JP2019075688A - Image projection device, control method thereof and program - Google Patents

Abstract

An object of the present invention is to easily and highly accurately align an image to be projected with respect to a printed matter. An image projection apparatus (100) includes a projection unit (106) for projecting a projection image (120) on the back surface of a printed material (110), an image shift between a printed image (111) formed on the front surface of the printed material (110) and the projected image (120), and an image shift between the printed image (111) and the projected image (120). A misalignment detection unit 102 that detects printing misalignment with the position marker 211 on the back surface of the printed matter 110, a misalignment correction unit 103 that corrects the projected image 120 based on the image misalignment, and a projection unit 106 projected image 120 based on the printing misalignment. and an overall control unit 108 that corrects the projected position of the image onto the printed matter 110 . [Selection drawing] Fig. 1

Description

  The present invention relates to an image projection apparatus, a control method thereof, and a program.

  In recent years, the opportunity to describe a subject photographed with a digital camera or the like as a high dynamic range image (hereinafter referred to as “HDR image”) has increased. If the HDR image can be reproduced faithfully to human vision, the expressive power of colors, gradations, textures, etc. can be enhanced, and a strong impact can be given to the viewer.

Here, in direct-viewing type devices such as liquid crystal displays and organic EL displays, the display ability is improved, but the reproduction range thereof is generally about 1 to 1000 cd / m ² . Therefore, in order to reproduce, for example, an HDR image exceeding 1000 cd / m ² with these direct view devices, it is necessary to perform tone compression processing called tone mapping. In that case, the dynamic range originally possessed by the HDR image can not be sufficiently expressed. In addition, while a projection apparatus such as a projector has high white luminance, it projects a small amount of light in black display, resulting in a decrease in contrast ratio. In particular, as the projection brightness becomes bright, the black brightness rises, and so-called black floating occurs. Printed matter obtained by printing an image on a printing medium such as paper using a printer etc. does not cause black floating as occurs with a projection device, but it is not possible to obtain brightness more than illumination light, so a sufficient dynamic range Can not be obtained.

  Therefore, for the purpose of expanding the dynamic range of the luminance and the color gamut, there has been proposed a technique for improving the contrast by projecting an image on a printed material with a projection device (for example, see Patent Document 1). In the technology described in Patent Document 1, the contrast of the object to be observed is improved by projecting the image on the object to be observed such as a printed matter so as to overlap the object to be observed. In addition, when projecting an image onto the screen from the back side of the screen, there is known a technique for aligning the projection position of the image with the screen by matching the positions of the four corners of the screen with the projection positions of the image (for example, Reference 2).

Unexamined-Japanese-Patent No. 2007-334179 JP, 2006-251604, A

  Printed matter is often distorted. Therefore, when projecting an image onto a print by a projection device, it is necessary to provide a reference point (marker) for alignment on the image area of the print in order to correct the influence of distortion of the print. Become. In the case of projecting an image from the back side of the printed matter (the side opposite to the side on which the image is printed), it is necessary to recognize the image printed on the printed matter from the back side of the printed matter. That is, it is necessary to recognize the content of the image of the printed matter using light passing through the printed matter.

  However, when the ambient light on the surface of the print (surface on which the image is printed) is low, the thickness of the print (print medium (such as paper)) is small. When the light intensity is dark, etc., transmitted light with a sufficient amount of light may not be obtained. In such a case, it is difficult to recognize the content of the front side of the printed matter from the back side of the printed matter, which makes it difficult to align the image to be projected onto the printed matter.

  One possible solution to this problem is to print a marker on the back of the print. However, due to the paper feeding accuracy of the printing apparatus, the print position on the front and back sides of the printed matter may be offset by millimeter. Therefore, even if alignment is performed using a marker printed on the back side of the printed matter, it is not always possible to reliably position the image to be projected onto the printed matter.

  An object of the present invention is to provide an image projection apparatus capable of easily and precisely aligning an image to be projected with respect to a print when projecting an image onto the print from the back side of the print.

