JP2002199203A - Correction method for photographed image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a correction method for photographed image that employs a simple arithmetic expression so as to correct distortion of a photographing lens and distortion of an original image due to a curved exposure image during photographing. SOLUTION: Coordinates (Px, Py) representing a position of an ideal image point formed at exposure under the assumption that an exposed image is on a plane and correction parameters α, β, γ, RF, LC determined on the basis of the performance of the photographing lens, a radius of curvature of the exposed face, and a distance from a center of an emissive pupil of the photographing lens to a center of the exposed face are applied to the prescribed arithmetic expression to obtain a cross-reference between coordinates (Fx, Fy) of pixels on the original image and coordinates (Px, Py) on which the pixels are rearranged and the pixels of the original image are rearranged on the basis of the correspondence relationship.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for correcting a photographed image for correcting distortion of an original image due to distortion of a photographing lens and curvature of an exposure screen during photographing.

[0002]

2. Description of the Related Art At present, as a photographing device for photographing,
In addition to a single-lens reflex camera, a compact camera, and the like, a film unit with a lens that enables a user to easily enjoy photography is known. A film unit with a lens is a unit that incorporates a photographic mechanism, such as a photographic lens and shutter device, with an unexposed photographic film built in beforehand. Because of the simplicity that they only need to be brought to a developing store, they are widely used in general.

A photographing lens mounted on a film unit with a lens as described above generally comprises one or two resin lenses. When the photographing lens is composed of one or two lenses in this way, it is difficult to improve various aberrations and improve the image quality only by the performance of the photographing lens. For this reason, in the conventional film unit with a lens, with respect to the field curvature of the photographing lens, which is one factor that deteriorates the image quality, the longitudinal direction of the exposure screen is curved so as to have a center of curvature on the object side. By supporting the photographic film and exposing the film surface of the photographic film to light, good focus is achieved over the entire exposure screen.

[0004] In addition to the above-mentioned curvature of field, distortion (distortion) caused by the performance of a photographic lens is a typical cause of image quality deterioration. Distortion occurs when the imaging magnification changes according to the distance from the exit pupil to the imaging plane (film plane).

[0005] For a camera such as a single-lens reflex camera which can be costly to a certain extent, an image whose distortion has been well corrected is printed on a photographic film by using a high-precision photographing lens combining a large number of lenses. be able to. However, in the case of a film unit with a lens or a low-priced compact camera, the cost of the photographing lens cannot be increased so much that the occurrence of distortion of the image projected on the photographic film cannot be sufficiently suppressed. is the current situation.

[0006] To solve the problem of image quality deterioration as described above,
An image processing method and an image processing apparatus for correcting aberration of an image according to aberration characteristics of a photographing lens obtained through a certain information acquisition unit are disclosed in Japanese Patent Application Laid-Open Nos. 11-313214 and 20.
It is known from JP 00-125174. According to these, even if an image is captured by a camera that generates distortion, such as a film unit with a lens, distortion can be corrected by image processing to obtain a high-quality image without distortion.

For example, in an image processing method described in Japanese Patent Application Laid-Open No. H11-313214, when an original image recorded on a photographic film is optically read by a scanner or the like and extracted as original image data for each pixel. The lens information of the photographing lens that has photographed the original image is simultaneously read, and image processing for correcting distortion is performed on the original image data based on the obtained lens information and output.
At the time of this image processing, the coordinate values set in the original image data are corrected using a correction formula set in advance according to the lens information,
The coordinates are converted by a correction coefficient used in the correction formula, and the distortion is corrected by rearrangement. In the image processing method described in JP-A-2000-125174, a distortion rate f (r) = (r′−r) / r ′ is used as a correction equation for correcting distortion.
(Where r is the distance from the optical axis, and r 'is the distance after the distance r has fluctuated due to the distortion). Image processing for correcting the distortion is performed.

[0008]

However, Japanese Patent Application Laid-Open No.
In the image processing method described in US Pat. No. 3,132,214, a correction formula that is set in advance in accordance with lens information is not specifically given. If a complicated correction formula is used in such an image processing method, an enormous amount of time is required in the course of arithmetic processing using the correction formula, which is not suitable for handling a large number of photographic films.

Further, the image processing method described in Japanese Patent Application Laid-Open No. 2000-125174 corresponds only to the case where distortion of a photographic lens is corrected. However, as described above, when a photographic film is supported by being curved, as in the case of a film unit with a lens, the curvature also causes distortion.
Therefore, satisfactory image quality cannot be obtained only by correcting the distortion of the taking lens.

The present invention has been made in view of the above circumstances, and provides a simple calculation of both distortion caused by the performance of a photographic lens and distortion caused by the photographic film being curved and supported during exposure. It is an object of the present invention to provide a method of correcting a captured image that can be corrected by processing.

[0011]

According to a first aspect of the present invention, there is provided a method for correcting a photographed image in which a distortion of an original image due to distortion of a photographing lens and curvature of an exposure screen during photographing is eliminated. By calculating the position on the original image based on the ideal position of the pixel corresponding to the ideal image point and the correction parameters predetermined according to the distortion of the shooting lens and the curvature of the exposure screen at the time of shooting. , The correspondence of the ideal position to the position of each pixel of the original image is obtained, and each pixel of the original image is rearranged to the corresponding ideal position based on this correspondence.

