JP2002218320A - Imaging apparatus and its control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus which can produce a video which does not impart incongruity feeling to the user, even when the illuminance of an object is varied abruptly. SOLUTION: When the illuminance of the object is low, a system control microcomputer 7 controls a sensitization circuit 4 to perform sensitization processing and subtracts the amplification factor of the sensitization circuit from the amplification factor of a CDS/AGC circuit 2. Since the total amplification factor can be varied smoothly, a video which does not impart incongruity feeling to user can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus using a solid-state image pickup device, such as a video camera, an in-vehicle camera, and a surveillance camera. The present invention relates to a possible imaging device and a control method thereof.

[0002]

2. Description of the Related Art In recent years, C.P.
CD (Charge Coupled Device) image sensor, CMOS
(Complementary Metal Oxide Semiconductor) Imaging devices such as video cameras, in-vehicle cameras, and surveillance cameras using solid-state imaging devices such as imaging devices have been commercialized and widely used. These imaging devices are used for monitoring the outdoors all day, like a surveillance camera, and are used not only during the daytime but also at night, like a vehicle-mounted camera. Therefore, even in a bright place or a place where there is only a twilight at night, a performance capable of capturing a certain amount of video is required.

[0003] Techniques related to increasing the sensitivity of these imaging devices can be roughly classified into techniques related to optical systems and techniques related to circuit systems. Techniques for increasing the sensitivity of optical systems include those related to optical components such as reducing the aperture (F-number) of a lens and those utilizing infrared illumination. Imaging devices using these technologies have been developed and commercialized. Have been.

[0004] Further, as a technique for increasing the sensitivity of the circuit system, the opening time of the electronic shutter of the solid-state image sensor, that is, the charge accumulation time in the solid-state image sensor is lengthened, and images of a plurality of frames are accumulated in a frame memory or the like. There is a device using a high-sensitivity circuit in which peripheral pixels in the same frame are added, and an imaging device using the high-sensitivity circuit has been developed and commercialized.

[0005] In a technology for increasing the sensitivity of a circuit system,
If a high-sensitivity circuit is used when the illuminance of the subject is high, problems such as a decrease in the frame rate, making it difficult to see the motion of the video, and a decrease in the illuminance of the video due to the occurrence of extra noise occur. Therefore, it is common to operate the sensitivity increasing circuit only when the illuminance of the subject is low. Japanese Unexamined Patent Publication No. 7-16287 relates to these technologies.
No. 4 and Japanese Patent Application Laid-Open No. 5-48961.

The single-chip high-sensitivity color camera device disclosed in Japanese Patent Application Laid-Open No. Hei 7-162874 operates a CCD image sensor in a frame accumulation mode to obtain a high-sensitivity image by extending the charge accumulation time. Becomes possible. The video signal read from the CCD image sensor is stored in two field memories for each field, and the odd lines and the even lines stored in the respective field memories are vertically adjacent two lines in a predetermined order. The video signal is read out and added every time and the video signal processing is performed, so that it is possible to obtain a video signal having the same resolution as that of the field storage mode of normal sensitivity.

The imaging apparatus disclosed in Japanese Patent Application Laid-Open No. 5-48916 combines two temporally adjacent video signals at low illuminance to attenuate noise components. And
Higher sensitivity can be achieved by increasing the gain with a variable gain amplifier by the amount that the noise component is attenuated.

[0008]

However, Japanese Patent Application Laid-Open Nos. Hei 7-162874 and Hei 5-48916 mentioned above disclose the above.
In the invention disclosed in Japanese Patent Application Laid-Open No. H11-279, the sensitizing circuit operates even when the illuminance of the subject changes from a high place to a low place. Because of the addition, there is a problem that the image suddenly becomes bright and gives the user a sense of incongruity.

Conversely, when the illuminance of the subject changes from a low to a high position, the operation of the high-sensitivity circuit stops, but the high-sensitivity circuit added to the video signal at this time. However, since the gain amount is lost, there is a problem that the image suddenly becomes dark and gives a sense of incongruity to the user.

Also, if a bright object is suddenly picked up while the high sensitivity circuit is operating in a place where the illuminance of the object is low, the image cannot be recognized because the image is overexposed. In particular,
If a high-sensitivity circuit that lowers the frame rate is used, the time during which the image cannot be recognized becomes longer, which may be a serious problem in a vehicle-mounted camera or the like, which may affect safety. .

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and a first object of the present invention is to obtain an image that does not cause a user to feel uncomfortable even when the illuminance of a subject changes suddenly. It is an object of the present invention to provide an imaging device and a control method thereof.

A second object of the present invention is to provide an image pickup apparatus and a control method thereof capable of obtaining an image without a sense of incongruity for a user even if the illuminance of the subject changes suddenly, and preventing a decrease in image resolution. It is to provide.

[0013] A third object is that even if the illuminance of the subject changes suddenly, it is possible to obtain an image that is comfortable for the user, and no blurring occurs even when the moving subject is photographed. An object of the present invention is to provide an imaging device and a control method thereof.