  An image projection apparatus according to the present invention comprises: projection means for projecting a projection image on the back side of a printed matter; and first detection means for detecting an image deviation between a print image formed on the front side of the printed matter and the projection image. A second detection unit that detects a shift between the print image and a predetermined position on the back surface of the printed matter as a print shift, a correction unit that corrects the projected image based on the image shift, and the print shift And control means for correcting the projection position of the projection image on the printed matter by the projection means.

  According to the present invention, when projecting an image from the back side of a print, the image to be projected can be easily aligned with high precision to the print.

It is a figure explaining an example of outline composition and a picture projection form of a picture projection device concerning a 1st embodiment. It is a figure explaining a printed matter, a projection image, and an appreciation picture. It is a flowchart which shows the image projection processing procedure by an image projector. It is a figure explaining the process which detects the positional offset of a position marker. It is a figure explaining the process which detects the shift | offset | difference of the surface and back surface in printed matter. It is a figure showing an example of exhibition of printed matter. It is a block diagram which shows schematic structure of the image projection system which concerns on 2nd Embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. First, a first embodiment of the present invention will be described. FIG. 1A is a block diagram showing a schematic configuration of an image projection apparatus 100 according to the first embodiment of the present invention. FIG. 1B is a plan view (front view) of a printed material 110 which is an object of image projection by the image projection apparatus 100. FIG. 1C is a view schematically showing a state in which the image projection apparatus 100 projects an image onto the printed material 110 from the back surface side of the printed material 110.

  The printed matter 110 is an image formed (printed) on one side of a printing medium such as paper or film. In the following description, an image printed (formed) on the printed matter 110 is referred to as a “printed image”. Further, the surface on which the print image 111 is formed is defined as “the surface of the print 110”, and the surface on which the print image 111 is not formed (the surface opposite to the surface on which the print image 111 is formed) is “print It defines as "the back of 110". Then, an image projected from the image projection device 100 to the printed matter 110 is referred to as a “projected image”.

  The image projection apparatus 100 includes an imaging unit 101, a shift detection unit 102, a shift correction unit 103, an image input unit 104, a communication unit 105, a projection unit 106, a UI unit 107, and an overall control unit 108. The overall control unit 108 includes a CPU, a ROM for storing a program executed by the CPU, a RAM having an area for storing calculation results and parameters used by the CPU for calculation, and an area for expanding a program. The general control unit 108 controls the overall operation of the image projection apparatus 100 by the CPU expanding the program stored in the ROM into the RAM and controlling the operation of each unit of the image projection apparatus 100. In FIG. 1A, the connection between the overall control unit 108 and each unit is omitted.

  The imaging unit 101 (first imaging unit) includes a lens and an imaging sensor such as a CCD sensor or a CMOS sensor, and an image processing circuit that converts an electrical signal output from the imaging sensor into image data. The shift detection unit 102 includes an image (hereinafter referred to as “input image”) input to the shift detection unit 102 and the shift correction unit 103 via the image input unit 104 and an image captured by the imaging unit 101 (hereinafter referred to as “captured Obtain an image. Then, the shift detection unit 102 detects the shift amount between the projection image 120 (see FIG. 2) and the print image 111 from the information attached to the input image and the photographed image.

  The shift correction unit 103 creates a shift correction value of the projection image 120 based on the shift amount detected by the shift detection unit 102, and creates a corrected image. Examples of the processing performed by the deviation correction unit 103 include keystone (trapezoidal correction) processing and warping processing, but are not limited to these. The warping process is a process of specifying a feature point on an image and generating a new image by specifying the movement amount of the specified feature point. The shift detection unit 102 and the shift correction unit 103 are each configured by an arithmetic device such as a microcomputer, and the above-described function is realized by a combination of hardware and software.

