JPH06261248A - Video camera - Google Patents

Abstract

PURPOSE:To set the auto gain control operation range of an auto gain control circuit corresponding to the switching changed amount of exposure time. CONSTITUTION:An exposure time control circuit 1 sets exposure time by a manual operation or detects the illuminance of an object by a CCD output signal d1 and sets exposure time based on this detection result, and supplies an exposure time control signal a1 showing how many fields exposure time is to a CCD driving circuit 2, a signal processing circuit 3 and an AGC operation range setting circuit 8. The AGC operation range setting circuit 8 supplies voltage to set the auto gain control operation range on an AGC circuit 7 based on the exposure time control signal a1. Thus, the auto gain control operation range of the AGC circuit 1 corresponding to the switching changed amount of exposure time can be set.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video camera for taking an image by changing the exposure time, and more particularly to a video camera capable of preventing hunting when the exposure time is changed.

[0002]

2. Description of the Related Art Conventionally, in a single-chip video camera, a CCD (Charge Coupling) is generally used as a solid-state image sensor.
led device) is used to perform sampling and holding on the video signal obtained by photoelectrically converting the video for each field.
A video signal is obtained by processing the sampled and held signal as an analog signal. As such a video camera, a camera that performs high-sensitivity operation by long-time exposure has been put into practical use when capturing an image in a low light amount state such as at night.

FIG. 2 is a block diagram showing such a conventional video camera.

In FIG. 2, reference numeral 51 is an exposure time control circuit for performing control for switching the exposure time. The exposure time control circuit 51 sets the exposure time manually or a CCD from a CCD 54 described later. The illuminance is detected by the output signal d2, the exposure time is set based on the detection result, and the CCD drive circuit 5 outputs the exposure time control signal a2 indicating how many fields the exposure time is.
2 and the signal processing circuit 53. CCD drive circuit 5
2, the vertical drive pulse b2 from the input terminal 60 is also supplied, and the horizontal transfer pulse, the vertical transfer pulse, and the exposure time setting field shift pulse c2 are created based on the exposure time control signal a2 and the vertical drive pulse b2. And supply it to the CCD 54.

A lens 55 is provided on the front side of the CCD 54, and the imaging light passing through the lens 55 is the CCD 54.
Image on. The CCD 54 is driven by the horizontal transfer pulse, the vertical transfer pulse, and the field shift pulse c2 from the CCD drive circuit 52, so that a C having an exposure signal for each field to which the field shift pulse c2 is input.
The CD output signal d2 is sampled and held and the memory circuit 5
Supply to 6. Sample and hold and memory circuit 56
Generates a sample hold signal by sampling and holding the CCD output signal d2, stores the sample hold signal of the field having the exposure signal, and stores the field not having the exposure signal in the stored sample hold signal of the field. An auto gain control circuit (hereinafter referred to as an AGC circuit) 5 as a sample hold signal e2 that has been interpolated and field interpolated.
Supply to 7.

The AGC circuit 57 has its AGC operating range set by the voltage V0 from the AGC operating range setting circuit 58. The AGC operation range setting circuit 58 connects the voltage dividing resistors Ra and Rb in series between the bias wiring to which the reference voltage Va2 is supplied from the DC voltage source and the reference potential point, and connects the voltage dividing resistors Ra and Rb. The voltage V0 is derived from the connection point. The AGC circuit 57 adjusts the gain of the sample and hold signal e2 from the sample and hold and memory circuit 56 in the AGC operation range set in this way to suppress the level fluctuation and supply it to the signal processing circuit 53 as the sample and hold signal f2. To do. The signal processing circuit 53 performs analog signal processing on the sample hold signal f2 based on the exposure time control signal a2 from the exposure time control circuit 51 to generate a video signal g2 and output it to the video signal output terminal 59. Lead. The video signal g2 guided to the video signal output terminal 59 is supplied to a video device such as a video tape recorder or a television receiver connected to the video signal output terminal 59.

FIG. 3 is a block diagram for explaining the CCD 54 of FIG. 2 in more detail.

In FIG. 3, the CCD 54 has a form in which photoelectric conversion units 61 corresponding to pixels arranged in the vertical direction and vertical transfer units 62 are arranged alternately in the horizontal direction. The signal charge accumulated in the photoelectric conversion unit 61 is transferred to the vertical transfer unit 62 by the field shift pulse, and the charge transferred to the vertical transfer unit 62 is horizontally transferred for each horizontal line by supplying the vertical transfer pulse. The charges transferred to the unit 63 and transferred to the horizontal transfer unit 63 are supplied to the charge detection unit 64 by being supplied with the horizontal transfer pulse. The charge detection unit 64 creates an exposure signal by detecting the signal charge from the horizontal transfer unit 63, and supplies this exposure signal to the sample hold and memory circuit 56 as a CCD output signal d2.

