JP3376034B2 - Imaging device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to exposure control of an image pickup apparatus having electronic image magnification magnifying means for electronically magnifying an image magnification of a subject.

[0002]

2. Description of the Related Art In recent years, video equipment such as a video camera has been remarkably developed, and various functions such as an automatic exposure control function, an automatic focus control function, and a high-magnification zoom function are standardly provided.

Further, recently, a function called so-called electronic zoom has been introduced in which a signal is intermittently read out from an image pickup element and interpolated / interpolated to electronically increase an image magnification of a subject, and a high-magnification zoom is further achieved. It has become possible and the functionality and operability have been improved.

[0004]

However, the exposure control method generally used for video cameras and the like is as follows.
The aperture is controlled so that the brightness level of the video signal output from the image sensor is constant at a predetermined level.
Considering the case where such an automatic exposure control function and electronic zoom function are installed, with the conventional optical zoom, the angle of view set by zooming and the readout range on the imaging surface of the image sensor are always the same. However, when the electronic zoom function as described above is operated, the angle of view of the optical image actually incident on the image pickup surface and the read range of the image pickup element are different. If the image signal output from the device is used as it is, when the image is magnified by operating the electronic zoom, the magnified angle of view differs from the angle of view on the image sensor used for exposure control (displayed on the screen. The image signal of the part that is not displayed is also used for exposure control.) Not only may the exposure control for the enlarged angle of view not be optimal, but the exposure may fluctuate depending on the electronic zoom operation. Ri instability there is a danger to or summer, is a problem in carrying out the shooting.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image pickup apparatus capable of optimal exposure control under any subject condition even when the electronic image magnification enlarging means is operated.

[0006]

The present invention has been made to achieve the above-mentioned object, and is characterized in that an image pickup signal output from the image pickup means is intermittently changed according to the electronic zoom magnification. Enlarging means for electronically enlarging a subject image imaged by the image pickup means by read-out control, and integrating means for integrating the image pickup signal read out intermittently in accordance with the electronic zoom magnification of the enlarging means for a predetermined period. And an exposure control means for performing exposure control based on the integrated output of the integrating means, and an image pickup signal output from the image pickup means being intermittently read out in accordance with the electronic zoom magnification of the enlarging means. An image pickup apparatus comprising: a correction unit that corrects an attenuation amount of the integrated output of the integration unit.

[0007]

As a result, the exposure control according to the image magnification actually displayed on the screen can be always performed, and even when the electronic zoom operation is performed to intermittently read out the image or perform the interpolation process, etc. A proper exposure can always be obtained without causing an error due to the non-signal portion.

[0008]

Embodiments of the image pickup apparatus according to the present invention will be described in detail below with reference to the drawings.

First, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an example of an exposure control system of an image pickup apparatus equipped with an electronic zoom and automatic exposure control means which are electronic image magnification enlarging means of the first embodiment of the present invention. For convenience of explanation, it is assumed that the electronic zoom magnification is 2 times.

FIG. 1 is a block diagram showing a first embodiment of the present invention, showing a video camera provided with an electronic zoom and automatic exposure control means which are electronic image magnification enlarging means. In the figure, 1 is a focus lens, 2 is a diaphragm mechanism (hereinafter referred to as an iris) for adjusting the amount of incident light to the image sensor, 3 is an iris drive motor for driving the iris, 4
Is an image pickup device such as CCD, 5 is a scanning timing pulse generator for driving the image pickup device 4, 6 is a correlated double sampling circuit, and 7 is an automatic gain control for controlling the output signal level of the image pickup device together with the iris. A circuit (hereinafter abbreviated as AGC circuit), 8 is an A / D converter for converting an analog image signal into a digital image image signal, 9
Is a signal processing circuit for performing predetermined signal processing such as gamma correction, knee correction and white clip processing on the digital image signal output from the A / D converter 8, 10 is an image memory circuit,
Reference numeral 11 is a D / A converter that converts a digital image signal read from the image memory 10 into an analog image signal.

Reference numeral 12 is an integrating circuit for integrating and smoothing the image signal output from the AGC circuit 7 for a predetermined period. Reference numeral 13 is for comparing the integrated output of the integrating circuit 12 with a predetermined reference voltage and responding to the comparison result. It is a comparison circuit that generates an output.