  The image input unit 104 includes terminals of a communication standard such as HDMI (registered trademark) and DisplayPort (registered trademark), a processing circuit thereof, and the like, and has a role of capturing images and video data from an external device. In addition, the image input unit 104 sends information on an image or video data acquired from an external device and a marker attached thereto as metadata to the deviation correction unit 103. Furthermore, the image input unit 104 sends information on the marker to the deviation detection unit 102. The details of the marker will be described later with reference to FIG. The communication unit 105 (first communication unit) is constituted by terminals of a communication standard such as USB (registered trademark), LAN, wireless LAN, etc. and its processing circuit, and the like. Send to

  The projection unit 106 includes a light source such as an LED or a halogen lamp, an optical element such as a prism or a mirror, a display panel such as a liquid crystal panel or a liquid crystal on silicon (LCOS) panel, and a projection lens. In the present embodiment, the projection unit 106 projects an image on the back surface of the printed matter 110. The UI unit 107 includes an input unit such as a button, a mouse, and a remote controller, a display device, and the like, receives an input by a user operation, and notifies a user or saves setting values in items set by the user. I do.

  As shown in FIG. 1C, the viewer views the print 110 from the front side of the print 110. At that time, the user's eyes see the back surface side of the printed matter 110 among the light reflected by the light such as illumination reflected on the surface of the print image 111 and the light projected by the image projection apparatus 100 (that is, the projection image 120). The light in which the transmitted light transmitted to the side is superimposed is incident. As a result, the user can view the print image 111 (hereinafter referred to as a "view image") whose dynamic range is expanded.

  Next, the relationship between the print image 111 of the print 110 and the projection image 120 will be described. FIG. 2A is a view showing the surface of the printed matter 110. A print image 111 is printed at the center of paper (print medium), and a margin is provided around the print image 111. Table markers 201 are printed at the four corners of the margin. The front marker 201 is used to correct a printing deviation between the print image 111 on the front surface of the printed material 110 and the position marker 211 (see FIG. 2B) printed on the back surface of the printed material 110. The front marker 201 can be viewed from the back side of the printed matter 110 by the transmitted light transmitted from the front side to the back side of the printed matter 110. Therefore, it is desirable that the printing of the front marker 201 have a characteristic (for example, dark color or thick) that facilitates recognition from the back side. In addition, although the front marker 201 is made into cross shape here, the shape of the front marker 201 is not restricted to this, For example, arbitrary shapes, such as a polygon and a circle, can be used.

  FIG. 2 (b) is a view showing the back surface of the printed matter 110. A plurality of position markers 211 are printed in an area corresponding to the print image 111 on the back surface of the printed matter 110. Here, three in the vertical direction (direction parallel to the short side) and the horizontal direction (parallel to the long side) Total of 12 position markers 211 are printed. The position marker 211 is used to align the position where the projection image 120 is projected. Although the number of position markers 211 is not limited to twelve, it is preferable that a plurality of position markers 211 be formed from the viewpoint of correcting the projection image 120.

  Each position of the front marker 201 and the position marker 211 is associated with the print image 111. Then, position information of each of the front marker 201 and the position marker 211 and information indicating a relative positional relationship are attached to the input image as metadata. Therefore, as described later, by applying the position information of the markers attached to the input image to the positional relationship between the position marker 211 detected from the back side of the printed matter 110 and the front marker 201, the front marker for the position marker 211 The positional deviation of 201 can be detected. That is, the deviation between the back surface and the front surface of the print medium in the printed material 110 can be detected.

  The position marker 211 is recognized from the back side of the printed matter 110 by the reflected light reflected by the back side of the printed matter 110. On the other hand, the projection light of the projection image 120 is transmitted from the back side to the front side of the print 110 and recognized by the viewer from the front side of the print 110. At that time, since the light passing through the position marker 211 is also transmitted to the surface side of the printed matter 110, it is necessary to prevent the position marker 211 from appearing in the viewing image. Therefore, it is desirable that the position marker 211 has a characteristic (for example, light color or thin) which is difficult to be recognized from the surface side of the printed matter 110, compared with the surrounding area (print medium (paper) base). It is sufficient if there is a recognizable degree of contrast. In addition, although the position marker 211 is set as X mark here, the shape of the position marker 211 is not restricted to this, For example, arbitrary shapes, such as a polygon and a circle, can be used.

