means.

Alternatively, a high level input may be made to the terminal 45 when the lighting device is electrically or mechanically connected to the imaging device.

FIG. 11 is a diagram showing a fourth embodiment of the present invention,
In the figure, reference numeral 62 denotes an illumination device with a built-in illumination light source, 66 a convex portion, and 64a, 64b engagement protrusions provided on the imaging device main body 65 that can be engaged with the convex portion 66.

Reference numeral 66 designates a pin that elastically protrudes from the image pickup device main body by an elastic body (not shown), and one end of the pin is in a position where the contact piece of the switch 67 can be pushed down, and the convex portion 66 engages with the engagement protrusions 64a and 64b. The configuration is such that the corresponding switch 67 is turned on.

One end of the switch 67 is connected to a positive voltage source, and the other end is grounded via a resistor 68.

Further, the connection point with the resistor is connected to the terminal 45 in FIG. 5(a).

With this configuration, γ can be switched as the illumination device is connected to the imaging device.

In this embodiment, the switch 67, the variable gamma circuits 7 to 10, etc. form the γ characteristic control means.

Furthermore, if the illumination mode is configured to be switched to by bringing up the illumination light source from the imaging device, γ may be switched in conjunction with this pop-up.

FIG. 12 is a diagram illustrating a fifth embodiment of the present invention, in which a lighting unit 69 built into the main body 65 can protrude from the upper part 78 of the main body. It is configured to be exposed from 7
1 is a bottle on the main body side, 72 is a bottle provided in the unit 69, and a tension spring 7 is stretched between both pins. 7
Reference numeral 4 denotes a stopper provided on the unit 69, which comes into contact with a part of the main body in a state where the unit protrudes a predetermined amount from the main body by the groove 7.

Reference numeral 75 denotes a bin provided in the unit 69, with which a lever 76 can engage.

The lever 76 is rotatable around the axis AX.
ORP, which is urged to rotate clockwise by SP, is a stopper for regulating this lever 760 rotation.

A switch 77 forms the gamma characteristic switching means of the present invention together with the variable gamma circuits 7 to 10, and is turned on when the unit 69 protrudes and comes into contact with the bin 75.

The sleeve of the lever 76 is configured so that it can be disengaged from the bin 75 from outside the imaging device main body by a member (not shown). With this configuration, when the lever 76 is removed from the bin 75 in the illumination mode, The unit 69 protrudes from the main body and the switch 77 is turned on. Turn on this switch 77
Alternatively, power supply or charging to the lighting device may be started.

Further, γ may be changed in accordance with the operation of a release button for recording after the lighting device such as a strobe is set up or after the preparation is completed. 79 is a diagram showing an example, and 79 is an AND gate;
80.81 is a one-shot circuit.

In this embodiment, the power switch 25 shown in the fourth figure is turned on,
When the release signal from the release button is output, a high-level pulse is output from the AND gate 79 in synchronization with the subsequent hematemesis synchronization No. 11, and in synchronization with this rise, the one-shot circuit 80 outputs a one-field pulse. A high level signal is output, and in synchronization with the fall of this signal, a high level signal is output from the one-shot circuit 81 for a predetermined period of time and is input to the terminal 45 shown in FIG. 5(a).

In this embodiment, the AND gate 79, the one-shot circuit 80, the variable gamma circuits 7 to 10, etc. form a γ characteristic control means. In the embodiment, a COD was considered as the imaging device, but
Needless to say, this may be an X-Y address type MOS sensor or an image pickup tube.

Further, in the above embodiment, the gamma characteristic control means is configured to switch the gamma values of the gamma correction circuits 7 to 100 in the imaging device, but instead of being configured in this way, a A linear amplification circuit may be provided for the Y signal and each color signal, and by controlling this, the gamma characteristics of the imaging device may be changed.

It should be noted that, compared to the case of this configuration, the configuration in which the gamma value of the gamma correction circuit is changed as in the first to sixth embodiments has a lower Q (effect). As explained above, according to the present invention, when imaging is performed using an illumination light source, by automatically changing the γ characteristic, the input/output characteristic in the signal processing circuit is made close to flat, so even the width of the illumination light source is not so-called white. There is no possibility of unnatural images such as blurring or blackouts.X1'0 Also, since such changes in γ characteristics are automatically performed as the illumination light is used, it is easy to operate. .

[Brief explanation of the drawings] Figure 1 is a diagram showing the γ characteristics of a color receiver, Figure 2 is a diagram showing the γ4V characteristics of a conventional video camera, and Figure 6 is a diagram showing the distance from the illumination source and the reflected scene. FIG. 4 is a diagram showing a configuration example of the imaging device of the present invention, and FIG. 5(a) is a diagram showing the relationship.
A diagram showing an example of the circuit configuration, Figure 5 (bl is a line diagram of the normal γ characteristic of the circuit in Figure 5 (ml), and Figure 5 (C) is a diagram showing the case of using an illumination light source with the circuit in Figure 5 (al) Figure 6 is a diagram showing a good example of the 7-trobofuntrol circuit shown in Figure 4. Figure 7 is a diagram showing an example of the γ characteristic when using an illumination light source. 7 is a diagram showing the overall γ characteristic in the case of the γ characteristic shown in FIG. , FIG. 11 is a diagram of the fourth embodiment, FIG. 12 is a diagram of the fifth embodiment, and FIG. 16 is a diagram of the sixth embodiment. 1... Imaging device, 7- 10...5J
f jJ mass rate 14.25・Keyaki... Power switch for Nutrobo control σ-control circuit. Applicant: Canon Co., Ltd. 6 4 Ljiro (incident light chamber Ql'1)l

Claims (1)

[Scope of Claims] (1) An imaging device used together with an illumination light source, characterized in that it is provided with gamma characteristic control means for changing the gamma characteristics of the imaging device as the illumination light source is used. Imaging device used. (2) The imaging device used with the lighting device according to claim (1), wherein the gamma characteristic control means changes the gamma characteristic of the imaging device as the illumination light source prepares to emit light. (6) The imaging device used with the lighting device according to claim (1), wherein the gamma characteristic control means changes the gamma characteristic of the imaging device upon completion of light emission preparation of the illumination light source.