[0014]

According to one aspect of the present invention, an image pickup apparatus includes: a solid-state image sensor for converting an image from a subject into a video signal; and an image signal for amplifying a video signal output from the solid-state image sensor. Amplifying means, a converting means for converting the amplified video signal output from the amplifying means into a digital signal, and a high sensitivity means for performing a high sensitivity process on the video signal output from the converting means. When the illuminance of the subject is low, the control unit controls the sensitivity increasing unit to perform the sensitivity increasing process, and controls the amplification factor of the amplifying unit, and processes the video signal output from the sensitivity increasing unit. Process processing means for performing processing.

When the illuminance of the subject is low, the control means
Since the high-sensitivity means performs the high-sensitivity processing and controls the amplification rate of the amplification means, the total amplification rate can be continuously and smoothly changed, so that the user can obtain an image that is not uncomfortable. It becomes possible.

[0016] Preferably, the sensitivity enhancing means integrates video signals of a plurality of frames to enhance the sensitivity.

Therefore, it is possible to obtain an image that does not cause a sense of incongruity to the user, and it is possible to prevent a decrease in the resolution of the image.

[0018] Preferably, the sensitivity increasing means increases the sensitivity by adding a pixel of interest in the video signal and a pixel adjacent to the pixel of interest.

Therefore, it is possible to obtain an image that does not give the user a sense of discomfort, and no blurring or the like occurs even when a moving subject is photographed.

[0020] Preferably, the control means subtracts the gain of the high sensitivity means from the gain of the amplification means when the high sensitivity means starts the high sensitivity processing.

Therefore, it is possible to continuously and smoothly change the total amplification factor.

According to another aspect of the present invention, the imaging device comprises:
A solid-state imaging device that converts an image from a subject into a video signal,
Amplifying means for amplifying a video signal output from the solid-state imaging device; a converting means for converting the amplified video signal output from the amplifying means into a digital signal; and a video signal output from the converting means. Gain control means for amplifying while controlling the amount of gain, high sensitivity means for performing high sensitivity processing on the video signal output from the gain control means, and high sensitivity when the illuminance of the subject is low. Control means for causing the amplification means to perform a high-sensitivity process, causing the gain control means to set the initial gain amount to 1, and causing the gain control means to increase the gain amount as the illuminance of the subject decreases, and Process processing means for performing process processing on the video signal output from the high sensitivity means.

When the illuminance of the subject is low, the control means
Since the sensitivity increasing means performs the sensitivity increasing process, the gain controlling means sets the initial gain to one time, and the gain controlling means increases the gain as the illuminance of the subject decreases, so that the total gain is increased. The amplification factor can be continuously and smoothly changed, and it is possible to obtain an image that does not give a user an uncomfortable feeling.

[0024] Preferably, the sensitivity increasing means increases the sensitivity by integrating video signals of a plurality of frames.

Therefore, it is possible to obtain an image that does not cause a sense of incongruity for the user, and it is possible to prevent the resolution of the image from lowering.

Preferably, when the average luminance level of the video signal of one frame is smaller than the first luminance level, the control means causes the high-sensitivity means to perform the high-sensitivity processing, and the average luminance level is set to the second luminance level. When it is higher than the luminance level, the high-sensitivity means stops the high-sensitivity processing.

Therefore, by setting the optimum values for the first luminance level and the second luminance level, it is possible to obtain an image corresponding to the illuminance of the subject.

[0028] More preferably, the first luminance level and the second luminance level have hysteresis.

Therefore, it is possible to prevent the occurrence of flickering or the like by frequently operating / stopping the high-sensitivity means.

[0030] Preferably, the control means divides one frame into a plurality of areas and measures the brightness level of each area when the sensitivity improving means is operating, and determines that an area having a predetermined brightness level or more is adjacent. When the number is equal to or more than the predetermined number, the operation of the sensitivity increasing means is stopped.

Therefore, even when a high-luminance subject is picked up while the high-sensitivity means is operating, it is possible to prevent problems such as overexposed images.

According to another aspect of the present invention, a solid-state imaging device for converting an image from a subject into a video signal, amplification means for amplifying a video signal output from the solid-state imaging device,
Conversion means for converting the amplified video signal output from the amplification means into a digital signal; sensitivity enhancement means for performing a sensitivity enhancement process on the video signal output from the conversion means; and sensitivity enhancement means A process processing means for performing a process process on a video signal output from the imaging device, wherein when the illuminance of the subject is low, the high sensitivity process is performed by the high sensitivity device. And setting the gain of the amplifying means by subtracting the gain of the high sensitivity means from the gain of the amplifying means.

When the illuminance of the object is low, the sensitivity increasing means performs the sensitivity increasing process, and the gain of the sensitivity increasing means is subtracted from the gain of the amplifying means. It is possible to smoothly change the image, and it is possible to obtain an image that does not give a user an uncomfortable feeling.

