JP2002033954A - Imaging device and its control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set an image signal to an appropriate level which is obtained by imaging, without having to use using diaphragms. SOLUTION: There is no diaphragm for the imaging device. A peak is detected at each vertical scanning period with a peak detection circuit 17. The peak value is given to a control device 20 and required control out of the control of the shutter speed of a shutter control circuit 19, the gain control of a preamplifier circuit 13, and the gain control of a GCA 16 is made according to the difference between an appropriate level and a peak value, thus making an adjustment, so that the level of an image signal obtained by imaging can attain appropriate level, without the control of the diaphragm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an imaging device such as an electronic still camera and a video camera used in a presentation system, and a control method therefor.

[0002]

2. Description of the Related Art In an image pickup apparatus typified by an electronic still camera for photographing a subject and recording a video signal representing the subject image on a recording medium, exposure control is required to obtain a video signal of an appropriate level. The exposure control is generally performed by controlling the shutter and controlling the aperture.

[0003] However, a drive circuit such as a drive motor is required to control the aperture, resulting in an increase in cost and an increase in circuit scale. Also, software for aperture control must be developed.

[0004]

DISCLOSURE OF THE INVENTION It is an object of the present invention to enable a video signal of an appropriate level to be obtained without controlling the aperture.

According to a first aspect of the present invention, there is provided an image pickup device, wherein a shutter speed is variable, an image of a subject is taken under exposure by the shutter means, and a video signal representing a subject image is output. Amplifying means for amplifying a video signal to be output, a peak detection circuit for detecting a peak of the video signal output from the imaging means, an average level detection circuit for detecting an average level of the video signal output from the imaging means, First level difference detecting means for detecting a first peak level difference between a peak level obtained by a detection circuit and an appropriate peak level, and the shutter means so as to reduce the first peak level difference. Shutter control means for controlling, the peak level obtained by the peak detection circuit and the average level obtained by the average level detection means. The second level difference detecting means for detecting a second level difference from the video signal, and the second level difference detected by the second level difference detecting means are used as a basis for adjusting the level of the video signal to an average level. If it exceeds the reference value for discriminating whether to place it at the peak level, make sure that the average level approaches the appropriate average level.
When the shutter control of the shutter means or the gain control of the amplifying means is performed and the second level difference detected by the second level difference detecting means is equal to or less than the reference value, at least the peak level is adjusted to the appropriate peak level.・
A control means for controlling the shutter of the shutter means or controlling the gain of the amplifying means so as to approach the level is provided.

According to a first aspect of the present invention, there is provided a control method of an image pickup apparatus, comprising: shutter means having a variable shutter speed; an image pickup element for photographing a subject under exposure by the shutter means; and outputting a video signal representing a subject image; In an image pickup apparatus provided with an amplifier circuit for amplifying a video signal output from an image sensor, a peak value of a video signal output from the image sensor is obtained.
Level and average level are detected.
A first peak level difference between the level and the proper peak level and a second level difference between the detected peak level and the detected average level are detected, and the first peak level difference is reduced. Controlling the shutter speed of the shutter means so that the second level difference exceeds a reference value for discriminating whether to base the adjustment of the level of the video signal on the average level or on the peak level. The shutter speed of the shutter means or the gain control of the amplifier circuit is performed so that the average level approaches the appropriate average level. When the average level is equal to or less than the reference value, at least the peak level is adjusted to the appropriate peak level. , The shutter speed control or the gain control is performed.

The fact that the second level difference exceeds the reference value means that an image obtained by photographing has an extremely bright spot, and the peak level is much higher than the average level. I do. In this case, if the gain or the like of the amplifier circuit is controlled so that the peak level falls within the dynamic range of the circuit, the average level of the video signal becomes considerably low (for example, less than half the range).

[0008] The reference value is preferably set in such a manner that the level of the video signal is adjusted based on the average value.
Level (or weighted average of peak level and average)
This is a criterion for dividing into a preferable form based on the above, and can be determined by trial and error based on experience, experiments, and the like.

[0009] If there is an extremely bright portion in a part of the subject, the peak level becomes prominent. Therefore, if the level of the video signal is adjusted based on the peak level,
The entire captured image may be dark.

According to the first aspect, the second level difference is detected, and when the second level difference is large, it is determined that there is an extremely bright portion in a part of the subject.
Control of the shutter speed or gain control of the amplifier circuit is performed based on the average level. Therefore, even if there is an extremely bright portion in a part of the subject, a photographed image having almost appropriate brightness can be obtained as a whole and on average.

Two cascaded amplifier circuits are provided, and when the difference between the average level and the proper average level or the difference between the peak level and the proper peak level is large, the gain control of the preceding amplifier circuit is performed. It is preferable that the video signal level be finely adjusted by a later-stage amplifier circuit.

As a result, the level can be adjusted with relatively high accuracy.

According to a second aspect of the present invention, there is provided a shutter means having a variable shutter speed, an imaging means for photographing a subject under exposure by the shutter means, and outputting a video signal representing a subject image, and a video output from the imaging means. Amplifying means for amplifying the signal, a peak detection circuit for detecting a peak of the video signal output from the imaging means, an average level detection circuit for detecting the average level of the video signal output from the imaging means, and the peak detection circuit Level difference detecting means for detecting the level difference between the obtained peak level and the average level obtained by the average level detecting circuit, and the level difference detected by the level difference detecting means form the basis of the level adjustment of the video signal. If it exceeds the reference value for discriminating whether to place at the average level or at the peak level, the average level It is to approach the proper average level, characterized in that it comprises a control means for performing shutter control or gain control of the amplifier means of said shutter means.

