JP2017173473A - Image projection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image projection device capable of preferably reducing blur on a moving image by suppressing a blurred image, a double image and/or visibility of flicker even when response characteristics of a light modulation element have changed due to circumstance changes and/or aging.SOLUTION: The image projection device includes: light source means; light modulation means that modulates a beam of light from the light source means based on an input image; black insertion drive means that drives the light source means; acquisition means that acquires response characteristics of the light modulation means when a piece of input image data has changed; and black insertion setting means that sets of driving of the black insertion drive means depending on response time acquired by the acquisition means.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image projection apparatus such as a liquid crystal projector, and more particularly to improvement of motion blur.

  Conventionally, a hold-type display device typified by a display device using a light modulation element has a problem called moving image blur where an afterimage is visually recognized when displaying a moving image. As a technique for improving the moving image blur, a technique called black insertion for inserting black in a subframe period is known. The subframe period is a period obtained by dividing one frame period into a plurality of periods. Further, as a method of “inserting black”, a method of displaying black by a light modulation element and a method of turning off the light source based on the scanning start timing of the image are known.

  In relation to the black insertion technique, a technique is known in which the backlight illumination period for illuminating the liquid crystal display panel is determined based on the temperature of the liquid crystal display panel described in Patent Document 1, and the backlight is turned off. .

  Further, a technique is known in which the response start timing and end timing of the panel described in Patent Document 2 are acquired, and the backlight lighting and extinguishing timings are changed based on the acquired timing.

JP 2007-163701 A JP 2012-194530 A

  In order to effectively reduce motion blur due to light source control, it is important to control the turn-off timing and turn-off time of the light source. This is because when the light source extinction timing is not synchronized with the light modulation element scanning timing and the light source extinction timing, a double image is generated. Further, regarding the light source turn-off time, flicker becomes more visible as the turn-off time is longer. In addition, since the response characteristics of the light modulation element change due to temperature changes due to environmental changes and changes over time due to long-term use, it is necessary to control the light source in consideration of these effects.

  However, in the prior art disclosed in Patent Document 1 described above, no consideration is given to changes over time, and the correlation between temperature and backlight lighting timing shifts due to changes over time due to long-term use. For this reason, the liquid crystal display panel and the backlight cannot be synchronized, and a double image is generated.

  Further, in the prior art disclosed in Patent Document 2, the light source extinguishing time increases as the response time of the display panel becomes slow, and flicker visibility is improved.

  Accordingly, an object of the present invention is to reduce blurring of a moving image suitably by suppressing the visibility of a blurred image, a double image, and flicker even when the response characteristic of the light modulation element changes due to environmental changes or changes over time. An object of the present invention is to provide an image projection apparatus capable of performing the above.

In order to achieve the above object, an image display device according to the present invention includes:
A light source unit, a light modulation unit that modulates light from the light source unit based on an input image, a black insertion drive unit that drives the light source unit, and the light modulation unit when input image data changes. It has an acquisition means which acquires a response characteristic, and a black insertion setting means which performs drive setting of the black insertion drive means according to the response time which the acquisition means acquires.

  According to the present invention, even when the response characteristics of the light modulation element change due to environmental changes or changes over time, the visibility of blurred images and double images can be suppressed, and moving image blur can be suitably reduced. An image projection apparatus can be provided.

Block diagram of projector in embodiment 1 Diagram showing black insertion drive Diagram showing the principle of motion blur and the effect of black insertion Diagram showing an example of black insertion failure Flow chart showing control during black insertion drive Flow chart showing a method for obtaining response time of a liquid crystal panel Response time calculation example of LCD panel Flow chart showing how to change black insertion parameters Diagram showing black insertion pattern Flowchart illustrating a black insertion parameter changing method according to the second embodiment. The figure which showed the timing of the black insertion parameter change in Example 2

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  In the following, referring to FIGS. 1 to 9, even if the response characteristics of the light modulation element are changed due to environmental changes or changes with time, according to the first embodiment of the present invention, blur images, double images, flickers, etc. An image projection apparatus capable of suppressing the visibility of the image and reducing the moving image blur appropriately will be described.