According to still another aspect of the present invention, a solid-state imaging device for converting an image from a subject into a video signal, amplification means for amplifying the video signal output from the solid-state imaging device, and amplification means Conversion means for converting the output amplified video signal into a digital signal; amplification rate control means for amplifying the video signal output from the conversion means while controlling the amount of gain; and amplification rate control means. Of an image pickup apparatus including a high-sensitivity unit for performing a high-sensitivity process on a video signal output from the digital camera, and a process processing unit for performing a process process on a video signal output from the high-sensitivity unit. A control method, wherein when the illuminance of the subject is low, the step of causing the sensitivity increasing means to perform the sensitivity increasing process; and, when the sensitivity increasing means starts operating, the initial gain amount of the amplification factor controlling means. Comprising a step of setting the magnification; and gain amount increases in accordance with the illuminance of the subject is low.

When the illuminance of the object is low, the high-sensitivity means performs the high-sensitivity processing, and the gain control means sets the initial gain to one time. Since the amount of gain is increased by the means, the total amplification rate can be continuously and smoothly changed,
It is possible to obtain an image that does not give the user a sense of discomfort.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Practical Embodiment 1) FIG. 1 is a block diagram showing a schematic configuration of an imaging apparatus according to Embodiment 1 of the present invention. This imaging apparatus performs correlated double sampling of a solid-state image element 1 for converting an image of a subject into an electric signal and an electric signal output from the solid-state image element 1, and automatically adjusts the gain of the image pickup apparatus according to the strength of the electric signal. Control CDS
/ AGC (Correlated Double Sampling / Automatic Gai
n Control) circuit 2 and an A / D for converting an analog signal output from the CDS / AGC circuit 2 into a digital signal.
(Analog / Digital) conversion circuit 3, and a high-sensitivity circuit 4 for performing predetermined processing on the digital signal output from the A / D conversion circuit 3 at low illuminance to increase the sensitivity of the video signal;
A video signal processing circuit 5 that performs processing such as signal interpolation, gamma correction, and various types of filtering on the video signal whose sensitivity has been increased by the sensitivity enhancement circuit 4 and outputs a video signal to an external device; It includes a TG circuit 6 that generates and outputs a timing signal, and a system control microcomputer 7 that performs overall control of the imaging device.

The system control microcomputer 7 controls the timing signal output from the TG circuit 6 to control the solid-state image pickup device 1
The optimum luminance level can be obtained by changing the charge accumulation time. Also, the system control microcomputer 7
By controlling the CDS / AGC circuit 2, the gain of the imaging device can be automatically controlled by changing the amplification factor according to the strength of the electric signal output from the solid-state imaging device 1.

FIG. 2 is a block diagram showing a schematic configuration of the high sensitivity circuit 4 of FIG. This high sensitivity circuit 4 has an A /
An integration control circuit 8 for integrating and outputting the video signal converted into a digital signal by the D conversion circuit 3, a counter 9 for counting the number of frames of the video signal integrated by the integration control circuit 8, and an integration control circuit 8 A selector 10 for switching and outputting the integrated video signal data, memories 11 and 12 for storing the video signal data integrated by the integration control circuit 8, and a reading for reading the integrated video signal data from the memory 11 or 12 Circuit 13
A selector 14 for switching the integrated video signal data output from the memories 11 and 12 and outputting the integrated video signal data to the read circuit 13; a limiter 15 for limiting the video signal data read by the read circuit 13; A selector 16 for switching and outputting the video signal output from the conversion circuit 3 and the integrated video signal output from the limiter 15;

The system control microcomputer 7 designates the number of video signal frames to be integrated with respect to the integration control circuit 8.
The integration control circuit 8 integrates the video signals of the designated number of frames while referring to the value of the counter 9. When the integration of the video signal is completed, the integration control circuit 8 switches the selector 10 to store the integrated video signal data in the memory 11 or 1.
Write to 2. When the integration control circuit 8 is writing the integrated video signal data in the memory 11, the reading circuit 1
3 switches the selector 14 to read the integrated video signal data from the other memory 12. Conversely, the integration control circuit 8
Is writing the integrated video signal data to the memory 12, the readout circuit 13 switches the selector 14 to read the integrated video signal data from the other memory 11.

The system control microcomputer 7 measures the brightness of the subject based on the luminance signal level of the video signal, and changes the charge accumulation time of the solid-state image sensor 1 and the signal amplification factor of the CDS / AGC circuit 2 according to the brightness of the subject. Then, control is performed so that the luminance signal level becomes an optimum level. At this time, the charge storage time of the solid-state imaging device 1 and the CDS / AG
When the optimal luminance signal level is obtained by controlling the amplification factor of the C circuit 2, the system control microcomputer 7 determines that the subject is not in low illuminance, and the video signal output from the A / D conversion circuit 3 The selector 16 is switched so as to be input to the video signal processing circuit 5.

If the optimum luminance signal level cannot be obtained even if the charge accumulation time of the solid-state image pickup device 1 and the amplification factor of the CDS / AGC circuit 2 are maximized, the system control microcomputer 7 sets the subject to low illuminance. When it is determined that there is, the high sensitivity circuit 4 is operated, and the selector 16 is switched so that the video signal output from the limiter 15 is input to the video signal processing circuit 5. As the number of frames to be integrated by the integration control circuit 8 is increased, it becomes possible to capture a clearer image at low illuminance, but a subject with fast movement may be blurred. There is a need to.

