JPH118803A - Camera having solid-state image pickup device for image receiving - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a camera which has a solid-state image pickup device that does not damage an image quality and an image receiving means even when a diaphragm is used to limit quantity of light. SOLUTION: This camera is provided with image pickup lens (1) which constitute an optical system that forms an optical image about an object on an image forming plane, diaphragm means 2 which is provided with an aperture and controls incident light quantity to a solid-state image pickup device and the solid-state image pickup device which photoelectrically converts the optical image about the object and generates an image signal. The solid-state image pickup device whose pixel pitch is equal to or less than 7.0 μm. The solid-state image pickup device whose diaphragm value at the time of minimum diaphragm of the means 2 is less than 5.6 is an image receiving means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera using a solid-state image sensor as an image receiving means, and more particularly, to a solid-state image sensor for receiving an optical image obtained through an imaging lens by the solid-state image sensor and treating the image as digital data. The present invention relates to a camera as image receiving means.

[0002]

2. Description of the Related Art A camera using a solid-state image pickup device as an image receiving means is configured to photoelectrically convert an optical image obtained through an image pickup lens by a solid-state image pickup device such as a CCD and to handle the obtained image signal as digital data. .

In recent years, the number of pixels in a CCD has been increased in order to increase the resolution, and the size of the CCD has also been reduced. As a result, the pixel pitch of the CCD has become very small.

As one of the improvements in image quality, a diaphragm means is used in order to optimize the amount of light incident on the CCD similarly to a normal silver halide camera.

[0005]

In such a camera using a solid-state image sensor using a CCD having a small pixel pitch as an image receiving means, it is considered that the resolution is increased and the image quality is improved with an increase in the number of pixels of the CCD. Was.

However, when a small aperture is used to limit the amount of light incident on the CCD, diffraction occurs to degrade the MTF characteristics of the photographing optical system, resulting in a decrease in resolution and contrast of an obtained image, thereby improving image quality. It turned out to be a hindrance.

Accordingly, it is an object of the present invention to realize a camera using a solid-state image sensor as an image receiving means, which does not impair the image quality even when an aperture is used for limiting the amount of light.

[0008]

As a result of intensive studies on the above-mentioned problems, it has been found that a specific relationship regarding the image quality is established between the pixel pitch of the solid-state imaging device and the aperture value. A new configuration has been found that does not impair image quality even when an aperture is used due to the limitation of.

(1) According to the first aspect of the present invention, an image pickup lens constituting an optical system for forming an optical image of a subject on an image forming surface, and an image signal is generated by photoelectrically converting the optical image of the subject. A solid-state imaging device having a pixel pitch of 7.0 μm or less and an opening, and controlling the area of the opening to control the amount of light incident on the solid-state imaging device. And a diaphragm means having a diameter of less than 6. The camera has a solid-state imaging device as an image receiving means.

In the camera using the solid-state image pickup device as an image receiving means, when the pixel pitch of the solid-state image pickup device is 7.0 μm or less, the aperture value at the minimum stop of the stop means is set to less than 5.6. Therefore, even when an aperture is used for the restriction, the reduction in resolution and contrast due to the influence of diffraction can be suppressed to the minimum, and a camera using a solid-state imaging device that does not impair the image quality can be realized.

(2) The invention according to claim 2 is characterized in that, in the camera using the solid-state image sensor of (1) as an image receiving means, the pixel pitch of the solid-state image sensor is 5.0 μm or less.

In a camera using this solid-state image sensing device as an image receiving means, since the pixel pitch of the solid-state image sensing device is 5.0 μm or less, when an aperture is used to limit the amount of light, the resolution and contrast due to the influence of diffraction are increased. The effect of suppressing the decrease in image quality is remarkably recognized, and it is possible to realize a camera using a solid-state imaging device that does not impair image quality as an image receiving unit.

(3) According to a third aspect of the present invention, an image pickup lens constituting an optical system for forming an optical image of a subject on an image forming surface, and an image signal is generated by photoelectrically converting the optical image of the subject. A solid-state imaging device having a pixel pitch of 7.0 μm or less, an aperture provided, aperture means for controlling the area of the aperture to control the amount of light incident on the solid-state imaging element, and light passing through the aperture means. And a diffraction effect correcting means for correcting the effect of light diffraction. This is a camera using a solid-state imaging device as an image receiving means.

In the camera using the solid-state image sensing device as an image receiving means, the pixel pitch of the solid-state image sensing device is 7.0 μm or less and the effect of diffraction is corrected by the diffraction effect correcting means. Even when an aperture is used, a decrease in resolution and contrast due to the influence of diffraction can be suppressed to a minimum, and a camera using a solid-state imaging device that does not impair image quality can be realized.

(4) The invention according to claim 4 is the camera having the solid-state image pickup device of (3) as an image receiving means, wherein the diffraction effect correcting means is an image processing means for performing image processing on the image signal. It is characterized by the following.

In the camera using the solid-state image pickup device as an image receiving means, the image processing means performs image processing on the image signal to correct the influence of diffraction. In addition, a decrease in resolution and contrast due to the influence of diffraction can be suppressed to a minimum, and a camera using a solid-state imaging device that does not impair image quality as an image receiving means can be realized.

(5) The camera according to the fifth aspect of the present invention, wherein the solid-state imaging device according to (4) is an image receiving means, wherein the image processing means performs image processing for enhancing a high frequency component of the image signal. It is characterized by.

In the camera using the solid-state image pickup device as an image receiving means, the image processing means performs image processing for emphasizing the high frequency component of the image signal to correct the influence of diffraction. In the case of using a solid-state image sensor, the reduction in resolution and contrast due to the influence of diffraction can be suppressed to a minimum, and a camera using a solid-state image sensor that does not impair the image quality can be realized.

(6) The invention according to claim 6 is the camera according to (5), wherein the solid-state imaging device has an image receiving means, wherein the solid-state imaging device has a pixel pitch of 5.0 μm or less. .

