JPH10164603A - Image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve focus precision using a high frequency by detecting the frequency higher than the effective case of optical low-pass filter(LPF), canceling the function of this optical LPF before the focusing operation and switching a 2nd detector. SOLUTION: The spatial frequency component of an image is inputted to an imaging device 2 after the spatial frequency component higher than a fixed level is removed through an optical LPF 4. A converted video signal is sent to a 1st detector 9 at the time of a moving image mode by a signal controller 8, the high frequency of about 4MHz band is extracted by a band-pass filter and sent to a lens controller 11 and while using the high frequency component from the 1st detector 9 and the information of lens position detector 12, a lens group 1 is controlled by a motor 13 and focused. In the case of high resolution mode, the optical LPF on the rotation side is rotated at a prescribed angle by an optical LPF rotating mechanism 4, and the high frequency component of spatial frequency is prevented from being attenuated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an imaging device such as a video camera.

[0002]

2. Description of the Related Art In recent years, video cameras have been widely used as image input devices for computers. In particular, a system in which a video camera and a computer (for example, a personal computer or a workstation) are combined is known.
It is being used for DTP or for electronic mail of images and video conference systems.

[0003] Among them, image input devices have recently been developed.
In particular, high-resolution ones that are conscious of HDTV have been developed,
They are used to edit text and images, and to exchange information with high-quality images.

However, the number of pixels of an image sensor of many video cameras at present is about 250,000 to 400,000 pixels, and it is difficult to obtain high-quality image.
Can not respond. Also, for special applications,
Although some high-resolution video cameras have been commercialized, CCDs (imaging devices) are very expensive, which has been a major obstacle to widespread use as general consumer equipment.

However, in recent years, CCDs having about 400,000 pixels
By using a parallel plate glass in the lens system and increasing the optical information incident on the CCD by shifting the optical path, a system that achieves high resolution although it is a still image is a high image quality by shifting the pixel of the CCD It is. As a result, high-quality input devices compatible with HDTV are becoming cheaper.

As described above, since high-resolution shooting can only perform still image shooting as described above, video cameras capable of switching to shoot moving images at a conventional resolution have been commercialized.

From the above background, a conventional video camera having a moving image mode and a high-resolution mode has been configured as shown in FIG. FIG. 3 is a block diagram showing a configuration of a conventional video camera having a moving image mode and a high resolution mode. In the figure, reference numeral 301 denotes a lens group which guides an optical image from a subject to a CCD 302 as an image sensor. 302 is a CCD for converting optical image information into an electric signal, 303 is a parallel plate glass device, 304 is an optical low-pass filter on the rotating side, 305
Is a rotation mechanism for rotating the rotation-side optical low-pass filter 304, and in the center thereof, the rotation-side optical low-pass filter 304 is rotatable within a predetermined angle range around the optical axis (in the figure, c direction). Reference numeral 306 denotes a fixed-side optical low-pass filter.

Reference numeral 307 denotes a signal processing device which receives the input CCD 302
A (analog) / D for output signal (analog signal)
(Digital) conversion, convert to digital signal, generate 3 lines of signal using 1H delay line, then generate RGB (red, green, blue) color signals by matrix processing and time division multiplex After that, white balance processing and gamma correction processing are performed, and RY, BY, and Y color signals and luminance signals are generated by color difference matrix processing. For the luminance signal Y, aperture correction in the horizontal and vertical directions is performed, and a video signal is output. 308
Is a detector for detecting a signal necessary for focusing, which detects and extracts a high frequency (usually about 4 MHz) from a video signal in accordance with the cutoff characteristics of the optical low-pass filters 304 and 306. 309 is a lens control device,
A lens group 301 is driven by information from the detection device 308 to focus on the hill-climbing method. A microcomputer (not shown) integrates information input from the detection device 308 by integrating only a digital signal corresponding to a measurement zone. Computer). In this microcomputer, the integrated value is added for one field, and by referring to the aperture information and the like, a motor 311 described later is controlled to focus. 310 is the lens group 301
311 is a lens group 3 that detects the position of
It is a motor for driving 01.