  FIG. 1 is a block diagram of a projector 1 which is an image projection apparatus according to an embodiment of the present invention.

  The projector 1 is an image projection apparatus that projects light modulated by the liquid crystal panel 60 according to an input signal onto a projection surface such as a screen as a projection image via a projection lens 90 that is a projection unit. The projector 1 includes a video signal input unit 10, an image processing engine 20, a liquid crystal panel 30, a control microcomputer 40, an operation unit 50, a light source unit 60, a light sensor 70, a memory 80, and a projection lens 90.

  The video signal input unit 10 receives a single or a plurality of video signals.

  The image processing engine 20 is an image processing unit that performs various image processing and synchronization timing change on the input video signal from the video signal input unit 10 and outputs the processed output video signal to the liquid crystal panel 30. The image processing engine 20 can output an internally generated image as an output video signal regardless of the presence or absence of an input signal. The image processing engine 20 includes a synchronization signal acquisition unit 21. The synchronization signal acquisition unit 21 detects the horizontal synchronization signal and the vertical synchronization signal included in the video signal, and acquires the update timing of each frame included in the input video signal.

  The liquid crystal panel 30 aligns the liquid crystal based on the input video signal converted by the image processing engine 20 and forms a light modulation pattern that modulates the light from the light source unit 60.

  The control microcomputer 40 is a control unit configured by a microcomputer so as to control each part of the projector 1 in accordance with an input from the operation unit 50. The control microcomputer 40 includes a light source control unit 41 and a black insertion control unit 42.

  The light source control unit 41 controls the amount of light emitted from the light source unit 60 by power supply control by D / A converter control.

  The black insertion control unit 42 includes a black insertion setting unit 421 and a black insertion driving unit 422, and performs light source control relating to black insertion.

  The black insertion setting unit 421 sets the black insertion timing and the duty ratio at the time of black insertion. The black insertion driving unit 422 performs black insertion according to the setting of the black insertion setting unit 421 while black insertion is being executed. FIG. 2 shows a light source driving state when black insertion start time = 1 ms, black insertion end time = 9 ms, and duty ratio at black insertion = 0%.

  The operation unit 50 includes a switch, a button, a remote control light receiving unit, and the like (not shown) that accept various operations from the user.

  The light source unit 60 includes an LED drive circuit 61 and an LED unit 62, and functions as a light source unit that generates light to be projected based on drive power from the control microcomputer 40.

  The LED drive circuit 61 drives the LED unit 62 based on the supply power supplied from the light source control unit 41 and the drive waveform driven by the black insertion drive unit 422.

  The LED unit 62 includes a plurality of LEDs, and each LED is individually controlled in light quantity based on a drive signal output from the LED drive circuit 61.

  The optical sensor 70 is disposed inside the projector 1 and functions as an optical sensing unit that detects light modulated by the liquid crystal panel 30.

  The memory 80 functions as a storage unit that stores various setting values related to driving of the projector 1.

  The projection lens 90 functions as a projection unit that forms a projection image from the light from the liquid crystal panel 30.

  Next, the operation of black insertion will be described with reference to FIG.

  The horizontal axis of each graph in FIG. 3 indicates time, and the vertical axis indicates the liquid crystal panel reflectivity, light source output rate, light output rate, and output image when black insertion is OFF when a certain pixel changes from black to white. It is the figure compared in the case of black insertion ON.

  The liquid crystal panel reflectivity is a ratio at which the liquid crystal panel 30 reflects the light output from the light source unit 61. The liquid crystal panel has a maximum reflectance when displaying all white and a minimum reflectance when displaying all black. The light source output rate is the ratio of the current light amount to the light amount that can be output by the light source unit 61. The light source output rate is determined based on the power supplied by the light source control unit 41 and the light source drive waveform by the black insertion control unit 42. The light output rate is the ratio of the current light amount to the maximum light amount in the light output from the light source unit 61 modulated by the liquid crystal panel 30. The output image shows the change in the pixel of interest when it is actually projected.

