JP3517421B2 - Video camera and photometric method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a video camera (including a still / movie video camera and a still video camera) that performs photometry of an object using a video signal obtained from a solid-state electronic image pickup device and determines exposure conditions. And its photometric method.

[0002]

BACKGROUND ART In a camera having an automatic exposure (so-called AE) function, photometry is necessary to determine an exposure condition. There are various methods for photometry. One of them is to arrange a photometric element in front of the camera. Although this method has a simple configuration, it has an essential problem that the photometric area does not match the shooting area. This problem is particularly noticeable when the field of view is changed using a zoom lens. In order to solve this problem, it is necessary to change the photometric area of the photometric element in conjunction with the zoom lens of the imaging system, which requires a large-scale mechanism.

A method in which a photometric element is incorporated in the image pickup optical system so that the photometric area coincides with the image pickup area (so-called TTL photometry).
There is also. This method requires a beam splitter, an optical path changing element, etc. in the imaging optical system, which leads to an increase in the size of the optical system and a decrease in sensitivity. Moreover, when a mirror is used, there are problems in terms of durability and reliability.

Therefore, in a video camera equipped with a solid-state electronic image pickup device (CCD or the like) to obtain a video signal representing a subject image, the video signal output from the solid-state electronic image pickup device is integrated over an appropriate photometric region. A method of obtaining a photometric value is considered. According to this method, there is an advantage that the image pickup area and the photometric area are completely coincident with each other, and an extra optical system for increasing the size is not required. Also,
By electrically processing the video signal obtained from the solid-state electronic image sensor, variations such as average photometry, partial photometry, and split photometry are possible, and it is possible to set the exposure conditions corresponding to various shooting environments. The range of applications expands.

The applicant invented and applied for a method for obtaining a photometric value based on a video signal output from a solid-state electronic image pickup device (filed on July 14, 1992, Patent No. 30589).
No. 94).

The invention of this prior application will be described in detail below. The solid-state electronic image pickup device is exposed, and a video signal representing a subject image is output from the solid-state electronic image pickup device. A luminance signal extraction circuit extracts a luminance signal component from the video signal and integrates it over a predetermined photometric period within the horizontal scanning period. The integrated value is converted into digital integrated data in the analog / digital conversion circuit every horizontal scanning period. The digital integrated data is added within the vertical scanning period, and the photometric value is calculated from this added data.

[0007]

DISCLOSURE OF THE INVENTION The present invention is an improvement of the invention of the prior application, and uses a general analog / digital conversion circuit which is not highly accurate and has a low luminance based on a video signal output from a solid-state electronic image pickup device. The purpose is to be able to obtain the photometric value of a subject.

A first aspect of the present invention is a photometric method for a video camera, which obtains a photometric value by integrating a video signal output from a solid-state electronic image pickup device within a photometric area defined within a photographing area. In the region, for each of the first number of horizontal scanning lines, the first integration processing is performed to integrate the video signal along the horizontal scanning line to obtain the first integrated value, and the obtained first integrated value Digitally converted to
Perform the first digital conversion process to obtain the integral data of
The first integration process and the first digital conversion process are repeatedly performed in the photometric area, and a plurality of obtained first integration data are added to obtain a first addition data,
It is determined whether or not the obtained value related to the first addition data is equal to or greater than a predetermined threshold value, and when it is determined to be equal to or greater than the threshold value, the first photometric value is calculated from the first addition data. However, when it is determined that the value is lower than the threshold value, the video signal is read again from the solid-state electronic image pickup device, and in the photometric region, for each of the second number of horizontal scanning lines, which is larger than the first number, The second integration process of integrating the video signal along the horizontal scanning line to obtain the second integration value is performed, and the obtained second integration value is digitally converted to obtain the second integration data. Digital conversion is performed, and the second integration process and the second digital conversion process are repeatedly performed in the photometric region, and a plurality of second integration data obtained are added to obtain second addition data. Second accrual day obtained From those for calculating the first photometric value.

When it is determined that the first photometric value is lower than the threshold value, the exposure condition is changed, and the video signal is read again from the solid-state electronic image pickup device to obtain the first photometric value. When it is impossible to change the exposure conditions, the second
It is preferable to obtain the photometric value of.

The first invention also provides a video camera. A first invention is a video camera which obtains a photometric value by integrating a video signal output from a solid-state electronic image pickup device in a photometric region defined in a photographing region, in which horizontal scanning is performed in the photometric region. Integrating means for integrating the video signal along the line and outputting a signal representing the integrated value,
An analog / digital converting means for digitally converting the signal representing the integrated value output from the integrating means and outputting integrated data, and an image along the horizontal scanning line for each of the first number of horizontal scanning lines in the integrating means. First control means for controlling the integration means and the analog / digital conversion means so that the integration processing for integrating the signal and the digital conversion processing in the analog / digital conversion means are repeatedly performed within the photometric region, and the first control means.
A first addition means for adding a plurality of integrated data obtained under the control of the control means to obtain first addition data, and a value related to the first addition data obtained by the first addition means. Determining means for determining whether or not is greater than or equal to a predetermined threshold, and the first addition data obtained by the first adding means in response to the determination by the determining means being greater than or equal to the threshold The first photometric value calculating means for calculating the first photometric value from the above, and the video signal is read again from the solid-state electronic image sensor in response to the judgment by the judging means that the value is lower than the threshold value, and For each of the second number of horizontal scanning lines, which is larger than the first number, in the photometric area, an integration process for integrating the video signal along the horizontal scanning lines and a digital conversion process in the analog / digital conversion means. So as to be repeatedly performed within the photometric region, the second control means for controlling the solid-state electronic image pickup device, the integration means, and the analog / digital conversion means, and the second control means. Second adding means for adding a plurality of integrated data to obtain second added data, and second calculating a second photometric value from the second added data obtained by the second adding means.
It is equipped with a photometric value calculation means.

