JP2012155049A - Projector and light source control method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately adjust luminance of a video image to be projected even when the video image is being projected.SOLUTION: A projector comprises: liquid crystal light valves 100R, 100G and 100B for modulating light emitted from LEDs 10R, 10G and 10B that configure a light source section according to a video signal Vid; a projection lens 16 for projecting a synthesized image with modulated images; an LUT 36a for storing a relation between luminance of a non-projection area and projection luminance; an image analyzing section 30 for analyzing an imaged image by an imaging device 18 so as to output luminance of a projection area and the luminance of the non-projection area in a projection plane; a luminance determining section 34 for reading out the projection luminance corresponding to the luminance of the non-projection area from the LUT 36a; and a light source controller 38 for controlling the light source section such that the luminance of the projection area becomes the projection luminance.

Description

The present invention relates to a technique for appropriately adjusting the luminance of a projected image according to the brightness around a projection surface.

2. Description of the Related Art In recent years, there has been known an image display device that improves the visibility of an image or saves energy in accordance with brightness such as illuminance and luminance in an installation place such as a room. In such a video display device, when the room is bright, the visibility of the video can be improved by increasing the brightness of the video to be displayed. On the contrary, when the room is dark, energy saving is achieved by reducing the brightness of the display video. Can be achieved.
Therefore, a technique has been proposed in which a sensor is provided on the front surface of the projector housing to acquire the brightness of the projected image, and the brightness of the projected image is corrected based on the viewing environment acquired by the sensor ( For example, see Patent Document 1).

JP 2003-280629 A (see FIGS. 1 and 3)

By the way, when correcting the luminance of an image by the above technique, since a predetermined calibration image is projected, it is necessary to temporarily interrupt the projection of the image based on the image signal.
The present invention has been made in view of the above-described circumstances, and one of its purposes is to provide a technique for appropriately adjusting the brightness of a projected image even while the image based on the image signal is being projected. It is in.

In order to achieve the above object, in the projector according to the present invention, a light source unit that supplies light, and the light from the light source unit is modulated according to a video signal that defines an image to be projected,
A light modulator that generates a modulated image; a light projection unit that projects the modulated image by the light modulator onto a projection area of the projection surface; and a luminance of a non-projection area of the projection surface on which the modulation image is not projected. A storage unit that stores a relationship with a projection luminance when projecting an image on the projection area, a luminance acquisition unit that acquires a luminance of the projection area and a luminance of the non-projection area on the projection surface,
A luminance determination unit that reads out the projection luminance corresponding to the acquired luminance of the non-projection area from the storage unit, and a light source control unit that controls the light source unit so that the acquired luminance of the projection area becomes the projection luminance It is characterized by comprising.
According to this configuration, the light source unit is controlled according to the luminance of the non-projection area that is not easily affected by the projected image on the projection surface. For this reason, it is possible to appropriately adjust the brightness of the projected image even while the image is being projected.

In the present invention, the storage unit stores a ratio between the luminance of the non-projection area and the luminance of the projection area when the light source unit is off or when a black image is projected onto the projection area. The luminance determination unit may be configured to correct the acquired luminance of the non-projection area to a value obtained by multiplying the luminance of the non-projection area by the ratio and read out the target luminance corresponding to the value.
According to this configuration, even when, for example, a screen having a frame is used as the projection surface, it is possible to appropriately adjust the luminance of the projected image.

In this configuration, it is preferable that the luminance determining unit corrects the target luminance in accordance with an average luminance value in a portion corresponding to the projection area in an image defined by the video signal.
In this way, the brightness of the image can be adjusted without changing the image projected on the projection area.

As a configuration further comprising a reset determining unit that causes the luminance determining unit to correct the target luminance again when the acquired luminance of the non-projection area changes beyond a threshold value within a predetermined time. Also good.
According to this configuration, even when the environmental brightness of the projection surface changes for some reason, it is possible to appropriately adjust the brightness of the projected image in accordance with the changed environmental brightness.

The light source control unit may be configured to gradually increase the amount of light supplied from the light source unit so that the luminance of the acquired projection area becomes the target luminance when the light source unit is turned on.
According to this configuration, compared with a configuration in which the light amount of the light source unit reaches the target luminance by repeating bright and dark, it is not necessary to give an unpleasant feeling to the viewer.

