JP2004072181A - Digital camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a digital camera capable of simply and freely adjusting swing and tilt in the case of processing digital image without the need for physically moving a lens and an imaging element. <P>SOLUTION: The digital camera 10 has a central processing unit 22, and the central processing unit 22 applies swing and tilt correction arithmetic operations using a swing and tilt correction coefficient to a digital image signal including 'swing and tilt'. Operating the camera 10 can set the swing and tilt correction coefficient and freely adjust the swing and tilt. Interpolating pixels of each line of the image in response to the swing and tilt correction coefficient performs the swing and tilt correction arithmetic operations to realize the swing and tilt adjustment with a simple configuration. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a digital camera that performs tilted photographing that can be freely adjusted.
[0002]
[Prior art]
Conventionally, a camera has a so-called “tilt” in which, for example, an entire view of a high building is captured in a squeezed and distorted shape. In order to correct such a distorted image when a building is listed in a catalog or the like, it is known to perform tilt correction photography that adjusts the angle between the lens and the image sensor or film surface. The digital camera can also perform tilt correction by signal processing of digital image data.
[0003]
An electronic camera described in Japanese Patent Application Laid-Open No. 2000-013665 operates a bellows to focus, detects a tilt angle and a tilt direction based on a movement amount of the bellows, and performs solid-state imaging according to the tilt angle and the tilt direction. The element support mechanism is operated to move the light receiving surface of the solid-state imaging device. Further, in order to confirm the in-focus position, a part of the image data is enlarged by digital processing. In addition, adjustment is performed by preparing a plurality of image data of different in-focus positions, which are images of the same subject, and synthesizing the plurality of image data.
[0004]
The liquid crystal projector described in Japanese Patent Application Laid-Open No. 06-082751 inputs a tilt correction amount and a correction direction, and a predetermined number of pixels are thinned out for each scanning line according to the correction amount. A blanking period corresponding to each pixel is given, and the number of pixels for each scanning line of the video signal given to the liquid crystal panel is reduced to correct the tilt generated in the projected image.
[0005]
[Problems to be solved by the invention]
In the electronic camera described in the above-mentioned Japanese Patent Application Laid-Open No. 2000-013665, for example, by operating the bellows, an appropriate tilt angle and tilt direction are detected, and the light receiving surface of the solid-state image sensor is tilted to perform tilt shooting. On the other hand, it also aims at electronic tilt correction. However, since this electronic correction electronically processes a plurality of images taken by tilting, it is considered that complicated processing is required, and that a large amount of processing time and memory capacity are required.
[0006]
In the projector described in Japanese Patent Laid-Open No. 06-082751, the tilt amount and tilt direction are input to the apparatus, and digital image processing is performed to perform tilt adjustment. However, in the liquid crystal projector described in this publication, the number of pixels decreases due to the thinning process, and the corrected image data can be used only for display by projection.
[0007]
The present invention eliminates the drawbacks of the prior art and provides a digital camera that can be adjusted easily and freely when processing digital image data without physically moving the lens or image sensor. The purpose is to do.
[0008]
[Means for Solving the Problems]
According to the present invention, a digital camera that captures a subject and generates a first digital image signal representing the subject image corrects the trapezoidal distortion of the subject image by performing a correction on the first digital image signal. Correction means and setting means for setting a coefficient used for tilt correction, wherein the correction means corrects the pixel according to the coefficient for each horizontal line of the screen including the subject image to correct the tilt. And
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of a digital camera according to the present invention will be described in detail with reference to the accompanying drawings. As shown in FIG. 1, the digital camera 10 according to the embodiment corresponds to the tilt correction coefficient input by the operator using the key operation unit 88 with respect to the subject image captured by the solid-state imaging device 14 through the optical lens system 12. A central processing unit (CPU) 22 is a photographing device that performs correction and performs recording on an image data recording medium such as a memory card 30. For the purpose of tilt correction, the central processing unit 22 has, inter alia, a coordinate calculation unit 24, an interpolation calculation unit 26 and a correction coefficient storage unit 28. Note that portions not directly related to understanding the present invention are not shown and redundant description is avoided.
