JP2007328074A - Light source control device - Google Patents

Abstract

Provided is a light source control device capable of changing to an arbitrary amount of light at high speed and accurately even if individual light sources vary or deteriorate with time.
A plurality of light sources 101 to 103 for outputting light of different wavelengths, a light source control means 104 for outputting a light source control signal 112 for controlling a lighting period and a light amount of the plurality of light sources, and a projection means 107 for projecting an image. And an image generating means 108 that is arranged between the plurality of light sources and the projecting means 107 and generates an image depending on whether or not the light beams of the plurality of light sources are guided to the projecting means 107, and the light flux is guided in the direction of the projecting means 107. Light quantity measurement means 109 for measuring the light quantity of the light source during a period when the light source is not, storage means 110 for holding the value of the light source control signal 112 and the light quantity measurement value 115 measured by the light quantity measurement means 109, and video information based on the video information Video processing means 111 for outputting a signal 117, a light intensity instruction signal 119, and a light source switching signal 120 is provided.
[Selection] Figure 1

Description

  The present invention relates to a light source control device such as an LED or a laser, and more particularly to a light amount modulation technique of a light source suitable for video display by a projector or the like.

  In recent years, semiconductor light emitting devices such as LEDs and lasers with a large amount of light have been developed, making use of features that can be switched on and off at high speed and that the amount of light can be easily changed. It is beginning to be installed.

  With respect to devices that display video, screens are becoming larger and devices are becoming thinner, and in particular, projectors using devices in which liquid crystals and minute mirrors are integrated have been developed.

  As a light source of a conventional projector, a halogen lamp, a metal halide lamp, an ultrahigh pressure mercury lamp, or the like is used. Since these lamps have an emission spectrum over the entire visible range, images are often expressed using the three primary colors of red, green, and blue light obtained by optical elements such as color filters and dichroic mirrors. However, in such a lamp, it takes time until the brightness stabilizes immediately after lighting, the range of light amount adjustment is limited, or high-speed light amount adjustment is difficult. For this reason, a movable diaphragm is provided to adjust the amount of light. As a result, it is possible to realize black floating due to leakage light or scattered light generated in the optical system, or to increase the gradation of the dark part (see, for example, Patent Document 1).

  On the other hand, as compared with the above-mentioned lamp, a semiconductor light emitting element that has a long life, can be switched on and off at high speed, and can easily change the amount of light has been used as a light source.

  However, as a light source for image display such as a projector, the amount of light is not yet sufficient, and thus a plurality of semiconductor light emitting elements are used to secure a necessary amount of light.

  Further, the amount of emitted light with respect to the current flowing through the semiconductor light emitting element has a non-linear relationship, and generally has a characteristic that the amount of light does not halve even if the current value is halved.

  Furthermore, there are individual differences in the light amount, emission spectrum, deterioration with time, etc. of individual semiconductor light emitting elements due to variations in manufacturing processes such as impurity concentration, crystal defects, and electrode formation.

Since the luminance and chromaticity of the image change due to the characteristics of the semiconductor light emitting element as described above, it is necessary to constantly monitor the light source and display an image with normal luminance and chromaticity. For example, a projector has been proposed in which a common photoelectric conversion element that measures the light amount of each light source is provided, and feedback control is performed so that the light source amounts of red, green, and blue light sources have predetermined values. Thereby, stable light quantity control can be realized (see, for example, Patent Document 2).
JP 2002-72361 A JP 2004-163527 A

  However, the technique described in Patent Document 1 requires a mechanical mechanism called a movable diaphragm that operates at high speed, and an alternative light quantity control means is desired from the viewpoint of member cost and operating life. In the technique described in the above-mentioned document 2, it is possible to keep a predetermined light source light amount. For example, the setting value of the drive current necessary for halving the light source light amount or changing it by 10% is set. Since it is not known, it is difficult to realize control that changes the amount of light at high speed and accurately, and it is difficult to realize high-quality video expression.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the conventional problems and to provide a light source control device capable of switching the light amount of a light source at high speed and accurately.

  In order to solve the conventional problems, a light source control device according to the present invention includes a plurality of light sources that output light of different wavelengths, and a light source that outputs a light source control signal for controlling lighting periods and light amounts of the plurality of light sources. Control means, projection means for projecting an image on a screen arranged inside or outside the apparatus, and arranged between the plurality of light sources and the projection means, and guides light beams from the plurality of light sources to the projection means. A video generation unit that generates the video depending on whether or not, a light amount measurement unit that measures at least one light amount among the plurality of light sources during a period in which the video generation unit does not guide the light flux to the projection unit, A storage means for holding a light source control signal value and a light quantity measurement value measured by the light quantity measurement means, and a video information signal is output to the video generation means based on video information from the outside. A video processing unit that outputs a light amount instruction signal for instructing a light amount of a light source to the light source control unit, and that outputs a light source switching signal for switching lighting of the plurality of light sources to the light source control unit, the light amount measuring unit, and the storage unit; It is characterized by providing.