According to a second aspect of the present invention, there is provided a method of controlling an image pickup apparatus, comprising: shutter means having a variable shutter speed; an image pickup element for photographing a subject under exposure by the shutter means; and outputting a video signal representing a subject image; In an image pickup apparatus provided with an amplifier circuit for amplifying a video signal output from an image sensor, a peak value of a video signal output from the image sensor is obtained.
The level and the average level are detected, and the level difference between the detected peak level and the average level is detected. The second level difference is based on the level adjustment of the video signal based on the average level or the peak level. When a reference value for discriminating whether to place the shutter is exceeded, shutter speed control of the shutter means or gain control of the amplifier circuit is performed so that the average level approaches an appropriate average level.

According to the second aspect, the level difference is detected, and when the level difference exceeds the reference value, it is determined that there is an extremely bright part in a part of the subject, and therefore, based on the average level. Control of the shutter speed or gain control of the amplifier circuit. Also in the third aspect, even if there is an extremely bright portion in a part of the subject, a photographed image having almost appropriate brightness as a whole can be obtained.

In the above, the present invention may be applied to a device for illuminating a subject and obtaining an image of the subject under illumination.

When the subject is illuminated, the brightness of the subject increases.
Although the brightness of the subject changes depending on the illumination used, even in such a case, the video signal can be set to an appropriate level even in such a case.

According to a third aspect of the present invention, there is provided an image pickup apparatus, wherein the shutter speed is variable, the image pickup means shoots a subject under exposure by the shutter means, and outputs a video signal representing a subject image. Amplifying means for amplifying a video signal to be output, a peak detection circuit for detecting a peak of the video signal output from the imaging means, an average level detection circuit for detecting an average level of the video signal output from the imaging means, The ratio of the average level increases as the level difference between the peak level detected by the detection circuit and the average level detected by the average level detection circuit increases, and the ratio of the average level decreases as the level difference decreases. Weighting ratio determining means for determining the weighting ratio, and using the weighting ratio determined by the weighting ratio determining means, Weighted average level calculating means for calculating a weighted average level of the peak level and the average level,
And control means for performing shutter control of the shutter means or gain control of the amplifying means so that the weighted average level calculated by the weighted average level calculation means approaches an appropriate weighted average level. .

According to a third aspect of the present invention, there is provided a control method of an image pickup apparatus, comprising: shutter means having a variable shutter speed; an image pickup element for photographing a subject under exposure by the shutter means; and outputting a video signal representing a subject image; In an image pickup apparatus provided with an amplifier circuit for amplifying a video signal output from an image sensor, a peak value of a video signal output from the image sensor is obtained.
The level and the average level are detected. The larger the level difference between the detected peak level and the average level is, the larger the ratio of the average level is, and the smaller the level difference is, the smaller the ratio of the average level is. Determining a weighting ratio, calculating a weighted average level of the peak level and the average level based on the determined weighting ratio, and controlling the shutter of the shutter means so that the calculated weighted average level approaches an appropriate weighted average level. It is characterized in that speed control or gain control of the amplifier circuit is performed.

According to the third aspect, the weighting ratio is determined from the peak level and the average level. The weighting ratio is such that when the subject is bright as a whole and the difference between the peak level and the average level is small, there is an extremely bright part in the part of the subject so that the weight of the average level and the weight of the peak level are equal. When the peak level is prominent and the difference between the peak level and the average level is large, the weight of the average level is determined to be large.

A weighting ratio is determined according to the distribution of brightness in the subject, a weighted average level is calculated using the determined weighting ratio, and a shutter control or a gain control of an amplifier circuit is performed based on the calculated weighted average level. Is performed. Therefore, a subject having relatively appropriate brightness can be obtained regardless of the situation of the subject.

Two cascaded amplifier circuits are provided, and when the difference between the weighted average level and the appropriate weighted average level is large, gain control of the preceding amplifier circuit is performed, and fine adjustment of the video signal level is performed by the latter amplifier circuit. Is preferably performed.

The presentation system is a system in which a manuscript (including a negative film or the like) is photographed by an image pickup device, and the obtained video signal is supplied to a CRT display device or a TV projector to be enlarged and displayed. In an imaging device in such a presentation system,
The position where the document is placed is predetermined, and therefore, the distance from the imaging device to the subject is often fixed. Therefore, with the aperture fixed,
Alternatively, no serious problem arises even if the depth of field becomes shallow by not providing a stop. Therefore, the aperture control can be omitted, and the present invention is particularly useful in such a system.

[0024]

FIG. 1 shows a first embodiment of the present invention. FIG. 1 is a block diagram showing an electrical configuration of an image pickup apparatus for picking up an image of a document and outputting a video signal representing an image obtained by the image pickup. It is.

The operation of the imaging device is controlled by the control device 20.

The image pickup apparatus includes a CCD 11, and its electronic shutter operation is performed by controlling the timing and the time for starting accumulation of electric charges in the CCD 11. The control of the start timing and the storage time of charge accumulation in the CCD 11 is performed by a shutter control circuit 19.
Further, the imaging apparatus includes a preamplifier circuit 13 and a GCA (gain controlled amplifier) 16, and in these amplifier circuits, an input video signal is amplified by a gain corresponding to a given gain control signal. Is done. The gain control signal applied to the preamplifier circuit 13 is mainly operated when the level of the input video signal is relatively changed, and the gain control signal applied to the GCA 16 finely adjusts the level of the input video signal. Be operated when you.

The imaging device has a lighting device 22. When the brightness of the subject is low, the subject to be photographed is illuminated by the lighting device 22.

The image pickup apparatus shown in FIG. 1 is not provided with an aperture, and the image signal is adjusted to an appropriate level by controlling the electronic shutter speed of the CCD 11 and adjusting the level of the image signal using the preamplifier circuit 13 and the GCA 16. , Thereby achieving exposure control. In particular, when the subject is illuminated using the illumination device 22, the exposure is likely to be over-exposed, but the video signal is adjusted to an appropriate level by the necessary control of the shutter speed and the gain control.