FIG. 3 is a diagram for explaining the control of the charge accumulation time (amplification rate) of the solid-state imaging device 1. As shown in FIG. 3, the charge accumulation time of the solid-state imaging device 1 is made longer as the brightness of the subject becomes darker. However, if the brightness of the subject is lower than X1, an optimal luminance signal level cannot be obtained only by controlling the charge accumulation time of the solid-state imaging device 1, so that the system control microcomputer 7 controls the amplification of the CDS / AGC circuit 2. Start rate control.

FIG. 4 is a diagram for explaining control of the amplification factor of the CDS / AGC circuit 2. As shown in FIG. 4, even if the brightness of the subject becomes dark, the charge accumulation time of the solid-state imaging device 1 can be controlled to obtain an optimal luminance signal until X1 is reached. / A
The control of the GC circuit 2 is not performed. The amplification factor when the brightness of the subject is X1 is Y1.

When the brightness of the subject is further reduced, X1
If it is darker and brighter than X2, the system control microcomputer 7 gradually increases the gain of the CDS / AGC circuit 2 so as to obtain an optimum luminance signal level. If the brightness of the subject becomes even darker and becomes darker than X2, an optimal brightness signal level cannot be obtained by controlling the amplification factor of the CDS / AGC circuit 2, so that the system control microcomputer 7 has a high level. The control by the sensitivity conversion circuit 4 is started.

FIG. 5 is a diagram for explaining the control of the amplification factor of the high sensitivity circuit 4. As shown in FIG. 5, when the brightness of the subject is higher than X2, the operation of the high-sensitivity circuit 4 is not performed, and the video signal output from the A / D conversion circuit 3 Signal processing circuit 5
Is input to When the brightness of the subject is lower than X2 and higher than X3, the system control microcomputer 7 controls the integration control circuit 8 to integrate the video signals for two frames to increase the sensitivity. The integrated video signal is input to the video signal processing circuit 5 via the selector 16.

Similarly, when the brightness of the subject is darker than X3 and brighter than X4, the system control microcomputer 7 controls the integration control circuit 8 to integrate the video signals for three frames to increase the sensitivity. Do. In FIG. 5, the system control microcomputer 7 performs step-by-step operation according to the luminance signal level.
It performs even the integration of video signals for frames. FIG.
As can be seen from the figure, since the amplification factor of the sensitivity increasing circuit 4 has a stepped shape, when the sensitivity increasing circuit 4 starts operating, the image becomes momentarily bright and the CDS / AGC circuit 2 operates to be optimal. The control is performed so that the luminance signal level becomes high. This phenomenon not only gives the user of the imaging apparatus a sense of incongruity, but also may cause an important scene to be missed when used in a device that is safely involved, such as a vehicle-mounted camera.

In order to prevent this phenomenon, the brightness is set to X2
Similar to the control of the gain of the CDS / AGC circuit 2 in the case of being darker and lighter than X3 (see FIG. 4), sawtooth-shaped gain control is performed. Thus, CDS / AGC
Performing the sawtooth-shaped gain control as the gain control of the circuit 2 lowers the gain of the CDS / AGC circuit 2 than controlling the charge accumulation time of the solid-state imaging device 1 to lower the total gain. Is more advantageous in terms of S / N ratio.

The amplification factors Y2 and Y3 in FIG.
And the amplification factors Y4, Y5, Y6, and Y7 in FIG.

Y3−Y2 = Y4 = Y5−Y4 = Y6−Y5 = Y7−Y6 (1) FIG. 6 shows the charge accumulation time (amplification rate) of the solid-state imaging device 1 and
FIG. 3 is a diagram showing a total amplification ratio of the amplification ratio of the CDS / AGC circuit 2 and the amplification ratio of the sensitivity enhancement circuit 4. FIG.
As can be seen from the figure, since the total amplification factor changes continuously and smoothly, the imaging device according to the present embodiment can obtain a video signal that does not give a user an uncomfortable feeling.

FIG. 7 is a flowchart for explaining the processing procedure of the imaging apparatus according to the first embodiment of the present invention. First, the system control microcomputer 7 outputs the average value Sn (n = 0 to 63) of the luminance signal level of each of a total of 64 regions, which are obtained by dividing one frame horizontally and vertically into eight regions, respectively, from the video signal process circuit 5. ) Is acquired (S1). Then, the system control microcomputer 7 calculates the average luminance level Z in one frame by adding all the average values Sn of the luminance signal levels and dividing by 64, and recognizes the brightness of the subject (S2). This average luminance level Z is represented by the following equation.

Z = (S0 + S1 + S2 +... + S63) ÷ 64 (2) When adding the average value Sn of the luminance signal levels of the respective regions, weighting is performed so that the subject at the center of the frame is mainly measured. May be.

