JP3852454B2 - Projector and exposure adjustment method - Google Patents

Description

  The present invention relates to a projector that displays an image by projecting projection light onto a projection object such as a screen, and in particular, a zoom lens capable of changing the size of a projection light range onto which projection light is projected, The present invention relates to a projector including an imaging unit capable of photographing the projection light range.

  In recent projectors, a zoom lens is provided in a projection lens, the zoom lens is driven, and the zoom position of the zoom lens is changed to freely change the size of the projection light range formed on the screen. Things are known.

  When such a projector is installed in front of the screen, zoom adjustment and keystone correction are performed in advance in the projector so that an image is appropriately displayed on the screen by the projection light projected from the projector onto the screen. Various adjustments such as focus adjustment are required.

  However, in the case of a portable projector, the relative position with respect to the screen may change every time the projector is installed. Therefore, the user must make various adjustments as described above. It was complicated.

  Therefore, conventionally, for example, as described in Patent Document 1 below, when a projector is provided with a monitor camera and the projector is installed in front of the screen, first, the projector is used for adjustment on the screen. A pattern image is projected and displayed, a screen for displaying the pattern image is photographed by a monitor camera, the photographed image is analyzed, and the above-described various adjustments are automatically performed based on the analysis result.

  In general, a monitor camera includes a CCD (Charge Coupled Device) that converts incident light into an electrical signal, and the like, in order to set the overall brightness of a captured image to a preset value (exposure target value). It has a function (automatic exposure) for changing the shutter speed, gain (sensitivity), aperture, and the like.

FIG. 7 is an explanatory diagram for explaining the effect of automatic exposure of a conventional monitor camera. In FIG. 7, the upper part shows a screen on which the adjustment pattern image is displayed, the middle part shows a photographed image obtained by photographing the screen with a monitor camera, and the bottom part shows a central horizontal line ( A value representing the brightness of each pixel arranged along the broken line) is shown. (A) shows the normal state of the projector, and (B) shows the state when the projector is set to low brightness.
A value representing the brightness of each pixel in the captured image is hereinafter referred to as a gradation value. Such a gradation value is a value obtained from the image signal of the captured image output from the monitor camera (CCD module).

  In FIG. 7, the adjustment pattern image is a white image on the entire surface, and as shown in the upper part, the range of the white portion displayed as the pattern image on the screen is the above-described projection light range.

  The captured image obtained by capturing with the monitor camera is as shown in the middle row.

  In the lower part, the horizontal axis corresponds to the position of each pixel on the central horizontal line of the captured image, and the vertical axis represents the gradation value of each pixel.

  In the projector, when the light source lamp is set to a low luminance setting, the luminance of the projection light projected from the projector is lower than in the normal case. Therefore, as shown in FIG. 7B, the brightness of the pattern image displayed on the screen is also darker than in the normal state of FIG. However, when the pattern image is taken with a monitor camera with automatic exposure, the shutter speed, gain, aperture, etc. are adjusted so that the overall brightness of the shot image is appropriate even when the subject is dark. Then, as shown in FIG. 7B, the brightness of the pattern image is not different from the normal time of (A). Accordingly, in the photographed image, the black portion (that is, the portion outside the projection light range) is so dark that it can be ignored. Therefore, the gradation value of each pixel in the black portion can be regarded as 0, whereas the white portion (that is, the pattern image) The gradation value of each pixel in (part) remains almost the same as the desired gradation value Lt.

  In this way, by operating the automatic exposure function in the monitor camera, even if the brightness of the light source lamp is set low in the projector and the brightness of the pattern image displayed on the screen becomes dark, the white portion ( That is, the gradation value of each pixel in the pattern image portion) can be substantially maintained at the desired gradation value Lt as in the normal case. This is not limited to the low luminance setting, and the same applies to the case where the luminance of the light source lamp deteriorates with age and the luminance decreases.

JP 2000-241874 A

  However, in such a projector having a zoom lens and a monitor camera, when the zoom lens zoom position is changed to change the size of the projection light range on the screen, the monitor camera is automatically exposed. There were the following problems.