When it is desired to change the level of the video signal obtained by photographing relatively large, shutter speed control or gain control by the preamplifier circuit 13 is performed. Since the shutter speed is limited to 1/60 second and cannot be further reduced, the level is adjusted using the preamplifier circuit 13 when the video signal level is further increased. Since the level of the signal input to the preamplifier circuit 13 is low, it is difficult to finely adjust the level. Therefore, when fine adjustment of the video signal level is required, gain control is performed using the GCA 16 connected to the subsequent stage of the preamplifier circuit 13.

The image pickup device includes an electronic volume 21, and the output voltage thereof is controlled by the control device 20.
Electronic volume is a kind of D / A converter and control device
The digital data provided from 20 is output as a corresponding analog voltage signal. Shutter control data is supplied from the electronic volume 21 to the shutter control circuit 19, and gain control signals are supplied from the electronic volume 21 to the preamplifier circuit 13 and the GCA 16, respectively. Thus, the shutter speed of the CCD 11 by the shutter control circuit 19 and the gains of the preamplifier circuit 13 and the GCA 16 are determined. The electronic volumes are provided corresponding to the preamplifier circuit 13, the GCA 16 and the shutter control circuit 19, respectively.
In FIG. 1, the plurality of electronic volumes are represented by one electronic volume 21.

Photographing is performed under the control of the shutter control circuit 19, and a video signal representing the photographed subject image
It is read from D11. A video signal output from the CCD 11 is supplied to a preamplifier circuit 13 via a CDS (correlated double sampling circuit) 12. The gain according to the gain control signal given from the electronic volume 21
Is amplified and output.

The video signal output from the preamplifier circuit 13 is supplied to a color separation circuit 14 and a luminance signal generation circuit 15, respectively. The video signal is separated into color signals of three primary colors, G (green), R (red), and B (blue), representing a subject image by a color separation circuit 14 and supplied to the GCA 16. The luminance signal Y is generated by the luminance signal generation circuit 15 and supplied to the GCA 16.

The GCA 16 adjusts the color balance of the input color signal and amplifies the color signal and the luminance signal according to the gain control signal supplied from the electronic volume 21. Although one GCA 16 is shown in FIG. 1, actually, four GCAs are provided for three color signals R, G, B and a luminance signal Y, and a gain control signal is supplied from the electronic volume 21 to each of them.

In the GCA 16, amplification processing of each color signal is performed at an amplification rate corresponding to the ratio of the color balance adjustment so as not to lose the color balance. The color signal and the luminance signal that have been subjected to color balance adjustment and amplification by the GCA 16 are supplied to an encoder 18.

The encoder 18 generates and outputs an NTSC video signal.

The luminance signal output from the GCA 16 is also supplied to a peak detection circuit 17.

The peak detection circuit 17 outputs the input luminance signal at a predetermined cycle (for example, every 1 V; V is a vertical scanning period).
This is a circuit for detecting a peak level. Peak detection circuit 17
The peak value detected at is supplied to the control device 20.

As described later in detail, a peak value obtained by the peak detection circuit 17 is compared with a peak value preset in the control device 20. If the difference between the two peak values is within the allowable range, the shutter speed and the preamplifier circuit 13
And the gain of GCA is not changed. When the difference between the two peak values is out of the allowable range and smaller than a predetermined value (a value larger than the value indicating the allowable range), the gain of the GCA 16 is adjusted so that the difference between the two peak values becomes small. . If the difference between the two peak values is larger than the first predetermined value, the shutter speed, the gain of the preamplifier circuit 13, or both are adjusted. The predetermined value may be determined in consideration of the amplification capabilities of the preamplifier circuit 13 and the GCA 16, the balance between input and output signals in these circuits, and the like.

FIG. 2 shows such a shutter speed and gain adjustment process, that is, a level adjustment process (AE control) of a video signal obtained by photographing in the imaging apparatus shown in FIG.
6 is a flowchart showing the procedure of FIG. This process is mainly executed by the control device 20. The photographing of the subject (document) by the CCD 11 is repeatedly performed every 1 V or 2 V.

The peak detection is performed at every 1 V, for example, from the luminance signal obtained by the imaging, which is input to the peak detection circuit 17 (step 31). The peak value obtained by peak detection and the peak value of a video signal having an appropriate level (a video signal level obtained when an adjustment chart is photographed under a standard brightness) (this peak value is previously determined by a control device. 20 is set). On the basis of the comparison result, the shutter speed control (step 32) and the gain control of the preamplifier circuit 13 (step 35) are performed to set the R, G, B color signals and the luminance signal obtained by the imaging to appropriate levels. And GCA16 gain control (step
It is determined which of the controls in 38) is properly achieved.

The adjustment chart includes, for example, a white portion,
It is configured to include a black portion and a plurality of gray portions whose brightness gradually changes from white to black. Therefore, the peak value of the video signal having the appropriate level is
It is at or very close to the peak.

When the difference between the peak value obtained by the peak detection and the peak value of the appropriate level is relatively large, control of the shutter speed (step 32) or gain control of the preamplifier circuit 13 (step 35) is performed. . Both of these controls are performed as necessary. If the difference between the peak value obtained by the peak detection and the peak value at the appropriate level is large, first control the shutter speed (step 32).
Is performed. However, the shutter speed cannot be made slower than 1/60 second. Even if the shutter speed is set to 1/60 second, the difference between the peak value obtained by the peak detection and the peak value of the appropriate level may still be large.
In such a case, the gain control of the preamplifier circuit 13 is performed. When the difference between the peak value obtained by the peak detection and the peak value of the appropriate level is relatively small and the fine adjustment of the video signal obtained by the imaging is sufficient, the gain adjustment of the GCA 16 is performed (step 38). Regardless of the adjustable range of the video signal in each control, C
Shutter control capability of CD11 and shutter control circuit 19,
It is determined by the amplification capability of the preamplifier circuit 13 and the GCA16. The shutter speed and gain control are controlled by the control unit 20.
Is E corresponding to the shutter control signal or the gain control signal.
This is achieved by providing the VR data to the electronic volume 21 or by changing the EVR data.