  Further, in the light source control device, the plurality of light sources are LEDs or lasers.

  Further, in the light source control device, the image generation means is a reflective device in which a large number of minute and angle-controllable mirrors are arranged in a matrix, and when the mirror reflects the light beam at a first angle, An image generating means guides the light flux to the projection means, and the image generating means guides the light flux to the light quantity measuring means when the mirror reflects the light flux at a second angle. It is.

  Further, in the light source control device, the light source control means outputs the light source control signal having a light source light amount different from that during video projection during a period when the light flux is not guided to the projection means, and the storage means The control signal value and the light quantity measurement value are held as a correlation table.

  Furthermore, in the light source control device, the light source control means outputs the light source control signal so as to obtain a light source light amount corresponding to the light amount instruction signal at the time of video projection, using the correlation table. It is.

  According to the light source control device of the present invention, since the light amount characteristics of the light source are measured in advance during a period in which no image is projected, even if variations in individual light sources or deterioration with time occur, the light source can be controlled at any light amount. In addition, switching can be performed accurately, and high-quality video expression can be realized.

  Embodiments of a light source control device according to the present invention will be described below in detail with reference to the drawings.

  The first embodiment of the present invention assumes a light source control device that projects an image by sequentially turning on a plurality of light sources that output light of different wavelengths.

  FIG. 1 is a configuration diagram of a light source control device in Embodiment 1 of the present invention. In FIG. 1, reference numerals 101, 102, and 103 denote light sources, each emitting light having a different wavelength. In general, three colors of red, green, and blue are often used to represent an image. Here, 101 is a red light source, 102 is a green light source, and 103 is a blue light source. In particular, a semiconductor light emitting element such as an LED or a laser that can switch the amount of emitted light at high speed is desirable. Thereby, for example, it is possible to switch the three colors of red, green, and blue many times during a period of projecting one frame of video, and it is possible to prevent the human eye from recognizing the color switching. In addition, luminance gradation expression and color gradation expression can be enhanced by freely changing the light amount of each color.

  A light source control unit 104 outputs a light source control signal 112 for controlling the amount of emitted light to the light sources 101, 102, and 103. The light source control signal 112 may be a setting value for determining a voltage value or a current value applied to the light sources 101, 102, 103, or may be a current value applied to the light sources 101, 102, 103 itself.

  Reference numeral 105 denotes a dichroic mirror that collects light beams from the light sources 101, 102, and 103. The light beams of the three colors are guided in the same direction by the reflection / transmission characteristics of the dichroic mirror. It is also possible to guide the light beam in the same direction by coupling optical fibers.

  Reference numeral 106 denotes a screen on which an image is projected, which may be provided inside the apparatus or may be disposed outside the apparatus.

  Reference numeral 107 denotes projection means for projecting an image on the screen 106, which is constituted by a lens or a mirror. It often has an image focus adjustment function and an enlargement ratio adjustment function.

  Reference numeral 108 denotes image generation means, which is a reflection type device in which a large number of minute mirrors are arranged in a matrix. It is arranged between the light sources 101, 102, 103 and the projection means 107, and switches whether to guide the light flux of the light sources 101, 102, 103 to the projection means 107 by reflecting at the first angle or the second angle. Can do. A light beam guided to the projection unit 107 is a first reflected light 113, and a light beam not guided to the projection unit 107 is a second reflected light 114.

  Reference numeral 109 denotes a light amount measuring unit that measures the light amount of the second reflected light 114 and outputs a light amount measurement value 115. It has sensitivity in the emission spectrum band of the light sources 101, 102, and 103, and can be composed of, for example, a silicon photodetector. If necessary, a lens or a mirror for collecting the second reflected light 114 may be provided.

  Reference numeral 110 denotes storage means for storing the light source control signal 112 and the light quantity measurement value 115. The stored light source control signal 112 and the correlation value 116 between the light quantity measurement values 115 are referred to by the light source control means 104.

  Reference numeral 111 denotes video processing means. Based on the projected video, the video information signal 117 and the video generation control signal 118 are output to the video generation means 108. Further, a light quantity instruction signal 119 is output to the light source control means 104. Further, the light source switching signal 120 is output to the light source control means 104, the light quantity measurement means 109, and the storage means 110.

