JP4176058B2 - Projector focus adjustment method and projector - Google Patents

Description

  The present invention relates to a projector capable of automatically adjusting the focus of an image to be projected, and a method for adjusting the focus of such a projector.

  In the field of presentation or video projection, a projector is used that receives image data from a personal computer or a video playback device and projects an image based on the image data onto an external screen. Such a projector forms an image based on image data on a projection device such as a liquid crystal panel or DMD (Digital Micromirror Device), and projects the image on the projection device onto an external screen by light from an internal light source. It has a configuration. In addition, such a projector may project a color image by projecting an image in which R (red), G (green), and B (blue) colors are combined, or by projecting RGB images in a time division manner. it can.

  Unless the screen and the projector are fixed together, such as in a theater, the relative position between the screen and the projector is usually variable, so that the projector can project an appropriate image on the screen. It is necessary to adjust the projection range, projection shape, focal length, and the like. A conventional technique for adjusting a projector is disclosed in Patent Document 1, for example. The projector projects a predetermined image (hereinafter referred to as a test pattern) on a screen and images the test pattern projected on the screen with a camera. The projector adjusts the projection range of the image so that the size of the captured test pattern falls within an appropriate range on the screen, and changes the projected shape of the image so that the captured test pattern has a predetermined shape. adjust.

  The projector can adjust the focal length using the test pattern. FIG. 9 is a schematic diagram illustrating an example of a test pattern for adjusting the focal length. FIG. 9 shows an example of a test pattern composed of a plurality of vertical straight lines. For example, the projector adjusts the focal length based on a change in the image signal intensity indicating the brightness of each pixel constituting the captured test pattern in the horizontal direction (a direction perpendicular to the vertical straight line of the test pattern). Specifically, the number of pixels where the difference in signal intensity between adjacent pixels in the horizontal direction of the test pattern captured while changing the focal length is greater than or equal to a predetermined threshold is counted, and the focal length with the largest count value is optimized. It was adjusted as the focal length.

As described above, the conventional projector can automatically adjust the projection range, projection shape, focal length, and the like of the image by projecting the test pattern.
JP 2000-241874 A

  By the way, the brightness of the image projected on the screen changes depending on the distance between the projector and the screen, the light intensity at which the projector projects an image, the light reflectance of the screen, etc. The luminance signal indicating the brightness of each pixel of the image also changes. Therefore, the image projected from the projector to the screen may become brighter or darker as a whole. In other words, the contrast of the projected image may be strong or weak. For this reason, when the conventional focal length adjustment as described above is performed, when the number of pixels in which the difference in signal intensity between adjacent pixels in the horizontal direction of the captured test pattern is greater than or equal to a predetermined threshold value is very large, On the contrary, it may be very small. In such a case, since the range that can be determined as the optimum focal length becomes wide, there is a possibility that the adjustment accuracy of the focal length is lowered.

  The present invention has been made in view of such circumstances, and its purpose is to adjust the focal length regardless of the overall brightness of the image projected on the screen. It is an object of the present invention to provide a method for adjusting the focus of a projector capable of performing the above adjustment with high accuracy, and such a projector.

A projector focus adjustment method according to the present invention includes a projection unit that projects an image onto a screen and an imaging unit that captures an image projected onto the screen, and is used for focus adjustment that combines a bright part and a dark part. In a focus adjustment method for a projector that performs focus adjustment based on an image of a test pattern in a captured image captured by the imaging unit by projecting a test pattern onto the screen by the projection unit, in the captured image captured by the imaging unit The brightness is measured in units of pixels in the direction crossing the boundary between the bright part and the dark part of the test pattern image, and the absolute value of the difference in brightness between adjacent pixels is calculated from the measurement results. Calculate as the difference value, obtain the maximum value of the difference value of the calculation result, based on the measurement result at each of a plurality of focal positions and the difference value of the calculation result, The maximum value of the difference value is acquired at each of the plurality of focal positions, a threshold is set based on the acquired maximum value of the difference value, and the calculated threshold value and the calculated difference value in pixel units And the number of pixels whose difference value is equal to or greater than the set threshold value is counted from the comparison result. Based on the comparison result and the counting result at each of a plurality of focal positions, The counting is performed at each focal position, and the focal position corresponding to the largest value among the counting results is determined as the optimum focal position.

