JP2009187002A - Projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projector capable of preventing projection from being performed on a projection surface which is not suitable for projection. <P>SOLUTION: The projector includes: a projection unit 110 which projects a projection image; a control circuit 101 which determines whether or not the projection surface is suitable for projection on the basis of a photographed image obtained by photographing the projection surface on which a prescribed projection image is projected by the projection unit; a determination notification part for notifying a result determined by the control circuit. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a projector.

  When projecting an image with a projector, there may be a case where there is a pattern or reflectance unevenness on the projection surface, a lighting unevenness on the projector, or an influence of the surrounding illumination environment on the projected image. In such a case, the projection image is not accurately displayed because the pattern or unevenness of the projection surface overlaps the projection image. In order to offset the influence of the pattern and display the projection image accurately, the projection plane on which the predetermined projection image is projected is photographed, and the maximum of the minimum luminance of each pixel in the projection plane of the photographed image is taken. Japanese Patent Application Laid-Open No. 2004-151820 discloses a technique for correcting a projected image so that the dynamic range of the projected image falls between the value and the minimum value of the maximum luminance of each pixel.

JP 2004-158941 A

  However, since the user determines the visibility by looking at the projection image of the projection plane, it cannot be evaluated in advance whether the projection plane is suitable for image projection.

(1) In the projector according to the first aspect of the invention, the projection surface projects based on a projection unit that projects a projection image and a captured image obtained by photographing a projection surface on which the predetermined projection image is projected by the projection unit. It is characterized by comprising determination means for determining whether or not it is suitable, and determination notification means for notifying the user of the result determined by the determination means.
(2) According to the invention of claim 2, in the projector according to claim 1, the determination means is a value obtained by multiplying the maximum luminance value in the captured image by a predetermined minimum reflectance from the pixels of the captured image. A pixel having a smaller luminance is extracted, and when the ratio of the extracted pixel to the pixel of the captured image is less than a predetermined ratio, it is determined that the projection surface is suitable for projection.
(3) According to a third aspect of the present invention, in the projector according to the first aspect, the determining means includes a plurality of predetermined reflectance threshold values R _i (i = 1, 2,..., N) and a pixel ratio threshold value. _{C i (i = 1,2, ···} , N) and using, from among the pixels of the captured image, smaller luminance than the value obtained by multiplying the maximum luminance value and a reflectance threshold R _i in the captured image , And when the ratio of the extracted pixel to the pixel of the captured image is less than the pixel ratio threshold C _i for all of i = 1, 2,..., N, the projection plane projects The reflectance threshold value R _j when i = j is smaller than the reflectance threshold value R _{j + 1} when i = j + 1 (j = 1, 2,..., N−1), The pixel ratio threshold C _j when i = _j is smaller than the pixel ratio threshold C _{j + 1} when i = j + 1 (j = 1, 2,..., N-1).
(4) According to a fourth aspect of the present invention, in the projector according to the first aspect, the determining means multiplies the maximum luminance value in the captured image by a predetermined minimum reflectance from the pixels of the captured image. A plurality of continuous pixels having a luminance smaller than the value is extracted, and when the ratio of the extracted pixels to the pixels of the captured image is less than a predetermined ratio, it is determined that the projection plane is suitable for projection.
(5) According to a fifth aspect of the present invention, in the projector according to the first aspect, the determination means includes a pixel of each captured image obtained by photographing a projection surface obtained by projecting the pixel primary color image of the projector for each single color. From this, pixels having a luminance smaller than a value obtained by multiplying the maximum luminance value of all the pixels of each photographed image by a predetermined minimum reflectance are extracted, and all pixel primary color images are extracted with respect to the pixels of the photographed image. When the ratio of pixels is less than a predetermined ratio, it is determined that the projection plane is suitable for projection.

  According to the present invention, it is possible to determine whether or not the projection surface is suitable for projection, and notify the user of the determination result.

1 is an external view of a projector according to an embodiment of the present invention. It is a block diagram explaining the structure of the projector in embodiment of this invention. It is a flowchart for demonstrating the image process performed by an image process part. It is a figure for demonstrating the projection surface judgment process in embodiment of this invention. It is a flowchart for demonstrating the projection plane determination process in the 1st Embodiment of this invention. It is a flowchart for demonstrating the projection plane determination process of 2nd Embodiment, when the correction amount which correct | amends a projection image is eased. It is a flowchart for demonstrating the projection plane determination process of 3rd Embodiment based on the combination of several R * _min_th and C_th. It is a flowchart for demonstrating the projection surface judgment process of 4th Embodiment based on a continuous pixel. It is a flowchart for demonstrating the projection surface judgment process of 5th Embodiment based on the saturation of a projection surface. 10 is a flowchart following the process of FIG. 9. It is a flowchart following the process of FIG. It is a flowchart for demonstrating the image processing in the 6th Embodiment of this invention.

  Hereinafter, an embodiment for carrying out the present invention will be described with reference to the drawings. The projector according to the present invention corrects an input image used for projecting onto a projection surface in order to improve the appearance and visibility of the projection image according to the state of the projection surface. Prior to the projection, an image projected on the projection plane is captured, and based on the captured image, it is determined whether the projection plane is appropriate for projection, and the user is notified.

-First embodiment-
FIG. 1 is a front view of a projector 1 according to an embodiment of the present invention. As shown in FIG. 1, a projection lens 111A constituting the projection optical system 111 (see FIG. 2) and a photographing lens 121A constituting the imaging optical system 121 (see FIG. 2) are provided on the front of the projector 1. Yes. The projector 1 projects projection information such as an image by a built-in projection unit 110 (see FIG. 2) toward a front screen or the like while being placed on a desk or the like.

  FIG. 2 is a block diagram illustrating the configuration of the projector 1. In FIG. 2, the projector 1 includes a projection unit 110, an imaging unit 120, a control circuit 101, a memory 102, an operation unit 103, an external interface (I / F) circuit 104, and a memory card interface (I / F). 105, and a memory card 150 is connected to the memory card interface 105.