  FIG. 8 is an explanatory diagram for explaining a problem caused by automatic exposure of the monitor camera when the zoom position in the related art is changed. In FIG. 8, as in FIG. 7, the upper row shows the screen on which the adjustment pattern image is displayed, the middle row shows the captured image of the screen, and the lower row shows the gradation value of the pixel in the captured image. (A) shows the state when the zoom position of the zoom lens is set to the intermediate position, (B) shows the state when the zoom position is set to the wide side, and (C) shows the zoom position. The state when the position is set to the tele side is shown.

  In the projector, when the zoom position of the zoom lens is set to the wide side, the area of the projection light range on the screen is wider than the intermediate position of (A) as shown in the upper part of FIG. The displayed pattern image is also enlarged. Therefore, when the pattern image is photographed by the monitor camera, the area of the white portion (that is, the pattern image portion) in the photographed image is at an intermediate position of (A) as shown in the middle part of FIG. The area of the black part (that is, the part outside the projection light range) becomes narrower.

  At this time, if the shooting is performed with automatic exposure, the overall brightness of the shot image is calculated as the exposure calculation value, and the shutter speed and gain are set so that the exposure calculation value becomes equal to the preset exposure target value. And aperture are controlled. Here, the overall brightness of the photographed image is also the sum of the amount of light detected by each pixel in the CCD converted into an electric signal, and the value is the gradation value of each pixel in the photographed image. It is proportional to the average value of. Therefore, normally, the average value of the gradation values of all the pixels in the captured image is used as the exposure calculation value.

  On the other hand, since the exposure target value is a preset constant value, as shown in FIG. 8A, when the zoom position is the intermediate position, the calculated exposure value matches the exposure target value. As described above, when the zoom position is set to the wide side and the area of the white portion in the photographed image is widened, the average value of the gradation values of all pixels, that is, the exposure calculation, is equivalent to the spread of the area. The value rises above the exposure target value. As a result, if the shutter speed, gain, aperture, etc. are changed so that the automatic exposure works and the calculated exposure value becomes equal to the exposure target value, the average value of the gradation values of all the pixels in the captured image will decrease. . As described above, in the photographed image, the black portion is so dark that it can be ignored, and the gradation value of each pixel in the black portion can be regarded as 0. Therefore, the average value of the gradation values of all the pixels decreases. As shown in the lower part of B), the gradation value of each pixel in the white portion is none other than the desired gradation value Lt.

  On the contrary, when the zoom position of the zoom lens is set to the tele side, the area of the projection light range on the screen is narrower than the middle position of (A) as shown in the upper part of FIG. The displayed pattern image is also reduced. Therefore, when the pattern image is photographed by the monitor camera, the area of the white portion (that is, the pattern image portion) in the photographed image is at an intermediate position of (A) as shown in the middle part of FIG. In comparison, the area becomes narrower and the area of the black portion (that is, the portion outside the projection light range) becomes wider.

  As described above, when the area of the white portion in the photographed image is narrowed, the average value of the gradation values of all the pixels, that is, the calculated exposure value is lower than the exposure target value by the narrowness of the area. . As a result, if the shutter speed, gain, aperture, etc. are changed so that the automatic exposure works and the calculated exposure value is equal to the exposure target value, the average value of the gradation values of all the pixels in the captured image increases, and as a result As shown in the lower part of FIG. 8C, the gradation value of each pixel in the white portion is higher than the desired gradation value Lt.

  As described above, conventionally, when the zoom position of the zoom lens is set to the wide side and the area of the projection light range on the screen is widened, in the captured image due to the automatic exposure of the monitor camera. When the gradation value of each pixel in the white portion falls below the desired gradation value Lt, and conversely, when the area of the projection light range becomes narrower on the tele side, the gradation value of each pixel in the white portion In this case, the average value of the gradation values in the white portion cannot be maintained at the desired gradation value Lt.

  Accordingly, when the average value of the gradation values of the white portion in the photographed image deviates from the desired gradation value Lt due to the change in the zoom position of the zoom lens, the photographed image is thereafter changed as described above. When analysis is performed and various adjustments are automatically performed based on the analysis results, there is a problem that appropriate adjustment cannot be performed depending on the content of the adjustment.