  FIG. 2C shows the projection image 120. As shown in FIG. Since the projected image 120 is superimposed on the print image 111, the relative position of the object in the image is the same, but the image is symmetrical with the print image 111. FIG. 2D is a view showing a viewing image 230 viewed by the viewer from the front side of the printed material 110 in which the projection image 120 is superimposed on the printing image 111. Here, it is assumed that the projection image 120 is ideally superimposed on the print image 111. The viewer recognizes the viewing image 230 as one picture in which the projection image 120 is superimposed on the print image 111. Since the print image 111 and the projection image 120 only need to be formed as a picture in a superimposed state, the pixel values of the pixels at the overlapping positions of the print image 111 and the projection image 120 do not have to be the same.

  FIG. 3 is a flowchart showing an image projection processing procedure by the image projection apparatus 100. In each step of the flowchart of FIG. 3, the CPU controls the overall operation of each part of the image projection apparatus 100 by the CPU developing the program stored in the ROM in the RAM in the general control unit 108. Is realized by In addition, it is assumed that an input image is sent to the deviation detection unit 102 and the deviation correction unit 103 via the image input unit 104 in advance. Here, when projected onto the back surface of the print 110, it is assumed that a position marker corresponding to the position marker 211 which is in an original positional relationship independent of distortion of the print 110 is projected. Then, the printed matter 110 is installed at a predetermined position.

  In step S301, the general control unit 108 performs keystone processing by the deviation correction unit 103 so that the longitudinal direction and the lateral direction of the projection image 120 are parallel to the longitudinal direction and the lateral direction of the printed matter 110, respectively.

  Steps S302 to S304 are processing for detecting an image shift between the print image 111 formed on the surface of the print 110 and the projection image 120 projected onto the print 110 from the projection unit 106, and correcting the image shift. First, in step S302, the overall control unit 108 causes the projection unit 106 to project the input image on the back surface of the print 110, and a position marker (hereinafter referred to as a “projection position marker”) corresponding to the position marker 211 is the back surface of the print 110 Project to That is, the input image here is an image for projecting the projection position marker onto the print 110.

  In step S303, the overall control unit 108 causes the imaging unit 101 to capture the back side of the printed matter 110. As a result, an image in which the position marker 211 printed on the back surface of the printed matter 110 and the projection position marker projected in step S302 by the projection unit 106 are captured is photographed. When the printed matter 110 is photographed obliquely, since the photographed image is trapezoidal, keystone processing is performed as necessary.

  In step S304, the overall control unit 108 causes the shift detection unit 102 to shift the positional shift amount for each predetermined area based on the photographed image acquired in step S303 and the position information of the projection position marker attached as metadata to the input image. Detect Here, the position (coordinates) of the projection position marker in the input image is known from the position information of the projection position marker attached to the input image. The shift detection unit 102 calculates where on the back surface of the print 110 the projection position marker is located when the projection position marker is projected on the back surface of the print 110 by performing keystone correction. Then, the shift detection unit 102 calculates the shift amount between the position of the projection position marker in the photographed image and the position of the position marker 211 of the printed material 110 for each of the vertical direction and the horizontal direction.

