JP2970092B2 - Video camera - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric conversion unit for photoelectrically converting optical information on a pixel basis and storing and outputting a plurality of pieces of pixel information obtained by the photoelectric conversion for a predetermined period of time. The present invention relates to a video camera using a solid-state image sensor of a two-line simultaneous reading type in which an imaging output of an even-numbered line image is read out for each field.
The present invention relates to a video camera that performs imaging by switching the exposure condition for each field and changes the exposure condition so that an imaging output with a wide dynamic range can be equivalently obtained.

[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 characteristics such as being free from image sticking and after-image, having high shock resistance, and being easy to miniaturize a camera, as compared with an image pickup tube. I have. Normally, in a video camera conforming to a standard television system such as the NTSC system employing interlaced scanning, an imaging output from each pixel of an odd-line image and an imaging output from each pixel of an even-line image are applied for one field period (NTSC). CCD that alternately reads every 1/60 sec in the system
An image sensor is used. In addition, a so-called Progressing Scan CCD (where a horizontal transfer register for two lines is provided so as to read out the imaging output from each pixel of the odd line image and the imaging output from each pixel of the even line image in one field period). Less than,
Simply P. S. An image sensor (referred to as a CCD) is provided for high-resolution video cameras.

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

Then, a video signal So based on an imaging output of an odd line image read from the solid-state image sensor 2 and a video signal S based on an imaging output of an even line image.
e is supplied to A / D converters 7 and 8 via amplifiers 5 and 6. 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 controls the electronic shutter function of the CDD image sensor 2 by supplying a shutter control signal SC to the timing generator 12. The outputs of the A / D converters 7 and 8 are
It is supplied to the changeover switch 13. The changeover switch 13 is changed over in response to a field changeover pulse FP output from the sync generator 14, and the result of the change is output to the output terminal 16 as the camera output signal Vo via the process amplifier 15.

[0005]

By the way, the technique of expanding the dynamic range in a video camera as described above, as shown in FIG. 4, covers a narrow range of about 90% to 110% of the signal level of the camera output signal Vo. In general, a wide dynamic range component of about 90% to 600% of the CCD output Co is compressed and inserted. However, in such an enlargement method, since the processing is performed non-linearly, there is a limit to the enlargement of the dynamic range, and there is a problem that the CCD output Co in the Z range shown in FIG. . That is, 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 lighting conditions of an object such as an indoor scene having an outdoor scene through a window are extremely different. However, when iris adjustment (lens aperture) is performed with emphasis on indoor contrast, almost all outdoor scenes are overexposed.

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

[0007]

According to a video camera according to the present invention, an odd number of pixels are photoelectrically converted from a photoelectric conversion unit which photoelectrically converts optical information in units of pixels and stores and outputs a plurality of pieces of pixel information obtained by the photoelectric conversion for a predetermined time. A two-line simultaneous readout type solid-state image sensor in which an image output of a line image and an image output of an even-numbered line image are read out for each field, an exposure control unit that switches exposure conditions for each field, and read out from the solid-state image sensor. A first field memory for storing one field of a video signal based on an imaging output of an odd line image, and a second field memory for storing a video signal for one field of an imaging output of an even line image read from the solid-state image sensor; , Odd-numbered line image read out simultaneously from the solid-state image sensor by two lines First level comparing means for comparing the signal level of the video signal by the imaging output with the reference level, and the imaging output of the odd-numbered line image controlled by the first level comparing means by the comparison output and read from the solid-state image sensor Switching means for switching and outputting a video signal based on the above-mentioned method and a video signal based on an imaging output of an odd-numbered line image one field before read out from the first field memory, and one field read out from the second field memory Second level comparing means for comparing a signal level of a video signal obtained by imaging output of the previous even-numbered line image with the reference level;
The video signal is controlled by the comparison output by the level comparison means, and is a video signal based on an imaging output of an even line image read from the solid-state image sensor and a video signal based on an imaging output of an even line image one field before read from the second field memory. A second switching means for switching and outputting a video signal based on an imaging output of an odd line image outputted via the first switching means, and an even line image outputted via the second switching means. The above-mentioned problem is solved by having a camera output generating means for alternately selecting a video signal based on the image pickup output for each field and generating a camera output signal.

