JPH05110940A - Video camera - Google Patents

Abstract

PURPOSE:To prevent void from being generated even when the level of an image pickup signal is rapidly increased. CONSTITUTION:A video camera part and a photo-camera part are integrally arranged in a cabinet. A photosensor 51 is provided with the almost same characteristic as photosensors for the respective picture elements of an imaging device 12. The output of the photosensor 51 is integrated for each field, and an integration signal SIN is supplied to a controller 27. The integration signal SIN of each field is corresponding to the stored charge amount of the imaging device 12 in each field, therefore, to the level of the image pickup signal outputted from the imaging device 12 to the next field. When the integration signal SIN exceeds a prescribed value, the gain of an AGC amplifier 19a is lowered in the next field. Thus, the level of the image pickup signal can be prevented from being increased too much and even when the level of the image pickup signal is rapidly increased by stroboscopic light emission, the void is not generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video camera which outputs an image pickup signal output from an image pickup device via an AGC circuit.

[0002]

2. Description of the Related Art By using a video camera, it is possible to capture still images as well as moving images. However, the resolution of the video camera is lower than that of the photo camera (film camera), and it is often desired to use the photo camera together with the video camera. For example, it is conceivable to fix the photo camera to the video camera and operate the shutter of the photo camera while capturing a moving image with the video camera.

[0003]

Here, it is assumed that the strobe light is emitted when the shutter of the photo camera is operated. The amount of accumulated charge in the image pickup element sharply increases with the flash emission, and the level of the image pickup signal from the image pickup element also sharply increases.

However, a normal iris or AGC circuit in a video camera has a slow response and cannot follow an instantaneous change in the level of an image pickup signal.

Therefore, when the level of the image pickup signal suddenly increases, the AGC circuit operates with the same gain as that when the level of the image pickup signal is small, and the level of the image pickup signal becomes too high, so-called overexposure occurs. There was a risk of

This is true not only when strobe light is emitted, but also when the level of the image pickup signal suddenly increases for some reason.

Therefore, the present invention is intended to prevent overexposure even when the level of the image pickup signal suddenly increases.

[0008]

SUMMARY OF THE INVENTION According to the present invention, an image pickup device for outputting an image pickup signal according to a charge amount accumulated in a certain accumulation period in a subsequent field and a level of an image pickup signal outputted from the image pickup device are controlled. AGC circuit, an optical sensor having substantially the same characteristics as the optical sensor of each pixel of the image sensor, an integrator that integrates the output signal of this optical sensor for each storage period, and an output signal of the integrator for a certain storage period. When the level exceeds a predetermined value, the AGC control means is provided for controlling the gain of the AGC circuit to decrease by a predetermined amount in the subsequent field.

[0009]

The output signal of the integrator in each accumulation period corresponds to the accumulated charge amount of the image pickup element, and thus the level of the image pickup signal output from the image pickup element in the subsequent field. Therefore, when the output signal of the integrator exceeds a predetermined value, the gain of the AGC circuit is forcibly reduced in the subsequent field, so that the level of the image pickup signal can be prevented from becoming too large, and the occurrence of overexposure can be prevented. obtain.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In this example, a video camera and a photo camera are integrally formed.

FIG. 1 is a perspective view showing the overall structure. In the figure, 1 is a cabinet. Although not shown, a video camera unit including an image pickup device, a signal processing circuit, and the like, and a photo camera unit including a film loading mechanism, a film driving mechanism, and the like are built in the cabinet 1.

Reference numeral 2 denotes an image pickup lens of a video camera section,
Reference numeral 3 is an imaging lens of the photo camera unit. That is, the optical system of the video camera unit and the optical system of the photo camera unit are configured separately. The imaging lens 2 has a focal length f of 7 mm to 42 m.
A 6x zoom lens of m is used. On the other hand, as the imaging lens 3, a fixed focus lens having a focal length f of 55 mm is used.

Further, in this example, an electronic viewfinder including a small CRT is provided in the cabinet 1, and
A screen imaged by the video camera unit is displayed on the RT via the imaging lens 2. 4 is an eyecup. In addition,
No finder is provided to directly check the screen imaged by the photo camera unit via the imaging lens 3.