According to a second aspect of the present invention, there is provided a method for correcting a photographed image.
For an original image photographed with a concave surface curved only in one direction, the position where the optical axis of the photographing lens intersects the photographic film is defined as the origin, and the curved direction is the X-axis direction, and the direction orthogonal to the X-axis direction. Is set as the Y-axis direction, and the coordinates of an arbitrary pixel on the exposure screen and the coordinates of the physical position on the exposure screen are set, the X coordinate of the ideal position is P _x , and the Y coordinate is P _y , the X coordinate of the position of an arbitrary pixel on the original image corresponding to the ideal position is F _x , the Y coordinate is F _y, and the correction parameters corresponding to the distortion of the photographing lens are α, β, γ, and the curvature radius R _F of the curved exposure screen and the distance L _C from the center of the exit pupil of the taking lens to the position where the optical axis of the taking lens intersects the photographic film are corrected according to the curvature of the exposure screen. when a parameter, F _{x ^{R F · tan -1 (W x}} / (R F -W z)) F y = ((L C -W z) · D Y) / L C _{where, D x = P x · (} 1 + α · √R + β · R + γ · R ² ) D _Y = P _Y · (1 + α · √R + β · R + γ · R ² ) R = √ (P _x ² + P _Y ² ) W _x = (− D _x / (M · L _C )) · ( N-√ (N ² -M
_Dx ² ) −M · L _C ) W _z = (N−√ (N ² −M · D _x ² )) / M M = 1 + (D _x ² / L _C ² ) N = R _F + (D _x ^The relationship between the position of each pixel on the original image and the ideal position is determined by the expression ² / L _C ).

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of a film unit with a lens for photographing while supporting the film surface to be curved. The lens-equipped film unit 2 includes a unit main body 3 in which various photographing mechanisms are incorporated, and an exterior paper 4 partially covering the unit main body 3. The unit main body 3 is pre-loaded with an unexposed photographic film. I have.

On the front surface of the unit body 3, a photographing lens 5, an object side window 6a of a finder 6, a strobe light emitting section 7,
A strobe operation member 8 for turning on / off the strobe unit is provided. On the upper surface, a shutter button 9 and a counter window 1 for displaying the number of remaining photographable frames are displayed.
0, an opening 12 from which a display light guide 11 for indicating completion of strobe charging is provided. further,
On the back side of the unit main body 10, a hoisting knob 13 that is operated to rotate every time one frame is shot is exposed.

FIG. 2 is an exploded perspective view of the unit main body 3. The unit main body 3 includes a main body base 15, a front cover 16,
It comprises a rear cover 17, a strobe unit 18, a battery 19 and the like, and a film cartridge 20 is loaded into the unit body 3 at the time of manufacture. Film Patrone 20
Is a 135 type, and includes a patrone 21 and a negative type photo film 22.

In the center of the front surface of the main body base 15, a dark box 24 for shielding the photographing optical path from the photographing lens 5 to the photographic film 22 is integrally formed. On both sides of the dark box 24, a patrone room 25 for accommodating the patrone 21 and a film room 26 for accommodating the photographic film 22 drawn out of the patrone 21 and wound into a roll shape.
And are provided integrally.

On the outside of the dark box 24, various components constituting a shutter mechanism, a film count mechanism, and the like for driving shutter blades in response to a pressing operation of the shutter button 9, a photographing lens 5, and the like are mounted. On the back surface of the dark box 24, an aperture (not shown) for defining a size of a photographed frame on the photo film 22, that is, an exposure screen 22a is formed. The exposure screen 22a has a size of about 24 × 36 mm and is a rectangle that is long in the longitudinal direction of the photographic film 22. The center of the exposure screen 22a is defined so as to coincide with the photographing optical axis 5a of the photographing lens 5.

A winding knob 13 is rotatably mounted on the upper part of the patrone chamber 25. By rotating the winding knob 13, the photographed portion of the photographic film 22 is wound up into the patrone 21, and the unexposed portion is set behind the aperture.

The front cover 16 has a viewfinder 6 on its front surface.
In addition to the objective side window 6a, an opening for exposing the photographing lens 5, the strobe light emitting unit 7, and the strobe operation member 8 is formed, and covers the front surface of the main body base 15.

The rear cover 17 is attached so as to cover the rear surface of the main body base 15. Thereafter, a bottom cover 17 for closing the bottom surfaces of the patrone chamber 25 and the film chamber 26 is provided on the cover 17.
a and 17b are integrally formed. After the rear cover 17 is attached to the main body base 15 loaded with the film cartridge 20, the bottom covers 17a and 17b are closed, and the cartridge chamber 25 and the film chamber 26 are light-tightly closed. Bottom lid 1
Reference numeral 7a is opened when the film cartridge 20 which has been photographed at the developing laboratory is taken out.

The rear cover 17 is provided with a film support surface 30 at a portion facing the aperture of the main body base 15. The gap between the film support surface 30 and the main body base 15 forms a film feed path that connects the patrone chamber 25 to the film chamber 26.

The feeding direction of the photographic film 22 is curved so that the film supporting surface 30 becomes concave toward the object side. It is curved in the feeding direction of the photographic film 22 so as to be convex on the side.

The photographing light from the photographing lens 5 enters the dark box 24 and gives exposure to the exposure screen 22a of the photographic film 22. The film surface of the exposure screen 22a positioned on the back side of the aperture has a center of curvature on the photographing lens side (object side) as shown in FIG. 3 by the above-mentioned film support surface 30 and the guide rail. The exposure screen 22a is supported in a shape in which the longitudinal direction of the exposure screen 22a is curved with a radius of curvature R _F. Thereby, the blurring of focus due to the curvature of field of the photographing lens 5 is improved.

The strobe unit 18 is formed integrally with a printed circuit board 32 on which various electric parts are mounted, a strobe light emitting portion 7 composed of a discharge tube, a reflector, a diffusion plate, etc., a charge switch 33, a synchro switch 34, and a strobe operation member 8. And a receiving plate 36 that slidably supports the switch plate 35, and uses the battery 19 as a power source. This strobe unit 18
Is charged when the flash operation member 8 is slid upward and the charging switch 33 is turned on, and the flash is emitted when the synchro switch 34 is turned on in synchronization with the opening and closing of the shutter blades.