  When the pixel changes from black to white, the rise of the liquid crystal panel 30 requires several ms as shown in the graph of the liquid crystal panel reflectivity. Accordingly, when black insertion is OFF, a blurred image due to the rise of the liquid crystal panel 30 as shown in the output image is generated. When black insertion is ON, the amount of light from the light source is decreased from the start to the end of the rise of the liquid crystal panel 30 and the rise of the liquid crystal panel is hidden to generate a blurred image due to the rise of the liquid crystal panel 30 as shown in the output image Can be prevented.

  Next, an example of black insertion failure will be described with reference to FIG.

  The horizontal axis of each graph in FIG. 4 represents time, and the vertical axis represents the liquid crystal panel reflectivity, light source output rate, light output rate, and output image when a certain pixel changes from black to white. . The difference from the black insertion ON shown in FIG. 3 is that the rise time of the liquid crystal panel reflectivity, the light output rate resulting from it, and the output image are different. It has been confirmed that the rise time of the liquid crystal panel reflectivity changes depending on the temperature of the liquid crystal panel 30 and the usage time.

  In the case of FIG. 4, the rising period of the liquid crystal panel 30 occurs before the light source light quantity reduction period for black insertion. Therefore, as shown in the output image, a blurred image is generated before the start of black insertion. In this case, since a blurred image is generated with the black insertion period in between, a double image is observed by the user.

  The success / failure example of black insertion when the pixel of interest changes from black to white has been described with reference to FIGS. 3 and 4. However, the liquid crystal panel can be used even when the pixel of interest changes from white to black. An equivalent result can be obtained from the relationship of the black insertion period to the fall of 30.

  Next, a black insertion method for suppressing the visibility of a blurred image / double image even when the rising / falling period of the liquid crystal panel 30 changes will be described.

  FIG. 5 is a flowchart showing control during black insertion driving.

  When black insertion is started, the black insertion driving unit 422 drives the light source unit 60 to be black inserted based on the set value of the black insertion setting unit 421.

  In step 101, it is determined whether a predetermined time has elapsed. If it has elapsed, the process proceeds to step 102, and if not, the process proceeds to step 105.

  In step 102, the response time of the liquid crystal panel 30 is acquired. For obtaining the response time of the liquid crystal panel 30, the optical sensor 70 is used to obtain the response start time and the response end time of the liquid crystal panel 30. Here, the response start time refers to the video signal received by the liquid crystal panel 30 from the image processing engine 20 after detecting the vertical synchronization signal included in the video signal input from the video signal input unit 10 to the image processing engine 20. Accordingly, it is the time until the start of light modulation. The response end time corresponds to the video signal received by the liquid crystal panel 30 from the image processing engine 20 after detecting the vertical synchronization signal included in the video signal input from the video signal input unit 10 to the image processing engine 20. This is the time until the light modulation ends.

  The response time acquisition method of the liquid crystal panel 30 performed in step 102 will be described using FIG.

  FIG. 6 is a flowchart showing a response time acquisition method of the liquid crystal panel.

  When response time acquisition of the liquid crystal panel 30 is started, in step 102a, the image processing engine 20 waits until it detects a vertical synchronization signal included in the video signal input from the video signal input unit 10, and the vertical synchronization signal is detected. Then, the process proceeds to step 102b.

  In step 102b, the image processing engine 20 analyzes the input signal and determines whether the response time of the liquid crystal panel 30 can be acquired. Whether or not the response time of the liquid crystal panel 30 can be acquired is determined that the response time can be acquired when the luminance difference between the input current frame and the previous frame exceeds the threshold, and is determined that the response time cannot be acquired if the threshold does not exceed the threshold. . If it is determined that the response time can be acquired, the process proceeds to step 102c. If it is determined that the response time cannot be acquired, the process proceeds to step 102a.

  In step 102 c, the light sensor 70 acquires the amount of light emitted from the light source unit 60 modulated by the liquid crystal panel 30. In the light amount acquisition method, the output of the optical sensor 70 is A / D converted at a specific sampling period, and the time change of the light amount is continuously acquired.

