JPH05260357A - Image pickup device - Google Patents

Abstract

PURPOSE:To keep high adjustment accuracy while decreasing number of picture elements of a face image pickup device provided for automatic focus adjustment and automatic exposure adjustment. CONSTITUTION:A light led from an optical system 1 is separated into a main optical path A and a sub optical path B by a half mirror 2. Then a picture is picked up by a 1st face image pickup device 5 arranged to the main optical path A. On the other hand, a 2nd face image pickup device 8 for image pickup control arranged to the sub optical path B has less picture signal number than that of the 1st face image pickup device 5 and has a small photosensing face size and the light is received via a magnification optical system 6. Then the optically apparent picture element pitch and image pickup area of the 2nd face image pickup device 8 are varied by the setting of zoom magnification in the said magnification optical system 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup device, and in particular,
The present invention relates to a technique for obtaining an image signal for shooting control such as an automatic focus adjustment function and an automatic exposure adjustment function separately from image shooting.

[0002]

2. Description of the Related Art Conventionally, a video camera or a still video camera for converting optical information from a subject into an electric signal by a surface image pickup device (CCD in which pixels are two-dimensionally arranged) has been put into practical use. In such a camera, as a distance-measuring element for automatic focus adjustment (for shooting control), a line imaging device (a CCD in which pixels are arranged in a row, generally called a line sensor) is provided separately from a surface imaging device for shooting. In some cases, the optical information dispersed by the spectroscopic means from the middle of the optical path to the surface imaging device for photographing is converted into one-dimensional image data by the line imaging device.

However, in the line imaging device,
Since only the image on the predetermined line can be obtained,
There is a problem in that the distance measurement position on the screen is restricted on the line, and the degree of freedom in automatic focus adjustment is lacking. Therefore, the applicant of the present invention can perform automatic focus adjustment on the entire screen by using a surface image pickup device having the same photosensitive surface size as the distance measuring element for the automatic focus adjustment. A device with a high degree was previously proposed (Japanese Patent Application No. 3-117481).

[0004]

If a surface image pickup device is provided for automatic focus adjustment as described above, although the degree of freedom in automatic focus adjustment is improved, a surface image pickup device having the same number of pixels as the surface image pickup device for photographing is provided. With a configuration that uses an imaging device,
If a surface imaging device with a reduced number of pixels is used to avoid the cost increase, the pixel pitch will be increased correspondingly, so the resolution will decrease and the performance of automatic focus adjustment will decrease. There was a problem that it would decrease.

Further, in the conventional configuration, when changing the distance measurement range in automatic focus adjustment, it is necessary to electrically process the signal output from the surface image pickup device for automatic focus adjustment. There was a problem that the system became complicated. Further, there is a case where photometry for automatic exposure adjustment is performed using a signal from the surface image pickup device for automatic focus adjustment. In this case also, the signal from the surface image pickup device is electrically changed to change the photometry range. Had to be done by processing.

The present invention has been made in view of the above problems, and even if the number of pixels of a surface image pickup device provided for photographing control such as automatic focus adjustment and automatic exposure adjustment is reduced,
It is an object of the present invention to prevent a decrease in resolution and to enable variable distance measurement and variable photometry range without requiring electrical processing of signals.

[0007]

Therefore, in the image pickup apparatus according to the present invention, the light guided through the optical system is split into at least two main optical paths and sub optical paths by the spectroscopic means, and the light is guided to the main optical path. Arranges a first surface image pickup device for image pickup, and a second image pickup control device on the sub optical path.
The surface imaging device of FIG. Here, the second surface imaging device is a surface imaging device having a pixel pitch equal to or smaller than the first surface imaging device and a photosensitive surface size smaller than that of the first surface imaging device.

Further, as the second surface image pickup device,
A device having a smaller number of pixels than the first surface imaging device is arranged on the sub optical path, and a variable magnification optical means is interposed between the second surface imaging device and the spectroscopic means. Here, the magnification in the variable power optical means may be set to a value corresponding to the pixel pitch ratio between the first surface imaging device and the second surface imaging device.

In addition, in the configuration including the variable power optical means, the number of pixels is smaller than that of the first surface image pickup device.
It is preferable that the surface image pickup device (1) has a pixel pitch equal to or smaller than the first surface image pickup device and has a photosensitive surface size smaller than that of the first surface image pickup device. Further, a device that outputs a color image signal may be used as the first surface imaging device, and a device that outputs a monochrome image signal may be used as the second surface imaging device.