Moreover, it is good also as a structure which further has a sensor which each detects the brightness | luminance of the said projection area and the brightness | luminance of the said non-projection area among the said projection surfaces, and supplies it to the said brightness | luminance acquisition part.
According to this configuration, the brightness of the projected image can be appropriately adjusted with the projector alone.

The present invention can be conceptualized not only as a projector but also as a light source control method for the projector.

1 is a perspective view showing an external configuration of a projector according to an embodiment of the invention. It is a top view which shows the optical structure of a projector. It is a block diagram which shows the electrical structure of a projector. It is a top view which shows a projection area and a non-projection area. It is a flowchart which shows operation | movement of a projector. It is a figure which shows the relationship between a screen and a photometry area. It is a flowchart which shows operation | movement of a projector. It is a figure which shows the (gamma) characteristic which is the relationship between a gradation level and relative luminance. It is a figure which shows the other example of arrangement | positioning of a photometry area.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram illustrating an external configuration of a projector 1 according to the present embodiment.
As shown in this figure, the projector 1 is a front projection type that projects an image from a projection lens 16. The projection lens 16 has a zoom mechanism. For this reason, the projector 1
In this case, the size of the projected image can be adjusted by rotating the zoom ring 17.
Further, the projector 1 is provided with a digital image pickup device (camera) 18 in the vicinity of the projection lens 16 for picking up a still image in a wider range than the projected image.

FIG. 2 is a plan view showing an optical configuration of the projector 1.
The LED 10R for red light is a light source unit that supplies R light. The R light from the LED 10R is collimated by the collimator lens 12, and then the liquid crystal light valve 100R for R light.
Is incident on. The liquid crystal light valve 100R is an aspect of an optical modulator, and is a transmissive liquid crystal panel having a plurality of pixels arranged in a matrix, and modulates R light for each pixel in accordance with a video signal. For this reason, the light emitted from the liquid crystal light valve 100R becomes a modulated image of R light with the transmittance modulated for each pixel. The modulated image of the R light modulated by the liquid crystal light valve 100R enters the dichroic prism 14 from the 12 o'clock direction in the figure.
Similarly, the green LED 10G is a light source unit that supplies G light. LED10
The G light from G is collimated by the collimator lens 12 and then enters the liquid crystal light valve 100G for G light. The G light modulated by the liquid crystal light valve 100G enters the dichroic prism 14 from the 9 o'clock direction in the figure.
Similarly, the blue LED 10B is a light source unit that supplies B light. LED10
The B light from B is collimated by the collimator lens 12 and then enters the liquid crystal light valve 100B for B light. The B light modulated by the liquid crystal light valve 100B enters the dichroic prism 14 from the 6 o'clock direction in the figure.
Note that other individual light sources such as semiconductor lasers may be used instead of the LEDs 10R, 10G, and 10B. Further, the projector 1 may be provided with a homogenizing optical system that makes the intensity distribution of the light beam uniform, for example, a rod integrator or a fly-eye lens.

The dichroic prism 14 has two dichroic films 14R and 14B arranged so as to be orthogonal to each other. The dichroic film 14R reflects R light, but transmits G light and B light other than R light. On the other hand, the dichroic film 14B reflects B light,
Transmits R light and G light other than B light.
Therefore, the dichroic prism 14 combines the R light incident from the 12 o'clock direction, the G light incident from the 9 o'clock direction, and the B light incident from the 6 o'clock direction, respectively, in the 3 o'clock direction. Exit. The projection lens 16 projects the light combined by the dichroic prism 14 onto the screen 200.
In this description, the screen 200 is used to mean a surface including an area on which an image is projected. Therefore, the screen 200 is a concept including not only an area where an image is projected but also an area around the area where an image is projected and an area where the image is not projected. Further, the screen 200 may refer not only to a cloth-like white curtain (so-called silver screen) used exclusively for image projection, but also to a screen, a ceiling, a partition, a wall surface and the like including an area where an image is projected.

Here, various areas in the screen 200 will be described with reference to FIG.
In the figure, the projection area 60a refers to an area where an image is actually projected on the screen 200 or an area where an image is scheduled to be projected. On the other hand, the non-projection area 60b refers to an area of the screen 200 excluding the projection area 60a.
The imaging area 70 in the imaging device 18 includes a projection area 60a and a non-projection area 60b.
It is set to be a range that includes a part of.
The photometry area 18a in the projection area 60a and the photometry area 18b in the non-projection area 60b will be described later.