  In step 102d, it is determined whether the image processing engine 20 detects the vertical synchronization signal of the next frame included in the video signal input from the video signal input unit 10. When the vertical synchronization signal of the next frame is not detected, the process proceeds to step 102c and the acquisition of the light amount is continued. When the vertical synchronization signal of the next frame is detected, the process proceeds to step 102e, and the acquisition of the light amount is completed.

  In step 102e, the response start / end time of the liquid crystal panel 30 is determined based on the maximum light amount and the minimum light amount included in the temporal change in the light amount acquired in step 102c. A response time calculation example will be described with reference to FIG. First, the maximum value = max and the minimum value = min of the output values of the plurality of light quantity sensors 70 acquired in step 102c are obtained, and the positions of 10% and 90% when max-min is 100% are calculated. Next, the calculated 10% and 90% positions are connected by a straight line, and the intersection with max and min is calculated. Then, the time located on the front side of the calculated intersection is taken as the response start time, and the time located on the rear side is taken as the response end time.

  Returning to FIG. 5 again, control during black insertion driving will be described.

  In step 103, the response start / end time acquired in step 102 is compared with the black insertion start / end time set in the black insertion setting unit 421, and it is determined whether each difference exceeds a threshold value. If the threshold value is exceeded, the process proceeds to step 104; otherwise, the process proceeds to step 105.

  In step 104, parameters related to black insertion driving set in the black insertion setting unit 421 are changed. The black insertion parameter changing method will be described with reference to FIG.

  When the change of the black insertion parameter is started, in step 104a, the black insertion start time set in the black insertion setting unit 421 is set to the response start time calculated in step 102e.

  In step 104b, the black insertion end time set in the black insertion setting unit 421 is set to the response end time calculated in step 102e.

  In steps 104c to 104e, the black insertion level is set.

  A method for setting the black insertion level will be described with reference to FIG.

  In step 104c, it is determined whether the black insertion time is equal to or less than the threshold A. If it is equal to or less than the threshold A, the process proceeds to step 104e, and if not less than the threshold, the process proceeds to step 104d. The black insertion time is a time during which black insertion, which is derived from “black insertion end time−black insertion start time”, is performed.

  In step 104d, it is determined whether the black insertion time is equal to or less than the threshold value B. If the black insertion time is equal to or less than the threshold value B, the process proceeds to step 104f.

  In step 104e, as shown in pattern 1 in FIG. 9, the light source output rate is set to 0% when the black insertion start time is reached, and the light source output rate is set to 100% when the black insertion end time is reached. By controlling in this way, generation | occurrence | production of the blur image and double image during black insertion is suppressed. However, when such control is performed, flicker is easily visible when the black insertion time is long. Therefore, when the black insertion time is long, the control shown in steps 104f and g is performed.

  In step 104f, as shown in pattern 2 in FIG. 9, the light source output rate is set to a constant value other than 0% when the black insertion start time is reached, and the light source output rate is set to 100% when the black insertion end time is reached. Do. By controlling in this way, a blurred image and a double image are easily visually recognized, but the visibility of flicker can be suppressed even when the black insertion time is long.

  In step 104g, the light source output rate from the black insertion start time to the black insertion end time is changed according to the response state of the liquid crystal panel 30 as in pattern 3 in FIG. By controlling in this way, even when the black insertion time is long, it is possible to suppress the occurrence of a blurred image or a double image during black insertion and to suppress the flicker visibility.

  Returning to FIG. 5 again, control during black insertion driving will be described.

  In step 105, it is determined whether or not black insertion has been completed. If it has not been completed, the process proceeds to step 101. If black insertion has been completed, black insertion is terminated and the light source output rate is driven at 100%.

  In this way, by changing the black insertion driving method according to the response time of the liquid crystal panel 30, even if the response characteristic changes, visibility of a blurred image, a double image, and flicker is suppressed, and a moving image blur is suppressed. Can be suitably reduced.

