JPH03135178A - Imaging device - Google Patents

Abstract

PURPOSE:To improve the S/N by sending alternately an S+N signal including noise of an amplifier circuit to a video signal for one field period and an S+N-N signal being the subtraction of a noise for a field period in the absence of the video signal from the S+N signal. CONSTITUTION:After a video signal of a CCD 1 in the intensifying mode is amplified by a preamplifier 3 and an AGC circuit 4, that is, after an S+N signal including the system noise is converted by an A/D converter 5, the converted S+N signal is fed to an A switch SW 6. The resulting signal is stored in a field memory (FM) 8 via a terminal (a) and a memory control (MC) 7 at 1/60sec and simultaneously processed by a D/A converter 11, a CSW 12, a process circuit 13 and an encoder 14 via a terminal (a) of a BSW 10 to be a video signal. No video signal exists at 2/60sec and only a system noise signal is given to a subtraction circuit 9 via a terminal (b), in which the S+N signal stored in the memory FM 8 read via the memory control MC 7 is subtracted by the noise to obtain S+N-N and the video signal is obtained after the similar processing at the 1/60sec. Thus, the signals S+N and S+N-N(=S) are sent alternately to improve the S/N.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an imaging device that performs imaging with increased sensitivity when the illuminance of a subject area is low.

[Prior art and its problems] When photographing a subject using an imaging device, when the illuminance around the subject is low, a countermeasure on the photographing device side is to use a video signal processing system, such as an AGC circuit, to electrically increase the gain. One possible method is to shoot with the camera raised.

However, when attempting to electrically increase the gain of video information using an AGC circuit or the like, there is a problem in that the quality of the image obtained deteriorates because even the internal noise of the imaging element is amplified.

The present invention was made to solve these problems, and it is possible to reduce noise in images even in low illuminance, and to achieve high S.
An object of the present invention is to provide an imaging device capable of transmitting images with a /N ratio.

[Means for Solving the Problems] The present invention stores the output signals of each photoelectric conversion element provided in a CCDWL imager in a charge storage element over one field period or a predetermined field period, and outputs the output signals from the charge storage element at least every l field period. In an imaging device using a CCD imaging device that sends out a signal at least every 1 field period, a video signal sent out from a photoelectric conversion element in 1 field period via a charge sending section and a circuit for amplifying the signal. a subtraction circuit that subtracts an N signal consisting of only noise during a field period in which no video signal is sent out from the charge sending section from the (S+N) signal including t noise generated in the charge sending section; Obtained (S+N)
-N processed signals alternately for every I field.

Further, the present invention provides a solid-state image sensor that converts a captured image into an electrical signal, an amplification unit that amplifies the electrical signal sent out by the solid-state image sensor, and a first contact point when information is sent out from the solid-state image sensor. a first switch connected to the solid-state image sensor and connected to a second contact when no information is transmitted from the solid-state image sensor; a storage section that stores the solid-state image sensor output information sent from the amplification section; a second switch that switches the connection to the third and fourth contacts at the same period as the interval required to form the L field; and when the first switch is connected to the first contact, the first switch The solid-state image sensor sending information sent from the contact is sent to the third contact, and the solid-state image sensor sending information is written to the storage section, and the first switch is connected to the second contact. a storage control section that reads out the stored solid-state imaging device transmission information from the storage section and sends it to the third contact point when the solid-state imaging device transmission information is in the storage section; The electrical noise component in the amplifying section sent out through the second contact is removed, and the second
and a video signal converter that converts the information sent by the second switch into a video signal.

With this configuration, the removal unit removes electrical noise components included in the information transmitted by the solid-state image sensor from the information transmitted by the solid-state image sensor, so that the exposure time of the solid-state image sensor is made longer than usual. Even in the sensitization mode, it works to obtain a display image with less noise.