In a preferred embodiment, the determining means is
When it is determined that the first photometric value is lower than the threshold value, the exposure condition is changed, and the first photometric value calculating means is caused to calculate the first photometric value again.

According to the present invention, it is determined whether the added data is equal to or more than the threshold value. If the subject is not of low brightness, the added data is equal to or higher than the threshold value, and the reliability of the digitally converted data by the analog / digital conversion circuit is high. Therefore, the first photometric value is calculated from the added data.

If the subject has low brightness, the addition data has a value lower than the threshold value. In this case, the second integration processing is performed for each of the second number of horizontal scanning lines, which is larger than the first number, to integrate the video signals along the horizontal scanning lines to obtain the second integrated value. . Since the number of horizontal scanning lines of the video signal to be integrated is large, the integrated value becomes large. The reliability of the integrated data obtained by the analog / digital conversion also becomes high. Addition data can be obtained from reliable integration data,
Since the second photometric value is obtained, the photometric accuracy is also high.

In this way, it is possible to measure a low-brightness subject on the basis of a video signal output from the solid-state electronic image pickup device without using a high-precision analog / digital conversion circuit.

The video camera of the first invention can be expressed as follows. That is, is a video camera that obtains a photometric value by integrating a video signal output from the solid-state electronic image pickup device in a photometric area defined in the shooting area. Integrating means for integrating a video signal along the line and outputting a signal representing the integrated value; analog / digital converting means for digitally converting the signal representing the integrated value output from the integrating means and outputting integrated data; For each of the first number of horizontal scanning lines, the integration means for integrating the video signal along the horizontal scanning line and the digital conversion processing by the analog / digital conversion means are repeatedly performed within the photometric area. First control means for controlling the analog / digital conversion means, and control of the first control means First addition means for obtaining a first addition data by adding the plurality of integrated data obtained, first obtained by the first addition means
A first photometric value calculating means for calculating a first photometric value from the addition data of, and for each second horizontal scanning line larger than the first number in the photometric area, along the horizontal scanning line. Second control means for controlling the integration means and the analog / digital conversion means so that the integration processing for integrating the video signal and the digital conversion processing in the analog / digital conversion means are repeatedly performed within the photometric region, Second addition means for obtaining a second addition data by adding a plurality of integration data obtained under the control of the second control means, from the second addition data obtained by the second addition means Second photometric value calculating means for calculating the second photometric value, and whether or not the first photometric value calculated by the first photometric value calculating means is greater than or equal to a predetermined threshold value. Based on the determination result in which includes a determination means for switching the first and the second photometric value calculating means.

A photometric method according to the second invention is a photometric method for a video camera, which obtains a photometric value by integrating a video signal output from a solid-state electronic image pickup device within a photometric area defined within a photographing area. In the photometric area, a first integration process is performed for each of the first number of horizontal scanning lines to obtain a first integrated value by integrating a video signal along the horizontal scanning line. A plurality of obtained values are obtained by performing a first digital conversion process for digitally converting the integrated value of to obtain the first integrated data, and repeatedly performing the first integration process and the first digital conversion process in the photometric region. The first integrated data is added to obtain the first added data, and in the photometric area, an image along the horizontal scanning line for each of the second number of horizontal scanning lines larger than the first number. Second integration processing to obtain the second integrated value by performing digital conversion of the obtained second integrated value to obtain the second integrated data. The second integration process and the second digital conversion process are repeatedly performed in the photometry area, and the plurality of second integration data obtained are added to obtain the second addition data, which relates to the first addition data. If the value is equal to or larger than a predetermined threshold value, the photometric value is calculated using the first addition data, and if the value related to the first addition data is lower than the predetermined threshold value, the first addition data is calculated. The photometric value is calculated using the addition data of 2.

The second invention also provides a video camera. A second invention is a video camera which obtains a photometric value by integrating a video signal output from a solid-state electronic image pickup device in a photometric area defined in a photographing area. For each number of horizontal scanning lines, a first integrating means for integrating a video signal along the horizontal scanning line to obtain a first integrated value, and a second integration number larger than the first number in the photometric area. For each horizontal scanning line of the number of, the second integration means for integrating the video signal along the horizontal scanning line to obtain the second integration value, and the first integration value output from the first integration means are Signal representing or second above
Analog-to-digital converting means for digitally converting the signal representing the second integrated value output from the integrating means, and outputting integrated data, a signal representing the first integrated value output from the first integrating means, or Switching means for selecting a signal representing the second integrated value output from the second integrating means and giving it to the analog / digital converting means, integrating processing in the first integrating means and in the second integrating means The integration process is repeatedly performed in the photometric area, the plurality of obtained integration data are added, and the first addition data and the second addition data are output, and the first output from the addition means. If the value related to the addition data is equal to or greater than the predetermined threshold value, the photometric value is calculated using the first addition data, and the first addition data is greater than the threshold value. Low when are those provided with a photometric value calculating means for calculating a photometric value using the second sum data.

According to the present invention, first addition data suitable for obtaining a photometric value of an object having a general brightness value and second addition data suitable for obtaining a photometric value of a low-luminance object. Is obtained. If the value related to the first added data is greater than or equal to a predetermined threshold value, the photometric value is calculated using the first added data, and the value related to the first added data is lower than the predetermined threshold value. Then the second
The photometric value is calculated using the added data of.

According to the present invention as well, a digital / analog conversion circuit having general accuracy can be used to measure a low-brightness subject with a video signal output from a solid-state electronic image pickup device.

A third invention is such that a first integral value is obtained based on a video signal obtained from the first field and a second integral value is obtained based on a video signal obtained from the second field. .