  The control circuit 101 includes a microprocessor and its peripheral circuits. Based on the control program, the control circuit 101 performs a predetermined calculation using signals input from each part in the projector. Then, the control circuit 101 sends the calculation result to each part in the projector as a control signal, and controls the projection operation and the photographing operation of the projector 1. The control program is stored in a ROM (not shown) in the control circuit 101.

  The control circuit 101 includes an image processing unit 101A. The image processing unit 101A performs image processing on image data acquired via the external interface 104 or image data acquired from the memory card 150. Details of the image processing performed by the image processing unit 101A will be described later.

  The memory 102 is used as a working memory for the control circuit 101. The operation unit 103 includes buttons and switches, and sends operation signals corresponding to the operated buttons and switches to the control circuit 101. The memory card 150 can write, store, and read data according to instructions from the control circuit 101.

  The projection unit 110 includes a projection optical system 111, a liquid crystal panel 112, an LED light source 113, and a projection control circuit 114. The LED light source 113 illuminates the liquid crystal panel 112 with brightness according to the supply current. The liquid crystal panel 112 generates a light image according to the drive signal from the projection control circuit 114. The projection optical system 111 projects a light image emitted from the liquid crystal panel 112. The projection control circuit 114 sends a control signal to the LED light source 113 and the liquid crystal panel 112 according to an instruction from the control circuit 101.

  The projection unit 110 is configured to be able to project an image based on image data supplied from an external device via the external interface circuit 104 in addition to the image data stored in the memory card 150, and is instructed by the control circuit 101. Project an image. The image data image stored in the memory card 150 or the image data image supplied from the external device via the external interface circuit 104 is hereinafter referred to as a projection original image.

  The imaging unit 120 includes an imaging optical system 121, an imaging element 122, and an imaging control circuit 123, and takes an image of the projection plane in response to an instruction from the control circuit 101. The imaging optical system 121 forms a subject image on the imaging surface of the imaging element 122. As the image sensor 122, a CCD, a CMOS image sensor, or the like is used. The imaging control circuit 123 drives and controls the imaging element 122 according to an instruction from the control circuit 101 and performs predetermined signal processing on the image signal output from the imaging element 122.

  Image processing performed by the image processing unit 101A of the control circuit 101 will be described. In the image processing according to the embodiment of the present invention, the projection original image is based on the image of the projection plane photographed by the imaging unit 120 so that the pattern and dirt on the projection plane become inconspicuous when the projection original image is projected onto the projection plane. Perform color correction. Further, the image processing unit 101 </ b> A is configured such that the distortion of the projection image due to the optical axis of the projection optical system 111 and the optical axis of the imaging optical system 121 not matching or the optical axis of the projection optical system 111 with respect to the projection surface. It is also possible to correct the tilt and distortion of the projected image due to non-verticality. Since the image processing according to the embodiment of the present invention is characterized by the above-described color correction, the color correction will be mainly described.

  The image processing performed by the image processing unit 101A will be described with reference to the flowchart of FIG. The processing in FIG. 3 is executed in the image processing unit 101A by a program that starts when the projector 1 starts processing for starting projection.

  In step S1, a geometric correction coefficient for performing geometric correction of the projection original image is calculated. Geometric correction refers to distortion of a projected image caused by the optical system optical axis of the projection unit 110 and the optical system optical axis of the imaging unit 120 not matching, or the optical system optical axis of the projection unit 110 with respect to the projection surface. This is a correction for eliminating tilt, distortion, etc. of the projected image due to non-verticality. Since the calculation method of the geometric correction coefficient is a conventional technique, the description thereof is omitted.

  Here, the image processing unit 101 </ b> A of the control circuit 101 performs an interpolation process so that the number of projected original images matches the resolution of the projector 1. Furthermore, the image processing unit 101A performs an interpolation process on the image captured by the imaging unit 120 so as to match the resolution of the projector 1. It is assumed that the projection original image subjected to the above-described interpolation processing is corrected as follows using the captured image subjected to this interpolation processing, and the corrected image is projected. This is to clarify the correspondence between the pixels of the projected image and the pixels of the captured image and increase the processing speed.

  In step S2, the projection characteristics of the projection unit 110 are calculated. The projection characteristics are characteristics indicating the relationship between the pixel values (R, G, B) of the input image and the colorimetric values (X, Y, Z) of the projection image reproduced on the projection plane. In other words, the projection characteristic is a characteristic representing a relationship between a projection original image to be projected on the projection plane and a captured image obtained by photographing the projection plane on which the projection original image is projected. The colorimetric value is affected by illumination unevenness of the projection unit 110, the color and pattern of the projection surface, and the brightness of the projection surface by ambient illumination. Therefore, the projection unit 110 projects and projects a predetermined projection image (a black image, an R image, a G image, and a B image as described later) represented by known pixel values (R, G, B). The projected image on the surface is photographed by the photographing unit 120, and the colorimetric values (X, Y, Z) are detected from the photographed image to calculate the projection characteristics. Then, by correcting and projecting the input image with a correction coefficient determined based on the projection characteristics, the projection unit 110 does not depend on uneven illumination, the color or pattern of the projection surface, and the brightness of the projection surface due to ambient illumination. It is possible to appreciate the projected image that is more expressed than the appearance of the input image. Specific processing of the projection characteristics will be described later.

  Step S3 determines a correction coefficient for the projection image. In other words, using the projection characteristics obtained in step S2, correction to be performed on the input image so that the projection image reproduces the input image (projected original image) without being affected by the state of the projection surface or the ambient illumination environment. Determine the coefficient. A predetermined projection image of the aforementioned known pixel value projected from the projection unit 110 is captured by the imaging unit 120, and the captured image is analyzed to determine a correction coefficient of the projection image. This correction coefficient becomes the correction amount of the projection original image. Details of this processing will also be described later.

  In step S4, a projection plane determination is made as to whether or not the projection plane is appropriate for projection. Details of this processing will also be described later.

  In step S <b> 5, image data of the projection original image is read from the external interface circuit 104 or from the memory card 150 and stored in the memory 102. In step S6, the projection original image data read in step S5 is corrected with the correction coefficient determined in step S3. In step S7, the projection original image data corrected in step S6 is converted to analog, and a projection image is projected.

