JP5115711B2 - Liquid crystal projector and projection image adjustment method thereof - Google Patents

Description

  The present invention relates to a liquid crystal projector that generates projection image light by irradiating a liquid crystal panel with light generated by an AC-driven light source.

  FIG. 4 is a block diagram showing the configuration of this type of liquid crystal projector, which is disclosed in Japanese Patent Laid-Open No. 2003-156798.

  The projector 10 receives the image signal VS and converts it into image data that can be processed by the projector 10, an image processing unit 20 that performs various image processing on the image data, a liquid crystal panel 32, and an image Based on the data, a liquid crystal panel drive unit 30 that generates a drive signal for driving the liquid crystal panel 32, an illumination device 50 that illuminates the liquid crystal panel 32, and transmitted light that has passed through the liquid crystal panel 32 is projected onto the screen SC. A projection optical system 58. The illumination device 50 includes a light source lamp 52, a lamp control unit 54, and a lamp driving unit 56.

The light source lamp 52 is AC driven, and flickering occurs in the projected image light when the driving frequency of the light source lamp 52 and the driving frequency of the liquid crystal panel 32 are asynchronous. In Patent Document 1, in order to suppress flickering, when the lamp control unit 54 can synchronize the vertical driving frequency of the liquid crystal panel 32 and the driving frequency of the light source lamp, the light source lamp 52 is set so that both are synchronized. It is disclosed to control and set the frequency of an AC driven lamp.
JP 2003-156798 A

  The lamp current for driving the AC lamp has a pulse period t1 in which pulses as shown in FIG. 5 are superimposed in order to suppress the flickering of the discharge arc generated during operation of the lamp. The pulse period t1 is determined in advance depending on the lamp type, driving power, and the like. In the pulse period t1, since the power supplied to the lamp is increased, the lamp luminance is increased, and as a result, regions having different brightness are generated in the projected image.

  FIG. 6 is a diagram showing changes in the projected image during the pulse period t1, with the projected image on the left side and the brightness of the projected image on the right side (increasing brightness toward the right). As shown in FIG. 6, the luminance increases during the pulse period t1, and is perceived as horizontal stripe noise.

  The present invention provides a technique capable of preventing the occurrence of horizontal stripe noise in a projected image projected on a screen while suppressing the occurrence of flicker in a liquid crystal projector that uses an AC-driven lamp as a light source. Objective.

The liquid crystal projector of the present invention includes a light source driven by an alternating current and a liquid crystal panel, and generates a projection image light by irradiating the liquid crystal panel with light generated by the light source.
A projector control unit for outputting a panel drive vertical synchronization signal for determining a vertical blanking period of the liquid crystal panel;
A lamp current generation unit that inputs the panel drive vertical synchronization signal and generates the alternating current in which a current is increased during a predetermined pulse period based on an input timing of the panel drive vertical synchronization signal;
A video signal representing an image to be displayed on the liquid crystal panel, inputs the said panel driving vertical synchronizing signal, wherein the amount is reduced predetermined the input video signal for a predetermined pulse duration, then the reduced having a video correcting unit which Ru to display images on the liquid crystal panel shown by the video signal.

A projection image adjustment method for a liquid crystal projector according to the present invention includes a light source driven by an alternating current and a liquid crystal panel, and a liquid crystal that generates projection image light by irradiating the liquid crystal panel with light generated by the light source. In the projection image adjustment method of the projector,
Based on the panel drive vertical synchronization signal that determines the vertical blanking period of the liquid crystal panel, a predetermined pulse period generates the alternating current in which the current is increased,
Wherein the panel driving vertical synchronizing signal the pulse period determined in advance based on reducing the amount predetermined the input video signal, Ru to display the image represented by the video signal obtained by the reduction in the liquid crystal panel .

  In the present invention configured as described above, the generation of flicker is suppressed by providing the pulse period, and the luminance of the video signal is reduced during the pulse period, thereby preventing the occurrence of horizontal stripe noise. it can.

  Next, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of an embodiment of a liquid crystal projector according to the present invention.

  As shown in FIG. 1, the liquid crystal projector of the present embodiment includes a video processing unit 101, a video correction unit 102, a liquid crystal panel driving unit 103, a liquid crystal panel 104, a projection lens 105, a projector control unit 106, a lamp control unit 107, The lamp control unit 107 and the lamp drive unit 108, the lamp 109, the screen 110, and the input unit 111 constitute a lamp current generation unit.