  The process of step S304 will be specifically described with reference to FIG. FIG. 4A is a view for explaining the relationship between the position marker 211 printed on the back surface of the printed matter 110 and the divided area. Here, divided areas of equal area are set around the position marker 211. That is, one divided area includes one position marker 211, and three equal divided areas in the longitudinal direction and four in the horizontal direction are provided in total. FIG. 4B is an example of the photographed image acquired in step S303. The projected position marker based on the projection of the input image is photographed so as to be superimposed on the position marker 211 printed on the back surface of the printed matter 110, and it can be seen that there is a divided area which is different from the divided area where both overlap. Since the metadata of the input image includes the position information of the projection position marker, the shift amount of the position marker 211 printed on the back surface of the printed material 110 from the projection position marker can be obtained. FIG. 4C shows an example calculated from the number of pixels of the positional deviation amount for each divided area, and the numerical value on the left in parentheses is the deviation in the horizontal direction, and the numerical value on the right in the parentheses is the deviation in the vertical direction Respectively. The shift correction unit 103 generates a shift correction value of the projection image 120 from the shift amount calculated by the shift detection unit 102, and generates a corrected image by warping the projection image 120 using the generated shift correction amount.

  Steps S305 to S306 detect positional deviation between the print image 111 on the front surface of the print 110 and a predetermined position on the back surface of the print 110 (that is, the position marker 211), and the projection image 120 from the projection unit 106 to the print 110 is detected. It is a process of correcting the projection position. In step S305, the overall control unit 108 causes the imaging unit 101 to capture the back side of the printed matter 110. Thereby, the position marker 211 on the back surface of the printed matter 110 is photographed, and the front marker 201 is photographed by the transmitted light transmitted from the front side to the back side of the printed matter 110. In addition, since it becomes difficult to visually recognize the front marker 201 if there is light (reflected light on the back surface) irradiated on the back surface of the printed matter 110, the projection unit 106 emits light while the process of step S305 is performed. It is maintained in a non-projecting state.

  In step S306, the overall control unit 108 corrects the projection position of the projected image 120 based on the print displacement amount calculated by the displacement correction unit 103 after the print displacement amounts of the front and back surfaces of the printed material 110 are calculated by the displacement detection unit 102. Do. The process of calculating the printing deviation amount by the deviation detection unit 102 in step S306 will be specifically described with reference to FIG. FIG. 5A shows an example of the photographed image acquired in step S305. In FIG. 5 (a), the x mark is a position marker 211 printed on the back surface of the print 110, and the cross is printed on the front surface of the print 110 (the back side of the print 110 is seen through the print medium of the print 110). (See from above) is a front marker 201.

  FIG. 5B is a view for explaining a method of calculating the deviation between the front surface and the back surface of the printed matter 110. The front marker 201 is shown by a gray cross in FIG. 5 (b), and its position is the same as FIG. 5 (a). On the other hand, the position of the front marker relative to the position marker 211 can be calculated from the position information of the front marker 201 attached to the input image and the position information of the position marker 211. As a result, the position of the black cross is obtained. It shall be. For each of the four front markers 201, the shift amount between the gray cross and the black cross is calculated for each of the horizontal direction and the vertical direction, and the average value of the calculated shift amounts is calculated. The amount of displacement between the front and back surfaces. It can be seen that FIG. 5B shows a state in which the back surface is shifted to the lower right as a whole with respect to the front surface of the printed matter 110.

  The correction of the projection position of the projected image 120 by the shift correction unit 103 in step S306 is performed based on the shift amount between the front surface and the back surface of the printed material 110 calculated by the shift detection unit 102. At that time, considering the characteristics of the printed image, it is considered that while the front and back surfaces may be misaligned by millimeter due to paper feeding or the like, the printing deviation in the same plane is very small. Therefore, in the present embodiment, the projection position of the projection image 120 is entirely shifted by the amount of deviation between the front surface and the back surface of the printed material 110. In the example of FIG. 5, the projection position of the projection image 120 generated in step S304 may be generally shifted to the upper left by the calculated deviation amount.

  In step S307, the overall control unit 108 causes the projection unit 106 to shift the corrected image (corrected projected image 120) generated in step S304 by the shift amount calculated in step S306 and project it on the back surface of the printed material 110. A viewing image 230 is generated on the After executing step S307, the overall control unit 108 ends the present process.