The image signal smoothed by the integration circuit 13 is compared with a reference voltage by a comparison circuit 14, and an error signal corresponding to the error is supplied to a system control circuit 16 described later to calculate an exposure correction amount. To be done. Thereby, one or more optimum control parameters are selected from the exposure control parameters of the iris 2, the electronic shutter for adjusting the photoelectric conversion time of the image pickup device 4, the AGC circuit 7, etc. according to the subject situation, and the calculation is performed. After converting the exposure correction amount into each exposure control data, the exposure control data is output to the iris drive circuit 17 and the scanning timing pulse generation circuit 5 for driving the iris drive motor 3, respectively, to perform the exposure control, and the output of the integration circuit 13 So that the reference voltages are equal, that is, finally D
The level of the output video signal of the / A converter 11 is controlled to be constant.

The video signal output from the AGC circuit 7 which has not been subjected to interpolation or the like by enlarging the electronic image magnification is
In order to obtain the detailed luminance information of the screen, the gate circuit 14 is gated by the gate signal for dividing the image area as shown in FIG. 4 (in the case of FIG. 4, the screen is divided into 64 equal parts), and the integration circuit 15 is used. After smoothing, it is detected by the system control circuit 16. By detecting the signal of the high brightness part of the screen based on the detection signal and performing weighting on the detection data of each part of the gate signal such as peak photometric control to operate so that the high brightness signal has an optimum exposure. Various so-called photometric patterns are possible, and a combination of the photometric patterns and the exposure control parameters such as the iris, AGC, and electronic shutter is programmed, and so-called program AE is possible to perform effective exposure control by switching according to shooting conditions. I am trying.

Reference numeral 16 is a system control circuit composed of a microcomputer for controlling the entire system. In the exposure control system, the comparison circuit 13 and the integration circuit 1 are used.
An exposure control data arithmetic circuit 16a, which controls the iris, the electronic shutter (accumulation time control of the image sensor), and the AGC circuit to perform exposure control data for exposure control based on the output of FIG. The iris control circuit 16c that controls the iris drive circuit 17 according to the output of 16a and the scanning timing pulse generator 5 according to the output of the exposure control data calculation circuit 16a to control the storage time of the image sensor, that is, the shutter speed. The gain of the AGC circuit is controlled according to the outputs of the shutter control circuit 16d and the exposure control data calculation circuit 16a (the iris
AGC control circuit 16e is provided for performing gain-up when proper exposure cannot be obtained even when is opened.

Further, the electronic zoom magnification control circuit 16b for varying the screen reading range by controlling the scanning timing pulse generator 5 in response to the scanning of a zoom key (not shown) from the outside to intermittently read from the image pickup device.
Is equipped with.

Further, there is provided a gate pulse generation circuit 16f for controlling the gate circuit 14 to perform a screen division as shown in FIG. 4 to generate a gate pulse for detecting a signal or the like in a high brightness portion.

The image magnification information set by the electronic zoom magnification control circuit 16b is supplied to the gate pulse generation circuit 16f, and based on this, the gate pulse generation circuit 16f.
Corrects the photometric area according to the image magnification, that is, the read range of the screen of the image sensor.

Further, the outputs of the comparison circuit 13 and the integration circuit 15 are controlled by the electronic zoom magnification control circuit 16b according to the image magnification, respectively, and an exposure control error caused by a mixture of a portion with image information and a portion without image information. It is provided with intermittent data correction circuits 16g and 16h for correcting.

The operation of the electronic zoom will be described with reference to FIG. The same figure is a timing chart showing the scanning timing of the image sensor. The figure (A) is a vertical transfer pulse, the figure (B) is a horizontal transfer pulse, the figure (C) is a horizontal scan pulse, and the figure (D) is an image pickup. The output signal of the element is shown. The vertical transfer pulse (A) and horizontal transfer pulse (B) are generated by the scanning timing pulse generator 5.

FIG. 3 is a conceptual diagram showing an image of a subject, that is, the image sensing element light receiving surface 51 and the image sensing element output image 5.
2 shows a state of the image 53 displayed on the monitor screen. The area of the image sensor light receiving surface 51 to be enlarged is surrounded by a frame, and the other unnecessary areas are indicated by diagonal lines.