  In step S8, it is determined whether there is projection original image data to be projected next. If there is projection original image data to be projected next, step S8 is affirmed and the process returns to step S5. If there is no projection original image data to be projected next, a negative determination is made in step S8, and the process ends.

  Next, steps S2, S3, S4, and S6 will be described in more detail.

ただし、

-Calculation of projection characteristics-
The calculation of the projection characteristics performed in step S2 will be described.
When a projection image is generated from the input image data whose i-th pixel value is given by (R, G, B) _i and projected by the projection unit 110, the colorimetric values (i.e., colorimetric values of the projection plane corresponding to the i-th pixel value) X, Y, Z) _i is expressed by the following equation (1).

However,

Here, γ represents the gradation characteristic of the projection unit 110. M _pi represents a color conversion matrix for converting the pixel values (R ^γ , G ^γ , B ^γ ) _i of the projection unit 110 into the colorimetric values of the illumination of the projection unit 110. (X _kp , Y _kp , Z _kp ) _i represents the illumination condition of the projection plane including ambient illumination when a black image is projected by the projection unit 110. R * _i represents the reflectance characteristic of the projection surface.

  The subscript i has the following meaning. In the projector according to this embodiment, the projection surface is imaged by projecting a known image such as a white image or a black image, and based on the captured image, not only the unevenness of the reflectance due to the pattern of the projection surface, but also the projection unit 110 illumination unevenness, ambient illumination and in-plane unevenness of black spots are also corrected. Therefore, the subscript i is used to express different projection characteristics for each pixel area on the projection plane.

In the equation (1), (X _k , Y _k , Z _k ) is based on a projection plane photographed image when a black image ((R, G, B) _i = (0, 0, 0) _i ) is projected. To decide. Note that the colorimetric value of the projected image on the projection plane can be calculated by using a color conversion process determined in advance from the pixel value of the captured image. That is, if the profile of the captured image is sRGB, (X _k , Y _k , Z _k ) _i can be determined by applying normal sRGB conversion processing to the pixel values.

Similarly, an R image ((R, G, B) _i = (255, 0, 0) _i ), a G image ((R, G, B) _i = (0, 255, 0) _i ), and a B image A 3 × 3 matrix coefficient of the color conversion matrix M _i is determined from each captured image obtained by capturing the projection plane on which ((R, G, B) _i = (0, 0, 255) _i ) is projected. Specifically, the colorimetric values of the captured images (hereinafter referred to as projection plane captured images) on which the R image, the G image, and the B image are projected are respectively (X _r , Y _r , Z _r ), Assuming (X _g , Y _g , Z _g ) and (X _b , Y _b , Z _b ), the color conversion matrix M _i is expressed by the following equation (3).

-Determination of projection image correction coefficient-
The determination of the projection image correction coefficient performed in step S3 will be described.
If the projection surface has unevenness (hereinafter simply referred to as “unevenness”, including unevenness in the reflectance of the projection surface or illumination unevenness) or a pattern, the pixel values of the captured image obtained by photographing the projection surface are uniform. Instead, the pixel values correspond to the unevenness and the pattern. In other words, the maximum displayable color gamut varies with each pixel. In this embodiment, first, the maximum displayable color gamut range is determined. The luminance Y _i on the projection plane is calculated from the equation (1):

Therefore, the displayable luminance range is determined by the range that Y _i can take when it is shaken in the range of 0 ≦ R _i , G _i , B _i ≦ 255 in the equation (4). _Usually, Y _r, Y _g, since a Y b> _{Y k,} displayable intensity range of each pixel is a white image _{((R, G, B)} i = (255,255,255) i) a projection The maximum displayable brightness Y _{MAX, i} can be obtained as the display brightness when the image is projected, and the display brightness when the black image is projected can be obtained as Y _{MIN, i} .

Here, in order to reduce the influence of the unevenness or pattern of the projection surface on the visibility of the projection image, the maximum luminance Y _{MAX on} the projection surface of the projection surface captured image is MIN (Y _{MAX, i} ), and the minimum luminance Y _MIN. It is necessary to correct the projection original image data so that becomes MAX (Y _{MIN, i} ). That is, the maximum luminance Y _MAX when the correction target projection original image is projected is corrected so as to be the minimum luminance value MIN (Y _{MAX, i} ) among the plurality of pixels constituting the captured image at the time of projecting the white image. There is a need. Further, the minimum luminance Y _MIN when the correction target projection original image is projected is corrected so as to become the maximum luminance value MAX (Y _{MIN, i} ) among a plurality of pixels constituting the captured image at the time of black image projection. There is a need.

すなわち、最大輝度Ｙ_ＭＡＸをＭＩＮ（Ｙ_{ＭＡＸ,ｉ}）まで補正せず、閾値Ｙ_ｔｈ（＜ＭＩＮ（Ｙ_{ＭＡＸ,ｉ}）まで補正することにより、低輝度側の画素値の補正量を抑制する。 However, when the above-described correction is performed on all the pixels when an extremely dark portion is on the projection surface, the dynamic range becomes very narrow, and the visibility of the corrected projected image itself is deteriorated. Therefore, to set the luminance threshold Yth, among the pixels of the projected image, for low luminance of the pixel from the luminance brightness threshold value Y _th when projected, mitigate the correction amount, the following maximum luminance Y _MAX ( 5) Determine as shown in the equation.

That is, without correcting the maximum brightness _{Y MAX} to MIN _{(Y MAX, i),} by correcting to a threshold _{Y th (<MIN (Y MAX} , i), suppressing the correction amount of the pixel value of the low luminance side.

-Projection plane judgment-
Since the projection plane determination process performed in step S4 is the main process of the present invention, a specific method will be described later.

