JP2013145950A - Image processing device, image projection device, program, and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing device, an image projection device, a program, and a recording medium that enable suppression of deterioration in the image quality of a color shift area.SOLUTION: An image processing device comprises a specification unit, and a gradation correction processing unit. The specification unit, using a color shift amount depending on a projection direction of input image data input from an external device, specifies a target image in which a color shift occurs among images included in the input image data. The gradation correction processing unit performs gradation correction processing so as to reduce the visibility of a first area indicating an area where a color shift occurs in the target image.

Description

  The present invention relates to an image processing device, an image projection device, a program, and a recording medium.

  For example, in an image projection apparatus such as a liquid crystal projector, color misregistration occurs on the projection surface due to various aberrations (magnification chromatic aberration, Seidel aberration) of the lens. In particular, the closer to the end of the projection plane, the greater the degree. The coloration different from that of the original occurs on the projection surface, thereby degrading the image quality, and further, the sharpness of the characters / line drawings is lowered, so that the legibility is deteriorated. Therefore, technology to improve color shift caused by various aberrations (magnification chromatic aberration, Seidel aberration) of the lens by optical design, and measure the amount of color shift using an external imaging device, and make corrections based on the actual measurement results. The technology to do is known. In addition to a projector device, a technique for correcting color misregistration of an image due to optical aberration by image processing is known. In particular, in a short focus projector, since the influence of aberration due to a lens is large, a technique for correcting image quality deterioration due to color shift becomes important.

  For example, in Patent Document 1, for each edge portion of image data (a portion where luminance changes), a histogram is created by calculating a correction magnification indicating how much two colors included in the image data are shifted, A technique for correcting chromatic aberration of magnification using a correction magnification (final correction magnification) indicating the mode value of the created histogram is disclosed.

  However, since the technique disclosed in Patent Document 1 performs uniform correction by geometric transformation using the final correction magnification, color misregistration is performed in an area other than the image area having the final correction magnification. There is a problem that image quality deterioration of the area cannot be suppressed.

  The present invention has been made in view of the above, and an object thereof is to provide an image processing device, an image projection device, a program, and a recording medium that can suppress deterioration in image quality in a color misregistration region.

  In order to solve the above-described problems and achieve the object, an image processing apparatus of the present invention includes a color shift amount that depends on a projection direction of input image data input from an external device, and is included in the input image data. The gradation correction processing is performed so that the visibility of a specific unit that identifies a target image in which color misregistration occurs and a first region indicating a region in which color misregistration occurs in the target image is reduced. A tone correction processing unit.

  According to another aspect of the present invention, there is provided an image projection apparatus including the image processing apparatus and a projection unit that projects image data on which image processing has been performed by the image processing apparatus onto a screen.

  Furthermore, the program according to the present invention specifies a target image in which color misregistration occurs among images included in the input image data, using a color misregistration amount that depends on a projection direction of the input image data input from an external device. And a gradation correction processing step for performing gradation correction processing so as to reduce the visibility of a first region indicating a region in which color misregistration occurs in the target image. It is. The recording medium of the present invention is a recording medium that stores the above-described program.

  According to the present invention, there is an advantageous effect that image quality deterioration in a color misregistration region can be suppressed.

FIG. 1 is a block diagram illustrating a configuration example of a projector. FIG. 2 is a block diagram illustrating a configuration example of the image processing unit. FIG. 3 is a block diagram illustrating a configuration example of the video processor. FIG. 4 is a diagram illustrating an example of the projection direction of the pixels included in the input image data. FIG. 5 is an image diagram when color misregistration of 2 dots occurs. FIG. 6 is a diagram showing RGB planes. FIG. 7 is a flowchart illustrating an example of processing by the image adjustment unit. FIG. 8 is a diagram illustrating the edge amounts of the RGB planes. FIG. 9 is a diagram illustrating a result of the contrast adjustment process. FIG. 10 is a diagram illustrating the relationship between the reflectance of the image data projected on the screen and the position in the horizontal direction. FIG. 11 is a diagram showing the relationship between the reflectance of the image data projected on the screen and the position in the horizontal direction.

  Hereinafter, embodiments of an image processing device, an image projection device, a program, and a recording medium according to the present invention will be described in detail with reference to the accompanying drawings. Hereinafter, a liquid crystal projector will be described as an example of an image projection apparatus, but the present invention is not limited to this.

  FIG. 1 is a block diagram illustrating a schematic configuration example of a projector 100 according to the present embodiment. As shown in FIG. 1, the projector 100 includes an optical system portion 10, a control device 90, and a power supply device 101.

  The optical system portion 10 functions as a projection unit that projects the image data supplied from the control device 90 onto the screen. More specifically, it is as follows.