When it is determined that control of the shutter speed is necessary (step 32), the shutter speed is changed (step 33). When the level of the video signal obtained by imaging is higher than the appropriate level, the shutter speed is controlled to increase, and when the level is opposite, the shutter speed is controlled to decrease. When the shutter speed is controlled,
Peak detection is performed again in the next 1 V period (step 3).
4) Return to step 32.

When it is determined that the gain control of the preamplifier circuit 13 is necessary (step 35), the gain of the preamplifier circuit 13 is controlled (step 36). This allows the preamplifier circuit
The gain of 13 changes, and the peak level of the video signal obtained by imaging approaches the proper peak level. When the gain control of the preamplifier circuit 13 is completed, peak detection is performed again in the next 1 V period (step 37), and the process returns to step 35.

When it is determined by the GCA 16 that fine adjustment of the video signal is necessary (step 38), the gain control signal applied to the GCA 16 is changed, and the gain control of the GCA 16 is performed (step 39). Peak detection is performed again in the next 1 V period (step 40), and the process returns to step 38.

As described above, necessary processing among the shutter speed control, the gain control of the preamplifier circuit 13 and the gain control of the GCA 16 is performed, and the video signal obtained by imaging has a proper peak level of the video signal. Converge to the peak level of

When the difference between the peak value of the video signal obtained by shooting and the peak value of the video signal having an appropriate level is small (if smaller than a certain value), it is determined that the level has converged to the appropriate level (step 41). YES), the adjustment process ends. The properly exposed image is displayed on a television screen. If the appropriate level is not attained by any of the controls (NO in step 41), an error is reported to the operator (step 42). The error notification may be performed by a display or a buzzer provided in the imaging device.

Second Embodiment FIG. 3 shows a second embodiment of the present invention and is a block diagram showing an electrical configuration of an image pickup apparatus.

In FIG. 3, the same circuit blocks as those shown in FIG.

In the imaging apparatus shown in FIG. 1, shutter control or gain control is performed based on the peak value obtained from the peak detection circuit 17 so that the level of the video signal output from the CCD 11 becomes appropriate. In the case of a subject having an extremely bright part in a part, the peak value of the video signal protrudes greatly compared to other parts. Therefore, if the level of the video signal is adjusted based only on the peak value, the entire image becomes dark. Could be.

The image pickup apparatus shown in FIG. 3 is an improvement of the apparatus of the first embodiment to solve such a problem.

The imaging device shown in FIG. 3 is different from the imaging device shown in FIG. 1 in that an average value detection circuit 23 is added.

The average value detecting circuit 23 receives the luminance signal generated by the luminance signal generating circuit 15 as an input, integrates the luminance signal in the photographing area of one image, and calculates the average value of the luminance signal.
This is a circuit that performs detection at a constant cycle (for example, every 1 V period). A signal representing the average value detected by average value detection circuit 23 is applied to control device 20A.

Also in the average value detection circuit 23, the luminance signal is amplified with the same gain as that of the GCA 16. Average value detection circuit 23 according to a gain control signal given from electronic volume 21
Are amplified, and an average value of the amplified luminance signals is detected. This makes the peak detection circuit 17
Signal and average value detection circuit whose peak value is detected by
The luminance signal at which the average value is detected by 23 is equal at that level.

In the imaging apparatus shown in FIG. 3, the control device is based on a peak value, an average value, or a value considering both the peak value and the average value in accordance with the difference between the peak value of the luminance signal and the average value of the luminance signal. The level adjustment processing (AE processing) of the video signal is performed under the control of 20A.

FIGS. 4 and 5 are flowcharts showing the processing procedure when AE control is performed using the imaging device shown in FIG. This process is mainly executed by the control device 20A. 4 and 5, the same processing blocks as those shown in FIG. 2 are denoted by the same reference numerals as those in FIG.

The peak value of the luminance signal is obtained in the peak detection circuit 17 (step 31).

It is determined whether or not the shutter speed needs to be controlled based on the peak value of the luminance signal (step 5).
0). When the peak value of the luminance signal is large and the signal portion of the peak value of the video signal is saturated, the shutter speed is controlled so as to increase the shutter speed (steps 50 and 33).

When the signal portion of the peak value of the video signal is not saturated, the shutter speed is not controlled, and the average value of the luminance signal for one image is detected by the average value detection circuit 23 (step 51).

Subsequently, it is determined whether or not the obtained peak value is larger than the average value and the difference between them is equal to or more than a predetermined value (step 52). For example, the peak value of a video signal obtained by shooting is much larger than the peak value of a video signal having an appropriate level (for example, 3 to 4 times or more), and the peak value of the video signal obtained by shooting is the video. When the average value of the signal is twice or more, it is determined that the difference between the peak value and the average value is equal to or more than a predetermined value. The video signal having an appropriate level is a video signal obtained when the adjustment chart is photographed under the reference brightness as described above.

When it is determined that the difference between the peak value and the average value is equal to or larger than a predetermined value (YES in step 52), the average value detection circuit 2
The average value obtained in 3 is compared with the average value of the video signal having the appropriate level (this average value is also preset in the control device 20A). Based on this comparison result,
In order to set the R, G, B color signals and the luminance signal obtained by imaging to appropriate levels, the gain control of the preamplifier circuit 13 (step 65) and the gain control of the GCA 16 (step 65)
It is determined which of 68) is appropriate to use.

When the difference between the two average values is relatively large, gain control of the preamplifier circuit 13 (step 65) is performed.
Thereafter, the average value detection processing is performed again (step 5).
6) Return to step 65.

When the difference between the average values is relatively small and the GCA 16 determines that fine adjustment of the video signal level is necessary (step 68), the gain control of the GCA 16 is performed (step 68).
39). Thereafter, the average value detection process is performed again (step 57), and the process returns to step 68.