ここで、黒画像を投影したときの画素の最大輝度、すなわち、Ｙ_ＭＩＮ＝ＭＡＸ（Ｙ_{ＭＩＮ,ｉ}）となる画素値を投影画面の黒点（Ｘ_ｋ０，Ｙ_ｋ０，Ｚ_ｋ０）とする。なお、Ｍ_{ｓＲＧＢ→ＸＹＺ}はｓＲＧＢ色空間からＸＹＺ色空間への変換マトリックスである。 -Correction of projected image-
The projection image correction performed in step S6 will be described.
If the color space of the projection original image (input image) is sRGB, the colorimetric values (X, Y, Z) on the projection plane with respect to the pixel values (R ₀ , G ₀ , B ₀ ) of the projection original image _i may be as follows.

Here, the maximum luminance of a pixel when a black image is projected, that is, a pixel value _satisfying Y _MIN = MAX (Y _{MIN, i} ) is defined as a black point (X _k0 , Y _k0 , Z _k0 ) on the projection screen. M _{sRGB → XYZ} is a conversion matrix from the sRGB color space to the XYZ color space.

Therefore, using the equation (1), the corrected input pixel value (R, G, B) _i to the projection unit 110 can be calculated by the following equation (7).

  Since equation (7) is simple, sRGB is described as γ = 2.2. However, it may be calculated as a combination of a linear function and γ = 2.4 as defined.

-Projection plane judgment-
Next, with reference to FIG. 4, the projection plane determination process in step S4 in the embodiment of the present invention will be described. FIG. 4A is a diagram for explaining the projection plane 30. The projection surface 30 is a wall with a star pattern. Prior to projecting the projection image, the white image is projected onto the projection plane 30. If it is determined that the projection surface 30 is inappropriate for projection, a cross mark 31 indicating that the projection surface 30 is inappropriate is projected from the projector 1 as shown in FIG. The user who sees the cross mark 31 recognizes that the projection plane is inappropriate for projection. Then, the user can move the projection plane to another plane before starting projection with the projection original image.

  FIG. 4C shows an example of a projected image when the projected image is projected onto a projection plane determined to be inappropriate. Even if the projection original image is corrected, the star mark is superimposed and displayed on the projection image 32 on the projection plane, and the appearance is poor.

  Next, a projection plane determination process performed by the control circuit 101 will be described with reference to the flowchart of FIG. The process of FIG. 5 is executed in the control circuit 101 by a program that starts when the projector 1 starts a process for starting projection.

In step S11, a white image ((R, G, B) _i = (255, 255, 255)) is projected from the projection unit 110 onto the projection plane. In step S <b> 12, the projection plane is imaged by the imaging unit 120.

  In step S13, the luminance Y is calculated from the pixel value RGB of the captured image. The brightness Y is calculated as follows. Using the conversion matrix from the RGB color system stored in the control circuit 101 in advance to the XYZ color system (CIE 1931 color system), the pixel value RGB of the photographed image is converted into the XYZ color system, Luminance Y is calculated. Note that the conversion matrix is determined from the spectral characteristics of the imaging element 122 in the imaging unit 120.

  In step S14, the maximum luminance Y_max is calculated among the luminances of a plurality of pixels constituting the captured image. In step S15, pixels whose luminance Y satisfies the relationship Y_max × R * _min_th> Y are extracted from the pixels of the entire captured image, and the extracted pixels are extracted with respect to the ratio of the extracted images, that is, the total number of pixels of the entire captured image. It is determined whether the ratio of the number of pixels is equal to or greater than C_th.

  Here, R * _min_th is a reflectance threshold value, and can be determined as follows. That is, the correction amount of the projection original image data increases as the reflectance of the projection surface decreases. And even if it correct | amends if a reflectance becomes below a predetermined value, it will become difficult to improve the visibility of a projection image. Therefore, the minimum reflectance that can improve the visibility by correction is set as R * _min_th. The value of R * _min_th is 0.02, for example.

  C_th is 0%, for example, and can be determined as follows. As described above, even if the projection original image data is corrected, if there are many pixels satisfying the relationship of luminance Y of Y_max × R * _min_th> Y, the number of incompletely corrected pixels increases, and the user can improve the visibility of the projection image. You will be dissatisfied with it. Therefore, the value of C_th may be determined within a range in which such user dissatisfaction does not occur. For example, C_th is 0%.

  If the ratio of pixels satisfying the relationship of luminance Y to Y_max × R * _min_th> Y is less than C_th, a negative determination is made in step S15, and the process proceeds to step S16. If the ratio of pixels satisfying the relationship of luminance Y to Y_max × R * _min_th> Y is equal to or greater than C_th, an affirmative determination is made in step S15 and the process proceeds to step S17.

  In step S16, the projection unit 110 projects a projectable mark (a mark), which is a mark indicating that the projection surface is suitable for projection, onto the projection surface. Then, the process proceeds to step S5 in FIG. 3, and the image corrected by the above-described method is projected. In step S17, the projection unit 110 projects a projection impossible mark (cross mark) that is a mark indicating that the projection plane is not suitable for projection onto the projection plane.

According to the embodiment described above, the following operational effects can be obtained.
(1) It is determined whether or not the projection plane is suitable for projection based on a projection plane captured image obtained by shooting a predetermined projection image, in this example, a projection plane on which a white image is projected, and the determination result Was notified to the user. Accordingly, it is possible to prevent the projection from being performed on the projection plane in which the deterioration of the image quality due to the unevenness or pattern of the projection plane cannot be avoided even if the projection original image data is corrected.

(2) The maximum luminance Y_max is detected among all the pixels of the projection plane photographed image, and a reference luminance value obtained by multiplying the luminance Y_max by the minimum reflectance R * _min_th of the projection plane is set. The number of pixels that can represent only a luminance smaller than the reference luminance value at the maximum, that is, the proportion of the pixels whose luminance Y satisfies the relationship Y_max × R * _min_th> Y is calculated, and the proportion is equal to or greater than the threshold C_th If so, it was determined that the projection surface was not suitable for projection. In other words, it is determined that a projection surface in which the proportion of pixels that can be expressed only at a maximum brightness that is darker than the reference brightness is less than a predetermined value is suitable for projection. Thereby, it is possible to appropriately determine whether or not the projection plane is suitable for projection only by using the luminance value of the pixels constituting the projection plane photographed image.