The projector according to the present invention includes a projection unit that projects an image onto a screen and an imaging unit that captures an image projected onto the screen, and a test pattern for focus adjustment that combines a bright part and a dark part. In the projector that performs focus adjustment based on the image of the test pattern in the captured image that is projected onto the screen by the projection unit and captured by the imaging unit, the brightness of the test pattern in the captured image captured by the imaging unit The measurement means for measuring the brightness in units of pixels in the direction crossing the boundary between the dark part and the dark part, and the absolute value of the difference in brightness between the adjacent pixels in units of pixels from the measurement result by the measurement means A difference value calculating means for calculating as a value, a maximum difference value acquiring means for acquiring a maximum value of the difference values calculated by the difference value calculating means, and a plurality of focus positions, respectively. Based on the measurement result by the measurement means and the calculation result by the difference value calculation means, the maximum difference value acquisition by focus position that causes the maximum difference value acquisition means to acquire the maximum difference value at each of the plurality of focus positions. Means, threshold setting means for setting a threshold based on the maximum difference value acquired by the focus position maximum difference value acquiring means, the threshold set by the threshold setting means, and the difference value calculating means A comparison unit that compares a difference value in pixel units, a counting unit that counts the number of pixels in which each difference value is equal to or greater than a threshold set by the threshold setting unit, and a plurality of focal points Based on the comparison result by the comparison unit and the count result by the counting unit at each position, the focus unit performs the counting at each of the plurality of focal positions. And a focus position setting means for performing focus adjustment with a focus position corresponding to the largest value among the count values counted at a plurality of focus positions as an optimum focus position. .

In such a projector focus adjustment method and projector according to the present invention, the brightness is measured in units of pixels in a direction crossing the boundary between the bright part and the dark part of the image of the test pattern in the captured image captured by the imaging unit. From this measurement result, the absolute value of the difference in brightness between adjacent pixels in pixel units is calculated as the difference value, the maximum value of the calculated difference value is acquired, and the maximum value of the acquired difference value A threshold is set based on Then, the threshold value set as described above is compared with the difference value in units of pixels, and from this comparison result, the number of pixels in which each difference value is equal to or greater than the threshold value is counted, and at each of the plurality of focal positions. The focus position corresponding to the largest value among the count results is determined as the optimum focus position, and the focus adjustment is performed.
In such a projector focus adjustment method and projector according to the present invention, in addition to the above-described invention, when setting the threshold value, the largest value among the maximum values of the difference values at each of the plurality of focus positions is obtained. The threshold value is set according to the result.

  Furthermore, the projector focus adjustment method and the projector according to the present invention are characterized in that, in both the above-described inventions, the test pattern is a pattern in which a bar-shaped dark portion is set with a bright portion as a background.

  In such a projector focus adjustment method and projector according to the present invention, since the test pattern has a bar-shaped dark portion set with a bright portion as a background, a change in luminance becomes clear on the captured image.

  Furthermore, the projector focus adjustment method and the projector according to the present invention are characterized in that, in both of the above inventions, the test pattern is a pattern in which a bar-shaped bright portion is set with a dark portion as a background.

  In such a projector focus adjustment method and projector according to the present invention, since the test pattern is set with a bar-shaped bright portion with a dark portion as a background, a change in luminance becomes clear on the captured image.

According to the projector focus adjustment method and the projector according to the present invention, the absolute value of the difference in luminance value between adjacent pixels with respect to each pixel of the line traversing the image of the test pattern, instead of setting the threshold value as a fixed value. Since the threshold value is set according to the maximum value, an appropriate threshold value is set according to the brightness of the image projected on the screen, in other words, the contrast. Therefore, appropriate focus adjustment is performed regardless of the brightness of the image projected on the screen.

  According to the projector focus adjustment method and the projector according to the present invention, in addition to the above-described invention, when the threshold value is set, the largest value among the maximum values of the difference values at each of the plurality of focus positions is obtained. Since the threshold is set according to the result, more optimal focus adjustment can be performed.

  Furthermore, according to the focus adjustment method and projector of the projector according to the present invention, in addition to the above-described invention, the test pattern has a bar-shaped dark portion (or bright portion) set against a bright portion (or dark portion) as a background. Since the luminance change is clear on the captured image, more appropriate focus adjustment can be performed.

Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof.
FIG. 1 is a block diagram showing an internal configuration example of a projector according to the present invention. Arrows in the figure indicate data or control signals, and white arrows indicate light. The projector 1 includes a light source 18 such as a xenon lamp or an ultra-high pressure mercury lamp, a condensing optical system 17 that collects light from the light source 18, a projection device 14 that forms an image, and an image on the projection device 14 that is enlarged. And a projection optical system 13 for projecting onto an external screen 3.

  The projector 1 irradiates the projection device 14 with light from the light source 18 through the condensing optical system 17 and projects the light reflected on the projection device 14 that has formed an image through the projection optical system 13, thereby causing the projection device 14. The upper image is projected onto the screen 3. In addition, it is good also as a structure which projects an image by making the light from the light source 18 permeate | transmit instead of reflecting on the projection device 14. FIG.

  The condensing optical system 17 includes a color filter, a lens, a prism, or the like, and performs condensing / polarization / color separation of light from the light source. The projection device 14 includes one or a plurality of liquid crystal panels or DMD (Digital Micromirror Device), and forms RGB images. The projection optical system 13 includes a projection lens for projecting an image, a focus adjustment lens (hereinafter referred to as a focus lens) for adjusting the focus of the image projected by the projection lens, and a zoom lens for adjusting the size. And a motor for moving the focus lens and zoom lens along the optical axis of the projection lens, a drive circuit for driving the motor, and the like. Note that the projection optical system 13 may have a configuration including a color synthesis optical system that synthesizes RGB images.

  The projector 1 also receives a communication unit 16 that receives image data transmitted from an external transmission device 2 such as a personal computer or a video reproduction device, processes the image data received by the communication unit 16, and generates an image based on the image data. Is formed on the projection device 14. Therefore, an image based on the image data transmitted from the transmission device 2 is projected onto the screen 3.

  The projector 1 also includes a camera 12 that captures an image projected on the screen 3. The camera 12 includes a CCD that captures an image, and an AD conversion unit that AD converts an analog image signal representing the image captured by the CCD into a digital image signal. The projector 1 further includes a control unit 11 that controls the operation of the entire projector 1. The control unit 11 includes a CPU that performs calculations, a flash memory that stores programs, and the like. The camera 12 outputs a digital image signal representing the captured image to the control unit 11 via the focus adjustment value determination unit 20, and the control unit 11 projects the projection optical system based on the image signal input from the camera 12. 13 and the image processing unit 15 are controlled. The control unit 11 adjusts the projection range (size) or focal length of the image projected by the projector 1 by controlling the operation of the drive circuit of the projection optical system 13. In addition, the control unit 11 controls the processing of causing the projection device 14 to form an image by the image processing unit 15, thereby controlling the content of the image to be projected, the shape of the image, the hue, or the projection luminous intensity of the image.

  The focus adjustment value determination unit 20 is a circuit for calculating a threshold value for classifying a difference in signal intensity (for example, luminance value) between adjacent pixels during focus adjustment, as will be described later. Although the function of the focus adjustment value determination unit 20 will be described later, the control unit 11 can substitute for software.

  Next, the focus adjustment method of the projector 1 according to the present invention, that is, the focus adjustment method of the projector according to the present invention will be described with reference to the flowcharts of FIGS. Various adjustments other than the focus adjustment are performed in the same manner as in the past.

  FIG. 2 is a flowchart showing a processing procedure of a main routine for focus adjustment performed by the projector 1 of the present invention. The control unit 11 controls the image processing unit 15 to cause the projection device 14 to form a test pattern as shown in FIG. 9 similar to the conventional example described above and project the test pattern onto the screen 3 (S11). The control unit 11 causes the camera 12 to capture an image of the test pattern projected on the screen 3 (S12). The camera 12 generates a digital image signal representing a captured image obtained by capturing the test pattern, and inputs the digital image signal to the focus adjustment value determination unit 20 (step S13).

  FIG. 6 is a schematic diagram illustrating an image obtained by capturing the test pattern projected onto the screen 3 with the camera 12. Reference numeral 12I indicates an image captured by the camera 12, and an image S of the screen 3 is captured. Further, a test pattern image TP is captured inside the image S of the screen 3. Note that the range indicated by the reference sign PA in the image 12I is an image area used by the focus adjustment value determining unit 20 as will be described later, and crosses the image TP of the test pattern indicated by the reference sign L in the horizontal direction. The focus adjustment value determination unit 20 calculates a threshold value for each pixel of one line.