  The optical system portion 10 includes an illumination optical system 20 that emits illumination light, a color separation light guide optical system 40 that separates illumination light from the illumination optical system 20 into three color lights of blue, green, and red, and color separation light guide optics. A light modulating unit 50 that modulates the three color lights emitted from the system 40 according to image information, a light combining optical system 60 that combines the image light of each color emitted from the light modulating unit 50, and a light combining optical system 60 A projection optical system for projecting the combined image light onto the screen SC. Of these, the portions from the illumination optical system 20 to the light combining optical system 60 are housed in the optical component casing.

  The illumination optical system 20 includes a light source device 21, a concave lens 22, a first lens array 24, a second lens array 25, a polarization conversion device 26, a superimposing lens 27, and a light control mechanism 31.

  The light source device 21 is a light source that emits a light beam for illumination. For example, an arc tube 21a that is a high-pressure mercury lamp or the like, and an elliptical concave mirror 21b that collects the light beam emitted from the arc tube 21a and emits it forward. With. The concave lens 22 has a role of collimating the light flux from the light source device 21. For example, when the concave mirror 21b is a parabolic mirror, the concave lens 22 can be omitted.

  Each of the first lens array 24 and the second lens array 25 is a fly-eye lens made up of a plurality of element lenses arranged in a matrix. The light beam emitted from the light source device 21 is divided into a plurality of partial light beams by the element lenses constituting the first lens array 24. In addition, each partial light beam from the first lens array 24 is emitted at an appropriate divergence angle by the element lenses constituting the second lens array 25.

  The polarization conversion device 26 is composed of a prism array incorporating a PBS and a wavelength plate, and converts the split light beam emitted from the lens array 25 into only linearly polarized light in a specific direction and supplies it to an optical system downstream of the optical path. Part.

  The superimposing lens 27 appropriately superimposes the illumination light as linearly polarized light that has passed through the polarization converter 26 as a whole, thereby superimposing illumination on the liquid crystal light valves 50r, 50g, and 50b of the respective colors provided in the illuminated region, that is, the light modulation unit 50. Enable. That is, the illumination light that has passed through the first lens array 24, the second lens array 25, and the superimposing lens 27 is provided in the light modulation unit 50 through the color separation light guide optical system 40 described in detail below. Further, the liquid crystal panels 51r, 51g, 51b of the respective colors are uniformly superimposed and illuminated.

  The dimming mechanism 31 is disposed inside the illumination optical system 20, for example, between the first lens array 24 and the second lens array 25, and partially illuminates the illumination light emitted from the illumination optical system 20. The light can be shielded, and the illumination light quantity, that is, the emission intensity of the illumination light is adjusted.

  The color separation light guide optical system 40 includes a first dichroic mirror 41a, a second dichroic mirror 41b, reflection mirrors 42a, 42b, and 42c, three field lenses 43r, 43g, and 43b, and relay lenses 44a and 44b. The illumination light emitted from the light source device 21 is separated into three colors of red (R), green (G), and blue (B), and each separated color light is separated into a subsequent liquid crystal light. Guide to valves 50r, 50g, 50b.

  More specifically, first, the first dichroic mirror 41a reflects the R illumination light LR out of the three RGB colors and transmits the G and B illumination lights LG and LB. Further, the second dichroic mirror 41b reflects the G illumination light LG of the two colors GB and transmits the B illumination light LB. That is, the red light LR reflected by the first dichroic mirror 41a is guided to the first optical path OP1 with the field lens 43r, is transmitted through the first dichroic mirror 41a, and is reflected by the second dichroic mirror 41b. The green light LG is guided to the second optical path OP2 having the field lens 43g, and the blue light LB having passed through the second dichroic mirror 41b is guided to the third optical path OP3 having the field lens 43b.

  The field lenses 43r, 43g, and 43b for the respective colors are adjusted so that the partial light beams emitted from the second lens array 25 have an appropriate incident angle on the irradiated areas of the liquid crystal light valves 50r, 50g, and 50b. doing.

  The pair of relay lenses 44a and 44b is disposed on a third optical path OP3 that is relatively longer than the first optical path OP1 and the second optical path OP2, and an image formed immediately before the first relay lens 44a on the incident side. By transmitting the light to the field lens 43b on the exit side almost as it is, the light use efficiency is prevented from being lowered due to light diffusion or the like.

  The light modulation unit 50 includes three liquid crystal light valves 50r, 50g, and 50b into which illumination lights LR, LG, and LB of three colors are incident, respectively. Each of the liquid crystal light valves 50r, 50g, and 50b is a non-light-emitting light modulator that modulates the spatial distribution of the intensity of incident illumination light.