In FIG. 3, when an image incident from a lens group 301 is photographed, the spatial frequency component of the image passes through an optical low-pass filter 304 to remove a high-frequency spatial frequency component above a certain level, and the spatial frequency component is transferred to a CCD 302. Is entered. CCD302
The image converted into the electric signal in the above is converted into a video signal in the signal processing device 307. From the converted video signal, a high-frequency component necessary for focusing is detected by a detector 308, and the lens controller 309 controls the lens group 301 by a motor 311 from the signal and information of the lens position detector 310, Focusing is performed by a control procedure as shown in FIG. 9 described later.

Next, the operation principle of the parallel flat glass device 303 will be described with reference to FIG.

FIG. 4A shows a state in which the parallel plate glass 401 of the parallel plate glass device 303 is positioned parallel (within the same plane) to the optical axis main plane, and FIG. 5 is a diagram showing a state where the parallel plate glass 401 is displaced by an angle θ from the state of FIG. 4 (a). 4A and 4B, reference numeral 401 denotes a parallel flat glass having a thickness d in the optical axis direction, 402 denotes an incident light incident on the parallel flat glass 40l, and 403 denotes an outgoing light emitted from the parallel flat glass 40l. .

In general, the shift amount of the optical path due to the parallel plate glass 401 is expressed by the following equation.

Δ = (1− (1 / N) · (cosΦ / cos
Φ ')｝ · d · SINΦ) N: Refractive index of parallel plate glass Φ: Angle between incident light and surface normal (incident angle) Φ': Angle between incident light surface normal inside parallel plate glass When the incident angle Φ is very small, cosΦ = cosΦ ′ SINΦ = Φ. Therefore, it can be expressed by a simple approximation as follows: δ = (1-1 / N) · d · Φ1 δ = (1 −1 / N) · d · Φ2 Φ2 = Φ1 + θ, and the parallel flat glass 40 according to the state of FIG.
When 1 is inclined by the angle θ (the state of FIG. 4B), the optical path change amount Δs is as follows: δs = δ2−δ1 = (1-1 / N) · d · (Φ2−Φ1) = (1-1 / N ) · D · θ.

Next, a pixel arrangement and an example of an aperture of the image sensor 302 will be described with reference to FIG. In FIG. 5A, H indicates a horizontal operation direction, and V indicates a vertical operation direction.

On one of two adjacent horizontal lines in the horizontal scanning direction, a yellow color filter Y and a magenta color filter M are alternately arranged at a pixel interval ph in the horizontal operation line direction, and the other is a cyan color filter. C and green filters G are alternately arranged at pixel intervals of ph. Further, one of the vertical lines adjacent to each other in the vertical scanning direction is provided with a yellow filter Y and a cyan filter C alternately at a pixel interval pv, and the other is provided with a magenta filter M and a green filter G at the pixel interval. pv
Are alternately arranged. Here, when the parallel plate glass 401 is tilted at an angle θ, the image shift amount is, for example, 画素 pixel, that is, (1) · ph and (1/1).
2) If the thickness d of the parallel flat glass plate 401 is set so as to become pv, as shown in FIG. 5 (b), a matrix of 4 times in the horizontal direction and 4 times in the vertical direction can provide 16 times the image information. High resolution can be achieved using the conventional CCD 302.

As described above, in the high resolution mode, CC
By performing the pixel shift of D302, the sampling frequency of the CCD 302 is apparently doubled. Therefore, normally, CCD
The "aliasing noise of high-frequency components" generated by the sampling characteristics of 302 no longer occurs, and the high-frequency removal function of the spatial frequency of the optical low-pass filter used there is no longer necessary. I will.

For this purpose, the optical low-pass filter 304 having the function of canceling the function of the optical low-pass filter only when the mode is switched to the high resolution mode is shown in FIGS.
It was configured like 7.

In FIGS. 6 and 7, reference numeral 304 denotes a rotating optical low-pass filter, and 305, a rotating mechanism for rotating the rotating optical low-pass filter 304. The target low-pass filter 304 is held rotatable (in the drawing, direction c) around the optical axis within a predetermined angle range. Reference numeral 306 denotes a fixed-side optical low-pass filter. The optical low-pass filter 304 on the rotating side has a direction in which a normal ray is decomposed (an extraordinary ray direction) with respect to a horizontal plane.
It is in the state of 5 degrees. In addition, the fixed side optical low-pass filter 306 is in a state where the decomposition direction of the ordinary ray (the extraordinary ray direction) is 0 degree (horizontal) with respect to the horizontal plane.