A model code unique to the model of the lens-equipped film unit is optically side-printed on the photographic film 22 loaded in the lens-equipped film unit. In the present embodiment, the correction parameters α, γ, β, L _C , and R used in the distortion correction processing will be described later in detail by using the model code side-printed on the photo film 22 in the related art. _{Specify F.}

FIG. 4 shows the configuration of a digital printer embodying the present invention. The digital printer 40 is roughly composed of an image input unit 41 having a function as a correction device and an image recording unit 42 for printing an image on photographic paper. The image input unit 41 receives the model of the photographing device. A code reader 43 as an input means, a scanner 44 for reading a color image from each exposure screen 22a of the photo film 22, a first image memory 45a, a second image memory 45b, an image processing circuit 46, and a controller 47 for controlling them Become.

When the developed photo film 22 is set in the digital printer 40, the photo film 22 is transported by a transport mechanism (not shown), and
3 to the scanner 44.

The code reader 43 is composed of a light source for illuminating the photographic film 22, a photosensor disposed on the opposite side of the light source across the conveyance path of the photographic film 22, and the like. Is optically read from the photographic film 22 being conveyed. The reading of the model code is performed for each photo film, and the read model code is sent to the image processing circuit 46 via the controller 47.

The scanner 44 is a film carrier for supporting the photographic film 22 on a flat surface, and an exposure screen 22a which is set on the film carrier by diffusing light from a lamp.
, An CCD for reading an original image in the exposure screen 22a, a lens for forming the original image on the CCD, and the like.

Each time the photographic film 22 is fed by one frame, the scanner 44 separates and measures the original image on the exposure screen 22a in three colors of red, blue and green by the CCD, and converts the obtained photoelectric signal into an A / D signal. Send to converter 48. A / D converter 48
Converts the density of each position on the exposure screen 22a into corresponding three-color image data by digitally converting the photoelectric signal of each color. The three color image data is written to the first image memory 45a. Thereby, the exposure screen 22a
Is decomposed into a number of pixels, and the image data of each pixel is written to the address of the first image memory 45a corresponding to the position on the exposure screen 22a on a one-to-one basis. In addition,
Any type of image data may be used.
Instead of color image data, for example, luminance data and color data may be used as image data.

When image data for one screen is written into the image memory 45a, the image processing circuit 46 reads out the image data and performs predetermined image processing. For the photo film 22 in which the model code is recorded, the first image memory 45a is used.
By writing the image data as the corrected image data in the second image memory 45b so as to rearrange the pixels read from the camera, the exposure screen 22a is curved when the photographic lens 5 is distorted and exposed. A distortion correction process for correcting distortion is performed. After the distortion correction process,
Normal image processing such as color correction for printing and negative / positive inversion processing is performed on the corrected image data of the corrected image subjected to the distortion correction processing. The corrected image data subjected to the normal image processing is sent to the image recording unit 42.

Prior to performing the distortion correction process, the image processing circuit 46 corrects one screen of correction LUs commonly used for each exposure screen 22a of one photographic film 22.
T (lookup table) is created in the work memory 46a. As described above, the processing time is shortened by performing the distortion correction processing on one photo film 22 using the common correction LUT.

The image processing circuit 46 includes a work memory 46
a and the EEPROM 46b are connected. The work memory 46a is used not only for creating a correction LUT but also for temporarily storing data required when the image processing circuit 46 performs image processing.

[0034] The EEPROM46a, correction parameters above _{α, γ, β, L C} , R F have been written for each model code, the image processing circuit 46, the correction parameter corresponding to the model code alpha, gamma, beta , L _C , and R _F to perform distortion correction processing. Note that the correction parameters α,
By storing γ, β, L _C , and R _F in the EEPROM 46a, it is possible to add correction parameters α, γ, β, L _C , and R _F corresponding to a new model of a film unit with a lens.

The coordinates (P _x , P _y ) for one screen used as an ideal position of a pixel corresponding to an ideal image point are written in the EEPROM 46a. The ideal image point is
Assuming that the taking lens 5 has no distortion and that the exposure screen 22a is flat at the time of exposure, it is an image point formed on the exposure screen 22a, and has coordinates (P _x ,
P _y ) represents the position where the pixels of the original image are to be rearranged by the distortion correction processing, using an XY plane coordinate system described later. Note that the corrected image subjected to the distortion correction is composed of a large number of pixels in the same manner as the original image read by the scanner 44. Therefore, the coordinates (P _x , P _y ) are the pixels of one screen assumed after the distortion correction. It only needs to be prepared for a few minutes and can be determined in advance by calculation.

The image recording section 42 includes an image memory 51, a laser unit 52 for outputting red, blue and green laser beams, and a driver 5 for controlling the output of the laser unit 52.
3, a polygon mirror 54, an Fθ lens 55, a transport mechanism (not shown) for transporting a long color photographic paper 56, and the like.

The corrected image data from the image input unit 41 is
The data is written to the image memory 51. The output of the laser unit 52 is controlled by the corrected image data in the image memory 51, and the polygon mirror 54 that rotates at high speed is irradiated with laser light. Thereby, the scanning of the laser light is performed in the width direction of the color photographic paper 56 (the direction orthogonal to the transport direction), and the corrected image obtained from the exposure screen 22a by transporting the color photographic paper 56 in the longitudinal direction is obtained. The color photographic paper 56 is exposed. The exposed color photographic paper 56 is developed by a developing unit (not shown), and then cut into single images to be printed photographs.