[0010]
In the digital camera 10, the optical lens system 12 is an imaging optical system that forms a subject image on the imaging surface of the solid-state imaging device 14. The solid-state imaging device 14 has a function of photoelectrically converting the subject image into an electric signal 102. In this embodiment, a charge coupled device (CCD) or the like is used. The output 102 is connected to the input of an analog / digital (A / D) conversion circuit 16. The A / D conversion circuit 16 is a signal conversion circuit that performs analog / digital conversion on the electric signal 102. In the following description, each signal is specified by the reference number of the connecting line in which it appears. The converted digital data 104 is input to the input of the signal processing unit 18.
[0011]
The signal processing unit 18 has a signal processing function of an image signal. The digital image signal 104 input from the A / D conversion circuit 16 is subjected to white balance adjustment, gamma processing, and luminance / color difference signal conversion (YC). The digital image signal 106 is stored in the buffer memory 20 for temporary storage. In this embodiment, the buffer memory 20 is a temporary storage device having a storage capacity capable of storing image data 106 for at least two frames. In relation to the present invention, the central processing unit 22 performs tilt correction on the image data stored in the buffer memory 20, and the corrected image data is stored in the buffer memory 20 again.
[0012]
The central processing unit 22 is a control function unit that is connected to the key operation unit 88 and controls and supervises the operation of the entire apparatus according to the key operation of the operator in the key operation unit 88. In particular, the central processing unit 22 performs tilt correction on the digital image signal 108 by the coordinate calculation unit 24, the interpolation calculation unit 26, and the correction coefficient storage unit 28 included therein.
[0013]
The correction coefficient storage unit 28 has a storage function for storing a tilt correction coefficient, and the correction coefficient includes a tilt center axis value and a tilt amount. For example, as shown in FIG. 3, in order to simplify the description, an image 102a of a simple rectangular parallelepiped subject (not shown) includes a tilt in a raster scanning screen 102 composed of a plurality of horizontal scanning lines. When trapezoidal distortion occurs, a straight line perpendicular to the base of the trapezoid is selected as the central axis 110, and this is used as a reference for correction. As shown in FIG. 2, the tilt center axis value 110 is represented by a value γ obtained by normalizing the position of the tilt center axis 110 in the horizontal axis coordinates with the horizontal width of the image 102 being 1. Further, as shown in FIGS. 3 and 4, when the trapezoid is divided into two trapezoids by the tilt central axis 110, the tilt amount is set to 1 which is the longer of the upper or lower trapezoid. Is represented by a value α of the length of the opposite side to The central axis value γ and the tilt amount α are stored in the correction coefficient storage unit 28.
[0014]
The coordinate calculation unit 24 has a function of correcting the coordinates of each pixel of the supplied digital image signal 108 with the above-described correction coefficient and obtaining the corrected coordinates. For example, as shown in FIG. 6, with respect to the position of a certain pixel in the image region represented by the image signal 102, that is, the coordinates (x, y), the corresponding corrected coordinates (X, y) subjected to the tilt correction are With reference to the coordinates (CX, y) on the central axis 110, the tilt amount α is obtained. The x coordinate CX of the tilt center axis 110 at this time is obtained from γ. The coordinate calculation unit 24 performs such coordinate calculation.
[0015]
The interpolation calculation unit 26 has a calculation function for obtaining pixel values corresponding to the corrected coordinates obtained by the coordinate calculation unit 24 from the original digital image signal 108 by pixel interpolation. For example, as shown in FIG. 7, the pixel value of the interpolated coordinates (X, y), that is, the signal level Data, is calculated based on two neighboring pixels ((INT) X, y) and ((INT) X + 1) in the original digital image signal 108. , Y) can be obtained by linear interpolation using the pixel values Data0 and Data1. This interpolation method may be determined in consideration of image quality. This will be described in detail later.