As described above, the AE control process is performed based on the difference between the average values, and it is determined whether or not the video signal finally obtained by imaging has reached an appropriate level (step 41). That is, when the difference between the average value of the video signal obtained by shooting and the average value of the video signal having an appropriate level falls within the allowable range, it is determined that the video signal obtained by shooting is at the appropriate level. If it is at the proper level, the process is terminated. If it is not at the proper level, error processing is performed as in the process shown in FIG. 2 (step 42).

When the peak value is larger than the average value and the difference between them is equal to or larger than a predetermined value, A is determined based on the average value.
Since the E control is performed, even if a part of the subject has an extremely bright spot and the peak value of the video signal is significantly prominent compared to other parts, the whole except for the part showing the peak is obtained. Thus, an image with appropriate brightness can be obtained.

When the difference between the peak value and the average value is smaller than a predetermined value (NO in step 52), AE control is performed in consideration of both the peak value and the average value. More specifically, the peak value and the average value are set at a predetermined ratio (for example, 4:
AE control is performed based on the value obtained by weighted averaging at the ratio of 6) (step 81).

First, the weighted average value of the video signal obtained by photographing the subject is compared with the weighted average value of the video signal of an appropriate level (this weighted average value is also preset in the control device 20A). From this comparison result, in order to make the video signal obtained by photographing the subject closer to a video signal of an appropriate level, shutter speed control (step 72), gain control of the preamplifier circuit 13 (step 75), and GCA
It is determined which of the sixteen gain controls (step 78) is preferred. If the difference between the two weighted average values is large, the shutter speed control (step 7) is performed in the same manner as in the above-described embodiment.
2) Or gain control of preamplifier circuit 13 (step 75)
Is performed (both controls as necessary), and if the difference between the two weighted average values is small and out of the allowable range, the gain control of the GCA 16 is performed (step 78).

If the difference between the two weighted average values is larger than a predetermined value and the shutter speed can be controlled (when the shutter speed needs to be reduced, the shutter speed does not reach 1/60 second) First, a shutter speed control process is performed (step 33). Subsequently, peak detection (step 34) and average value detection (step 55) are performed to calculate a weighted average value.

A weighted average value (for example, at a ratio of 4: 6) of the peak value and the average value obtained in the peak detection (step 34) and the average value detection (step 55) is calculated (step 82).

Based on the calculated weighted average value, it is determined again whether or not the shutter speed needs to be controlled (step 72).

If the difference between the weighted average values is large and the shutter speed becomes 1/60 second and cannot be further reduced (when the shutter speed needs to be further reduced), the preamplifier circuit 13 Is performed (steps 75 and 36). After that, peak detection (step
37) and average value detection (step 56) are performed, and a peak value and an average value are detected. A weighted average value of the detected peak value and the average value is calculated (step 83), and the process returns to step 75.

If the difference between the calculated weighted average value and the weighted average value obtained based on the video signal of an appropriate level is still large, the gain control of the preamplifier circuit 13 is necessary again.

If the difference between these weighted average values is small and still not within the allowable range, the gain control of GCA 16 is performed (steps 78 and 39). Thereafter, peak detection (step 40) and average value detection (step 57) are performed. A weighted average value of the obtained peak value and average value is calculated again (step 84), and the process returns to step 78.

If the difference between the weighted average value of the video signal and the weighted average value of the video signal of the appropriate level is within the allowable range, the AE control ends (step 41).

In the above, when the difference between the peak value and the average value is equal to or larger than the predetermined value (YES in step 52), the gain control of the preamplifier circuit 13 or the GCA 16 is performed based on the average value (step 36). , 39), control of the shutter speed may be added to this.

When the difference between the peak value and the average value is smaller than the predetermined level (NO in step 52), it is considered that an extremely bright portion is not included in a part of the subject, and therefore, FIGS. As in the first embodiment shown in FIG. 2, AE control based on the peak value may be performed.

Third Embodiment FIGS. 6 and 7 show a third embodiment. The configuration of the imaging device shown in FIG. 3 can be applied as it is.

The AE control process shown in FIG. 4 and FIG.
In the embodiment, peak detection and average value detection are performed. When the difference between the obtained peak value and the average value is equal to or smaller than a predetermined value, the peak value and the average value are weighted and averaged at a ratio of 4: 6, and the shutter speed control and the gain are performed based on the obtained weighted average value. The control is performed (step 81 in FIG. 5 and subsequent processes).

On the other hand, in the AE control processing of the third embodiment, the ratio of the weight given to the average value and the peak value for calculating the weighted average value in accordance with the magnitude of the difference between the peak value and the average value is determined. A corresponding value (this is referred to as a weighting ratio γ) is determined, and a weighted average calculation of the peak value and the average value is performed at the determined weighting ratio γ. Shutter speed control and gain control are performed based on the obtained weighted average value.

The weighting ratio γ can be variously defined. Here, the weighting ratio γ is defined as a value that varies in the range of 0 to 10 as shown in the graph of FIG. 9 according to the value of the difference α between the peak value and the average value. . The weighted average value is calculated by the following equation using the weighting ratio γ and the difference α between the peak value and the average value.

Weighted average value = average value + γ × α / 10 {Formula 1}

In FIG. 9, the weight ratio γ takes a large value when the image obtained by photographing the subject does not have a distinctly bright portion and has substantially the same overall brightness. That is, the smaller the difference α between the peak value and the average value, the smaller the weight ratio γ
Is a large value. On the other hand, the weight ratio γ becomes a small value when the difference α between the peak value and the average value is large because a part of the subject image has a very bright portion. When the weighting ratio γ is large, the influence of the peak value on the weighted average value increases. The maximum value of the weighting ratio γ is set to 10, and when the weighting ratio γ = 10, the weighted average value is the average value of the average value and the peak value. When the weighting ratio γ is small, that is, when there is a very bright portion in a part of the subject image, the weighted average value approaches the average value. When the difference α between the peak value and the average value reaches a certain value β, the weighting ratio γ becomes zero. This value β
Means that if the subject image has a very bright part and the peak value slightly affects the weighted average,
It represents the difference between the peak value and the average value in a situation where control is considered impossible. Specifically, the difference between the peak value and the average value obtained when the adjustment chart is imaged is adopted as β. The adjustment chart is as described above, and will be described later in more detail.