Next, the electrical configuration of the projector 1 will be described with reference to FIG.
As shown in the figure, the video signal Vid is supplied to the projector 1 in synchronization with the synchronization signal Sync. The video signal Vid indicates the brightness (luminance) of the RGB component of the video to be displayed.
For example, it is digital data that is specified for each pixel with gradation levels from “0” to “255”, each of which is 8 bits.
When the video signal Vid is supplied as an analog signal, it may be converted into digital data by an A / D conversion circuit (not shown).
The liquid crystal control unit 20 controls each part of the video processing unit 22, the D / A conversion circuits 24R, 24G, and 24B, and the liquid crystal driving units 26R, 26G, and 26B in accordance with the synchronization signal Sync.
The video processing unit 22 executes gamma processing for adjusting the brightness of RGB components specified by the video signal Vid to the display characteristics of the liquid crystal light valves 100R, 100G, and 100B, for example. The gamma (γ) coefficient which is a parameter of this gamma processing is, for example, the liquid crystal control unit 2.
Supplied from zero.

The D / A conversion circuit 24R converts the R component video signal that has been subjected to gamma processing into the liquid crystal control unit 20.
Convert to analog signal with polarity specified by. Similarly, the D / A conversion circuit 24G is a G component video signal that has been subjected to gamma processing, and the D / A conversion circuit 24B is a B signal that has been subjected to gamma processing.
The component video signals are converted into analog signals having polarities designated by the liquid crystal control unit 20, respectively.
Here, the polarity is either positive polarity or negative polarity, and the liquid crystal control unit 20 sets the polarity to each pixel of the liquid crystal light valves 100R, 100G, and 100B so that no DC component is applied. Alternately switched between negative polarity and negative polarity.

The liquid crystal driving unit 26R performs vertical scanning and horizontal scanning of the liquid crystal light valve 100R according to instructions to the liquid crystal control unit 20, and drives the scanned pixels with an R component video signal converted into analog. With this driving, in the liquid crystal light valve 100R, each pixel has the transmittance defined in the video signal, so that the emitted light when the R light is incident becomes a modulated image of the R light.
Similarly, the liquid crystal driving unit 26G drives the liquid crystal light valve 100G with a G component video signal, and the liquid crystal driving unit 26B drives the liquid crystal light valve 100B with a B component video signal. Thus, in the liquid crystal light valve 100G, the emitted light when the G light is incident becomes a modulated image of the G light, and in the liquid crystal light valve 100B, the emitted light when the B light is incident becomes the modulated image of the B light.

The imager 18 outputs information on the captured image. On the other hand, the encoder 19 detects the rotation angle of the zoom ring 17 in the projection lens 16 and outputs the angle information. The angle information indicates the focal length of the projection lens 16 that is a zoom lens, that is, the enlargement ratio.
The image analysis unit 30 analyzes the image information obtained by the image pickup device 18, calculates the luminance of the projection area 60a and the luminance of the non-projection area 60b, and outputs information on each luminance. In other words, since the image analysis unit 30 acquires information indicating the luminance of the projection area 60a and information indicating the luminance of the non-projection area 60b, the image analysis unit 30 functions as a luminance acquisition unit.

Here, as shown in FIG. 4, the photometric area 18a is located substantially at the center of the projection area 60a. The photometry area 18b is located to the right of the projection area 60a in the non-projection area 60b. The horizontal position of the photometric area 18b is the same as the horizontal position of the photometric area 18a.
The image analysis unit 30 calculates the luminance in the photometry area 18a, represents the luminance and outputs it as the luminance of the projection area 60a. Similarly, the image analysis unit 30 calculates the luminance in the photometry area 18b, The luminance is represented as the luminance of the non-projection area 60b.
The following is the same as the horizontal position of the photometric areas 18a and 18b.
That is, since the indoor lighting is usually provided on the ceiling, if the photometric area 18b is arranged in the vertical direction (up or down) of the photometric area 18a, it is affected by the difference in brightness due to the indoor lighting. is there. For this reason, in the present embodiment, the photometry areas 18a and 18b are aligned in the horizontal position so as not to be easily affected by the difference in brightness due to room lighting.
In addition, since the projection lens 16 has a zoom mechanism, the size of the projected image is also changed by the rotation of the zoom ring 17. For this reason, the image analysis unit 30 includes the encoder 19.
From the angle information obtained by the above, the size of the projection area 60a is grasped, and the projection area 60a (photometry area 18a) and the non-projection area 60b (photometry area 18b) are defined.

