JPH04371082A - Video camera - Google Patents

Abstract

PURPOSE:To obtain a video camera capable of using a stroboscope without causing the saturation of the storage charge of an image pickup element. CONSTITUTION:A video camera part and a photo camera part are integrally provided in a cabinet. A stroboscopic mode can be activated by a stroboscopic made setting switch 31 to be connected to a controller 27, and when a shutter button 7 is pressed in the stroboscopic mode, a stroboscope 33 emits light. In the stroboscopic mode, the opening of an iris 11 is reduced to approximately 1/3 by the control of the controller 27. The gain of an AGC amplifier 19a is forcedly dropped in a field where an image pickup signal obtained by picking up a picture with stroboscopic light is outputted from an image pickup element 12. A large amount of light will not come into the image pickup element 12 by the light emission from the stroboscope, and the saturation of storage charge will not be caused. Furthermore, too large level of the image pickup signal obtained by the image pick up with the light emission from the stroboscope which may result in the generation of white scattering, can be prevented.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video camera suitable for use in capturing still images.

0002

2. Description of the Related Art By using a video camera, it is possible to capture not only moving images but also still images.

0003

In this case, when the amount of light from the subject is insufficient, it is conceivable to use a strobe light so that the amount of charge accumulated in the image pickup device is sufficient.

However, when using a strobe, it is dark (low illuminance), so the iris is in an open state and the AGC circuit is in an operating period. Normally, the iris has a slow response, and a high amount of light from strobe light is incident on the image sensor. Therefore, if a strobe is used, there is a risk that the accumulated charges in the image sensor may become saturated.

Accordingly, it is an object of the present invention to provide a video camera that can use a strobe light without causing saturation of the accumulated charge in the image sensor.

[0006]

[Means for Solving the Problems] The present invention provides a strobe light emitting means, an iris for controlling the amount of light incident on an image sensor, an AGC circuit for controlling the level of an image signal output from the image sensor, and a strobe light emitting means. and a control means for reducing the aperture of the iris in the strobe mode and lowering the gain of the AGC circuit at the output timing of the imaging signal captured by the strobe light emission. It is.

[0007]

[Operation] In the strobe mode, the opening of the iris 11 is made small, so even if the strobe 33 emits light, a high amount of light will not be incident on the image sensor 12, and the accumulated charge will not become saturated.

[0008] When the opening of the iris 11 becomes smaller, the AG
The gain of the C circuit 19a is automatically increased to compensate for the decrease in the gain of the imaging signal. If the gain of the AGC circuit 19a remains raised even when the strobe 33 emits light, the level of the imaging signal will become too high and overexposure will occur. Since the gain of the AGC circuit 19a is lowered at the output timing, overexposure and the like will not occur.

[0009]

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 configuration. In the figure, 1 is a cabinet. Although not shown, the cabinet 1 includes a video camera section including an image sensor, a signal processing circuit, etc., and a photo camera section including a film loading mechanism, a film drive mechanism, etc.

2 is an imaging lens of the video camera section;
3 is an imaging lens of the photo camera section. That is, the optical systems of the video camera section and the photo camera section are configured separately. As the imaging lens 2, the focal length f is 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 with a focal length f of 55 mm is used.

Further, in this example, an electronic viewfinder made of a small CRT is provided in the cabinet 1.
A screen imaged by a video camera unit via an imaging lens 2 is displayed on RT. 4 is an eye cup. In addition,
A finder for directly checking the screen imaged by the photo camera section through the imaging lens 3 is not provided.

Further, 5T and 5W are zoom operation buttons for zooming in the TELE direction and WIDE direction, respectively. Reference numeral 6 represents a recording button for recording an imaged video signal outputted from the video camera unit onto a VTR, and 7 represents a shutter button. Furthermore, 8 is a film rewind operation button.

FIG. 2 shows the configuration of the video camera section. Image light from a subject is supplied via an imaging lens 2 and an iris 11 to a single-chip CCD solid-state image sensor 12 having a complementary color checkerboard color filter.

The zoom magnification of the imaging lens 2 is adjusted by a zoom driver 41. FIG. 7 shows a specific configuration of the zoom driver 41. In the same figure,
A lens 411 constitutes the imaging lens 2 and is used to adjust the zoom magnification. By moving the position of this lens 411 back and forth with rotational drive,
The zoom magnification is adjusted. For example, rotating it toward the T side adjusts it in the TELE direction, while rotating it toward the W side adjusts it in the WIDE direction.