Referring to FIG. 8, the weight ratio calculation processing and the weighted average value calculation processing will be described.

First, the difference α between the peak value and the average value given to the control device 20A is calculated (step 91).

Subsequently, the calculated difference α is equal to the value β
(This value β is stored in advance in the control device 20A) is determined (step 9).
2).

When the calculated difference α is larger than the value β, it is determined that a part of the subject image has an extremely bright portion, and the peak value of the video signal obtained by photographing is prominent. In such a case, it is better to control the brightness of the image based on the average value ignoring the peak value, so that the weighting ratio γ is set to 0 (step 93). The weighted average is equal to the average from Equation 1 (step 97).

When the calculated difference α is equal to or smaller than the value β (NO in step 92), the calculated difference α is β / 10 (10 divided by the value β).
Is determined in consideration of the accuracy of the analog / digital conversion circuit included in the control device 44, and may be divided by other numerical values.

When the difference α is equal to or smaller than β / 10 (in step 94,
YES), the difference α between the detected peak value and the average value is small. Therefore, the weighting ratio γ is set to 10 (step 95), and the weighted average value is equal to the average of the peak value and the average value from Expression 1 (step 97).

When the difference α is larger than β / 10 (NO in step 94), the weighting ratio γ is calculated by using the equation (step 95), and the weighted average value is calculated by using the weighting ratio γ in equation (1). (Step 97).

Weighting ratio (γ) = β / α Equation 2

AE control processing based on the processing procedures shown in FIGS. 6 and 7 will be described.

The processing in FIGS. 6 and 7 is almost the same as the processing shown in FIG. 5, except for the processing for calculating the weighted average value. Therefore, in FIGS. 6 and 7, the same processing blocks as those shown in FIG. 5 are denoted by the same reference numerals as those shown in FIG.

Although the processing for controlling the shutter speed so that the signal portion of the peak value of the video signal is not saturated is not shown in FIGS.
Needless to say, processing for controlling the shutter speed may be performed so that the signal portion of the peak value of the video signal is not saturated as in the case of 31, 50, and 33.

First, the peak value (step 85) of the luminance signal detected by the peak detection circuit 17 and the average value (step 86) detected by the average value detection circuit 23 are supplied to the control device 20A. The weighting ratio γ is calculated from the peak value and the average value given to the control device 20A, and the weighted average value is calculated by Expression 1 using the calculated weighting ratio γ (step 98). This is performed according to the processing shown in FIG. 8 as described above.

The calculated weighted average value is compared with a value obtained by weighting the peak value and the average value of the video signal having the appropriate level at a ratio of 4: 6.

The video signal of the appropriate level is a video signal obtained when the adjustment chart is photographed under the reference brightness as described above. As described above, the adjustment chart includes a white portion, a black portion, and a gray portion having a plurality of brightness levels. Since the peak value is at or near the level of the white peak and the average value is at a level approximately intermediate between the white peak and the black peak, the peak value and the average value are weighted and averaged at a ratio of 4: 6. The value will be located at a level between the white peak and the intermediate level.

When the difference between the calculated weighted average value and the weighted average value obtained from the video signal of an appropriate level is large,
First, the shutter speed is controlled in a direction to reduce the difference (steps 72 and 33). The peak detection and the average value detection are performed again (steps 34 and 55), the calculation of the weighting ratio γ and the weighted average value are performed (step 98), and the process returns to step 72.

Even after the control of the shutter speed is performed, if the difference between the weighted average value of the video signal obtained by shooting and the weighted average value of the video signal of the appropriate level is still large, the shutter speed control is performed again. Done. When the shutter speed needs to be controlled in the direction of decreasing the shutter speed, and when the shutter speed is already set to 1/60 second, the shutter speed cannot be further reduced. At this time, gain control of the preamplifier circuit 13 is performed (step 75,
36). Thereafter, peak detection and average value detection are performed again (steps 37 and 56), a weight ratio γ and a weighted average value are calculated (step 98), and the process returns to step 75.

If the difference between the calculated weighted average value and the weighted average value obtained based on the video signal of an appropriate level is still large, the gain control of the preamplifier circuit 13 is required again. If the difference between these weighted average values is small, but not within the proper range, gain control of the GCA 16 is performed (steps 78 and 39).

When the gain control of GCA 16 is performed, peak detection (step 40) and average value detection (step 57) are performed again to calculate the weighting ratio. A weight ratio and a weighted average value are calculated from the obtained peak value and average value (step 98).

Steps 78, 39, 40, 57 and 98 are repeated until the difference between the weighted average value of the video signal and the weighted average value of the video signal of the appropriate level falls within the allowable range.
When the difference between the weighted average value of the video signal and the weighted average value of the video signal of the appropriate level falls within the allowable range, the AE control process ends.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an electrical configuration of an imaging apparatus according to a first embodiment.

FIG. 2 is a flowchart illustrating a procedure for adjusting a level of a video signal.

FIG. 3 is a block diagram illustrating a second embodiment and illustrating an electrical configuration of an imaging apparatus.

FIG. 4 is a flowchart illustrating a procedure of a video signal level adjustment process.

FIG. 5 is a flowchart showing a procedure for adjusting a level of a video signal.

FIG. 6 is a flowchart illustrating a video signal level adjustment processing procedure according to a third embodiment.

FIG. 7 is a flowchart illustrating a level adjustment processing procedure of a video signal.