The second switch switches the third and fourth contacts at the same period as the interval required to form the L field in the display image, and when connected to the third contact, the storage control unit sends The solid-state image sensor output information containing electrical noise components is sent to the next stage video signal converter,
On the other hand, when connected to the fourth contact, the information sent by the removing section, that is, the solid-state imaging probe sending information from which electrical noise components have been removed, is sent to the video signal converting section. Therefore,
Even in a sensitization mode in which the exposure time of the solid-state image sensor is longer than usual, it works to obtain a display image with less noise.

Further, the present invention provides a solid-state image sensor that converts a captured image into an electrical signal, an amplification unit that amplifies the electrical signal sent out by the solid-state image sensor, and a first contact point when information is sent out from the solid-state image sensor. a switch connected to the solid-state image sensor and connected to a second contact when information is not transmitted from the solid-state image sensor; and a first switch that stores the solid-state image sensor sending information sent from the amplifying section via the first contact. a second storage section that stores an electrical noise component sent from the amplification section via the second contact; The solid-state image sensor sending information supplied from the contact is sent out, and the solid-state image sensor sending information is written to the first storage section, and when the switch is connected to the second contact, the stored solid-state image sensor is written. a first storage control section that reads and sends out transmission information from the first storage section; and when the switch is connected to a second contact, sends out an electrical noise component supplied from the second contact; A second storage unit that writes the electrical noise component into the second storage unit, and reads out and sends out the stored electrical noise component from the second storage unit when the switch is connected to the first contact. a storage control section; a removal section that removes an electrical noise component sent from the second storage control section from the solid-state image sensor sending information sent out from the first storage control section; A video signal converter that converts information into a video signal.

Furthermore, with this configuration, when the switch is connected to the first contact, the removal unit is supplied with the solid-state image pickup device sending information containing electrical noise components from the first storage control unit, and as a countermeasure. Since the electrical noise component stored in the second storage section is read out and supplied from the second storage control section, the removal section reads out the electrical noise component stored in the second storage section. The electrical noise component supplied from the second storage control unit is subtracted from the attached solid-state image sensor output information, and the solid-state image sensor output information without the electrical noise component is sent to the next-stage video signal converter.

When the switch is connected to the second contact, the solid-state image sensor sending information containing electrical noise components stored in the first storage unit is read out from the first storage control unit to the removal unit. Since the electrical noise component is supplied from the storage control section of the second solution, the removal section extracts the electrical noise component-attached solid-state image pickup device output information supplied from the first storage control section. By subtracting the electrical noise component supplied from the storage control section No. 2, the solid-state image sensor sending information without electrical noise components is sent to the next-stage video signal converting section. Therefore,
The removing unit operates to transmit information to the solid-state image sensor without electrical noise components, regardless of whether the contact of the switch is connected to the first or second contact.

[Embodiment] In FIG. 1 showing an embodiment of the imaging device of the present invention, a CG
A CCD driver circuit 2 is connected which sends out a signal that controls the timing at which the DI sends out a video signal. ccpi
is used as a normal mode when the illuminance of the subject is sufficient.
/ Sends video information shot every 60 seconds, and when the illuminance of the subject is insufficient, the exposure time is doubled as in the normal mode as shown in Figure 3C as a sensitization mode, and images are taken every 1/30 seconds. This transmits video information that has been captured.

In addition, even in the sensitization mode, a signal is sent out from the CCD 1 every 1/60 seconds, but a signal including a video signal is sent out every 1/30 seconds. The reason why the signal is sent from the CCDI every 1760 seconds is to create a video signal that consists of two fields that constitute one frame, that is, one image.

Further, the exposure time in the sensitization mode is not limited to the above time.

The output side of the CCD 1 is connected to an analog/digital (hereinafter referred to as A/D) converter 5 via a preamplifier 3 that amplifies the video signal to be sent out and an AGC circuit 4.
The output side of is connected to the input terminal of the A switch 6. or,
The output side of the AGC circuit 4 is b of the C switch 12, which will be described later.
Connected to the side terminal.