  Each of the liquid crystal light valves 50r, 50g, 50b includes a liquid crystal panel 51r, 51g, 51b disposed in the center, and an incident side polarizing filter 52r, 52g, 52b disposed on one light incident side so as to sandwich the liquid crystal panel 51r, 51g, 51b. Emission-side polarizing filters 53r, 53g, and 53b disposed on the other light emission side are provided.

  The liquid crystal panels 51r, 51g, and 51b are not shown in the drawings, but a light-transmitting substrate having a transparent electrode or the like, a light-transmitting driving substrate having a pixel electrode or the like, and between the light-transmitting substrate and the driving substrate. And a liquid crystal layer hermetically sealed.

  Each color light LR, LG, LB incident on each liquid crystal light valve 50r, 50g, 50b is pixel by pixel according to a drive signal or control signal input as an electrical signal to each liquid crystal light valve 50r, 50g, 50b. Intensity modulated.

  The light combining optical system 60 is a cross dichroic prism, has a substantially square shape in plan view in which four right angle prisms are bonded together, and a pair of dichroic mirrors 61 intersecting in an X shape at the interface where the right angle prisms are bonded together. , 62 are formed.

  The pair of dichroic mirrors 61 and 62 are formed of dielectric multilayer films having different characteristics. That is, one dichroic mirror 61 reflects red light LR, and the other dichroic mirror 62 reflects blue light LB.

  The light combining optical system 60 reflects the modulated red light LR from the liquid crystal light valve 50r by the dichroic mirror 61 and emits it in the Z direction by bending the optical path, and modulates the green light LG from the liquid crystal light valve 50g. Is transmitted straight through the dichroic mirrors 61 and 62, and the modulated blue light LB from the liquid crystal light valve 50b is reflected by the dichroic mirror 62 and bent in the optical path to be emitted in the Z direction. On the light emitting side of the light combining optical system 60, the color lights LR, LG, and LB are superimposed to perform color combining.

  The projection optical system 70 includes a projection lens 71 that enlarges and projects the color image light combined by the light combining optical system 60, a lens driving device 72 that operates under the control of the control device 90, and adjusts the state of the projection lens 71. And a temperature sensor 97 for detecting the temperature of the projection lens 71.

  The projection lens 71 is a zoom lens that projects images on the liquid crystal panels 51r, 51g, 51b onto the screen SC at a desired magnification. In addition to a plurality of lens groups 71a that can move in the direction of the optical axis OA, the projection lens 71 includes an iris 71b that can adjust the aperture value by opening and closing operations. Although not shown, the lens driving device 72 includes an actuator, a mechanical mechanism, and the like.

  The lens driving device 72 detects lens information such as the lens shift amount, the projection magnification, and the aperture value of the projection lens 71 by the built-in sensor group 72b, and outputs the detection result to a lens drive control unit 95 described later. At the same time, the lens shift amount, projection magnification, aperture value, and the like of the projection lens 71 can be changed based on a control signal from the lens drive control unit 95. When adjusting the lens shift amount of the projection lens 71, the lens driving device 72 appropriately translates the projection lens 71 from the state where the optical axis OA is on the system optical axis SA along the ± Y direction perpendicular to the optical axis OA. Move.

  Thus, by the lens shift that intentionally shifts the optical axis OA of the projection lens 71 with respect to the system optical axis SA, the projection direction by the projection lens 71 is an oblique direction inclined by a desired angle, for example, in the + Y direction with respect to the optical axis OA. Therefore, it is possible to project an image in a state with little shape distortion at a position shifted in the + Y direction from the system optical axis SA.

  Further, the projection magnification by the projection lens 71 can be changed by individually moving a part of the plurality of lens groups 71a constituting the projection lens 71 in the direction of the optical axis OA.

  The temperature sensor 97 provided so as to accompany the projection lens 71 is formed of a temperature sensitive element such as a thermistor, for example, and its operation is controlled by a detection circuit 96 provided in the control device 90. By the projection optical system 70 described above, a color moving image or a color still image obtained by synthesizing each color image corresponding to the drive signal or display signal input to each liquid crystal panel 51r, 51g, 51b is projected on the screen SC at a desired magnification. Is done.

  The control device 90 includes an image processing unit 91 to which an external image signal (image data) such as a video signal is input, and a panel driving unit that drives the liquid crystal light valves 50r, 50g, and 50b based on the output of the image processing unit 91. 92, a dimming mechanism driving unit 93 that drives the dimming mechanism 31 based on the output of the image processing unit 91, a lighting driving unit 94 that supplies power to the light source device 21 to adjust the lighting state of the arc tube 21a, and a projection A lens drive control unit 95 for adjusting an image forming state by the optical system 70 and a main control unit 99 for comprehensively controlling operations of the circuit portions 91, 94, 95 and the like are provided. The control device 90 operates with power supplied from the power supply device 101.

