JPH0522669A - Video camera - Google Patents

Abstract

PURPOSE:To output a wide dynamic range signal as a camera output signal by performing an image pickup while switching exposure conditions by one field and obtaining a video signal with different exposure conditions. CONSTITUTION:A two-line simultaneous reading system CCD image sensor 52 performs the image pickup while switching the exposure conditions by one field and synthesizes picture signals with different exposure conditions by means of field memories 59 and 60 and signal selection switches 62, 64, and 65 at its output. In short, the iris adjustment of a lens 51 secures a level V1 indoors, set to be a level V2 outdoors by means of an electronic shutter. Further, the field memories 69 and 60 synchronize video signals S4 and S5 before one field and the present video signals S1 and S2, resulting in outputting the levels V1 and V2 selectively. Thus, the contrast can be reproduced well without becoming a white state even when the illumination conditions for an object differs greatly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to image pickup and output of an odd field image from a photoelectric conversion unit which photoelectrically converts light information in pixel units and accumulates and outputs a plurality of pixel information obtained by the photoelectric conversion for a predetermined time. The present invention relates to a video camera using a two-line simultaneous read-out type solid-state image sensor in which an image pickup output of an even field image is read out for each field, and in particular, an exposure condition is switched for each field and image pickup is performed equivalently. The present invention relates to a video camera capable of obtaining an imaging output having a wide dynamic range.

[0002]

2. Description of the Related Art CCD (Charge Coupled)
A solid-state image sensor such as a device (charge-coupled device) image sensor has excellent features such as no image sticking or afterimage, high impact resistance, and easy miniaturization of a camera, as compared with an imaging tube. There is. Normally, in a video camera conforming to a standard television system such as the NTSC system which adopts interlaced scanning, the imaging output from each pixel of the odd field image and the imaging output from each pixel of the even field image are performed for one field period ( In the NTSC system, a CCD image sensor is used which is read alternately every 1/60 sec. Further, a so-called Progressing Scan C is provided in which a horizontal transfer register for two lines is provided to read out the imaging output from each pixel of the odd field image and the imaging output from each pixel of the even field image within one field period.
A CD (hereinafter referred to as PS CCD) image sensor is provided for a high-resolution video camera.

Conventionally, as a technique of this kind of field, there is one as shown in FIG. 3, for example. FIG. 3 is a block circuit diagram showing a configuration example of a conventional video camera. In FIG. 3, the P.I. S. The light applied to the photoelectric conversion unit 2a of the CCD image sensor 2 is photoelectrically converted in the pixel unit in the photoelectric conversion unit 2a. Then, the P. S. In the CCD image sensor 2, the imaging output from each pixel of the odd field image and the imaging output from each pixel of the even field image obtained in the photoelectric conversion unit 2 are simultaneously read out for two lines via the horizontal transfer registers 3 and 4. It

Then, the video signal So obtained by the imaging output of the odd field image and the video signal Se obtained by the imaging output of the even field image read from the solid-state image sensor 2 are supplied to the A / D converter 7, 8 is supplied. On the other hand, the outputs of the amplifiers 5 and 6 are sent to the control unit 11 via the adder 9 and the buffer amplifier 10. The control unit 11 is a circuit that controls the aperture of the lens 1 and also applies a shutter control signal Sc to the timing generator 12 to control the electronic shutter function of the CDD image sensor 2. The outputs of the A / D converters 7 and 8 are supplied to the changeover switch 13. The changeover switch 13 is changed over according to the field changeover pulse FP output from the sync generator 14, and the result of the changeover is output to the output terminal 16 as the camera output signal Vo via the process amplifier 15.

[0005]

By the way, as shown in FIG. 4, the method of expanding the dynamic range in the video camera as described above has a narrow range of about 90% to 110% of the signal level of the camera output signal Vo. The mainstream method is to compress and insert a wide dynamic range component of about 90% to 600% of the CCD output Co into a level. However, in such an expansion method, since the processing is performed in a non-linear manner, there is a limit to the expansion of the dynamic range, and there is a problem that the gradation of the CCD output Co in the Z range shown in FIG. 4 cannot be obtained. .. Ie CCD
Since 90% to 600% of the output Co can be expressed only at a level of about 90% to 110%, for example, when the illumination conditions of the subject are extremely different, such as an indoor scene where there is an outdoor scene through some windows. , When iris adjustment (lens diaphragm) is performed with an emphasis on indoor contrast, outdoor scenes are almost overexposed.