In the photometric method according to the third aspect of the present invention, the solid-state electronic image pickup device of the video camera provided with the solid-state image pickup device for outputting the video signals of the first field and the second field for one frame by the interlaced scanning is output. In the photometric method of the video camera for obtaining the photometric value by integrating the video signal of the first field within the photometric area defined in the shooting area, the video signal of the first field is For each number of horizontal scanning lines, a first integration process is performed to integrate a video signal along the horizontal scanning line to obtain a first integrated value, and the obtained first integrated value is digitally converted to a first integrated value. Performing the first digital conversion processing to obtain the integration data of and repeating the first integration processing and the first digital conversion processing in the photometry area. Then, a plurality of the obtained first integrated data are added to obtain the first added data, and the video signal of the second field has the second number larger than the first number in the photometric area. For each horizontal scan line,
The second integration process of integrating the video signal along the horizontal scanning line to obtain the second integration value is performed, and the obtained second integration value is digitally converted to obtain the second integration data. Digital conversion is performed, and the second integration processing and the second integration processing are performed.
Is repeatedly performed in the photometric area, a plurality of second integrated data obtained are added to obtain second added data, and the first added data is obtained and the second addition is performed. The process of obtaining data is performed simultaneously in one field or one frame, and if the value related to the first added data is equal to or greater than a predetermined threshold value, the photometric value is calculated using the first added data, and If the value related to the first addition data is lower than a predetermined threshold value, the photometric value is calculated using the second addition data.

The third invention also provides a video camera.

A video camera according to a third aspect of the present invention outputs from the solid-state electronic image pickup device of a video camera provided with a solid-state electronic image pickup device for outputting a video signal of a first field and a second field for one frame by interlaced scanning. In a video camera that obtains a photometric value by integrating the video signal to be measured in a photometric area defined in the shooting area, the video signal along the horizontal scanning line is integrated and integrated in the photometric area. Integrating means for outputting a signal indicating the above, digital / analog converting means for digitally converting the signal indicating the integrated value output from the above integrating means, and outputting integrated data; For each of the first number of horizontal scanning lines, an integration process for integrating the video signal along the horizontal scanning line, and the above Under the control of the first control means and the first control means for controlling the integration means and the analog / digital conversion means so that the digital conversion processing in the analog / digital conversion means is repeatedly performed in the photometric region. The first addition means for obtaining the first addition data by adding the plurality of integration data obtained in the above, and the video signal of the second field in the second field, which is larger than the first number in the photometry area, For each number of horizontal scanning lines, the integration means and the analog / digital conversion means for repeatedly performing the integration processing for integrating the video signal along the horizontal scanning line and the digital conversion processing in the analog / digital conversion means within the photometric area. Second control means for controlling the digital conversion means, and a plurality of control means obtained under the control of the second control means. The second adding means for adding the minute data to obtain the second added data, and the first addition data output from the first addition means if the value is equal to or more than a predetermined threshold value. To calculate the photometric value, and when the first added data is lower than the threshold value, the photometric value is calculated using the second added data output from the second adding means. It is equipped with a photometric value calculation means that

Based on the video signal of the first field among the video signals output from the solid-state electronic image pickup device, the first addition data suitable for obtaining the photometric value of the subject having a general brightness value can be obtained. . Based on the video signal of the second field, the second addition data suitable for obtaining the photometric value of the low-luminance subject is obtained. If the value related to the first added data is greater than or equal to a predetermined threshold value, the photometric value is calculated using the first added data, and the value related to the first added data is lower than the predetermined threshold value. Then, the photometric value is calculated using the second addition data.

Since the first field and the second field are temporally close to each other and have a high correlation, photometry can be performed using two kinds of data almost at the same time.

According to the present invention as well, a digital / analog conversion circuit having general accuracy can be used to measure a low-luminance object by a video signal output from a solid-state electronic image pickup device.

In the above, a luminance signal component is generally used as the video signal, and the luminance signal component does not have to be a strict luminance signal as long as it can be regarded as a luminance signal such as a G (green) signal. Further, the first field may be either an odd or even field and the second field may be the first field.
It need only be a field different from the field.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment in which the present invention is applied to a digital still camera will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram of a digital circuit of an embodiment of the present invention.
It is a block diagram which shows the electric constitution of a still camera.

A clock signal generation circuit (hereinafter referred to as CG) 1 includes a clock signal CLK, a horizontal transfer pulse H for driving the horizontal transfer path of the CCD 4, a substrate extraction pulse SUB for sweeping unnecessary charges, and an A field vertical transfer. A pulse VA and a B field vertical transfer pulse VB are generated. Further, CG1 generates a field index signal FI, an X timing signal XTM for strobe emission, and a horizontal synchronizing signal HD.

The clock signal CLK is given to a synchronizing signal generating circuit (hereinafter referred to as SSG) 2, and the SSG2 generates a horizontal synchronizing signal HD and a vertical synchronizing signal VD based on this clock signal CLK and gives it to CG1.

The horizontal transfer pulse H is given to the CCD (solid-state electronic image pickup device) 4, and the substrate extraction pulse SUB and the A field vertical transfer pulse VA are passed through the V driver 5.
The B field vertical transfer pulse VB is applied to the CCD 4 via the V driver 6.

The field index signal FI, the X timing signal XTM and the horizontal synchronizing signal HD are the CPU
Given to 3. A shutter enable signal TS indicating that the exposure condition has been set from the CPU 3 to the CG 1.
An electronic shutter control signal TS1 for starting exposure in EN and CCD 4 is applied.

In the CCD 4, the substrate extraction pulses SUB, A
By the field vertical transfer pulse VA, the B field vertical transfer pulse VB, and the horizontal transfer pulse H, interlaced shooting is performed, and video signals of the A field and the B field (color sequential signals of GRGB) are alternately generated every one field period. Are sequentially read. The driving of the CCD 4 (imaging and reading of a video signal) is performed at least at the time of photographing and in the photometric processing prior thereto.

The video signals of the A field and the B field output from the CCD 4 are given to a color separation circuit 8 through a correlated double sampling circuit (CDS) 7 and three primary colors representing a subject image, G (green), R ( Red) and B
It is separated into (blue) color signals.

The color signals G, R and B are subjected to color balance adjustment by a gain control circuit (hereinafter referred to as GCA) 9 and then gradation correction is performed by a gamma correction circuit 10 for clamping and resetting. Input to the sampling circuit 11.