-Second Embodiment-
In the projector according to the second embodiment, the following determination criteria (a) to (c) are adopted to reduce the correction amount of the projection original image data according to the state of the projection surface.
(A) When the ratio of pixels whose luminance is lower than a reference value (hereinafter referred to as “low luminance pixels”) in the projection plane image obtained by imaging the projection plane is less than a predetermined value (b) Projection plane imaging When the position of the low luminance pixel in the image is around the projection plane (c) When the number of continuous low luminance pixels is small

  That is, in the cases (a) to (c), when the low-luminance portion of the projection surface hardly affects the image quality of the projection image on the projection surface, the correction amount is relaxed. Correction is performed by the following equations (8) and (9).

The input pixel value to the projection unit 110 the corrected (R, G, _{B) i is} based on the magnitude of the _{Y MAX, i,} the following (8), can be calculated by equation (9).
(1) Pixel i satisfying Y _{MAX, i} ≧ Y _MAX ;

(2) Pixel i satisfying Y _{MAX, i} <Y _MAX ;

  Since the expressions (8) and (9) are simple, they are described as γ = 2.2 of sRGB. However, it may be calculated as a combination of a linear function and γ = 2.4 as defined.

  In the projector according to the first embodiment, the minimum reflectance R * _min_th and the threshold value C_th are used as criteria for determining whether or not the projection surface is suitable for image projection. However, in the second embodiment, the correction amount is reduced. In addition, the second criterion is adopted by preventing visibility deterioration due to overcorrection.

  The second determination criterion is a magnitude relationship between the minimum reflectance R * _min_th1 × Y_max and the second threshold C_th1. However, minimum reflectance R * _min_th1 <minimum reflectance R * _min_th, threshold C_th1> threshold C_th. The minimum reflectance R * _min_th1 is, for example, 0.02, and the threshold value C_th1 is, for example, 0.01 (1%).

  Next, a projection plane determination process according to the second embodiment will be described with reference to the flowchart of FIG. The process in FIG. 6 is executed in the control circuit 101 by a program that starts when the projector 1 starts a process for starting projection. The same processes as those in FIG. 5 are denoted by the same reference numerals, and portions different from the processes in FIG. 5 will be mainly described.

  After step S14, the process proceeds to step S21. In step S21, it is determined whether or not to reduce the degree of correction of the projection original image data, in other words, whether or not to reduce the correction amount. From the pixels of the entire photographed image, pixels whose luminance Y satisfies the relationship Y_max × R * _min_th1> Y are extracted, and it is determined whether or not the ratio of the number of extracted pixels to the total number of pixels is equal to or greater than the threshold C_th1. . Here, as described above, the minimum reflectance R * _min_th1 is a predetermined minimum reflectance of the projection surface, and is smaller than the reference reflectance R * _min_th in the first embodiment. The threshold value C_th1 is a predetermined ratio, and is a value larger than the threshold value C_th as described above. When the ratio of pixels satisfying the relationship of luminance Y of Y_max × R * _min_th1> Y is less than C_th1, a negative determination is made in step S21, and the process proceeds to step S16. If the ratio of the pixels satisfying the luminance Y of Y_max × R * _min_th1> Y is greater than or equal to the threshold C_th1, an affirmative determination is made in step S21, and the process proceeds to step S17.

  C_th and C_th1 may be determined in consideration of the allowable range of the number of pixel defects of the liquid crystal panel 112 in the projection unit 110. In step S21, the determination criterion (a) described above is used. However, determination criteria such as (b) and (c) may be used instead or in combination.

-Third embodiment-
In the projector according to the first embodiment, one determination reference value represented by the product of the minimum reflectance R * _min_th and the threshold value C_th is used as a determination reference whether or not the projection surface is suitable for image projection. In the projector according to the third embodiment, three large, medium, and small minimum reflectances R * _min_th2 to 4 and three large, medium, and small thresholds C_th2 to 4 are determined as criteria for determining whether or not the projection surface is suitable for image projection. The first determination reference value R * _min_th2 × C_th2, the second determination reference value R * _min_th3 × C_th3, and the third determination reference value R * _min_th4 × C_th4 expressed by their product are used.

  In the third embodiment, even when unevenness is not so conspicuous on the projection surface, the above-described three determination reference values are considered in consideration that the visibility of the projected image is deteriorated when the proportion of the unevenness area is large. First determination reference value R * _min_th2 × C_th2 (for example, 0.002 × 0.001), second determination reference value R * _min_th3 × C_th3 (for example, 0.02 × 0.01), and third determination reference The value R * _min_th4 × C_th4 (eg, 0.2 × 0.1) is used.

  Next, a projection plane determination process according to the third embodiment will be described with reference to the flowchart of FIG. The processing in FIG. 7 is executed in the control circuit 101 by a program that starts when the projector 1 starts processing for starting projection. The same processes as those in FIG. 5 are denoted by the same reference numerals, and portions different from the processes in FIG. 5 will be mainly described. Here, R * _min_th2 is smaller than R * _min_th3, and R * _min_th3 is smaller than R * _min_th4. Further, C_th2 is smaller than C_th3, and C_th3 is smaller than C_th4.

  After step S14, the process proceeds to step S31. In step S31, a pixel whose luminance Y satisfies the relationship Y_max × R * _min_th2> Y is extracted from the pixels of the entire captured image, and whether or not the ratio of the extracted pixel number to the total pixel number is equal to or greater than C_th2. Determine. For example, R * _min_th2 is 0.002 and C_th2 is 0.1%. If the ratio of the extracted number of pixels to the total number of pixels is less than C_th2, a negative determination is made in step S31, and the process proceeds to step S32. If the ratio of the number of extracted pixels to the total number of pixels is equal to or greater than C_th2, an affirmative determination is made in step S31, and the process proceeds to step S17.

