JP2006080838A - Imaging device - Google Patents

Abstract

In order to realize a thin imaging system, there is a technology for generating an RGB image using a four-lens optical system and combining it to obtain a video signal. However, in the above method, due to the parallax, the RGB image shifts according to the subject distance. An object of the present invention is to prevent image color shift and sharpness degradation during close-up photography.
An imaging optical system for forming an image on an imaging device having a plurality of imaging regions on the same plane, wherein the imaging device has first and second visual fields formed with the same spectral distribution. An output image, and detects close-up imaging based on a change in the interval between the first and second images, and outputs a single image of any of a plurality of imaging regions.
[Selection] Figure 1

Description

  The present invention relates to an imaging apparatus such as a digital still camera and a video movie.

  In a digital camera, an object scene image is exposed to an image sensor such as a CCD or CMOS sensor for a desired time, and an image signal of one screen obtained thereby is converted into a digital signal, and predetermined processing such as YC processing is performed. The image signal of a predetermined format is obtained. A digital image signal representing a captured image is recorded in a semiconductor memory, a tape medium, an HDD, or the like for each image.

  The recorded image signal is read out at any time, alone or continuously, and reproduced as a displayable or printable signal, and displayed on an output device such as a monitor.

  In addition, there is a technique for generating an RGB image using a four-lens optical system and synthesizing these to obtain a video signal. This technique is extremely effective in realizing a thin imaging system.

JP 2002-43555 A

  However, in the method using the above-described trinocular optical system or quadruple optical system, the RGB image shifts according to the subject distance due to the parallax of the optical system. This RGB image misalignment is not preferable because it causes a color misalignment of the output image and a decrease in sharpness.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an imaging apparatus capable of preventing image color shift and sharpness reduction during close-up photography.

  In order to solve the above-described problems and achieve the object, an imaging apparatus according to the present invention forms an image with an imaging element having a plurality of imaging areas on the same plane, and an object image on each of the plurality of imaging areas. A photographing optical system; and image processing means for processing an output signal of the image pickup device, wherein the image pickup device has first and second output images having substantially the same field of view formed with the same spectral distribution. In the process of processing the output signal, when a subject distance is detected based on a change in the interval between the first and second images and the subject detection distance is greater than or equal to a predetermined value that can be determined as close-up photography, a plurality of imaging regions It has the means to output any single image of these.

  According to the present invention, during close-up shooting, switching to image output in a single channel (monochrome mode) can prevent color misregistration and suppress a reduction in resolution.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

<Embodiment 1>
2A and 2B are views showing the appearance of the digital camera according to Embodiment 1 of the present invention, FIG. 2A is a front view of the camera, and FIG. 2B is a rear view of the camera.

  In FIG. 2, 201 is a card-type camera body, 202 is a liquid crystal monitor for displaying a captured image, 203 is a switch for the user to set the camera state, 204 is a grip unit for the user to hold the camera, Reference numeral 205 denotes a release button.

  Reference numeral 206 denotes an imaging system, which has a structure shown by a sectional view 207. The imaging system 207 includes a protective glass 209, a diaphragm 208, an optical filter 210, a photographing lens 102, and an imaging element 103.

  Here, the basic elements of the photographic optical system are the photographic lens 102, the diaphragm 208, and the solid-state image sensor 103. The imaging system 207 separates the green (G) image signal, the red (R) image signal, and the blue (B) image signal. Four optical systems for obtaining the above are provided.

  The object distance assumed in this system is several meters, which is very large compared to the optical path length of the imaging system. Therefore, if the incident surface is aplanatic with respect to the assumed object distance, the incident surface is a concave surface with a very small curvature. Here, the plane is replaced. The photographic lens 102 has four lens portions 102a, 102b, 102c, and 102d, each of which is constituted by a ring-shaped spherical surface. On this lens part 102a, 102b, 102c, 102d, the infrared cut filter which gave the low transmittance | permeability about the wavelength range of 670 nm or more is formed.

  Each of the four lens portions 102a, 102b, 102c, and 102d is an imaging system, and as will be described later, the lens portions 012a and 102d are for a green (G) image signal, and the lens portion 102b is a red (R) image signal. The lens portion 102c is for blue (B) image signals. Further, the focal lengths at the respective representative wavelengths of RGB are all 1.45 mm.