Returning the description to FIG. 3 again, the reset determination unit 32 includes the LEDs 10R, 10G, which are light source units,
When the image is projected with 10B lit, the brightness of the non-projection area 60b is fixed for a certain period of time,
For example, when the threshold value is changed over one second, the brightness determination unit 34 is notified of this.
On the other hand, the storage unit 36 stores in advance, as an LUT (lookup table) 36a, a relationship between the environmental luminance of the projection surface and the projection luminance that is a target value when a white image is projected onto the projection area 60a.
The environmental brightness of the projection surface here refers to the light source unit 1 among the brightness of the area where the image is projected.
Excluding the influence of 0, it means the brightness defined only by the surrounding environment such as the light blocking state of the room lamp and curtain. In other words, the environmental brightness of the projection plane determines the black brightness when the image is projected with the light source unit 10 turned on. Regarding the relationship between the environmental brightness of the projection plane and the projection brightness, the projection brightness is set so that the brightness is not dazzled and sufficient brightness is ensured with respect to the environmental brightness of the projection plane. Therefore, for the LUT 36a, for example, if the environmental brightness of the projection plane is “0.5 cd / m ² ”, the projection brightness is “50 cd / m ² ”, and for example, the environmental brightness of the projection plane is “0.6 cd”. if / ^{m 2} "a, projection brightness relationship such as" 75 cd / ^{m 2} "is stored.
Further, the storage unit 36 stores the brightness of the projection area 60a and the non-projection area 60 immediately after startup.
The ratio of b to the luminance is stored.

Immediately after the projector 1 is started up, the luminance determination unit 34 stores the luminance of the projection area 60a and the luminance and ratio of the non-projection area 60b in the storage unit 36, or the LUT 36 described above.
The projection brightness with respect to the brightness of the non-projection area 60b is read with reference to a, and is output as the target brightness of the light source. In addition, the luminance determination unit 34 is configured to reset the determination unit 3 during image projection.
2 receives a notification that the luminance of the non-projection area 60b has changed beyond the threshold value,
The target luminance of the light source is output again.
The light source control unit 38 generates a drive signal for each of the LEDs 10R, 10G, and 10B so that the luminance of the projection area 60a becomes the target luminance output by the luminance determination unit 34. The light source driving unit 40R drives the LED 10R according to the R driving signal. Similarly, the light source driver 40G drives the LED 10G according to the G drive signal, and the light source driver 40
B drives the LED 10B according to the drive signal for B.

Next, the light source control operation of the projector 1 according to the embodiment will be described. In the present embodiment, the light source control operation is performed immediately after the projector 1 is turned on, that is, immediately after startup, in the operation of adjusting the light amounts of the LEDs 10R, 10G, and 10B that are the light source units according to the detected luminance, When the environmental brightness of the projection surface changes for some reason, there are two types of operations: readjustment of the light amounts of the LEDs 10R, 10G, and 10B in accordance with the changed environmental brightness.

Therefore, first, the light amount control operation executed immediately after startup will be described with reference to FIGS. FIG. 5 is a flowchart showing a light source control operation executed immediately after startup, and FIG. 6 is a plan view for explaining the state of the screen 200 and the like in the light amount control operation.
First, immediately after the projector 1 is turned on, the light source driving units 40R and 40G are used.
, 40B do not immediately turn on the LEDs 10R, 10G, 10B, but maintain the non-lighted state. On the other hand, the imager 18 captures the screen 200 and supplies the captured image to the image analysis unit 30.
In step Sa1, the image analysis unit 30 analyzes the captured image to measure the photometry area 18.
The luminances a and 18b are obtained respectively. Then, the image analysis unit 30 calculates the obtained photometric area 18.
The luminance information of a (projection area 60a) and the luminance information of photometry area 18b (non-projection area 60b) are supplied to the luminance determination unit 34, respectively.

The luminance determination unit 34 that has received the luminance information of the projection area 60a and the luminance information of the non-projection area 60b causes the storage unit 36 to store the ratio of both luminances (luminance ratio) in step Sa2. Thus, for example, if the luminance of the projection area 60a and the luminance of the non-projection area 60b are the same, “1.0” is stored as the luminance ratio, and the luminance of the non-projection area 60b is relative to the luminance of the projection area 60a. If it is “20%”, “0.2” is stored as the luminance ratio.