Next, the system control microcomputer 7 determines a brightness level K_ON (hereinafter, referred to as a sensitivity enhancement start level) set in advance to determine the start of the operation of the sensitivity enhancement circuit 4, and an average brightness level. Compare with Z (S3). If the average luminance level Z is equal to or higher than the sensitivity enhancement start level K_ON (S3, No), it is determined that the subject is not low illuminance, and the process returns to step S1 to repeat the subsequent processes.

If the average luminance level Z is smaller than the sensitivity enhancement start level K_ON (S3, Yes), it is determined that the subject has low illuminance, and the sensitivity enhancement circuit 4 starts operation (S4). . And the system control microcomputer 7
Acquires the average value Sn of the luminance signal levels of the 64 regions again after operating the sensitivity increasing circuit 4 (S5).

The system control microcomputer 7 analyzes the average value Sn of the luminance signal level of each area and determines whether or not there is a high luminance area (S6). The high luminance area includes an adjacent area where the luminance level is equal to or higher than the sensitivity release level (a luminance level set in advance to determine whether to stop the operation of the sensitivity increasing circuit 4), and It is assumed that the number of adjacent regions is equal to or greater than the number of regions for which sensitivity enhancement has been canceled (the number of regions set in advance to determine whether to stop the operation of the sensitivity enhancement circuit 4).

If there is a high luminance area (S6, Ye
s), the system control microcomputer 7 stops the operation of the sensitivity increasing circuit 4 (S7), returns to step S1, and repeats the subsequent processing. By this processing, it is possible to prevent a high-luminance object from being picked up in a part of the subject while the sensitivity enhancement circuit 4 is operating, and to prevent the image from being unrecognizable due to overexposure or the like on the screen.

If there is no high luminance area (S6, N
o), the system control microcomputer 7 calculates an average luminance level Z in one frame (S8), and sets a preset luminance level K_OFF (hereinafter referred to as “high sensitivity enhancement”) in order to determine the stop of the operation of the sensitivity enhancement circuit 4. This is called a stop level.)
A comparison is made with the average luminance level Z (S9).

The average luminance level Z is the sensitivity stop level K
If _OFF or less (S9, No), it is determined that the subject has low illuminance, and the process returns to step S5 to repeat the subsequent processes. If the average luminance level Z is greater than the sensitivity stop level K_OFF (S9, Yes), it is determined that the illuminance of the subject has increased, and the operation of the sensitivity enhancement circuit 4 is stopped (S7), and step S1 is performed. Return to and repeat the subsequent processing.

The luminance signal level K_ON for starting the operation of the high sensitivity circuit 4 and the luminance signal level K_OFF for stopping the operation of the high sensitivity circuit 4 have different values, and have the following relationship.

K_ON <K_OFF (3) As described above, the luminance signal level K_ON for starting the operation of the high-sensitivity circuit 4 and the luminance signal level K_OFF for stopping the operation have a hysteresis, so that the video signal Even when the luminance signal level is near K_ON or K_OFF, frequent operation / stop of the high-sensitivity circuit 4 can be prevented, and phenomena such as flicker can be prevented.

As described above, according to the imaging apparatus of the present embodiment, when the illuminance of the subject is reduced and the operation of the sensitivity increasing circuit 4 is started, the gain (amplification) of the CDS / AGC circuit 2 is increased. By subtracting the gain amount (amplification ratio) obtained by the sensitivity increasing circuit 4 from the (ratio), the total gain amount (amplification ratio) changes continuously and smoothly, and the user does not feel uncomfortable. Images can now be obtained.

The high-sensitivity circuit 4 integrates video signals of two or more frames to change the gain (amplification factor) stepwise and changes the gain (amplification factor) of the CDS / AGC circuit 2. As a result, the total gain (amplification factor) changes continuously and smoothly, providing a video that is comfortable for the user and without causing a reduction in the resolution of the video. It became possible to obtain clear images.

If there is an adjacent area whose luminance level is equal to or higher than the sensitivity canceling level and the number of the adjacent areas is equal to or greater than the number of sensitivity canceling areas, the sensitivity increasing circuit 4
Is stopped, it is possible to prevent a problem such as overexposure of an image even when a high-luminance subject is imaged while the high-sensitivity circuit 4 is operating. Was.

Further, the luminance signal level K_ON for starting the operation of the high-sensitivity circuit 4 and the luminance signal level K_OFF for stopping the operation have hysteresis, so that the luminance signal level of the video signal is K_ON or K_ON.
Even when the position is near _OFF, it is possible to prevent the occurrence of a phenomenon such as flicker.

(Embodiment 2) The schematic configuration of an imaging apparatus according to Embodiment 2 of the present invention is the same as that of Embodiment 1 shown in FIG.
Only the configuration and function of the high-sensitivity circuit are different from the schematic configuration of the imaging device in the above. Therefore, detailed description of the same configurations and functions will not be repeated. It is to be noted that a description will be given assuming that the reference numeral of the sensitivity increasing circuit in this embodiment is 4 '.