Numerals 5T and 5W are zoom operation buttons for zooming in the TELE direction and the WIDE direction, respectively. Reference numeral 6 is a recording button for recording an image pickup video signal output from the video camera unit on the VTR, and 7 is a shutter button of the photo camera unit. Further, 8 is a film rewind operation button.

FIG. 2 shows the structure of the video camera section. Image light from a subject passes through the imaging lens 2 and the iris 11 and is a single-plate CCD solid-state imaging device (field storage type) 12 having a complementary color checkered color filter.
Is supplied to.

The zoom driver 41 adjusts the zoom magnification of the image pickup lens 2. FIG. 7 shows a specific configuration of the zoom driver 41. In the figure,
Reference numeral 411 denotes a lens that constitutes the imaging lens 2 and is for adjusting the zoom magnification. By moving the position of this lens 411 back and forth by rotational drive,
The zoom ratio is adjusted. For example, rotation to the T side adjusts in the TELE direction, while rotation to the W side adjusts in the WIDE direction.

The DC motor 412 drives the lens 411 to rotate. One end and the other end of the motor 412 are connected to the output terminals q1 and q2 of the zoom driver unit 413, respectively. The input terminals p1 and p2 of the zoom driver unit 413 are respectively connected to the zoom operation switch 4
2 is connected to the T-side and W-side fixed terminals.

In this case, when a high level "H" signal is supplied to the terminal p1, current flows through the motor 412 in the direction from the terminal q1 to the terminal q2 (shown by the solid line), and the lens 411 rotates in the T direction. Driven. Conversely, when a high level “H” signal is supplied to the terminal p2, the terminal q2
A current flows from the terminal q1 to the motor 412 in the direction from the terminal q1 (shown by a broken line), and the lens 411 is rotationally driven in the W direction. When a high level “H” signal is not supplied to either of the terminals p1 and p2, no current flows in the motor 412, the lens 411 is not rotationally driven in either direction, and its position is maintained. To be done.

The movable terminal of the zoom operation switch 42 is connected to the power supply terminal. Operation button 5 of the cabinet 1 described above
When pressing T or 5W, the zoom operation switch 42 is connected to the T side and the W side, respectively. Zoom operation switch 4
When 2 is connected to the T side and the W side, a high level “H” signal is supplied to the terminals p1 and p2 of the zoom driver unit 413, and zoom adjustment is performed in the TELE direction and the WIDE direction.

FIG. 3 is a schematic diagram of color coding of the image pickup device 12. As shown in the figure, field reading is performed. In the A field, charges are mixed in pairs such as A1 and A2, and in the B field, charges are mixed in pairs such as B1 and B2. Then, from the horizontal shift register Hreg, A1, A2, ...
.. in the order of B, B1, B2, ...

Here, the order of charges a, b, ... Is (Cy +) in line A1 as shown in FIG.
G), (Ye + Mg), ..., (Cy + Mg), (Ye + G), ... on the A2 line, and (G + Cy), (Mg + Y) on the B1 line.
e), ..., and in the B2 line, (Mg +
Cy), (G + Ye), ...

Returning to FIG. 2, the electric charge output from the image pickup device 12 as described above is supplied to the CDS circuit (correlated double sampling circuit) 13 and taken out from the CDS circuit 13 as an image pickup signal. By using this CDS circuit 13, reset noise can be reduced as is well known.

The timing pulse required by the image pickup device 12 and the CDS circuit 13 is supplied from the timing generator 14. The timing generator 14 has 8
Reference clock CK0 of fsc (fsc is color subcarrier frequency)
And the horizontal and vertical sync signals HD and VD are supplied from the sync generator 16. On the other hand, the synchronization generator 1
6 is a clock CK of 4 fsc from the timing generator 14.
1 is supplied.

The image pickup signal output from the CDS circuit 13 is supplied to the level detection circuit 17, and the output signal of the detection circuit 17 is supplied to the iris driver 18. And
The iris driver 18 automatically controls the aperture of the iris 11.

Now, the processing for obtaining the luminance signal Y and the chroma signal (color difference signal) from the image pickup signal output from the CDS circuit 13 will be described.

