JP2013041221A - Image projection apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image projection apparatus that projects images from a position displaced from a front face of a screen and compensates brightness inclination in a display screen caused by a difference in the angle of incidence on the screen to display high-quality images.SOLUTION: An image projection apparatus projects images from a position displaced from a front face of a screen, and includes shading compensation means for compensating brightness inclination that is generated from a distal end of a display screen on the screen to a near end of the display screen to a video signal for optically modulating the projected light.

Description

  The present invention relates to a control technique for an image projection apparatus.

In recent years, image projection apparatuses called ultra-short focus projectors have been commercialized. The ultra-short focus projector has the same projection screen size as the conventional one, but has a shorter spatial distance to the projection surface (screen). Since the distance to the projection surface is short, there are the following advantages.
1. Since the image projector can be used near the screen, the space can be used effectively, which is suitable for a narrow conference room.
2. Since the explanation light is hard to hit the explainer, it is not dazzling and there is no reflection.
3. Since the image projection apparatus and the observer are separated from each other, the heat generation and noise from the image projection apparatus are not bothered.

  As described above, since the projection distance of the ultra-short focus projector is short, the projector is disposed below or above the screen. In such an arrangement, the angle of light projected on the screen surface becomes shallow, and the amount of reflected light increases. In particular, since the incident angle on the side farther from the image projection apparatus becomes shallower than the side closer to the image projection apparatus, the amount of reflection is further increased. For this reason, there is a problem that a luminance difference occurs in the same screen.

  FIG. 1 is a diagram illustrating an example of projection onto a screen of an image projection apparatus. As shown in FIG. 1, the ultra-short focus type image projector 1 is installed at a position close to the screen 6 for displaying an image, and is arranged outside the display screen so that the display screen does not cover the image projector 1. The The distance between the screen 6 and the image projector 1 is approximately several tens of centimeters, and the projection screen size increases as the distance increases.

  If the display screen end (display screen far end) on the side far from the image projection apparatus 1 of the image projected on the screen 6 is point a, and the near display screen end (display screen near end) is point b, the point a It can be seen that the incident angle θb at the point b is larger than the incident angle θa, and the incident angles are different at both screen edges.

  A mat screen generally used widely as the screen 6 obtains brightness by reflecting incident light from the front of the screen to the front. A considerable amount of light incident obliquely reflects to the opposite side of the incident light at the same angle as the incident angle. When the incident angle to the screen is shallow as in the ultra-short focus projector, the angle of the reflected light on the opposite side to the incident side is inevitably shallow, and the amount of reflection off the screen increases, resulting in a decrease in brightness. The user will see the video.

  FIG. 2 is a diagram showing an example of the state of reflection at the far end of the display screen. Since the incident angle θa at the point a at the far end of the display screen is small, reflection to the outside of the screen increases and reflection to the front (diffusion). Decreases and the luminance decreases.

  FIG. 3 is a diagram showing an example of reflection at the near end of the display screen. Since the incident angle θb at the point b at the near end of the display screen is larger than the incident angle θa at the point a, the luminance decrease is relatively small. .

  Therefore, a gradation-like luminance difference occurs in which the luminance on the upper side of the display screen is the lowest and the luminance gradually increases downward, and a high-quality image cannot be displayed. This is an optical inconvenience that cannot be avoided unless some device is applied to the screen itself.

  On the other hand, Patent Document 1 discloses a technique for acquiring color unevenness in each display panel in advance for the purpose of correcting color unevenness in a display screen, and performing level correction based on this to perform color unevenness correction. Has been.

  However, Patent Document 1 suppresses color unevenness of an image caused by various variations such as input / output characteristics of a display device, electrical characteristics of a constituent circuit, and optical characteristics of an optical device. It cannot be applied to the resolution of the luminance difference caused by it.

  The present invention has been proposed in view of the above-described conventional problems, and an object of the present invention is to provide an image projection apparatus that projects an image from a position displaced from the front with respect to the screen, and a difference in incident angle to the screen. An object of the present invention is to provide an image projection apparatus capable of displaying a high-quality image by correcting the luminance gradient in the screen caused by the above.

  In order to solve the above problems, in the present invention, an image projection apparatus projects an image from a position displaced from the front with respect to the screen, and the image signal for optically modulating the projection light is projected on the screen. Shading correction means is provided for performing correction to cancel out the luminance gradient generated from the far end of the display screen toward the near end of the display screen.

  In the present invention, in an image projection apparatus that projects an image from a position displaced from the front with respect to the screen, a high-quality image can be obtained by correcting the luminance gradient in the screen due to the difference in the incident angle on the screen. Can be displayed.

