JP3852453B2 - 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 that captures an image of a projection target.

  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, an average value of gradation values of all pixels in the photographed 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 first projector of 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 zoom lens position detector for detecting a zoom position of the zoom lens;
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 acquires the zoom position detected by the zoom lens position detection unit, and changes the exposure target value to be set in the imaging control unit according to the acquired zoom position. To do.

  Thus, in the first projector, the exposure target value is changed according to the zoom position of the zoom lens. Therefore, for example, when the zoom position is set to the wide side and the area of the specific color portion represented by a specific color in the captured image becomes large, the exposure calculation value calculated from the captured image increases in the imaging control unit. However, for example, if the exposure target value is changed so as to increase as the zoom position becomes wide, exposure adjustment is performed so that the calculated exposure value becomes equal to the exposure target value as automatic exposure. However, since the average value of the gradation values of all the pixels in the photographed image does not decrease, the average value of the gradation values of the specific color portion can be substantially maintained at the desired gradation value. In addition, when the zoom position is set to the tele side and the area of the specific color portion in the captured image becomes narrow, the exposure calculation value calculated from the captured image is reduced in the imaging control unit. If the exposure target value is changed so as to decrease, the exposure level is adjusted so that the calculated exposure value is equal to the exposure target value as automatic exposure. Since the average value of the tone values does not increase, the average value of the tone values of the specific color portion can be substantially maintained at the desired tone value.

  In the first projector according to the aspect of the invention, the control unit may calculate an average gradation value of a specific color portion represented by a specific color in the captured image captured by the imaging unit based on the acquired zoom position. An exposure target value may be calculated such that the value is substantially equal to the desired gradation value regardless of the change in the zoom position, and the calculated exposure target value may be set in the imaging control unit.

Further, in the first projector of the present invention, an average of gradation values of a specific color portion represented by a specific color in a captured image photographed by the photographing unit corresponding to each zoom position of the zoom lens. An exposure target value table in which exposure target values are set in advance so that the value is substantially equal to the desired gradation value regardless of the change in the zoom position is prepared in advance.
The control unit refers to the exposure target value table based on the acquired zoom position, derives an exposure target value corresponding to the zoom position, and sets the derived exposure target value in the imaging control unit. It may be.

  Thus, based on the acquired zoom position, the exposure target value is calculated or derived from the exposure target value table, and the obtained exposure target value is set in the shooting control unit, so that the acquired zoom position is obtained. 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 second projector of 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 acquires a captured image captured by the capturing unit, and an average value of gradation values of a specific color portion represented by a specific color in the acquired captured image is substantially equal to a desired gradation value. Thus, the gist is to change the exposure target value to be set in the imaging control unit.

  As described above, in the second projector, the exposure target value is changed so that the average value of the gradation values of the specific color portion in the photographed image becomes substantially equal to the desired gradation value. Therefore, even if the zoom position of the zoom lens changes, the exposure target value changes so that the average value of the gradation values of the specific color portion is substantially equal to the desired gradation value. The average value of the gradation values 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:
5-5. Modification 5:

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 drive 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 position detection unit 122, a zoom lens drive unit 124, and a remote controller A control unit 126 and a remote control 128 are provided.

  In FIG. 1, the CPU 120 has an imaging control unit 105, a captured image memory 106, an image processing unit 108, a liquid crystal panel driving unit 110, a zoom lens position detection unit 122, a zoom lens driving unit 124, and remote control via a bus. Although it is depicted as being connected only to the portion 126, it is actually 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. The zoom lens position detection unit 122 can be configured by, for example, a zoom encoder. 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 zoom lens position detector 122 corresponds to the zoom lens position detector described in the claims, and the CPU 120 corresponds to the controller 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 control 128, the remote control 128 transmits the input instruction to the remote control 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, brightness, 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 in the 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 zoom position 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 the stop of the zoom position movement, 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. At this time, the zoom lens position detection unit 122 detects the zoom position of the zoom lens 116 and transmits the detection result to the CPU 120 as a zoom amount. In this embodiment, the zoom amount is “0” when the zoom position is at the extreme end on the tele side, and “255” when the zoom position is at the extreme end on the wide side.

  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 acquires the zoom amount transmitted from the zoom lens position detection unit 122 (step S102), and based on the acquired zoom amount, the exposure corresponding to the zoom amount is performed. A target value is calculated (step S104). Specifically, the exposure target value corresponding to the zoom amount is calculated by the following method. Here, the acquired zoom amount is Z, and the exposure target value to be calculated is R.

  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, in the captured image, the length of the horizontal side of the white portion (that is, the portion of the projection light range) is w, the length of the vertical side is h, and the area of the white portion is Sz. Regarding the relationship between the size of the projection light range and the zoom amount Z, it is generally known that the length of the horizontal side of the projection light range is proportional to the zoom amount Z. Accordingly, the length w of the horizontal side of the white portion is expressed by Expression (1).
w = k × Z + w0 (1)
However, k and w0 are constants, respectively.

Therefore, when the area Sz of the white portion is expressed by the zoom amount Z, the equation (1) is changed to the equation (2).
Sz = w × h
= K × w × w
= K × (k × Z + w0) ² (2)
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.