The luminance signal Y is obtained by adding the adjacent signals. In FIG. 4, a + b, b +
The addition signals of c, c + d, d + e, ... Are sequentially formed.

For example, the A1 line is approximated by the following equation. Here, Cy = B + G, Ye = R + G, Mg
= B + R.

Y = {(Cy + G) + (Ye + Mg))} × 1/2 = (2B + 3G + 2R) × 1/2 Further, the A2 line is approximated by the following equation.

Y = {(Cy + Mg) + (Ye + G))} × 1/2 = (2B + 3G + 2R) × 1/2 Other lines of the A field and lines of the B field are similarly approximated.

The chroma signal is obtained by subtracting adjacent signals.

For example, the A1 line is approximated by the following equation.

RY = (Ye + Mg)-(Cy + G) = (2R-G) Further, the A2 line is approximated by the following equation.

-(BY) = (Ye + G)-(Cy-Mg) =-(2B-G) The red difference signal R-Y and the red difference signal R-Y are similarly applied to the other lines of the A field and the line of the B field. The blue difference signal- (BY) is obtained line-sequentially and alternately.

Returning to FIG. 2, the image pickup signal output from the CDS circuit 13 is supplied to the AGC amplifier 19a. The output signal of the AGC amplifier 19a is the level detection circuit 19b.
The output signal of the detection circuit 19b is supplied to the AGC amplifier 19a as a control voltage via the buffer 19c. For example, the control voltage changes in the range of 2 to 4V, and the gain of the AGC amplifier 19a is correspondingly 10
˜29 dB (illustrated in FIG. 8). In this case, the control voltage is constant at 2V during the operation period of the iris 11.

The image pickup signal output from the AGC amplifier 19a is supplied to the low-pass filter 20 which constitutes the brightness processing section. The low-pass filter 20 performs an addition process (averaging) of adjacent signals. Therefore, the luminance signal Y is output from the low-pass filter 20.

Further, the image pickup signal output from the AGC amplifier 19a is supplied to the sample hold circuits 21 and 22 constituting the chroma processing section. Sample and hold circuit 2
Sampling pulses SHP1 and SHP2 (illustrated by E and F in FIGS. 5 and 6) are supplied to timings 1 and 22 from the timing generator 14.

From the sample hold circuit 21, (Cy
A continuous signal S1 of + G) or (Cy + Mg) is output and supplied to the subtractor 23 (shown in FIGS. 5B and 6B). From the sample hold circuit 22, (Ye + M
g) or (Ye + G) continuous signal S2 is output and supplied to the subtractor 23 (shown in FIGS. 5C and 6C).

The subtractor 23 subtracts the signal S1 from the signal S2. Therefore, the subtractor 23 outputs the red color difference signal RY and the blue color difference signal-(BY) alternately line-sequentially (shown in FIGS. 5D and 6D).

The color difference signal output from the subtractor 23 is directly supplied to the fixed terminal on the b side of the changeover switch 24 and the fixed terminal on the a side of the changeover switch 25, and has a delay circuit having a delay time of one horizontal period. It is supplied to the fixed terminal on the a side of the changeover switch 24 and the fixed terminal on the b side of the changeover switch 25 via 26.

The changeover of the changeover switches 24 and 25 is controlled by the controller 27. That is, one horizontal period in which the red color difference signal RY is output from the subtractor 23 is b
It is connected to the side a, and on the other hand, it is connected to the side a during one horizontal period in which the blue color difference signal-(BY) is output. The controller 27 is supplied with the synchronization signals HD and VD from the synchronization generator 16 as reference synchronization signals and the clock CK1 from the timing generator 14.

Since the changeover switches 24 and 25 are switched as described above, the changeover switch 24 outputs the red color difference signal RY in each horizontal period, and the changeover switch 25 outputs the blue color difference signal − (in each horizontal period. BY) is output.

The luminance signal Y output from the low-pass filter 20 is supplied to the encoder 28 via the gamma correction circuit 31, and at the same time, the color difference signals (RY) and-(B- are output from the changeover switches 24 and 25. Y) is encoder 2
8 are supplied. The encoder 28 has a synchronization generator 1
6) Composite sync signal SYNC, blanking signal BL
K, burst flag signal BF and color subcarrier signal SC
Is supplied.