FIG. 8 is a flowchart illustrating a procedure of a weight ratio and a weighted average value calculation process.

FIG. 9 is a graph showing a relationship between a level difference between a peak value and an average value and a weighting ratio.

[Explanation of symbols]

 11 CCD 13 Preamplifier (first amplifier) 16 GCA (second amplifier) 17 Peak detector 19 Shutter control circuit 20 Controller 21 Electronic volume (EVR) 22 Lighting 23 Average value detection circuit

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) // H04N 101: 00 H04N 101: 00 (72) Inventor Toshio Nakajima 3-46 Izumizu, Asaka-shi, Saitama Fuji-sha Shin Film Co., Ltd. (72) Inventor Yutaka Maeda 3-11-46 Izumi, Asaka-shi, Saitama Fuji-sha Shin Film Co., Ltd. F-term (reference) 2H002 CC02 CC09 CD05 FB23 HA21 JA07 JA08 2H053 AA08 BA85 CA41 2H054 AA01 5C022 AA13 AB04 AB05 AB20 AC52 AC69 CA00 5C024 BX01 CX54 HX18 HX20 HX21 HX29

Claims (22)

[Claims] 1. A shutter means having a variable shutter speed, an imaging means for photographing a subject under exposure by said shutter means, and outputting a video signal representing a subject image, and amplifying a video signal output from said imaging means. Amplifying means, a peak detection circuit for detecting a peak of a video signal output from the imaging means, an average level detection circuit for detecting an average level of a video signal output from the imaging means, and a peak detection circuit obtained by the peak detection circuit. Level and appropriate peak
First level difference detecting means for detecting a first peak level difference from the level, shutter controlling means for controlling the shutter means so as to reduce the first peak level difference, and peak detecting circuit. Second level difference detecting means for detecting a second level difference between the measured peak level and the average level obtained by the average level detecting means;
And the second level difference detected by the second level difference detection means exceeds a reference value for discriminating whether to set the basis of the level adjustment of the video signal at the average level or at the peak level. The shutter control of the shutter means or the gain control of the amplifying means is performed so that the average level approaches the proper average level, and the second level difference detected by the second level difference detecting means is determined by the second level difference detecting means. An image pickup apparatus comprising: control means for performing shutter control of the shutter means or gain control of the amplifying means so that at least the peak level approaches the proper peak level when the reference level is not more than the reference value. 2. The first amplifying circuit for amplifying a video signal output from the photographing means, the first amplifying circuit comprising:
And a second amplifying circuit for finely adjusting the level of the video signal output from the amplifying circuit. The control means controls the difference between the average level and the appropriate average level or the peak level and the appropriate peak level. 2. The imaging apparatus according to claim 1, wherein the gain control of the first amplifier circuit is performed when the difference between the first and second amplifier circuits is large, and the gain control of the second amplifier circuit is performed when the level difference is small. 3. A shutter means having a variable shutter speed, an imaging means for photographing a subject under exposure by said shutter means, and outputting a video signal representing a subject image, and amplifying a video signal output from said imaging means. Amplifying means, a peak detection circuit for detecting a peak of a video signal output from the imaging means, an average level detection circuit for detecting an average level of a video signal output from the imaging means, and a peak detection circuit obtained by the peak detection circuit. Level difference detecting means for detecting a level difference between a level and an average level obtained by the average level detecting circuit, and the level difference detected by the level difference detecting means places the basis of the level adjustment of the video signal on the average level. If the average level exceeds the reference value for discriminating whether to set the peak level or the peak level, the average level is adjusted to the appropriate average level. An image pickup apparatus comprising: control means for performing shutter control of the shutter means or gain control of the amplification means so as to approach the bell. 4. The first amplifying circuit, wherein the amplifying means amplifies a video signal output from the imaging means,
And a second amplifying circuit for finely adjusting the level of the video signal output from the amplifying circuit. When the difference between the average level and the appropriate average level is large, the control means controls the first amplifying circuit. 4. The imaging apparatus according to claim 3, wherein the gain control is performed such that the gain control of the second amplifying means is performed when the level difference is small. 5. A weighted average level calculating means for weighting and averaging a peak level obtained by said peak detection circuit and an average level obtained by said average level detection circuit at a predetermined ratio, wherein said control means comprises: When the level difference detected by the difference detecting means is equal to or less than the reference value, the shutter control of the shutter means or the control of the amplifying means is performed so that the weighted average level obtained by the weighted average level calculating means approaches the appropriate weighted average level. The imaging device according to claim 3, wherein the imaging device performs gain control. 6. The control means according to claim 1, wherein when the level difference detected by said level difference detecting means is equal to or less than said reference value, a peak level obtained by said peak detection circuit becomes said proper peak level. 4. The image pickup apparatus according to claim 3, wherein shutter control of said shutter means or gain control of said amplifying means is performed. 7. A weighted average level calculating means for weighting and averaging a peak level obtained by the peak detection circuit and an average level obtained by the average level detection circuit at a predetermined ratio, wherein the control means comprises: When the level difference detected by the difference detecting means is equal to or less than the reference value, one of the weighted average level obtained by the weighted average level calculating means and the peak level obtained by the peak detecting circuit is selected. Controlling the shutter of the shutter means or the gain of the amplifying means so as to approach the corresponding one of the proper weighted average level and the proper peak level.
The imaging device according to claim 3. 8. A peak level difference detecting means for detecting a peak level difference between a peak level obtained by the peak detection circuit and an appropriate peak level, and the shutter means for reducing the peak level difference. The imaging apparatus according to any one of claims 3 to 7, further comprising a shutter control unit configured to control (i). 9. A shutter means having a variable shutter speed, an imaging means for photographing a subject under exposure by said shutter means, and outputting a video signal representing a subject image, and amplifying a video signal outputted from said imaging means. Amplifying means, a peak detection circuit for detecting a peak of a video signal output from the imaging means, an average level detection circuit for detecting an average level of the video signal output from the imaging means, and a peak detected by the peak detection circuit The weighting ratio is set so that the ratio of the average level increases as the level difference between the level and the average level detected by the average level detection circuit increases, and the ratio of the average level decreases as the level difference decreases. The above-mentioned peak level and the above-mentioned average are determined using the weight ratio determining means to be determined, and the weight ratio determined by the weight ratio determining means. Weighted average level calculation means for calculating a weighted average level with the average level, and shutter control of the shutter means or the amplification means such that the weighted average level calculated by the weighted average level calculation means approaches an appropriate weighted average level. An imaging apparatus comprising: control means for performing gain control of the image pickup device. 10. A first amplifying circuit for amplifying a video signal output from the photographing means, and a second amplifying device for finely adjusting a level of the video signal output from the first amplifying circuit. And an amplifying circuit.