  Such a problem is not limited to the case where the adjustment pattern image is entirely white, but is also a case where the adjustment pattern image is a specific color other than white (for example, green) or a part of the adjustment pattern image. Can also occur.

  Therefore, the object of the present invention is to solve the above-mentioned problems of the prior art, and even if the zoom position of the zoom lens changes, the average gradation value of the specific color portion represented by the specific color in the captured image An object of the present invention is to provide a technique capable of maintaining a value substantially at a desired gradation value.

In order to achieve at least a part of the above object, a projector according to the present invention is a projector that projects projection light onto a projection object and displays an image,
A zoom lens capable of changing the size of the projection light range onto which the projection light is projected;
A control unit;
An imaging unit for imaging the projection object;
An exposure calculation value is calculated from a captured image captured by the imaging unit, and exposure adjustment is performed in the imaging unit so that the calculated exposure calculation value is substantially equal to an exposure target value set by the control unit. An imaging control unit;
With
The control unit obtains a photographed image photographed by the photographing unit, derives a parameter related to the area of a specific color portion represented by a specific color in the obtained photographed image, and depends on the derived parameter Thus, the gist is to change the exposure target value to be set in the imaging control unit.

  Thus, in the projector of the present invention, the exposure target value is changed according to the parameter related to the area of the specific color portion in the captured image. Accordingly, for example, when the zoom position is set to the wide side and the area of the specific color portion in the photographed image is widened, the exposure calculation value calculated from the photographed image is increased in the imaging control unit by the extent of the area. However, for example, if the exposure target value is changed so as to increase as the parameter increases as the area expands, the exposure is calculated so that the calculated exposure value becomes equal to the exposure target value as automatic exposure. Even if the adjustment is performed, the average value of the gradation values of all the pixels in the photographed image does not decrease, so that the average value of the gradation values of the specific color portion can be substantially maintained at the desired gradation value. When the zoom position is set to the tele side and the area of the specific color portion in the photographed image is narrowed, the exposure calculation value calculated from the photographed image is reduced in the imaging control unit by the narrowness of the area. However, for example, if the exposure target value is changed so as to decrease as the parameter becomes smaller according to the narrowness of the area, the calculated exposure value becomes equal to the exposure target value as automatic exposure. Even if exposure adjustment is performed, the average value of the gradation values of all the pixels in the photographed image does not increase, so that the average value of the gradation values of the specific color portion can be substantially maintained at the desired gradation value.

  In the claims and the specification, the parameters related to the area of the specific color portion in the photographed image include the area itself, the pixels constituting the specific color portion, that is, the number of pixels of the specific color pixel, the specific The length of the shape constituting the color portion (for example, the length of one side if the specific color portion is rectangular) is included.

  In the projector according to the aspect of the invention, the control unit may determine that the average value of the gradation values of the specific color portion in the captured image captured by the imaging unit is based on the derived parameter regardless of the change of the parameter. An exposure target value that is substantially equal to the tone value may be calculated, and the calculated exposure target value may be set in the imaging control unit.

In the projector according to the aspect of the invention, the average value of the gradation value of the specific color portion in the photographed image photographed by the photographing unit is approximately equal to the desired gradation value regardless of the change of the parameter. Prepare an exposure target value table in which exposure target values are set in advance so that they are equal,
The control unit refers to the exposure target value table based on the derived parameter, derives an exposure target value corresponding to the parameter, and sets the derived exposure target value in the imaging control unit. Also good.

  Thus, based on the derived parameter, the exposure target value is calculated or derived from the exposure target value table, and the obtained exposure target value is set in the imaging control unit, thereby deriving the parameter. The exposure target value can be changed according to the zoom level, and even if the zoom position is changed, the average value of the gradation values of the specific color portion in the photographed image can be substantially maintained at the desired gradation value.

  The present invention is not limited to the above-described aspects of the apparatus invention such as a projector, but can also be realized as an aspect of a method invention such as a method of performing exposure adjustment in an imaging unit of a projector.