  The image processing unit 91 can perform various correction processes (image processing) such as luminance correction, color correction, and distortion correction on image data input from outside (hereinafter referred to as “input image data”). In this example, the input image data is composed of RGB version image data, but is not limited thereto.

  The panel drive unit 92 generates a drive signal for adjusting the state of each of the liquid crystal light valves 50r, 50g, and 50b based on the image data after image processing (display data) output from the image processing unit 91. Accordingly, an image as a transmittance distribution can be formed in the liquid crystal light valves 50r, 50g, and 50b corresponding to the display data input from the image processing unit 91.

  The dimming mechanism driving unit 93 dynamically controls the open / closed state of the dimming mechanism 31. The dimming mechanism driving unit 93 causes the dimming mechanism 31 to perform a continuous or stepwise opening / closing operation between a closed state where most of the optical path is blocked and an open state where the optical path is opened. The lighting drive unit 94 adjusts the light emission state of the arc tube 21a by adjusting the voltage and current amplitude and period supplied to the arc tube 21a.

  The lens drive control unit 95 operates the lens drive device 72 appropriately by outputting a control signal to the lens drive device 72, and sets the projection magnification, the lens shift amount, the aperture value, etc. of the projection lens 71 to a desired state. can do.

  The lens drive control unit 95 receives a detection signal from a sensor group 72 b (specifically, a zoom position sensor, a shift sensor, an aperture sensor, etc.) built in the lens driving device 72. Lens information such as the projection magnification, the lens shift amount, and the aperture value is provided to the main control unit 99 as needed. The sensor group 72b described above functions as a detection unit for detecting lens information, which is various information related to projection, together with a temperature sensor 97 provided separately.

  The main control unit 99 operates based on a program appropriately prepared for controlling the image processing unit 91, the lighting drive unit 94, the lens drive control unit 95, and the like. The main control unit 99 operates the lens drive control unit 95 based on a user instruction, data stored therein, and the like, and changes the projection magnification and the lens shift amount of the projection lens 71 to a desired state. At this time, the main control unit 99 monitors, as lens information, the projection magnification detected by the sensor group 72b, the lens shift amount, the aperture value, and the use temperature detected by the temperature sensor 97. The main control unit 99 stores this lens information as information necessary for causing the image processing unit 91 to correct color misregistration and other aberrations. In this example, the control device 90 corresponds to the image processing device of the present invention.

  FIG. 2 is a block diagram illustrating a configuration example of the image processing unit 91. As shown in FIG. 2, the image processing unit 91 includes an MPU 110, a video processor 120, a display buffer 130, a ROM 140, a RAM 150, and an input / output I / F unit 160.

  The MPU 110 reads out a program stored in the ROM 140 or the like and develops and executes the read program on the RAM 150, thereby comprehensively controlling the image processing unit 91. For example, the MPU 110 performs various types of image processing on an externally input image by appropriately operating the video processor 120 or the like.

  The video processor 120 executes various image processing under the control of the MPU 110. The display buffer 130 temporarily stores the image data (display data) that has been subjected to image processing by the video processor 120 for output to the panel drive unit 92 of FIG.

  The ROM 140 stores invariant information (for example, a program, color shift amount data to be described later) for the image processing unit 91 to operate. The RAM 150 is used as a work area for data processing during image processing.

  The input / output I / F unit 160 receives, from the main control unit 99, control signals, projection magnification, lens shift amount, aperture value, operating temperature, and other lens information related to the operation of the image processing unit 91. Further, the input / output I / F unit 160 accepts an input image from the outside. The MPU 110 uses the information received by the input / output I / F unit 160 to perform control for executing image processing on the input image data, and performs control for transmitting display data after image processing to the panel drive unit 92. That is, the image processing unit 91 can also be regarded as functioning as a correction unit that corrects input image data.

  The projector 100 according to the present embodiment can project input image data from the projection lens 71 onto the screen SC by using an optical system as shown in FIG. 1. In general, however, various aberrations (magnification chromatic aberration, Due to the Seidel aberration), the image forming position is shifted in each of the RGB colors. In particular, for light passing through the end of the lens that cannot be approximated by paraxial rays, it is quite difficult to absorb all aberrations by lens design alone. In a proximity optical system in which the screen SC is placed near the projector, it is necessary to use a lot of light passing through the end of the lens, which is more susceptible to aberrations. As a result, a false color that does not exist in the input image data occurs at the edge portion of the projection image, resulting in image quality degradation. In particular, in a character image (including a line drawing), if a false color occurs in the edge area, the sharpness of the image may be extremely reduced.