When the difference between the weighted average level and the appropriate weighted average level is large, the gain control of the first amplifier circuit is performed,
10. The control device according to claim 9, wherein when the level difference is small, the gain of the second amplifier circuit is controlled.
An imaging device according to claim 1. 11. The imaging apparatus according to claim 1, further comprising an illuminating means for illuminating a subject, wherein said photographing means photographs a subject image illuminated by said illuminating means. 12. Shutter means having a variable shutter speed,
An image pickup device comprising: an image pickup device for photographing a subject under exposure by the shutter means and outputting a video signal representing a subject image; and an amplifying circuit for amplifying a video signal output from the image pickup device. Detecting the peak level and the average level of the video signal output from the first, the first peak level difference between the detected peak level and the appropriate peak level, and the detected peak level and the detected average level And the second level difference is detected, and the shutter speed of the shutter means is controlled so as to reduce the first peak level difference. The second level difference is the basis for adjusting the level of the video signal. If the average level exceeds the reference value for discriminating whether to place it at the average level or at the peak level, the average level approaches the appropriate average level. As described above, the shutter speed control of the shutter means or the gain control of the amplifier circuit is performed. When the shutter speed is equal to or less than the reference value, the shutter speed control or the gain control is performed so that at least the peak level approaches an appropriate peak level. , Imaging device control method. 13. A first amplifier circuit for amplifying a video signal output from the photographing means, and a second amplifier for finely adjusting the level of the video signal output from the first amplifier circuit. When the difference between the average level and the proper average level or the difference between the peak level and the proper peak level is large, the gain control of the first amplifier circuit is performed, and the level difference is small. And controlling gain of the second amplifier circuit.
13. The control method of the imaging device according to 12. 14. Shutter means having a variable shutter speed,
An image pickup device comprising: an image pickup device for photographing a subject under exposure by the shutter means and outputting a video signal representing a subject image; and an amplifying circuit for amplifying a video signal output from the image pickup device. Detecting the peak level and the average level of the video signal output from the CPU, detecting the level difference between the detected peak level and the average level. When a reference value for discriminating whether to place the signal at the level or the peak level is exceeded, the shutter speed control of the shutter means or the gain control of the amplifier circuit is performed so that the average level approaches an appropriate average level. And a control method of the imaging device. 15. A first amplifier circuit for amplifying a video signal output from the photographing means, and a second amplifier for finely adjusting the level of the video signal output from the first amplifier circuit. A gain circuit for controlling the gain of the first amplifier circuit when the difference between the average level and the appropriate average level is large, and a gain control for the second amplifier circuit when the difference between the average level and the appropriate average level is small. Claim
15. The control method of the imaging device according to 14. 16. A weighted average level of a detected peak level and an average level is weighted and averaged at a predetermined ratio, and when the level difference is equal to or less than the reference value, the weighted average level approaches an appropriate weighted average level. 15. The method according to claim 14, further comprising controlling a shutter speed of the shutter means or a gain control of the amplifier circuit. 17. When the level difference is equal to or less than the reference value, shutter speed control of the shutter means or gain control of the amplifier circuit is performed so that the detected peak level becomes the appropriate peak level. Item 15. The control method for an imaging device according to item 14. 18. A weighted average of a detected peak level and an average level at a predetermined ratio, and when the level difference is equal to or smaller than the reference value, a selected one of the weighted average level and the detected peak level is selected. 15. The image pickup apparatus according to claim 14, wherein the shutter control of the shutter means or the gain control of the amplifier circuit is performed such that one of them approaches a corresponding one of the proper weighted average level and the proper peak level. Control method. 19. The method according to claim 14, further comprising detecting a peak level difference between the detected peak level and an appropriate peak level, and controlling a shutter speed of the shutter means so as to reduce the detected peak level difference. 19. The control method for an imaging device according to any one of items 18 to 18. 20. Shutter means having a variable shutter speed,
An image pickup device for photographing a subject under exposure by the shutter means and outputting a video signal representing a subject image; and an amplifying circuit for amplifying a video signal output from the image pickup device. The peak level and the average level of the video signal output from are detected, and the ratio of the average level increases as the level difference from the detected peak level and the average level increases, and as the level difference decreases, A weighting ratio is determined so that the ratio of the average level is reduced, and a weighted average level of the peak level and the average level is calculated based on the determined weighting ratio, and the calculated weighted average level is an appropriate weighted average level. Controlling the shutter speed of the shutter means or the gain control of the amplifier circuit so as to approach Method. 21. A first amplifier circuit for amplifying a video signal output from the photographing means, and a second amplifier for finely adjusting the level of the video signal output from the first amplifier circuit. When the difference between the weighted average level and the appropriate weighted average level is large, the gain control of the first amplifier circuit is performed. When the level difference is small, the gain control of the second amplifier circuit is performed. 21. The method for controlling an imaging device according to claim 20, wherein the method is performed. 22. A video signal representing a subject image by illuminating the subject and photographing the subject under the illumination.
21. The method for controlling an imaging device according to 20.