  FIG. 6 is a view showing an example of display of the printed matter 110. As shown in FIG. Here, a scene in which the printed matter 110 is set in the frame 600 and displayed is assumed, and the viewing image 230 appears to the viewer as shown in FIG. At this time, since the front marker 201 (not shown) is hidden by the frame 600, there is no sense of disturbing viewing. The back surface of the printed matter 110 is as shown in FIG. If the back side of the frame 600 is made of a material that easily reflects light (visible light) such as white, it is possible to recognize the front marker 201 (not shown) from the back side of the printed matter 110 even with the frame 600. It is.

  In the present embodiment, the form in which the front marker 201 is printed in the margin of the outer periphery of the print image 111 has been described, but even if the front marker 201 is printed at a position where it is not noticeable in the area of the print image 111. Good. Further, for example, by simultaneously photographing the front marker 201 at the time of photographing of the position marker 211 in step S304, alignment and correction of the projected image 120 with respect to the position marker 211 and correction of the front and back of the printed matter 110 are simultaneously performed. You may do so. Furthermore, in the present embodiment, the amount of displacement of the front and back surfaces of the printed matter 110 is performed using the front marker 201 and the position marker 211 and the position information of the input image, but the amount of displacement of the front and back surfaces of the printed matter 110 is If known, the value may be input from the outside and used. For example, the projection position of the projected image 120 may be corrected by acquiring the amount of deviation between the front surface and the back surface of the printed material 110 by an apparatus such as a scanner and inputting the acquired value through the communication unit 105 or the UI unit 107.

  As described above, according to the present embodiment, the displacement between the print image and the projection image is corrected using the position marker formed on the back surface of the print, and the front surface of the print is used to form the print Correct the offset between the front and back. Thereby, when projecting an image from the back side of a printed matter, it is possible to easily match and project the projected image with high accuracy to the print image, and it is possible to generate a high-quality viewing image.

  Next, a second embodiment of the present invention will be described. In the present embodiment, an image for correcting a projected image is captured from the front side of a printed material using an external imaging device. FIG. 7 is a block diagram showing a schematic configuration of an image projection system having an image projection device 700 and an imaging device 750 according to the second embodiment. In FIG. 7, the same components as those of the image projection apparatus 100 among the components of the image projection apparatus 700 are denoted by the same names and the same reference numerals, and redundant description thereof will be omitted.

  The image projection device 700 differs from the image projection device 100 in that predetermined data (data acquired from the imaging device 750) is transmitted from the communication unit 105 to the shift detection unit 102, but the other configuration is the same as the image projection device 100. is there. The imaging device 750 is a device independent of the image projection device 700, and includes an imaging unit 751 (second imaging unit) and a communication unit 752 (second communication unit). The imaging unit 751 has the same configuration as the imaging unit 101, the communication unit 752 has the same configuration as the communication unit 105, and communication can be performed between the communication unit 752 and the communication unit 105. The printed matter 110 to be projected of the image from the image projection device 700 is the same as that shown in FIGS. 2A and 2B, and the projected image 120 projected on the printed matter 110 is shown in FIG. It is assumed that it is the same as that shown in.

  The procedure of projecting an image onto the printed material 110 by the image projecting device 700 is basically the same as the procedure in the image projecting device 100 described with reference to the flowchart of FIG. Is different. Therefore, here, only the method of the photographing process of the front marker will be described, and the description of the other processes (S301 to S304, S306 to S307) will be omitted.

  In step S305, the overall control unit 108 causes the UI unit 107 to display a message prompting the user to shoot the front marker 201 using the imaging device 750. Further, the overall control unit 108 acquires an image for projecting the front marker onto the printed matter 110 from the image input unit 104, and the projection unit 106 projects the front marker as an image on the back surface of the printed matter 110. When the user captures an image of the front surface of the print 110 from the front side of the print 110 using the imaging device 750 according to the display, the print medium of the print 110 is projected on the front marker 201 printed on the print 110 and the back of the print 110. Two of the transparent front markers are taken simultaneously. The image thus taken is transmitted to the communication unit 105 of the image projection apparatus 700 through the communication unit 752, and is sent from the communication unit 105 to the deviation detection unit 102. Thus, the process of step S306 can be performed in the same manner as in the first embodiment.