The distortion correction processing performed by the image processing circuit 46 will be described. As shown in FIG. 5, the image processing circuit 46 sets the center of the exposure screen 22a, that is, the position of the photographing optical axis 5a on the exposure screen 22a as the origin O, and sets the longitudinal direction (curved direction) of the exposure screen 22a to X Using the XY plane coordinate system in which the width direction of the exposure screen orthogonal to the axis and the longitudinal direction is the Y axis, the X coordinate of an arbitrary pixel of the original image read from the exposure screen 22a which is a plane is represented by “F _x ”. Y coordinate is "F _y "
And the corrected coordinates, that is, the X coordinate of the ideal image point is “P _x ” and the Y coordinate is “P _y ”.

The image processing circuit 46 calculates the coordinates (F _x , F _y ) and the coordinates (P _x ) according to the following arithmetic expressions (a) and (b).
_x , P _y ) is created,
The distortion correction is performed by rearranging the pixels at the coordinates (F _x , F _y ) to the coordinates (P _x , P _y ) based on the correspondence shown in the correction LUT.

F _x = R _F tan ⁻¹ (W _x / (R _F −W _z )) (a) F _y = ((L _C −W _z ) · D _Y ) / L _C ··· (B) where D _x = P _x · (1 + α · √R + β · R + γ · R ² ) D _Y = P _Y · (1 + α · √R + β · R + γ · R ² ) R = √ (P _x ² + P _Y ² ) W _x = (− D _x / (M · L _C )) · (N−√ (N ² −M ·
_Dx ² ) −M · L _C ) W _z = (N−√ (N ² −M · D _x ² )) / M M = 1 + (D _x ² / L _C ² ) N = R _F + (D _x ² / L _C )

Hereinafter, the above arithmetic expressions will be described. Assuming that the exposure screen 22a at the time of the exposure is a plane, when the photographing is performed by the photographing lens 5 having the distortion, the coordinates (P _x , P _x) in the XY plane coordinate system are schematically shown in FIG. _The ideal image point PP to be formed at the position _y ) is formed at the image point PD at the coordinates (D _x , D _y ) under the influence of the distortion of the taking lens 5.

In general, the distortion of the photographing lens 5 is calculated by using the ideal image height R ₁ and the formed image height R ₂ as “D = (R ₂
-R ₁₎ / represented by R ₁ ". Also, as described on page 102 of “Lens Design Method (Kyoritsu Shuppan: Yoshiya Matsui) First Edition, Eighth Printing”, assuming that the third-order aberration coefficient V ₁ and the fifth-order aberration coefficient V ₂ are “D = −50”・ (V ₁・ (N ₁・ tan
_{^{ω) 2 + (V 2/}} 4) (N 1 tan ω) can be represented by ⁴ "," N ₁ tan omega "in this formula is the term corresponding to the ideal image height R _1. By giving the ideal image height to such an expression, it is possible to obtain the image forming position by distortion when the exposure screen 22a is supported on a plane, that is, the position of the image point PD corresponding to the ideal image point PP.

In this example, based on the above equation, assuming that the exposure screen 22a at the time of exposure is a plane, the ideal image point PP
And the image point PD deviated by the distortion of the taking lens 5 are defined as the following (1) and (2) using correction parameters α, β, and γ determined by the performance of the taking lens 5. . D _x = P _x · (1 + α · √R + β · R + γ · R ² ) (1) D _Y = P _Y · (1 + α · √R + β · R + γ · R ² ) (2) where R = √ (P _x ² + P _Y ² )

In the case where the taking lens 5 has distortion and the exposure screen 22a is curved and supported at the time of exposure in order to correct the field curvature as in the case of the film unit with lens 2 described above, Ideal image point PP
Is formed as an image point PF further deviated from the image point PD under the influence of the curvature of the exposure screen 22a, and the image point PF is subjected to coordinates (F _x ,
F _y ).

FIG. 7 shows an XYZ coordinate system obtained by expanding the above XY plane coordinate system with the optical axis direction of the photographing lens 5 as the Z axis. 7 is a center EP (coordinates (0, 0, L _C )) of the exit pupil of the photographing lens 5, and a symbol Rc is
The center of curvature of the exposed screen (coordinates (0,0, R _F)) represents a, Z coordinates L _C of the center EP of the exit pupil is equal to the distance from the center EP of the exit pupil to the center of the exposure window 22a , and the Z-coordinate R _F of the center of curvature Rc, the same value as the radius of curvature of the exposed screen 22a. The direction of the arrow in each axis is defined as the positive direction of each coordinate.

From the flat exposure screen 22a, the scanner
The image point PF read at 44 is in the XYZ coordinate system described above.
, Coordinates on the exposure screen 22a curved at the time of exposure
(W _x, W_y, W_z) Is formed at the image point PW represented by
Then, each image point PW, PF, PD, viewed from the Y-axis direction,
FIG. 8 shows the relationship between the center of curvature Rc and the center EP of the exit pupil.
As shown.

As can be seen from the relationship diagram of FIG.
The X coordinate F _x, arc between the origin O and the image point PW (hereinafter, referred to as an arc OW) is equal to the length of it and the line segment EP-PD toward the image point PD from a center EP of the exit pupil, the arc The coordinates of the intersection of the OPs, that is, the X coordinate W _x and the Z coordinate W of the image point PW
It can be obtained by finding _z . Then, the line segment EP-PD is calculated by the following equation (3),
Is represented by the following equation (4). X = − (D _x / L _C ) · Z + D _x (3) (Z−R _F ) ² + X ² = R _F ² (4)

From the above equations (3) and (4), the X coordinate W _x and the Z coordinate W _z of the image point PW are obtained by the following equations (5) and (6). Expressions (5) and (6) take into account that the intersection of the arc OW, that is, the curved exposure screen 22a and the line segment EP-PD is closer to the origin O than the center EP of the exit pupil. . W _x = (− D _x / (M · L _C )) · (N−√ (N ² −M · D _x ² ) −M · L _C ) (5) W _z = (N−√) (N ² −MD D _x ² )) / M (6) where M = 1 + (D _x ² / L _C ² ) N = R _F + (D _x ² / L _C )