Hereinafter, embodiments of the present invention will be described in the following order based on examples.
1. Projector configuration:
2. Image projection operation:
3. Exposure target value setting operation:
4). Effects of the embodiment:
5). Variations:
5-1. Modification 1:
5-2. Modification 2:
5-3. Modification 3:
5-4. Modification 4:

1. Projector configuration:
FIG. 1 is a block diagram showing a configuration of a projector as an embodiment of the present invention. The projector 100 is a portable projector, and as shown in FIG. 1, an A / D conversion unit 102, an imaging unit 104, an imaging control unit 105, a captured image memory 106, and an image processing unit 108. A liquid crystal panel driving unit 110, an illumination optical system 112, a liquid crystal panel 114, a projection optical system 118 including a zoom lens 116, a CPU 120, a zoom lens driving unit 124, a remote control control unit 126, and a remote control 128. It is equipped with.

  In FIG. 1, the CPU 120 is connected to only the imaging control unit 105, the captured image memory 106, the image processing unit 108, the liquid crystal panel driving unit 110, the zoom lens driving unit 124, and the remote control control unit 126 via a bus. In fact, it is connected to other components. The imaging unit 104 includes a CCD, and the imaging unit 104 and the imaging control unit 105 constitute a CCD module 130 as a monitor camera. In FIG. 1, the exposure target value table storage unit 107 will be described later.

  In this embodiment, the imaging unit 104 shown in FIG. 1 is the imaging unit described in the claims, the imaging control unit 105 is the imaging control unit described in the claims, and the zoom lens 116 is the zoom lens described in the claims. The CPU 120 corresponds to a control unit in the claims.

2. Image projection operation:
First, an image projection operation that is a normal operation in the projector 100 will be briefly described.

  In FIG. 1, when the user instructs the start of image projection using the remote controller 128, the remote controller 128 transmits the input instruction to the remote controller control unit 126 by wireless communication. The remote controller control unit 126 transmits an instruction from the remote controller 128 to the CPU 120 via the bus. Based on these instructions, the CPU 120 controls each component including the image processing unit 108 to perform an image projection operation.

  First, the A / D conversion unit 102 inputs an image signal output from a video player, a television, a DVD player, or the like, or an image signal output from a personal computer or the like, and converts these analog image signals into digital image signals. And output to the image processing unit 108. The image processing unit 108 adjusts the input digital image signal so that the display state of the image (for example, luminance, contrast, synchronization, tracking, color density, hue, etc.) is in a desired state, and the liquid crystal panel Output to the drive unit 110.

  The liquid crystal panel driving unit 110 drives the liquid crystal panel 114 based on the input digital image signal. Thereby, in the liquid crystal panel 114, the illumination light emitted from the illumination optical system 112 is modulated according to the image information. The projection optical system 118 is attached to the front surface of the housing of the projector 100, and projects the projection light modulated by the liquid crystal panel 114 onto a screen (not shown). Thereby, an image is projected and displayed on the screen.

3. Exposure target value setting operation:
Now, an exposure target value setting operation which is a characteristic part of the present invention in the projector 100 will be described in detail.

  Conventionally, as described above, the exposure target value used for automatic exposure of the monitor camera has always been constant, but in this embodiment, even if the zoom position of the zoom lens 116 changes, The exposure target value is changed according to the area of the white portion in the photographed image so that the average value of the gradation values of the white portion is substantially maintained at the desired gradation value.

  Therefore, when the user installs the projector 100 at a desired position in front of the screen and then turns on the power of the projector 100, the projector 100 projects and displays an adjustment pattern image on the screen in order to perform various adjustments. Let

  Specifically, the image processing unit 108 generates an adjustment pattern image and outputs it as a digital image signal to the liquid crystal panel driving unit 110. As described above, the liquid crystal panel driving unit 110 drives the liquid crystal panel 114 based on the input digital image signal, and the liquid crystal panel 114 converts the illumination light emitted from the illumination optical system 112 according to the image information. Modulate. The projection optical system 118 projects the projection light modulated by the liquid crystal panel 114 onto the screen via the zoom lens 116 and the like. As a result, the adjustment pattern image is displayed on the screen.