The present invention has been made in view of such circumstances, and an object thereof is to provide a video camera capable of outputting a signal having a wide dynamic range as a camera output signal.

[0007]

A video camera according to the present invention photoelectrically converts light information on a pixel-by-pixel basis, and accumulates and outputs a plurality of pixel information obtained by the photoelectric conversion for a predetermined time. A two-line simultaneous read-out type solid-state image sensor in which the image pickup output of an image and the even-numbered field image pickup are read out for each field, an exposure control unit for switching the exposure condition for each field, and an odd number read out from the solid-state image sensor A first field memory for storing one field of a video signal obtained by imaging output of a field image, and a second field memory for storing one field of a video signal obtained by imaging output of an even field image read from the solid-state image sensor, Two lines are simultaneously read out from the solid-state image sensor. An odd field image read from the solid-state image sensor, which is controlled by first level comparing means for comparing the signal level of the video signal by the image pickup output of the odd field image with a reference level, and comparison output by the first level comparing means. And a first switching means for switching and outputting the video signal by the image pickup output of the first field memory and the video signal by the image pickup output of the odd field image one field before which is read from the first field memory, and read from the second field memory. Second level comparing means for level-comparing the signal level of the video signal by the imaged output of the even field image one field before, and the second analog / digital converter based on the second control pulse. Output data and second field memory output Second switching means for switching to and from the data, and a video signal by the image pickup output of an even field image read from the solid-state image sensor and controlled by the comparison output by the second level comparison means, and the second field. Second switching means for switching and outputting a video signal obtained by picking up and outputting an even field image one field before read from the memory, and video by picking up and outputting an odd field image outputted through the first switching means. By including a signal and a camera output generation unit that generates a camera output signal by alternately selecting, for each field, a video signal obtained by picking up and outputting an even field image output through the second switching means, Solve the problem.

[0008]

In the video camera according to the present invention, the two-line simultaneous read-out type solid-state image sensor is used to switch the exposure condition for each field to perform imaging, and for example, the first and second field modes are used for fields with long exposure times. In addition, as fields having a short exposure time, the exposure conditions are switched for each field between an exposure state suitable for capturing a relatively dark image and an exposure state suitable for capturing a relatively bright image, and the images are exposed to each other. Obtain video signals under different conditions. In addition, 2 from the solid-state image sensor
Simultaneous line readout The video signal output by the image output of each field is stored in the first and second field memories, and the high brightness portion of the video signal by the image output under the exposure condition suitable for capturing the dark image is detected. , The high-brightness portion is replaced with the video signal by the imaging output under the exposure condition suitable for the imaging of the bright image by the first or second switching means. Then, the camera output generation unit outputs a video signal by the imaging output of the odd field image output through the first switching unit and a video signal by the imaging output of the even field image output through the second switching unit. The signals are alternately selected for each field, and a camera output signal is generated and output.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a one-chip CC according to an embodiment of the present invention.
It is a block circuit diagram which shows schematic structure of a D video camera. In the present embodiment, when the illumination conditions of the subject are extremely different, for example, a scene in which there is an outdoor scene through a window in an indoor scene is assumed as the subject.

In the video camera shown in FIG. 1, the P.O.I. is provided via a lens 51 which is focused to a predetermined light amount by iris adjustment (adjustment of the effective aperture of the lens). S. The light emitted to the photoelectric conversion unit 52a of the CCD image sensor 52 is
The photoelectric conversion unit 52a performs photoelectric conversion on a pixel-by-pixel basis. Then, the P. S. In the CCD image sensor 52, the image pickup output from each pixel of the odd field image and the image pickup output from each pixel of the even field image obtained by the photoelectric conversion unit 52a are transferred to the horizontal transfer register 52b,
Two lines are simultaneously read out via 52c.