  FIG. 2 is a timing chart showing an operation at the time of light quantity measurement of the light source control device according to the first embodiment of the present invention. The detailed operation of the light source control device will be described with reference to FIG.

  When the video is projected onto the screen 106, the video processing unit 111 outputs three video information signals 117 of red, green, and blue that can reproduce the luminance and color information of one frame of video to the video generation unit 108. . The image generation means 108 operates each minute mirror corresponding to the image information signal 117 based on the image generation control signal 118 representing the operation timing of the entire large number of minute mirrors arranged in a matrix, and thereby the light source 101, The luminous fluxes 102 and 103 are guided to the projection means 107. Further, the video processing unit 111 outputs a light source switching signal 120 synchronized with the video generation control signal 118 to the light source control unit 104 so that the light sources 101, 102, and 103 are sequentially turned on in a time division manner.

  The on / off waveform of the image generation means 108 shown in FIG. 2 is a high brightness with the minute mirror angle turned on in the first reflected light 113 direction and turned off in the second reflected light 114 direction. It is shown that a minute mirror corresponding to is turned on for a long time, and a minute mirror corresponding to low luminance is turned on for a short time. The light source switching signal 120 changes so that red, green, and blue are sequentially lit during one frame period, and the light source is switched during the entire off period in which all the minute mirrors are turned off. As a result, the three-color video information signal 117 and the light sources 101, 102, and 103 can be linked to project a video onto the screen 106.

  Here, the light beam is guided in a direction different from that of the projection unit 107 during the all-off period, and thus is not projected onto the screen 106. Therefore, it is allowed to turn on an arbitrary light source. For example, as in the light source control signal of the red light source shown in FIG. 2, the red light source 101 is turned on with a predetermined light amount during the period during which the red image is projected, and the red light source is gradually stepped in all the subsequent off periods. The light source control signal can be changed. The same applies to green and blue. It is also possible to light up while switching the light sources 101, 102, 103 during one all off period.

  By the way, since the light quantity measuring means 109 is arranged in the direction of the second reflected light 114, it is possible to measure the light quantity of the light sources 101, 102, and 103 that are turned on during all off periods. The light quantity measurement value in FIG. 2 is an example. While the red light source is turned on, the minute mirror operates according to the red component of the projected image, and the light flux from the off minute mirror is measured. When the entire off period is reached, the amount of light corresponding to the changed light source control signal is measured.

  The holding timing of the storage unit shown in FIG. 2 indicates a pulse signal for sampling the light quantity measurement value 115 obtained according to the light source control signal 112 switched during the all-off period. The timing for switching the light sources 101, 102, and 103 can be determined based on the light source switching signal 120. Further, the value of the light source control signal 112 can be a value that can be set from the outside, or can be switched in accordance with a predetermined procedure.

  As a result, a correlation table of the light source control signal 112 and the light quantity measurement value 115 is obtained in the storage unit 110 for each of the light sources 101, 102, and 103. Note that FIG. 2 shows an example in which sampling is performed once for each of the switched light source control signals, but in order to reduce the measurement error of the light amount measuring means 109, sampling is performed a plurality of times and averaging is performed. It is also possible to do. The number of light source control signals 112 to be switched during the all-off period is determined in consideration of the processing speed of the light source control means 104, the responsiveness of the light quantity measurement means 109, the time required for storage in the storage means 110, and the like. Can do.

  Table 1 shows an example of the correlation table. For example, for the red light source 101, when the light source control signal 112 is 1, the light quantity measurement value 115 is stored as 1000.

What should be noted here is that the characteristics of the light source are not necessarily linear. For example,
Looking at the red light source 101, the light quantity measurement value 115 is 8000 when the light source control signal 112 is 9, and the light source control signal 112 is 4 to obtain 4000, which is exactly half the light quantity. That is, it can be seen that it is not necessary to halve the light source control signal 112 when it is desired to halve the amount of light.

  By updating the correlation table as shown in Table 1 as needed, it is possible to refer to it when switching to an arbitrary light amount. If the light quantity measurement values 115 for as many light source control signals 112 as possible are stored, the light quantity can be switched with high accuracy, but the correlation table can also be reduced by applying a general interpolation technique or approximate curve. is there.

  Next, FIG. 3 shows a timing chart of each signal when the light amounts of the light sources 101, 102, and 103 are switched to half during the two-frame period. Here, the case where the light sources 101, 102, and 103 are switched once every frame period is also shown.