On the other hand, assuming that the average value of the gradation values of the white portion 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 given by equation (3). expressed.
Lccd = Sz × L / Sccd (3)
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.

By the way, in the automatic exposure, as described above, the average value Lccd of the gradation values of all 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. Therefore, by substituting R for Lccd in equation (3), the exposure target value R is expressed by equation (4).
R = Sz × L / Sccd (4)

Therefore, in order to maintain the average value L of the gradation value of the white portion in the photographed image substantially at the desired gradation value Lt regardless of the zoom position of the zoom lens 116, that is, the change in the zoom amount Z, the expression In (4), Lt is substituted for L and the value of equation (2) is substituted for Sz, and equation (5) is derived, and the calculated exposure value R is calculated according to equation (5) according to the zoom amount Z. That's fine.
R = K × (k × Z + w0) ² × Lt / Sccd (5)

  Next, the CPU 120 sets the exposure target value R calculated according to the zoom amount Z in the imaging control unit 105 (step S106), instructs the imaging control unit 105 to perform shooting (step S108), and FIG. The exposure target value setting process shown in FIG.

  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.

  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.

  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 expression (5) according to the zoom position of the zoom lens 116, that is, the zoom amount Z. Accordingly, when the zoom position is set to the wide side (that is, the zoom amount Z is increased) and the area of the white portion in the photographed image becomes wide, the average value Lccd of the gradation values of all the pixels is increased by the area. That is, the calculated exposure value increases, but the exposure target value R also increases by the amount of increase in the zoom amount Z according to the equation (5). 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, when the zoom position is set to the tele side (that is, the zoom amount Z is reduced) and the area of the white portion in the photographed image is reduced, similarly, the steps of all the pixels are reduced by the narrowed area. The average value Lccd of the tone values, that is, the calculated exposure value is lowered, but the exposure target value R is also lowered by the amount of the zoom amount Z according to the equation (5). 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 zoom amount Z has been calculated by the CPU 120 according to the equation (5), but the present invention is not limited to this. For example, for each zoom amount, an exposure target value R corresponding to the zoom amount Z is obtained in advance by calculation or measurement, and the result is used as an exposure target value table, and the exposure target value table storage unit 107 indicated by a dotted line in FIG. Store it in Then, the CPU 120 may read out and refer to the exposure target value table from the exposure target value table storage unit 107 and derive the exposure target value R corresponding to the zoom amount Z from the acquired zoom amount Z.

  FIG. 5 is an explanatory view showing an example of such an exposure target value table. 5A shows the contents of the exposure target value table, and FIG. 5B is a graph showing the relationship between the zoom amount Z and the exposure target value R obtained from the exposure target value table. The magnitude of the zoom amount Z may be opposite depending on how the encoder value is taken.

  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. 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 as the zoom amount Z increases. That is, the exposure target value R is smaller as the zoom position of the zoom lens 116 is at the telephoto side, and is larger as it is at the wide side.

  In the exposure target value table shown in FIG. 5A, the zoom amount Z is described as a value in increments of “5”, but actually, when the described value is a, for example, a For the zoom amount Z in the range of −2.5 <Z ≦ a + 2.5, the exposure target value R corresponding to the value a is used.

5-2. Modification 2:
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 apparent from the above-described equation (4), 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, if the area of the white portion is the same, the exposure target value R calculated according to the zoom amount Z does not change regardless of the shape of the white portion.

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 /. When a horizontally long image of 3 is used, the area Sz of the white portion in the captured image is as shown in Expression (2) ′.
Sz = (1/3) × K × (k × Z + w0) ² (2) ′

Therefore, the exposure target value R is also expressed as in Expression (5) ′.
R = (1/3) × K × (k × Z + w0) ² × Lt / Sccd (5) ′

  Therefore, as the area Sz of the white portion in the photographed image becomes smaller, the curve representing the relationship between the zoom amount Z and the exposure target value R shown in FIG.

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

5-3. Modification 3:
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.

5-4. Modification 4:
In the above-described embodiment, the zoom amount is “0” when the zoom position is at the extreme end on the tele side, and the zoom amount is “255” when the zoom position is at the extreme end on the wide side. The zoom amount is not limited to these values, and the zoom amount may be a value other than “255” when the zoom lens is at the extreme end on the wide side. Also, the zoom amount “0” may be set when the zoom position is at the widest end. Also, the zoom amount may have an offset value. Further, a value other than the zoom amount may be used as long as the value corresponds to the zoom position of the zoom lens 116.

  In the case of this modification, the above-described formulas (1) to (5) themselves need to be corrected according to the modification.

5-5. Modification 5:
In the above-described embodiment, even if the zoom position of the zoom lens 116 is changed, the exposure is performed according to the zoom position so that the average value of the gradation value of the white portion in the captured image is substantially maintained at the desired gradation value. Although the target value is changed, the present invention is not limited to this, and the exposure target value is changed so that the average value of the gradation values in the white portion is substantially equal to the desired gradation value. You may do it.