The A switch 6 is a switch that selects either the a side terminal or the b I11 terminal according to the field discrimination pulse sent by the timing generator 15 for each -field when two fields constitute one frame, that is, one image. The a side terminal of the A switch 6 is connected via a memory control 7 to a field memory 8 which is a semiconductor memory and stores the digitally converted video signal, and the b side terminal of the A switch 6 is connected to a subtraction circuit 9. Connected. Therefore, the A switch 6 sends the video signal digitally converted by the A/D converter 5 to the memory control 7 every other field, and the memory control 7 receives the video signal using the timing signal sent by the timing generator 15. It is stored in the field memory 8.

The output side of the memory control 7 is connected to the a side terminal of the B switch IO and the input side of the subtraction circuit 9.
The output side of the subtraction circuit 9 is connected to the b side terminal of 0, and the output side of the B switch IO is connected to the digital/analog (hereinafter referred to as D/A
) is connected to the a side terminal of the C switch 12 via the converter 11.

The subtraction circuit 9 uses the video signal of the current field supplied from the A/D converter 5 via the b side terminal of the A switch 6 from the video signal of the previous field supplied from the field memory 8 via the memory control 7. This is a circuit that subtracts signals.

Like the A switch 6, the B switch 10 is a switch that can be switched to either the a side terminal or the b side terminal by a timing signal sent by the timing generator 15, and the A switch 6 is switched to the a side terminal. At times, the B switch IO is also switched to the a-side terminal, and when the A switch 6 is switched to the b-side terminal, the B switch IO is also switched to the b-side terminal.

The C switch 12 is a changeover switch (not shown) that selects whether the video signal in the CCDI is sent out every 1/60 seconds in the normal mode or every 1/30 seconds in the enhanced mode. This is a switch that selects either the a-side terminal or the b-side terminal in response to a switching signal, and switches to the b-side terminal in the normal mode and to the a-side terminal in the sensitization mode.

The output side of the C switch 12 is connected to a video signal output terminal 16 via a process circuit 13 for converting a video signal into a video signal and an encoder I4.

The operation of the imaging apparatus configured as described above will be explained below with reference to FIGS. 1 and 3.

First, when the illuminance around the subject is bright enough to photograph, that is, when photographing in normal mode, the captured image is converted into an electrical signal by the CCDI, and the converted electrical signal is The video signal becomes 1/60 seconds per timing signal sent by the COD driver circuit 2 every 1/60 seconds
It is sent to the preamplifier 3 every 60 seconds.

The video signal consisting of the electrical signal sent out from the CCDI is
Preamplifier 3. The signal is amplified by the AGC circuit 4 and sent to the A/D converter 5 and the b-side terminal of the C switch 12. Furthermore, A
The video signal sent from the GC circuit 4 is
Contains noise components such as fixed pattern noise generated up to GC circuit 4. Such noise components are not noticeable in the displayed image in normal mode with short exposure time, but become noticeable in enhanced mode. be.

In the normal mode, the contact of the C switch 12 is switched to the b-side terminal, so the video signal sent from the AGC circuit 4 is sent to the process circuit 13 via the b-side terminal of the C switch 12. The signal is processed by the encoder 14, converted into a video signal, and sent to the video signal output terminal 16. Therefore, in the normal mode, a video signal sent from the CGDI every 1/60 seconds is sent to the video signal output terminal 16 as a video signal every 1/60 seconds. Further, in the video signal sent from the video signal output terminal 16, one field is formed every 1760 seconds, and two fields constitute one image. Note that, as described above, the video signal does not have noticeable noise components even when displayed on a screen.

Next, if the illuminance around the subject is insufficient for photographing in the normal mode, photographing is performed in the enhanced mode. Note that switching between the normal mode and the sensitized mode may be performed by a signal sent from a well-known circuit provided with an optical sensor, or may be switched by an operator.