FIG. 8 is a block diagram showing a schematic configuration of the sensitivity increasing circuit 4 '. This sensitivity increasing circuit 4 'is different from the sensitivity increasing circuit 4 in the first embodiment shown in FIG.
An amplification factor control circuit 17 that controls the amplification of the video signal converted into a digital signal by the A / D conversion circuit 3 includes an A / D converter.
The only difference lies in the point added between the conversion circuit 3 and the integration control circuit 8. Therefore, detailed description of the same configurations and functions will not be repeated.

FIG. 9 is a diagram for explaining the operation of the amplification factor control circuit 17. As shown in FIG. 9, the system control microcomputer 7 switches the number of frames to be integrated by the integration control circuit 8, that is, when the brightness of the subject is X2,
At times X3, X4, X5 and X6, the gain of the gain control circuit 17 is set to one. Then, the system control microcomputer 7 controls the gain control circuit 17 to gradually increase the gain until the gain reaches Y13 as the brightness of the subject becomes darker. Note that the brightness is X2
When it becomes darker, the gain of the CDS / AGC circuit 2 remains unchanged at Y2.

The figure showing the total amplification ratio of the charge accumulation time (amplification ratio) of the solid-state imaging device 1, the amplification ratio of the CDS / AGC circuit 2, and the amplification ratio of the high-sensitivity circuit 4 'is shown. , And FIG. Further, the processing procedure of the imaging device according to the present embodiment is the same as the processing procedure of the imaging device according to Embodiment 1 shown in FIG. 7, and thus detailed description will not be repeated.

As described above, according to the imaging apparatus of the present embodiment, the integration control circuit 8 is controlled to integrate video signals of two or more frames to change the gain (amplification rate) stepwise. And the gain control circuit 17 is controlled to gradually change the gain (amplification factor), so that the total gain (amplification factor) changes continuously and smoothly, and the A video without a sense of incongruity can be obtained, and a reduction in the resolution of the video does not occur.

(Embodiment 3) A schematic configuration of an imaging apparatus according to Embodiment 3 of the present invention is described in Embodiment 1 shown in FIG.
Only the configuration and function of the high-sensitivity circuit are different from the schematic configuration of the imaging device in the above. Therefore, detailed description of the same configurations and functions will not be repeated. Note that the description will be made assuming that the reference numeral of the sensitivity increasing circuit in the present embodiment is 4 ″.

FIG. 10 is a block diagram showing a schematic configuration of the sensitivity increasing circuit 4 ".
A line memory 27 for delaying the video signal output from the D conversion circuit 3 by 1H, a line memory 28 for further delaying the video signal output from the line memory 27 by 1H, and a line memory 27 output from the line memory 27 A delay circuit 29 for delaying the video signal by up to two pixels,
An adder circuit 30 for adding the video signals output from the line memories 27 and 28 and the video signal output from the delay circuit 29, and adjusting the level of the video signal added by the adder circuit 30 to fall within a certain range. Limiter 3
1 and a selector 32 for switching and outputting the video signal output from the A / D conversion circuit 3 and the added video signal output from the limiter 31.

The line memory 27 delays the video signal output from the A / D conversion circuit 3 by 1H. Also,
Since the line memory 28 further delays the video signal output from the line memory 27 by 1H, it means that the current video signal output from the A / D conversion circuit 3 is delayed by 2H. Therefore, when the current video signal is included, a video signal for 3H is input to the addition circuit 30.

The delay circuit 29 generates a signal obtained by delaying the video signal output from the line memory 27 by one pixel and a signal delayed by two pixels. The adder circuit 30 outputs A /
The current video signal output from the D conversion circuit 3, the 1H delayed video signal output from the line memory 27 (the line including the pixel of interest), and the 2H delayed output from the line memory 28 The video signal, a video signal (target pixel) obtained by delaying the video signal output from the line memory 27 by one pixel, and a video signal obtained by delaying the video signal output from the line memory 27 by two pixels are added. . In this way, the adder circuit 30 adds the target pixel and the upper, lower, left, and right pixels of the target pixel, for a total of five pixels, and increases the amount of light of one pixel received by the solid-state imaging device 1, thereby increasing the video signal. Of high sensitivity.

FIG. 11 is a diagram for explaining the amplification factor of the sensitivity increasing circuit 4 ″ in the present embodiment. As shown in FIG. 11, when the brightness of the subject becomes darker than X2, the sensitivity is increased. The operation of the circuit 4 "is started, the gain becomes Y14, and the gain becomes a step shape.

FIG. 12 shows the CDS /
FIG. 3 is a diagram for explaining control of the AGC circuit 2. FIG.
As shown in (1), when the brightness of the subject becomes darker than X1, the system control microcomputer 7 gradually increases the amplification factor of the CDS / AGC circuit 2. When the brightness of the subject becomes darker than X2, the operation of the high-sensitivity circuit 4 ″ is started, so the system control microcomputer 7 sets the amplification factor of the CDS / AGC circuit 2 to Y15. As the signal becomes darker, the amplification factor of the CDS / AGC circuit 2 is gradually increased, and the amplification factor Y14 shown in FIG.
And the amplification factors Y3 and Y15 shown in FIG.
It becomes like the following formula.