Here, the case where the luminance ratio is not “1.0” even though the LEDs 10R, 10G, and 10B are in the non-lighting state is, for example, a non-projection area on the screen 200 as shown in FIG. When 60b is darker than the projection area 60a, that is, the screen 20
This is a case where a frame is formed at zero.
On the other hand, the case where the luminance ratio is “1.0” is a case where the projection area 60a and the non-projection area 60b cannot be distinguished on the screen 200 as shown in FIG. 6A, for example.
Since the projector 1 is used in a relatively dark environment, the screen 2 in FIG.
In 00, the darkness is expressed by the density of oblique lines applied to the area of each part.

In any case, since the LEDs 10R, 10G, and 10B that are the light source units are not lit, the luminance of the projection area 60a indicates the environmental luminance of the projection surface. Therefore, in step Sa3, the luminance determining unit 34 refers to the LUT 36a, reads the projection luminance corresponding to the luminance of the projection area 60a when the light source unit is in the non-lighted state, and uses the target luminance as an initial value as the light source. It supplies to the control part 38.
When the luminance of the projection area 60a and the luminance of the non-projection area 60b are the same, that is, when the luminance ratio is “1.0”, the luminance of the non-projection area 60b also indicates the projection luminance. Even when the luminance ratio is not “1.0”, the projection luminance can be estimated from the luminance of the non-projection area 60b. For example, when the luminance ratio is “0.2”, when the luminance of the non-projection area 60 b is multiplied by the reciprocal of the luminance ratio, the multiplication result is the projection area 6.
Since the luminance is 0a, the environmental luminance of the projection surface is indicated. Therefore, in any case, when the luminance of the non-projection area 60b is multiplied by the reciprocal of the luminance ratio, the environmental luminance of the projection surface is obtained from the multiplication result, and the projection luminance as the initial value of the target luminance is read from the LUT 36a. Can do.

Now, the light source control unit 38 that has received the supply of the target luminance notifies the video processing unit 22 to that effect. Regardless of the video signal Vid, the video processing unit 22 outputs RGB components for all the pixels, for example, at “255” where the maximum gradation level is the maximum value. As a result, the composite image by the liquid crystal light valves 100R, 100G, and 100B becomes a white image with the maximum luminance.

Next, in step Sa4, the light source control unit 38 determines that the current LED 10R, 1
The light source driving units 40R, 40G, and 40B are instructed so that 0G and 10B become brighter by one level, for example, by about 2% of the supplied target luminance. As a result of driving the light source driving units 40R, 40G, and 40B according to this instruction, the LEDs 10R, 10G,
Each of 10B is actually controlled to be brighter by one level.
In addition, when step Sa4 is performed for the first time, the state immediately before LED10R, 10G, 10B is a non-lighting state. For this reason, when step Sa5 is executed for the first time, the light source control unit 38 starts lighting by setting the brightness of the LEDs 10R, 10G, and 10B to approximately 2% of the target luminance. Thereafter, each time Step Sa4 is repeated, the light source control unit 38 increases the target luminance by 4%, 6%, 8%,.
FIG. 6B shows a state where the LEDs 10R, 10G, and 10B are turned on and only the projection area 60a is brightened.

When the brightness of the LEDs 10R, 10G, and 10B is changed, in step Sa5, the image analysis unit 30 analyzes the image captured by the image sensor 18, obtains the luminance of the projection area 60a, and supplies the luminance to the light source control unit 38. To do.
In step Sa6, the light source control unit 38 determines whether or not the difference between the target luminance supplied from the luminance determination unit 34 and the luminance of the actual projection area 60a obtained by the image analysis unit 30 is within the threshold value Th1. Is determined. As a result of the determination, if the difference exceeds the threshold value Th1,
It is considered that the luminance of the actual projection area 60a has not yet reached the target luminance after the power is turned on. For this reason, the process of step Sa4 is executed again in the light source control unit 38 in order to further brighten the light source by one level. That is, steps Sa4, Sa5, Sa
6 is repeatedly executed until the difference between the target brightness and the actual brightness of the projection area 60a falls within the threshold value Th1.
When the processing of steps Sa4, Sa5, and Sa6 is repeated in this manner, the difference between the target luminance and the luminance of the projection area 60a will eventually be within the threshold value Th1. When the value is within the threshold value Th1, the actual brightness of the projection area 60a has reached the target brightness after the power is turned on, or
Since the brightness difference is considered to be negligible, the determination result in step Sa6 is “
“Yes”, and the light source control operation ends.