  In step S32, a pixel whose luminance Y satisfies the relationship Y_max × R * _min_th3> Y is extracted from the pixels of the entire photographed image, and whether or not the ratio of the extracted number of pixels to the total number of pixels is C_th3 or more. Determine. For example, R * _min_th3 is 0.02 and C_th3 is 1%. If the ratio of the extracted number of pixels to the total number of pixels is less than C_th3, a negative determination is made in step S32, and the process proceeds to step S33. If the ratio of the number of extracted pixels to the total number of pixels is equal to or greater than C_th3, an affirmative determination is made in step S32 and the process proceeds to step S17.

  In step S33, pixels whose luminance Y satisfies the relationship Y_max × R * _min_th4> Y are extracted from the pixels of the entire captured image, and whether or not the ratio of the extracted number of pixels to the total number of pixels is C_th4 or more. Determine. For example, R * _min_th4 is 0.2 and C_th4 is 10%. If the ratio of the extracted number of pixels to the total number of pixels is less than C_th4, a negative determination is made in step S33, and the process proceeds to step S16. If the ratio of the number of extracted pixels to the total number of pixels is equal to or greater than C_th4, an affirmative determination is made in step S33, and the process proceeds to step S17.

  A combination of a plurality of R * _min_th and C_th may be adjustable depending on the user, the captured image, the imaging condition, and the like.

-Fourth embodiment-
In the projector according to the first embodiment, if the luminance Y is a pixel satisfying the relationship of Y_max × R * _min_th> Y, the single pixel or the continuous pixels are all added as the number of pixels. In the projector according to the fourth embodiment, when at least two pixels satisfying the relationship of luminance Y of Y_max × R * _min_th> Y are consecutive, these pixels are added, and the total number of pixels as a result of the addition is calculated. Calculate the percentage. In other words, the projection plane is evaluated by excluding pixels that have a luminance Y satisfying the relationship Y_max × R * _min_th> Y but are not continuously distributed.

  Next, a projection plane determination process according to the fourth embodiment will be described with reference to the flowchart of FIG. The processing in FIG. 8 is executed in the control circuit 101 by a program that starts when the projector 1 starts processing for starting projection. The same processes as those in FIG. 5 are denoted by the same reference numerals, and portions different from the processes in FIG. 5 will be mainly described.

  When the process proceeds from step S14 to step S41, continuous pixels that have a luminance Y satisfying the relationship Y_max × R * _min_th> Y are extracted from the pixels of the captured image. In step S42, it is determined whether the ratio of the number of pixels extracted in step S41 to the total number of pixels is equal to or greater than C_th. If the ratio of the extracted number of pixels to the total number of pixels is less than C_th, a negative determination is made in step S42, and the process proceeds to step S16. If the ratio of the number of extracted pixels to the total number of pixels is equal to or greater than C_th, an affirmative determination is made in step S42 and the process proceeds to step S17.

  In this case, as in FIG. 6, when (a) the ratio of pixels whose luminance is lower than the reference value (hereinafter referred to as low luminance pixels) in the projection plane captured image obtained by imaging the projection plane is small, (B) The correction amount may be relaxed when the position of the low-luminance pixel in the projected-surface photographed image is the periphery, and (c) when the number of pixels when the low-luminance pixel continues is small. When the correction amount is relaxed, the second determination reference value described with reference to FIG. 6 may be used.

-Fifth embodiment-
In the projector according to the first embodiment, a white image ((R, G, B) i = (255, 255, 255)) is projected from the projection unit 110 onto the projection plane, and the projection plane is projected by the monochrome image. It was judged whether it was suitable. However, the R image ((R, G, B) _i = (255, 0, 0)), the G image ((R, G, B) _i = (0, 255, 0)) and the B image ((R, G, B). G, B) _i = (0, 0, 255)) may be projected onto the projection plane, and an image having color may be projected onto the projection plane to evaluate the projection plane. For example, if there is a portion with high saturation in a part of the projection surface, it can be determined that the projection surface is not suitable for projection.

  Next, projection plane determination processing according to the fifth embodiment will be described with reference to the flowcharts of FIGS. 9 to 11 are executed in the control circuit 101 by a program that starts when the projector 1 starts a process for starting projection.

9, the R image ((R, G, B) _i = (255, 0, 0)) is projected from the projection unit 110 onto the projection plane. In step S502, the imaging unit 120 captures the projection plane. In step S503, the luminance YR is calculated from the pixel value RGB of the captured image. In step S504, YR * _max which is the maximum value of the luminance YR in the captured image is calculated.

  In step S505, pixels whose luminance YR satisfies the relationship YR * _max × R * _min_th> YR are extracted from the pixels of the entire captured image, and whether the ratio of the extracted number of pixels to the total number of pixels is equal to or greater than C_th. Determine whether or not. If the ratio of the number of extracted pixels to the total number of pixels is less than C_th, a negative determination is made in step S505, and the process proceeds to step S506. If the ratio of the extracted number of pixels to the total number of pixels is equal to or greater than C_th, an affirmative determination is made in step S505, and the process proceeds to step S517.

In step S506 in FIG. 10, the G image ((R, G, B) _i = (0, 255, 0)) is projected from the projection unit 110 onto the projection plane. In step S507, the imaging unit 120 images the projection plane. In step S508, the luminance YG is calculated from the pixel value RGB of the captured image. In step S509, YG_max that is the maximum value of luminance YG in the captured image is calculated.

  In step S510, pixels whose luminance YG satisfies the relationship YG_max × R * _min_th> YG are extracted from the pixels of the entire captured image, and whether or not the ratio of the extracted number of pixels to the total number of pixels is equal to or greater than C_th. Determine. If the ratio of the extracted number of pixels to the total number of pixels is less than C_th, a negative determination is made in step S510, and the process proceeds to step S511. If the ratio of the extracted number of pixels to the total number of pixels is equal to or greater than C_th, an affirmative determination is made in step S510 and the process proceeds to step S517.

In step S511 in FIG. 11, a B image ((R, G, B) _i = (0, 0, 255)) is projected from the projection unit 110 onto the projection plane. In step S512, the imaging unit 120 captures the projection plane. In step S513, the luminance YB is calculated from the pixel value RGB of the captured image. In step S514, YB_max that is the maximum value of luminance YB in the captured image is calculated.