An angle formed by a line segment Rc-PW from the center of curvature radius Rc to the image point PW and the photographing optical axis (Z axis) is represented by “θ”.
When _x "(radian), the length of the arc OP, i.e. the X coordinate F _x of an image point PF is obtained by the following equation (7). F _x = R _F · θ _x (7)

Then, “θ _x ” in the equation (7) is
X coordinates W _{x of} the image point PW obtained from the equations (5) and (6),
By using the Z-coordinate W _z, and Z coordinates R _F of the center Rc of the radius of curvature, because is expressed by the following equation (8), the result as the equation (a), any physical image image point PP Corresponding image point P
It is possible to calculate the X coordinate F _x of F. θ _x = tan ⁻¹ (W _x / (R _F −W _z )) (8)

On the other hand, the relationship between the image points PW, PF, PD and the center EP of the exit pupil when the above XYZ coordinate system is viewed from the X-axis direction is as shown in FIG. A line segment EP-PD from the center EP of the exit pupil to the image point PD, and a photographing optical axis (Z axis)
Is the angle formed by “θ _y ”, the following equation (9) is established, and the Y coordinate W _y of the image point PW is obtained by dividing the angle “θ _y ” with the Z coordinate W _z of the image point PW. It can be expressed as in the following equation (10). tan θ _y = D _Y / L _C (9) W _y = (L _C −W _z ) · tan θ _y (10)

[0052] exposure window 22a is supported by the curved shape of the longitudinal direction (X-axis direction), because not curved in a width direction (Y axis direction), Y-coordinate F _y of the image point PF is the image point It becomes the same as the Y coordinate W _{y of the} PW (F _y = W _y ). Therefore, by the above (b) obtained from the above equations (9) and (10), an image point P corresponding to an arbitrary image point PP is obtained.
It is possible to calculate the F Y coordinate F _y.

As a result, the coordinates (P _x , P _x ) of an arbitrary pixel as the ideal image point PP are obtained from the above-mentioned arithmetic expressions (a) and (b).
_Y ), the correction parameters α, β, γ corresponding to the distortion of the photographing lens 5 and the respective correction parameters R _F , L _C corresponding to the curvature of the exposure screen, to obtain a pixel which is an ideal image point PP. The coordinates (F _x , F _x) of the pixel corresponding to the image point PF
_y ) can be obtained.

The correction parameters α, β, and γ are determined by the photographing lens 5 incorporated in the film unit 2 with a lens.
Can be determined by calculation or experimentally from the specifications. As described above, the correction parameter R _F is
This is the radius of curvature of the exposure surface 22a.
_C is the exposure screen 22a from the center of the exit pupil of the photographing lens 5.
Are obtained from the specifications of the film unit with lens 2 and the taking lens 5 incorporated therein. Then, each correction parameter α, β,
γ, R _F and L _C are associated with the model code and
Written to M46b.

At the time of creating the correction LUT, the image processing circuit 46 calculates the arithmetic expressions (a) using the correction parameters α, β, γ, L _C and R _F read from the EEPROM 46.
By applying the coordinates (P _x P _Y ) (P _x and P _Y are real numbers) of each pixel for one screen prepared in advance as the coordinates of the ideal image point PP to (b), one screen is (F _x , F _Y ) (F _x , F _Y are real numbers). Then, the coordinates (P _x , P _Y ) used for the calculation and the coordinates (F _x , F _Y ) obtained from the coordinates are written in the work memory 46a in association with each other, thereby creating a correction LUT.

In the distortion correction processing, the image processing circuit 46
Reads the image data of each pixel sequentially from the first image memory 45a, converts the address of the first image memory 45a used at the time of this reading into coordinates (F _x , F _Y ), and obtains the obtained coordinates (F _x , F _Y ) corresponding to coordinates (P _x ,
P _Y ) is taken out of the correction LUT. Then, the extracted coordinates (P _x , P _Y ) are converted into addresses again, and the target image data is written into the second image memory 45b using the addresses. Then, this process is performed for each pixel. In this manner, the first
The distortion correction processing is performed by writing the image data of each pixel stored in the image memory 45a to the second image memory 45b.

In this example, the first image memory 45a
Address of coordinates (F_x, F_Y) And its coordinates
(F_x, F_Y) Based on the correction LUT
Mark (P _x, P_Y) To the address of the second image memory 45b.
The coordinates (F_x, F_YThe first stroke corresponding to)
The address of the image memory 45a and the coordinates (P_x, P_Y) To
Corresponding to the address of the corresponding second image memory 45b.
Create an LUT and use this LUT to directly
From the address of the first image memory 45a to the second image memory 45
The address may be converted to the address b. In this way,
Processing can be sped up.

Further, the above operation (a) is performed by using "tan ^-1 "
, Which can be an approximation to a simple expression with some constant parameters,
It is possible to speed up the arithmetic processing.

Next, the operation of the above configuration will be described. A model code corresponding to the loaded film unit with lens 2 is side-printed on the photo film 22 of the film cartridge 20. This photo film 22
It is loaded into the unit body 3 together with the patrone 21.
Then, the exterior paper 4 is attached to the completed unit main body 3 to complete the lens-fitted film unit 2, which is shipped and provided for photographing under the user.

At the time of photographing, first, the winding knob 13
To rotate. As a result, the photo film 22 is wound up by one frame, and the shutter is charged. Thereafter, the photographer presses the shutter button 9 after framing with the viewfinder 6. To perform flash photography, the flash operation member 8 is slid upward and the shutter button 9 is pressed after charging is completed. When the shutter button 9 is pressed, the shutter blade swings and the shutter opening is opened and closed.