Considering the double electronic zoom, the vertical CCD (not shown) in the image pickup device is driven only within the vertical blanking period in order to set only the region of the image pickup device light receiving surface 51 to be enlarged as the scanning region. 2A is performed at high speed to sweep out unnecessary charges in the shaded area in the vertical direction of the light receiving surface 51 of the image pickup device 51, and in FIG.
The vertical transfer pulse shown in FIG. 2A is generated once for every two horizontal scanning pulses shown in FIG. 2C, and the image sensor output signal shown in FIG. At that time, in order to intermittently read out the signal in the horizontal scanning direction in the vertical direction in accordance with the magnification to be enlarged, as in the image sensor output image 52, according to the control signal from the scan timing pulse generator 5, the image sensor 4 scans the scanning line 2 The image sensor output signals in FIG. 2D are thinned out and read out at a rate of one for each book.

A noise component is removed from the read image sensor output signal (D) by the correlated double sampling circuit 6, and AG
After the amplitude is controlled by the C circuit 7, it is sent to the A / D converter 8 and converted into a digital signal. And A / D converter 8
The output digital signal is supplied to the signal processing circuit 9 and subjected to color signal processing and the like, and then supplied to the memory circuit 10 and stored therein. Vertical interpolation is performed by calculating an average value and interpolating the average value between the two scanning lines. Further, by prohibiting reading or writing of digital data of an image pickup signal corresponding to an unnecessary area 52a in the left-right direction of the image pickup device output image 52, the image pickup operation is discarded inside the memory circuit 10 and corresponds to an effective area to be enlarged. Horizontal interpolation is performed by interpolating the average value of the two digital data between the adjacent digital data of each pixel of the signal. Then, the interpolated digital signal is input to the D / A converter 11 and converted back into an analog image pickup signal, and an image of the monitor image 53 is obtained.

Next, the exposure control when performing the electronic zoom as described above, which is a feature of the present invention, will be described.

As is apparent from the above description, the exposure control of the present invention controls the iris, the AGC, the storage time of the image sensor, etc. so that the video signal level becomes constant. When electronically changing the angle of view, the range of the screen for which the exposure control is performed is adjusted to the angle of view that is electronically changed, and the exposure control is performed using the signal after the enlarging process and the interpolation process. Then, the following problems occur.

That is, if the final angle of view by electronic zoom and the area for photometry differ, the image after electronic zoom may not be optimally exposed. Therefore, the angle of view after electronic zoom and the angle of view for photometry are different. In order to adjust the values, the video signal after electronic zooming, that is, the output of the D / A converter 11 is directly supplied to the integrating circuit 12 and the gate circuit 14, and the interpolation / enlargement processing performed in the electronic zooming operation is performed as described above. The video signal after that is due to the fact that the dynamic range of the A / D converter, D / A converter, signal processing circuit, etc. is not sufficient, and the gamma correction, knee correction, and white clip circuit in the signal processing circuit have an effect. Signals near high brightness are compressed and clipped, and information cannot be obtained faithfully, so it is suitable for shooting high brightness subjects or subjects with a large contrast ratio. There is a problem that can not be controlled to level out.

Therefore, according to the present invention, the output signal of the image pickup device before the signal processing such as gamma correction is used for the exposure control, and when the electronic image magnification enlarging operation is performed, no signal is intermittently read out and not interpolated. Even when a line is generated, the effect of a no-signal line on exposure control is corrected, and by using a signal that has a dynamic range before performing signal processing such as gamma correction as the image detection signal for exposure control. Also, appropriate exposure control can be performed on a high-brightness subject, and optimal exposure control can be performed as in the normal shooting operation.

That is, specifically, in FIG.
The output signal of the C circuit 7 is used. This AGC output signal is
While being supplied to the comparison circuit 13 via the integration circuit 12,
The output signals of the gate circuit 14 and the integration circuit 15 are connected to the system control circuit 16. The system control circuit 16 performs normal exposure control processing when the electronic image magnification enlarging operation is not performed, but the output signal of the AGC circuit 7 is a signal before signal processing such as gamma correction and knee correction is performed. Since the dynamic range is sufficiently secured, the brightness information is accurate even for a high-brightness subject. Even if the exposure control by the system control circuit 16 is the same as the conventional one, a high-brightness subject or a subject with a large contrast ratio is used. Proper exposure control can be performed.