It is a figure which shows the example of the projection with respect to the screen of an image projector. It is a figure which shows the example of the mode of reflection in a display screen far end. It is a figure which shows the example of the mode of the reflection in a display screen near end. It is a figure which shows the example of the external appearance of the image projector concerning one Embodiment of this invention. It is a figure which shows the example of arrangement | positioning of an image projector. It is a figure which shows the hardware structural example of an image projector. It is a figure which shows the example of a function structure concerning the image projection of an image projector. It is a figure which shows the example of the angle detection by an acceleration sensor. It is a figure which shows the structural example of a shading correction | amendment part. It is a figure which shows the example of a shading correction | amendment.

  Hereinafter, preferred embodiments of the present invention will be described. Although a vertical ultra-short focus projector will be described as an example of the image projection apparatus, the present invention is not limited to this, and any projector can be targeted.

  FIG. 4 is a diagram showing an example of the appearance of the image projector 1 according to the embodiment of the present invention.

  The image projection apparatus 1 of the present embodiment emits light from a projection port 2 on the upper surface of the apparatus and projects an image on a screen 6. The image projection apparatus 1 has a projection screen size similar to that of a general projector, but is characterized by a short distance to the projection surface. As a technique for realizing such an ultrashort focus, for example, there is a projection optical system described in Japanese Patent Application Laid-Open No. 2007-316674.

  The image projection apparatus 1 is also characterized by a vertical shape. The vertical type has the advantage that the installation space can be reduced.

  The operation unit 3 disposed on the upper surface of the apparatus includes a plurality of buttons, and can be used for power ON / OFF, various setting operations, input signal switching, and the like.

  A connection terminal 4 and a vent hole 5 are arranged on the side of the apparatus. Cables from various video devices such as computers and DVD players can be connected to the connection terminal 4 to input video signals. In addition, the air vent 5 uses the internal fan to intake and exhaust air with the outside air. This cools the lamp and optical system in the housing.

  FIG. 5 is a view showing an example of the arrangement of the image projection apparatus 1 and is a view of a conference room and the like as viewed from the side.

  The image projection apparatus 10 is a projector having a normal focal length shown for comparison. In the case of a normal focal length, it is necessary to install it at a position somewhat away from the screen 6 (near the center of the table 8 in the figure). On the other hand, since the image projection apparatus 1 of the present embodiment has a short focal length, it can be installed in the vicinity of the screen 6 (on the table 9 in the figure).

  In the case of a normal image projection apparatus 10, it is necessary to secure an installation space on the table 8. In addition, since the presenter will explain in a standing manner in front of the screen 6, the projected light from the image projection device 10 may be dazzled, or the projected light may be blocked by a part of the body and a part of the projected image may not be seen. Such a problem occurs. Further, since participants such as conferences sit around the table 8, heat generation and noise from the image projection device 10 become problems.

  In the case of the image projection apparatus 1, since it is installed in the vicinity of the screen 6, it is not necessary to prepare an installation space on the table 8. Further, since the presenter can explain by standing in front of the image projecting apparatus 1, it does not feel the projected light dazzling or obstruct the projected light. Since the image projection apparatus 1 is also away from the participants, it does not suffer from heat generation or noise. Moreover, since it is a vertical type, an installation space can be reduced. The image projection apparatus 1 can be a taller vertical type, and the installation space can be further reduced.

  FIG. 6 is a diagram illustrating a hardware configuration example of the image projection apparatus 1.

  The image projection apparatus 1 includes a lamp 104, an illumination optical system 103, a light modulator 102, and a projection optical system 101. Light emitted from the lamp (light source) 104 is applied to the light modulator 102 via the lens or mirror of the illumination optical system 103. The optical modulator 102 includes a liquid crystal panel or a digital mirror device (DMD), and can form an image based on a video signal input from the outside. The light modulated by the light modulator 102 is projected onto the screen 6 (FIGS. 1 and 2) via the lens and mirror of the projection optical system 101.

  Further, the image projection apparatus 1 includes a power source 105 and supplies power to the lamp 104, the light modulator 102, the fan 118, and the like.

  The optical modulator 102, the lamp 104, and the power source 105 are provided with control units (106, 107, and 108) that control their operations, and these are controlled centrally by the system control unit 109.

  The system control unit 109 includes a CPU (Central Processing Unit), a memory, and the like, and controls the operation of the entire image projection apparatus 1 based on various input information.

  An external video signal is input to the image projection apparatus 1 via the external interface 115. After the video signal is processed by the video signal processing unit 114 and the system control unit 109, a command is sent to the optical modulator control unit 106 and reflected in the operation of the optical modulator 102.

  When the user operates the image projection apparatus 1, the operation panel 111 or the remote controller 113 is used. The operation on the operation panel 111 is directly notified to the system control unit 109. Further, the operation on the remote controller 113 is notified to the system control unit 109 via the remote control receiver 112. Receiving the notification, the system control unit 109 performs processing corresponding to the notification.