The clamp and resampling circuit 11 has
The three color signals R, G, B are clamped and re-converted into GRGB color sequential signals by resampling. This color sequential signal is input to the gain control and blanking circuit 12. The gain control and blanking circuit 12 amplifies the color sequential signal to an appropriate level for recording and adds the blanking signal to it. The output signal of the circuit 12 is subsequently converted into digital image data by the A / D converter 13.

As will be described later in detail, prior to photographing, photometric processing and exposure control (control of iris and shutter speed) based on the photometric value are performed. This photometric processing is GCA9.
Based on the output signal of Shooting is performed after such photometric processing and exposure control. Then, the video signal obtained from the CCD 4 by photographing is the above-mentioned circuit 10, 1
It becomes digital image data through 1, 12 and 13 and is processed by Y / C separation, data compression, etc. by an image data processing circuit (not shown) and then recorded on a recording medium such as a memory card. Become.

For photometric processing, a YL combining circuit 14, a gate circuit 15, an integrating circuit 16 and an amplifying circuit 17 are provided. An example of a specific electrical configuration of these circuits is shown in FIG. The CPU 3 outputs a window signal WIND that controls the gate circuit 15 and a reset signal HLRST that resets the integration circuit 16. These signals WIND
The timing of HLRST will be described later. Further, in this embodiment, the CPU 3 has an A / D converter 18 built-in.

The color signals R, G and B output from the gain control circuit 9 are added by the YL synthesizing circuit 14,
Relatively low frequency luminance signal YL (hereinafter simply referred to as luminance signal YL
Is generated). The luminance signal YL passes through the gate circuit 15 while the window signal WIND is applied in the required horizontal scanning period. The integrating circuit 16 is reset when the reset signal HLRST is given,
After that, the luminance signal YL input from the gate circuit 15 is integrated. The integrated signal of the integrating circuit 16 is amplified by the amplifying circuit 17, and immediately before the integrating circuit 16 is reset, the A /
Converted to digital integral data by D converter 18,
It is taken in by the CPU 3. The reference voltage divisions V1 and V2 of the integrating circuit 16 and the amplifying circuit 17 give an appropriate offset thereto.

In the video camera, the reset timing of the integrating circuit 16 differs depending on the magnitude of the subject brightness. In the case of a subject having general brightness, the integrating circuit 16 is reset every one horizontal scanning period, but in the case of a low brightness subject, the integrating circuit 16 is reset in units of four horizontal scanning periods. Therefore, the output timing of the window signal WIND, the A / D conversion timing, the reset signal and the timing of addition to the memory also differ depending on the subject brightness.

The photometry in the video camera can be AV photometry for average photometry in the photographing area and SP photometry for partial photometry in the photographing area.

FIG. 3 shows the photometric area set in the photographing area of the CCD. The AV photometry area covers almost the entire shooting area, but the SP photometry area is set at the center of the shooting area where the main subject is likely to exist. Of course, it goes without saying that the SP metering area can be set to any location within the shooting area and to any width. AV photometry is performed in the A field, and SP photometry is performed in the B field.

FIG. 4 is a time chart showing the operation of the video camera when the integrating circuit is reset every one horizontal scanning period in AV photometry.

The photometric area is set over almost the entire photographing area. For this reason, the window signal WIND becomes H level every other horizontal scanning line during the almost same period as the H level of the horizontal synchronizing signal HD.

While the window signal WIND is given, the gate circuit 15 allows the input luminance signal YL to pass through, and the luminance signal YL is input to the integrating circuit 16.

The integrating circuit 16 has already been reset in the preceding field and integrates the luminance signal YL which has passed through the gate circuit 15 and is input. Window signal WIND
Becomes L level and the input of the luminance signal YL to the integrator circuit 16 is stopped, the integrated output of the integrator circuit 16 is held as it is and the integrated output of the integrator circuit 16 is incorporated in the A / D converter incorporated in the CPU 3. Converted to digital data by 18. After that, the integrating circuit 16 is reset by the horizontal line reset signal HLRST given from the CPU 3 to prepare for the next integrating operation.

A memory attached to the CPU 3 (for example, RA
The integrated data storage area of M) is cleared in synchronization with a predetermined horizontal synchronizing signal HD. The integrated value converted into digital data by the A / D converter 18 is added to the previous data (which is cleared in the first case and is zero) and stored in this integrated data storage area. .

The A / D conversion by the A / D converter 18, the reset of the integrating circuit 16 and the addition processing of the integrated data are performed in the next horizontal scanning period when the window signal WIND is output.

As described above, 1 in the photometry area
The luminance signal Y by the integrating circuit 16 is applied to the horizontal scanning line of the book.
Integration of L and A / D of integrated signal obtained by this integration
The conversion, the reset of the integrating circuit 16 and the addition of the integrated data to the memory are alternately repeated every horizontal scanning period. Then, this repetition is performed over the entire photometric area.

FIG. 5 is a time chart showing the operation of the video camera when the integrating circuit 16 is reset with four horizontal scanning periods as one unit.

The window signal WIND is continuously output for four horizontal scanning periods and is not output for one horizontal scanning period after the four horizontal scanning periods. This output form is repeated within one field. Window signal WIND is L
A / D conversion is performed while the level is
The reset signal HLRST is output and stored in the memory.

In the B field in which SP photometry is performed, a window signal having a pulse width of 10 μs is output every other horizontal scanning period after 31 μs has elapsed from the falling of the horizontal synchronizing signal HD. Details of SP photometry are omitted in this embodiment.

FIG. 6 shows the overall operation of the photometric processing performed by the CPU 3.

The CPU 3 initializes the exposure condition when starting the photometric processing, and controls at least one of the iris and the electronic shutter so that the initial exposure condition is realized (step 31). As the initial exposure condition, a statistically most possible exposure condition, for example, an exposure amount Ev = 10 (aperture F4, shutter speed 1/60 seconds, or aperture F2, shutter speed 1/125 seconds) is preferable.