  Note that the response time acquisition method, measurement timing, black insertion setting parameter, and the like of the liquid crystal panel 30 shown in the present embodiment are merely examples, and the present invention is not limited to this.

  Further, in this embodiment, the response time of the liquid crystal panel 30 is obtained using the optical sensor 70. However, the response time can be appropriately changed, for example, by calculating the response time from the correlation between the temperature and the driving time and the response time of the liquid crystal panel 30. Further, when the response time is calculated from the correlation between the temperature and the driving time and the response time of the liquid crystal panel 30, the correlation set in advance according to the measurement result, the instruction from the user, or the like may be updated.

  In the following, with reference to FIGS. 10 to 11, even if the response characteristics of the light modulation element change due to environmental changes or changes with time, according to the second embodiment of the present invention, a blurred image, double image, flicker, etc. An image projection apparatus capable of suppressing the visibility of the image and reducing the moving image blur appropriately will be described. The second embodiment is different from the first embodiment in that the black insertion control parameter is calculated using the test pattern. In the second embodiment, only differences from the first embodiment will be described. There is no difference between the second embodiment and the first embodiment.

  FIG. 10 is a flowchart illustrating a black insertion parameter changing method according to the second embodiment. FIG. 11 is a diagram illustrating the timing of changing the black insertion parameter in the second embodiment. In the second embodiment, the black insertion parameter change start condition is when the user designates the change of the black insertion parameter by the operation unit 50. Also, it is assumed that the black insertion parameter is not changed during the black insertion drive.

  When the change of the black insertion parameter is started, in step 201, the image processing engine 20 displays the preset test pattern 1 shown in FIG.

  In step 202, the image processing engine 20 displays a preset test pattern 2 shown in FIG.

  In step 203, the light sensor 70 acquires the amount of light emitted from the light source unit 60 modulated by the liquid crystal panel 30. In the light amount acquisition method, the output of the optical sensor 70 is A / D converted at a specific sampling period, and the time change of the light amount is continuously acquired.

  In step 204, it is determined whether the display time of the test pattern 2 has passed one frame. If not, the process proceeds to step 203. If it has elapsed, the light quantity acquisition 1 in step 203 is terminated, and the process proceeds to step 204. To do.

  In step 205, the image processing engine 20 displays a preset test pattern 3 shown in FIG.

  In step 206, as in step 203, the light sensor 70 continues to acquire the amount of light emitted from the light source unit 60 modulated by the liquid crystal panel 30.

  In step 207, it is determined whether the display time of the test pattern 3 has passed one frame. If not, the process proceeds to step 206. If it has elapsed, the light quantity acquisition 2 in step 206 is terminated, and the process proceeds to step 208. To do.

  In step 208, the response start / end time of the liquid crystal panel 30 based on the maximum light amount and the minimum light amount included in the temporal change in the light amount acquired in steps 203 and 206 in the same procedure as the method performed in step 102e of the first embodiment. To decide.

  In step 209, the response start times in step 203 and step 206 are compared, and the earlier one is set as the response start time.

  In step 210, the response end times of step 203 and step 206 are compared, and the later one is set as the response end time.

  In step 211, it is determined whether the black insertion time is equal to or less than the threshold value A. If the black insertion time is equal to or less than the threshold value A, the process proceeds to step 213. The black insertion time is a time during which black insertion, which is derived from “black insertion end time−black insertion start time”, is performed.

  In step 212, it is determined whether the black insertion time is equal to or less than the threshold value B. If the black insertion time is equal to or less than the threshold value B, the process proceeds to step 214.

  In step 213, the light source output rate is set to 0% when the black insertion start time is reached, and the light source output rate is set to 100% when the black insertion end time is reached. By controlling in this way, generation | occurrence | production of the blur image and double image during black insertion is suppressed. However, when such control is performed, flicker is easily visible when the black insertion time is long. Therefore, when the black insertion time is long, the control shown in steps 214 and 215 is performed.