FIG. 4 is a timing chart for explaining the long-time exposure operation of such a conventional video camera by taking the case where the exposure time is 4 fields as an example. FIG. 4A shows the vertical drive pulse b2. 4B shows the field shift pulse c2, and FIG. 4C shows the CCD output signal d2.

When performing a long-time exposure operation with an exposure time of 4 fields, the exposure time control circuit 51 outputs an exposure time control signal a2 indicating that the exposure time is 4 fields to the CCD drive circuit 52 and the signal processing circuit. Supply to 53. The CCD drive circuit 52 uses the exposure time control signal a2
And a horizontal transfer pulse, a vertical transfer pulse, and an exposure time setting field shift pulse c2 having a period of 4 fields shown in FIG. 4B are created from the vertical drive pulse b2 having a period of 1 field shown in FIG. 4A. Is supplied to the CCD 54.

The signal charge accumulated in the photoelectric conversion portion 61 is
It is transferred to the vertical transfer unit 62 every four fields by the field shift pulse c2. The charges transferred to the vertical transfer unit 62 are transferred to the horizontal transfer unit 63 by the supply of the vertical transfer pulse, and the charges transferred to the horizontal transfer unit 63 are the horizontal transfer pulse synchronized with the vertical drive pulse b2. It is supplied to the charge detection unit 64 by being supplied, and is supplied from the charge detection unit 64 to the sample hold and memory circuit 56 as the CCD output signal d2. In this case, the CCD output signal d2 is, as shown in FIG.
In the period T1 of the field to which the field shift pulse c2 is supplied, the exposure signal is provided, but in the period T2 in which the field shift pulse c2 is not supplied, the vertical and horizontal transfer pulses are supplied to the CCD 54, but the charges from the pixels are vertically transferred. Since it has not been transferred to the unit 62, the field has no exposure signal.

The sample and hold and memory circuit 56 is
By sampling and holding the CCD output signal d2, a sample and hold signal is created, and a sample and hold signal in a period T1 with an exposure signal is stored and stored in a field in a period T2 without an exposure signal. AGC is performed as a sample hold signal e2 by interpolating with the sample hold signal of the field in the period T1.
Supply to the circuit 57. The AGC circuit 57 uses the voltage V0 from the AGC operation range setting circuit 58 to set the AGC.
Within the operating range, the gain of the sample hold signal e2 is adjusted to suppress the level fluctuation and supplied to the signal processing circuit 53 as the sample hold signal f2. The signal processing circuit 53
A video signal g2 is created from the sample hold signal f2 and is guided to the video signal output terminal 59. As a result, the video signal with the exposure time of 4 fields is stabilized by the AGC circuit 57 as the video signal g2 and is output from the video signal output terminal 59 while switching the video by 4 fields.

When a normal exposure operation is performed, the exposure time control circuit 51 outputs an exposure time control signal a2 indicating that the exposure time is one field to the CCD drive circuit 5.
2 and the signal processing circuit 53. CCD drive circuit 5
2 is a horizontal transfer pulse, a vertical transfer pulse, and a field shift pulse c2 for exposure time setting with a cycle of 1 field.
Is prepared and supplied to the CCD 54. Then, the CCD output signal d2 has an exposure signal in all fields. As a result, the video signal of the video having the exposure time of one field is output from the video signal output terminal 59 as the video signal g2 while being stabilized by the AGC circuit 57 and the video is switched one field at a time. Become.

According to such a conventional video camera,
When capturing an image in a low light amount state such as at night, high-quality images can be obtained by long-time exposure. However,
In the case where the exposure time is automatically switched according to the light quantity of the subject to be imaged, the change rate of the sample hold signal e2 greatly differs between the switching in the relatively short exposure time and the switching in the long exposure time. To explain this in detail, when switching is performed in a relatively short exposure time, for example, switching from 2 fields to 3 fields, the signal amount of the sample hold signal e2 is 3/2 =
1.5 times, switching in a relatively long exposure time,
For example, when switching from 14 fields to 15 fields, the signal amount of the sample hold signal e2 is 15/14.
(About 1.07). As described above, the change amount of the sample hold signal e2 is different between the switching in the short exposure time and the switching in the long exposure time. For this reason, the AGC circuit 57 sets the AGC operation range to 2/1 = 2 times the 1st field to the 2nd field where the amount of change is maximum. In the AGC operation range setting circuit 58, the resistance values of the resistors Ra and Rb are set so that the voltage V0 conforms to such a setting. However, AGC
By setting the AGC operation range of the circuit 57 so wide, hunting occurs when switching is performed for a long exposure time, and the screen is unstable.