  In this embodiment, it is assumed that, for example, a white image is used as the adjustment pattern image. Therefore, on the screen, as shown in the upper part of FIG. 7 or FIG. 8, the range of the white portion displayed as the pattern image is the projection light range.

  After the pattern image is displayed on the screen in this way, the user then operates a zoom button (not shown) of the remote control 128 to adjust the size of the projection light range on the screen, and the zoom position. The remote control 128 transmits the input instruction to the remote control unit 126 by wireless communication. The remote controller control unit 126 transmits an instruction from the remote controller 128 to the CPU 120 via the bus. Based on the instruction, the CPU 120 controls the zoom lens driving unit 124 to drive the zoom lens 116 included in the projection optical system 118 and move the zoom position of the zoom lens 116. After that, when the projection light range on the screen reaches a desired size, when the user operates the zoom button of the remote control 128 to instruct to stop moving the zoom position, the CPU 120 performs the zoom lens based on the instruction. The drive unit 124 is controlled to stop the movement of the zoom position of the zoom lens 116.

  Further, the CPU 120 reads and executes an exposure target value setting processing program from a memory (not shown). Specifically, the CPU 120 controls each component including the imaging controller 105 according to the processing procedure shown in FIG.

  FIG. 2 is a flowchart showing a processing procedure of exposure target value setting processing in the projector of FIG.

When the processing shown in FIG. 2 is started, the CPU 120 reads an initial value from a memory (not shown), sets the initial value as the exposure target value R in the imaging control unit 105 (step S102), and then performs imaging control. The unit 105 is instructed to shoot (step S104).
Thereby, the imaging control unit 105 controls the imaging unit 104 to start imaging. The imaging unit 104 captures a screen on which a pattern image is displayed. At this time, the imaging control unit 105 calculates an average value Lccd of gradation values of all pixels from the captured image captured by the imaging unit 104 as an exposure calculation value, and the exposure calculation value is set by the CPU 120. The automatic exposure is performed by controlling the shutter speed, gain, aperture, and the like in the imaging unit 104 so as to be equal to the exposure target value R, that is, the initial value.

  Thus, when the image capturing unit 104 captures the screen on which the pattern image is displayed, the image capturing unit 104 outputs the captured image to the image processing unit 108 as a digital image signal. The image processing unit 108 performs a desired process on the input digital image signal, writes it in the captured image memory 106, and updates the contents.

  Next, the CPU 120 reads out a digital image signal from the photographed image memory 106 and applies a binarization process to obtain a monochrome binary photographed image. Then, the acquired captured image is analyzed to derive the area of the white portion in the captured image (step S106). Since the area of the white portion is proportional to the number of pixels of the white pixel, the CPU 120 can derive the area of the white portion by counting the number of pixels of the white pixel from the monochrome binary captured image.

  Next, the CPU 120 calculates an exposure target value according to the area of the derived white portion (step S108). Specifically, the exposure target value corresponding to the area of the white portion is calculated by the following method. Here, Sz is the area of the white portion in the derived photographed image, and R is the exposure target value to be calculated.

  FIG. 3 is an explanatory view showing a photographed image photographed by the CCD module 130. In the present embodiment, as described above, since an entire white image is used as the adjustment pattern image, in FIG. 3, the white portion in the captured image is a portion of the projection light range, and the black portion is projected. It is a part outside the light range.

Now, assuming that the average value of the gradation values of the white portion in the captured image is L, the area of the entire captured image is Sccd, and the average value of the gradation values of all the pixels in the captured image is Lccd, the average value Lccd is expressed by the formula ( 1).
Lccd = Sz × L / Sccd (1)
This is because in the captured image, the black portion (that is, the portion outside the projection light range) is so dark that it can be ignored, so that the gradation value of each pixel in the black portion can be regarded as zero.
Note that, for example, in a captured image, the gradation value of a pixel is not 0, but a portion having a certain threshold value or less is determined to be outside the projection light range, and the gradation value of the pixel in that portion is set to 0. You may make it calculate by replacing with.