[0016]
In the present embodiment, for example, the tilt center axis value γ and the tilt amount α can be easily set by the operator operating the key operation unit 88 while viewing the display image on the liquid crystal display screen 86. More specifically, the operator displays a straight line segment for calculating the tilt center axis value γ and the tilt amount α on the liquid crystal display screen 86 so as to be superimposed on the image of the subject, and these keys are operated by key operation. By moving the line segment on the liquid crystal display screen 86 as desired, the tilt center axis value γ and the tilt amount α can be set. For this purpose, the digital camera 10 includes a combining unit 82 and a correction image memory 84, which are connected as shown in the figure.
[0017]
At this time, the synthesizer 82 superimposes the digital image signal 802 obtained from the buffer memory 20 and the digital image signal 804 supplied from the correction image memory 84, and supplies the resulting digital image signal 806 to the liquid crystal display screen 86. Signal synthesis function.
[0018]
The correction image memory 84 stores a digital image signal 808 representing two tilt lines 902 and 904, for example, as shown in FIG. Digital image signals 808 representing the tilt lines 902 and 904 are generated by the central processing unit 22 and stored in the correction image memory 84.
[0019]
The liquid crystal display screen 86 is a visible display device that is supplied with a digital image signal 806 from the synthesis unit 82 and displays the image signal 806 as a visible image. The liquid crystal display screen 86 has a viewfinder function that represents an object scene image picked up by the solid-state image sensor 14. However, when the tilt correction operation is performed, the tilt lines 902 and 904 (FIG. 9 and the like) are displayed on the object scene. It also has a function of displaying it superimposed on an image and displaying the internal state of the camera 10. Therefore, the digital image signal 806 normally represents the object scene image 802 read out from the buffer memory 20, but when performing a tilt correction operation, it represents the lines 902 and 904 in the combining unit 82 as will be described later. This is a signal synthesized with the image signal 804.
[0020]
The key operation unit 88 is a manual operation device that inputs various instructions of the operator to the camera 10, and has a function of outputting an operation signal 810 according to the manual operation state of the operator to the central processing unit 22. In particular, the present embodiment includes input and selection switches (not shown) for moving the tilt lines 902 and 904 displayed as shown in FIG.
[0021]
The operation of the digital camera 10 in this embodiment will be described. The operator sets a tilt center axis value γ and a tilt amount α in the camera 10 by, for example, key operation using the key operation unit 88. These are stored in the correction coefficient storage unit 28 in the central processing unit 22. The setting method will be described later in detail.
[0022]
In the camera 10, a subject image is formed on the solid-state image sensor 14 by the optical lens system 12, and the solid-state image sensor 14 photoelectrically converts the subject image to generate an electric signal 102 that is an image signal. The image signal 102 is supplied to the A / D conversion circuit 16 and converted into a corresponding digital signal 104. The digital image signal 104 is supplied to the signal processing unit 18 and subjected to the signal processing described above. The signal-processed digital image signal 106 is temporarily stored in the buffer memory 20.
[0023]
When performing the tilt correction, the central processing unit 22 reads the target digital image signal 108 from the buffer memory 20, and performs a tilt correction on the digital image signal 108 by the coordinate calculation unit 24 and the interpolation calculation unit 26. The coordinate calculation unit 24 and the interpolation calculation unit 26 use the tilt center axis value γ and the tilt amount α stored in the correction coefficient storage unit 28 to perform tilt correction as follows.
[0024]
The coordinate calculation unit 24 first determines the x coordinate of the tilt center axis 110. As shown in FIG. 5, when the number of pixels in one horizontal line is H, the x-coordinate CX = γ × H of the tilt center axis 104 can be obtained. If the number of pixels in the vertical direction of the screen, that is, the number of lines is V, the correction amount αy = (1−α) × (V−y) / V + α at the coordinate y can be obtained. Further, as shown in FIG. 6, using these values, correction coordinates (X, y) corresponding to the coordinates (x, y) of each pixel can be obtained. When the horizontal coordinate x is smaller than X, X = CX−αy × x, otherwise X = CX + αy × x.