[0008]

In the video camera according to the present invention, the solid-state image sensor of the two-line simultaneous readout type switches the exposure condition for each field and performs imaging. For example, the first field and the second field are each subjected to a field having a long exposure time. As a field having a short exposure time, the exposure conditions are switched for each field between an exposure condition suitable for capturing a relatively dark image and an exposure condition suitable for capturing a relatively bright image. Obtain video signals with different conditions. In addition, 2
A video signal based on the imaging output of the odd-numbered line image and a video signal based on the imaging output of the even-numbered line image, which are simultaneously read out from the line, are stored in the first and second field memories, and are exposed under exposure conditions suitable for capturing the dark image. A high-luminance portion of the video signal resulting from the imaging output is detected, and the high-luminance portion is replaced by the first or second switching means with a video signal generated by the imaging output under an exposure condition suitable for capturing the bright image. The camera output generation unit is configured to output the video signal based on the imaging output of the odd line image output through the first switching unit and the imaging output of the even line image output through the second switching unit. A video signal is alternately selected for each field, and a camera output signal is generated and output.

[0009]

FIG. 1 shows a one-chip CC according to an embodiment of the present invention.
FIG. 2 is a block circuit diagram illustrating a schematic configuration 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 iris adjustment (adjustment of the effective aperture of the lens) adjusts the P.I. S. 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 above P.E. S. In the CCD image sensor 52, two lines are simultaneously read out through the horizontal transfer registers 52b and 52c, the imaging output from each pixel of the odd line image and the imaging output from each pixel of the even line image obtained by the photoelectric conversion unit 52a. You.

In the photoelectric conversion section 52a, photosensitive elements such as photodiodes (not shown) corresponding to respective pixels of an odd line image and an even field image are arranged in a matrix. The 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 the horizontal transfer register 52b for imaging and outputting the odd line image and the imaging of the even line image via the vertical transfer register. The data is transferred to the output horizontal transfer register 52c. The horizontal transfer registers 52b, 52c
, A video signal So based on the imaging output of the odd-numbered line image and a video signal Se based on the imaging output of the even-numbered line image are simultaneously output within one field period.

The CCD image sensor 52 has an electronic shutter function. This electronic shutter function is
By changing the accumulation time of the pixel information, the same effect as the shutter of the film camera can be obtained. The pixel information is usually 1 determined by the NTSC system.
/ 60 seconds, but according to the electronic shutter function, the shutter speed (1/2000 seconds, 1/1000 seconds ...
・ It is accumulated only for the time determined in ()).

Here, the shutter control signal SC of 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 second)
Each time the accumulation time of the pixel information changes. That is, the shutter speed changes for each field, and a field with a long exposure time (first field mode) and a field with a short exposure time (second field mode) are alternately repeated.

The video signal So obtained by the imaging output of the odd line image and the video signal Se obtained by the imaging output of the even line image are supplied to A / D converters 57 and 58 via amplifiers 55 and 56, respectively. Supplied. When A / D conversion is performed by the A / D converters 57 and 58, video signals S1 and S2 having different exposure times from the subject for each field are obtained on the output side.
That is, as shown in FIG. 2, the video signals S1 and S2 are signals in which a high video level field and a low video level field 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 high-luminance window, and the symbol Q corresponds to an indoor scene with a low luminance. Further, the level V1 in FIG. 2 is automatically set to an appropriate value according to indoor lighting conditions by controlling the iris adjustment 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 outdoor lighting conditions by controlling the electronic shutter function described above.

Thereafter, the video signals S1 and S2 are stored in the field memories 59 and 60 for one field, respectively. That is, a video signal S1 obtained by digitizing the video signal So based on the imaging output of the odd line image.
Is stored in the field memory 59, and a video signal S1 obtained by digitizing the video signal Se obtained by capturing and outputting the even-numbered line image is stored in the field memory 59. At the same time, the video signal S1 is
It is supplied to the plus 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 compares the comparison result with the first reference level Vf.
Is output to the changeover switch 62 as the control pulse S3. Here, the reference level Vf is set corresponding to the high luminance portion of the video signal S1. 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),
If it is smaller, it will be at a lower level.