This lens 411 is rotationally driven by a DC motor 412. One end and the other end of this motor 412 are connected to output terminals q1 and q2 of a zoom driver section 413, respectively. Input terminals p1 and p2 of the zoom driver section 413 are respectively connected to the zoom operation switch 4.
Connected to the fixed terminals on the T and W sides of 2.

In this case, when a high level "H" signal is supplied to the terminal p1, current flows to the motor 412 in the direction from the terminal q1 to the terminal q2 (shown by a 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 through the motor 412 in the direction of the terminal q1 (as shown by the broken line), and the lens 411 is rotationally driven in the W direction. In addition, high level "H" is applied to both terminals p1 and p2.
When this signal is not supplied, no current flows to the motor 412, and the lens 411 is not rotated in any direction and its position is maintained.

A movable terminal of the zoom operation switch 42 is connected to a power supply terminal. Operation button 5 of the cabinet 1 mentioned above
When pressing T and 5W, the zoom operation switch 42 is connected to the T side and the W side, respectively. Zoom operation switch 4
2 is connected to the T side and the W side, high level "H" signals are supplied to the terminals p1 and p2 of the zoom driver section 413, respectively, and zoom adjustment is performed in the TELE direction and the WIDE direction.

FIG. 3 is a schematic color coding diagram of the image sensor 12. As shown in FIG. 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, in the A field, A1, A2, .
In the B field, charges are output in the order of B1, B2, and so on.

Here, the order of charges a, b, . . . is (Cy+G) on line A1, as shown in FIG.
, (Ye+Mg),..., and on the A2 line, (Cy+Mg), (Ye+G),..., and B
In one line, (G+Cy), (Mg+Ye),
..., and in the B2 line, (Mg+Cy)
, (G+Ye), .

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

Timing pulses necessary for the image sensor 12 and the CDS circuit 13 are supplied from a timing generator 14. The timing generator 14 has 8 signals from the oscillator 15.
Reference clock C of fsc (fsc is color subcarrier frequency)
K0 is supplied, and horizontal and vertical synchronization signals HD and VD are supplied from the synchronization generator 16. On the other hand, the synchronous generator 16 is supplied with a 4 fsc clock CK1 from the timing generator 14.

The imaging signal output from the CDS circuit 13 is supplied to a level detection circuit 17a. This detection circuit 17
The output signal of a is sent to the iris driver 17b and the adder 1.
is supplied as a control signal to the iris 11 via 7c,
The aperture of the iris 11 is automatically controlled.

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

The luminance signal Y is obtained by adding adjacent signals together. In FIG. 4, a+b, b+
Addition signals c, c+d, d+e, . . . are formed in order.

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 Furthermore, on the A2 line, it is approximated by the following equation.

Y={(Cy+Mg)+(Ye+G))}×1/2=(
2B+3G+2R)×1/2 The other lines of the A field and the 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)=
(2RG-G) Also, on the A2 line, it is approximated as shown in the following equation.

−(B−Y)=(Ye+G)−(Cy−Mg)=−(2
B-G) Regarding the other lines of the A field and the lines of the B field, the red difference signal RY and the blue difference signal -(B-Y) are obtained alternately line-sequentially in the same way.

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 this AGC amplifier 19a is the level detection circuit 19b.
The output signal of this detection circuit 19b is supplied to the AGC amplifier 19a via a buffer 19c and a subtracter 19d.
is supplied as a control voltage. For example, if the control voltage is 2~
4V range, and the AGC amplifier 19 changes accordingly.
The gain of a is set to 10 to 29 dB (as shown in FIG. 8). In this case, the control voltage remains constant at 2V during the operation period of the iris 11.

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

Further, the image signal output from the AGC amplifier 19a is supplied to sample and hold circuits 21 and 22 forming a chroma processing section. Sample hold circuit 2
1 and 22 are supplied with sampling pulses SHP1 and SHP2 (shown in E and F in FIG. 5 and FIG. 6) from the timing generator 14.

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

The subtracter 23 subtracts the signal S1 from the signal S2. Therefore, the subtracter 23 outputs a red difference signal R-Y and a blue difference signal -(B-Y) alternately in a line-sequential manner (as 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 is also supplied to a delay circuit having a delay time of one horizontal period. The signal is supplied to the a-side fixed terminal of the change-over switch 24 and the b-side fixed terminal of the change-over switch 25 via the changeover switch 26 .