[0025]
As shown in FIG. 7, in the interpolation calculation unit 26, for example, the pixel value Data of the interpolation coordinate (X, y) obtained by the coordinate calculation unit 24 is obtained by linear interpolation using two neighboring pixels. In the present embodiment, interpolation coordinates (X) are obtained by using two neighboring pixels, that is, the pixel value Data0 of the coordinates ((INT) X, y) of the digital image signal and the pixel value Data1 of the coordinates ((INT) X + 1, y). , Y) finds the pixel value Data. First, an interpolation coefficient CF1 = X− (INT) X between the pixel values Data0 and Data is obtained. The correction coefficient CF1 represents the decimal part of the coordinate X. Next, an interpolation coefficient CF0 = 1−CF1 between the pixel values Data and Data1 is obtained. Using these interpolation coefficients, the pixel value Data = CF0 × Data0 + CF1 × Data1 of the pixel (X, y) can be obtained by linear interpolation.
[0026]
As described above, in this embodiment, when the tilt center axis value γ and the tilt amount α are set, the value of the correction coordinate X in the coordinates (x, y) of the image 102 is With the x coordinate CX of the central axis 104 as a reference, it is obtained by a correction amount αy that changes for each coordinate in the vertical direction. Further, the pixel value Data corresponding to the correction coordinate X is obtained by interpolation calculation, and is used as a pixel value after correction of the coordinates (x, y). In this way, in an image in which a trapezoidal distortion occurs in the subject, the correction can be performed for each line parallel to the bottom of the trapezoid with an enlargement factor that is variable according to the correction coefficient. This line may basically be a horizontal scan line of the screen.
[0027]
In this embodiment, the operator displays straight line segments for calculating the tilt center axis value γ and the tilt amount α on the liquid crystal display screen 86 so as to overlap the subject image, and these line segments are displayed by key operation. By operating as desired, the tilt center axis value γ and the tilt amount α can be set. In the tilt correction mode, the central processing unit 22 first generates a digital image signal 808 representing the tilt lines 902 and 904 or the center line 912 and the tilt line 914 as shown in FIGS. Stored in the image memory 84. Next, the synthesizer 82 superimposes the digital image signal 802 of the subject supplied from the buffer memory 20 and the digital image signal 804 representing the tilt lines 902 and 904 supplied from the correction image memory 84 on the digital image. A signal 806 is generated. The image signal 806 is supplied to the liquid crystal display screen 86 and displayed as a visible image. The operator operates the key operation unit 88 while viewing the composite image displayed on the liquid crystal display screen 86 to move the tilt lines 902 and 904 and the like on the screen 86.
[0028]
For example, as shown in FIG. 8, when using two tilt lines 902 and 904, the operator operates the key operation unit 88 to move the upper end and the lower end of each tilt line. As shown in FIG. 9, when a picture 910 in the subject image is distorted into a trapezoidal shape including a tilt, first, the upper end 912 of the left tilt line 902 is aligned with the left side 918 of the target picture 910. At this time, the upper end 914 of the right tilt line 904 automatically moves to the same height as the upper end 912 of the tilt line 902. Next, as shown in FIG. 10, the lower end 916 of the tilt line 902 is similarly aligned with the right side 920 of the subject pattern 910. At this time, the lower end 922 of the tilt line 904 is also automatically moved to the same height as the lower end of the tilt line 902. Next, as shown in FIG. 11, the upper end 914 of the tilt line 904 is aligned with the right side 920 of the subject pattern. At this time, the height of the upper end 912 of the tilt line 902 does not change. Next, as shown in FIG. 12, the lower end 922 of the tilt line 904 is aligned with the right side 920 of the subject pattern 910. Also at this time, the height of the lower end 916 of the tilt line 902 does not change. In this way, the correction tilt lines 902 and 904 are superimposed on the image of the subject.