Next, the diaphragm 208 has four circular openings 208a, 208b, 208c, 208d. The object light incident on the light incident surface of the photographing lens 102 from each of these is emitted from the four lens portions 102 a, 102 b, 102 c, and 102 d to form four object images on the imaging surface of the solid-state image sensor 103. The diaphragm 208, the light incident surface, and the imaging surface of the solid-state imaging device 103 are arranged in parallel. The diaphragm 208 and the four lens portions 102a, 102b, 102c, and 102d are set in a positional relationship that satisfies the condition of Zinken-Sommer, that is, a positional relationship that simultaneously removes coma and astigmatism.

  The optical filters 210a and 210d have a spectral transmittance characteristic that mainly transmits green as indicated by G in FIG. 3, the optical filter 210b has a spectral transmittance characteristic that mainly transmits blue, indicated by B, and The optical filter 210c has a spectral transmittance characteristic indicated by R, which mainly transmits red. That is, these are primary color filters. As a product of the characteristics of the infrared cut filters formed on the lens portions 102a, 102b, 102c, and 102d, the object images formed on the image circle are respectively formed of a green light component, a green light component, and a red light component. Become.

  If substantially the same focal length is set for each wavelength of the representative wavelength of each spectral distribution in each imaging system, a color image in which chromatic aberration is corrected can be obtained by combining these image signals. Ordinarily, achromatism for removing chromatic aberration requires a combination of at least two lenses having different dispersions. On the other hand, there is a cost reduction effect due to the fact that each imaging system has a single structure. Further, the effect of thinning the imaging system is increased.

  On the other hand, optical filters are also formed on the four imaging regions 103a, 103b, 103c, and 103d of the solid-state imaging device 103. The spectral transmittance characteristics of the imaging regions 103a and 103d are indicated by G in FIG. 3, the spectral transmittance characteristic of the imaging region 103b is indicated by B in FIG. 3, and the spectral transmittance characteristics of the imaging region 103c are shown in FIG. This is indicated by R in FIG. That is, the imaging regions 103a and 103d are sensitive to green light (G), the imaging region 103b is sensitive to blue light (B), and the imaging region 820c is sensitive to red light (R).

  Since the received light spectrum distribution of each imaging region is given as the product of the spectral transmittance of the pupil and the imaging region, the combination of the imaging system pupil and the imaging region is almost selected by the wavelength region even if there are overlapping image circles. .

  Furthermore, a microlens is formed for each light receiving portion of each pixel on the imaging regions 103a, 103b, 103c, and 103d. The microlens is arranged eccentrically with respect to the light receiving portion of the solid-state imaging device 103, and the amount of eccentricity is set to be zero at the center of each imaging region 103a, 103b, 103c, 103d and to increase toward the periphery. . The eccentric direction is the direction of the line segment connecting the center point of each imaging region 103a, 103b, 103c, 103d and each light receiving unit.

  In addition to the method for selectively assigning pupils to each imaging region using the wavelength range described above, the method for selectively assigning pupils to each imaging region using a microlens is also applied. The object light that has passed through the aperture opening 208a is photoelectrically converted in the imaging area 103a, the object light that has passed through the aperture opening 208b is photoelectrically converted in the imaging area 103b, and the object light that has passed through the aperture opening 208c is captured in the imaging area. The object light that has undergone photoelectric conversion at 103c and has passed through the aperture 208d of the diaphragm is photoelectrically converted by the imaging region 103d. Therefore, the imaging areas 103a and 103d output a G image signal, the imaging area 103b outputs a B image signal, and the imaging area 103c outputs an R image signal.

  In an image processing system (not shown), a plurality of imaging regions of the solid-state imaging device 103 form color images based on selective photoelectric conversion outputs obtained from one of a plurality of object images. At this time, distortion of each imaging system is corrected in calculation, and signal processing for forming a color image is performed on the basis of the G image signal including the peak wavelength 555 nm of the relative visibility. Since the G object image is formed in the two imaging regions 103a and 103d, the number of pixels is twice that of the R image signal and the B image signal, and a particularly high-definition image can be obtained in a wavelength region with high visibility. Can be done. At this time, by shifting the object images on the imaging regions 103a and 103d of the solid-state imaging device by ½ pixel in the vertical and horizontal directions, it is possible to use a method of pixel shifting that increases the resolution with a small number of pixels.

  Here, in comparison with an imaging system using a single photographic lens, when the pixel pitch of the solid-state imaging device is fixed, a Bayer in which an RGB color filter is formed on a solid-state imaging device with 2 × 2 pixels as a set. Compared to the arrangement method, this method has an object image size of 1 / √4. As a result, the focal length of the photographic lens is reduced to approximately 1 / √4 = 1/2. Therefore, it is extremely advantageous for making the camera thinner.

