JP6311823B2 - Image display device and image display method - Google Patents

Description

  The present invention relates to an image display device and an image display method.

  A laser scan type image display device that projects and displays an image by reflecting and scanning laser light is known (for example, Patent Document 1). Laser scan type image display devices are used as HUDs (Head Up Displays), projectors, and the like that project and display images on windshields and combiners of automobiles. In a laser scan type image display apparatus, laser light is reflected by a mirror of an optical scanner and the direction of the mirror is changed in a horizontal direction and a vertical direction to scan the laser light.

  The emission intensity of the laser light when a constant current is passed through the laser diode changes based on the surrounding temperature change. Moreover, in HUD, in order to improve the visibility of the displayed image, the brightness of the image is changed in accordance with the presence / absence of a forward vehicle, changes in daylight and nightlight, and the like. As described above, in the image display apparatus, the output of the light source may be changed in order to change the brightness of the displayed image.

JP 2013-156314 A

  If a change that can be discriminated by the user occurs in the brightness or color tone of the image during image display, the user may feel uncomfortable. In the image display device described in Patent Document 1, the output of the laser light is adjusted after the laser beam is not emitted to the outside of the image display device by a driving mirror. For this reason, the brightness can be adjusted without displaying an image. However, when laser light output adjustment is performed in stages, an image displayed during the adjustment period may have an unnatural color.

  Such laser light output adjustment is often required when the ambient temperature of the image display device is low. In particular, when three-color laser diodes such as RGB are used as the light source, the temperature characteristics of the laser diodes are different, so that during the stepwise adjustment, the color tone differs from the desired color tone. There is also.

  The present invention has been made to solve such problems, and even when adjusting the output of laser light, the user feels unnaturalness with respect to the brightness or color tone of the displayed image. It is an object of the present invention to provide an image display device and an image display method that make it possible to perform output adjustment that does not occur.

  The image display device (100) of the present invention includes a light source unit (11) that outputs light, a detection unit (13) that detects the intensity of the light, and the light for displaying an image composed of a plurality of frames. An optical scanner (12) that scans the light, an adjustment unit (74) that adjusts the output of the light source unit so that the detection value of the detection unit becomes a target value, and light corresponding to the image data that constitutes the image A light source drive unit (73) for driving the light source unit based on the adjustment result of the adjustment unit to output the light source, and the adjustment unit sets the detection value of the detection unit to a target value. When adjusting the output of a part, in the adjustment during the period in which the frame constituting the image is a black frame, the change of the output to the target value is sharply performed as compared with the adjustment during the period not being a black frame It is characterized by that.

  The image display method of the present invention is an image display method in an image display device that drives a light source unit according to image data composed of a plurality of frames to output light and displays the image by scanning the light. Then, when adjusting the output of the light source unit so that the detected value of the light intensity becomes a target value, the adjustment during the period in which the frame constituting the image is a black frame is performed during the period that is not a black frame. Compared with the adjustment, the change in output up to the target value is performed sharply.

  According to the present invention, it is possible to provide an image display device and an image display method that enable a user to perform output adjustment so as not to feel unnaturalness with respect to the brightness or tone of an image to be displayed. it can.

1 is a diagram illustrating a configuration of an image display device according to a first embodiment. FIG. 3 is a diagram illustrating a configuration of a light emitting unit according to the first embodiment. 3 is a diagram showing a scan area of the image display device according to Embodiment 1. FIG. FIG. 3 is a block diagram showing processing in a control unit according to Embodiment 1. FIG. 6 is a diagram illustrating an APC operation in the image display apparatus according to the first embodiment. 6 is a flowchart showing an image display method in the image display apparatus according to Embodiment 1. FIG. 6 is a diagram illustrating a comparative example of the operation of APC in the image display apparatus according to Embodiment 1. FIG. FIG. 10 is a block diagram showing processing of a control unit in a modification of the image display device according to Embodiment 1.

[Embodiment 1]
Embodiments of an image display apparatus according to the present invention will be described below with reference to the drawings.
First, the configuration of the image display apparatus 100 according to the present embodiment will be described with reference to FIG. The image display device 100 includes a light emitting unit 1, a first plane mirror 2, a screen 3, a second plane mirror 4, a concave mirror 5, a projection unit 6, a control unit 7, a housing 8, Have

  With reference to FIG. 1, the optical path until the light beam L1 emitted from the light emitting unit 1 reaches the eyes of the user U will be described. The light beam L <b> 1 emitted from the light emitting unit 1 is reflected by the first flat mirror 2 to bend the optical path and enter the screen 3. The light beam L1 forms an intermediate image of the display image on the screen 3. The screen 3 is of a light transmission type. For example, a diffusion plate or a microlens array is used as the screen 3. The microlens array is an array of microlenses arranged in a matrix. The microlens array has an effect of reducing speckles of laser light, and is designed so that the emission angle and color unevenness are optimized.

  The light beam L <b> 1 emitted from the screen 3 is reflected by the second plane mirror 4, so that the optical path is bent and enters the concave mirror 5. The light beam L <b> 1 reflected by the concave mirror 5 is emitted outside the housing 8 and enters the projection unit 6. The projection unit 6 reflects a part of the incident light beam and transmits the rest. The projection unit 6 can use a combiner or a car windshield.