The changeover switch 62 performs a changeover operation in accordance with the first control pulse S3 to select either the signal S1 or the output S4 of the field memory 59. For example, when the first control pulse S3 is at a high level, the output S4 is selected. Since the output S4 of the field memory 59 is a signal one field before the video signal S1, it is a signal in which the video signal S1 is shifted by one field as shown in FIG. Therefore, the output S4 in the first field mode has the same form as the video signal S1 at the time of the field having the low video level, and therefore includes the component of the level V2.
Only, the control pulse S3 becomes the high level. for that reason,
The changeover switch 62 selects the output S4 for the period t2 in the first field mode, and selects the output S4 for the other periods t1,
At t3, the level V1 of the video signal S1 is selected because the control pulse S3 is at a low level.

In this manner, the high luminance portion (P in FIG. 2; camera output 100) of the video signal S1 obtained by digitizing the video signal So generated by the imaging output of the odd line image.
%) Is detected at the high level of the control pulse S3, and only when the video signal S1 has a high luminance, it is possible to switch to the video signal of the field with a low video level.

Thus, as shown in FIG. 2, a signal S7 in which the levels V1 and V2 are 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 input terminal of the comparator 63. Comparator 6
In step 3, the output signal S5 of the field memory 60, that is, the video signal S2 obtained by digitizing the video signal Se obtained by the imaging output of the even-numbered line image is stored in the field memory 6
The signal S5 delayed by one field by 0 is compared with the reference level Vf, and the comparison result is used as a second control pulse S6 as shown in FIG.
Output to As shown in FIG. 2, the second control pulse S6 has a high level in a high-brightness portion (Pa in FIG. 2; camera output 100% or more) where the level of the signal S5 is higher than the reference level Vf (Pa in FIG. 2). Level, and if lower, the level is lower.

By performing the switching operation of the changeover switch 64 with such a control pulse S6, the levels V1 and V2 are set at the output side of the changeover switch 62 within the even field period as shown in FIG. A signal S8 is output. A signal S7 formed from a video signal S1 obtained by digitizing the video signal So based on the imaging output of the odd-numbered line image, and a video signal S2 formed from a digitized video signal Se generated by imaging the output of the even-numbered line image. The signal S8 is supplied to the switch 65 of the camera output generation unit 67 by the switch 65 as shown in FIG.
Field switching pulse FP that reverses for each field
Is switched for each field in accordance with the above, so that a field-sequential signal S9 corresponding to interlaced scanning is obtained.
It is said. Thereafter, the signal S9 is supplied to the process amplifier 66.
After being subjected to a predetermined signal processing such as a synchronization signal adding process, the signal is sent to the output terminal 68 as a camera output signal Vo. Note that the camera output generation unit 67 includes a changeover switch 65 and a process amplifier 66.

In the present embodiment, the above-described setting of the levels V1 and V2 is automatically performed. Hereinafter, the description will be simplified. The outputs of the amplifiers 55 and 56 are added by an adder 69, and the addition result is supplied to a common terminal of a changeover switch 71 of the control unit 53 via a buffer amplifier 70. Here, the control unit 53 includes a changeover switch 71, an iris control unit 72, and a shutter control unit 73. The changeover switch 71 switches 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 unit 72 side, and when the field switching pulse FP is at a low level, the second field mode is switched to the shutter control unit 73 side.

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

In the first field mode, the changeover switch 73c selects the power supply VC (second reference level), so that the shutter control signal SC becomes maximum and the shutter speed becomes 1/60 sec. In addition, the output of the adder 69 is provided to the switch 72a via the buffer amplifier 70 and the changeover switch 71. The switch 72a is turned on and off based on the first control pulse S3 inverted by the inverter 74. For example, the switch 72a turns off when the control pulse S3 is at a high level and turns 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 only when the control pulse S3 is at the low level, 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 portions Q of the video signals S1 and S2 in the first field mode are 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 is detected. Further, the error amplifier 73b detects how much the detected output level has an error with respect to the 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 signals S1,
The high luminance portion P of S2 is set to level V2.