Y14 = Y3-Y15 (4) FIG. 13 shows the charge accumulation time (amplification rate) of the solid-state imaging device 1.
FIG. 14 is a diagram showing the total gain obtained by combining the gain of the CDS / AGC circuit 2 and the gain of the high-sensitivity circuit 4 ″. As can be seen from FIG. 13, the total gain is continuously increased. Since the change is smooth, the imaging device according to the present embodiment can obtain a video signal that does not give a user an uncomfortable feeling.

The processing procedure of the imaging device according to the present embodiment is the same as the processing procedure of the imaging device according to the first embodiment shown in FIG. 7, and therefore, detailed description will not be repeated.

As described above, according to the imaging apparatus of the present embodiment, the resolution increasing circuit 4 ″ adds the pixel of interest and the upper, lower, left, and right pixels of the pixel of interest, for a total of five pixels, thereby increasing the resolution. Although a drop occurs, the frame rate is not reduced, so that even when a moving subject is imaged, the motion of the subject can be taken smoothly and an image without blurring can be obtained. became.

The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[0079]

According to one aspect of the present invention, when the illuminance of a subject is low, the control means causes the high sensitivity means to perform high sensitivity processing and controls the amplification factor of the amplification means.
The total amplification factor can be continuously and smoothly changed, and it is possible to obtain an image that is comfortable for the user.

Further, since the high sensitivity means integrates the video signals of a plurality of frames to increase the sensitivity, it is possible to obtain an image which is not uncomfortable for the user, and to prevent the resolution of the image from lowering. It has become possible.

Further, since the sensitivity increasing means adds the pixel of interest and the pixel adjacent to the pixel of interest in the video signal to increase the sensitivity, it is possible to obtain an image which is not uncomfortable for the user, and Blurring no longer occurs when a certain subject is photographed.

Further, the control means subtracts the gain of the high sensitivity means from the gain of the amplification means when the high sensitivity means starts the high sensitivity processing. It became possible to change smoothly.

According to another aspect of the present invention, the control means includes:
When the illuminance of the object is low, the sensitivity increasing means performs the sensitivity increasing process, the gain control means sets the initial gain amount to 1, and the gain control means gains as the illuminance of the object decreases. Since the amount is increased, the total amplification rate can be continuously and smoothly changed, and it is possible to obtain an image that does not give a user an uncomfortable feeling.

Further, since the sensitivity enhancing means integrates the video signals of a plurality of frames to enhance the sensitivity, it is possible to obtain an image which is not uncomfortable for the user, and to prevent the resolution of the image from lowering. It has become possible.

When the average luminance level of the video signal of one frame is smaller than the first luminance level, the control means causes the high-sensitivity means to perform the high-sensitivity processing, and the average luminance level becomes the second luminance level. When the level is larger than the level, the sensitivity increasing means stops the sensitivity increasing process. Therefore, by setting the optimal values for the first luminance level and the second luminance level, the image corresponding to the illuminance of the subject can be obtained. It became possible to obtain.

Further, since the first luminance level and the second luminance level have a hysteresis, it is possible to prevent the occurrence of flicker or the like by frequently operating / stopping the high sensitivity means. It has become possible.

When the control means is operating, the control means divides one frame into a plurality of areas and measures the brightness level of each area. If there is a predetermined number or more, the operation of the high-sensitivity means is stopped. Therefore, even when a high-luminance subject is imaged while the high-sensitivity means is operating, problems such as overexposed images may occur. It became possible to prevent.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of an imaging device according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a schematic configuration of a sensitivity increasing circuit 4 of FIG. 1;

FIG. 3 is a diagram for explaining control of a charge accumulation time (amplification factor) of the solid-state imaging device 1 according to the first embodiment of the present invention.

FIG. 4 shows CDS / AG according to Embodiment 1 of the present invention.
FIG. 4 is a diagram for explaining control of an amplification factor of a C circuit.

FIG. 5 is a diagram for explaining control of the amplification factor of the sensitivity increasing circuit 4 according to the first embodiment of the present invention.

FIG. 6 shows the charge storage time (amplification rate) of the solid-state imaging device 1 and the CDS / AGC circuit 2 according to the first embodiment of the present invention.
FIG. 6 is a diagram showing a total amplification ratio obtained by combining the amplification ratio of the high sensitivity circuit 4 with the amplification ratio of FIG.

FIG. 7 is a flowchart illustrating a processing procedure of the imaging device according to the first embodiment of the present invention.

FIG. 8 is a block diagram illustrating a schematic configuration of a sensitivity increasing circuit 4 ′ according to a second embodiment of the present invention.

FIG. 9 is a diagram for explaining an operation of the amplification factor control circuit 17 according to the second embodiment of the present invention.

FIG. 10 is a block diagram illustrating a schematic configuration of a sensitivity increasing circuit 4 ″ according to a third embodiment of the present invention.