During the opening and closing of the shutter opening, the photographing light transmitted through the photographing lens 5 enters the dark box 24 and exposes the photographic film 22 exposed in the aperture, ie, the film surface in the exposure screen 22a. give. At this time, the film surface is supported with its longitudinal direction being curved.

The photographing is sequentially performed in the same manner as described above. After the photographing of all the frames is completed, the user rotates the winding knob 13 continuously to store all the photographic films 22 in the cartridge 21. And this film unit with lens 2
To a photo lab or DPE store.

At a developing laboratory or the like, the photographed film cartridge 20 is taken out of the unit body 3. The photographic film 22 is taken out of the patrone 21 and separated from the patrone 21. The photographic film 22 is set in a digital printer 40 after being processed by a predetermined developing device.

The digital printer 40 is a photo film 2
When 2 is set, the leading end is conveyed toward the scanner 44. During this conveyance, as shown in FIG. 10, the controller 47 reads the model code recorded on the photo film 22 using the code reader 43 and sends the read model code to the image processing circuit 46.

The image processing circuit 46 receives the model code
Then, the corresponding correction parameters α, β, γ, L
_C, R_FIs read from the EEPROM 46b. And
Each of these correction parameters α, β, γ, L_C, R_FFor
The calculated equations (a) and (b) are converted from the EEPROM 46b.
The coordinates (P_x, P_Y)
By applying the following, the coordinates (P_x,
P_Y) (F) _x, F_Y)
You.

When the above-mentioned correction LUT is created, calculations are performed on one quadrant, for example, only the first quadrant, using the arithmetic expressions (a) and (b). It is efficient to change only the sign of the operation result in the first quadrant. The coordinates (P _x , P _Y ) are stored in the EEPROM 46.
b, instead of being prepared in advance, based on the pixel spacing,
The calculation may be performed sequentially by increasing or decreasing the coordinates (P _x , P _Y ) by predetermined steps.

The coordinates (F _x , F _Y ) obtained by the above calculation
And the coordinates (P _x , P _Y ) used for the calculation are written in the work memory 46a in association with each other, whereby a correction LUT is created. .

On the other hand, when the first exposure screen 22a of the photographic film 22 reaches the film carrier of the scanner 44 by the conveyance, the conveyance is stopped. During this stop, the original image in the exposure screen 22a is read by the scanner 44, converted into three-color image data by the A / D converter 48, and written into the first image memory 45a. When the image data for one screen is written in the first image memory 45a, the image processing circuit 46 sequentially reads out the image data from the image memory 45 by specifying an address, as shown in FIG.

The image processing circuit 46 converts one piece of image data
When read, the address of this image data is set to coordinates (F_x,
F_Y). Next, using the correction LUT,
(F _x, F_Y) To the corresponding coordinates (P_x, P_YConvert to
You. Then, coordinates (P obtained from the correction LUT)_x, P_Y)
Is converted to an address, and then the image
Data as corrected image data in the second image memory 45b.
Get in.

When the conversion processing is performed as described above and one piece of image data is written to the second image memory 45b, new image data is read from the image memory 45, and the conversion processing is performed in the same procedure as described above. Is performed, and the first image memory 45
The image data read from a is written into the second image memory 45b as corrected image data. Similarly,
The conversion process is performed while reading the image data sequentially,
The corrected image data is written to the second image memory 45b.

Thus, as schematically shown in FIG. 12, the coordinates (F _x , F _Y ) on the original image read by the scanner 44 are, for example, the coordinates (J + 2, I−1) and the coordinates (J + 1, I), the image data of each pixel at the coordinates (J, I + 1) is D1, D2, D3, and the coordinates (P _x , P _Y ) corresponding to these pixels are (J, I−1) and the coordinates ( J, I) and the coordinates (J, I + 1), the corrected image data of the coordinates (J, I-1) is set to D1 and the corrected image data of the coordinates (J, I) is set by the distortion correction processing. D2
Then, each pixel of the original image is stored in the second image memory 4 so that the corrected image data of the coordinates (J + 1, I + 1) becomes D3.
5b is rearranged and written. In FIG. 12, X
Although the case where only coordinates are transformed is drawn, in actuality,
The Y coordinate is also converted according to the correspondence.

As described above, the first image memory 45a
All the pixels for one screen above are rearranged and written in the second image memory 45b, thereby completing the distortion correction processing.

When the distortion correction processing is completed, the image processing circuit 46 performs normal image processing such as color correction for printing and negative / positive inversion processing on each of the corrected image data in the second image memory 45b. Is written in the image memory 51 of the image recording unit 42. At the time of the normal image processing, exposure unevenness, chromatic aberration, and the like may be corrected.

When the corrected image data for one screen is written into the image memory 51, the image recording unit 42 drives the laser unit 52 based on the corrected image data of the three colors, and color-prints the color photographic paper 56. Record the image as a latent image.

When the recording of a color image for one screen is started, the next exposure screen 22a is set on the scanner, and the distortion correction processing is performed in the same procedure as described above. At this time, the correction LUT created first is used. After the distortion correction processing is completed for one screen of image data, normal image processing is performed, and then each corrected image data is written to the image memory 51 of the image recording unit 42. And
After the completion of the recording of the color image whose recording has been started first, the color image is recorded on the color photographic paper 56 based on the corrected image data.

Thereafter, in the same manner, one photographic film 22
The color image read from each exposure screen 22a is subjected to distortion correction processing and normal image processing, and
Record a color image in

The exposed color photographic paper 56 is sent to a developing process, where it is developed, fixed, dried, and the like, cut into individual images, and discharged from the digital printer 40 as a print photograph. The print photograph thus obtained contains a color image in which image distortion has been corrected and corrected.