  In other words, the focus adjustment value determination unit 20 is optimal based on the signal intensity (for example, luminance value) of each pixel of the line L that crosses the test pattern image TP in the horizontal direction in the digital image signal input from the camera 12. The process for obtaining the focus adjustment value is performed (step S14). Then, the focus adjustment is performed by moving the focus lens by controlling the drive circuit of the projection optical system 13 in accordance with the optimum focus adjustment value obtained in step S14 (step S15).

  The procedure for obtaining the optimum focus adjustment value executed by the focus adjustment value determination unit 20 in step S14 is shown in the flowchart of the subroutine shown in FIG. Specifically, as shown in FIG. 3, the process for obtaining the optimum focus adjustment value uses a process for setting the threshold value TH (step S21) and the threshold value TH obtained by the process in step S21. And processing for obtaining the maximum focus adjustment value (step S22).

  FIG. 4 is a flowchart showing a processing procedure of a subroutine for setting the threshold value TH in step S21. First, the control unit 10 first moves the focus lens to an initial position (for example, one of the moving end portions) (step S30). ), Causing the focus adjustment value determination unit 20 to execute the following processing.

The focus adjustment value determination unit 20 initializes the counter i to “1” (step S31), and the i-th pixel for a predetermined line L within the predetermined range PA in the image 12I captured by the camera 12 illustrated in FIG. (initially the first pixel, i.e., the left end of the pixel) the absolute value dY _i of the difference between the luminance value Y _{i + 1} of the luminance values Y _i and the i + 1 pixel adjacent to the i-th pixel of the following formula (step S32).
dY _i = | Y _i −Y _{i + 1} |

FIG. 7 is a graph schematically showing the luminance value Y of the i-th pixel when the line L crosses two straight lines of the test pattern image TP in FIG. At the left end of the graph of FIG. 7, the black line portion of the test pattern image TP has low luminance (almost close to 0), and the portion between the two black lines of the test pattern image TP suddenly becomes high luminance. You can see that The luminance value of the i-th pixel is Y _i , and the luminance value of the i + 1-th pixel adjacent thereto is Y _{i + 1} . Therefore, with respect to the i-th pixel, the difference in luminance value with the adjacent pixel is “Y _i −Y _{i + 1} ”, and the absolute value is referred to as the difference value of the i-th pixel.

Next, the focus adjustment value determination unit 20 calculates the absolute value dY _i of the luminance value difference regarding the i th pixel obtained in step S32 and the luminance obtained for the previous pixel on the line L, that is, the i−1 pixel. The absolute value dY _i-1 of the difference between the values is compared (step S33), and the absolute value dY _i of the luminance value difference with the adjacent pixel related to the i-th pixel is the luminance with the adjacent pixel related to the i-th pixel. If it is larger than the absolute value dY _i-1 of the difference in values (YES in step S33), dY _max is updated with the absolute value dY _i of the luminance value difference with the adjacent pixel regarding the i-th pixel, and the updated dY _max is stored (step S34). If the determination result in step S33 is NO, the focus adjustment value determination unit 20 does not update dY _max .

  Next, the focus adjustment value determination unit 20 determines whether or not the counter i is m−1 (step S35). Until the counter i reaches m−1 (NO in step S35), the focus adjustment value determining unit 20 increments the counter i by “1” (step S36), and returns the process to step S32.

“M” is the number of pixels in the horizontal direction of the line L in the predetermined area PA in the image 12I captured by the camera 12. Therefore, when the counter i is m−1 (YES in step S35), the horizontal direction on the image captured by the camera 12 in a state where the focus lens is at one position (initial position at first) is set. This means that the absolute value dY _i of the difference in luminance value from the adjacent pixels has been obtained for all the pixels up to the last preceding pixel (m−1 pixel) of the line L.