In the states of FIGS. 6 and 7, both the horizontal component and the vertical component are in a state where the cutoff frequency band of the spatial frequency is limited, and the circuit shown in FIGS. To cancel the function of the filter 304, rotate the entire optical low-pass filter 304 by 45 degrees around the shooting optical axis, and the vertical component will be canceled, preventing attenuation of the high spatial frequency component. It is known that this can be done (Japanese Patent Laid-Open No. 7-2457).
No. 62).

FIG. 8 is a diagram showing a high-frequency component included in the video signal extracted by the detection device 308 and a positional relationship between the focal points.
The lens group 301 is moved in an arbitrary direction to check the increase / decrease of the high frequency component (（in FIG. 8). If the high-frequency component increases, it is determined that the focal point exists in the direction, and if the high-frequency component decreases, it is determined that the focal point exists in the opposite direction, and the lens group 301 is rotated. The high-frequency component becomes maximum at the focal point.

FIG. 9 is a flowchart showing a control procedure for performing the focusing control by the above-mentioned method. In step S901, the motor 311 is moved in an arbitrary direction, and in the next step S902, the increase or decrease of the high frequency component is determined. If the high frequency component has increased, the high frequency component is detected by the detection device 308 in step S904. If the high frequency component has not increased, the motor 311 is reversely rotated in step S903, and then the high frequency component is detected by the detector 308 in step S904. Next, in step S905, an increase or decrease in high frequency is determined. If the high frequency component has increased, the process returns to step S904, where the high frequency component is detected by the detector 308. If the high-frequency component has not increased, the rotational position of the motor 311 is returned to the state one step before to focus, and then the processing operation ends.

FIG. 10 is a flowchart showing an operation control procedure up to photographing in a high resolution mode in a conventional image pickup apparatus. In the figure, the mode is switched to the high-resolution mode in step S1001, focusing is performed in step S1002, the function of the optical low-pass filter 304 is canceled in step S1003, and the parallel flat glass 40 is switched in step S1004.
After moving 1 to perform high-resolution shooting, this processing operation ends. The procedure for focusing in step S1002 is the same as that in the moving image mode described above. After focusing, the function of the optical low-pass filter 304 is canceled, and the pixel of the CCD 302 is shifted by one pixel with respect to the pixel of the CCD 302 by the parallel plate glass 401. , High image quality can be obtained.

[0023]

However, when the image is taken in the high resolution mode, the resolution of the conventional apparatus as described above is approximately doubled. Comes into question.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and has an object to provide a good autofocus function even when shooting in a high resolution mode. An object of the present invention is to provide an imaging device.

[0025]

In order to achieve the above object, an image pickup apparatus according to claim 1 of the present invention comprises a lens unit capable of focus control, and an optical image for refracting an optical image obtained from the lens unit. Refraction means, an optical low-pass filter for removing a high-frequency signal component of an optical image signal obtained from the optical image refraction means, an image sensor for converting an optical image signal into an electric signal, and an image sensor obtained from the image sensor. Signal processing means for performing various kinds of signal processing on the electric signal to generate a luminance signal and a color difference signal, and capturing a plurality of images by changing the normal moving image mode and the optical image refraction means; In an imaging device capable of selecting a high-definition image mode capable of capturing a high-definition image by combining these images, a cut-off frequency region of the optical low-pass filter is changed. Optical low-pass characteristic changing means, and high-frequency detection means for freely changing a detection band for the luminance signal to detect a high-frequency component; and adding the optical low-pass characteristic in the moving image mode and the high-definition mode. The focus control of the lens unit is performed based on high frequency information obtained by changing a cutoff frequency region by a changing unit and further changing a detection band by the high frequency detecting unit.

According to another aspect of the present invention, there is provided an imaging apparatus according to the first aspect of the present invention, wherein the optical image refracting means comprises a light-transmitting flat plate glass as an optical axis main plane. The image sensor is configured to be rotatable on an axis parallel to a vertical direction of the image sensor and rotatable on an axis parallel to a horizontal direction of the image sensor, and the light transmission is performed according to horizontal and vertical pixel sizes of the image sensor. The optical path emitted to the image pickup device is changed by rotating the flat glass by a predetermined amount.