In the sensitization mode, the exposure time of the CCDI is 1/30 seconds, which is twice as long as 1/60 seconds, and the CCDI exposure time is 1/30 seconds, which is twice as long as 1/60 seconds.
At D1, the charge of the photographed image is accumulated for 1/30 seconds, and the illuminance of the subject is ensured even in an environment with insufficient illuminance. The video signal with guaranteed illuminance is sent out from the CGDI every 1/30 seconds according to the timing signal sent out by the COD driver circuit 2, and is sent out from the preamplifier 3. AGC
Amplified by circuit 4 and sent to A/D converter 5 and C switch 1
It is sent to the b-side terminal of 2. However, since the contact point of the C switch 12 is switched to the a side terminal because it is in the sensitization mode, the video signal sent from the AGC circuit 4 is digitally converted by the A/D converter 5 and sent to the A switch 6. Supplied.

The A switch 6 has a timing generator 15 of 1/6
According to the field discrimination pulse signal 30 shown in Fig. 3e, which is sent out every 0 seconds, the contact is switched to the a side or b side terminal at 1/60 seconds, so first, the 8 side terminal is switched at the first I/60 second. When connected to the A/D converter 5, the video signal sent from the A/D converter 5 is supplied to the memory control 7.

The memory control 7 stores the supplied video signal in the field memory 8 according to the timing signal sent out by the timing generator 15, and sends it out as it is to the a-side terminal of the B switch IO.

Incidentally, as shown in FIG. 3d, the video signal 31 stored in the field memory 8 and sent to the B switch 10 is supplied with the preamplifier 3. A noise component 32 in the AGC circuit 4 is included.

At this 1/60 second, the contact point of B switch lO is a
Since it is connected to the side terminal, the video signal 31 containing the noise component 32 is sent out via the memory control 7.
is connected to the D/A converter 1 via the a side terminal of the B switch 10.
1, is converted into analog by the D/A converter ti, and is sent to the C switch 12. Since the C switch 12 is in the sensitization mode, the contact point of the C switch 12 is connected to the a side terminal, and the video signal 31 containing the noise component 32 supplied to the C switch 12 is sent to the process circuit 13. Signal processing is performed in the encoder 14, and as shown in FIG.
Video signal output terminal 16 as a video signal 34 containing 2
sent to.

Next, 1/60 seconds have elapsed, and at 2/60 seconds, the next field discrimination pulse signal is supplied to the A switch 6.
The contact point of the A switch 6 is switched to the b side terminal. However, since it is in the sensitization mode, a video signal is sent out from the CCDI every 1/30 seconds, and no video signal is sent out from the CCDI at 2/60 seconds. Therefore, the A switch 6 has a preamplifier 3. as shown in FIG. 3d.
Only the noise component 32 in the AGC circuit 4 is supplied,
The supplied noise component 32 is sent to the subtraction circuit 9 via the b-side terminal.

Also, at the 2/60th second, the memory control 7 is 1/6
The video signal 31 containing the noise component 32 stored at second 0 is read out from the field memory 8 and sent to the subtraction circuit 9.

Therefore, the subtraction circuit 9 receives the signal sent from the A/D converter 5 from the video signal 31 containing the noise component 32 at the 1/60th second sent from the memory control 7 at the 2/60th second. The noise component 32 is subtracted and only the video signal 31 is sent to the b-side terminal of the B switch 10. At the 2/60th second, the contact of the B switch IO has been switched to the b side, so the video signal 31 sent from the subtraction circuit 9 is sent to the D/A converter 11 via the b side terminal of the B switch 10. The signal is converted into an analog signal and sent to the a-side terminal of the C switch 12. Since the contact of the C switch 12 has been switched to the a side terminal, the video signal 31 is sent to the process circuit 13.
．． The signal is sent via the encoder 14 to the video signal output terminal I6 as a video signal 35 containing no noise components.

At the next 3/60th second, the contacts of the A switch 6 and the B switch 10 are switched to the a side terminal again by the field discrimination pulse signal 30 sent out by the timing generator 15, so that An action similar to the one shown in the figure is performed. Therefore, at the 3/60th second, the video signal 3 is again made up of the noise component bone video signal.
6 is sent to the video signal output terminal 16.

At the next 4/60th second, a video signal consisting only of the video signal is sent to the video signal output terminal I6 in the same manner as the operation at the 2/60th second.

When the video signal supplied to the video signal output terminal 16 is displayed on a screen, an image for one field is created every 1/60 seconds, and one image is formed by two fields.