In the photoelectric converter 52a, photosensitive elements such as photodiodes (not shown) corresponding to respective pixels of the odd field image and the even field image are arranged in a matrix. Pixel information obtained by the photoelectric conversion action of each photosensitive element in the photoelectric conversion unit 52a is accumulated for a predetermined time, and a horizontal transfer register 52b for picking up and outputting an odd field image via a vertical transfer register.
And an even field image is transferred to the horizontal transfer register 52c for imaging output. Then, from the output side of these horizontal transfer registers 52b and 52c, the video signal So obtained by the image pickup output of the odd field image and the video signal Se obtained by the image pickup output of the even field image are simultaneously output within one field period.

The CCD image sensor 52 has an electronic shutter function. This electronic shutter function is to obtain the same effect as the shutter of a film camera by changing the accumulation time of the pixel information. Pixel information is usually accumulated for 1/60 seconds determined by the NTSC system, but according to the electronic shutter function, the shutter speed (1/2000 seconds, 1/10 seconds).
00 seconds ...) is accumulated only for the time determined.

Here, the shutter control signal SC having a different level for each field output from the control unit 53 is supplied to the CCD image sensor 52 via the timing generator 54, and as a result, the field (1/60
Every second), the accumulation time of the pixel information changes. That is,
The shutter speed changes for each field, and a field having a long exposure time (first field mode) and a field having a short exposure time (second field mode) are alternately repeated.

The video signal So obtained by the imaging output of the odd field image and the video signal Se obtained by the imaging output of the even field image thus obtained are supplied to the amplifier 5
It is supplied to A / D converters 57 and 58 via 5, 56, respectively. When A / D converted by the A / D converters 57 and 58, video signals S1 and S2 having different exposure times for each field are obtained on the output side of the subject. That is, the video signals S1 and S2 are
As shown in FIG. 2, a field having a high video level and a field having a low video level are signals that are alternately repeated in the first and second field modes, respectively. Here, the period of the first field mode is an odd field, and the period of the second field mode is an even field.

The symbol P in FIG. 2 corresponds to an outdoor scene through a window with high brightness, and the symbol Q corresponds to an indoor scene with low brightness. Further, the level V1 in FIG. 2 is automatically set to be an appropriate value according to the indoor lighting condition by controlling the iris adjustment described above by the control unit 53 in the first field mode. Similarly, level V
In the second field mode, 2 is automatically set to an appropriate value according to the outdoor lighting condition by controlling the electronic shutter function described above.

After that, the video signals S1 and S2 are stored in the field memories 59 and 60 for one field, respectively. That is, the video signal S obtained by digitizing the video output of the odd-numbered field image is digitized.
1 is stored in the field memory 59, and the video signal Se obtained by the imaging output of the even field image is output.
The digitized video signal S1 is stored in the field memory 59. At the same time, the video signal S
1 is supplied to the positive side input terminal of the comparator 61. The comparator 61 compares the level of the video signal S1 with the first reference level Vf and outputs the comparison result to the changeover switch (first changeover means) 62 as the first control pulse S3. Here, the reference level Vf
Are set corresponding to the high luminance part of the video signal S1. Thus, as shown in FIG. 2, the first control pulse S3 output from the comparator 61 becomes a high level when the level of the video signal S1 is higher than the reference level Vf (P in FIG. 2) and is low when it is low. Is a low level.

The changeover switch 62 performs a changeover operation in response to the first control pulse S3 to select either one of the signal S1 and the output S4 of the field memory 59. For example, the output S4 is selected when the first control pulse S3 is at the high level. Since the output S4 of the field memory 59 is a signal one field before the video signal S1, the video signal S1 is a signal shifted by one field as shown in FIG. Therefore, the output S4 in the first field mode has the same shape as the video signal S1 in the field having a low video level, and therefore the level V2
Of the level V2 only during the period t2 of the level V2,
The control pulse S3 becomes the high level. Therefore, the changeover switch 62 selects the output S4 only during the period t2 in the first field mode, and during the other periods t1 and t3,
Since the control pulse S3 is at the low level, the video signal S
Select the level V1 of 1.

In this way, the high-luminance portion of the video signal S1 (P in FIG. 2; camera output 1) obtained by digitizing the video signal So obtained by the imaging output of the odd-numbered field image.
(00% or more) is detected at the high level of the control pulse S3, and only when the video signal S1 has high brightness, it is possible to switch to the video signal of the field having a low video level.

Thus, as shown in FIG. 2, the signal S7 having the levels V1 and V2 set within the odd field period is output to the output side of the changeover switch 62.