[0029]
At this time, as shown in FIG. 13, if the x coordinate of the left end of the screen 86 is 0, the upper end of the tilt line 902 is represented by a, the lower end is represented by b, the upper end of the tilt line 904 is represented by c, and the lower end is represented by d. The coordinate calculation unit 24 obtains the abscissa x of the center axis 906 and the ratio between the upper base and the lower base from these four points. In these four points, since the ratio from the tilt center axis 906 is constant, when the upper base (c−b) is smaller than the lower base (da), 1: α = (da) :( c −b), and the tilt amount α = (c−b) / (d−a) can be obtained. When the upper base (cb) is larger than the lower base (da), 1: α = (c−b) :( da), and the tilt amount α = (da) / (c -B) can be determined. Further, when the upper base (bc) is smaller than the lower base (ad) from the tilt amount α and the coordinates of the apex, 1: α = (x−a) :( x−b), and the tilt center axis 906 is obtained. The coordinates x = (b−αa) / (1−α) can be obtained. Further, when the upper base (bc) is larger than the lower base (ad), 1: α = (x−b) :( x−a), and the coordinate x = (a−αb) of the tilt center axis 906 is obtained. ) / (1-α). By normalizing the coordinate value x of the tilt center axis 906 with the horizontal width of the screen 86 being 1, it is possible to cope with the case where the number of pixels of the display image and the recording image is different.
[0030]
When tilt correction is performed at the time of photographing, coefficients used for tilt correction, such as a tilt center axis value γ and a tilt amount α, are calculated from the tilt lines 902 and 904 set by operating as described above. Using these coefficients, the coordinate calculation unit 24 obtains correction coordinates of each pixel of the digital image signal, and the interpolation calculation unit 26 obtains pixel values corresponding to the correction coordinates.
[0031]
By the way, as shown in FIG. 14, one tilt center axis 912 and two tilt lines 914a and 914b are displayed on the liquid crystal display screen 86, and the system is configured to perform correction by operating this. May be. In this example, the operator operates the key operation unit 88 to set the tilt amount, and moves the tilt lines 914a and 914b and the tilt center axis 912 to the left and right. When the operator sets the variable r by means of the key operation unit 88, the two tilt lines 914a and 914b are automatically tilted at the same time. As shown in FIG. 15, for example, if the length e of the upper base and the length f of the lower base are given, the two tilt lines 914a and 914b are hatched lines that can be expressed by a ratio of e: f = r: 1. . At this time, when the variable r is smaller than 1, the tilt amount α is r. When the variable r is larger than 1, the tilt amount α is 1 / r. As shown by an arrow 924 in FIG. 16, the tilt center axis 912 moves left and right by key operation to determine its position, and the tilt center axis value α can be obtained from this position. At this time, the two tilt lines 914a and 914b move simultaneously so as to maintain a ratio of a: b = r: 1. As shown in FIG. 17, the tilt lines 914a and 914b move to the left and right by key operations individually. For example, when the left tilt line 914a is moved left and right as indicated by an arrow 926, the tilt center axis 912 and the right tilt line 914b do not move, and the left tilt line 914a does not change the tilt amount α. Move and tilt again. The right tilt line 914b can be moved in the same manner.
[0032]
This embodiment can also be applied to the display of a through image on the liquid crystal display screen 86. In this case, an image of the subject is captured when the through image is updated, and an image representing a tilt line or the like corresponding to the operation state at that time is generated and stored in the buffer memory 20 and the correction image memory 84. The Further, these images are combined by the combining unit 82, and the combined image is supplied to the liquid crystal display screen 86 and displayed as a visible image. These processes are repeated every time the live view display is updated. This embodiment can be similarly applied to the display of a preview image. In this case, if it is not necessary to repeatedly update the preview image, it is not necessary to repeat the above processing as in the case of through image display.
[0033]
The image data that has been corrected by the central processing unit 22 in this manner is stored in the buffer memory 20 again. The image stored in the buffer memory 20 is finally recorded in the memory card 30 in this embodiment in response to the operation of the key operation unit 88 by the operator.
[0034]
【The invention's effect】
As described above, according to the present invention, the digital camera sets a coefficient necessary for the tilt correction, and performs the tilt correction by the digital image processing by correcting the pixel for each line according to the coefficient. This makes it possible to perform tilt shooting that can be freely adjusted.
[0035]
Also, the digital camera according to the present invention displays a visible image by superimposing an image representing a line segment from which this coefficient can be calculated with the image of the subject, and allows the line segment to be moved by key operation. Can be adjusted easily through the visual sense of the person. Since this image superimposition can be applied to a through image display and a preview image display, it can be adjusted in real time.
[Brief description of the drawings]
FIG. 1 is a functional block diagram showing a first embodiment of a digital camera to which the present invention is applied.