In this way, in the imaging apparatus of this embodiment, in the sensitization mode, a video signal containing a noise component for each -field,
A video signal that does not contain noise components is sent out alternately, and -
Since a video signal containing no noise components can be obtained for each field, a display image with less noise can be obtained even in the sensitization mode.

The second embodiment is an imaging device in which only a video signal containing no noise components is obtained in the sensitization mode, and only the range that differs from the constituent parts of the imaging device in the above embodiment is shown in FIG. Also, the same components as those in FIG. 1 are not shown, and their explanation will be omitted. Also, in the structural parts shown in FIG. 2, the same reference numerals are given to the same structural parts as in FIG. 1, and the explanation thereof will be omitted.

The b side terminal of the A switch 6 is connected to the timing generator 1.
The output side of 5 is connected to a memory control 7', and the output side of memory control 7° is connected to a subtraction circuit 9. Similarly to the memory control 7, the memory control 7° controls the noise component supplied from the A/D converter 5 via the b side terminal of the A switch 6 to the memory control 7° according to the timing signal sent by the timing generator 15. Connected field memory 8
This circuit stores the noise component in the subtraction circuit 9 and sends the noise component as it is to the subtraction circuit 9.

Further, the output side of the memory control 7 is connected to a subtraction circuit 9, and the output side of the subtraction circuit 9 is connected to a D/A converter 11. The D/A converter 11 is connected to a C switch 12.

The operation of the imaging device configured in this manner will be described below. The operations of the CCD 1, A switch 6, C switch 12, etc. in the sensitization mode are the same as those in the above embodiment, and the explanation thereof will be omitted.

In the sensitization mode, at the first 1/60 seconds, the contact point of the second switch 6 is switched to the a-side terminal by the field discrimination pulse signal sent by the timing generator 15, and the contact point of the second switch 6 is switched to the a side terminal by the field discrimination pulse signal sent by the timing generator 15. A video signal 31 containing a noise component 32 is stored in a field memory 8 via a memory control 7, and is also sent from the memory control 7 to a subtraction circuit 9. Since the signal to be subtracted by the subtraction circuit 9 is not supplied to the first 1/60 grain, the video signal 31 containing the noise component 32 supplied from the memory control 7 to the subtraction circuit 9 is transferred to the D/A converter It. sent to.

Next, at 2/60 seconds, the contact point of the A switch 6 is switched to the b side terminal by the field discrimination pulse signal sent from the timing generator 15, and the A/D converter 5 sends out the signal as in the above embodiment. A signal containing only the noise component 32 is sent to the memory control 7° via the b-side terminal of the A switch 6. The memory control 7' causes the signal containing only the noise component 32 to be stored in the field memory 8' according to the signal sent from the timing generator 15, and also sends it to the subtraction circuit 9.

Also, at this time, the memory control 7 stores the noise component 32 stored at 1/60 second from the field memory 8.
The video signal 31 containing the above is read out and sent to the subtraction circuit 9.

Therefore, the subtraction circuit 9 subtracts the signal of the noise component 32 supplied via the b-side terminal of the A switch 6 and the memory control 7° from the video signal 31 containing the noise component 32 sent out from the memory control 7. . Therefore, 2
At the /60th second, the subtraction circuit 9 sends only the video signal 31 to the D/A converter 11, so as shown in FIG. A video signal 37 consisting only of

Next, at the 3760th second, the contact point of the A switch 6 is switched to the a side terminal again by the field discrimination pulse signal sent out by the timing generator 15, and the A/D
A video signal 31 containing a noise component 32 sent from the converter 5 is sent to the memory control 7 via the a-side terminal. The memory control 7 stores the supplied signal in the field memory 8 and sends it to the subtraction circuit 9. On the other hand, at this time, the memory control 7° is also 2/
At the 60th second, the signal of the noise component 32 stored in the field memory 8' is read out and sent to the subtraction circuit 9.