  The light amount instruction signal 119 is a signal for instructing the light amounts of the light sources 101, 102, and 103 when projecting an image. When the normal light amount is 100%, the light amount instruction signal 119 is 200% and halved when the light amount is to be doubled. If you want to, you can set 50%.

  For example, when the video processing unit 111 wants to switch the light amounts of the light sources 101, 102, and 103 according to the luminance or chromaticity feature amount of each frame of the video, the second and third frames in FIG. In addition, by setting the light amount instruction signal 119 to 50%, the light source control unit 104 refers to the correlation value 116 stored in the storage unit 110 and obtains the light source control signal 112 so that the light amount is halved. , 102, 103 are realized by outputting a light source control signal 112.

  Since the light quantity measurement means 109 measures the light quantity of the second reflected light 114 in advance and the light quantity measurement value 115 is stored in the storage means 110, the light quantity of the light sources 101, 102, 103 can be switched accurately. .

  Further, even when a detector for measuring the light quantity of the light sources 101, 102, and 103 is always provided separately and there is a means for feedback control, the present invention improves the convergence when the light quantity is switched. Is clear.

  2 and 3 show an example in which red, green, and blue are switched once each as a light source for image projection for one frame, but many red, green, and blue are used for one frame. You may switch repeatedly.

  Further, the order of switching the light sources and the lighting period need not be constant, and they may be switched in an arbitrary order and lighting time within one frame and over multiple frames.

  Further, the image generation means is not limited to the reflection type, and the same effect can be obtained by a transmission type using liquid crystal or the like.

  As described above, the light source control means of the present invention changes the light amount of the light sources 101, 102, and 103 in one frame time or shorter time of the video, thereby expressing the luminance gradation and the color gradation. It is effective for enhancing expression.

  Further, the longer the period during which the light amounts of the light sources 101, 102, and 103 are reduced, the ratio of leakage light and scattered light generated in the optical system is reduced, so that the dark part is expressed darker. It is particularly effective.

  The light source control device according to the present invention measures the light quantity characteristics of the light source in advance during the period when the image is not projected. It can be changed accurately and is useful for realizing high-quality video expression.

1 is a configuration diagram of a light source control device in Embodiment 1 of the present invention. FIG. 3 is a timing chart showing an operation at the time of light amount measurement of the light source control device according to the first embodiment of the present invention. FIG. 3 is a timing chart showing an operation at the time of light quantity switching of the light source control device according to the first embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Red light source 102 Green light source 103 Blue light source 104 Light source control means 105 Dichroic mirror 106 Screen 107 Projection means 108 Image generation means 109 Light quantity measurement means 110 Storage means 111 Image processing means 112 Light source control signal 113 First reflected light 114 Second Reflected light 115 Light quantity measurement value 116 Correlation value 117 Video information signal 118 Video generation control signal 119 Light quantity instruction signal 120 Light source switching signal

Claims (5)

A plurality of light sources each outputting light of a different wavelength;
A light source control means for outputting a light source control signal for controlling a lighting period and a light amount of the plurality of light sources;
Projection means for projecting an image onto a screen arranged inside or outside the apparatus;
A video generation unit that is arranged between the plurality of light sources and the projection unit and generates the video depending on whether or not light beams from the plurality of light sources are guided to the projection unit;
A light amount measuring unit that measures at least one light amount of the plurality of light sources during a period in which the image generation unit does not guide the light flux to the projection unit;
Storage means for holding the value of the light source control signal and the light quantity measurement value measured by the light quantity measurement means;
Based on video information from the outside, a video information signal is output to the video generation unit, a light amount instruction signal for instructing a light amount of a light source is output to the light source control unit, the light source control unit, the light amount measurement unit, and the storage Video processing means for outputting a light source switching signal for switching lighting of the plurality of light sources to the means;
A light source control device comprising: The light source control device according to claim 1, wherein the plurality of light sources are LEDs or lasers. The image generation means is a reflective device in which a large number of mirrors that can be controlled in angle are arranged in a matrix, and when the mirror reflects the light beam at a first angle, the image generation means performs the projection. Directing the luminous flux to the means, and when the mirror reflects the luminous flux at a second angle, the image generating means guides the luminous flux to the light quantity measuring means;
The light source control device according to claim 1. The light source control means outputs the light source control signal having a light source light amount different from that during video projection during a period when the light flux is not guided to the projection means,
The light source control apparatus according to claim 1, wherein the storage unit holds the value of the light source control signal and the light quantity measurement value as a correlation table. The light source control means uses the correlation table to output the light source control signal such that a light source light amount corresponding to the light amount instruction signal at the time of video projection is obtained.
The light source control device according to claim 4.

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