1 is set as the integrated number of horizontal scanning lines to be integrated (step 32). Clear to CCD4
A pulse is applied to sweep out unnecessary charges, and the CCD 4 is exposed. When the signal charges are accumulated in the CCD 4, the reading of the video signal from the CCD 4 is started (step 33).

In the horizontal scanning period within the photometric area, the window signal WIND is output as described above, and the integrating circuit 16 performs the integrating operation during the photometric period in one horizontal scanning period (step 34). When the integration of the photometric period within one horizontal scanning period is completed, the integrated line number is decremented (step 35), and it is determined whether the integrated line number has become 0 (step 36). If the integrated line number is not 0, the processing from step 34 to step 36 is continued until it becomes 0.

In the initial operation, the number of integrated lines is set to 1, so that the number of integrated lines becomes 0 by decrementing (YES in step 36). When the number of integrated lines becomes 0, the luminance signal component integrated by the integrating circuit 16 is given to the A / D converter 18 and converted into digital data (step 37). The luminance signal component is digital
By being converted into data, the reset signal HLRS
T is output and the integrating circuit 16 is reset.

Whether or not the data for all one field has been obtained is determined by the number of horizontal scanning lines, for example (step 39). If the data for all one field has not been obtained, the processing from step 34 to step 39 is repeated.

When the integrated data from the integrating circuit 16 is obtained every other horizontal scanning line for all the one field, the brightness value calculation is performed (step 40). By the brightness value calculation, appropriate weighting is performed corresponding to the position of the field of the obtained data, and the brightness data of one field is obtained. Further, the brightness data for one horizontal scanning line is calculated from this brightness data.

It is judged whether or not the luminance data for one horizontal scanning line is within a predetermined specified range (step 41). If it is within the specified range, it is considered that the subject has a general brightness, and the photometric processing is terminated (YES in step 41). If it is not within the specified range, it is generally considered to be a low-brightness subject. Therefore, the exposure condition is changed. The shutter speed is changed to change the exposure condition, and the shutter speed is set to be slow (steps 42 and 43). The processing from steps 34 to 41 is performed again by changing the shutter speed.

When the shutter speed has already been set to the lowest speed, the integrated line number is set to 4 (steps 44 and 45). If the total number of lines has already been set to 4, it is judged to be outside the photometric range, and the process ends (step 46).

If the total number of lines is not set to 4, the total number of lines is set to 4 (steps 44, 4).
Five).

When the total number of lines is set to 4, FIG.
As shown in (4), the window signal WIND is output in the four continuous horizontal scanning lines and sequentially integrated by the integrating circuit 16 (steps 34 to 36). When the integration for four horizontal scanning periods is completed, A is calculated in the next horizontal scanning period.
/ D conversion is performed (step 37). When the A / D conversion is completed and the digital data of the luminance signal component is stored in the memory, the integrating circuit 16 is reset (step 38).

When the continuous integration of four horizontal scanning periods is completed for one field (YES in step 39), the brightness value calculation process is performed (step 40). In this way, the photometric processing is completed.

When the digitally converted integral data is not reliable because of a low-luminance object, the range of the horizontal scanning line to be integrated is widened, so that the value of the integrated signal input to the A / D converter 18 becomes large. Therefore, A /
Even with the D converter 18, reliable digital integration data can be obtained, and photometry of a low-luminance object can be performed.

FIG. 7 shows the range of subject brightness values that can be detected as described above.

When the number of integrated lines is 1, it is possible to perform photometry for luminance values of 8 to 12 Ev. Photometry is not possible for a subject having a brightness value of 8 Ev or less. In the case of a subject having a luminance value of 8 Ev or less, the photometric processing is performed by setting the number of integrated lines to 4 and integrating the luminance signal components of four horizontal scanning lines as described above. This allows photometry for luminance values of 6 to 10 Ev. In this way A / D
The dynamic range of the converter 18 will be expanded in a pseudo manner.

FIG. 8 is a time chart showing another operation of the video camera.

In this operation, the number of integrated lines is set to 1 in the A field, the luminance signal components are integrated and A / D converted every other horizontal scanning line, and the CPU 3
Taken into memory. In the B field, the number of integrated lines is set to 4, the luminance signal components are continuously integrated for four horizontal scanning lines, and the integrated luminance signal components for the four horizontal scanning lines are A / D converted and stored in the memory of the CPU 3. Is taken into. Therefore, both the A field and the B field are AV photometry, and SP photometry is not performed.

It is possible to measure the subject brightness of 8 to 12 Ev from the video signal of the A field, and to measure the subject brightness of 6 to 10 Ev from the video signal of the B field. Since the fields are close in time and have a high correlation, the photometric values of the subject at approximately the same time can be obtained.

FIG. 9 shows still another embodiment and is a block diagram showing the electrical construction of the video camera. In the circuit shown in FIG. 8, the same parts as those in the circuit shown in FIG.

In the video camera shown in FIG. 9, two gate circuits and two integrator circuits are connected, and the output of the integrator circuit is an amplifier circuit via a switch circuit 27 or 28.
Given to 17.

In the video camera shown in FIG. 9, the gate circuit 15, the integration circuit 16, and the switch circuit 28 (one-line integration system) integrate the luminance signal component every other horizontal scanning line, perform A / D conversion, and store a memory. Gate circuit 25, integrator circuit 26 and switch circuit 27 (4-line integration system) are used for integration of four horizontal scanning line luminance signal components, A / D conversion, and incorporation into memory. Used.

FIG. 10 is a time chart showing the operation of the video camera shown in FIG.

From the CPU 3, a first window signal WIND1 for controlling the gate circuit 15, a second window signal WIND for controlling the gate circuit 25, a first reset signal HLRST for resetting the integrating circuit 16, and an integrating circuit 26.
Second reset signal HLRST2 for resetting the first switch control signal SW for resetting switch circuit 28
1, and a second switch control signal SW2 for controlling the switch circuit 27 is output.