In the camera using the solid-state image pickup device as an image receiving means, the image processing means performs image processing for emphasizing the high-frequency component of the image signal, thereby correcting the influence of diffraction.
Since the pixel pitch of the solid-state imaging device is 5.0 μm or less, when a stop is used to restrict the amount of light, the effect of suppressing a decrease in resolution and contrast due to diffraction is remarkably recognized, and image quality is not impaired. A camera using a solid-state imaging device as an image receiving means can be realized.

(7) According to a seventh aspect of the present invention, an image pickup lens constituting an optical system for forming an optical image of a subject on an image forming surface, and an image signal is generated by photoelectrically converting the optical image of the subject. A solid-state imaging device having a pixel pitch of 7.0 μm or less, and filter means for controlling the light transmittance to control the amount of light incident on the solid-state imaging device. This is a camera using a solid-state imaging device as an image receiving means.

In the camera using the solid-state image sensing device as an image receiving means, the pixel pitch of the solid-state image sensing device is 7.0 μm or less, and the filter means is used to limit the light quantity. A decrease in contrast can be suppressed to a minimum, and a camera using a solid-state imaging device that does not impair image quality as an image receiving means can be realized.

(8) The invention according to claim 8 is the camera according to (7) wherein the solid-state imaging device is used as an image receiving means, wherein an opening is provided, and the area of the opening is controlled to control the solid-state imaging device. Diaphragm means for controlling the amount of incident light,
The aperture value of the aperture means at the time of minimum aperture is less than 5.6.

In the camera using the solid-state image pickup device as an image receiving means, the pixel pitch of the solid-state image pickup device is 7.0 μm or less, and the aperture value of the minimum stop of the stop means is set to less than 5.6 to further limit the light quantity. Therefore, a reduction in resolution and contrast due to the influence of diffraction can be suppressed to a minimum, and a camera using a solid-state imaging device that does not impair image quality as image receiving means can be realized.

(9) The invention according to claim 9 is the camera according to (7), wherein the solid-state image sensor is used as an image receiving means, wherein an opening is provided, and the area of the opening is controlled to control the solid-state image sensor. Diaphragm means for controlling the amount of incident light,
When the aperture value of the diaphragm unit is 5.6 or more, the amount of light incident on the solid-state imaging device is controlled by controlling the transmittance of the filter unit and controlling the aperture area of the diaphragm unit. .

In the camera using the solid-state image pickup device as an image receiving means, the light amount is limited when the pixel pitch of the solid-state image pickup device is 7.0 μm or less and the aperture value at the time of the minimum stop of the stop means is 5.6 or more. Therefore, compared with the case where no filter means is used, the value of the aperture value is hardly increased, and the reduction in resolution and contrast due to the influence of diffraction can be minimized, and the image quality can be reduced. A camera using an intact solid-state imaging device as an image receiving means can be realized.

(10) According to a tenth aspect of the present invention, there is provided an image pickup lens constituting an optical system for forming an optical image of a subject on an image forming surface, and an opening, and by controlling the area of the opening, Diaphragm means for controlling the amount of light incident on the solid-state imaging device; a solid-state imaging device having a pixel pitch of 7.0 μm or less for photoelectrically converting an optical image of the subject to generate an image signal; and processing the image signal Signal processing means, wherein when the aperture value of the aperture means is 5.6 or more, the signal processing means performs a process of emphasizing a high frequency component of the image signal. This is a camera using a solid-state imaging device as an image receiving means.

In the camera using the solid-state image sensor as an image receiving means, when the pixel pitch of the solid-state image sensor is 7.0 μm or less, and when the aperture value of the minimum aperture of the aperture means is 5.6 or more, As a result of performing the process of emphasizing the high-frequency components of the image signal, even when an aperture of F5.6 or more is used to restrict the amount of light, a decrease in resolution and contrast due to attenuation of high-frequency components due to diffraction is minimized. It is possible to realize a camera that uses a solid-state image sensor that does not impair image quality as an image receiving unit.

As a result, even when an aperture is used to limit the amount of light, a decrease in resolution and contrast due to the influence of diffraction can be minimized, and a solid-state image sensor that does not impair image quality is used as the image receiving means. A camera can be realized.

(11) The invention according to claim 11 is characterized in that (1)
0) In the camera using the solid-state imaging device as the image receiving means,
The signal processing unit changes a degree of emphasis of a high-frequency component of an image signal according to an aperture value of the aperture unit.

When such image processing is performed, the degree of emphasis of the high-frequency component of the image signal is changed according to the aperture value of the aperture means, so that the aperture value is narrowed down according to the aperture value.
It is possible to compensate for the deterioration of the MTF due to the generated diffraction.

Therefore, it is possible to minimize a decrease in resolution and contrast due to attenuation of high-frequency components due to the influence of diffraction, and it is possible to realize a camera using a solid-state image sensor that does not impair image quality as an image receiving unit.

(12) According to a twelfth aspect of the present invention, there is provided an image pickup lens constituting an optical system for forming an optical image of a subject on an image forming surface, a light amount controlling means for controlling an amount of light incident on the image forming surface, A solid-state imaging device having a pixel pitch of 7.0 μm or less for photoelectrically converting an optical image of the subject to generate an image signal; and a signal processing unit for processing the image signal; The first light quantity control means comprises: first light quantity control means for controlling the incident light quantity by controlling the area; and second light quantity control means for controlling the incident light quantity irrespective of the opening area. The aperture value at the time of the minimum aperture is set to less than 5.6. This is a camera using a solid-state imaging device as an image receiving means.

In the camera using the solid-state image pickup device as an image receiving means, when the pixel pitch of the solid-state image pickup device is 7.0 μm or less, the aperture value of the first light amount control means at the minimum stop is set to less than 5.6. As a result, the second light quantity control means for controlling the light quantity irrespective of the aperture area is used together. As a result, even when the light quantity control means is used for limiting the light quantity, the resolution and contrast are reduced by the influence of diffraction. Can be minimized, and a camera using a solid-state imaging device that does not impair image quality as an image receiving means can be realized.