As described above, the maximum value dY _max of the absolute value dY _i of the luminance value difference with the adjacent pixel for each pixel on the line L when the focus lens is at one position (initial position) is obtained. Then, the control unit 10 determines whether or not the focus lens is at the end position (end position opposite to the initial position) (step S37). At first, since the focus lens is not at the end position (NO in step S37), the control unit 10 controls the drive circuit of the projection optical system 13 to move the focus lens position to the end position side by a predetermined amount, for example, the focus lens. If the motor to be driven is a step motor, the step motor is rotated by one step to move the focus lens (step S38), and the process returns to step S31 described above.

The above processing is repeated while moving the focus lens sequentially by a predetermined amount until the focus lens reaches the end position (YES in step S37), so that the line L at all positions where the focus lens can be moved is displayed. The maximum value dY _max of the absolute value dY _i of the luminance value difference between adjacent pixels with respect to each pixel is obtained. Then, the focus adjustment value determining unit 20 sets the threshold value TH on the basis of the maximum value dY _max (step S39). Specifically, the threshold value TH is set as a value obtained by multiplying dY _max obtained as described above by a predetermined coefficient (“0.4” in the present embodiment). The above-mentioned predetermined count is not limited to “0.4”. In short, the threshold value is not fixed, but a value that varies according to dY _max is used as the threshold value. It is.

  When the threshold value TH is obtained in this way, the process is returned to the flowchart of the subroutine shown in FIG.

FIG. 8 is a graph showing the relationship between the focus adjustment value F corresponding to the position of the focus lens and the dY _max when the threshold value TH is changed. Here, FIG. 8B is a graph showing the result of obtaining dY _max as described above, and the horizontal axis corresponds to the number of movement steps of the step motor for moving the focus lens (the position of the focus lens). The vertical axis indicates the value of dY _max (the difference value of the luminance value that is digital data). More specifically, the curve of the graph shown in FIG. 8B shows the actual measurement value of dY _max at each movable position of the focus lens, and the maximum value is less than 60. I understand.

From the result of the actual measurement of dY _max , in the flowchart of the subroutine shown in FIG. 4 described above, the focus lens is moved to all movable positions and finally dY _max is obtained. the previously fixed to the approximate position may be obtained dY _max by performing the processing as described above only in the position of the one point. In other words, the threshold value is determined from the processing result at one focal position unless the focal position is shifted from the graph shown in FIG. Even if it is set, there is almost no problem in practical use.

From the above, it is not necessary to perform the process of obtaining dY _max at all the positions where the focus lens can move, and it may be performed only at one place in the substantially central portion of the range where the focus lens can move. Of course, more in order to perform accurate focusing, it is preferable to determine the dY _max at all positions possible movement of the focus lens, dY and compromise both in several places in the movable range of the focus lens _max And the threshold value TH may be set from the result.

As described above, since the threshold value TH is set for the predetermined line L in the image 12I captured by the camera 12, the control unit 10 next performs the process of step S22, that is, the process of obtaining the maximum focus adjustment value _Fmax. To the focus adjustment value determination unit 20. FIG. 5 shows a flowchart of the processing procedure of the subroutine.

First, the control unit 10 moves the focus lens to an initial position (for example, one of the moving end portions) (step S40), and causes the focus adjustment value determination unit 20 to execute the following processing. The focus adjustment value determination unit 20 initializes the counter i to “1” (step S41), and initializes the focus adjustment value F to “0” (step S42). The focus adjustment value determination unit 20 then selects all the pixels from the first pixel to the m−1th pixel of a predetermined line L (the same line as the line for which dY _max is obtained) in the image signal captured by the camera 12. the absolute value of the difference between the luminance value Y _i and the luminance value Y _{i + 1} of the pixel adjacent thereto, that is, the dY _i described above, to determine the magnitude of the threshold TH determined in as described above (step S43) .

  When the absolute value of the luminance value difference between adjacent pixels of the i-th pixel (i is a natural number of 1 to m) is equal to or greater than the threshold value TH (YES in step S43), the focus adjustment value determination unit 20 determines the focus adjustment value F. Is incremented by "1" (step S44). If the determination result in step S43 is NO, the focus adjustment value determination unit 20 does not increment the focus adjustment value F.

  Next, the focus adjustment value determination unit 20 determines whether or not the counter i is m−1 (step S45). Until the counter i reaches m−1 (NO in step S45), the focus adjustment value determination unit 20 increments the counter i by “1” (step S46), and returns the process to step S43. Note that “m” is the number of pixels in the horizontal direction of the line L in the predetermined area PA in the image 12I captured by the camera 12, as described above.