  The video processing unit 101 receives various types of video signals such as NTSC system, PAL system, and personal computer output, and converts them into video signals of a format that the video correction unit 102 performs processing.

  The input unit 111 is provided to correct brightness, contrast, sharpness of a projected image, image distortion caused by an arrangement state of a liquid crystal projector, and the like. The image adjustment signal S4 shown is output to the image correction unit 102.

  The projector control unit 106 outputs a panel driving vertical synchronization signal S1 for determining the pulse period t1 to the video correction unit 102 and the lamp control unit 107.

  The video correction unit 102 receives the video signal from the video processing unit 101, the panel drive vertical synchronization signal S1 from the projector control unit 106, and the video adjustment signal S4 sent from the input unit 111.

  The video correction unit 102 adjusts the luminance, contrast, sharpness, and image distortion of the projected image on the video signal from the video processing unit 101 based on the video adjustment signal S4 from the input unit 111. The brightness of the projected image is further adjusted in accordance with the panel drive vertical synchronization signal S 1 from the projector control unit 106 and supplied to the liquid crystal panel drive unit 103. The liquid crystal panel driving unit 103 generates a liquid crystal panel driving signal for driving the liquid crystal panel 104 according to the input video signal, and supplies the liquid crystal panel driving signal to the liquid crystal panel 104.

  When the lamp control unit 107 receives the panel drive vertical synchronization signal S1 from the projector control unit 106, the lamp control unit 107 generates a lamp current drive signal S2 synchronized with the panel drive vertical synchronization signal S1.

  FIG. 2 is a diagram showing the relationship between the panel drive vertical synchronization signal S1 and the lamp current drive signal S2.

  The panel driving vertical synchronization signal S1 is a signal including a pulse that falls during the period t2 every period T, and the lamp current driving signal S2 is an AC signal. A period t2 included in the panel driving vertical synchronization signal S1 is used as a vertical blanking period for driving the liquid crystal panel 104.

  When the lamp control unit 107 detects a pulse included in the panel driving vertical synchronization signal S1, the lamp control unit 107 generates a lamp current driving signal S2 in which the polarity is inverted by inverting the pulse during the pulse period t1 after the delay time td. The pulse period t1 is a predetermined time, and the occurrence of flicker is suppressed by providing the pulse period t1.

  A specific circuit for realizing the lamp control unit 107 includes, for example, a circuit using a one-shot multivibrator. The lamp current drive signal S2 can be generated by synchronizing with the panel drive vertical synchronization signal S1 as a trigger of the one-shot multivibrator.

  The lamp current driving signal S2 is supplied to the lamp driving unit 108, and the lamp driving unit 108 amplifies the lamp current driving signal S2 and supplies it to the lamp 109 as a lamp current S3.

  The liquid crystal panel 104 forms an image according to the liquid crystal panel drive signal sent from the liquid crystal panel drive unit 103. The lamp 109 is controlled in its lighting state and light amount by a lamp current S3 supplied from the lamp driving unit 108. The light generated by the lamp 109 passes through the liquid crystal panel 104 and is a lens 105 that is an imaging optical system. Projection image light is formed by passing through, and a projection image is formed on the screen 110.

  As described above, since the pulse is superimposed in the pulse period t1, the luminance of the light generated by the lamp 109 increases. In the present embodiment, in order to suppress an increase in the luminance of the projected image light, when the video correction unit 102 receives the panel drive vertical synchronization signal S1 from the projector control unit 106, the luminance level of the video signal within the pulse period t1. (Amplitude) is decreased by an amount determined by the transmittance of optical components such as the lamp 109 and the liquid crystal panel 104 by Y1.

  FIG. 3 is a diagram illustrating the luminance of the video signal output from the video correction unit 102 and the luminance of the projected image light projected onto the screen 110 when the luminance of the video signal input to the video processing unit 101 is constant. It is.

  The luminance characteristic of the video signal input to the video correction unit 102 is flat, but the video signal output from the video correction unit 102 has a luminance reduced by Y1 during the pulse period t1. The light emission luminance of the lamp 109 becomes brighter during the pulse period t1, but the luminance of the projected image light is shown in FIG. 3 because the luminance of the video signal output from the video correction unit 102 is reduced accordingly. It is so flat. In this way, by correcting the apparent change in luminance level, it is possible to suppress the occurrence of flicker and to prevent the occurrence of horizontal stripe noise in the projected image projected on the screen.