[0015]

In the above-mentioned conventional video camera, when the exposure time is automatically switched,
For the automatic gain control circuit, the AGC operating range is set in correspondence with the switching in the shortest exposure time at which the amount of change is the maximum, so hunting occurs when switching over a long exposure time. The screen was unstable.

Therefore, it is an object of the present invention to provide a video camera capable of setting the automatic gain control operation range of the automatic gain control circuit in accordance with the amount of change in exposure time switching.

[0017]

According to the video camera of the present invention, the charge of the photoelectric conversion portion is accumulated in the field to which the field shift pulse is not supplied, and is accumulated in the photoelectric conversion portion in the field to which the field shift pulse is supplied. The solid-state imaging device that transfers the generated signal charges to the charge detection unit and outputs the signal charges as an output signal by the charge detection unit, the lens that forms the image of the subject on the photoelectric conversion unit of the solid-state imaging device, and the exposure An exposure time control circuit for setting a time, a solid-state image sensor drive circuit for supplying a field shift pulse whose period is set based on the setting of the exposure time control circuit to the solid-state image sensor, and an output signal from the solid-state image sensor Of the sample and hold circuit that performs sample and hold of the sample hold signal and outputs the sample and hold signal. The sample-hold signal from the field circuit is interpolated by the interpolating means for interpolating the field not supplied with the field shift pulse by the signal of the field supplied with the field shift pulse, and the interpolating means. An auto gain control circuit that adjusts the gain for the sample hold signal to suppress level fluctuations, and an auto gain that sets the auto gain control operation range of the auto gain control circuit based on the settings of the exposure time control circuit. Control operating range setting means,
And a video signal processing circuit for creating a video signal by performing a predetermined signal processing on the sample hold signal from the auto gain control circuit.

[0018]

According to this structure, the solid-state image pickup device driving circuit supplies the field shift pulse whose period is set based on the setting of the exposure time control circuit to the solid-state image pickup device, whereby the photoelectric conversion of the solid-state image pickup device is performed. The charge accumulation time of the converter is set, and the auto gain control operation range setting means switches and sets the auto gain control operation range of the auto gain control circuit based on the setting of the exposure time control circuit.
The automatic gain control operation range of the automatic gain control circuit can be set according to the amount of change in exposure time switching.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a video camera according to the present invention.

In FIG. 1, the exposure time control circuit 1 sets the exposure time by manual operation, or detects the illuminance of the object by the CCD output signal d1 from the CCD 4, and determines the exposure time based on the detection result. The exposure time control signal a1 indicating the number of fields of the exposure time is set and the CCD drive circuit 2, the signal processing circuit 3 and the AGC are set.
It is supplied to the operating range setting circuit 8. On the other hand, the vertical drive pulse b1 generated by the crystal oscillator is applied to the input terminal 10.
Has been led. The vertical drive pulse b1 guided to the input terminal 10 is supplied to the CCD drive circuit 2. CCD
The drive circuit 2 creates a horizontal transfer pulse, a vertical transfer pulse, and an exposure time setting field shift pulse c1 based on the exposure time control signal a1 and the vertical drive pulse b1 and supplies them to the CCD 4.

A lens 5 is provided on the front side of the CCD 4, and the imaging light of the subject passing through the lens 5 is the CCD 4
Image on. The CCD 4 has the same configuration as the conventional CCD 54 of FIG. 3, and is driven by the horizontal transfer pulse, the vertical transfer pulse, and the field shift pulse c1 from the CCD drive circuit 2 to perform photoelectric conversion of the imaging light,
A CCD output signal d1 having an exposure signal for each field to which the field shift pulse c1 is input is supplied to the sample hold and memory circuit 6. The sample and hold and memory circuit 6 creates a sample and hold signal by sampling and holding the CCD output signal d1, stores the sample and hold signal of the field having the exposure signal, and uses the stored sample and hold signal of the field. By interpolating the field without the exposure signal, the sample hold signal e1 in which the field is interpolated is created and supplied to the AGC circuit 7.