Further, by using the second light amount control means independent of the aperture area, sufficient resolution and contrast can be obtained even in a bright environment. (13) According to a thirteenth aspect of the present invention, there is provided an imaging lens constituting an optical system for forming an optical image of an object on an image forming surface, a light amount control unit for controlling an amount of light incident on the image forming surface, and A solid-state imaging device having a pixel pitch of 7.0 μm or less, which photoelectrically converts an optical image to generate an image signal;
Signal processing means for processing the image signal, wherein the light quantity control means controls the aperture area to control the quantity of incident light, and the second light quantity control means controls the quantity of incident light regardless of the aperture area. 2 light amount control means,
When the incident light amount is further limited in a state where the aperture value of the first light amount control means is 5.6 or more, the light amount control of the second light amount control means is used together. This is a camera using a solid-state imaging device as an image receiving means.

In the camera using the solid-state image sensing device as an image receiving means, when the pixel pitch of the solid-state image sensing device is 7.0 μm or less, the first light amount control means is further set to an aperture value of 5.6 or more. When the amount of incident light is limited, the second light amount control means for controlling the amount of light regardless of the aperture area is used together. As a result, even when the light amount control means is used to limit the amount of light, Thus, a decrease in resolution and contrast due to the influence of diffraction can be suppressed as compared with the case of a single aperture stop, and a camera using a solid-state image sensor that does not impair the image quality can be realized.

Further, by using the second light amount control means independent of the aperture area, a sufficient resolution and contrast can be obtained even in a bright environment. (14) The invention according to claim 14 provides (10) to (13)
Wherein the pixel pitch of the solid-state imaging device is 5.0 μm or less.

In the camera using the solid-state image sensing device as an image receiving means, the pixel pitch of the solid-state image sensing device is 5.0 μm or less. The effect of suppressing the decrease in image quality is remarkably recognized, and it is possible to realize a camera using a solid-state imaging device that does not impair image quality as an image receiving unit.

(15) The invention according to claim 15 is characterized in that (1)
2) to (14), wherein the second light amount control means is an ND filter.

In the camera using the solid-state image pickup device as an image receiving means, since the ND filter is used as the second light amount control means, it is possible to control the light amount irrespective of the aperture area. A reduction in resolution and contrast due to the influence of diffraction can be suppressed more than in the case of a single unit, and a camera using a solid-state imaging device that does not impair image quality as image receiving means can be realized.

(16) The invention according to claim 16 is characterized in that (1)
2) to (14), wherein the second light quantity control means is a variable density transmittance control means in the camera using the solid-state imaging device as an image receiving means.

In the camera using the solid-state image pickup device as the image receiving means, the variable density transmittance control means is used as the second light quantity control means, so that the light quantity can be controlled regardless of the aperture area. In addition, a reduction in resolution and contrast due to the influence of diffraction can be suppressed more than in the case of a single aperture stop due to the aperture area, and a camera using a solid-state image pickup device that does not impair image quality can be realized.

(17) The invention according to claim 17 is characterized in that (1)
2) to (14), wherein the second light amount control means is a shutter speed control means of the solid-state imaging device.

In the camera using the solid-state imaging device as the image receiving means, since the shutter speed control means is used as the second light quantity control means, the light quantity control can be performed regardless of the aperture area. Thus, a decrease in resolution and contrast due to the influence of diffraction can be suppressed as compared with the case of a single aperture stop, and a camera using a solid-state image sensor that does not impair the image quality can be realized.

[0045]

Embodiments of the present invention will be described below in detail. In the present embodiment, an electronic still camera will be described as an example of a camera using a solid-state imaging device as an image receiving unit.

<Structure of Electronic Still Camera> First, the structure of the electronic still camera used in the present embodiment will be described with reference to FIG.

FIG. 1 is a functional block diagram showing the overall electrical schematic configuration of an electronic still camera according to an embodiment of the present invention. In the electronic still camera shown in FIG. 1, a light image obtained through an optical system including a lens 1, an aperture stop 2, and the like is formed on a light receiving surface of an image sensor 3 such as a CCD. At this time, the lens 1 and the aperture stop 2
Focus drive circuit 16 and aperture drive circuit 15
Driven by The aperture stop 2 constitutes first light amount control means.

Here, the image sensor 3 photoelectrically converts the light image formed on the light receiving surface into an electric charge amount, and outputs an analog image signal by a transfer pulse from the image sensor driving circuit 19. Note that the image sensor driving circuit 19 can control the shutter speed while driving the image sensor 3.
A second light amount control unit that limits the amount of incident light regardless of the opening area is configured.

The output analog image signal is subjected to CDS (correlated double sampling) in the pre-processing circuit 4.
The noise is reduced by the processing, the gain is adjusted by the AGC, and the processing for expanding the dynamic range is performed.

After being converted into a digital image signal by the A / D converter 5, the signal processing circuit 6 performs luminance processing and color processing on the digital video signal (for example, a luminance signal (Y) and a color difference signal ( Cr, Cb)) and output to the memory controller 7. Further, in the signal processing circuit 6, an image signal for emphasizing a high frequency component of the image signal is performed as needed.

On the other hand, the signal processing circuit 6 also has a built-in D / A converter, and receives a colorized video signal input from the A / D converter 5 and a reverse input from the memory controller 7. Image data can be output as an analog video signal.

These functions are switched by exchanging data with the main microcomputer 8, and the exposure information, the focus signal, and the white balance information of the image sensor signal can be output to the main microcomputer 8 as needed.

The main microcomputer 8 is mainly used for photographing,
The sequence of recording and reproduction is controlled, and further, as necessary, compression and reproduction of the photographed image and serial port transmission with an external device are performed. Here, ITU-T and ISO are used as image compression.
Use the JPEG or JBIG standardized by

The memory controller 7 stores the digital image data input from the signal processing circuit 6 in the frame memory 9 or outputs the image data in the frame memory 9 to the signal processing circuit 6.