  Next, a schematic configuration of the signal processing system will be described.

  FIG. 1 is a block diagram of a signal processing system of the present invention. This camera is a system using a solid-state image sensor 103 such as a CCD or CMOS sensor, and obtains an image signal that can form a moving image or a still image by driving the solid-state image sensor 103 continuously or once. Here, the solid-state imaging device 103 is a type of imaging device that converts exposed light into an electrical signal for each pixel, accumulates charges according to the amount of light, and reads the charges.

  In the drawings, only the portions directly related to the present invention are shown, and the portions not directly related to the present invention are not shown and described.

  As shown in FIG. 1, the camera system includes an imaging lens 102, an imaging element 103, an A / D converter 104, an RGB image formation processing circuit 107, and an output of a single area among a plurality of imaging areas. A single area image forming processing circuit for forming an image from the signal, a YC processing circuit 110, an output signal switching circuit for switching an output signal of the RGB image forming processing circuit and an output signal of the single area image forming processing circuit, A subject distance detection circuit 109 for detecting the distance of the subject.

  The light beam 101 from the object is imaged on the imaging surface of the solid-state image sensor 103 through the diaphragm 208 and the photographing lens 102, and the subject image is exposed to the solid-state image sensor 103. As described above, an imaging device such as a CCD or CMOS sensor is effectively applied to the solid-state imaging device 103, and an image signal representing a continuous moving image by controlling the exposure time and the exposure interval of the solid-state imaging device 103, Alternatively, an image signal representing a still image by one exposure can be obtained.

  As described above, the imaging device 103 is an imaging device having, for example, 800 pixels in the long side direction and 600 pixels in the short side direction for each imaging region, and has a total of 19.2 million pixels. Optical filters of the three primary colors of red (R), green (G), and blue (B) are arranged for each predetermined region.

  Image signals read from the solid-state image sensor 103 are supplied to the image processing systems 106 and 107 via the A / D converter 104, respectively. The A / D converter 104 is a signal conversion circuit that converts and outputs, for example, a 10-bit digital signal according to the amplitude of the signal of each exposed pixel, and subsequent image signal processing is realized by digital processing. Is done.

  The RGB image formation processing circuit 107 is a signal processing circuit that obtains an image signal in a desired format from R, G, and B digital signals. Together with the YC processing circuit 110, the RGB image formation processing circuit 107 converts the R, G, and B color signals into luminance signals. Y and YC signals represented by color difference signals (R−Y) and (B−Y) are converted.

  The RGB image formation processing circuit 107 is a signal processing circuit that processes an image signal of 800 × 600 × 4 pixels received from the solid-state imaging device 103 via the A / D converter 104, and includes a white balance circuit, a gamma correction circuit, It has an interpolation calculation circuit for increasing the resolution by interpolation calculation.

  The YC processing circuit 110 is a signal processing circuit that generates a luminance signal Y and color difference signals RY and BY. A high-frequency luminance signal generation circuit that generates a high-frequency luminance signal YH, a low-frequency luminance signal generation circuit that generates a low-frequency luminance signal YL, and a color difference signal generation circuit that generates color difference signals RY and BY. Yes. The luminance signal Y is formed by combining the high frequency luminance signal YH and the low frequency luminance signal YL.

  A recording / reproducing circuit (not shown) has a processing system for outputting an image signal to the memory and outputting the image signal to the liquid crystal monitor 202, and performs a process for writing and reading the image signal to and from the memory. And a reproduction processing circuit for reproducing an image signal read from the memory and forming an output signal to a monitor or the like. More specifically, the recording processing circuit includes a compression / expansion circuit that compresses YC signals representing still images and moving images in a predetermined compression format, and expands the compressed data when it is read out. The compression / decompression circuit has a frame memory or the like for signal processing. The YC signal from the image processing circuit is stored in the frame memory for each frame, and is read and compressed and encoded for each of a plurality of blocks. The compression coding is performed by, for example, performing two-dimensional orthogonal transformation, normalization, and Huffman coding on the image signal for each block.

  The reproduction processing circuit is a circuit that performs matrix conversion of the luminance signal Y and the color difference signals RY and BY, for example, into RGB signals. The signal converted by the reproduction processing circuit is output to the liquid crystal monitor 202, and a visible image is displayed and reproduced.