  In step 214, the light source output rate is set to a constant value other than 0% when the black insertion start time is reached, and the light source output rate is set to 100% when the black insertion end time is reached. By controlling in this way, a blurred image and a double image are easily visually recognized, but the visibility of flicker can be suppressed even when the black insertion time is long.

  In step 215, the light source output rate from the black insertion start time to the black insertion end time is changed according to the response state of the liquid crystal panel 30 acquired in steps 203 and 206. By controlling in this way, even when the black insertion time is long, it is possible to suppress the occurrence of a blurred image or a double image during black insertion and to suppress the flicker visibility.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

1 projector, 10 video signal input unit, 20 image processing engine,
21 synchronization signal acquisition unit, 30 liquid crystal panel, 40 control microcomputer, 41 light source control unit,
42 black insertion control unit, 421 black insertion setting unit, 422 black insertion drive unit, 50 operation unit,
60 light source unit, 61 LED drive circuit, 62 LED unit, 70 light sensor,
80 memories, 90 projection lenses

Claims (16)

Light source means;
Light modulating means for modulating light from the light source means based on an input image;
Black insertion driving means for driving the light source means;
An acquisition means for acquiring response characteristics of the light modulation means when the input image data changes;
Black insertion setting means for performing drive setting of the black insertion driving means according to the response time acquired by the acquisition means;
An image display device comprising: The image display apparatus according to claim 1, wherein the acquisition unit includes a light amount measurement unit, and acquires a response start time and an end time of the light modulation unit using the light amount measurement unit. The black insertion setting unit sets the black insertion start time of the black insertion driving unit based on the response start time of the light modulation element acquired by the acquisition unit. Image display device. 4. The black insertion setting unit sets the black insertion end time of the black insertion driving unit based on the response end time of the light modulation element acquired by the acquisition unit. The image display device according to claim 1. The said acquisition means has a temperature measurement means, The black insertion start time or the end time of the said black insertion drive means is set based on the temperature which the said black insertion setting means acquired. 5. The image display device according to any one of 4. The image display apparatus according to claim 1, wherein the temperature measurement unit measures a temperature of the light modulation element. The acquisition means includes drive time measurement means, and sets the black insertion start time or end time of the black insertion drive means based on the drive time acquired by the black insertion setting means. The image display device according to claim 6. 8. The image display device according to claim 1, wherein the black insertion start time or end time is determined based on a vertical synchronization signal. 9. When the time from the response start time to the response end time of the light modulation element acquired by the acquisition unit is equal to or less than a threshold value, the black insertion setting unit has the light source between the black insertion start time and the black insertion end time. 9. The image display apparatus according to claim 1, wherein the black insertion driving unit is set so that the lighting state of the unit is turned off. When the time from the response start time to the response end time of the light modulation element acquired by the acquisition unit is equal to or greater than a threshold, the black insertion setting unit is configured to output the light source between the black insertion start time and the black insertion end time. 10. The image display device according to claim 1, wherein the black insertion driving unit is set so that a lighting state of the unit includes a state other than a light-off state. The image display device according to claim 10, wherein the state other than the light-off state is a second light source state that is darker than the first light source state where black insertion is not performed. The image display apparatus according to claim 10, wherein states other than the extinguished state are driven with a predetermined black insertion waveform pattern based on a result of the acquisition unit. 13. The image display device according to claim 12, wherein the black insertion waveform pattern is a waveform pattern having an inverse correlation with a response curve of a light modulation element. 14. The apparatus according to claim 1, further comprising a black insertion setting update unit configured to update a correlation between an acquisition result of the acquisition unit and a setting value set by the black insertion setting unit. Image display device. The black insertion setting means has a black insertion luminance threshold value indicating a ratio of the brightness of the display image at the time of black insertion to the brightness of the display image at the time of non-black insertion, and the ratio of the brightness at the time of black insertion is the black The image display apparatus according to claim 1, wherein the black insertion setting unit is set so as to be equal to or higher than an insertion luminance threshold value. The image display apparatus according to claim 1, wherein the black insertion luminance threshold value can be changed.