The frame memory 9 is an image memory capable of storing image data of at least one screen. For example, VRAM, SRAM, DRAM and the like are generally used. Here, VRAM which can operate independently of the CPU bus is used. doing.

The image storage memory 10 is a memory incorporated in the main body, and stores image data stored in the frame memory 9 that has been subjected to image compression processing or the like by the main microcomputer 8. As the image storage memory 10,
For example, an SRAM, a DRAM, an EEPROM or the like is used, but an EEPROM is preferable in consideration of storing image data in the memory.

A PC card controller (PCMCIA controller) 11 is a PC memory card (hereinafter simply referred to as PC).
The main microcomputer 8 connects an external recording medium such as a card) to the main microcomputer 8. After the image stored in the frame memory 9 is subjected to image compression processing or the like by the main microcomputer 8, the image is transmitted through the controller 11. Recorded on an external storage medium. An external storage PC card connected via the PC card controller 11 is an SRAM card.
A card, a DRAM card, an EEPROM card, or the like can be used, and image data can be directly transferred to a remote storage medium via a public line using a modem card or an ISDN card.

The flash timing of the strobe 12 can be obtained by the main microcomputer 8 which controls the photographing sequence. The serial port driver 13 performs signal conversion for performing information transmission between the camera body and information between external devices. As the serial transmission means, RS23
There are recommended standards for performing serial communication such as 2C and RS422A, but here, RS232C is used.

The sub-microcomputer 14 controls man-machine interfaces such as operation switches of the camera body and a liquid crystal display, and transmits information to the main microcomputer 8 as needed. Here, a serial input / output terminal is used for transmitting information to and from the main microcomputer 8. It also has a built-in clock function and controls auto-date.

The aperture drive circuit 15 is constituted by, for example, an auto iris and the like, and changes the aperture value of the optical aperture 2 under the control of the main microcomputer 8. The aperture value is synonymous with the F number (F No.). = F / D (where D is the effective diameter of an optical system composed of a lens and a diaphragm, f
Is the focal length of the lens).

The focus drive circuit 16 is constituted by, for example, a stepping motor, and changes the lens position under the control of the main microcomputer 8 so that the optical focus surface of the subject is appropriately adjusted on the image sensor 3. 18
Is a liquid crystal display connected to the sub-microcomputer 14 and displaying various information such as photographing information.

Although the configuration shown in FIG. 1 shows a case where the main microcomputer 8 compresses and decompresses an image, a dedicated circuit for compression / decompression may be arranged on the CPU bus.

<Basic Operation of Electronic Still Camera>
A series of operations from shooting to memory recording will be described. The operation mode of the camera is set based on various switch information connected to the sub-microcomputer 14, and information for photographing is input to the main microcomputer 8 as serial information.

In response to this information, the main microcomputer 8
The memory controller 7 and the serial port driver 13 are set. When the release switch on the sub-microcomputer 14 is pressed, the sub-microcomputer 14 issues a first switch signal S1
Is activated, issues an image input command to the signal processing circuit 6, and the signal processing circuit 6 operates the image sensor 3, the pre-processing circuit 4, and the A / D converter 5 to receive image data.

The received image data is transmitted to the signal processing circuit 6.
After performing basic signal processing, focus information is created from high-frequency components of luminance data, and exposure data is created from low-frequency components. The main microcomputer 8 reads these data from the signal processing circuit 6, and performs aperture driving, focus driving, and the AG of the pre-processing circuit 4 as necessary.
The gain of the C amplifier is controlled so that proper exposure and focus can be obtained. Further, depending on the operation mode, an analog image signal can be output from the signal processing circuit 6 via the video amplifier 17 as an NTSC video signal.

When the signal indicating that the second release switch signal S2 has been pressed is input from the sub-microcomputer 14 to the main microcomputer 8 after the exposure value and the focus have been adjusted to appropriate values, the main microcomputer 8 It outputs a data capture instruction to the memory controller 7. Also, if necessary, a light emission signal is output to the strobe 12 at the field timing of the captured image. Memory controller 7
Receives a command to capture an image, detects a synchronization signal from the signal processing circuit 6, and captures image data in the Y, Cr, Cb format or the like output from the signal processing circuit 6 at a predetermined timing into the frame memory 9. .

When the image capture to the frame memory 9 is completed, the memory controller 7 displays a status indicating that the capture has been completed, and the main microcomputer 8 reads the status. Know. After the photographing is completed, the main microcomputer 8 performs image compression as necessary, and transfers the image data to the image storage memory 10, an externally connected IC card, or a personal computer or the like connected to an external serial port. I do.

In the reproduction display operation, the main microcomputer 8
Image data is read from the image storage memory 10, an externally connected IC card, or a personal computer connected to an external serial port, the image is expanded if necessary, and written to the frame memory 9. Thereafter, the image data is read by the signal processing circuit 6 and the memory controller 7, and an analog signal of the image is output to the output terminal via the signal processing circuit 6. In this way, the functions of photographing, recording, reproducing, displaying and transmitting of the camera are achieved.

In this embodiment, it has been found that a specific relationship is established between the pixel pitch of the CCD and the aperture value with respect to the image quality. In particular, when the pixel pitch of the CCD is 7.0 μm or less. In addition, the aperture value of the aperture stop 2 at the time of the minimum stop is configured to be less than 5.6.

With this configuration, even when the aperture stop 2 is used to limit the amount of light, the reduction in resolution and contrast due to the influence of diffraction can be suppressed to the minimum, and the electron quality does not impair the image quality. A still camera can be realized.

In the electronic still camera having such a configuration, when the aperture value of the aperture stop 2 is set to 5.6 or more, the signal processing circuit 6 performs processing for emphasizing the high frequency component of the image signal. I do.