  In step S515, a pixel whose luminance YB satisfies the relationship YB_max × R * _min_th> YB is extracted from the pixels of the entire captured image, and whether or not the ratio of the extracted number of pixels to the total number of pixels is equal to or greater than C_th. Determine. If the ratio of the extracted number of pixels to the total number of pixels is less than C_th, a negative determination is made in step S515, and the process proceeds to step S516. If the ratio of the extracted number of pixels to the total number of pixels is equal to or greater than C_th, an affirmative determination is made in step S515, and the process proceeds to step S517.

  In step S516, the projection unit 110 projects a projectable mark (mark) that is a mark indicating that the projection surface is suitable for projection onto the projection surface. In step S517, the projection unit 110 projects a projection impossible mark (cross mark) that is a mark indicating that the projection plane is not suitable for projection onto the projection plane.

  Also in this case, as in the third embodiment described with reference to FIG. 7, each luminance Y (R, G, B) is Y (R, G, B) _max × in a combination of a plurality of R * _min_th and C_th. When the ratio of pixels satisfying the relationship of R * _min_th> Y (R, G, B) is less than C_th, it may be determined that the projection plane is suitable for projection.

The above embodiment can be modified as follows.
(1) The projection plane is evaluated in two stages, whether the projection plane is suitable for projection, but (i) the projection plane is suitable for projection, (ii) it is not suitable for projection on a part of the projection plane. The projection plane may be evaluated in three stages: there are portions, but the other portions are suitable for projection, and (iii) the projection plane is not suitable for projection. At this time, if the projection surface is suitable for projection, a round mark is projected, and if it is not suitable for projection on a part of the projection surface, but the other part is suitable for projection, a triangle mark mark is projected and projected. If the surface is not suitable for projection, a cross mark is projected. When a part of the projection plane is not suitable for projection, the user can determine whether or not to project on the projection plane, and the convenience of the projector is improved. This is because, depending on the projection image, it may be difficult to see a part of the projection image.

(2) Whether or not the projection plane is suitable for projection is determined based on the maximum value (Y_max) of the luminance Y in the projection plane photographed image. However, it may be determined whether or not the projection plane is suitable for projection from the average luminance of the projection plane photographed image. In this case, if the average luminance of the projection plane photographed image is greater than a predetermined value, it is determined that the projection plane is suitable for projection, and if the average luminance of the projection plane photographed image is less than the predetermined value, the projection plane is suitable for projection. Judge that there is no.

(3) When determining whether or not the projection plane is suitable for projection from the viewpoint of saturation, the pixel value RGB of the projection plane photographed image is converted into the XYZ color system, further converted into CIELAB, and the saturation C The determination may be made using a value of = √ (a ² + b ² ). In this case, a C threshold value is stored in advance for each lightness L. This is because the C threshold value depends on the lightness L, and therefore the C threshold value cannot be a constant value.

(4) The numerical values of R * _min_th and C_th in the above embodiments are examples, and are not limited to the values in the embodiments. This is because the numerical values of R * _min_th and C_th vary depending on the characteristics of the projector 1 (allowable range of illumination unevenness, defects, etc.), the correction method of the projected image, and the like. For example, if the driving amount of the LED light source 113 can be increased by x times, the value of R * _min_th can be made about 1 / x times that of the embodiment.

(5) The method of notifying the user of the result of determining whether or not the projection plane is suitable for projection is not limited to the method of projecting the cross mark 31 onto the projection plane 30. For example, when the projector is provided with a display unit, the state of the projection surface may be notified to the user by performing appropriate projection surface display and inappropriate projection surface display on the display unit.

(6) It may be determined whether or not the projection surface is suitable for projection in consideration of the projection image. For example, when the projection image is a photograph of a blue sky, the pattern of the projection surface is conspicuous, and therefore the determination criterion for determining whether the projection surface is suitable for projection is increased. That is, if there is even a conspicuous pattern on the projection surface, it is determined that it is not suitable for projection. On the other hand, if the projection image is a jungle image, the projection image is complex and the pattern on the projection surface is inconspicuous. Therefore, the criterion for determining whether or not the projection surface is suitable for projection is lowered. That is, even if a somewhat conspicuous pattern or the like is present on the projection surface, it is determined that it is suitable for projection.

As described above, the evaluation of the projection image that affects the determination criterion for determining the propriety of the projection on the projection plane is performed as follows (A) and (B).
(A) The distribution of the frequency components of the projection image data is examined. If there are many high-frequency components, the projection image is an image with a fine structure such as a jungle image, so the criterion for determining whether or not projection is appropriate on the projection plane is lowered. On the other hand, when the high-frequency component is small, the projection screen is an image having a rough structure such as an image of a blue sky.

  For example, the projection image is binarized with a threshold value of a predetermined edge strength using a Laptian filter or the like. Based on the binarized image, it is determined whether the projected image is an image with a fine structure or an image with a rough structure. For example, if the ratio of the number of pixels with edge strength greater than the threshold to the number of pixels in the entire projected image is greater than or equal to a predetermined value, it is determined that the image has a fine structure.

(B) The difference between the projected image and the image obtained by repeatedly reducing and enlarging the projected image may be used to determine whether the image is a fine structure or a coarse structure. For example, the following Laplacian pyramid may be used.

  That is, a 1/2 times reduced image is created from the projected image. This 1/2 times reduced image is made a double enlarged image, and the difference between the projected image and the enlarged image is taken. This difference becomes a high frequency component. Furthermore, it is possible to divide into frequency components by repeating the acquisition of the difference image between the image obtained by repeating the reduction of 1/2 times and the enlargement of 2 times and the projection image. An image obtained by calculating a difference between the projected image and an image obtained by repeating the reduction and the enlargement of ½ times and twice the predetermined number of times from the projection image is binarized with a predetermined threshold value. Based on the binarized image, it may be determined whether the projected image is an image with a fine structure or an image with a rough structure.

  The threshold value for binarization varies depending on how many edges are extracted and the noise level of the projection image (depending on the brightness at the time of photographing the projection surface). For example, if it is 8 bit gradation, it may be about 10.