In the AGC operation range setting circuit 8, the voltage dividing resistors Ra1 and Rb1 are connected in series between the bias wiring supplied with the reference voltage Va1 from the DC voltage source and the reference potential point, and the voltage dividing resistors Ra2 and Rb2. Connected in series, voltage dividing resistors Ra3, Rb3 connected in series ... voltage dividing resistors Ran, Rbn
Connected in parallel with each other to connect the voltage dividing resistor Ra
1, Rb1, resistors for voltage division Ra2, Rb2, resistors for voltage division R
a3, Rb3 ... The voltages V1, V2, V3 ... Vn are derived from the respective connection points of the voltage dividing resistors Ran, Rbn. Here, the resistance values Ra1 and Rb1 of the voltage dividing resistors Ra1 and Rb1 are set so that the AGC operating range of the AGC circuit 7 is suitable for switching from 2 fields to 1 field when the voltage V1 is supplied to the AGC circuit 7. ing. Other resistors for voltage division Ra2, Rb2, R for voltage division
a3, Rb3 ... Ran, Rbn have resistance values of voltage V2,
V3 ... Vn is switched from 1 field to 2 fields, 2 fields is switched to 3 fields ...
It is set so as to be suitable for switching from the n-1 field to the n field.

The voltages V1 and V set in this way
2, V3 ... Vn are guided to the first to nth input terminals a1, a2, a3 ... An of the switch 11. Switch 11
The exposure time control circuit 1 is connected to the control signal input terminal of
The exposure time control signal a1 from is derived. Switch 11
Indicates that the exposure time control signal a1 indicates that the exposure time is one field, the first input terminal a1 is selected and connected to the common terminal c, and similarly, the exposure time control signal a1 indicates When the exposure time is 2, 3 ... N fields, the second, third ... Nth input terminals a2, a3 ... An are selected and connected to the common terminal c. As a result, the exposure time indicated by the exposure time control signal a1 is 1, 2,
.. n fields are respectively led to the voltages V1, V2, V3 ... Vn. The voltage introduced to the common terminal c of the switch 11 is supplied to the AGC operation range setting circuit 8.

The AGC circuit 7 is operated by the voltage from the common terminal c of the switch 11 of the AGC operation range setting circuit 8
C operation range is set. The AGC circuit 7 adjusts the gain of the sample and hold and sample and hold signal e1 from the memory circuit 6 within the AGC operation range set in this way to suppress the level fluctuation and supply it to the signal processing circuit 3 as the sample and hold signal f1. To do. The signal processing circuit 3 performs analog signal processing on the sample hold signal f1 based on the exposure time control signal a1 from the exposure time control circuit 1 to obtain a video signal g.
1 is created and led to the video signal output terminal 9. The video signal g1 guided to the video signal output terminal 9 is supplied to the video equipment connected to the video signal output terminal 9.

The operation of automatically switching the exposure time in such an embodiment will be described.

First, when the exposure time is one field, the exposure time control circuit 1 outputs the exposure time control signal a1 indicating that the exposure time is one field to the CCD.
The signal is supplied to the drive circuit 2, the signal processing circuit 3, and the AGC operation range setting circuit 8. The CCD drive circuit 2 uses a horizontal transfer pulse,
An exposure time setting field shift pulse c1 having a vertical transfer pulse and a cycle of 1 field is created and supplied to the CCD 4. Then, the CCD output signal d1 has exposure signals in all fields. In this state, the sample and hold and memory circuit 6 outputs the CCD output signal d1.
A sample hold signal e1 is generated from the above and supplied to the AGC circuit 7. On the other hand, the AGC operation range setting circuit 8 supplies the voltage V1 to the AGC circuit 7 because the switch 11 selects the first input terminal a1. The AGC circuit 7 is an AG set by the voltage V1 from the AGC operation range setting circuit 8.
In the C operation range, the gain of the sample hold signal e1 is adjusted to suppress the level fluctuation and supplied to the signal processing circuit 3 as the sample hold signal f1. As a result, the video signal of the video having the exposure time of one field is output from the video signal output terminal 9 as the video signal g1 while being stabilized by the AGC circuit 7 and the video is switched one field at a time. Become.

First, the exposure time is k fields (k = 2,
3 ... n), the exposure time control circuit 1
An exposure time control signal a1 indicating that the exposure time is k fields is supplied to the CCD drive circuit 2 and the signal processing circuit 3. The CCD drive circuit 2 creates a horizontal transfer pulse, a vertical transfer pulse, and an exposure time setting field shift pulse c1 having a period of k fields and supplies the same to the CCD 4. Then, the CCD output signal d1 has an exposure signal for every k fields, but has no exposure signal in the other fields.