Note that the sync generator 74
A field switching pulse FP is generated, and synchronization signals of all the components shown in FIG.
4 generated by As described in detail above,
In this embodiment, the indoor level V1 is secured by the iris adjustment of the lens 51, and the electronic shutter is set to the outdoor level V2.
, The video signals S4 and S5 one field before and the current video signals S1 and S2 are synchronized, so that the level V1 and the level V2 can be selectively selected and output. As a result, even in a scene in which the illumination conditions of the subject are extremely different, it is possible to reproduce with good contrast without becoming overexposed as in the related art.

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

[0028]

As is clear from the above description, in the video camera according to the present invention, the solid-state image sensor of the two-line simultaneous readout type switches the exposure condition for each field and performs imaging. The field and the second field are defined as a field having a long exposure time and a field having a short exposure time, respectively, for each of the exposure conditions suitable for capturing a relatively dark image and the exposure conditions suitable for capturing a relatively bright image. The image pickup is performed by switching the exposure conditions to obtain video signals having different exposure conditions. In addition, a video signal based on an imaging output of an odd line image and a video signal based on an imaging output of an even line image which are simultaneously read out from the solid-state image sensor by two lines are first.
And a second field memory for detecting a high-brightness portion of the video signal by the imaging output under the exposure condition suitable for capturing the dark image, and using the high-brightness portion as the first or second switching means. Is replaced with a video signal based on an imaging output under exposure conditions suitable for imaging the bright image. The camera output generation unit is configured to output the video signal based on the imaging output of the odd line image output through the first switching unit and the imaging output of the even line image output through the second switching unit. Since the video signal is alternately selected for each field, and a 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 expanded dynamic range equivalently. You can, for example,
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, unlike the conventional case, the outdoor scene does not become overexposed and the contrast is improved. Can be reproduced.

[Brief description of the drawings]

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

FIG. 2 is a timing chart showing an 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 unit, 5
2b, 52c horizontal transfer register, 53 control unit, 5
7, 58 A / D converter, 59, 60 field memory, 61, 63 comparator, 62, 64, 71 changeover switch, 67 camera output generation unit, 69 adder, 72 iris control unit, 73 shutter control unit

Claims (1)

(57) [Claims] An imaging output of an odd-numbered line image and an imaging output of an even-numbered line image from a photoelectric conversion unit that photoelectrically converts optical information in pixel units and stores and outputs a plurality of pieces of pixel information obtained by the photoelectric conversion for a predetermined time. , A two-line simultaneous readout solid-state image sensor that reads out one field at a time, an exposure control unit that switches exposure conditions for one field, and a one-field video signal based on an imaging output of an odd line image read out from the solid-state image sensor. A first field memory for storing the video signal of the even line image read out from the solid-state image sensor for one field; a second field memory for storing one line of the video signal read out from the solid-state image sensor; and two lines simultaneously read from the solid-state image sensor. Signal level of video signal from odd line image pickup output A first level comparing means for comparing with a reference level, a video signal based on an imaging output of an odd line image read from the solid-state image sensor and controlled by a comparison output by the first level comparing means, and the first field memory A first switching means for switching and outputting a video signal based on an imaging output of an odd line image one field before read from the memory; and a video based on an imaging output of an even line image one field before read from the second field memory. A second level comparing means for comparing the signal level of the signal with the reference level; and a video signal controlled by a comparison output by the second level comparing means, the video signal being an imaging output of an even line image read from the solid-state image sensor. One file read from the second field memory A second switching unit for switching and outputting a video signal based on an imaging output of an even line image before the field, a video signal based on an imaging output of an odd line image output via the first switching unit, and the second switching unit, And a camera output generating means for generating a camera output signal by alternately selecting a video signal based on an imaging output of an even-numbered line image output through the switching means.