Switching of the changeover switches 24 and 25 is controlled by a controller 27. That is, one horizontal period during which the red difference signal RY is output from the subtracter 23 is b.
On the other hand, one horizontal period during which the blue color difference signal -(B-Y) is output is connected to the a side. Note that the controller 27 is supplied with the synchronization signals HD and VD from the synchronization generator 16 as reference synchronization signals, and is also supplied with the clock CK1 from the timing generator 14.

Since the changeover switches 24 and 25 are changed over as described above, the changeover switch 24 outputs the red difference signal RY in each horizontal period, and the changeover switch 25 outputs the blue difference signal -( B-Y) is output.

The luminance signal Y output from the low-pass filter 20 and the color difference signals (R-Y) and -(B-Y) output from the changeover switches 24 and 25 are supplied to an encoder 28. The encoder 28 is supplied with a composite synchronization signal SYNC, a blanking signal BLK, a burst flag signal BF, and a color subcarrier signal SC from the synchronization generator 16.

In the encoder 28, as is well known, a synchronizing signal SYNC is added to the luminance signal Y, and a color difference signal is subjected to quadrature two-phase modulation to form a carrier color signal C, and a color burst signal is added. . and,
These luminance signal Y and carrier color signal C are added to form, for example, an NTSC color video signal SCV. Color video signal SC output from encoder 28
V is led out to output terminal 29.

Furthermore, the encoder 28 outputs a black-and-white video signal SV (luminance signal Y to which a synchronizing signal SYNC has been added), and this black-and-white video signal SV is supplied to the electronic viewfinder 30 to display an image pickup screen on a small CRT. be done.

A strobe mode setting switch 31 is connected to the controller 27, and by turning on this setting switch 31, the normal mode is changed to the strobe mode. In the strobe mode, when the shutter button 7 (shown in FIG. 1) is pressed and the shutter switch 32 connected to the controller 27 is turned on, the controller 2
A light emission timing pulse PLG is supplied from 7 to the strobe 33, and the strobe 33 is controlled to emit light in the next field.

When the strobe mode is set, a control signal is supplied from the controller 27 to the adder 17c, and the opening of the iris 11 is set to be small, for example, about ⅓. When the opening of the iris 11 becomes smaller, the amount of light incident on the image sensor 12 decreases, and the level of the image signal output from the image sensor 12 decreases. Therefore, the gain of the AGC amplifier 19a is automatically increased by the AGC control loop to compensate for the drop in the level of the imaging signal.

However, even if the opening of the iris 11 is small, when the strobe 33 emits light, the amount of light incident on the image sensor 12 is sufficient, and the level of the image signal output from the image sensor 12 is also increased. At this time, AGC amplifier 1
If the gain of 9a remains raised, the level of the imaging signal may become too high and overexposure may occur. Therefore, in this example, in the next field in which the strobe 33 emits light, that is, in the field in which the image signal captured by the strobe light 33 is output, a control signal is supplied from the controller 27 to the subtractor 19d, and the AGC amplifier The gain of 19a is forcibly lowered.

The level of the control signal is, for example, iris 11.
Level detection circuit 19 when the opening is reduced
b is made equal to the level change of the detection signal SAG. Therefore, the detection signal SAG is supplied to the controller 27,
A level change is detected when the opening of the iris 11 is made smaller.

Furthermore, in the strobe mode, the controller 2 is activated in synchronization with the end of the field in which the strobe 33 emits light.
A take-in pulse PTI is output from 7. This capture pulse PTI is used to capture data for one screen into a still image recorder connected to the output terminal 29 (not shown).

In the above configuration, when the setting switch 31 is turned on (as shown in FIG. 9B), the next vertical synchronization signal V
In synchronization with D, the normal mode changes to the strobe mode (as shown in FIG. 9C). FIG. 9A shows the vertical synchronization signal VD.

When it comes to strobe mode, controller 2
A control signal is supplied from 7 to the adder 17c, and the iris 1
1 is reduced to about 1/3 of the open state (Fig. 9
(Illustrated in D). The example in FIG. 9 shows an example in which the illuminance is low and the iris 11 is open (AGC operation) and the strobe mode is set. Note that the solid line a in FIG. 10 shows the relationship between the illuminance in the normal mode and the output signal of the AGC amplifier 19a. The broken line b in the figure shows the relationship when the iris 11 is open and the gain of the AGC amplifier 19a is fixed at 10 dB.