Therefore, the subtraction circuit 9 subtracts the signal of the noise component 32 supplied from the memory control 7° from the video signal 31 containing the noise component 32 supplied via the a side terminal of the A switch 6 and the memory control 7. , only the resulting video signal 31 is sent to the D/A converter 11. Therefore, even at the 3/60th second time, as shown in FIG. 4, the video signal 38 consisting only of the video signal 31 without noise components is supplied to the video signal output terminal 16.

Similarly, according to this embodiment, a video signal containing no noise components can be obtained in any field. Therefore, an image free of noise can be displayed even when displayed on the screen in the sensitization mode.

[Effects of the Invention] As detailed above, according to the present invention, the removal section can remove the electrical noise component that occurs when the information sent out by the solid-state image sensor is amplified, so that Also, it is possible to provide an imaging device capable of transmitting an image with little noise in the image and a high S/N ratio.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a first embodiment of the imaging device of the present invention, FIG. 2 is a block diagram showing the configuration of the second embodiment of the imaging device of the present invention, and FIG. 4 is a time chart showing the operation of the imaging device shown in FIG. 2. FIG. 4 is a time chart showing the operation of the imaging device shown in FIG. 1...CCD, 6...A switch, 7.7''...
Memory control, 8.8゛...Field memory, 9...Subtraction circuit, lO...B switch, 12...C switch.

Claims (3)

[Claims] (1) The output signal of each photoelectric conversion element included in the CCD imaging device is stored in a charge storage element over one field period or a predetermined field period, and a signal is sent out from the charge storage element at least every other field period. In an imaging device using a CCD imaging device, the image signal includes a video signal sent out in one field period from a photoelectric conversion element via a charge sending unit and noise generated in a circuit for amplifying the signal (S+N ) signal, a subtraction circuit that subtracts an N signal consisting only of noise during a field period in which no video signal is sent from the charge sending section; and (S+N) obtained from the above (S+N) signal and the subtraction circuit.
-N processed signals alternately at every other field. (2) A solid-state image sensor that converts a photographed image into an electrical signal, an amplification section that amplifies the electrical signal sent out by the solid-state image sensor, and connected to the first contact when information is sent out from the solid-state image sensor. a first switch that is connected to a second contact when information is not transmitted from the solid-state image sensor; a storage section that stores the solid-state image sensor output information that is sent from the amplification section; and one field in a display image. a second switch that switches the connection to the third and fourth contacts at the same period as the interval required to form the first contact; and when the first switch is connected to the first contact, the first contact Sends the solid-state image sensor sending information sent from the above to the third contact and writes the solid-state image sensor sending information to the storage section, and when the first switch is connected to the second contact, a storage control unit that reads out the stored solid-state image sensor sending information from the storage unit and sends it to the third contact; and a second contact of the first switch from the solid-state image sensor sending information sent from the storage control unit. The electrical noise component in the amplification section sent out through the second
An imaging device comprising: a removal section that sends out information to a fourth contact of the switch; and a video signal conversion section that converts information sent out from the second switch into a video signal. (3) A solid-state image sensor that converts a photographed image into an electrical signal, an amplification section that amplifies the electrical signal sent out by the solid-state image sensor, and connected to the first contact when information is sent out from the solid-state image sensor. a switch that is connected to a second contact when information is not transmitted from the solid-state image sensor, and a first memory that stores solid-state image sensor output information that is sent from the amplification section via the first contact. a second storage section that stores electrical noise components sent from the amplification section via the second contact; The supplied solid-state image sensor sending information is sent and the solid-state image sensor sending information is written to the first storage section, and when the switch is connected to the second contact, the stored solid-state image sensor sending information is written. a first storage control section that reads out and sends out the electrical noise component from the first storage section; and when the switch is connected to the second contact, sends out the electrical noise component supplied from the second contact; a second storage control for writing the electrical noise component into the second storage section, and reading and transmitting the stored electrical noise component from the second storage section when the switch is connected to the first contact; a removing unit that removes an electrical noise component sent from the second storage control unit from the solid-state image sensor sending information sent from the first storage control unit; An imaging device comprising: a video signal converter that converts into a video signal.