The emphasis processing of the high frequency component is performed by hardware,
It may be performed by any of software. Also,
Various known methods can be used as an emphasis processing method of the high frequency component. By using a convolution filter, the high frequency component can be accurately processed. In addition, Fourier transform can be used as an emphasis processing method for high frequency components.

As a result of performing such a process of emphasizing the high-frequency component of the image signal, even when an aperture of F5.6 or more is used to restrict the amount of light, the MTF characteristic of the photographing optical system deteriorates due to the influence of diffraction. Therefore, a decrease in the resolution and contrast of the image caused by the above can be compensated and minimized, and an electronic still camera that does not impair the image quality can be realized.

Also, as the aperture value increases, the MT due to diffraction increases.
Since the deterioration of F becomes large, the degree of emphasis of the high-frequency component is changed according to the aperture value. In particular, the main microcomputer 8 increases the degree of emphasis as the aperture value increases.
May perform the control.

Also, as shown in FIG. 4, an aperture stop 2 for controlling the amount of incident light by controlling the aperture area, an ND filter for controlling the amount of incident light regardless of the aperture area, and a variable transmittance The aperture value at the time of the minimum aperture stop of the aperture stop 2 is configured to be less than 5.6 by using a light amount control means such as a liquid crystal and an electronic shutter.

With this configuration, even when the aperture stop 2 is used to limit the amount of light, a decrease in image resolution and contrast caused by deterioration of the MTF characteristic of the photographing optical system due to the influence of diffraction is minimized. It is possible to realize an electronic still camera that does not impair image quality. Since the incident light amount is controlled regardless of the aperture area in combination with the aperture stop 2, the light amount control can be performed in a wide range.

As another example of the light quantity control means, when the aperture value of the aperture stop 2 for controlling the incident light quantity by controlling the aperture area is 5.6 or more, the incident light quantity is controlled irrespective of the aperture area. A light amount control means such as an ND filter, a liquid crystal having a variable transmittance, and an electronic shutter is used in combination.

With this configuration, even when the aperture stop 2 is used to limit the amount of light, the M of the photographing optical system due to the influence of diffraction is smaller than that of the aperture stop alone due to the aperture area.
It is possible to suppress a decrease in the resolution and contrast of the image due to the deterioration of the TF characteristic, and to realize an electronic still camera that does not impair the image quality. Since the incident light amount is controlled regardless of the aperture area in combination with the aperture stop 2, the light amount control can be performed in a wide range.

Further, as shown in FIG. 5, instead of the aperture stop 2 for controlling the amount of incident light by controlling the aperture area, the amount of incident light is controlled irrespective of the aperture area as shown in FIG.
A D filter, a liquid crystal having a variable transmittance, an electronic shutter, or the like can be used as the light amount control means.

With this configuration, since the aperture area does not change due to the limitation of the light amount, the resolution of the image due to the deterioration of the MTF characteristic of the photographing optical system due to the influence of diffraction can be improved.
An electronic still camera which can prevent a decrease in contrast and does not impair image quality can be realized. Since the incident light amount is controlled regardless of the aperture area in combination with the aperture stop 2, the light amount control can be performed in a wide range.

In the case described above, the effect was obtained when the pixel pitch of the CCD was 7.0 μm. However, a greater effect was obtained when the pixel pitch was 5.0 μm or less.

[0082]

The following is a detailed verification of the above-described embodiment using an example and a comparative example.

FIG. 2 is a lens arrangement diagram showing the overall optical schematic configuration of the electronic still camera according to the embodiment of the present invention.
2, the electronic still camera 30 includes a lens system 31 described as the lens 1 in FIG.
D, a signal processing system 32 including the signal processing circuit described in FIG.
It is composed of

The optical system 31 is configured to pass through the seven imaging lenses, further pass through the infrared cut filter RF, the optical low-pass filter LF, and the cover glass CG to form an image on the solid-state imaging device CCD. ing.

In the description of this embodiment, the solid-state imaging device CCD used for evaluation as the present embodiment and a comparative example
The following will be used. Sony Corporation's ICX084K (trade name): 1/3 inch light-receiving surface, approximately 330,000 pixels, pixel pitch 7.5 μm Sony Corporation's ICX089AK (trade name): light-receiving surface 1/4 inch, approximately 330,000 pixels Pitch: 5.6 μm MN3773 (trade name) manufactured by Matsushita Electronics Corporation: 1 / 2.72 inch light receiving surface, approximately 1 million pixels, pixel pitch: 4.6 μm. Here, the pixel pitch is adjacent to the image sensor. It refers to the distance between the centers of the two light receiving elements, and if different between the horizontal and vertical directions, it refers to the shorter distance.

FIG. 3 is a sectional view of an optical system of an imaging lens used in the following examples. Table 1 shows optical data of this example. In this embodiment, the aperture stop is located at a position 1.2 mm behind the eighth surface.

Where f is the focal length (mm), F is the aperture value, R is the radius (mm), D is the interval (mm), Nd is the refractive index,
νd is the Abbe number of the d-line, and P is the minimum pitch (mm) between pixels of the solid-state imaging device.

The surface numbers of the lenses in FIG. 3 correspond to the surface numbers of the lenses in Table 1. This imaging lens is a detailed specific example of the optical system 31 described above.

[0089]

[Table 1]

The performance of this imaging lens is shown below. Resolution (center) = 160 lines / mm or more Resolution (peripheral) = 100 lines / mm or more Here, 2 × (1 / (2P)) = 135 lines / mm 2.35 × (1 / (2P)) = 158 0.8 lines / mm 1.3 × (1 / (2P)) = 87.8 lines / mm

As shown in FIG. 4, the aperture stop 2 has an aperture of F2.8, an aperture of F4, and an exposure multiple of 2.
(ND2) filter provided with F4 aperture (F5.
6), an aperture of F4 (equivalent to F8) provided with a filter of an exposure multiple of 4 (ND4), and an exposure multiple of 8 (ND8)
F4 opening (equivalent to F11) provided with a filter of
Aperture / transmittance stop 2b composed of In order to rotationally drive the aperture / transmittance diaphragm 2b,
It is assumed that a rotary drive mechanism 2a controlled by the aperture drive circuit 15 is provided.