On the other hand, in the automatic exposure, as described above, the average value Lccd of the gradation values of all the pixels in the photographed image is used as the exposure calculation value, and the shutter is set so that the exposure calculation value Lccd is equal to the exposure target value R. Speed, gain, aperture, etc. are controlled. Accordingly, by substituting R for Lccd in equation (1), exposure target value R is expressed by equation (2).
R = Sz × L / Sccd (2)

Therefore, in order to maintain the average value L of the gradation values of the white portion in the photographed image substantially at the desired gradation value Lt regardless of the change in the zoom position of the zoom lens 116, in Expression (2), L By substituting Lt for Eq. (3), the exposure calculation value R may be calculated according to Eq. (3) according to the area Sz of the white portion.
R = Sz × Lt / Sccd (3)

  Next, the CPU 120 sets the exposure target value R calculated according to the area Sz of the white portion in the imaging control unit 105 (step S110), and instructs the imaging control unit 105 to perform imaging (step S112). Then, the exposure target value setting process shown in FIG.

  At this time, since the imaging unit 104 is already shooting, the imaging control unit 105 causes the imaging unit 104 to continue shooting. Then, the imaging control unit 105 calculates the exposure calculation value from the captured image captured by the imaging unit 104, and the imaging unit so that the exposure calculation value becomes equal to the exposure target value R newly set by the CPU 120. Automatic exposure is performed by controlling the shutter speed, gain, aperture, and the like at 104.

  In this way, the captured image captured by the image capturing unit 104 is written as a digital image signal into the captured image memory 106 via the image processing unit 108 as described above, and the content is updated.

  Thereafter, the CPU 120 reads out a digital image signal from the captured image memory 106, acquires a captured image, and analyzes the captured image. Then, various adjustments are performed based on the analysis result.

4). Effects of the embodiment:
FIG. 4 is an explanatory diagram showing the gradation value of each pixel in the white portion of the photographed image when the zoom position is changed. 4, as in FIG. 7 or FIG. 8, the upper row shows the screen on which the adjustment pattern image is displayed, the middle row shows the captured image of the screen, and the lower row shows the gradation value of the pixel in the captured image. ing. (A) shows the state when the zoom position of the zoom lens is set to the intermediate position, (B) shows the state when the zoom position is set to the wide side, and (C) shows the zoom position. The state when the position is set to the tele side is shown.

  When the zoom position is the intermediate position, it is assumed that the gradation value of each pixel in the white portion in the captured image matches the desired gradation value Lt as shown in the lower part of FIG. In the present embodiment, the exposure target value R is changed according to the equation (3) according to the area Sz of the white portion in the captured image. Therefore, when the zoom position is set to the wide side and the area Sz of the white portion in the photographed image becomes wide, the average value Lccd of the gradation values of all pixels, that is, the calculated exposure value increases by the extent of the area Sz. However, the exposure target value R is also increased by the extent of the area Sz according to the equation (3). As a result, even if the shutter speed, gain, aperture, etc. are changed so that the automatic exposure works and the calculated exposure value is equal to the target exposure value, the average value of the gradation values of all pixels in the captured image does not decrease. In this embodiment, as shown in the lower part of FIG. 4B, the gradation value of each pixel in the white portion can be substantially maintained at the desired gradation value Lt.

  On the other hand, even when the zoom position is set to the tele side and the area Sz of the white portion in the photographed image is narrowed, the average value Lccd of the gradation values of all the pixels, that is, the exposure calculation, is equivalent to the narrowness of the area Sz Although the value is decreased, the exposure target value R is also decreased by the narrow variation of the area Sz according to the equation (3). As a result, even if the shutter speed, gain, aperture, etc. are changed so that the automatic exposure works and the calculated exposure value is equal to the target exposure value, the average value of the gradation values of all pixels in the captured image does not increase. In this embodiment, as shown in the lower part of FIG. 4C, the gradation value of each pixel in the white portion can be substantially maintained at the desired gradation value Lt.

  As described above, in this embodiment, even if the zoom position of the zoom lens 116 changes, the average value of the gradation values of the white portion in the captured image can be substantially maintained at the desired gradation value Lt.

5). Variations:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the scope of the invention.