  Further, the user can know the state of the image projector 1 via the display device 110. The display device 110 is configured by, for example, an LED (Light Emitting Diode). The display device 110 receives a notification from the system control unit 109 in response to ON / OFF of the power of the image projection device 1 or an error occurrence, and notifies the user of the device state by turning on / off the LED. Can do.

  The image projection apparatus 1 includes various sensors such as an acceleration sensor 116 and a temperature sensor 117.

  The acceleration sensor 116 can measure the inclination of the image projector 1. The measured tilt information is notified to the system control unit 109 and can be used for keystone correction (keystone distortion correction) of the projected image.

  The temperature sensor 117 can measure the temperature in the image projector 1. The measured temperature information is notified to the system control unit 109, and the rotation of the fan 118 is changed in order to bring the image projection apparatus 1 into an appropriate temperature state. If the temperature is too high, the projection is stopped as a system abnormality. Control.

  The fan 118 is used for intake and exhaust of air inside and outside the image projection apparatus 1. In addition, the air flow in the housing is controlled, and air is applied to high-temperature components to cool the air to an appropriate temperature.

  FIG. 7 is a diagram illustrating an example of a functional configuration related to image projection of the image projection apparatus 1.

  7, with respect to image projection, an analog-digital converter (ADC) 121, an angle-of-view converter 122, a shading corrector 123, an acceleration sensor 116, a gamma corrector 124, a panel driver 125, and an illumination optical system. 103, a display panel 129, and a projection optical system 101. The illumination optical system 103 includes a light source 126, a condenser lens 127, and a filter 128, and the projection optical system 101 includes a filter 130 and a projection lens 131. The display panel 129 corresponds to the light modulator 102 (FIG. 6). In addition, although the case where the shading correction part 123 is provided in the front | former stage of the gamma correction part 124 is shown in figure, the shading correction part 123 may be provided in the back | latter stage of the gamma correction part 124, and the process of the shading correction part 123 is gamma. It may be performed simultaneously by the correction unit 124.

  In operation, when a video signal is input from the input terminal, in the case of an analog signal, the analog / digital conversion unit 121 converts the analog video signal into a digital video signal. Thereafter, most processing is performed in the state of digital signals. When the input video signal is a digital signal, the analog-digital conversion unit 121 can be omitted.

  For the digitized video signal, the angle-of-view conversion unit 122 converts the angle of view according to the number of display pixels on the display panel 129, and performs keystone correction based on the angle information provided from the acceleration sensor 116. . When the image projection apparatus 1 is tilted in the direction to be looked up with respect to the screen 6 (FIG. 4), the display image has a trapezoidal shape in which the upper side of the display image is widened. Either spreading or performing both of them simultaneously is performed.

FIG. 8 is a diagram showing an example of angle detection by the acceleration sensor 116. As shown in the drawing, for example, the acceleration sensor 116 is inclined 45 degrees with respect to the image projecting apparatus 1 and arranged vertically. The acceleration sensor 116 can measure the acceleration g _{X in} the X-axis direction and the acceleration g _Y in the Y-axis direction. At this time, the inclination angle θ (the angle formed by gravity from the + X axis to the + Y axis) can be calculated by the following equation using the acceleration values g _X and g _Y.

θ = tan ⁻¹ (g _Y / g _X )
Returning to FIG. 7, the shading correction unit 123 performs luminance correction on the video signal whose angle of view has been converted, by applying shading having a reverse characteristic to the luminance gradient caused by the difference in the incident angle on the screen. Further, the shading correction unit 123 adjusts the amount of brightness correction based on the angle information given from the acceleration sensor 116.

  FIG. 9 is a diagram illustrating a configuration example of the shading correction unit 123, which includes a scanning line position detection unit 1231, a correction value acquisition unit 1232, a correction value output unit 1233, and a correction execution unit 1234.

  The scanning line position detection unit 1231 detects the position of the scanning line (horizontal video signal) from the video signal.

  The correction value acquisition unit 1232 acquires a correction value from the correction value output unit 1233 based on the position of the scanning line detected by the scanning line position detection unit 1231 and the angle information of the image projection apparatus 1 provided from the acceleration sensor 116.