  Next, specific contents of the video processor 120 will be described with reference to FIG. FIG. 3 is a block diagram illustrating a configuration example of the video processor 120. As shown in FIG. 3, the video processor 120 includes a dot correction unit 121 and an image adjustment unit 122.

  Here, in the video processor 120, color misregistration amount data depending on the projection direction (hereinafter referred to as “color misregistration amount data”) is attached to the input image data received by the input / output I / F unit 160. Entered. The color misregistration data is determined as follows, for example.

  As shown in FIG. 4, the direction (vector direction) in which a specific pixel is projected is uniquely determined according to the position of the input image data. At this time, the light rays flying in the direction of the minute solid angle in the vicinity of each vector direction include various aberrations of the lens, but for all regions (regions in block units including a plurality of pixels) in advance, Measurement is performed for three colors of red (R), green (G), and blue (B) separated by the color separation light guide optical system 40. In this way, data (color misregistration amount data) regarding the color misregistration amount in the main scanning direction and the sub scanning direction as a result of considering all aberrations is experimentally obtained in advance and recorded in the ROM 140 of the image processing unit 91. Keep it.

  Here, the color shift amount data for each projection direction obtained in advance is stored in the ROM 140. However, the present invention is not limited to this. For example, as in the technique described in Japanese Patent No. 3853684, The configuration is such that a test pattern such as a cross hatch is projected onto a screen, the color shift error of the projected image is measured using a CCD camera, the color shift amount at each position is measured, and the measurement result is obtained. May be.

  The dot correction unit 121 in FIG. 3 corrects a color misregistration amount of less than one line out of the color misregistration amounts in the main scanning direction and the sub scanning direction, using the input image data and the color misregistration amount data that are input. . Although the correction method of the color misregistration amount of less than one line is arbitrary, for example, as in the technique described in Japanese Patent No. 3904385, it can be corrected by an interpolation process using a cubic function convolution method or the like. . However, the dot correction unit 121 is not an essential component, and may be configured such that the dot correction unit 121 is not provided, for example.

  In the output image of the dot correction unit 121, it may be considered that color misregistration in units of integer lines has occurred. For example, it is assumed that a color deviation of 2 dots has occurred. FIG. 5 is an image diagram when color misregistration of 2 dots occurs. Here, an example of a line drawing having a width of 6 pixels (0.25 mm at 600 dpi) is shown.

FIG. 5 is an example in which a 2-dot color shift occurs in an ideal green line on a white ground.
In the green line on the white ground, light does not exist in the RB plane among the RGB signals. Therefore, when divided into RGB planes, as shown in FIG. 6, the RB plane is a black line on the white ground, and the G plane is a white image over the entire surface. Here, considering a case where a two-dot color shift has occurred in the RB plane, a cyan and yellow bleed area beside the green line (can also be regarded as a color shift area indicating an area where the color shift occurs). Will occur. As a result, character sharpness is greatly reduced.

  Although it is conceivable to correct this color misregistration region by correcting the geometric position, the main object of the present invention is to make it difficult to visually recognize the blurred portion image by image processing. However, it is not necessarily intended to faithfully reproduce the document, and one object is to accurately transmit character information in a presentation using an image projected on the screen SC. Therefore, it is for business documents and not for photographic images. In general, image data projected by a projector apparatus is rarely a photographic image that requires very fine document reproduction.

  The image adjusting unit 122 illustrated in FIG. 3 performs image processing on the input image data after the correction by the dot correcting unit 121 is performed. This will be specifically described below.

  As illustrated in FIG. 3, the image adjustment unit 122 includes a specifying unit 123 and a gradation correction processing unit 124. The identifying unit 123 identifies a target image in which color misregistration occurs among images included in the input image data, using color misregistration amount data that depends on the projection direction of the input image data. The gradation correction processing unit 124 performs gradation correction processing so that the visibility of the first area indicating the area where color misregistration occurs in the target image is reduced. In the present embodiment, the gradation correction processing unit 124 contrasts (bright) the first region and the second region indicating a region in which no color shift occurs in the target image so that the visibility of the first region is reduced. Contrast adjustment processing (an example of gradation correction processing) for adjusting the difference in brightness between the dark portion and the dark portion is performed.

  FIG. 7 is a flowchart illustrating an example of processing performed by the image adjustment unit 122. The image adjustment unit 122 executes the process of FIG. 7 for each image included in the input image data (for each object to be projected). Hereinafter, specific contents will be described with reference to FIG.

  As shown in FIG. 7, first, the specifying unit 123 determines whether or not the attribute of the object to be projected indicates a character image (including a line drawing) (step S1). An attribute can be regarded as information indicating the type of image. For example, if the input image data is information input from a PC, it can be determined whether or not the attribute of the object indicates a character image depending on whether or not the object to be projected is text. In addition, a known image area separation technique may be used.