When the opening of the iris 11 becomes smaller, the amount of light incident on the image sensor 12 decreases.
As a result, the level of the output image signal decreases. Therefore, the control voltage to the AGC amplifier 19a increases, and the AGC amplifier 19a increases.
The gain of the C amplifier 19a is automatically increased (as shown in FIG. 9E) to compensate for the drop in the level of the imaging signal.

In strobe mode, shutter button 7
When is pressed, the shutter switch 32 is turned on, and a light emission timing pulse PLG is supplied from the controller 27 to the strobe 33 (as shown in FIG. 9F), the strobe 33 emits light in the next field F0 (as shown in FIG. 9G). .

A read pulse is supplied from the timing generator 14 to the image sensor 12 at the end of each field (as shown in FIG. 9H). Therefore, the accumulated charge of the image sensor 12 becomes as shown in FIG. 9I. On the other hand, the image signal output from the image sensor 12 is outputted with a delay of one field, as shown in FIG. 9J.

In the field in which the image signal n for one screen captured by firing the strobe 33 in the field FO is output from the image sensor 12, a control signal is supplied from the controller 27 to the subtractor 19d, which causes the AGC amplifier 19a to (as shown in FIG. 9E), and the gain of the AGC amplifier 19a is forcibly lowered. The level of the image signal n captured by firing the strobe 33 is sufficiently high, and the AGC amplifier 1
Forcibly lowering the gain of 9a prevents the level of the imaging signal n from becoming too large.

Furthermore, in synchronization with the end of field F0, the controller 27 outputs a take-in pulse PTI (as shown in FIG. 9K). Therefore, by using this capture pulse PTI, it is possible to capture, for example, one screen worth of image signal n captured by firing the strobe 33 into a still image recorder connected to the output terminal 29 (Fig. 9L (illustrated). The imaging signal n is obtained by imaging under a sufficient amount of light, and is a high-quality imaging signal with a good S/N ratio compared to imaging signals of other fields whose levels are compensated by the AGC amplifier 19a. .

As described above, in this example, by turning on the setting switch 31 to set the strobe mode, the strobe 33 can emit light to take an image. in this case,
In the strobe mode, the opening of the iris 11 is made small, so there is no risk that the accumulated charge in the image sensor 12 will be saturated due to light emission from the strobe 33. Furthermore, since the gain of the AGC amplifier 19a is forcibly lowered in the field where the image signal n captured by firing the strobe 33 is output, the level of the image signal n may become too large and cause overexposure, etc. do not have.

[0057]

[Effects of the Invention] According to this invention, since the opening of the iris is made small in the strobe mode, even when the strobe emits light, a high amount of light is not incident on the image sensor, and the accumulated charge does not become saturated. . Furthermore, since the gain of the AGC circuit is lowered at the output timing of the image signal captured by strobe light emission, there is no possibility that the level of the image signal becomes too high and overexposure occurs.

[Brief explanation of drawings]

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

FIG. 2 is a diagram showing the configuration of a video camera section.

FIG. 3 is a schematic diagram of color coding.

FIG. 4 is a diagram showing the 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 the configuration of a zoom driver.

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

FIG. 9 is a diagram showing the operation in strobe mode.

FIG. 10 is a diagram showing the relationship between illuminance and the output of the AGC amplifier (normal mode).

[Explanation of symbols]

1 Cabinet 2, 3 Imaging lens 4 Eye cup 5T, 5W Zoom operation button 6 Record button 7 Shutter button 12 CCD solid-state image sensor 14 Timing generator 16 Synchronous generator 17c Adder 19a AGC amplifier 19d Subtractor 20 Low pass filter 21, 22 Sample and hold circuit 23 Subtractor 24, 25 Selector switch 26 Delay circuit 27 Controller 28 Encoder 29 Output terminal 30 Electronic viewfinder 31 Strobe mode setting switch 32 Shutter switch 33 Strobe

Claims (1)

[Claims] 1. A strobe mode that uses a strobe light emitting means, an iris that controls the amount of light incident on an image sensor, an AGC circuit that controls the level of an image signal output from the image sensor, and the strobe light emitting means. A video camera comprising: a mode setting means; and a control means which, in the strobe mode, reduces the opening of the iris and lowers the gain of the AGC circuit at the output timing of an image signal captured by the strobe light emission.