The correction value output unit 1233 holds a correction value corresponding to the position of the scanning line and the angle of the image projection apparatus 1 as a table, or generates a correction value by a mathematical expression from the position of the scanning line and the angle of the image projection apparatus 1. The correction value is output by, for example. The decrease in luminance based on the incident angle to the screen 6 is larger toward the upper side of the screen, and the decrease in luminance is smaller toward the lower side. In addition, when the image projection apparatus 1 is tilted in a direction facing the screen 6, the luminance reduction on the upper side of the screen becomes large. Therefore, when the position of the scanning line from the upper side of the screen is n, the inclination angle in the direction in which the image projection apparatus 1 looks up with respect to the screen 6 is θ, and the constants are c ₁ , c ₂ , c ₃ , the correction value is, for example, ,
Correction value = c ₁ −c ₂ · n + c ₃ · n · θ
Can be expressed as

  Note that the positional relationship between the ultrashort focus projector and the screen is very important, and a very large distortion occurs in the display screen, for example, when the image projector 1 is installed at an angle. For this reason, the positional relationship between the image projection apparatus 1 and the screen 6 is defined within a limited range to some extent. For this reason, it is considered that the tilt angle of the image projection apparatus 1 falls within a certain small range. Therefore, under such a condition, it is not necessary to consider the variation of the correction value with respect to the angle.

  In addition, although the case where it projected on the screen upward from the bottom was demonstrated, the case where it projects on the screen from the top may be sufficient. Moreover, the case where it projects from the right side or the left side of a screen may be sufficient. In this case, the “scanning line position” for determining the correction value can be dealt with by replacing it with “scanning position”.

  The correction execution unit 1234 executes shading correction by, for example, multiplying the video signal by the correction value acquired by the correction value acquisition unit 1232.

  FIG. 10 is a diagram illustrating an example of shading correction. As shown on the right side of the figure, there is a dark-to-bright brightness gradient from point a at the far end of the display screen to point b at the near end of the display screen. Here, as shown on the left side of the figure, if the original video signal in the V period (vertical period) is V indicated by a broken line, the luminance is higher than the original video signal on the point a side at the far end of the display screen. The corrected video signal V ′ is obtained by continuously performing correction so that the luminance is lower than that of the original video signal at the point b near the display screen. As a result, the luminance gradient due to the incident angle with respect to the screen is canceled, and the same luminance can be reproduced for the video signal of the same level.

Returning to FIG. 7, the gamma correction unit 124 performs gamma correction on the video signal subjected to the shading correction. In general, the display device is not linear with respect to the intensity of the video signal, and the screen output y can be approximated to y = x ^γ with respect to the input x. Therefore, a value γ corresponding to the characteristics of the display panel 129 is set in advance. By correcting each color signal (R, G, B) of the video signal to the [1 / γ] power, the screen output is corrected so as to change linearly with respect to the input.

  Based on the gamma-corrected video signal, the panel drive unit 125 converts the drive signal into a drive signal suitable for the display panel 129 and drives the display panel 129.

  On the other hand, the light emitted from the light source 126 enters the display panel 129 through the condenser lens 127 and the filter 128 of the illumination optical system 103, and the light light-modulated by the video signal by the display panel 129 is the filter 130 and the projection optical system 101. The light is projected onto the screen 6 through the projection lens 131.

  The present invention has been described above by the preferred embodiments of the present invention. While the invention has been described with reference to specific embodiments, various modifications and changes may be made to the embodiments without departing from the broad spirit and scope of the invention as defined in the claims. Obviously you can. In other words, the present invention should not be construed as being limited by the details of the specific examples and the accompanying drawings.

DESCRIPTION OF SYMBOLS 1 Image projector 101 Projection optical system 102 Light modulator 103 Illumination optical system 104 Lamp 105 Power supply 106 Light modulator control unit 107 Lamp control unit 108 Power supply control unit 109 System control unit 110 Display apparatus 111 Operation panel 112 Remote control receiver 113 Remote control 114 Video signal processing unit 115 External interface 116 Acceleration sensor 117 Temperature sensor 118 Fan 121 Analog / digital conversion unit 122 Angle of view conversion unit 123 Shading correction unit 1231 Scanning line position detection unit 1232 Correction value acquisition unit 1233 Correction value output unit 1234 Correction execution unit 124 Gamma correction unit 125 Panel drive unit 126 Light source 127 Condensing lens 128 Filter 129 Display panel 130 Filter 131 Projection lens 2 Throw Mouth 3 Operation unit 4 connecting terminals 5 vent 6 Screen 7 camera 8 table nine 10 image projector

JP 2001-209358 A

Claims (3)

An image projection device that projects an image from a position displaced from the front with respect to a screen,
An image projection apparatus comprising: a shading correction unit that performs correction to cancel a luminance gradient generated from a display screen far end on the screen toward a display screen near end with respect to a video signal that optically modulates projection light . The image projector according to claim 1,
The shading correction means includes
Means for detecting the scanning position of the video signal;
Means for obtaining a correction value according to the scanning position of the detected video signal;
An image projection apparatus comprising: means for performing correction on a video signal based on an acquired correction value. The image projection device according to claim 1, wherein
The shading correction means includes
An image projection apparatus, wherein a correction amount is adjusted based on an inclination angle of the image projection apparatus.

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