  If the object attribute does not indicate a character image (result of step S1: NO), the process ends. On the other hand, when the attribute of the object indicates a character image (result of step S1: YES), the process proceeds to step S2. As described above, the present invention does not necessarily intend to faithfully reproduce a document. Therefore, for example, when an object attribute indicates a photographic image, the object is excluded and no processing is performed.

  In step S2, the specifying unit 123 determines whether or not the object whose attribute is determined to indicate a character image in step S1 is a single color character image (step S2). Here, a single-color character image is defined as a character image that does not affect the final image quality even if there is a color shift. For example, it is determined that the green character on the white ground as shown in FIG. 5 is not a single color character image. On the other hand, for example, in the case of a cyan character on the ground, there is no R plane light in the character portion, and the G and B planes are white images over the entire surface. Accordingly, since the color shift does not affect the final image quality, it is determined that the character image is a single color.

  Further, for example, in the case of a green character on the black ground, light is projected onto the character portion only in the G plane, so that it is determined that the character image is a single color. Thus, the determination of a single color character is switched depending on the combination of the background color and the character color. Here, in order to comprehensively process all combinations, the specifying unit 123 performs edge extraction with character edges for each of the RGB planes constituting the input image data. If there is an edge amount equal to or greater than a predetermined value in only a single plane, it is determined that the character image is a single color.

  FIG. 8A is a diagram showing the edge amounts of the RGB planes when edge extraction is performed with green characters on the ground. More specifically, FIG. 8A shows a change in edge amount when the edge of the image in FIG. 6 is extracted in the main scanning direction (horizontal direction in FIG. 6). As shown in FIG. 8A, since there is an edge amount that is greater than or equal to a predetermined amount in each of the R plane and the B plane, in this case, the specifying unit 123 determines that the character image is not a single color. To do.

  FIG. 8B is a diagram showing the edge amounts of the RGB planes when edge extraction is performed with cyan characters on the white ground. As shown in FIG. 8B, since there is an edge amount equal to or larger than a predetermined amount only in the R plane, in this case, the specifying unit 123 determines that the character image is a single color.

  As described above, when it is determined that the object whose attribute is determined to indicate a character image in step S1 is a single color character image (result of step S2: YES), the process ends. On the other hand, if it is determined that the object whose attribute is determined to indicate a character image in step S1 is not a single color character image (result of step S2: NO), the process proceeds to step S3.

  In step S3, the specifying unit 123 refers to the color misregistration amount data and determines whether or not the object is an image in which color misregistration occurs. When it is determined that the object is an image in which color misregistration occurs (result of step S3: YES), the specifying unit 123 sets the object as a target image to be subjected to gradation correction processing by the gradation correction processing unit 124. As specified. In this case, the specifying unit 123 refers to the color misregistration amount data, and includes a first area indicating a region where color misregistration occurs in the target image, and a second area indicating a region where no color misregistration occurs in the target image. Is identified. Then, the process proceeds to step S4.

  On the other hand, when it is determined that the object is not an image in which color misregistration occurs (result of step S3: NO), the specifying unit 123 does not specify the object as a target image, and the process ends. . In other words, the specifying unit 123 selects any of the case where the attribute of the object does not indicate a character image, the case where the object is not a single color character image, and the case where the object is an image in which no color shift occurs. If this is the case, since the object is not specified as the target image, gradation correction processing is not performed on the object.

  In step S4, the gradation correction processing unit 124 determines whether or not the line width of the target image (character image) specified by the specifying unit 123 is greater than or equal to a predetermined threshold value. If it is determined that the line width of the target image is equal to or greater than the threshold (result of step S4: YES), the process proceeds to step S5.

  In step S5, the gradation correction processing unit 124 does not cause color misregistration between the first region and the target image so that the visibility of the first region indicating the region where color misregistration occurs in the target image is reduced. Contrast adjustment processing for adjusting the contrast with the second region indicating the region is performed. More specifically, when the density value near the outside of the first area (outside the character image) is lower than a predetermined value, the gradation correction processing unit 124 performs the density of the first area by γ conversion. In the meantime, a process of increasing the density of the second region by γ conversion is performed. On the other hand, when the density value near the outside of the first area is higher than a predetermined value, the gradation correction processing unit 124 performs the process of increasing the density of the first area by γ conversion, while by the γ conversion. Processing for reducing the density of the second region is performed.

  By performing the contrast adjustment process as described above, as shown in FIG. 9, the visibility of color misregistration is reduced, and thus the visibility of characters is improved. In addition, the sharpness of the characters also increases, and the character information in the presentation is smoothly transmitted.