As another example of the light amount control means (transmittance control means) used together with the aperture stop 2, a transmittance stop 2c shown in FIG. 6 is used. The transmittance stop 2c includes a liquid crystal panel 2d having a variable exposure multiple (density). The liquid crystal transmittance control circuit 15a in the aperture drive circuit 15 controls the exposure multiple to control the amount of incident light regardless of the aperture area. It is possible to do.

As a means for controlling the amount of incident light irrespective of the aperture area, a well-known electronic shutter for controlling the charge storage time of the CCD is also used. For example, F2.8
In the case where the aperture stop 2 capable of switching between F1 and F4 is provided, as shown in FIG. 7, the light amount is controlled by setting the shutter speed to be faster than 1/60 second at a brightness of EV10 or more.

It is also possible to combine the above-mentioned electronic shutter with light amount control means for controlling the amount of incident light regardless of the opening area. In that case, as shown in FIG.
F5.6 equivalent to F11 equivalent are controlled by the diaphragm,
What is necessary is just to perform the light quantity control further at the shutter speed.

As a comparative example, a mechanism similar to that of the aperture stop 2 in FIG. 4 was used, and the transmittance was not controlled.
An aperture stop 2 'having apertures of 4, F5.6, F8, and F11 is also prepared, and comparative data obtained when light amount control is performed using only the aperture stop is collected and compared.

<Evaluation of Image Quality> With respect to the above Examples and Comparative Examples, images of each example were relatively evaluated by 10 evaluators.

The evaluation method in this case is as follows.
An image obtained by placing the resolution test chart m places ahead was output to a printer having a sufficient resolution, and the resolution, sharpness, and sharpness were evaluated on a three-point scale.

○ is good, Δ is slightly inferior, × is inferior,
This indicates that the evaluation has been made, ○ = + 1 point, Δ = 0
The evaluation point A was calculated based on the points, x = -1 points. (1) When the aperture value at the time of the minimum aperture is defined: The relationship between the aperture value and the evaluation point A in this case is as shown in Table 2 below.

[0099]

[Table 2]

As is apparent from Table 2, when the pixel pitch of the CCD is 7.0 μm or less, and when the aperture value at the time of the minimum aperture is set to less than 5.6, the aperture is used to limit the light amount. Also in the case, the MT of the imaging optical system due to the effect of diffraction
A decrease in the resolution and contrast of the image due to the deterioration of the F characteristic can be minimized, and the image quality is not impaired.

Further, when the pixel pitch of the CCD was 5.0 μm or less, the effect of suppressing such a decrease in resolution and contrast was more remarkably recognized. As a comparative example, when the pixel pitch of the CCD is equal to or less than 7.0 μm and the aperture value at the time of the minimum aperture is set to 5.6 or more, the resolution and contrast are clearly reduced, and the image quality is impaired. Was confirmed.

When the pixel pitch of the CCD was 7.0 μm or more, the effect of improving the image quality as described above was not seen because the resolution and the contrast were hardly reduced by diffraction.

(2) When high-frequency components are emphasized according to the aperture value at the time of the minimum aperture: The relationship between the aperture value and the evaluation point A in this case is as shown in Table 3 below.

[0104]

[Table 3]

As is apparent from Table 3, when the pixel pitch of the CCD is 7.0 μm or less, the high frequency component of the image signal is emphasized even when the aperture value at the minimum aperture is set to 5.6 or more. In addition, the reduction in resolution and contrast due to the influence of diffraction can be minimized, and the image quality is not impaired.

When the pixel pitch of the CCD was 5.0 μm or less, the effect of suppressing such a decrease in resolution and contrast was more remarkably recognized. Also, CC
When the pixel pitch of D is equal to or less than 7.0 μm, unless the aperture value at the minimum aperture is set to 5.6 or more and the high frequency component of the image signal is emphasized, the resolution and the contrast are lowered as is apparent from Table 2. Is seen and the image quality is impaired.

When the pixel pitch of the CCD is 7.0 μm or more, the effect of improving the image quality as described above was not observed because the resolution and the contrast were hardly reduced by the diffraction.

(3) The aperture stop value at the time of the minimum stop is defined.
When transmittance control is used together: The relationship between the aperture value and the evaluation point A in this case is as shown in Table 4 below.

[0109]

[Table 4]

As is clear from Table 4, when the pixel pitch of the CCD is 7.0 μm or less, the aperture value at the time of the minimum aperture is set to less than 5.6, and the light amount control by the transmittance control is also used. Thus, a decrease in resolution and contrast due to the influence of diffraction can be minimized, and the image quality is not impaired.

Further, when the pixel pitch of the CCD was 5.0 μm or less, the effect of suppressing such a decrease in resolution and contrast was more remarkably recognized. Also, CC
If the actual aperture value at the time of the minimum aperture is set to 5.6 or more when the pixel pitch of D is 7.0 μm or less, as can be seen from Table 2, the resolution and contrast are reduced, and the image quality is reduced. It was confirmed that it was damaged.

When the pixel pitch of the CCD is 7.0 μm or more, the effect of improving the image quality as described above was not observed because the resolution and the contrast were hardly reduced by the diffraction.

(4) When the aperture stop at the minimum stop and the transmittance control are used together: The relationship between the aperture value and the evaluation point A in this case is as shown in Table 5 below.

[0114]

[Table 5]

As is apparent from Table 5, when the pixel pitch of the CCD is 7.0 μm or less, the transmittance control is performed when the light amount is further controlled using the aperture value of 5.6 or more at the minimum aperture. By using the light amount control by the aperture, the resolution by the influence of diffraction can be improved compared to the case of the stop with the aperture area alone.
A decrease in contrast can be suppressed, and the image quality is not impaired. For example, F8 equivalent in this case is realized by using both F5.6 and light amount control, so that the influence of diffraction is smaller than in the case where only the aperture is used for the aperture.