  In the image display device 100, the light beam L <b> 1 emitted from the opening of the housing 8 and reflected by the projection unit 6 and the light beam L <b> 2 transmitted through the projection unit 6 are overlapped by the projection unit 6 toward the user U. When viewed from the user U, the image displayed by the image display device 100 appears as a virtual image superimposed on the scenery over the projection unit 6.

  The structure of the light emission unit 1 of this Embodiment is demonstrated using FIG. As shown in FIG. 2, the light emitting unit 1 includes a laser diode 11, a scanning mirror 12, a photodiode 13, and a light shielding unit 14.

  The laser diode 11 outputs laser light according to the input current. The laser diode 11 is a light source unit that outputs light. As the laser diode 11, for example, a semiconductor laser is used. The laser diode 11 has three types of laser diodes R, G, and B, and can output R, G, and B laser beams. Of course, the laser diode 11 may output laser light of a color other than R, G, and B.

  The light beam L1 emitted from the laser diode 11 enters the scanning mirror 12. The scanning mirror 12 swings to scan the light beam L1 by changing the reflection direction of the light beam L1 output from the laser diode 11. As the scanning mirror 12, for example, a MEMS (Micro Electro Mechanical Systems) mirror is used. The scanning mirror 12 is an optical scanner that scans light.

  The scanning mirror 12 reflects a part of the incident light beam and transmits the rest. For example, the scanning mirror 12 reflects about 98% of incident light and transmits the remaining about 2%. A part of the light beam L 1 incident on the scanning mirror 12 is transmitted to become a light beam L 3, and the rest is reflected by the scanning mirror 12 and emitted to the outside of the light emitting unit 1. A light blocking portion 14 is provided between the time when the light beam L1 is reflected by the scanning mirror 12 and the time when the light beam L1 exits the light emitting unit 1. The light beam blocked by the light shielding unit 14 does not go out of the light emitting unit 1.

  The photodiode 13 detects the intensity of the laser beam (light beam L3) output from the laser diode 11 and transmitted through the scanning mirror 12. The photodiode 13 functions as a detection unit that detects the intensity of light from the light source.

  As shown in FIG. 3, the scan area 30 in which light is scanned by the scanning mirror 12 has a rectangular shape. The scan area 30 has a drawing area 31 in which an image is displayed and a blanking area 32 in which no image is displayed. In FIG. 3, the laser beam is scanned in the direction indicated by the arrow. In the region indicated by the two-dot chain line in the arrow, the laser diode 11 emits light based on the image data, and the user can visually recognize the image in the drawing area 31. In FIG. 3, the drawing area 31 has a rectangular shape. The blanking area 32 has a frame shape so as to surround the drawing area 31.

  In the blanking area 32, an adjustment area 33 for adjusting the output of the laser diode 11 is provided. Here, the adjustment area 33 is provided on the upper end side of the blanking area 32. In the drawing area 31, the laser diode 11 blinks based on the image data for each frame. In the blanking area 32, the laser diode 11 is not caused to emit light, but in the adjustment area 33, the laser diode 11 is caused to emit light. The light shielding unit 14 illustrated in FIG. 2 is provided so as to shield the light beam corresponding to the adjustment area 33. In the adjustment area 33, the light from the laser diode 11 is shielded by the light shielding portion 14, and thus the image is not visually recognized by the user.

  The image display apparatus 100 has an APC (Auto Power Control) function that adjusts the current input to the laser diode 11 so that the detection value of the photodiode 13 is constant.

  The processing in the control unit 7 when the image display apparatus 100 performs APC will be described with reference to FIG. The control unit 7 includes a frame buffer 71, a black frame detection unit 72, a light source drive unit 73, and an adjustment unit 74. The control unit 7 may be realized by hardware such as an FPGA (Field Programmable Gate Array), or may be realized by a program stored in an external storage device and a CPU (Central Processing Unit).

  Image data to be displayed is input to the control unit 7 from the outside and sent to the frame buffer 71 and the black frame detection unit 72. The image data includes RGB data of an image to be displayed. The frame buffer 71 is a storage device that temporarily stores image data, accumulates image data for several frames, and then sends the image data for each frame to the light source driving unit 73. As the frame buffer 71, for example, a DDR (Double Data Rate) memory is used, and DDR2, DDR3, or other SDRAM (Synchronous Dynamic Random Access Memory) may be used. In addition, the frame buffer 71 sends a frame synchronization signal to the adjustment unit 74 as one frame of image data is input.

  The black frame detection unit 72 detects a black frame in which all RGB data constituting one frame is zero from the input image data. When a predetermined number of black frames, for example, several tens of frames are continued, the black frame detection unit 72 sends a data 0 detection signal to the adjustment unit 74.

  The adjustment unit 74 adjusts the output of the laser diode 11 so that the detection value of the photodiode 13 becomes a target value. A data 0 detection signal is input from the black frame detection unit 72 and a frame synchronization signal is input from the frame buffer 71 to the adjustment unit 74. Based on these two signals, the adjustment unit 74 sends the RGB power setting signal to the light source driving unit 73. And send. The RGB power setting signal is a signal for setting the amount of current input to the laser diode 11.