By the way, as described above, a proper exposure control can be performed by using a signal which is thinned out in the horizontal direction and which is not interpolated as the image signal for the exposure control, but it is accurate only by this. Exposure control is not possible.

Therefore, the system control circuit 16 performs the following processing operation when enlarging the electronic image magnification.

The output signal of the AGC circuit 7 during the electronic image magnification enlarging operation has a non-signal line in a state where it is thinned out in the horizontal direction and is not interpolated. For example, when the magnifying operation of 2 times is performed as described above, half of the lines are in a non-signal state because they are thinned out and read from the image sensor 4 at a ratio of one scanning line to two scanning lines. In this case, the output signal of the comparison circuit 21 is 1/2 times as large as that when a subject having the same brightness is photographed without the electronic image magnification enlarging operation.

Similarly, when the image magnification of the electronic image magnification enlarging operation is n times, the attenuation rate becomes 1 / n times and changes according to the image magnification. Based on the image magnification information from the zoom controller 16b, the attenuation of the detection signal due to the non-signal line is corrected according to the image magnification. The D / A converter 11 which is output as a standard video signal in the exposure correction data calculation unit 16a from the data corrected by the intermittent data correction unit 16g
A correction amount is calculated so that the output of is always constant at an appropriate level.

Further, optimum exposure control parameters were selected and converted into control data corresponding to each parameter by the iris data calculation unit 16c, the electronic shutter data calculation unit 16d, and the AGC data calculation unit 16e. After that, it is output to each control unit and an optimum exposure control operation is performed.

Similarly, the output signal of the integration circuit 15 for the video signal divided into screens also changes the electronic image magnification enlarging operation according to the image magnification. Therefore, the intermittent data correction unit 16h corrects the attenuation due to the influence of the non-signal line. After that, it is used as a program AE control signal in the exposure correction data calculation unit 16a,
Effective exposure control operation is performed.

Further, when the electronic image magnification enlarging operation with the image magnification of 2 is performed as described above, the output of the image pickup device is thinned out and read out for each scanning line, and the non-signal line and the presence signal are detected. Although the lines are uniformly present, when the image magnification is lower than 2 times, for example, one signal line is generated every tens of scanning lines, and when the image magnification is high, when the image magnification is high, the scanning line of the signal line is detected. Is less than the number of non-signal lines. In the case of such a halfway image magnification, the number of non-signal lines existing differs depending on the gate position, and the data of the screen division signal obtained from each gate area is different even if a subject having the same brightness on the entire surface is photographed.

Therefore, the amount of attenuation depends on the non-signal line depending on the image magnification and the gate position, and the necessary correction amount also differs depending on each gate position. Therefore, in the intermittent data correction unit 16h, the gate position and the image magnification are changed. A more accurate exposure control operation can be performed by obtaining a correction amount at each gate position from the above and performing the correction.

(Other Embodiments) Next, a second embodiment of the present invention will be described. FIG. 5 is a block diagram showing an example of an image pickup apparatus equipped with an electronic image magnification enlarging means according to the second embodiment of the present invention. The circuit configuration and operation of the focus lens 1 to the integrating circuit 15 and the iris driving circuit 17 are shown in FIG. Similar to the first embodiment of the first embodiment, a system control circuit 20 having an internal process different from that of the system control circuit 16, an integration circuit 18, and a comparison circuit 19 are added.

In the case where the signal obtained by correcting the influence of the non-signal line due to the electronic image magnification enlarging operation on the output signal of the image pickup element as shown in the first embodiment is used for the direct exposure control, the electronic image magnification enlarging operation is performed. Since the image sensor output signal at this time also includes the signal of the portion indicated by the unnecessary area 52a of the image sensor output image 52, the influence of the brightness of the subject that is not displayed in the monitor image 53 output as the standard video signal is affected. As a result, the optimum exposure operation may not be performed on the monitor image 53.

Therefore, in the second embodiment of the present invention, similarly to the conventional example, the output signal of the D / A converter 11 is sequentially supplied to the integrating circuit 18 and the comparing circuit 19 so that the integrating circuit 12 and the comparing circuit 13 are connected to each other. Similarly, after smoothing and comparison processing, it is supplied to the system control circuit 20 and a sufficient dynamic range before signal processing such as gamma correction is ensured.
The output signal of the GC circuit 7 is also supplied to the system control circuit 20 after being subjected to the smoothing and comparison processing as described above in the integrating circuit 12 and the comparing circuit 13.