The operation of the one-line integration system is the same as the operation represented by the time chart shown in FIG. 4, and the switch control signal S for controlling the ON / OFF of the switch circuit 28 is used.
The difference is that W1 and SW2 are added.

The gate circuit 15 receives the first window signal WI
ND1 turns on every other horizontal scanning line within the photometric area of one horizontal scanning period. In the horizontal scanning period of the horizontal scanning line next to the horizontal scanning line in which the gate circuit 15 is turned on, the luminance signal component is integrated by the integrating circuit 16 and turned on by the switch circuit 28 to be given to the amplifier circuit 17.
The luminance signal component amplified in the amplifier circuit 17 is A / D converted and taken into the memory. The first switch control signal SW1 for turning on the switch circuit 28 is output in the first half of the horizontal scanning period so as not to overlap with the acquisition of the signal of the 4-line integration system.

The operation of the 4-line integration system is the same as the operation represented by the time chart shown in FIG. 5, except that a control signal for controlling on / off of the switch circuit 27 is added.

The gate circuit 25 receives the second window signal WI.
ND2 turns on four horizontal scanning lines in succession within the photometric area of one horizontal scanning period. In the horizontal scanning period of the horizontal scanning line next to the continuous four horizontal scanning lines in which the gate circuit 25 is turned on, the luminance signal component is integrated by the integrating circuit 26 and the switch circuit 27 is turned on, so that the amplifier circuit 17 is turned on.
Given to. The luminance signal component amplified in the amplifier circuit 17 is A / D converted and taken into the memory. The first switch control signal SW1 for turning on the switch circuit 27 is output in the latter half of the horizontal scanning period so as not to overlap with the acquisition of the signal of the one-line integration system.

As shown in FIG. 9, by connecting both a 1-line integration system circuit and a 4-line integration system circuit to the video camera, the luminance signal component is obtained for each horizontal scanning line. It becomes possible to simultaneously measure the measured photometric value and the measured photometric value obtained by integrating the luminance signal components for four continuous horizontal scanning lines.

FIG. 11 is a table when subject brightness is estimated from the data of the 1-line integration system and the data of the 4-line integration system obtained by the video camera shown in FIG.

If both the data of the 1-line integration system and the data of the 4-line integration system are larger than the range where the photometric accuracy shown in FIG. 6 can be obtained, it is determined that photometry is impossible because the subject has high brightness. .

If both the data of the 1-line system and the data of the 4-line integration system are smaller than the range in which the photometric accuracy shown in FIG. 7 can be obtained, it is determined that photometry is impossible because the subject has low brightness.

When the data of the 1-line integration system is in the range where the photometric accuracy is obtained, and when the data of the 4-line integration system is larger than the range where the photometric accuracy is obtained, the subject brightness is 10 to 12 Ev.
It is estimated to be.

When the data of the 1-line integration system is lower than the range in which the measurement accuracy is obtained and the data of the 4-line integration system is higher than the range in which the photometric accuracy is obtained (* 1 in FIG. 11), The data shows that the subject brightness value is 10 Ev or more, and the data of the one-line integration system shows that the subject brightness value is 8 Ev or less. This does not occur when the level of the luminance signal component in all the horizontal scanning lines is low, but can occur when the level of the luminance signal component of some horizontal scanning lines is high and the horizontal scanning line in which the level of the luminance signal component is low is mixed. In this case, when all the luminance signal components on the four horizontal scanning lines are low, re-photometry is performed as a photometry error.

When the level of the data of the 1-line integration system is higher than the range where the photometric accuracy is obtained and the level of the data of the 4-line integration system is within the range where the photometric accuracy is obtained (* 2 in FIG. 11), The data of the 4-line integration system shows that the subject brightness value is 6 to 10 Ev, and the data of the 1-line integration system shows that the subject brightness value is 12 Ev or more. This does not occur when the level of the luminance signal component in all the horizontal scanning lines is high, but may occur when the level of the luminance signal component of some horizontal scanning lines is low and the level of the luminance signal component is high in a mixture with the horizontal scanning line. In this case, when all the luminance signal components on the four horizontal scanning lines are high, re-photometry is performed as a photometry error.

If both the data of the 1-line integration system and the data of the 4-line integration system are within the range where the photometric accuracy is obtained, the subject brightness is estimated to be 8 to 10 Ev. If the data of the 1-line integration system is lower than the range where the photometric accuracy is obtained and the data of the 4-line integration system is within the range where the photometric accuracy is obtained,
Subject brightness is estimated to be 6-8 Ev.

When the data of the 1-line integration system is higher than the range where the photometric accuracy is obtained and the data of the 4-line integration system is lower than the range where the photometric accuracy is obtained (* 3 in FIG. 11), The data shows that the subject brightness is 6 Ev or less, and the data of the 4-line integration system shows that the subject brightness is 12 Ev or more. This does not occur when the level of the luminance signal component in all the horizontal scanning lines is low, but can occur when the level of the luminance signal component of some horizontal scanning lines is high and the horizontal scanning line in which the level of the luminance signal component is low is mixed.
In this case, when all the luminance signal components on the four horizontal scanning lines are low, re-photometry is performed as a photometry error.

When the data of the 1-line integration system is within the range where the photometric accuracy is obtained and the data of the 4-line integration system is lower than the range where the photometric accuracy is obtained (* 4 in FIG. 11), 4 lines are used. The integration system data indicates that the subject brightness is 6 Ev or less, and the 1-line integration system data indicates that the subject brightness is 8 to 12 Ev.

In the video camera shown in FIG. 9, switch circuits 27 and 28 are provided to control the select signals so that they do not overlap each other.
If the A / D converter and the dedicated A / D converter for the 4-line integration system are provided, the switch circuits 27 and 28 become unnecessary.