Further, when the pixel pitch of the CCD was 5.0 μm or less, the effect of suppressing such a decrease in resolution and contrast was more remarkably recognized. Also, CC
When the pixel pitch of D is equal to or greater than 7.0 μm, the effect of improving the image quality as described above was not observed because the resolution and the contrast were hardly reduced by diffraction.

(5) In the case where the transmittance is controlled irrespective of the opening area: The relationship between the aperture value and the evaluation point A in this case is as shown in Table 6 below.

[0118]

[Table 6]

As is clear from Table 6, when the pixel pitch of the CCD is 7.0 μm or less, the aperture value at the time of the minimum aperture is less than 4 (in this example, as shown in FIG. 5, the maximum aperture F2 .8), and using the light amount control by the transmittance control, the reduction of the resolution and the contrast due to the influence of diffraction can be suppressed to the minimum.
Does not impair image quality.

Further, when the pixel pitch of the CCD was 5.0 μm or less, the effect of suppressing such a decrease in resolution and contrast was more remarkably recognized. Also, CC
When the actual aperture value at the time of the minimum aperture is set to 5.6 or more when the pixel pitch of D is 7.0 μm or less, as is clear from Table 2, the resolution and contrast are reduced, and the image quality is reduced. It was confirmed that it was damaged.

When the pixel pitch of the CCD is 7.0 μm or more, the effect of improving the image quality as described above was not observed because the resolution and the contrast were hardly reduced by the diffraction.

It should be noted that the ones described in the above embodiments and examples can be used for all cameras (electronic still cameras, digital video cameras, etc.) using a solid-state image sensor as an image receiving means. It is particularly suitable for an electronic still camera in that high image quality is emphasized and an aperture is used.

[0123]

As described above in detail with the embodiments and examples, according to each invention described in this specification, the following effects can be obtained.

(1) In the first aspect, when the pixel pitch of the solid-state image pickup device is equal to or less than 7.0 μm, the aperture value at the time of the minimum aperture of the aperture means is set to less than 5.6, so that the light amount is limited. Therefore, even when an aperture is used, the reduction in resolution and contrast due to the effect of diffraction can be minimized.
It is possible to realize a camera using a solid-state imaging device that does not impair image quality as an image receiving unit.

(2) In the second invention, when the pixel pitch of the solid-state imaging device is 7.0 μm or less, the effect of diffraction is corrected by the diffraction effect correction means. In the case of using, the reduction of resolution and contrast due to the influence of diffraction can be minimized.
It is possible to realize a camera using a solid-state imaging device that does not impair image quality as an image receiving unit.

(3) In the third aspect of the present invention, when the pixel pitch of the solid-state imaging device is 7.0 μm or less, the filter means is used to limit the light quantity. The reduction can be minimized, and a camera using a solid-state imaging device that does not impair image quality as an image receiving unit can be realized.

(4) In the fourth aspect, when the pixel pitch of the solid-state imaging device is 7.0 μm or less, and when the aperture value of the minimum aperture of the aperture means is 5.6 or more, the image signal As a result of the process of emphasizing high frequency components, even when an aperture of F5.6 or more is used to limit the amount of light, it is possible to minimize the reduction in resolution and contrast due to attenuation of high frequency components due to diffraction. It is possible to realize a camera that uses a solid-state image sensor that does not impair image quality as an image receiving unit. As a result, even when an aperture is used to limit the amount of light, a decrease in resolution and contrast due to the influence of diffraction can be suppressed to a minimum, and a camera using a solid-state imaging device that does not impair image quality as a receiving means is realized. it can.

(5) In the fifth aspect, when the pixel pitch of the solid-state imaging device is 7.0 μm or less, the aperture value at the time of the minimum aperture of the first light amount control means is set to less than 5.6, and the aperture area is set. As a result of using the second light quantity control means for controlling the light quantity regardless of the light quantity, even when the light quantity control means is used for restricting the light quantity, the deterioration of the resolution and contrast due to the influence of diffraction is minimized. And a camera using a solid-state imaging device that does not impair image quality as an image receiving unit can be realized.

Further, by using the second light amount control means independent of the aperture area, sufficient resolution and contrast can be obtained even in a bright environment. (6) In the sixth aspect, when the pixel pitch of the solid-state imaging device is equal to or less than 7.0 μm, the incident light amount is further limited in a state where the aperture value of the first light amount control means is set to 5.6 or more. In this case, the second light quantity control means for controlling the light quantity irrespective of the aperture area is used together. As a result, even when the light quantity control means is used for restricting the light quantity, the resolution and the contrast due to the influence of the diffraction are increased. Can be minimized, and a camera using a solid-state imaging device as an image receiving unit that does not impair image quality can be realized.

Further, by using the second light amount control means independent of the aperture area, sufficient resolution and contrast can be obtained even in a bright environment. (7) In each of the above-described inventions, even when the image is captured by the solid-state imaging device having a small pixel pitch, the influence of diffraction can be suppressed by using the filter means for controlling the light amount. In particular, when the aperture value is set to 5.6 or more, N
It is desirable to control the light amount using a D filter.

When a photographed image is printed, deterioration in image quality due to diffraction can be easily observed by human eyes. Therefore, the present invention is particularly effective when applied to a still camera.

[Brief description of the drawings]

FIG. 1 is a functional block diagram illustrating a configuration of a camera that uses a solid-state imaging device used as an image receiving unit according to an embodiment of the present invention.

FIG. 2 is a lens arrangement diagram showing an optical schematic configuration of a camera using an image sensor as a solid-state imaging device used in an embodiment of the present invention.

FIG. 3 is a sectional view of an optical system of the imaging lens according to the embodiment of the present invention.