  A control system (not shown) includes a control circuit for each part that controls the imaging system, the image processing system, and the recording / reproducing system in response to an external operation, detects the depression of the release button 205, and drives the imaging device 103. It controls the operation of the RGB image processing circuit 106, the operation of the single area image forming circuit 107, the control of the switching circuit 108, the compression processing of the recording processing circuit, and the like.

  The processing in the RGB image processing circuit 107 is as follows.

  That is, with respect to the RGB signal output for each of the R, G, and B regions via the A / D converter 104, first, a predetermined white balance adjustment is performed by the white balance circuit in the RGB image processing circuit, Further, predetermined gamma correction is performed by a gamma correction circuit. An interpolation operation circuit in the RGB image processing circuit 107 generates an image signal having a resolution of 1200 × 1600 for each RGB by performing interpolation processing and distortion correction on the image signal of the solid-state imaging device 103, and the subsequent high-frequency luminance signal This is supplied to a generation circuit, a low luminance signal generation circuit, and a color difference signal generation circuit. Reference numeral 106 denotes a single area image forming circuit that forms an image based on an output signal of one of a plurality of image pickup areas. A white balance circuit, a gamma correction circuit, and a high luminance signal generation according to the RGB processing circuit. And a processing circuit such as a circuit, a low-frequency luminance signal generation circuit, and a color difference signal generation circuit.

  Here, as shown in FIG. 4, when close-up shooting is performed using the RGB image processing circuit 107, the images of the respective areas do not match as shown in FIG. 4 (401), and the resolution and sharpness are lowered. Will occur. Therefore, when a certain amount of image shift occurs, it is possible to prevent a decrease in resolution by forming an image based on one output signal of the plurality of imaging regions (402).

  FIG. 5 is a diagram for explaining detection area setting of an image sensor image used for detecting image shift (subject distance).

  In FIG. 5, reference numerals 501 a, 501 b, 501 c, and 501 d denote four imaging regions of the solid-state imaging device 103. Here, for the sake of explanation, each of the imaging areas 501a, 501b, 501c, and 501d is configured by an array of 8 × 6 areas. The imaging areas 501a and 501d output G image signals, the imaging area 501b outputs B image signals, and 501c outputs R image signals. Since both the imaging areas 501a and 501d output a G image, the line segment L502 is a line segment connecting the optical centers 503 and 504 of the imaging areas 501a and 501d, and the imaging area 501a located below the line segment L502. , 501d pixel region signals have similar shapes, and by taking these correlations, it is possible to detect an image shift between the imaging regions 501a and 501d.

  A relative change amount between a pair of signals having the same spectral distribution in such color characteristics can be detected using a known method using a correlation calculation.

  FIG. 6 shows a method for detecting image shifts in the imaging regions 501a and 501d. The sensors 605a and 605b correspond to a configuration in which image regions located below the line segment L502 in FIG. 5 are arranged. When the subject distance is A, the outputs of the sensors 605a and 605b match as shown in FIG. However, when the subject distances are B and C, the sensor output causes an image shift as shown in FIG. By detecting this deviation amount m, the subject distance can be detected.

  Next, the operation of this camera will be described.

  First, when the main switch 211 is turned on, a power supply voltage is supplied to each part, and an operation is enabled.

  Subsequently, it is determined whether an image signal can be recorded in the memory. The remaining capacity and the number of images that can be taken at this time are displayed on the liquid crystal monitor 202.

  Looking at the display, if the photographer can shoot, the camera is pointed at the subject and the release button 205 is pressed. When the release button 205 is pressed, the exposure time is calculated and the distance calculation circuit 109 calculates the subject distance. If the detected object distance is equal to or smaller than the predetermined value, it is determined that the close-up shooting is performed, the close-up shooting mode (business card shooting mode) switching is displayed on the liquid crystal monitor, and the output signal is switched with the switch 108, and a single area is displayed. The image forming circuit 106 forms an image of only a single area and outputs a monochrome image.

  The switch 203 is a switch for switching to the close-up shooting mode (business card shooting mode), and forcibly switches to the above-described close-up shooting mode. Alternatively, the mode is forcibly switched to the normal mode to the close-up mode (business card mode).

<Embodiment 2>
FIG. 10 shows the screen division of the arithmetic circuit for obtaining the exposure evaluation value of the entire image. Of these divisions, straight lines connecting the optical center positions of G1 and G2 as shown in FIG. A signal corresponding to the first embodiment can be obtained by using the signal of the divided area located above. In this case, detection is performed by inputting G1 and G2 to the detection unit in time series.