[0078]

Next, an embodiment will be described. In the embodiments, description will be made with reference numerals common to the above description. The photographing lens 5 of the lens-fitted film unit 2 used in this embodiment has a two-lens configuration including a first lens on the object side and a second lens on the exposure screen side.

The specifications of the lens-fitted film unit 2 used in the examples are shown below. f = 33.14 mm FNo. = 8.0 f1 = 104.37 mm θ = 34 °

In the above data, "f" is the combined focal length of the entire photographing lens 5, "f1" is the focal length of the first lens, "FNo." Is the open value of the photographing lens, and "θ" is the photographing distance. The angle of view is half. The longitudinal direction of the exposure screen 22a has a radius of curvature R _F so that the exposure screen 22a has a concave surface on the photographing lens 5 side.
= 100 mm.

Table 1 below shows the lens data of the taking lens 5. The surface numbers in Table 1 are the first numbers given in order from the object side.
It is a number assigned to each lens surface of the lens and the second lens,
The space represents the lens thickness or air space between the lens and the next surface (unit: mm). The numerical value shown in the column of the image plane interval is a shift amount from the paraxial focus position to the best focus position, and indicates that the film surface is at the best focus position. Further, the lens surface indicated by (*) in Table 1 is an aspheric surface formed so as to satisfy the following conditional expression, and the aspheric surface coefficient is shown in Table 2. In addition. In the equation, c is the reciprocal of the radius of curvature, and h is the height of a ray from the optical axis. ^{Condition: Z = ch 2 / [1} + √ {1- (1 + k) c 2 h
² ｝] + Ah ⁴ + Bh ⁶ + Ch ⁸ + Dh ¹⁰

[0082]

[Table 1]

[0083]

[Table 2]

The degree of distortion when photographing with the film unit with lens 2 having the above specifications was examined by ray tracing. The results are shown in Table 3 using the angles (θ1, θ2) of the incident light with respect to the optical axis of the photographing lens 5 and the coordinates of the image forming point of the incident light. Table 3 and Table 5 below
The values of the coordinates in Table 6 are rounded to three decimal places.

[0085]

[Table 3]

In Table 3 above, the angle θ1 is the same as the aforementioned Z
In the XY coordinate system, the angle between the imaging optical axis on the ZX plane including the imaging optical axis and the incident light beam, and the angle θ2 is the angle between the imaging optical axis on the ZY plane including the imaging optical axis and the incident light beam. Further, each coordinate in Table 3 corresponds to the exposure screen 2
It is represented by coordinates corresponding to the image point PF (F _x , F _Y ) when 2a is a plane, and the unit is mm.

If the angle θ1 is the same, each angle θ2
Is the coordinate P _x originally corresponding to the angle θ1.
And the angle θ2 is the same,
The Y coordinate corresponding to each angle θ1 should be essentially the same as the coordinate P _Y corresponding to the angle θ2.

Here, the angle θ1 is “0 °”, “7.84”
4 ° ”,“ 15.463 ° ”,“ 22.686 ° ”,
Coordinate P of ideal image point PP at “29.424 °”
_x is “0”, “4.512”, “9.060”,
"13.690" and "18.472" (mm).
Further, when the angle θ2 is “0 °”, “5.237 °”, “1”
The coordinates P _Y of the ideal image point PP at “0.36 °”, “15.28 °”, and “19.92 °” are “0”, “3.
002 "," 5.988 "," 8.948 "," 11.
870 "(mm).

However, since the exposure screen 22a is curved at the time of distortion and exposure of the photographing lens 5, the coordinates in Table 3 are shifted from the coordinates (P _Y , P _Y ) and are distorted. .

[0090] with respect to the lens-fitted photo film unit, the correction parameter alpha, beta, gamma, set L _C, the R _F as shown in Table 4, corresponding to the angle .theta.1, .theta.2 of the incident ray each The coordinates (P _x , P _Y ), the corresponding coordinates (D _x , D _Y ), and the coordinates (F _x , F _Y ) are calculated using the above-described equations (1) and (2) and the arithmetic equations (a), Table 5 shows the results obtained using (b).

[0091]

[Table 4]

[0092]

[Table 5]

In the operation using the operation expression (a), instead of the function “tan ⁻¹ ”, its approximate function is expressed as “f (σ) =
δ · σ + ε · σ ³ ”and the constant parameters δ and ε
Was used after optimization. Table 6 shows the complementation accuracy by the optimized approximation function. As can be seen from Table 6, it is understood that a sufficiently high accuracy of the calculation result can be obtained even by using the approximation function. Note that δ = 0.99939
35, ε = −0.3086605.

[0094]

[Table 6]

The coordinates by the ray tracing shown in Table 3 and the table
4 (F _x, F_YRelationship with
Are shown in Table 7. The error values in Table 7 are used for ray tracing.
Coordinates and calculated coordinates (F_x, F_Y) Coordinate value
Is calculated as an absolute value using a non-rounded value.
Fractions are rounded down to three digits.

[0096]

[Table 7]

As can be seen from Table 7, the arithmetic expressions (a) and (a)
The deviation between the coordinates (F _x , F _Y ) obtained by (b) and the coordinates due to ray tracing is 0.012 at the maximum, and it can be seen that the distortion is corrected with high accuracy.

In the above embodiment, the correction parameter is specified by using the model code side-printed on the photo film. However, the model code is described outside the patrone, and this is manually or mechanically read. May be input. In addition, as long as the correction parameter can be specified, a code other than the model code may be used.The correction code for specifying the correction parameter may be side-printed on the photo film or written on the outside of the cartridge. Good

When the correction code is applied, the same code may be applied even if the type of the film unit with a lens is different as long as the correction is performed using the same correction parameter. Further, the correction parameter itself may be adopted as the correction code. Further, an instruction for simply executing the correction processing at the time of printing may be given as a correction code, and when the correction code is read, the distortion correction processing may be performed using a predetermined correction parameter.