  10 is projected onto the screen SC with the reflectance of the image data projected on the screen SC as the vertical axis and the horizontal position in FIG. 5 as the horizontal axis for the cross section in the horizontal direction (horizontal direction) in FIG. It is a figure which shows the relationship between the reflectance of the obtained image data, and the position of the horizontal direction of FIG. FIG. 10A is a diagram illustrating a state before the above-described contrast adjustment processing is performed, and FIG. 10B is a diagram illustrating a state after the above-described contrast adjustment is performed.

  On the other hand, for example, if color misregistration occurs in a character image whose line width is less than the threshold value, the character area may entirely overlap with the color misregistration area. In this case, if the above-described contrast adjustment process is not performed, the visibility of characters is significantly deteriorated. However, when the above-described contrast adjustment process is performed, the density is increased in order to improve the contrast. There is no second region to be changed, and the processing is merely to change the density of the first region. In other words, the processing is such that the character image becomes thin as a whole.

  Therefore, in this embodiment, when it is determined that the line width of the target image (character image) is less than the threshold (result of step S4 in FIG. 7: NO), the gradation correction processing unit 124 determines that the target image is A character color conversion process (an example of a gradation correction process) for converting a character image of a single color is performed (step S6 in FIG. 7). More specifically, the gradation correction processing unit 124 performs edge extraction for each RGB plane. Then, among the RGB planes, the pixel value (density value) of each pixel of the plane with the largest edge amount is left as it is, and the pixel value of each pixel is set so that the edge amount is equal to or less than the reference value for the other planes. Convert. In the present embodiment, the gradation correction processing unit 124 keeps the pixel value (density value) of each pixel of the plane with the largest edge amount among the RGB planes, and the edge amount becomes 0 for the other planes. Thus, the pixel value of each pixel is converted.

  As described above, the target image whose line width is less than the threshold value is converted to a character image of a single color, so that it is possible to prevent the image quality of the object projected on the screen SC from deteriorating.

  As described above, in the present embodiment, the gradation correction processing unit 124 includes the first region (region near the edge) where color misregistration occurs in the character image (target image) specified by the specifying unit 123. Since the contrast adjustment processing is performed to adjust the contrast between the first area and the second area where no color shift occurs in the character image (the area inside the vicinity of the edge) so as to reduce the visibility, There are advantageous effects that the visibility is lowered and the visibility of the characters is improved. When the line width of the character image specified by the specifying unit 123 is less than the threshold, the gradation correction processing unit 124 converts the character image into a single color character image instead of performing contrast adjustment processing on the character image. Since the character color conversion process for conversion is performed, it is possible to prevent the final image quality from being affected by the color shift.

(Modification)
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.

  For example, when performing the above-described contrast adjustment processing, the gradation correction processing unit 124 can change the contrast adjustment amount according to the color misregistration amount. That is, the gradation correction processing unit 124 can also perform contrast adjustment processing such that the greater the color misregistration amount (the greater the color misregistration level), the greater the contrast between the first region and the second region. .

  When the color misregistration amount is large, it is difficult to smoothly transmit the character information unless the contrast adjustment process is performed so that the contrast between the first region and the second region is increased. It is preferable to perform contrast adjustment processing so that the contrast between the first region and the second region is increased. As the contrast between the first area and the second area increases, it becomes difficult to faithfully reproduce the original, but in exchange for this, the sharpness of the characters increases, and the character information is smoothly transmitted.

  FIG. 11A is a diagram illustrating an example in which the amount of color misregistration is larger than that in FIG. In this case, the gradation correction processing unit 124 ensures that the relationship between the reflectance of the image data projected on the screen SC and the horizontal position in FIG. 5 is the relationship shown in FIG. By performing the contrast adjustment process, the visibility of color misregistration is reduced and the sharpness of characters is improved. Therefore, it becomes possible to smoothly transmit the character information.

  In the above-described embodiment, among the images included in the input image data, an image whose attribute indicates a photographic image is not a target of processing by the gradation correction processing unit 124, but is not limited thereto. For example, among the images included in the input image data, color misregistration occurs and an image whose attribute indicates a photographic image is specified as the target image, and the visibility of the first region where the color misregistration of the target image occurs is reduced. Thus, a configuration in which contrast adjustment processing is performed may be employed.

  In short, as an embodiment of the present invention, an image in which color misregistration occurs among images included in input image data is specified as a target image, and the visibility of a first region indicating a region in which color misregistration occurs in the target image. As long as gradation correction processing (contrast adjustment processing as an example) is performed so that the image quality decreases.

(program)
Note that the image processing apparatus according to the present invention can be applied to a system including a plurality of devices (for example, a host computer, an interface device, a scanner, a printer, and the like). ) May be applied.