5-1. Modification 1:
In the above-described embodiment, the exposure target value R corresponding to the area Sz of the white portion in the captured image is derived by the CPU 120 by calculation according to the equation (3), but the present invention is not limited to this. . For example, for each area Sz of the white portion, an exposure target value R corresponding to the area Sz is obtained in advance by calculation or actual measurement, and the result is stored as an exposure target value table in the exposure target value table indicated by a dotted line in FIG. Stored in the unit 107. Then, the CPU 120 reads out and refers to the exposure target value table from the exposure target value table storage unit 107, and may derive the exposure target value R corresponding to the area Sz from the derived area Sz of the white portion. .

  FIG. 5 is a graph showing the relationship between the area Sz of the white portion and the exposure target value R obtained from such an exposure target value table.

  In this example, the CCD included in the imaging unit 104 has 640 × 480 pixels, so the area Sccd of the entire captured image is 640 × 480. As the adjustment pattern image, a white image with an aspect ratio of 4: 3 is used, and when the zoom position is at the extreme end on the telephoto side, the area Sz of the white portion in the captured image is 300 × 225. On the other hand, when it is at the extreme end on the wide side, it is 600 × 450. Further, the desired gradation value Lt is 200.

  As shown in FIG. 5, the exposure target value R increases in proportion to the increase in the area Sz of the white portion in the captured image. That is, as the exposure target value R, the zoom position of the zoom lens 116 is on the telephoto side, and the smaller the area Sz of the white portion in the photographed image is, the smaller the value is, and the larger the area Sz is on the wide side. The value will increase.

5-2. Modification 2:
In the above-described embodiment, the exposure target value R is changed according to the area Sz of the white portion in the photographed image. However, the exposure target value R may not be the area Sz itself, and is a value related to the area Sz. It doesn't matter. For example, as shown in FIG. 3, in the captured image, when the length of the horizontal side of the white portion is w and the length of the vertical side is h, the area Sz of the white portion is expressed by Expression (4).
Sz = w × h
= K × w × w
= K × w ² (4)
Here, K is a coefficient corresponding to the aspect ratio. For example, when the aspect ratio of the pattern image is 4: 3, K = 3/4.

Therefore, by substituting Equation (4) for Sz in Equation (3), the exposure target value R is expressed by Equation (5).
R = K × w ² × Lt / Sccd (5)

  Therefore, in order to maintain the average value of the gradation value of the white portion in the photographed image substantially at the desired gradation value Lt regardless of the change in the zoom position of the zoom lens 116, the length of the horizontal side of the white portion is maintained. What is necessary is just to calculate the exposure calculation value R according to Formula (5) according to w.

  In addition, when the exposure target value R corresponding to the length w is obtained for each horizontal side length w and the exposure target value table is generated, the result is as shown in FIG.

  FIG. 6 is an explanatory view showing an example of such an exposure target value table. 6A is the contents of the exposure target value table, and FIG. 6B is a graph showing the relationship between the horizontal side length w of the white portion obtained from the exposure target value table and the exposure target value R. is there.

  The number of pixels of the CCD provided in the imaging unit 104, the contents of the adjustment pattern image, and the like are the same as those in FIG.

  As shown in FIG. 6, the exposure target value R increases monotonously as the length w of the horizontal side of the white portion increases. That is, as the exposure target value R, the zoom position of the zoom lens 116 is on the tele side, and the shorter the horizontal side length w of the white portion is, the smaller the value is, and on the wide side, the length w is long. The higher the value.

5-3. Modification 3:
In the above-described embodiment, a white image is used as the adjustment pattern image, but the present invention is not limited to this. Therefore, an appropriate pattern image can be used as the adjustment pattern image in accordance with the content of adjustment performed later.

  Further, as is clear from the above-described equation (3), the exposure target value R depends on the area Sz of the white portion in the captured image, but does not depend on the shape of the white portion. Therefore, as the adjustment pattern image, as long as the area of the white portion is the same, the exposure target value calculated according to the area Sz of the white portion in the captured image is whatever the shape of the white portion. R does not change.