FIG. 4 is a configuration diagram showing a configuration of an aperture / transmittance stop used in the description of the embodiment of the present invention.

FIG. 5 is a configuration diagram showing the configuration of another example of the aperture / transmittance stop used in the description of the embodiment of the present invention.

FIG. 6 is a configuration diagram of a transmittance stop used in the description of the embodiment of the present invention.

FIG. 7 is a program diagram of an electronic shutter used in the description of the embodiment of the present invention.

FIG. 8 is a program diagram of an electronic shutter used in the description of the embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 lens 2 aperture stop 3 image sensor 4 pre-processing circuit 5 A / D converter 6 signal processing circuit 7 memory controller 8 main microcomputer 9 frame memory 10 image storage memory 11 PC card controller 12 strobe 13 serial port driver 14 sub-microcomputer 15 Aperture drive circuit 16 Focus drive circuit 17 Video amplifier 18 Liquid crystal display unit 19 CCD drive circuit

Claims (17)

[Claims] 1. An imaging lens which forms an optical system for forming an optical image of a subject on an image forming surface, and an image signal is generated by photoelectrically converting the optical image of the subject, and a pixel pitch of 7.0 μm or less. A solid-state imaging device; and aperture means provided with an opening, controlling the area of the opening to control the amount of light incident on the solid-state imaging device, and having a minimum aperture value of less than 5.6. A camera comprising: a solid-state imaging device; 2. A solid-state imaging device having a pixel pitch of 5.0.
2. The camera according to claim 1, wherein the size of the solid-state image sensor is not more than μm. 3. An imaging lens which forms an optical system for forming an optical image of a subject on an image forming surface, and an image signal generated by photoelectrically converting the optical image of the subject, wherein a pixel pitch is 7.0 μm or less. A solid-state image sensor, an aperture provided, aperture means for controlling the amount of light incident on the solid-state image sensor by controlling the area of the aperture, and a diffraction element for correcting the influence of diffraction of light passing through the aperture means. A camera comprising: a solid-state imaging device; 4. The camera according to claim 3, wherein the diffraction effect correction unit is an image processing unit that performs image processing on the image signal. 5. The camera according to claim 4, wherein said image processing means performs image processing for enhancing a high-frequency component of said image signal. 6. The solid-state image sensor has a pixel pitch of 5.
The camera according to claim 5, wherein the size is 0 μm or less. 7. An imaging lens which forms an optical system for forming an optical image of a subject on an image forming surface, and an image signal is generated by photoelectrically converting the optical image of the subject, and a pixel pitch of 7.0 μm or less. A camera comprising: a solid-state imaging device; and a filter unit that controls the amount of light incident on the solid-state imaging device by controlling light transmittance. 8. An aperture is provided, and aperture means for controlling the amount of light incident on the solid-state imaging device by controlling the area of the aperture is provided. The aperture value of the aperture means at the minimum aperture time is 5. 8. The camera according to claim 7, wherein the number is less than 6. 9. An aperture is provided, and aperture means for controlling the amount of light incident on the solid-state imaging device by controlling the area of the aperture is provided, wherein the aperture value of the aperture means is 5.6 or more. 8. The solid-state imaging device according to claim 7, wherein the amount of light incident on the solid-state imaging device is controlled by controlling the transmittance of the filter unit and controlling the opening area of the diaphragm unit. camera. 10. An image pickup lens which forms an optical system for forming an optical image of a subject on an image forming surface, and an opening, wherein an area of the opening is controlled to reduce an amount of light incident on the solid-state image pickup device. A diaphragm means for controlling; a solid-state imaging device having a pixel pitch of 7.0 μm or less for generating an image signal by photoelectrically converting an optical image of the subject; and a signal processing means for processing the image signal. A camera using a solid-state imaging device as an image receiving means, wherein the signal processing means performs processing for enhancing a high frequency component of an image signal when an aperture value of the aperture means is 5.6 or more. 11. The solid-state imaging device according to claim 10, wherein the signal processing unit changes the degree of emphasis of a high-frequency component of the image signal according to an aperture value of the aperture unit. Camera. 12. An imaging lens which forms an optical system for forming an optical image of a subject on an image forming surface, a light amount control unit for controlling an amount of light incident on the image forming surface, and a photoelectric conversion unit for photoelectrically converting the optical image of the subject. A solid-state imaging device having a pixel pitch of 7.0 μm or less, and a signal processing unit for processing the image signal, wherein the light amount control unit controls an opening area to control an incident light amount. And a second light quantity control means for controlling the quantity of incident light regardless of the aperture area. The aperture value of the first light quantity control means at the time of the minimum aperture is set to 5. 6. A camera using a solid-state image sensor as an image receiving means. 13. An image pickup lens which forms an optical system for forming an optical image of a subject on an image forming surface, a light amount control unit for controlling an amount of light incident on the image forming surface, and a photoelectric conversion unit for photoelectrically converting the optical image of the subject. A solid-state imaging device having a pixel pitch of 7.0 μm or less, and a signal processing unit for processing the image signal, wherein the light amount control unit controls an opening area to control an incident light amount. And a second light quantity control means for controlling the amount of incident light regardless of the aperture area. The aperture value of the first light quantity control means is set to 5.6 or more. A camera using a solid-state imaging device as an image receiving means, wherein the light quantity control of the second light quantity control means is used when the incident light quantity is further limited in the state. 14. The solid-state imaging device according to claim 5, wherein a pixel pitch is 5.
14. A camera using the solid-state imaging device according to claim 10 as an image receiving means, wherein the size is 0 μm or less. 15. The apparatus according to claim 12, wherein said second light amount control means is an ND filter.
A camera using the solid-state imaging device according to any one of the above as an image receiving means. 16. A camera according to claim 12, wherein said second light quantity control means is a variable density transmittance control means. . 17. The solid-state imaging device according to claim 12, wherein said second light amount control unit is a shutter speed control unit of a solid-state imaging device. camera.