  As shown in FIG. 2, even if the pulse period t1 and the vertical blanking period t2 for driving the liquid crystal panel are set to the same timing by shifting the phase, such as by delaying the delay time td, a horizontal stripe shape is obtained when t1> t2. The noise width is reduced by the period t2, and the generation position only changes.

  In the above description, the case where the frequency of the vertical synchronizing signal S1 for driving the liquid crystal panel 104 and the lamp current S3 for driving the lamp 109 is 1: 1 has been described, but the frequency of the lamp current S3 is vertical synchronizing for panel driving. The present invention can also be applied to the case of an integral multiple of the signal S1. When the lamp current S3 is an integral multiple of the panel driving vertical synchronization signal S1, the pulse period exists for an integer, and therefore horizontal stripe noise is generated for an integer. Therefore, it is sufficient to correct the luminance level of the video signal by an integral number during one frame period.

  The embodiment described above is a liquid crystal projector using a transmissive liquid crystal panel in which the transmitted light of the liquid crystal panel is projected onto the screen. However, the present invention is a reflective liquid crystal in which the reflected light of the liquid crystal panel is projected onto the screen. Of course, it can also be applied to a liquid crystal projector using a panel, and may be configured in this way.

It is a block diagram which shows the structure of one Embodiment of the liquid crystal projector by this invention. It is a figure which shows the relationship between the panel drive vertical synchronizing signal S1 and the lamp current drive signal S2 in FIG. It is a figure which shows the brightness | luminance of the video signal output from the video correction | amendment part 102 in FIG. 1, and the brightness | luminance of the projection image light projected on the screen 110. FIG. It is a block diagram which shows the structure of a liquid crystal projector. It is a figure which shows pulse period t1. It is a figure which shows the change of the projection image in the pulse period t1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Image processing part 102 Image correction part 103 Liquid crystal panel drive part 104 Liquid crystal panel 105 Lens 106 Projector control part 107 Lamp control part 108 Lamp drive part 109 Lamp 110 Screen 111 Input part S1 Panel drive vertical synchronizing signal S2 Lamp current drive signal S3 Lamp Current S4 Image adjustment signal

Claims (6)

In a liquid crystal projector comprising a light source driven by an alternating current, and a liquid crystal panel, and generating projection image light by irradiating the liquid crystal panel with light generated by the light source,
A projector control unit for outputting a panel drive vertical synchronization signal for determining a vertical blanking period of the liquid crystal panel;
A lamp current generation unit that inputs the panel drive vertical synchronization signal and generates the alternating current in which a current is increased during a predetermined pulse period based on an input timing of the panel drive vertical synchronization signal;
A video signal representing an image to be displayed on the liquid crystal panel, inputs the said panel driving vertical synchronizing signal, wherein the amount is reduced predetermined the input video signal for a predetermined pulse duration, then the reduced liquid crystal projector having a video correcting unit which Ru to display images on the liquid crystal panel shown by the video signal. The liquid crystal projector according to claim 1.
A liquid crystal projector in which the alternating current and the panel drive vertical synchronization signal have the same frequency. The liquid crystal projector according to claim 1.
A liquid crystal projector in which the frequency of the alternating current is an integral multiple of the frequency of the panel drive vertical synchronization signal, and the lamp current generator generates the pulse period for the integral multiple of one period of the panel drive vertical synchronization signal . The liquid crystal projector according to any one of claims 1 to 3,
The liquid crystal panel is a transmissive liquid crystal panel. The liquid crystal projector according to any one of claims 1 to 3,
The liquid crystal panel is a reflection type liquid crystal panel. In a projection image adjustment method for a liquid crystal projector, which includes a light source driven by an alternating current and a liquid crystal panel, and generates projection image light by irradiating the liquid crystal panel with light generated by the light source.
Based on the panel drive vertical synchronization signal that determines the vertical blanking period of the liquid crystal panel, a predetermined pulse period generates the alternating current in which the current is increased,
Wherein the panel driving vertical synchronizing signal the pulse period determined in advance based on reducing the amount predetermined the input video signal, Ru to display the image represented by the video signal obtained by the reduction in the liquid crystal panel Projection image adjustment method for a liquid crystal projector.

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