According to a third aspect of the present invention, there is provided an imaging apparatus according to the third aspect of the present invention, wherein the optical low-pass characteristic changing means is fixed vertically to an optical axis. An optical low-pass filter including a first crystal birefringent plate and a second crystal birefringent plate rotatable about an optical axis, and a cut-off characteristic obtained by rotating the second crystal birefringent plate. Is changed.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a block diagram showing a schematic configuration of an imaging device having a moving image mode function and a high resolution mode function according to an embodiment of the present invention. In the figure, reference numeral 1 denotes a light image from a subject (CCD)
A lens group for guiding to 2, a CCD for converting optical image information into an electric signal, and a parallel plate glass device 3, a vertical direction (a direction in the figure) and a horizontal direction (b direction in the figure). And a rotatable parallel flat glass 3a. Reference numeral 4 denotes an optical low-pass filter rotating mechanism. An optical low-pass filter (rotation-side optical low-pass filter) 5 is provided at a central portion in one direction within a predetermined angle around the optical axis (direction c in the figure).
Is held rotatably. Reference numeral 6 denotes a fixed-side optical low-pass filter. In the moving image mode, the rotation-side optical low-pass filter 5 is fixed at a position where high frequency is removed by the optical low-pass filter rotation device 4. In the high-resolution mode, the rotation-side optical low-pass filter 5 is rotated to a position where the high frequency is not removed by the optical low-pass filter rotating device 4.

Reference numeral 7 denotes a signal processing device which converts a signal from the CCD 2 into a video signal. Reference numeral 8 denotes a signal control device that controls the flow of a video signal according to an imaging mode. Reference numeral 9 denotes a first detector for detecting a high frequency component of about 4 MHz in the video signal from the signal processor 7. 10 is a second detection device, a signal processing device
The first detector 9 detects a high-frequency component of about 7 MHz, which is higher than the first detector 9, using the video signal from 7. 11 is a lens control device,
The lens group 1 is controlled and focused by the high frequency component signal output from the detection device 9 or the second detection device 10 and the detection information of the lens position detection device 12. Reference numeral 12 denotes a lens position detection device that detects zoom information and focus lens position information, and 13 denotes a motor for driving the lens group 1.

Next, the operation of the imaging apparatus according to the present embodiment having the above configuration will be described with reference to FIGS.

When focusing in the moving image mode, FIG.
In, the spatial frequency component of the image incident from the lens group 1 passes through the optical low-pass filter 4 to remove a spatial frequency component of a certain high frequency or more, and is input to the CCD 2. The image converted to an electric signal by the CDD 2 is output to the signal processing unit 7
Is converted to a video signal. The converted video signal is sent to the first detection device 9 by the signal control device 8 in the moving image mode. The video signal sent to the first detector 9 is approximately
The high frequency in the 4 MHz band is extracted by a band pass filter and sent to the lens control device 11. This lens control device 11
Using the high frequency components sent from the first detector 9 and the information of the lens position detector 12, the lens group 1 is
Control with 3 to focus.

When focusing in the high resolution mode,
In FIG. 1, an optical low-pass filter rotation mechanism 4 rotates a rotation-side optical low-pass filter 5 by 45 degrees around an imaging optical axis, and a high-frequency component of a spatial frequency in relation to a fixed-side optical low-pass filter 6. To prevent the attenuation of
No. 245762). Therefore, the spatial frequency component of the optical image incident from the lens group 1 is not removed without removing the high frequency component.
Input to CCD2. The optical image converted into an electric signal by the CDD 2 is processed into a video signal by the signal processing unit 7, and the processed video signal is transmitted to the second detection device 10 by the signal control device 8 in the high resolution mode. Sent. From the video signal sent to the second detector 10, the high frequency of about 7 MHz band higher than the first detector 9 is extracted by a band-pass filter and sent to the lens controller 11. This lens control device
11 is a motor 13 based on the high frequency sent from the second detector 10 and the information of the lens position detector 12
To control the focus. Then, when the focus is achieved, the parallel plate glass 3a of the parallel plate glass device 3 is driven to start the pixel shift.

FIG. 2 is a flowchart showing an operation control procedure up to the start of high-resolution shooting in the high-resolution mode. Note that a program for executing this flowchart is stored in storage means such as a ROM (read only memory) (not shown), and is executed by a microcomputer or the like.