  As described above, by using the image projection device 700 and the imaging device 750 in combination, it is possible to correct the deviation of the front surface and the back surface of the printed material 110 by photographing from the front surface side of the printed material 110. In the case where the ambient light on the front side of the printed matter 110 which is the viewing environment of the user is extremely small or the light transmittance of the print medium of the printed matter 110 is small, the method in the first embodiment is from the back side of the printed matter 110 In some cases, it is difficult to recognize the front marker 201. On the other hand, in the present embodiment, since the image projection device 700 projects the front marker, it is possible to recognize and correct the deviation between the front surface and the back surface of the printed matter 110 even in such a situation.

  Although the present invention has been described in detail based on its preferred embodiments, the present invention is not limited to these specific embodiments, and various embodiments within the scope of the present invention are also included in the present invention. included. Furthermore, each embodiment mentioned above shows only one embodiment of the present invention, and it is also possible to combine each embodiment suitably.

  The present invention supplies a program that implements one or more functions of the above-described embodiments to a system or apparatus via a network or storage medium, and one or more processors in a computer of the system or apparatus read and execute the program. Processing is also feasible. It can also be implemented by a circuit (eg, an ASIC) that implements one or more functions.

100, 700 image projection apparatus 101, 751 imaging unit 102 shift detection unit 103 shift correction unit 104 image input unit 105, 752 communication unit 106 projection unit 108 overall control unit 750 imaging device

Claims (8)

Projection means for projecting a projection image on the reverse side of the printed matter;
First detection means for detecting an image deviation between a printed image formed on the surface of the printed matter and the projected image;
A second detection unit that detects a shift between the print image and a predetermined position on the back surface of the print as a print shift;
A correction unit that corrects the projected image based on the image shift;
An image projection apparatus comprising: control means for correcting a projection position of the projection image onto a printed matter by the projection means based on the printing deviation. A first imaging unit configured to capture the back side of the printed matter from the back side of the printed matter;
The first detection means is a back surface of the printed matter when a projection position marker corresponding to a position marker associated with the printed image and formed on the back surface of the printed matter is projected from the projection means to the back surface of the printed matter The image projection apparatus according to claim 1, wherein the image shift is detected based on a position shift between the position marker and the projection position marker in a captured image captured by the first imaging unit.   3. The image projection according to claim 2, wherein the correction means divides the photographed image into a plurality of regions each including the position marker, and corrects the projection image for each of the divided regions. apparatus.   The second detection means is a front marker formed on the front surface of the printed matter in association with the print image, the position of the front marker in the photographed image photographed from the back side of the printed matter by the first imaging means The image projection apparatus according to claim 2 or 3, wherein a deviation from the position of the front marker with respect to the position marker photographed in the photographed image is detected as the printing deviation. And a second imaging unit configured to capture a front side marker of the printed matter, which is associated with the printed image and formed on the surface of the printed matter, from the front side of the printed matter.
The second detection means includes the front marker in the photographed image photographed by the second imaging means and the position of the front marker relative to the position marker in the photographed image photographed by the first imaging means. 4. The image projection apparatus according to claim 2, wherein a shift of the image is detected as the print shift.   The image projection apparatus according to any one of claims 1 to 3, wherein the second detection unit acquires the value of the printing deviation by input or communication. It is a control method of an image projector, and
Projecting a projection image from the projection means onto the printed matter from the back side of the printed matter having the printed image formed on the front side, and detecting an image deviation between the printed image and the projected image;
Correcting the projected image based on the image shift;
Detecting a shift between the print image and a predetermined position on the back surface of the print as a print shift;
And correcting the projection position of the projection image on the printed material by the projection unit based on the printing deviation.   A program causing a computer to execute the steps of the control method of an image projection apparatus according to claim 7.