[0010]

According to the image pickup apparatus having such a structure, since the pixel pitch of the second surface image pickup device for image pickup control arranged in the sub optical path is equal to or smaller than the pixel pitch of the first surface image pickup device, It is possible to obtain a resolution equal to or higher than that of the first surface imaging device of. Meanwhile, the second
Since the photosensitive surface size of the surface imaging device is smaller than that of the first surface imaging device, it can be realized as a device having fewer pixels than the first surface imaging device.

On the other hand, a second surface imaging device having a smaller number of pixels than the first surface imaging device is arranged in the sub optical path, and a variable magnification optical means is interposed between the second surface imaging device and the spectroscopic means. According to the mounted structure, if the variable power optical unit is a zoom system, the pixel pitch in the second surface imaging device can be optically changed, and the image can be captured by the second surface imaging device according to the change in magnification. The area can be changed. Further, when the pixel pitches of the first and second surface imaging devices are different, it is possible to optically align the pixel pitches of the first and second surface imaging devices by setting the magnification in the variable power optical means. ..

Here, if the second surface imaging device has a pixel pitch equal to or smaller than the first surface imaging device and the photosensitive surface size is smaller than that of the first surface imaging device, the second surface imaging device. The resolution of the device can be secured to the same level or more as that of the first surface imaging device when the scaling is not performed by the scaling optical means, and the resolution and the imaging region can be changed by changing the magnification.

When a monochrome image signal is sufficient as the information for photographing control, if a device that outputs a monochrome image signal is used as the second surface image pickup device, the first image pickup device for obtaining the color image signal can be obtained. High resolution can be ensured for a surface imaging device even if the number of pixels is small.

[0014]

EXAMPLES Examples of the present invention will be described below. Figure 1
It is a figure which shows the basic composition of the optical system in the Example of the imaging device concerning this invention. Here, the light guided through the photographing optical system 1 including a lens group such as a focus lens and a zoom lens, and the diaphragm 1a is subjected to the main optical path A and the sub optical path by the half mirror 2 as a spectroscopic means. It is split into two, B.

An optical low-pass filter 3, an infrared cut filter (IR filter) 4, a first surface image pickup device 5 are provided in the main optical path which passes through the half mirror 2 and goes straight.
(CCDs having a plane structure) are arranged in this order. Therefore,
The optical image from the optical system 1 is received by the first surface imaging device 5 via the optical low-pass filter 3 and the infrared cut filter 4, and the first surface imaging device 5 photoelectrically converts the received optical image. And image signal (color image signal)
Output as.

On the other hand, in the sub optical path which is reflected by the half mirror 2 and advances in the direction orthogonal to the main optical path, the variable magnification optical system 6, the infrared cut filter 7, the second surface image pickup device 8 (the CCD having the surface structure) ) Are arranged in this order. Therefore, the second surface image pickup device 8 receives the optical image from the optical system 1 through the variable power optical system 6 (magnification changing optical means) and the infrared cut filter 7, and the second surface image pickup device 8 is received.
Photoelectrically converts the received optical image and outputs it as an image signal.

Incidentally, the first and second surface image pickup devices 5,
Of the eight, the first surface imaging device 5 is provided for actual image capturing as will be described later, while the second surface imaging device 8 is used for automatic focusing (AF).
It is provided for shooting control such as automatic exposure adjustment (AE). Further, in the first surface imaging device 5 for image capturing, the optical low-pass filter 3 is provided to prevent the occurrence of color bleeding, but in the second surface imaging device 8 for imaging control, In order to improve the control accuracy by utilizing the high frequency component, the optical low pass filter is not arranged in the optical path.

FIG. 2 is a block diagram showing the overall construction of an image pickup apparatus using the optical system portion shown in FIG. The first
The surface image pickup device 5 is driven by the CCD drive circuit (1) 11, and its output signal is the process circuit (1) 12,
After passing through the image signal processing circuit (1) 13, it is output as a high quality color image signal.

On the other hand, the second surface imaging device 8 has a C
It is driven by a CD drive circuit (2) 14, and its output signal is a process circuit (2) 15 and an image signal processing circuit (2) 16
After passing through the AE (automatic exposure adjustment) processing circuit 17, AF
The signals are output to the (automatic focus adjustment) processing circuit 18 and the AWB (automatic white balance adjustment) processing circuit 19, respectively. Then, from the AE processing circuit 17, the AF processing circuit 18, and the AWB processing circuit 19, photometric information, distance measuring information (focus information), and color temperature information are output to the CPU 20, respectively.