Here, when the loop process of steps Sa4, Sa5, and Sa6 is executed at a rate of 50 times per second, for example, the LEDs 10R, 10G, and 10B are 2% of the target brightness, 4% from the start of lighting.
%, 6%,... Gradually increase in brightness, and eventually reach the target brightness in about 1 second.
In feedback control in which the brightness of the projection area 60a simply matches the target brightness,
Since the LEDs 10R, 10G, and 10B converge to the target luminance while repeating light and dark, the light and dark at that time are given to the viewer as discomfort. On the other hand, in this light quantity control operation, since the brightness is controlled only in the increasing direction, such discomfort is not given to the viewer.

In this way, when the amount of light is controlled so that the target luminance is adjusted to the luminance of the non-projection area 60b immediately after activation, projection of an image according to the input video signal Vid is started.
Here, during projection of an image, when the environmental luminance of the projection surface changes due to, for example, lighting of a room lamp for some reason, it is necessary to control the light amount of the light source according to the changed luminance. However, since an image has already been projected in the projection area 60a, in the configuration in which the luminance of the projection area 60a is detected, whether the change in luminance is due to the projected image or the environmental luminance of the projection surface. Is difficult to distinguish.
In the present embodiment, the projection area 60a and the non-projection area 60b before the light source is turned on.
Is stored in the storage unit 36. As described above, the environmental brightness of the projection plane can be estimated by multiplying the brightness of the non-projection area 60b by the reciprocal of the brightness ratio.
Therefore, in the present embodiment, when an image is projected on the projection area 60a, the environmental brightness of the projection surface is estimated from the brightness of the non-projection area 60b instead of the projection area 60a, and the light amount is controlled. It was to be.

FIG. 7 is a flowchart showing a light source control operation executed during image projection.
First, in step Sb1, the imaging device 18 captures the screen 200 and supplies the image information to the image analysis unit 30, and the image analysis unit 30 analyzes the image information to analyze the photometric area 18b, that is, non-projection. The brightness of the area 60b is obtained. In step Sb2, the reset determination unit 32 compares the luminance information of the current non-projection area 60b with the luminance information of the previous non-projection area 60b read from the storage unit 36, and the luminance difference is a threshold value Th2. It is determined whether or not the number is exceeded. The reset determining unit 32 stores the luminance information of the current non-projection area 60b in the storage unit 36 for use as the luminance information of the previous non-projection area 60b when the next step Sb2 is executed.
If the brightness difference exceeds the threshold value Th2, it is considered that the environmental brightness of the projection surface has changed to a degree that cannot be ignored. Therefore, the reset determining unit 32 notifies the brightness determining unit 34 to that effect.
On the other hand, if the difference is within the threshold value Th2, it is considered that the environmental brightness of the projection surface has not changed, or the change can be ignored, and the processing procedure returns to step Sb1.
Here, when the loop processing of steps Sb1 and Sb2 is executed at a rate of once per second, for example, the environmental luminance on the projection plane is detected at intervals of 1 second.

In step Sb3, the luminance determining unit 34 re-determines the target luminance as follows based on the supplied video data Vid. Specifically, the luminance determination unit 34 first reads the luminance ratio from the storage unit 36, and secondly obtains a product obtained by multiplying the luminance of the non-projection area 60b after the change by the reciprocal of the luminance ratio, 3, the projection luminance corresponding to the product is read with reference to the LUT 36 a.
Further, the light source control unit 38 corrects the read projection brightness based on the video data Vid,
This is supplied to the light source controller 38. Specifically, the luminance determination unit 34 first calculates an average value of gradation levels of a plurality of pixels included in a region corresponding to the photometric area 18a in the video defined by the video data Vid, In addition, the projection luminance read from the LUT 36a is corrected according to the average value. Here, the reason for correcting the target luminance read from the LUT 36a with the average value is as follows. In other words, the LUT 36a stores the projection brightness, that is, the target value when a white image is projected, but at the present time the projection area 60a (the photometry area 18).
The projection on a) is not a white image but an image based on the image data Vid.
As for the correction example, when the read projection brightness is “50 cd / m ² ” and the average value of the gradation level is “128” and the gamma coefficient is “2.6”, photometry is performed. Area 1
As shown in FIG. 8, the luminance of 8a is 16.7% as relative luminance. For this reason, the projection luminance is “8.35 cd / m ² ” which is 16.7% of “50 cd / m ² ”.
To be corrected. The relative luminance here is normalized when the luminance corresponding to “0” having the darkest gradation level is set to 0% and the luminance corresponding to “255” having the brightest gradation level is set to 100%. The brightness is shown.
As described above, when the luminance determination unit 34 corrects the projection luminance, the corrected projection luminance is reset as the target luminance in the light source control unit 38.