  The configuration of the projector in this modification is almost the same as the configuration of the projector 100 shown in FIG. However, in this modification, it is not necessary to know the zoom position of the zoom lens 116, that is, the zoom amount, and therefore the zoom lens position detection unit 122 is unnecessary.

  FIG. 6 is a flowchart showing a processing procedure of exposure target value setting processing in the modification.

  When the user operates the zoom button of the remote control 128 to move the zoom position of the zoom lens 116 to a desired position, when the processing shown in FIG. 6 is started, the CPU 120 starts from an unillustrated memory. The value is read, and the initial value is set as the exposure target value R in the imaging control unit 105 (step S202), and then imaging is instructed to the imaging control unit 105 (step S204). Thereby, the imaging control unit 105 controls the imaging unit 104 to start imaging, and the imaging unit 104 images the screen on which the pattern image is displayed. At this time, the imaging control unit 105 calculates an exposure calculation value from the image captured by the imaging unit 104, and the imaging unit 104 so that the exposure calculation value becomes equal to the set exposure target value R, that is, the initial value. The automatic exposure is performed by controlling the shutter speed at. 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, and the content is updated.

  Next, the CPU 120 reads a digital image signal from the captured image memory 106, acquires the captured image, analyzes the captured image, and derives an average value of the gradation values of the white portion in the captured image (step S206). . Then, the CPU 120 reads the desired gradation value Lt from a memory (not shown), and compares the average value of the gradation values in the white portion with the desired gradation value Lt (step S208). As a result, when the average value of the gradation values of the white portion is lower than the desired gradation value Lt, a value higher than the exposure target value set in the imaging control unit 105 previously is set as a new exposure target value R. On the contrary, when the value is set to the imaging control unit 105 (step S210) and is higher than the desired gradation value Lt, a value lower than the exposure target value previously set to the imaging control unit 105 is set as a new exposure target value. R is set in the imaging control unit 105 (step S212). Then, the CPU 120 obtains a captured image from the captured image memory 106 again, derives an average value of the gradation value of the white portion in the captured image, and thereafter performs the same processing as the average of the gradation value of the white portion. Repeat until the value is equal to the desired gradation value Lt. As a result of the comparison, finally, when the average value of the gradation values of the white portion becomes equal to the desired gradation value Lt, the CPU 120 instructs the imaging control unit 105 to perform imaging (step S214). Since the imaging unit 104 is already shooting, the imaging control unit 105 causes the imaging unit 104 to continue shooting.

  By operating as described above, even in this modified example, the average value of the gradation value of the white portion in the photographed image can be substantially maintained at the desired gradation value with respect to the change in the zoom position of the zoom lens 116. it can.

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 an exposure target value table. It is a flowchart which shows the process sequence of the exposure target value setting process in a 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
122 ... Zoom lens position detection unit 124 ... Zoom lens driving unit 126 ... Remote control unit 128 ... Remote control 130 ... CCD module

Claims (7)

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 zoom lens position detector for detecting a zoom position of the zoom lens;
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 acquires the zoom position detected by the zoom lens position detection unit, and changes the exposure target value to be set in the imaging control unit according to the acquired zoom position. Projector. The projector according to claim 1, wherein
The control unit, based on the acquired zoom position, an average value of gradation values of a specific color portion represented by a specific color in a captured image captured by the imaging unit corresponds to a change in the zoom position. Regardless of the case, the projector calculates an exposure target value that is substantially equal to the desired gradation value, and sets the calculated exposure target value in the imaging control unit. The projector according to claim 1, wherein
Corresponding to each zoom position of the zoom lens, the average value of the gradation values of the specific color portion represented by the specific color in the captured image captured by the imaging unit is independent of the change in the zoom position. Prepare in advance an exposure target value table in which exposure target values are set so as to be approximately equal to the desired gradation value,
The controller refers to the exposure target value table based on the acquired zoom position, derives an exposure target value corresponding to the zoom position, and sets the derived exposure target value in the imaging control unit. Projector. 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 acquires a captured image captured by the capturing unit, and an average value of gradation values of a specific color portion represented by a specific color in the acquired captured image is substantially equal to a desired gradation value. The projector is characterized in that the exposure target value to be set in the imaging control unit is changed. 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) detecting a zoom position of the zoom lens;
(B) deriving an exposure target value according to the zoom position based on the detected zoom position;
(C) calculating an exposure calculation value from a captured image captured by the imaging unit, and performing exposure adjustment in the imaging unit so 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 5,
In the step (b), as the exposure target value according to the zoom position, an average value of gradation values of a specific color portion represented by a specific color in the captured image captured by the imaging unit is An exposure adjustment method characterized by deriving a value that is substantially equal to a desired gradation value regardless of a change in zoom position. 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) calculating an exposure calculation value from a captured image captured by the imaging unit, and performing exposure adjustment in the imaging unit so that the exposure calculation value is substantially equal to an exposure target value;
(B) obtaining a photographed image photographed by the photographing unit;
(C) changing the exposure target value so that an average value of gradation values of a specific color portion represented by a specific color in the acquired photographed image is substantially equal to a desired gradation value;
Exposure adjustment method comprising

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