  Another object of the present invention is to supply a recording medium recording a program code of software for realizing the functions of the above-described image processing apparatus to the system or apparatus, and the computer of the system or apparatus (or CPU, MPU, It can also be achieved by the DSP) executing the program code stored in the recording medium. In this case, the program code itself read from the recording medium realizes the function of the above-described image processing apparatus, and the program code or the recording medium storing the program constitutes the recording medium of the present invention. become. Recording media for supplying the program code include FD, hard disk, optical disk, magneto-optical disk, CD-ROM, CD-R, magnetic tape, non-volatile memory, optical recording medium such as ROM, magnetic recording medium, optical Magnetic recording media and semiconductor recording media can be used.

  Further, by executing the program code read by the computer, not only the functions of the image processing apparatus described above are realized, but also an OS (operating system) operating on the computer based on the instruction of the program code. However, it is needless to say that a case where the function of the above-described image processing apparatus is realized by performing part or all of the actual processing.

  In addition, after the program code read from the recording medium is written in a memory provided in a function expansion board inserted in the computer or a function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program code. It goes without saying that the CPU or the like provided in the board or the function expansion unit performs part or all of the actual processing and the functions of the above-described image processing apparatus are realized by the processing.

  Furthermore, the software that realizes the functions of the above-described image processing apparatus may be configured to be provided by being stored on a computer connected to a network such as the Internet and downloaded via the network. The software that realizes the functions of the above-described image processing apparatus may be provided or distributed via a network such as the Internet.

DESCRIPTION OF SYMBOLS 10 Optical system part 90 Control apparatus 91 Image processing part 100 Projector 101 Power supply apparatus 110 MPU
120 Video processor 121 Dot correction unit 122 Image adjustment unit 123 Identification unit 124 Tone correction processing unit 130 Display buffer 140 ROM
150 RAM
160 Input / output I / F section

JP 2010-219683 A

Claims (13)

Using a color shift amount that depends on the projection direction of input image data input from an external device, a specifying unit that specifies a target image in which color shift occurs among images included in the input image data;
A gradation correction processing unit that performs gradation correction processing so that the visibility of a first region indicating a region where color misregistration occurs in the target image is reduced.
Image processing device. The specifying unit specifies, as the target image, an image in which color misregistration occurs and an attribute indicating a type of image is a character image among images included in the input image data.
The image processing apparatus according to claim 1. The gradation correction processing unit adjusts a contrast between the first region and a second region indicating a region in which no color shift occurs in the target image so that the visibility of the first region is lowered. Perform the adjustment process,
The image processing apparatus according to claim 1. When the density value in the vicinity of the outside of the first area is lower than a predetermined value, the gradation correction processing unit reduces the density value of the first area and sets the density value of the second area. By increasing the contrast, the contrast between the first region and the second region is adjusted.
The image processing apparatus according to claim 3. The gradation correction processing unit increases the density value of the first area and decreases the density value of the second area when the density value near the outside of the first area is higher than a predetermined value. By adjusting the contrast between the first region and the second region,
The image processing apparatus according to claim 3. The gradation correction processing unit performs the contrast adjustment process when the line width of the target image is equal to or greater than a threshold value, and does not perform the contrast adjustment process when the line width of the target image is less than the threshold value. ,
The image processing apparatus according to claim 3. When the line width of the target image is less than the threshold value, the gradation correction processing unit performs a process of converting the target image into a single color character image.
The image processing apparatus according to claim 6. The gradation correction processing unit leaves the pixel value of the plane image having the largest edge amount out of the plurality of plane images constituting the input image data, and the edge amount is equal to or less than a reference value for the other plane images. Convert the pixel values to be
The image processing apparatus according to claim 7. The specifying unit may include any one of the plurality of plane images constituting the input image data, even if the attribute indicates a character image among the images included in the input image data. In the case where only an edge amount equal to or greater than a predetermined value is extracted, the image is not specified as the target image.
The image processing apparatus according to claim 2. The gradation correction processing unit performs the contrast adjustment processing so that the contrast between the first region and the second region increases as the degree of color misregistration increases.
The image processing apparatus according to claim 3. An image processing apparatus according to any one of claims 1 to 10, and a projection unit that projects image data on which image processing has been performed by the image processing apparatus onto a screen.
Image projection device. A specifying step for specifying a target image in which color misregistration occurs among images included in the input image data using an amount of color misregistration that depends on a projection direction of input image data input from an external device;
A program for causing a computer to execute a gradation correction processing step for performing gradation correction processing so that visibility of a first area indicating an area where color misregistration occurs in the target image is reduced.   A recording medium for storing the program according to claim 12.

Images