The sample and hold and memory circuit 6 is C
A sample hold signal is created from the CD output signal d1, and a field without an exposure signal is interpolated and supplied to the AGC circuit 7 as a sample hold signal e1. On the other hand, in the AGC operating range setting circuit 8, the switch 11 has the kth
Since the input terminal ak of the AGC circuit 7 is selected, the voltage V
supply k. The AGC circuit 7 has an AGC operating range set by the voltage Vk from the AGC operating range setting circuit 8,
The gain of the sample hold signal e1 is adjusted to suppress the level fluctuation and supplied to the signal processing circuit 3 as the sample hold signal f1. As a result, a video signal having an exposure time of k fields is output from the video signal output terminal 9 as the video signal g1 while being stabilized by the AGC circuit 7 and the image is switched for each k field.

Next, the operation when the exposure time is switched will be described.

When the exposure time is switched from the k-1 field to the k field, the signal amount of the sample hold signal e1 becomes k / (k-1) times. On the other hand, since the exposure time control signal a1 indicates the k field, the AGC circuit 7 adjusts the gain of the sample hold signal e1 when the exposure time is switched in the AGC operation range set by the voltage Vk to change the level. Is supplied to the signal processing circuit 3 as a sample hold signal f1.

When the exposure time is switched from the k field to the k-1 field, the signal amount of the sample hold signal e1 becomes (k-1) / k times. On the other hand, since the exposure time control signal a1 indicates the k−1 field, the AGC circuit 7
Adjusts the gain of the sample hold signal e1 when the exposure time is switched in the AGC operation range set by the voltage Vk-1, suppresses the level fluctuation and supplies the sample hold signal f1 to the signal processing circuit 3.

According to such an embodiment, since the automatic gain control operation range can be set in accordance with the amount of change in the exposure time when the exposure time is switched, hunting when the exposure time is switched is performed. This can be prevented, and the screen can be stabilized when the video signal g1 is stored directly or in the VTR and then reproduced and displayed on the screen of the television receiver or the like.

In the embodiment shown in FIG. 1, the AGC operation range setting circuit 8 includes the voltage dividing resistors Ra1, Rb1, Ra2 and Rb.
2, Ra3, Rb3 ... Ran, Rbn and the switch 11 are used to set the voltage to be supplied to the AGC circuit 7. However, as the AGC operation range setting circuit 8, another circuit, for example, a device for setting the voltage by a memory, It is also possible to use one that sets the voltage using a plurality of DC voltage generation sources.

[0035]

As described above, according to the present invention, since the automatic gain control operation range of the automatic gain control circuit can be set in accordance with the change amount of the switching of the exposure time, the exposure time is switched. Hunting can be prevented, and the screen can be stabilized when the video signal is stored directly or in the VTR and then reproduced and displayed on the screen of a television receiver or the like.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a video camera according to the present invention.

FIG. 2 is a block diagram showing a conventional video camera.

3 is a block diagram showing a CCD of the video camera of FIG.

4 is a timing chart explaining the operation of the video camera of FIG.

[Explanation of symbols]

 1 exposure time control circuit 2 CCD drive circuit 3 signal processing circuit 4 CCD 5 lens 6 sample hold and memory circuit 7 AGC circuit 8 AGC operating range setting circuit

Claims (1)

[Claims] 1. The charge of the photoelectric conversion unit is accumulated in the field to which the field shift pulse is not supplied, and the signal charge accumulated in the photoelectric conversion unit in the field to which the field shift pulse is supplied is transferred to the charge detection unit. , A solid-state image sensor for outputting this signal charge as an output signal by a charge detection unit, a lens for forming an image of a subject on a photoelectric conversion unit of the solid-state image sensor, an exposure time control circuit for setting an exposure time, A solid-state image sensor drive circuit that supplies a field shift pulse whose period is set based on the setting of an exposure time control circuit to the solid-state image sensor, and sample-holds an output signal from the solid-state image sensor, and outputs a sample-hold signal. Sample hold circuit and sample hold signal from this sample hold circuit On the other hand, the interpolation means for interpolating the field to which the field shift pulse is not supplied by the signal of the field to which the field shift pulse is supplied, and the gain for the sample hold signal interpolated by this interpolation means An automatic gain control circuit for adjusting the level of the automatic gain control circuit, and an automatic gain control operation range setting means for switching and setting the automatic gain control operation range of the automatic gain control circuit based on the setting of the exposure time control circuit, A video camera, comprising: a video signal processing circuit that creates a video signal by performing predetermined signal processing on a sample hold signal from an auto gain control circuit.