The mode is switched to the high resolution mode in step S201 of FIG. 2, and the function of the optical low-pass filter 5 is canceled in step S202. Next, the second detection device 10 is selected in step S203, the focus is set in step S204, and the parallel flat glass 3a is driven in step S205 to execute high-resolution imaging, and then this processing operation is ended.

[0035]

As described above in detail, according to the image pickup apparatus of the present invention, a detection apparatus capable of detecting a frequency in a higher frequency band than when an optical low-pass filter is effective, and the optical apparatus before focusing operation. Since switching means for canceling the function of the low-pass filter and switching to the detection device is provided, it is possible to improve the focus accuracy by using a higher frequency than usual.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of an imaging device according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating an operation control procedure up to a stage where high-resolution imaging is started in the imaging apparatus.

FIG. 3 is a block diagram illustrating a schematic configuration of a conventional imaging device.

FIG. 4 is a schematic view of shifting an optical path by a parallel plate glass in the conventional imaging apparatus.

FIG. 5 is a diagram showing a pixel arrangement and an example of an aperture of an image sensor in the conventional image pickup apparatus.

FIG. 6 is a diagram showing a schematic configuration of an optical low-pass filter rotating mechanism in the conventional imaging apparatus.

FIG. 7 is a diagram showing a schematic configuration of an optical low-pass filter rotation mechanism in the conventional imaging apparatus.

FIG. 8 is a diagram showing a relationship between a focal point and a high frequency in the conventional imaging apparatus.

FIG. 9 is a flowchart showing an operation control procedure at the stage of focusing in the conventional imaging apparatus.

FIG. 10 is a flowchart showing an operation control procedure up to a stage of starting high-resolution imaging in the conventional imaging apparatus.

[Explanation of symbols]

 1 Lens group 2 Image sensor 3 Parallel plate glass device 3a Parallel plate glass 4 Optical low-pass filter 5 Optical low-pass filter rotation driver 6 Fixed-side optical low-pass filter 7 Signal processing device 8 Signal control circuit 9 Detection device 10 High-frequency detection Device 11 Lens control device 12 Lens position detection device 13 Motor 301 Lens group 302 Image sensor 303 Parallel plate glass device 304 Optical low-pass filter 305 Optical low-pass filter rotation drive unit 306 Fixed-side optical low-pass filter 307 Signal processing device 308 Detection Device 309 Lens control device 310 Lens position detector 311 Motor 401 Parallel flat glass 402 Incident light 403 Outgoing light

Claims (3)

[Claims] 1. A lens unit capable of focus control, an optical image refraction unit for refracting an optical image obtained from the lens unit, and a high-frequency signal component of an optical video signal obtained from the optical image refraction unit is removed. An optical low-pass filter, an image sensor that converts an optical image signal into an electric signal, and a signal processing unit that performs various kinds of signal processing on the electric signal obtained from the image sensor to generate a luminance signal and a color difference signal. Which can select a normal moving image mode and a high-definition image mode in which a high-definition image can be captured by capturing a plurality of images by changing the optical image refraction means and combining these images. In the apparatus, an optical low-pass characteristic changing unit that changes a cutoff frequency region of the optical low-pass filter, and a detection band for the luminance signal is freely changed. A high-frequency detection means for detecting high-frequency components is added, a cutoff frequency region is changed by the optical low-pass characteristic changing means in the moving image mode and the high-definition mode, and a detection band is further changed by the high-frequency detection means. An image pickup apparatus characterized in that focus control of the lens unit is performed based on high-frequency information obtained by changing the distance. 2. The optical image refracting means, wherein a light transmitting flat glass is rotatable on an optical axis main plane on an axis parallel to a vertical direction of the image sensor and on an axis parallel to a horizontal direction of the image sensor. The light path emitted to the image sensor is changed by rotating the light transmitting flat glass by a predetermined amount according to the horizontal and vertical pixel sizes of the image sensor. The imaging device according to 1. 3. The optical low-pass characteristic changing means comprises: a first crystal birefringent plate fixed perpendicular to an optical axis and a second crystal birefringent plate rotatable around the optical axis. 2. The imaging device according to claim 1, further comprising a low-pass filter, wherein the cut-off characteristic is changed by rotating the second crystal birefringent plate.