  Next, the operation of this camera will be described.

  First, when the main switch 211 is turned on, a power supply voltage is supplied to each part, and an operation is enabled.

  Subsequently, it is determined whether an image signal can be recorded in the memory. The remaining capacity and the number of images that can be taken at this time are displayed on the liquid crystal monitor 202.

  Looking at the display, if the photographer can shoot, the camera is pointed at the subject and the release button is pressed. When the release button is pressed, the exposure time is calculated and the subject distance is calculated by the photometric processing / ranging processing circuit 1101. When the detected subject distance is less than or equal to the predetermined value, it is determined that the close-up shooting is performed, the close-up shooting mode (business card shooting mode) switching is displayed on the liquid crystal monitor, and an image is formed with an image of only a single area. Monochrome image output is performed.

  The switch 203 is a switch for switching to the close-up shooting mode (business card shooting mode), and forcibly switches to the above-described close-up shooting mode. Alternatively, the mode is forcibly switched to the normal mode to the close-up mode (business card mode).

<Embodiment 3>
FIG. 9 shows an example of a well-known distance measuring sensor. Such an external sensor, for example, an active side distance sensor that detects a distance by projecting ultrasonic waves or LED light onto a subject is used. A method of detecting the subject distance and switching to the close-up shooting mode (business card shooting mode) is also conceivable. The basic configuration of the system in this case is the same as that shown in FIG.

  Here, the relative positional relationship of the light flux that has passed through the imaging lens changes according to the distance of the subject, and is reflected in the sensor output. The sensor unit 901 includes sensor rows 902a and 902b. Two images of light beams that have passed through different pupil regions are formed on the light receiving surfaces of the sensor rows 902a and 902b. Accumulation and transfer of charges according to the light quantity distribution are performed. A photoelectric conversion signal based on the electric charge accumulated in time series by the signal from the sensor driving device 903 is converted into a digital signal by the A / D converter 904, and the object distance calculation means 905 detects the object distance. .

It is a block diagram for demonstrating this invention. It is a figure of the digital camera for demonstrating this invention. It is a figure showing the spectral transmittance characteristic of an optical filter. It is a figure showing the image shift by parallax. It is a figure showing the direction of the image shift by parallax. It is a figure showing the image shift by the parallax according to a to-be-photographed object distance. It is a figure which shows the sensor output at the time of focusing. It is a figure which shows the sensor output at the time of a non-focusing. It is a block diagram of a phase difference type distance measuring sensor. It is a figure showing the detection frame setting of the exposure amount detection unit for demonstrating this invention. It is a block diagram for demonstrating this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Light beam 102 Imaging lens 103 Image pick-up element 104 A / D converter 107 RGB image formation processing circuit 108 Output signal switching circuit 109 Subject distance detection circuit 110 YC processing circuit 201 Camera main body 202 Liquid crystal monitor 203 Switches 204 Grip part 205 Release button 206 Imaging system 207 Imaging system 208 Aperture 209 Protective glass 210 Optical filter

Claims (5)

A plurality of apertures for capturing subject images from different positions and a plurality of imaging means for separately receiving external light captured from the plurality of apertures and extracting a predetermined color component for each external light received separately And image processing means for processing the output signal of the imaging means,
The image processing means includes a composite video forming means for forming a composite video based on output signals of the plurality of imaging means, and a single video formation for forming a video based on one output signal of the plurality of imaging means. An image pickup apparatus having a function of switching between an output image of a composite video forming unit and an output image of a single video forming unit as an output image.   A subject distance detecting unit that detects a distance to the subject image, and having a function of switching between an output image of the composite video forming unit and an output image of the single video forming unit according to the output of the subject distance detecting unit; The imaging apparatus according to claim 1, wherein:   3. The imaging according to claim 2, wherein the subject distance detection unit detects the subject distance by comparing video signals from a plurality of imaging units that have extracted the same color component of the plurality of imaging units. apparatus.   An exposure control means for controlling the exposure amount of the subject and an exposure amount detection means for detecting the exposure amount, wherein the subject distance detection means and the exposure amount detection means share the same detection means. Item 4. The imaging device according to Item 3.   And a function of switching between an output image of the composite video forming unit and an output image of the single video forming unit according to a state of the close-up shooting instruction unit. Item 2. The imaging device according to Item 1.

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