Therefore, if the counter i is m−1 (YES in step S45), the pixel immediately before the last line L in the horizontal direction L on the image captured by the camera 12 at the current focus lens position. absolute value dY _i of the difference between the luminance values of the adjacent pixels for (m-1-th pixel) until all pixels are compared threshold TH and magnitude, absolute value dY _i of the difference in luminance value between adjacent pixels than the threshold value TH Therefore, the focus adjustment value determining unit 20 stores the focus lens position and the focus adjustment value F in association with each other (step S47).

  As described above, since the focus adjustment value F for the line L when the focus lens is at one position (initial position) is obtained, the control unit 10 next determines that the focus lens is at the end position (opposite side from the initial position). Is determined (step S48). At first, since the focus lens is not at the end position (NO in step S48), the control unit 10 controls the drive circuit of the projection optical system 13 to move the focus lens position to the end position side by a predetermined amount, for example, the focus lens. If the motor to be driven is a step motor, the step motor is rotated by one step to move the focus lens (step S49), and the process returns to step S41 described above.

The process as described above is repeated while the focus lens is sequentially moved by a predetermined amount until the focus lens reaches the end position (YES in step S48), thereby regarding the lines L at all positions where the focus lens can be moved. Since the focus adjustment value F is obtained, the focus adjustment value determination unit 20 obtains the maximum value F _max among them (step S50), and returns to the flowchart of the subroutine of FIG. However, when the process returns from step S50 to the subroutine of FIG. 3, the process returns to the main routine of FIG. 2 and proceeds to the process of step S15.

In step S15, by controlling the operation of the driving circuit of the projection optical system 13 in accordance with the focus adjustment value F _max optimum was determined as described above, it performs focus adjustment by moving the focus lens.

As a result of the processing as described above, when the threshold value TH is set to “10” as a fixed value, the periphery of the maximum value of the focus adjustment value F is relatively as shown in the upper curve of FIG. Since it becomes a gentle trapezoid, it is not clear to what value the actual focus adjustment value F should be set. Even in such a case, the control unit 10 selects the maximum value, but there is no guarantee that the value thus selected is the optimum focus adjustment value. However, when the threshold TH is set to “20” (0.4 × dY _max ) based on dY _max from the fixed value “10” for the same dY _max , the lower curve in FIG. As described above, since the maximum value of the focus adjustment value F is a peak and the periphery thereof is relatively steep, it is possible to easily determine the optimum focus adjustment value F. The value determined in this way is considered to be a value that is sufficiently guaranteed to be the optimum focus adjustment value.

  As described in detail above, in the present invention, the threshold value is not set to a fixed value, but the absolute value of the difference in luminance value between adjacent pixels with respect to each pixel of the line L crossing the image TP of the test pattern is obtained. Since the threshold value is set according to the maximum value, an appropriate threshold value is set according to the brightness of the image projected on the screen 3, in other words, the contrast. Accordingly, appropriate focus adjustment is performed regardless of the brightness of the image projected on the screen 3.

  In the above-described embodiment, the test pattern is a pattern in which a bar-shaped dark part is arranged with the bright part as the background, but conversely, it may be a pattern in which the bar-shaped bright part is arranged with the dark part as the background. In addition to such patterns, any test pattern of any shape can be used as long as it is possible to determine the luminance value of each pixel on the line that crosses the boundary between the bright and dark areas on the test pattern image TP. Is possible.

  In the above embodiment, the measurement means, the difference value calculation means, the maximum difference value acquisition means, the focus position maximum difference value acquisition means, the threshold setting means, the comparison means, the counting means, the focus position counting means, the focus The position setting means and the like adopt a configuration realized as software means executed by the control unit 10 or the focus adjustment value determination unit 20, but each is realized as hardware means, specifically as a hardware circuit. Of course, it is also possible.

  Furthermore, if the luminance value Y of each pixel is stored in the memory device in the subroutine shown in FIG. 4, the luminance value of each pixel stored in the memory device can be used in the subroutine shown in FIG. become.