In the encoder 28, as is well known, the synchronizing signal SYNC is added to the luminance signal Y, the quadrature two-phase modulation is performed to the color difference signal to form the carrier color signal C, and the color burst signal is added. .. And
The luminance signal Y and the carrier color signal C are added to form a color video signal SCV of the NTSC system, for example. Color video signal S output from the encoder 28
The CV is led to the output terminal 29.

Further, the encoder 28 outputs a monochrome video signal SV (luminance signal Y to which the synchronizing signal SYNC is added), and the monochrome video signal SV is supplied to the electronic viewfinder 30 and an image pickup screen is displayed on a small CRT. To be done.

Reference numeral 51 is an optical sensor having substantially the same characteristics as the optical sensor of each pixel of the image pickup device 12. The output signal of the optical sensor 51 is supplied to an integrator 52 including an operational amplifier 52a and a capacitor 52b.

Switch 5 connected in parallel with capacitor 52b
3 is connected, and on / off of the switch 53 is controlled by the controller 27. That is, the switch 53 is turned on at the timing when the read pulse is supplied from the timing generator 14 to the image sensor 12, and the capacitor 52b is discharged. As a result, the integrator 52
Output signal SIN is reset to Vb.

As described above, the optical sensor 51 has the image pickup device 12
In addition to having almost the same characteristics as the optical sensor of each pixel of
Since the capacitor 52b is discharged at the timing of the read pulse supplied to the image sensor 12, the output signal SIN of the integrator 52 immediately before the switch 53 is turned on.
Corresponds to the accumulated charge amount of the image sensor 12, and thus the level of the image signal output from the image sensor 12 in the subsequent field.

The output signal SIN of the integrator 52 is supplied to the controller 27. When the level of the output signal SIN exceeds the predetermined value VTH, the controller 27 controls so that the larger the difference between the output signal SIN and the predetermined value VTH, the lower the gain of the AGC amplifier 19a. Here, the level of VTH is, for example, the output signal SIN of the integrator 52 when strobe light is emitted.
Is set slightly lower than the level reached by.

In the above structure, FIG. 9A is a vertical synchronizing signal VD, FIG. 9B is a read pulse of the image pickup device 12, FIG. 9D is accumulated charge in each field of the image pickup device 12, and E is an image pickup signal of each field. Shall be indicated.

As shown in FIG. 9C, when the strobe emits light corresponding to the (n + 2) th field, the accumulated charge amount of each pixel of the image pickup device 12 increases significantly in the (n + 2) th field (shown in FIG. 9F), and the integrator 52 is operated. The output signal SIN of (1) also changes similarly (illustrated in FIG. 9G). In FIGS. F and G, broken lines indicate the case where no stroboscopic light emission occurs.

In the (n + 2) th field where the strobe emits light, the level of the output signal SIN of the integrator 52 becomes higher than the predetermined value VTH, so that the AGC amplifier 19a of the next field, that is, the field in which the image pickup signal of the (n + 2) th field is output. The gain is controlled so as to decrease, and the level of the image pickup signal output from the AGC amplifier 19a is suppressed.

That is, FIG. 9H shows the image pickup signal output from the AGC amplifier 19a, but the image pickup signal of the (n + 2) th field is at the level shown by the solid line. That is, when the normal AGC operation is performed, A
The gain of the GC amplifier 19a is substantially equal to the state in the previous field, and the image pickup signal output from the AGC amplifier 19a becomes too large to cause overexposure (illustrated by a broken line). However, in this example, as described above, the AGC amplifier 1
Since the gain of 9a is controlled so as to decrease, the image pickup signal does not become too large (shown by the solid line).
Here, the alternate long and short dash line indicates the level when there is no stroboscopic light emission and the AGC operation is not performed. Further, the alternate long and short dash line corresponding to the image pickup signals of the nth and (n + 1) th fields shows the level when the AGC operation is not performed.

Note that in the example of FIG.
Even in the +4 field, the amount of charge accumulated in each pixel of the image pickup device 12 significantly increases, and the level of the output signal SIN of the integrator 52 becomes larger than the predetermined value VTH. Therefore, the gain of the AGC amplifier 19a is controlled to decrease in the next field, the level of the image pickup signal output from the AGC amplifier 19a is suppressed, and the occurrence of overexposed highlights is suppressed. The broken line corresponding to the image pickup signal in the (n + 4) th field in FIG. 9H indicates the level when the normal AGC operation is performed.