The CPU 20 controls the AF motor 21 and the diaphragm motor 22 of the optical system 1 based on the input information and also controls the electronic shutter speed and the like in the CCD drive circuit (1) 11. Further, in response to a signal from a zoom switch (not shown), the zoom motor 23 of the optical system 1 is controlled, and if the zoom optical system 6 is a zoom system, the zoom motor 24 is controlled to control the zoom optical system. The magnification in 6 is also set.

Next, a specific configuration of AF (automatic focus adjustment) will be described. Generally, the range-finding range in the case of AF does not have to be the entire image. In the case of passive AF as in the present embodiment, the central part of the image in which the main subject is highly likely to be located is usually set as the range-finding range. I often do it. Therefore, when the surface imaging device 8 is used for AF as in the present embodiment, it is not necessary to have the same photosensitive surface size as the surface imaging device 5 for image capturing, and the first surface imaging device 5 captures an image. Any small photosensitive surface size that can capture only the central portion of the image area (imaging area) may be used (see FIG. 3).

For example, the first and second surface image pickup devices 5,
8 has the same pixel pitch, and the second surface imaging device 8
If the photosensitive surface size is 1/9 of the first surface imaging device 5, and the number of pixels of the first surface imaging device 5 is 900,000, the second surface imaging device 8 has the same resolution.
The second area imaging device 8 can be realized with 100,000 pixels (900,000 pixels / 9), and the image of the necessary area (1/9 area in the center of the screen) can be captured with the same resolution as that of the first area imaging device 5. The cost can be significantly reduced.

That is, since it is sufficient to use a surface image pickup device having a photosensitive surface size of about 1/9 for AF,
Even if the pixel pitch is equal to or less than that of the surface imaging device for image capturing, the required number of pixels in the second surface imaging device 8 may be significantly smaller than that in the first surface imaging device 5, and the present embodiment In the example, by using the second surface imaging device 8 having such a pixel pitch and photosensitive surface size, the cost of the surface imaging device 8 for shooting control is reduced while ensuring high AF accuracy.

The above-described operation can be obtained even if the variable power optical system 6 is omitted. Further, the variable power optical system 6 of the zoom system is further provided.
4, the range can be changed by changing the magnification, as shown in FIG. 4, and AF control with different characteristics becomes possible. Here, the distance measurement area (second surface imaging device 8
If the surface imaging device having the same pixel pitch is used, the second surface imaging device 8 is optically different from the first surface imaging device 5 by making the imaging area) smaller.
This is the same as the reduction of the pixel pitch of, and the resolution can be further improved. Therefore, when the distance measuring area may be reduced, the AF control can be performed with higher accuracy in the narrow area.

On the other hand, by changing the magnification of the variable power optical system 6,
If the distance measurement area is increased, the pixel pitch of the second surface imaging device 8 is optically increased with respect to the first surface imaging device 5 even if surface imaging devices having the same pixel pitch are used. Although the same as the above, the resolution decreases, but a wider range can be set as the distance measurement area. Further, when performing AF control, color information is not generally required, and a monochrome image signal (luminance signal) is sufficient. Therefore, a color image signal is output as the first surface imaging device 5 for color image capturing. Even when using, the second surface imaging device 8 for AF control is
Only black and white can be used. If the second surface imaging device 8 is exclusively used for black and white, the resolution can be further increased as compared with the surface imaging device for color with the same pixel pitch, thereby improving the accuracy of AF control. You can

As described above, the apparent correlation between the pixel pitches can be changed by setting the magnification of the variable power optical system 6, so that the pixel pitch is larger than that of the first surface imaging device 5, for example. Even when the second surface image pickup device 8 is used, the magnification of the variable power optical system 6 is narrowed in the direction (TEL) in which the distance measuring area is narrowed according to the pixel pitch ratio.
If it is set to the E side), the pixel pitch can be optically made approximately the same in appearance.