  The projected image is divided into a fine structure area and a rough structure area from the image with the edge emphasized, and the projection image is not corrected in the fine structure area, and the projection image is corrected in the rough structure area. You may do it.

(7) In the projector according to the third embodiment, three different minimum reflectances R * _min_th2 to 4 and three threshold values C_th2 to 4 are defined, and three first determination reference values R expressed by their products. Although * _min_th2 × C_th2, the second determination reference value R * _min_th3 × C_th3, and the third determination reference value R * _min_th4 × C_th4 were used as the determination reference as to whether or not the projection surface is suitable for image projection. The number of criteria is not limited to three. N different N (N is a natural number of 3 or more) minimum reflectances R _i (i = 1, 2,..., N) and thresholds C _i (i = 1, 2,..., N). R _i × C _i (i = 1, 2,..., N) expressed by the product of N pieces may be used as a criterion for determining whether or not the projection plane is suitable for image projection. . Here, the minimum reflectance R _j when i = j is smaller than the minimum reflectance R _{j + 1} when i = j + 1, and the threshold C _j when i = j is the threshold C when i = j + 1. _It is smaller than _{j + 1} (j = 1, 2,..., N−1).

(8) In the projector according to the fifth embodiment, R image _{((R, G, B)} i = (255,0,0)), G image _{((R, G, B)} i = (0,255, 0)) and B images ((R, G, B) _i = (0, 0, 255)) were projected onto the projection plane to evaluate the projection plane. However, the pixel primary color image of the projector to be projected on the projection plane is not limited to the R image, the G image, and the B image as long as the projection plane is evaluated by projecting the pixel primary color image of the projector onto the projection plane.

  FIG. 12 is a flowchart illustrating image processing according to the sixth embodiment. Steps S601 to S607 are the same as steps S11 to S17 in FIG. That is, “project a white image” in step S601 in FIG. 12 is the same as step S11 in FIG. 5. Similarly, “shoot a projection plane” in step S602 in FIG. 12 and “pixel value of a captured image” in step S603. “Calculate brightness Y from RGB”, “Y_max calculation” in step S604, “the ratio of pixels satisfying Y_max × R * _min_th> Y in step S605? C_th or more?”, “Project projectable mark” in step S606, and “Project unmarkable mark” in step S607 is the same as step S12, step S13, step S14, step S15, step S16, and step S17 in FIG.

  If a projectable mark is projected in step S606, “calculation of projection characteristics” is performed in step S608. The “projection characteristic calculation” in step S608 is the same as the projection characteristic calculation in step S2 of FIG.

  Similarly, “determination of projection image correction coefficient” in step S609 in FIG. 12, “read projection original image” in step S610, “correction of projection image” in step S611, “project projection image” in step S612, and step S613. "Is there a next projection original image?" Is the same as Step S3, Step S5, Step S6, Step S7, and Step S8 of FIG.

  As described above, in the present embodiment, a projection plane on which a white image is projected is photographed, and whether or not the projection plane is suitable for projection is determined based on the photographed image, and the projection plane is suitable for projection. If it is, the mark that can be projected is projected, and if it is not suitable for projection, the mark that cannot be projected is projected.

  When a mark having a projection plane is projected, projection characteristics are calculated, and a projection image correction coefficient is determined based on the projection characteristics. Thereafter, the projection original image is read, the read projection original image is corrected based on the projection image correction coefficient, and the corrected projection image is projected.

  The above description is merely an example, and the present invention is not limited to the configuration of the above embodiment.

DESCRIPTION OF SYMBOLS 1 Projector 30 Projection surface 31 Cross mark 32 Projected image 101 Control circuit 102 Memory 103 Operation part 104 External interface 105 Memory card interface 110 Projection unit 120 Imaging unit

Claims (5)

Projection means for projecting a projection image;
Determination means for determining whether or not the projection surface is suitable for projection based on a captured image obtained by photographing a projection surface on which a predetermined projection image is projected by the projection means;
A projector comprising: determination notification means for notifying a user of a result determined by the determination means. The projector according to claim 1, wherein
The determination means extracts a pixel having a luminance smaller than a value obtained by multiplying a maximum luminance value in the captured image by a predetermined minimum reflectance from the pixels of the captured image, The projector according to claim 1, wherein if the ratio of the extracted pixels is less than a predetermined ratio, the projection plane is determined to be suitable for projection. The projector according to claim 1, wherein
The determination means uses a plurality of predetermined reflectance thresholds R _i (i = 1, 2,..., N) and pixel ratio thresholds C _i (i = 1, 2,..., N). And
A pixel having a luminance smaller than a value obtained by multiplying the maximum luminance value in the photographed image by the reflectance threshold R _i is extracted from the pixels of the photographed image, and the extracted pixel for the pixel of the photographed image is extracted. When the ratio of pixels is less than the pixel ratio threshold C _i , when i = 1, 2,..., N is satisfied, the projection plane is determined to be suitable for projection,
The reflectance threshold value R _j when i = j is smaller than the reflectance threshold value R _{j + 1} when i = j + 1 (j = 1, 2,..., N−1), and the pixel ratio when i = j. The projector is characterized in that the threshold C _j is smaller than the pixel ratio threshold C _{j + 1} when i = j + 1 (j = 1, 2,..., N−1). The projector according to claim 1, wherein
The determination means extracts a plurality of continuous pixels having a luminance smaller than a value obtained by multiplying a maximum luminance value in the captured image by a predetermined minimum reflectance from the pixels of the captured image, A projector, wherein when the ratio of the extracted pixels to the pixels of a captured image is less than a predetermined ratio, the projection plane is determined to be suitable for projection. The projector according to claim 1, wherein
The determination means includes
Among the pixels of each photographed image obtained by photographing the projection surface obtained by projecting the pixel primary color image of the projector for each single color, the maximum luminance value among all the pixels of each photographed image and a predetermined minimum reflectance When a pixel having a luminance smaller than a value obtained by multiplying is extracted and the ratio of the extracted pixel to the pixel of the photographed image is less than a predetermined ratio for all pixel primary color images, the projection plane is suitable for projection. It is determined that the projector is present.

Images