In step Sb4, the light source control unit 38 resets the target luminance and the image analysis unit 30.
Is compared with the brightness of the projection area 60a, and the current drive state is instructed to the light source drive units 40R, 40G, and 40B in a direction to eliminate the brightness difference. As a result of actually driving the corresponding LEDs 10R, 10G, 10B by the light source driving units 40R, 40G, 40B according to this instruction, the luminance of the photometry area 18a in the image projected on the screen 200 is
The light source unit is controlled so as to approach the reset target luminance.

When the brightness of the LEDs 10R, 10G, and 10B is changed, in step Sb5, the image analysis unit 30 analyzes the image information obtained by the imager 18, obtains luminance information of the photometry area 18a, and sends it to the light source control unit 38. Supply.
In step Sb6, the light source control unit 38 determines whether or not the difference between the target luminance reset by the luminance determination unit 34 and the luminance of the actual projection area 60a obtained by the image analysis unit 30 is within the threshold value Th1. Determine whether or not. As a result of the determination, if the difference exceeds the threshold value Th1, the control result in step Sb4 is insufficient. Therefore, the processing procedure returns to step Sb4, and the brightness in the photometric area 18a is reset. Control close to the luminance is performed again on the light source unit. As described above, when the processes of steps Sb4, Sb5, and Sb6 are repeated,
Eventually, the difference between the luminance of the photometry area 18a and the reset target luminance falls within the threshold value Th1. When the value is within the threshold value Th1, the determination result in step Sb6 is “Yes”, and the light source control operation ends.

As described above, according to this embodiment, when an image is projected on the projection area 60a, the brightness of the light source unit is determined by estimating the environmental brightness on the projection surface from the brightness of the non-projection area 60b. Since the control is performed, it is possible to appropriately adjust the luminance of the image projected on the screen 200.

The present invention is not limited to the above-described embodiments, and various applications and modifications are possible.
For example, the liquid crystal light valves 100R, 100G, and 100B are not limited to the transmissive type but may be a reflective type. As the light modulator, liquid crystal light valves 100R, 100R
Not limited to G and 100B, an EL element, a mirror element, and more specifically, a mirror that takes a position corresponding to on / off of the mirror and reflects incident light in a predetermined direction only when it is on or off. It can also be applied to elements.

Further, for example, as shown in FIG. 9, the photometry area 18b of the non-projection area 60b may be arranged at a total of two locations, one on the left and the right around the photometry area 18a. Alternatively, a larger number of photometric areas may be arranged. When a plurality of photometric areas 18b are arranged in this way, it is possible to more accurately estimate the environmental brightness on the projection plane if the average value of the brightness obtained in each area is obtained as the brightness of the non-projection area 60b. it can.

In the light amount control immediately after startup, when the luminance ratio between the projection area 60a and the non-projection area 60b is obtained, the light source unit is set to the non-lighted state, but the light source unit is turned on and the black image is projected. good. For this purpose, the video processing unit 22 uses the video signal V.
Regardless of id, if the gradation levels of RGB for all the pixels are set to the lowest value “0”, the composite image by the liquid crystal light valves 100R, 100G, and 100B becomes a black image.
Further, after storing the luminance ratio, a white image is projected and the light source unit is controlled so that the luminance of the projection area 60a reaches the target luminance. However, for example, a gray image other than white may be projected. When a gray image is projected, the target luminance may be corrected according to the gray.

Further, since it is sufficient that the luminance of the photometric areas 18a and 18b on the screen 200 can be obtained, the image pickup device 18 may be externally installed instead of being provided in the housing of the projector 1. If the imaging device 18 is a separate configuration, the projector 1
For example, the luminance information of the photometric areas 18a and 18b may be input via an interface. The imager 18 is not a camera but a photometric area 18a, 18b.
Any sensor can be used as long as it requires the brightness of the sensor.