In the above-described embodiment, an example has been described in which distortion is corrected for a photographic film photographed by a film unit with a lens. However, a camera such as a compact camera in which a film surface is curved and supported is used. The same processing can be performed on a photographed photo film. It is not possible to specify a correction parameter corresponding to the type (model) of the camera used for shooting from the 135-type photo film used in the camera. Alternatively, if a correction code corresponding to this is manually input to the digital printer, correction according to the model of the camera used for shooting can be performed.

Further, in the above-described embodiment, an example has been shown in which correction is performed on a 135-type photographic film.
Various types of photographic film such as nced Photo System IX240 model can be used. In the IX240 type photographic film, a transparent magnetic recording layer is provided on the photographic film, so that a correction code or the like may be recorded on the transparent magnetic recording layer. In a camera corresponding to this, data can be recorded on the magnetic recording layer. Alternatively, a correction code or the like may be recorded on the camera side and used in the distortion correction processing.

In the above description, an example in which the present invention is applied to a digital printer for creating a print photograph has been described.
It can be used for other devices and also for an independent correction device for correcting distortion.

[0103]

As described above, according to the present invention,
The correspondence relationship between the positions of ideal image points corresponding to the respective image points on the original image is calculated based on the positions of the ideal image points and the correction parameters predetermined according to the distortion of the photographing lens and the curvature of the exposure screen during photographing. By calculating the position of the image point on the original image based on the original image, and re-arranging each image point of the original image to the position of the corresponding ideal image point, the processing of the photographing lens is performed by a simple calculation. It is possible to correct image distortion caused by distortion and photographic film being curved at the time of exposure.

[Brief description of the drawings]

FIG. 1 is a perspective view showing the appearance of a film unit with a lens that supports a film surface in a curved manner.

FIG. 2 is an exploded perspective view showing a configuration of a film unit with a lens.

FIG. 3 is an explanatory diagram schematically showing a photographing lens and a curvature of a film surface.

FIG. 4 is a block diagram illustrating a configuration of a digital printer embodying the present invention.

FIG. 5 is an explanatory diagram showing coordinates of an exposure screen used for correction.

FIG. 6 is an explanatory diagram showing a movement of an image point caused by distortion of a photographing lens and curving of a photographic film during exposure.

FIG. 7 shows an XYZ coordinate system showing the relationship between the photographic film, the center of curvature Rc, and the center EP of the exit pupil.

FIG. 8 is a view showing each image point PW,
FIG. 4 is an explanatory diagram showing a relationship among PF, PD, a center of curvature Rc, and a center EP of an exit pupil.

9 is a view showing each image point PW,
FIG. 4 is an explanatory diagram showing a relationship between PF, PD, and a center EP of an exit pupil.

FIG. 10 is a flowchart illustrating a procedure for creating a correction LUT.

FIG. 11 is a flowchart illustrating a procedure for rearranging pixels.

FIG. 12 is an explanatory diagram illustrating a relationship between image data before rearrangement and image data after rearrangement.

[Explanation of symbols]

 22 Photo film 22a Exposure screen 43 Code reader 44 Scanner 45a, 45b Image memory 46 Image processing circuit 46b EEPROM

Claims (2)

[Claims] An original image on an exposure screen of a photographic film photographed with a concave surface facing the photographing lens side is decomposed into a large number of pixels and read, and these pixels are rearranged. Correction method for correcting the distortion of the original image due to the distortion of the exposure screen during shooting and the distortion of the exposure screen during shooting, the ideal image when there is no distortion of the original image due to the distortion of the shooting lens and the curvature of the exposure screen during shooting By calculating the position on the original image based on the ideal position of the pixel corresponding to the point and a correction parameter predetermined according to the distortion of the photographing lens and the curvature of the exposure screen at the time of photographing, the original image is calculated. The correspondence between the ideal position and the position of each pixel is obtained, and based on this correspondence,
A method for correcting a captured image, comprising rearranging each pixel of an original image to a corresponding ideal position. 2. For an original image photographed with the concave surface curved only in one direction, the position where the optical axis of the photographing lens intersects the photographic film is set as the origin, and the curved direction is defined as the X-axis direction. An XY plane coordinate system in which the direction orthogonal to the axial direction is set as the Y axis direction is set, and the position of an arbitrary pixel on the exposure screen as a plane and the coordinates of the physical position are respectively represented. _x , the Y coordinate is _Py, and the X at the position of an arbitrary pixel on the original image corresponding to the ideal position
The coordinates are F _x , the Y coordinates are F _y, and the correction parameters corresponding to the distortion of the taking lens are α, β, γ
Further, the curvature radius R _F of the curved exposure screen and the distance L _C from the center of the exit pupil of the taking lens to the position where the optical axis of the taking lens intersects the photographic film are the correction parameters according to the curvature of the exposure screen. Where F _x = R _F · tan ^-1 (W _x / (R _F -W _z )) F _y = ((L _C -W _z ) · D _Y ) / L _C where D _x = P _x · (1 + α · √R + β · R + γ · R ² ) D _Y = P _Y · (1 + α · √R + β · R + γ · R ² ) R = √ (P _x ² + P _Y ² ) W _x = (− D _x / ( M · L _C )) · (N−√ (N ² −M ·
^{_{D x 2) -M · L C}} ) W z = (N-√ (N 2 -M · D x 2)) / M M = 1+ (D x 2 / L C 2) N = R F + (D x ^{2. The} method according to claim 1, wherein the correspondence between the position of each pixel on the original image and the ideal position is obtained by the expression ² / L _C ).