  Further, for example, as the adjustment pattern image, the length of the white portion in the vertical direction is set to 1/3 as compared with the entire white image instead of the entire white image, thereby reducing the area of the white portion to 1 /. A horizontally long image of 3 may be used.

  Furthermore, for example, as the adjustment pattern image, other specific colors such as green and gray may be used instead of white.

5-4. Modification 4:
In the above-described embodiment, the imaging control unit 105 controls the shutter speed, gain, aperture, and the like in the imaging unit 104 to perform automatic exposure. However, the present invention is not limited to this, and the shutter speed is not limited to this. , Gain and aperture may be controlled to perform automatic exposure, or two or more may be combined and controlled to perform automatic exposure.

It is a block diagram which shows the structure of the projector as one Example of this invention. It is a flowchart which shows the process sequence of the exposure target value setting process in the projector of FIG. FIG. 4 is an explanatory diagram illustrating a captured image captured by a CCD module. It is explanatory drawing which shows the gradation value of each pixel of the white part in a picked-up image when a zoom position is changed. It is explanatory drawing which shows an example of the exposure target value table in a 1st modification. It is explanatory drawing which shows an example of the exposure target value table in a 2nd modification. It is explanatory drawing for demonstrating the effect by the automatic exposure of the monitor camera in the past. It is explanatory drawing for demonstrating the problem by the automatic exposure of a monitor camera at the time of changing the zoom position in the past.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Projector 102 ... A / D conversion part 104 ... Imaging part 105 ... Imaging control part 106 ... Captured image memory 107 ... Exposure target value table storage part 108 ... Image processing 110 ... Liquid crystal panel driver 112 ... Illumination optical system 114 ... Liquid crystal panel 116 ... Zoom lens 118 ... Projection optical system 120 ... CPU
124 ... Zoom lens drive unit 126 ... Remote control unit 128 ... Remote control 130 ... CCD module

Claims (5)

A projector that projects projection light onto a projection object to display an image,
A zoom lens capable of changing the size of the projection light range onto which the projection light is projected;
A control unit;
An imaging unit for imaging the projection object;
An exposure calculation value is calculated from a captured image captured by the imaging unit, and exposure adjustment is performed in the imaging unit so that the calculated exposure calculation value is substantially equal to an exposure target value set by the control unit. An imaging control unit;
With
The control unit obtains a photographed image photographed by the photographing unit, derives a parameter related to the area of a specific color portion represented by a specific color in the obtained photographed image, and depends on the derived parameter The exposure target value to be set in the imaging control unit is changed. The projector according to claim 1, wherein
Based on the derived parameter, the control unit has an average value of gradation values of a specific color portion in a captured image captured by the imaging unit substantially equal to a desired gradation value regardless of a change in the parameter. In such a projector, the exposure target value is calculated, and the calculated exposure target value is set in the imaging control unit. The projector according to claim 1, wherein
Corresponding to the parameter, an exposure target value such that an average value of gradation values of a specific color portion in a photographed image photographed by the photographing unit is substantially equal to a desired gradation value regardless of a change in the parameter. Prepare an exposure target value table with each set,
The control unit refers to the exposure target value table based on the derived parameter, derives an exposure target value corresponding to the parameter, and sets the derived exposure target value in the imaging control unit. Projector. A zoom lens capable of projecting projection light onto a projection object to display an image and changing the size of a projection light range onto which the projection light is projected, and an imaging unit for photographing the projection object A method of performing exposure adjustment in the imaging unit,
(A) obtaining a photographed image photographed by the photographing unit;
(B) deriving a parameter related to the area of a specific color portion represented by a specific color in the acquired captured image;
(C) deriving an exposure target value according to the parameter based on the derived parameter;
(D) calculating an exposure calculation value from a captured image captured by the imaging unit, and performing exposure adjustment in the imaging unit such that the exposure calculation value is substantially equal to the derived exposure target value;
Exposure adjustment method comprising The exposure adjustment method according to claim 4,
In the step (b), as the exposure target value according to the parameter, an average value of gradation values of a specific color portion in a photographed image photographed by the photographing unit is a desired floor regardless of a change in the zoom position. An exposure adjustment method characterized by deriving a value that is substantially equal to a tone value.

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