By the way, in order to prevent the occurrence of overexposure,
When the gain of the AGC amplifier 19a is controlled so as to be reduced, the level is reduced to the black level region in which the overexhibition is not originally generated. In this example, the controller 27
The gamma value of the gamma correction circuit 31 is controlled to prevent deterioration of image quality in the black level area.

That is, the gamma value of the gamma correction circuit 31 is normally 0.45 because the gamma value of the picture tube is 2.2, but it is controlled so that the gain of the AGC amplifier 19a decreases. When 0.3 (Fig. 9I
(Illustrated in). In FIG. 10, γ = 0.3, γ = 0.45, γ =
1 shows each gamma characteristic. As a result, the level reduction amount in the black level region is suppressed as compared with the white level region, so that the black level region can be provided with sufficient contrast and the deterioration of the image quality can be prevented.

As described above, in this example, when the output signal SIN of the integrator 52 (corresponding to the level of the image pickup signal output from the image pickup device 12 to the next field) exceeds the predetermined value, the AGC is performed in the next field. Since the gain of the amplifier 19a is forcibly reduced, it is possible to prevent the level of the image pickup signal from becoming too high in the AGC amplifier 19a, and it is possible to prevent the occurrence of overexposure due to flash light emission or the like.

Further, when the gain of the AGC amplifier 19a is controlled to be reduced, the gamma value in the gamma correction circuit 31 is controlled to 0.3, so that the level reduction amount in the black level region is higher than that in the white level region. The image pickup device 12 in the above-described embodiment is of the field accumulation type, but is of the frame accumulation type. Of course, even if there is, it can be similarly applied.

Further, in the above-mentioned embodiment, the video camera and the photo camera are integrated, but the same applies to a type in which a separate photo camera is fixed to the video camera for use. be able to.

[0059]

According to the present invention, when the level of the image pickup signal output from the image pickup device exceeds a predetermined value, A
Since the gain of the GC circuit is forcibly reduced, it is possible to prevent the level of the image pickup signal from becoming too high, and it is possible to favorably prevent the occurrence of overexposed highlights.

[Brief description of drawings]

FIG. 1 is a perspective view showing an appearance of an embodiment.

FIG. 2 is a diagram showing a configuration of a video camera unit.

FIG. 3 is a schematic diagram of color coding.

FIG. 4 is a diagram showing an output of a horizontal output register.

FIG. 5 is a diagram for explaining color signal processing.

FIG. 6 is a diagram for explaining color signal processing.

FIG. 7 is a diagram showing a configuration of a zoom driver.

FIG. 8 is a diagram showing a gain control characteristic of an AGC amplifier.

FIG. 9 is a diagram showing an operation of an AGC circuit.

FIG. 10 is a diagram showing gamma characteristics.

[Explanation of symbols]

 1 Cabinet 2, 3 Imaging Lens 4 Eye Cup 5T, 5W Zoom Operation Button 6 Recording Button 7 Shutter Button 12 CCD Solid State Imaging Device 14 Timing Generator 16 Synchronization Generator 20 Low Pass Filter 21 and 22 Sample Hold Circuit 23 Subtractor 24, 25 Changeover switch 26 Delay circuit 27 Controller 28 Encoder 29 Output terminal 30 Electronic viewfinder 31 Gamma correction circuit 51 Optical sensor 52 Integrator

Claims (1)

[Claims] 1. An image pickup device for outputting an image pickup signal according to an amount of charges accumulated in a certain accumulation period in a subsequent field, an AGC circuit for controlling a level of an image pickup signal outputted from the image pickup device, and the image pickup device. The optical sensor having substantially the same characteristics as the optical sensor of each pixel of, the integrator that integrates the output signal of the optical sensor for each storage period, and the level of the output signal of the integrator that has a predetermined value during a certain storage period. A video camera provided with AGC control means for controlling the gain of the AGC circuit to decrease by a predetermined amount in the following field when exceeding.