Further, the video camera of FIG. 9 is provided with two integrating circuits 15 and 25 to obtain data of the 1-line integrating system and the 4-line integrating system, but more integrating circuits are provided,
It is also possible to obtain data by changing the number of integrated lines of a plurality of types of horizontal scanning lines.

[Brief description of drawings]

FIG. 1 is a block diagram of a digital still camera according to an embodiment of the present invention.
It is a block diagram which shows the electric constitution of a video camera.

2 is a circuit diagram showing a more specific electrical configuration of a circuit portion required for photometry in the digital still video camera of FIG.

FIG. 3 shows a photometric area set within a shooting area.

FIG. 4 is a time chart for obtaining photometric data of a 1-line integration system.

FIG. 5 is a time chart for obtaining photometric data of a 4-line integration system.

FIG. 6 is a flowchart showing a procedure of photometric processing by a CPU.

FIG. 7 shows a relationship between a subject brightness value and integrated data.

FIG. 8: Performs one-line integration in the A field,
It is a time chart at the time of performing 4-line integration in B field and obtaining photometric data.

FIG. 9 shows another embodiment of a digital still camera.
It is a block diagram which shows the electric constitution of a video camera.

10 is a time chart in the case of performing photometry in the video camera shown in FIG.

FIG. 11 is a table showing the relationship between integrated data and subject brightness values.

[Explanation of symbols]

3 CPU (control means) 4 CCD (solid-state electronic image sensor) 14 YL synthesis circuit 15, 25 gate circuit 16, 26 Integrator circuit 17 Amplifier circuit 18 A / D converter 27, 28 switch circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-32173 (JP, A) JP-A-4-127673 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04N 5/225-5/247

Claims (9)