On the other hand, the output S5 of the field memory 60
Is input to the plus side input terminal of the comparator 63. In the comparator 63, the output S5 of the field memory 60, that is, the video signal S2 obtained by digitizing the video signal Se obtained by the image pickup output of the even field image is delayed by one field by the field memory 60 and the reference level Vf. The magnitudes are compared, and the comparison result is output to the changeover switch (second changeover means) 64 as the second control pulse S6 as shown in FIG. This second control pulse S6 is, as shown in FIG.
A high-luminance portion in which the level of the signal S5 is larger than the reference level Vf (Pa in FIG. 2; camera output 100% or more) (FIG. 2)
Pa), the level is high, and when it is small, the level is low.

By performing the changeover operation of the changeover switch 64 with such a control pulse S6, the output side of the changeover switch 62 is at the level V, as shown in FIG.
Signal S8 in which 1 and V2 are set within the even field period
Is output.

Then, from the signal S7 formed from the video signal S1 obtained by digitizing the video signal So obtained by the image pickup output of the odd field image and the video signal S2 obtained by digitizing the video signal Se obtained by the image pickup output of the even field image. The formed signal S8 is output by the changeover switch 65 of the camera output generator 67 as shown in FIG.
By switching field by field in response to the field switching pulse FP that is inverted field by field, a field-sequential signal S9 corresponding to interlaced scanning is obtained. Thereafter, the signal S9 is supplied to the process amplifier 66, subjected to predetermined signal processing such as synchronization signal addition processing, and then sent to the output terminal 68 as a camera output signal Vo. The camera output generator 67 is composed of a changeover switch 65 and a process amplifier 66.

By the way, in the present embodiment, the above-mentioned levels V1 and V2 are automatically set. The description will be simplified below.

The outputs of the amplifiers 55 and 56 are added by an adder (adding means) 69, and the addition result is supplied to the common terminal of the changeover switch 71 of the control unit 53 via the buffer amplifier 70. Here, the control unit 53 is composed of a changeover switch (mode switching unit) 71, an iris control unit 72, and a shutter control unit 73. The changeover switch 71 is adapted to switch the connection mode according to the field changeover pulse FP. For example, when the field switching pulse FP is at a high level, the first field mode is switched to the iris control section 72 side, and when it is at a low level, the second field mode is switched to the shutter control section 73 side.

The iris control section 72 includes a switch 72a,
The shutter control section 73 includes a level detection circuit 72b and an error amplifier 72c.
It is composed of an error amplifier 73b and a changeover switch 73c. The level detection circuit 72b has a time constant enough to hold the next field period.

In the first field mode, since the changeover switch 73c selects the power source VC (second reference level), the shutter control signal SC becomes maximum and the shutter speed becomes 1/60 sec. in addition,
The output of the adder 69 is given to the switch 72a via the buffer amplifier 70 and the changeover switch 71.
The switch 72a is adapted to be turned on / off based on the first control pulse S3 inverted by the inverter 74. For example, the switch 72a is turned off when the control pulse S3 is at a high level and turned on when the control pulse S3 is at a low level. Therefore, the level detection circuit 72b takes in the output of the buffer amplifier 70 at the low level of the control pulse S3, that is, during the periods t1 and t2 shown in FIG. 2 and detects the output level.

Further, the error amplifier 72c detects how much the detected level has an error with respect to the level V1. Then, iris adjustment is performed so that the error becomes zero. As a result, the low luminance portion Q of the video signals S1 and S2 in the first field mode is set to the level V1.

On the other hand, in the second field mode, the output of the adder 69 is supplied to the level detection circuit 73a via the buffer amplifier 70 and the changeover switch 71, and the output level thereof is detected. Further, the error amplifier 73b detects how much the detected output level has an error with respect to the above level V2 (V2> V1). Then, the shutter control signal SC is supplied to the CCD image sensor 52 via the changeover switch 73c and the timing generator 54 so that the error becomes zero, and controls the electronic shutter of the CCD. As a result, the video signal S in the second field mode
The high-intensity part P of 1 and S2 is set to level V2.

The sync generator 74
The field switching pulse FP is generated, and the sync signals of all the components shown in FIG. 1 are also generated by the sync generator 74.