Therefore, even if a surface image pickup device having a pixel pitch relatively larger than that of the first surface image pickup device 5 is used as the second surface image pickup device 8, by providing the variable power optical system 6, It is possible to obtain the same resolution as that of the surface imaging device 5 and to perform AF control with high accuracy.
As described above, when the magnification is set according to the pixel pitch ratio of the double-sided image pickup device and the pixel pitch is apparently about the same, the variable magnification optical system 6 is not a zoom system but a fixed magnification. May be

As described above, by selecting the combination of the first surface imaging device 5 and the second surface imaging device 8 having different pixel pitches and photosensitive screen sizes and the zoom magnification of the variable power optical system 6, The distance measurement area (the imaging area of the second surface imaging device 8) and the resolution can be arbitrarily changed, and the surface imaging device for black and white has a small number of pixels, and the surface for image capturing has a large number of pixels for color. A resolution equal to or higher than that of the image pickup device can be obtained, and high-precision AF can be realized at low cost.

Since the automatic exposure adjustment (AE) and the automatic white balance adjustment (AWB) do not require high resolution unlike the distance measurement in AF (automatic focus adjustment), the pixel pitch in the second surface image pickup device 8 is not required. Is relatively large is acceptable. Therefore, the zoom magnification of the variable power optical system 6 is set to the wide side, and the same image as that of the first surface imaging device 5 is captured by the second surface imaging device 8 having a small photosensitive surface size, and the average photometry is performed. However, although the resolution is lowered, the necessary automatic exposure adjustment (AE) and automatic white balance adjustment can be performed.

On the contrary, if the zoom magnification of the variable power optical system 6 is set to the telephoto side, only a part of the image picked up by the first surface image pickup device 5 is picked up by the second surface image pickup device 8. Then, spot photometry can be performed (see FIG. 5). In this way, by changing the zoom magnification of the variable power optical system 6, in automatic exposure adjustment (AE) and automatic white balance adjustment (AWB), the photometric and colorimetric areas are displayed in a manner other than electrical processing of image signals. 5, the second surface imaging device 8 having a photosensitive surface size smaller than that of the first surface imaging device 5 can be optically changed to easily switch between spot metering and average metering. You can do it. Further, the resolution also changes in accordance with the change of the photometric and colorimetric areas.

[0031]

As described above, according to the image pickup apparatus of the present invention, the second surface image pickup device having a smaller number of pixels than the first surface image pickup device for image capturing is used, and the automatic focusing is performed with high accuracy. It becomes possible to perform the adjustment, and by providing the variable power optical means, it is possible to easily change the range and resolution of the distance measurement, photometry and color measurement in the second surface imaging device. is there.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an optical portion in an embodiment of an image pickup apparatus according to the present invention.

FIG. 2 is a block diagram showing an overall configuration including a control circuit according to an embodiment.

FIG. 3 is a diagram showing a difference in photosensitive surface size between surface imaging devices.

FIG. 4 is a diagram showing a change in a distance measuring area using a variable power optical system.

FIG. 5 is a diagram showing a change in a photometric area using a variable power optical system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical system 2 Half mirror 5 1st surface imaging device 6 Variable magnification optical system 8 2nd surface imaging device

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H04N 5/335 Z

Claims (5)

[Claims] 1. A spectroscopic unit that splits light guided through an optical system into at least two main optical paths and a sub optical path, and a first surface imaging device for image capturing arranged on the main optical path. A second surface imaging device arranged on the sub optical path, having a pixel pitch equal to or smaller than the first surface imaging device and having a photosensitive surface size smaller than that of the first surface imaging device, An imaging device configured to include. 2. A spectroscopic unit for splitting light guided through an optical system into at least two main optical paths and a sub optical path, and a first surface imaging device for image capturing arranged on the main optical path. A second surface imaging device that is arranged on the sub optical path and has a smaller number of pixels than the first surface imaging device, and is interposed between the spectroscopic unit and the second surface imaging device. And an image pickup device including: 3. The image pickup according to claim 2, wherein the variable power optical means is set to a magnification corresponding to a pixel pitch ratio between the first surface image pickup device and the second surface image pickup device. apparatus. 4. The second surface image pickup device, wherein the pixel pitch is equal to or smaller than the first surface image pickup device, and the photosensitive surface size is smaller than that of the first surface image pickup device. 3. The image pickup device according to item 3. 5. The first surface imaging device is a surface imaging device that outputs a color image signal, and the second surface imaging device is a surface imaging device that outputs a monochrome image signal. Item 5. The image pickup device according to any one of items 1, 2, 3 and 4.