(57) [Claims] 1. A photometric method for a video camera, which obtains a photometric value by integrating a video signal output from a solid-state electronic image sensor in a photometric area defined in a photographing area, wherein: For each of the first number of horizontal scanning lines, the first integration process of integrating the video signal along the horizontal scanning line to obtain the first integrated value is performed, and the obtained first integrated value is digitally converted. A first digital conversion process for obtaining first integrated data is performed, and the first integration process and the first digital conversion process are repeatedly performed in the photometric region to obtain a plurality of obtained first integrated data. The first addition data is obtained by addition, and it is determined whether or not the value relating to the obtained first addition data is greater than or equal to a predetermined threshold value. The first photometric value is calculated from the added data, and when it is determined that the value is lower than the threshold value, the video signal is read out again from the solid-state electronic image pickup device, and the first photometric value larger than the first number is read in the photometric area. For every two horizontal scanning lines, a second integration process is performed to integrate a video signal along the horizontal scanning line to obtain a second integrated value, and the obtained second integrated value is digitally converted. A second digital conversion for obtaining second integrated data is performed, and the second integration processing and the second digital conversion processing are repeatedly performed in the photometric region, and a plurality of obtained second integration data are added. Then, the second addition data is obtained, and the first photometry value is calculated from the obtained second addition data. 2. The exposure condition is changed when it is determined that the first photometric value is lower than the threshold value, and the video signal is read again from the solid-state electronic image pickup device to determine the first photometric value. The photometric method for a video camera according to claim 1, wherein the second photometric value is determined when the exposure condition cannot be changed. 3. A photometric method of a video camera, which obtains a photometric value by integrating a video signal output from a solid-state electronic image pickup device within a photometric area defined within a photographing area, wherein: For each of the first number of horizontal scanning lines, the first integration process of integrating the video signal along the horizontal scanning line to obtain the first integrated value is performed, and the obtained first integrated value is digitally converted. A first digital conversion process for obtaining first integrated data is performed, and the first integration process and the first digital conversion process are repeatedly performed in the photometric region to obtain a plurality of obtained first integrated data. Addition is performed to obtain the first addition data, and in the photometric area, for each of the second number of horizontal scanning lines larger than the first number, the video signal along the horizontal scanning line is integrated to obtain the second added data. Integral of The second integration process is performed to obtain the second integration data, and the second integration process is performed to obtain the second integration data. The conversion process is repeated in the photometric area, the plurality of second integrated data obtained are added to obtain the second added data, and the value related to the first added data is equal to or greater than a predetermined threshold value. If so, the photometric value is calculated using the first addition data, and if the value related to the first addition data is lower than a predetermined threshold value, the photometric value is calculated using the second addition data. How to calculate the photometry of a video camera. 4. A video signal output from the solid-state electronic image pickup device of a video camera having a solid-state electronic image pickup device for outputting a video signal of a first field and a second field for one frame by interlaced scanning, In the photometric method of the video camera for obtaining the photometric value by integrating within the photometric area defined in the above, for the video signal of the first field, in the above-mentioned photometric area, for each first number of horizontal scanning lines. A first integrated value obtained by integrating a video signal along the horizontal scanning line
Is performed, and the obtained first integrated value is digitally converted to obtain first integrated data. First digital conversion processing is performed, and the first integration processing and the first digital conversion processing are performed as described above. Repeatedly in the photometric area, the plurality of first integrated data obtained are added to obtain the first added data. Regarding the video signal of the second field, in the photometric area, from the first number The second integration processing is performed for every second horizontal scanning line having a large number of lines, and the video signal along the horizontal scanning line is integrated to obtain a second integrated value, and the obtained second integrated value is digitalized. A second digital conversion is performed to obtain the second integrated data, and the second integration processing and the second digital conversion processing are repeatedly performed in the photometric region to obtain a plurality of second integrations. Day Is added to obtain the second addition data, the process of obtaining the first addition data and the process of obtaining the second addition data are simultaneously performed in one field or one frame, and a value related to the first addition data is obtained. Is greater than or equal to a predetermined threshold value, the photometric value is calculated using the first addition data, and if the value relating to the first addition data is lower than the predetermined threshold value, the second A photometric method of a video camera that calculates the photometric value using the added data of. 5. A video camera for obtaining a photometric value by integrating a video signal output from a solid-state electronic image pickup device in a photometric area defined in a photographing area, wherein a horizontal scanning line is provided in the photometric area. Means for integrating a video signal along the line and outputting a signal representing the integrated value, an analog / digital converting means for digitally converting the signal representing the integrated value output from the integrating means, and outputting integrated data, the integrating means At the first number of horizontal scan lines,
A first control means for controlling the integration means and the analog / digital conversion means so that the integration processing for integrating the video signal along the horizontal scanning line and the digital conversion processing by the analog / digital conversion means are repeatedly performed within the photometric region. Control means, first addition means for adding a plurality of integrated data obtained under the control of the first control means to obtain first addition data, and the first addition means. Determination means for determining whether or not the value related to the first addition data is greater than or equal to a predetermined threshold value, and obtained by the first addition means in response to determination by the determination means as being greater than or equal to the threshold value. First photometric value calculating means for calculating a first photometric value from the obtained first added data, and the judgment means judges that the value is lower than the threshold value. Accordingly, the video signal is read again from the solid-state electronic image pickup device, and the video signal along the horizontal scanning line is integrated for each of the second number of horizontal scanning lines larger than the first number in the photometric region. Second control means for controlling the solid-state electronic image pickup device, the integrating means, and the analog / digital converting means so that the integrating processing and the digital converting processing in the analog / digital converting means are repeatedly performed in the photometric region. Second addition means for obtaining a second addition data by adding a plurality of integral data obtained under the control of the second control means, second addition data obtained by the second addition means A video camera equipped with a second photometric value calculating means for calculating the second photometric value from. 6. A video camera for obtaining a photometric value by integrating a video signal output from a solid-state electronic image pickup device within a photometric region defined within a photographing region, wherein a horizontal scanning line is provided within the photometric region. Means for integrating a video signal along the line and outputting a signal representing the integrated value, an analog / digital converting means for digitally converting the signal representing the integrated value output from the integrating means, and outputting integrated data, the integrating means At the first number of horizontal scan lines,
A first control means for controlling the integration means and the analog / digital conversion means so that the integration processing for integrating the video signal along the horizontal scanning line and the digital conversion processing by the analog / digital conversion means are repeatedly performed within the photometric region. Control means, first addition means for adding a plurality of integrated data obtained under the control of the first control means to obtain first addition data, and the first addition means. A first photometric value calculating means for calculating a first photometric value from the first added data; and a second photometric value larger than the first number in the photometric area.
For each horizontal scanning line, the integration means and the analog means are arranged so that the integration processing for integrating the video signal along the horizontal scanning line and the digital conversion processing in the analog / digital conversion means are repeated within the photometric area. Second control means for controlling the digital / digital converting means, second adding means for adding a plurality of integrated data obtained under the control of the second controlling means to obtain second added data, The second photometric value calculating means for calculating the second photometric value from the second added data obtained by the second adding means, and the first photometric value calculated by the first photometric value calculating means are A video camera, comprising: a judgment means for judging whether or not it is equal to or more than a predetermined threshold value, and switching between the first and second photometric value calculation means based on the judgment result. 7. The determining means changes the exposure condition when it is determined that the first photometric value is lower than the threshold value, and the first photometric value calculating means again determines the first photometric value. The video camera according to claim 5 or 6, wherein the video camera is calculated. 8. A video camera which obtains a photometric value by integrating a video signal output from a solid-state electronic image pickup device within a photometric region defined within a photographing region, wherein First integrating means for obtaining a first integrated value by integrating a video signal along the horizontal scanning line for each number of horizontal scanning lines; and a second integration unit which is larger than the first number in the photometric region. Second integration means for obtaining a second integration value by integrating the video signal along the horizontal scanning line for each number of horizontal scanning lines, and representing the first integration value output from the first integration means. A signal or an analog / digital conversion means for digitally converting a signal representing the second integrated value output from the second integration means and outputting integrated data; a first integration output from the first integration means A belief representing a value Alternatively, switching means for selecting a signal representing the second integrated value output from the second integrating means and giving it to the analog / digital converting means, integrating processing in the first integrating means and second integrating means Is repeatedly performed in the photometric region, and a plurality of obtained integration data are added to obtain the first
Means for outputting the addition data and the second addition data, and if the value related to the first addition data output from the addition means is equal to or greater than a predetermined threshold value, photometry is performed using the first addition data. A video camera comprising a photometric value calculating means for calculating a value and calculating a photometric value using the second added data when the first added data is lower than the threshold value. 9. A video signal output from the solid-state electronic image pickup device of a video camera having a solid-state electronic image pickup device for outputting a video signal of a first field and a second field for one frame by interlaced scanning, In a video camera that obtains a photometric value by integrating within a photometric area defined within, an integrating means for integrating a video signal along a horizontal scanning line within the photometric area and outputting a signal representing the integrated value. , An analog / digital converting means for digitally converting the signal representing the integrated value output from the integrating means and outputting integrated data; for the video signal of the first field, the integrating means includes a first number of horizontal scanning lines. The integration processing for integrating the video signal along the horizontal scanning line and the analog / digital conversion means First control means for controlling the integration means and the analog / digital conversion means so that the digital conversion processing in the photometric region is repeatedly performed, and a plurality of control means are obtained under the control of the first control means. The first adding means for adding the integrated data of 1 to obtain the first added data, and for the video signal of the second field, the second number of horizontal scanning lines larger than the first number in the photometric area. For each time, the integration means and the analog / digital conversion means are controlled so that the integration processing for integrating the video signal along the horizontal scanning line and the digital conversion processing in the analog / digital conversion means are repeatedly performed in the photometric region. Second control means for adding a plurality of integration data obtained under the control of the second control means If the value relating to the first addition data output from the second addition means for obtaining the data and the first addition means is greater than or equal to a predetermined threshold value, the photometric value is calculated using the first addition data. And a photometric value calculation means for calculating a photometric value using the second addition data output from the second addition means when the first addition data is lower than the threshold value. Video camera.