It is a block diagram which shows the internal structural example of the projector of this invention. It is a flowchart which shows the procedure of the process of the focus adjustment which the projector of this invention performs. It is a flowchart which shows the procedure of the process of the focus adjustment which the projector of this invention performs. It is a flowchart which shows the procedure of the process of the focus adjustment which the projector of this invention performs. It is a flowchart which shows the procedure of the process of the focus adjustment which the projector of this invention performs. It is a schematic diagram which shows the image which imaged the test pattern projected on the screen from the projector of this invention with the camera. 7 is a graph schematically showing pixel luminance values when a predetermined line crosses two straight lines of an image of a test pattern in FIG. 6. It is a graph showing the relationship between the value and dY _max focus adjustment value corresponding to the position of the focus lens in the case of changing the threshold value. It is a schematic diagram which shows the example of the test pattern for adjusting a focal distance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Projector 3 Screen 11 Control part 12 Camera 13 Projection optical system 14 Projection device 15 Image processing part 20 Focus adjustment value determination part S Screen image 12I Camera image TP Test pattern image L line

Claims (6)

A projection unit configured to project an image onto a screen; and an imaging unit configured to capture an image projected onto the screen. A test pattern for focus adjustment combining a bright part and a dark part is projected onto the screen by the projection unit. In a focus adjustment method for a projector that performs focus adjustment based on an image of a test pattern in a captured image captured by the imaging unit.
The brightness is measured in units of pixels in a direction crossing the boundary between the bright part and the dark part of the image of the test pattern in the captured image captured by the imaging unit,
From the measurement result, the absolute value of the difference in brightness between adjacent pixels in pixel units is calculated as a difference value,
Obtain the maximum difference value of the calculation result,
Based on the difference value between the measurement result and the calculation result at each of a plurality of focal positions, to obtain the maximum value of the difference value at each of the plurality of focal positions,
A threshold is set based on the maximum value of the acquired difference value,
The set threshold value is compared with the calculated difference value in pixel units,
From the comparison result, count the number of pixels in which each difference value is equal to or greater than the set threshold value,
Based on the comparison result and the counting result at each of a plurality of focal positions, the counting is performed at each of the plurality of focal positions,
A focus adjustment method for a projector, wherein a focus position corresponding to the largest value among the counting results is determined as an optimum focus position. 2. The projector focus adjustment method according to claim 1, wherein the test pattern is a pattern in which a bar-shaped dark portion is set with a bright portion as a background. 2. The projector focus adjustment method according to claim 1, wherein the test pattern is a pattern in which a bar-shaped bright portion is set with a dark portion as a background. A projection unit configured to project an image onto a screen; and an imaging unit configured to capture an image projected onto the screen. A test pattern for focus adjustment combining a bright part and a dark part is projected onto the screen by the projection unit. In the projector that performs focus adjustment based on the image of the test pattern in the captured image captured by the imaging unit,
A measuring unit that measures brightness in units of pixels in a direction crossing a boundary between a bright part and a dark part of an image of a test pattern in a captured image captured by the imaging unit;
A difference value calculating means for calculating an absolute value of a difference in brightness between adjacent pixels in pixel units as a difference value from the measurement result by the measuring means;
Maximum difference value acquisition means for acquiring the maximum value of the difference values calculated by the difference value calculation means;
A focal position that causes the maximum difference value acquisition means to acquire the maximum value of the difference value at each of the plurality of focal positions, based on the measurement result by the measurement means and the calculation result by the difference value calculation means at each of the plurality of focal positions. Another maximum difference value acquisition means;
Threshold setting means for setting a threshold based on the maximum value of the difference values acquired by the focal position maximum difference value acquiring means;
A comparison means for comparing the threshold set by the threshold setting means with the difference value in pixel units calculated by the difference value calculation means;
Counting means for counting the number of pixels, each difference value being equal to or greater than the threshold set by the threshold setting means , from the comparison result by the comparison means;
Based on the comparison results by the comparison means at each of a plurality of focal positions and the counting results by the counting means, the counting means for each focal position that causes the counting means to perform the counting at each of the plurality of focal positions;
A projector comprising: a focus position setting unit that performs focus adjustment with a focus position corresponding to the largest value among count values counted at a plurality of focus positions as an optimum focus position. 5. The projector according to claim 4 , wherein the test pattern is a pattern in which a bar-shaped dark part is set with a bright part as a background. The projector according to claim 4 , wherein the test pattern is a pattern in which a bar-like bright part is set with a dark part as a background.

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