In the system control circuit 20, the amount of attenuation of the signal of the comparison circuit 13 due to the influence of the non-signal line during the electronic image magnification enlargement operation is adjusted according to the image magnification set by the electronic zoom magnification control unit 20b. Intermittent data correction unit 20
The output from the intermittent data correction unit 20g is compared with the signal from the comparison circuit 19 which is the interpolated signal from the D / A converter 11 in the comparison unit 20h.

In the comparison section 20h, when a high-brightness subject or a subject having a large contrast ratio is photographed, the D / A converter 8
While the signal of the comparison circuit 13 which is the output of the above is the signal of the high luminance part is compressed and clipped, the signal of the comparison circuit 13 which is the output of the AGC circuit 7 before the signal processing such as gamma correction is performed is Since the signal in the high-luminance portion is accurate because the dynamic range is sufficiently secured, high-luminance detection can be performed by comparing the respective signals.
Based on the data obtained by the comparison unit 20h, that is, the high-brightness detection information, the data correction unit 20i and the data correction unit 20j weight the signals of the comparison circuit 19 and the integration circuit 15, which is a screen division signal, respectively, and perform signal processing. Circuit 9
The data of the high-intensity signal part compressed and clipped by is supplemented.

Thus, the exposure correction data calculation unit 20a is based on the data of the data correction unit 20i and the data correction unit 20j.
Optimum exposure data is obtained in step S1 and is output to each control circuit, so even if electronically magnifying the image magnification, the optimum exposure control operation is always performed regardless of the image magnification and the condition of the subject. You can

[0042]

As described above, according to the image pickup apparatus of the present invention, the dynamic range before the signal processing such as gamma correction is ensured, the information of the high luminance signal portion is accurate, and The image signal before being intermittently read out from the image sensor by the operation of the image magnification enlarging means and before being subjected to interpolation and interpolation is corrected for the influence of a no-signal portion caused by the intermittent reading, and then exposed. Since it is used as a control image detection signal, stable and optimal exposure control is always performed on various subjects when the electronic image magnification operation is performed, as is the case when the electronic image magnification operation is not performed. It becomes possible to operate.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of an image pickup apparatus of the present invention.

FIG. 2 is a timing chart showing scanning timing of the image sensor.

FIG. 3 is a conceptual diagram showing an image of a subject.

FIG. 4 is a conceptual diagram showing an example of screen division.

FIG. 5 is a block diagram showing a second embodiment of the image pickup apparatus of the present invention.

[Explanation of symbols]

1 Focus lens 2 Aperture mechanism (iris) 3 Iris drive motor 4 image sensor 5 Scanning timing pulse generator 6 Correlated double sampling circuit 7 Auto gain control circuit 8 A / D converter 9 Signal processing circuit 10 Memory circuit 11 D / A converter 12 Integrator circuit 13 Comparison circuit 14 gate circuit 15 Integrator circuit 16 System control circuit 17 Iris drive circuit 18 Integrating circuit in the second embodiment of the present invention 19 Comparison Circuit in Second Embodiment of the Present Invention 20. System control circuit in the second embodiment of the present invention

Claims (3)

(57) [Claims] 1. An enlarging unit for electronically enlarging a subject image imaged by the image pickup unit by intermittently reading and controlling an image pickup signal output from the image pickup unit according to an electronic zoom magnification, and the enlarging unit. Integrating means for integrating the image pickup signal read out intermittently in accordance with the electronic zoom magnification of a predetermined period, exposure control means for performing exposure control based on the integrated output of the integrating means, and electronic zoom magnification of the enlarging means. In accordance with the above, the image pickup apparatus further comprises a correction unit that corrects an attenuation amount of the integrated output of the integration unit caused by intermittently reading the image pickup signal output from the image pickup unit. 2. The exposure control means according to claim 1, further comprising gate means for dividing an image area into a plurality of areas, and gate integration means for respectively integrating an image pickup signal of each area obtained by the gate means. Is an exposure apparatus, wherein the exposure control is performed by weighting the integrated data of each region obtained by the integrating means in a plurality of photometric modes according to the photometric modes. 3. The image pickup apparatus according to claim 1, wherein the exposure control unit controls at least one of an iris, an AGC, and an electronic shutter.