FIG. 11 is a diagram for explaining control of an amplification factor of a sensitivity increasing circuit 4 ″ according to the third embodiment of the present invention.

FIG. 12 shows CDS / A according to Embodiment 3 of the present invention.
FIG. 4 is a diagram for explaining control of the amplification factor of the GC circuit 2.

FIG. 13 shows the total of the charge accumulation time (amplification rate) of the solid-state imaging device 1, the amplification rate of the CDS / AGC circuit 2, and the amplification rate of the sensitivity enhancement circuit 4 ″ in the third embodiment of the present invention. It is a figure which shows the amplification factor of.

[Explanation of symbols]

1 solid-state image sensor, 2 CDS / AGC circuit, 3 A /
D conversion circuit, 4 high sensitivity circuit, 5 video signal processing circuit, 6 TG circuit, 7 system control microcomputer, 8
Integration control circuit, 9 counter, 10, 14, 16, 32
Selector, 11, 12 memory, 13 readout circuit,
15, 31 limiter, 17 amplification rate control circuit, 27,
28 line memories, 29 delay circuits, 30 addition circuits.

Claims (11)

[Claims] 1. A solid-state imaging device for converting an image from a subject into a video signal, an amplification unit for amplifying a video signal output from the solid-state imaging device, and an amplified video output from the amplification unit Conversion means for converting a signal into a digital signal; high-sensitivity means for performing high-sensitivity processing on the video signal output from the conversion means; and high-sensitivity means when the illuminance of a subject is low. And control means for controlling the amplification factor of the amplifying means, and process processing means for performing a process processing on a video signal output from the high sensitivity means. Imaging device. 2. The imaging apparatus according to claim 1, wherein said sensitivity enhancing means integrates video signals of a plurality of frames to enhance the sensitivity. 3. The image pickup apparatus according to claim 1, wherein said sensitivity increasing means adds the pixel of interest in the video signal and a pixel adjacent to the pixel of interest to increase the sensitivity. 4. The control means subtracts the gain of the high sensitivity means from the gain of the amplification means when the high sensitivity means starts the high sensitivity processing.
The imaging device according to any one of the above. 5. A solid-state imaging device for converting an image from a subject into a video signal, an amplification unit for amplifying a video signal output from the solid-state imaging device, and an amplified video output from the amplification unit A conversion unit for converting a signal into a digital signal; a video signal output from the conversion unit; an amplification control unit configured to amplify while controlling a gain amount; and a video signal output from the amplification ratio control unit. A high-sensitivity means for performing the high-sensitivity processing; and when the illuminance of the subject is low, the high-sensitivity processing is performed by the high-sensitivity processing, and the initial gain amount is set to 1 by the gain control means. Control means for increasing the gain amount to the gain control means as the illuminance of the subject decreases, and performing process processing on the video signal output from the sensitivity enhancement means. An image pickup apparatus comprising: 6. The imaging apparatus according to claim 5, wherein said sensitivity increasing means integrates video signals of a plurality of frames to increase sensitivity. 7. The control means causes the sensitizing means to perform a sensitizing process when the average luminance level of the video signal of one frame is smaller than the first luminance level, and the average luminance level is set to 2. The method according to claim 1, wherein when the luminance level is higher than the second luminance level, the high-sensitivity means stops the high-sensitivity processing.
7. The imaging device according to any one of claims 6 to 6. 8. The imaging device according to claim 7, wherein the first luminance level and the second luminance level have a hysteresis. 9. The control unit divides one frame into a plurality of regions and measures a luminance level of each region when the sensitivity enhancing unit is operating. The imaging device according to claim 1, wherein when a predetermined number or more are adjacent to each other, the operation of the sensitivity increasing unit is stopped. 10. A solid-state imaging device for converting an image from a subject into a video signal, an amplification unit for amplifying a video signal output from the solid-state imaging device, and an amplified video output from the amplification unit A conversion unit for converting a signal into a digital signal, a sensitivity enhancement unit for performing a sensitivity enhancement process on the video signal output from the conversion unit, and a video signal output from the sensitivity enhancement unit. A process processing means for performing a process process by performing a process process when the illuminance of a subject is low. Setting the gain of the amplifying means by subtracting the gain of the sensitivity increasing means from the gain of (a). 11. A solid-state imaging device for converting an image from a subject into a video signal, an amplification unit for amplifying a video signal output from the solid-state imaging device, and an amplified video output from the amplification unit Conversion means for converting a signal into a digital signal; amplification rate control means for amplifying a video signal output from the conversion means while controlling a gain amount; and video output from the amplification rate control means. A method for controlling an imaging apparatus, comprising: a sensitivity increasing unit for performing a sensitivity increasing process on a signal; and a process processing unit for performing a process process on a video signal output from the sensitivity increasing unit. When the illuminance of the subject is low, causing the sensitizing means to perform a sensitizing process; and when the sensitizing means starts operating, initializing the amplification rate controlling means. Comprising a step of setting obtained amount to 1 times, and the step of gain amount increases in accordance with the illuminance of the subject is low, the control method of the imaging apparatus.