As described above in detail, in this embodiment, the indoor level V1 is secured by the iris adjustment of the lens 51, and the outdoor level V2 is set by the electronic shutter, and the field memory 69 is further set. , 60, the video signals S4 and S5 one field before and the current video signal S
Since 1 and S2 are synchronized, the level V1 and the level V2 can be selectively selected and output. This allows
Even in a scene where the illumination conditions of the subject are extremely different, it is possible to reproduce with good contrast without causing overexposure as in the past.

The present invention is not limited to the above embodiment, but can be applied to, for example, a 3-chip CCD color video camera in addition to the 1-chip CCD video camera. The levels V1 and V2 may be set manually instead of automatically.

[0032]

As is apparent from the above description, in the video camera according to the present invention, the two-line simultaneous read-out type solid-state image sensor is used to switch the exposure condition for each field to perform imaging. The second field mode is set to a field having a long exposure time and a field having a short exposure time, one for each field for an exposure state suitable for capturing a relatively dark image and an exposure state suitable for capturing a relatively bright image. The exposure conditions are switched to and imaging is performed to obtain video signals having different exposure conditions. In addition, two lines are simultaneously read out from the solid-state image sensor, and a video signal based on the imaging output of each field is first
And a second field memory are stored, a high-intensity part of the video signal by the imaging output under the exposure condition suitable for imaging the dark image is detected, and the high-intensity part is switched to the first or second switching means. Is replaced with a video signal obtained by image pickup output under an exposure condition suitable for picking up the bright image. Then, the camera output generation unit outputs a video signal by the imaging output of the odd field image output through the first switching unit and a video signal by the imaging output of the even field image output through the second switching unit. Since the signals are alternately selected for each field and the camera output signal is generated and output, the video signal before the field and the current video signal are synchronized to form a video signal having an equivalently expanded dynamic range. Even if the lighting conditions of the subject are extremely different, such as when there is an outdoor scene through a window in an indoor scene, the outdoor scene will be overexposed as in the past. It can be reproduced with good contrast.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing a schematic configuration of a 1-chip CCD video camera that is an embodiment of the present invention.

FIG. 2 is a timing chart showing the operation of the video camera shown in FIG.

FIG. 3 is a block circuit diagram showing a configuration example of a conventional video camera.

FIG. 4 is an explanatory diagram of a conventional problem.

[Explanation of symbols]

 52 ... CCD image sensor 52a ... Photoelectric conversion section 52b, 52c ... Horizontal transfer register 53 ... Control section 57, 58 ... A / D converter 59 , 60 ... Field memory 61, 63 ... First and second comparators 62, 64 ... First and second switching means 67 ... Camera output generation unit 69 ... Addition means 71 ... Mode switching means 72 ... Iris control section 73 ... Shutter control section

Claims (1)

Claim: What is claimed is: 1. A photoelectric conversion unit that photoelectrically converts optical information in pixel units, and accumulates and outputs a plurality of pixel information obtained by the photoelectric conversion for a predetermined time. 2-line simultaneous read-out type solid-state image sensor that reads even-field image pickup output for each field, exposure control unit that switches the exposure condition for each field, and odd-field image pickup output read from the solid-state image sensor From the solid-state image sensor, a first field memory for storing one field of the video signal according to the above, and a second field memory for storing one field of the video signal according to the imaging output of the even field image read from the above-mentioned solid-state image sensor. Odd field image read simultaneously on two lines By the first level comparing means for comparing the signal level of the video signal by the image pickup output with the reference level, and the image pickup output of the odd field image read from the solid-state image sensor, which is controlled by the comparison output by the first level comparing means. First switching means for switching and outputting a video signal and a video signal by imaging output of an odd field image of one field before read from the first field memory; and one field before read from the second field memory Second comparison for comparing the signal level of the video signal by the image pickup output of the even field image with the reference level
Level comparing means, second switching means for switching the output data of the second analog / digital converter and the output data of the second field memory based on the second control pulse, and the second switching means. Of the even field image read out from the solid-state image sensor and controlled by the comparison output by the level comparing means, and the video signal output from the even field image one field before read out from the second field memory. And a second switching means for switching and outputting the video signal, a video signal generated by imaging output of the odd field image output through the first switching means, and an even field image output through the second switching means. The video signal by the imaging output of is selected alternately for each field,
And a camera output generation unit that generates a camera output signal.