The projection area 60a and the non-projection area 60b can be defined by the following method if a large number of photometric areas 18b are arranged without using the rotation angle of the zoom ring 17. That is, immediately after the projector 1 is activated, the light source unit is turned off, and the ambient brightness on the projection plane is acquired by the photometric area 18a of the projection area 60a, and the brightness of the other photometric areas 18b is also acquired. Thereafter, the light source unit is turned on, and it is determined that the light measurement area 18b having no change in brightness or the least is present in the non-projection area 60b, and is used for the photometry in the non-projection area 60b. Use it.
Of course, the projection lens 16 may be of a fixed focus type without a zoom mechanism.

During the projection of an image, the luminance of the non-projection area 60 b may be affected by the light leaking from the projection lens 16. For this reason, not only the luminance ratio in the non-lighting state of the light source unit immediately after startup, but also the luminance ratio when projecting a white image, that is,
A configuration in which the degree of influence of the luminance of the projection area on the luminance of the non-projection area may be stored. In this configuration, the luminance of the non-projection area during image projection may be corrected by reflecting the average luminance value of the projected image and the degree of the influence.

DESCRIPTION OF SYMBOLS 1 ... Projector, 10R, 10G, 10B ... LED, 16 ... Projection lens, 17 ... Zoom ring, 18 ... Image pick-up device, 20 ... Liquid crystal control circuit, 30 ... Image analysis part, 32 ... Reset determination part, 34 ... Brightness determination 36, LUT, 38, light source control circuit, 40R, 40G, 40B, light source driving unit, 100R, 100G, 100B, liquid crystal light valve, 200, screen.

Claims (7)

A light source unit for supplying light;
An optical modulator that modulates light from the light source unit according to a video signal that defines an image to be projected, and generates a modulated image;
A light projection unit that projects a modulation image by the light modulator onto a projection area of the projection surface;
A storage unit for storing a relationship between a luminance of a non-projection area where the modulated image is not projected on the projection surface and a projection luminance when an image is projected on the projection area;
A luminance acquisition unit that acquires the luminance of the projection area and the luminance of the non-projection area on the projection plane;
A luminance determination unit that reads out the projection luminance corresponding to the acquired luminance of the non-projection area from the storage unit;
A light source control unit that controls the light source unit so that the luminance of the acquired projection area becomes the projection luminance;
A projector comprising: The storage unit
Storing the ratio of the luminance of the non-projection area and the luminance of the projection area when the light source unit is off or when a black image is projected on the projection area;
The brightness determination unit
The projector according to claim 1, wherein the acquired brightness of the non-projection area is corrected to a value obtained by multiplying the brightness of the non-projection area by the ratio, and a target brightness corresponding to the value is read out. The brightness determination unit
The projector according to claim 2, wherein the target luminance is corrected according to an average luminance value in a portion corresponding to the projection area in the image defined by the video signal. A reset determining unit that causes the luminance determining unit to correct the target luminance again when the acquired luminance of the non-projection area changes beyond a threshold value within a predetermined time. The projector according to claim 3. The light source controller is
When the light source unit is turned on,
The projector according to claim 1, wherein the amount of light supplied from the light source unit is gradually increased so that the acquired luminance of the projection area becomes the target luminance. The sensor according to any one of claims 1 to 5, further comprising a sensor that detects the brightness of the projection area and the brightness of the non-projection area of the projection plane and supplies the brightness to the brightness acquisition unit. A projector according to any one of the above. A light source unit for supplying light;
An optical modulator that modulates light from the light source unit according to a video signal that defines an image to be projected, and generates a modulated image;
A light projection unit that projects a modulation image by the light modulator onto a projection area of the projection surface;
A storage unit for storing a relationship between a luminance of a non-projection area where the modulated image is not projected on the projection surface and a projection luminance when an image is projected on the projection area;
A light source control method for a projector having
Obtaining the brightness of the projection area and the brightness of the non-projection area on the projection surface;
The projection brightness corresponding to the acquired brightness of the non-projection area is read from the storage unit,
A light source control method for a projector, characterized in that the light source unit is controlled so that the acquired luminance of the projection area becomes the target luminance.

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