FIG. 2 is a diagram showing a tilt center axis when one image is a correction target in the digital camera of the embodiment shown in FIG. 1;
FIG. 3 is a diagram showing a tilt amount when the bottom base of the tilt correction target is longer than the top bottom in the digital camera of the embodiment.
FIG. 4 is a diagram illustrating a tilt amount when the upper base of the tilt correction target is longer than the lower base in the digital camera of the embodiment.
FIG. 5 is a diagram illustrating a correction amount at a coordinate y in the digital camera of the embodiment.
6 is a diagram exemplifying correction coordinates (X, y) corresponding to coordinates (x, y) in the digital camera in the embodiment. FIG.
FIG. 7 is a diagram illustrating pixel interpolation of interpolation coordinates (X, y) in the digital camera in the embodiment.
FIG. 8 is a diagram illustrating two tilt lines when one image is a target for tilt correction in the digital camera of the embodiment.
FIG. 9 is a diagram illustrating a case where the upper end of the left tilt line is superimposed on the tilt correction target in the digital camera of the embodiment.
FIG. 10 is a diagram illustrating a case where the lower end of the left tilt line is superimposed on the tilt correction target in the digital camera of the embodiment.
FIG. 11 is a diagram illustrating a case where the upper end of the right tilt line is superimposed on the tilt correction target in the digital camera of the embodiment.
FIG. 12 is a diagram illustrating a case where the lower end of the right tilt line is superimposed on the tilt correction target in the digital camera of the embodiment.
FIG. 13 is a diagram illustrating the coordinates of the upper and lower ends of two tilt lines in the digital camera of the embodiment.
FIG. 14 is a diagram showing a center line and two tilt lines when one image is a target for tilt correction in the digital camera of the embodiment;
FIG. 15 is a diagram showing a case where the tilt amount is set and two tilt lines are inclined in the digital camera of the embodiment.
FIG. 16 is a diagram showing a case where the center line is moved in the digital camera of the embodiment.
FIG. 17 is a diagram showing a case where the left tilt line is moved in the digital camera of the embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Digital camera 12 Optical lens system 14 Solid-state image sensor 16 A / D conversion circuit 18 Signal processing part 20 Buffer memory 22 Central processing unit 24 Coordinate calculation part 26 Interpolation calculation part 28 Correction coefficient storage part

Claims (5)

In a digital camera that images a subject and generates a first digital image signal representing the subject image, the camera includes:
Correcting means for correcting a tilt of the first digital image signal to correct the trapezoidal distortion of the subject image;
Setting means for setting a coefficient used for the tilt correction,
The digital camera according to claim 1, wherein the correction unit performs the tilt correction by correcting pixels according to the coefficient for each horizontal line of the screen including the subject image. 2. The camera according to claim 1, wherein the coefficient is a ratio of a tilt center axis value representing a horizontal position of the trapezoid tilt center axis perpendicular to the horizontal line and a length of two bases of the trapezoid. Including the amount of tilt represented,
The correction means includes
Coordinate calculation means for calculating correction coordinates by calculating the coordinates of each pixel of the subject image using the tilt center axis value and the tilt amount;
Interpolation operation means for obtaining a pixel value corresponding to the correction coordinates by pixel interpolation. The camera of claim 2, wherein the camera is
Generating means for generating a second digital image signal representing a plurality of line segments;
Combining means for combining the first digital image signal and the second digital image signal to generate a third digital image signal;
Display means for visually displaying an image represented by the third digital image signal,
The setting means includes an operation means for operating a display position on the screen of the plurality of line segments,
The correction means includes correction coefficient calculation means for obtaining the tilt center axis value and the tilt amount from the display positions of the plurality of line segments,
Thus, the coefficient is set by operating the display position of the plurality of line segments displayed on the display means by the operation means. 4. The digital camera according to claim 3, wherein the display means displays a third digital image signal generated by the synthesizing means in a through image display in which images can be continuously confirmed. 4. The digital camera according to claim 3, wherein the display means displays a third digital image signal generated by the synthesizing means in a preview image display for confirming an image after photographing.

Images