  Based on the laser light irradiated to the adjustment area 33 in the blanking area 32 shown in FIG. 3, the adjustment unit 74 adjusts the output of the laser diode 11 by changing the amount of current input to the laser diode 11. To do.

  The light source drive unit 73 drives the laser diode 11 based on the adjustment result of the adjustment unit 74 in order to output light according to the image data. Thereby, in the drawing area 31, the laser diode 11 emits light with the light intensity that appropriately displays the RGB data in the image data. Further, the light source driving unit 73 causes the laser diode 11 so that the detection value of the photodiode 13 becomes the target value during the black frame period when the black frame detection unit 72 detects a continuous section of the black frame. To emit light.

  The light output from the laser diode 11 is incident on the detection surface of the photodiode 13, and the photodiode 13 detects the intensity of the light incident on the detection surface. The intensity of the light detected by the photodiode 13 is sent to the adjustment unit 74 as a laser emission level signal.

  The APC operation of the image display apparatus 100 will be described with reference to FIGS. As shown in FIG. 5, image data for each frame is sent to the frame buffer 71, and the image data is displayed in order from the left side in the figure. That is, Dm to Dn each represent one frame, and the frames are displayed in the order of Dm, Dm + 1,..., Dn−1, Dn.

  One frame of image data includes a drawing section T1 in which an image is displayed and a blanking section T2 in which no image is displayed. The drawing section T1 corresponds to the drawing area 31 and the blanking section T2 corresponds to the blanking area 32. The drawing interval T1 and the blanking interval T2 are alternately repeated.

  The drawing section T1 includes a black frame that does not display an image and a non-black frame that displays an image. In the black frame, the RGB data in the image data are all zero, and the laser diode 11 is not emitted in the drawing area 31, so that no image is displayed. That is, the black frame does not output laser light in both the drawing section T1 and the blanking section T2. In the non-black frame, the light source driving unit 73 causes the laser diode 11 to emit light according to the RGB data in the image data, whereby an image is displayed in the drawing area 31.

  FIG. 5 shows data before passing through the frame buffer 71 and data after passing through, and a delay of 5 frames is caused by passing through the frame buffer 71. A frame synchronization signal is sent from the frame buffer 71 to the adjustment unit 74 in accordance with the image data sent for each frame. The H level of the frame synchronization signal corresponds to the drawing interval T1, and the L level corresponds to the blanking interval T2.

  The adjustment unit 74 adjusts the output of the laser diode 11 in a section corresponding to the adjustment area 33 in the blanking section T2. There are two kinds of methods for adjusting the output of the laser diode 11, which are switched depending on the presence or absence of the data 0 detection signal sent from the black frame detection unit 72 to the adjustment unit 74.

  In FIG. 5, when a predetermined number of black frames are continuous in the data before passing through the frame buffer, the black frame detection unit 72 determines that the black frames are continuous. Here, Dm to Dm + 4 are black frames, and five black frames are continuous. Thereafter, the black frame detection unit 72 sends a data 0 detection signal to the adjustment unit 74 at a timing when the head Dm of the black frame appears as the data after passing through the frame buffer.

  When the data 0 detection signal is not received, the adjustment unit 74 adjusts the current value input to the laser diode 11 so that the detection value of the photodiode 13 becomes the set value in the blanking interval T2. The set value is determined such that the detection value of the photodiode 13 increases or decreases by a certain amount from the current value. In this case, the current value input to the laser diode 11 changes step by step by a certain amount every time the blanking interval T2 comes.

  On the other hand, when receiving the data 0 detection signal, the adjustment unit 74 at a stroke sets the current value input to the laser diode 11 so that the detection value of the photodiode 13 becomes the target value regardless of the setting value of the previous frame. adjust. The target value is determined in advance, and a plurality of target values may be determined in accordance with the presence / absence of a preceding vehicle and changes in daylight and night light.

  Then, the light source driving unit 73 reads the current of the laser diode 11 when the detection value of the photodiode 13 is the target value. Thereby, the light quantity change of the laser diode 11 by the temperature change can be read. The adjustment unit 74 generates a power setting signal according to the light amount change.

  For example, when the current value of the laser diode 11 when the detection value of the photodiode 13 is the target value is higher than the reference, the laser diode 11 needs a higher current. Conversely, when the current value of the laser diode 11 when the detection value of the photodiode 13 is the target value is lower than the reference, a high current is not required for the laser diode 11. Therefore, even when the RGB data is the same, if the power setting signal is different, the current supplied from the light source driving unit 73 to the laser diode 11 changes.

  In order to explain more specifically, let us consider a case where the RGB data has a constant value in the entire drawing area 31. When displaying with the light quantity corresponding to RGB data, let the reference current which flows into the laser diode 11 be Id. When the current value of the laser diode 11 when the detection value of the photodiode 13 is the target value is higher than the reference, a current higher than the reference current Id is supplied to the laser diode 11 in the drawing area 31. On the other hand, when the current value of the laser diode 11 when the detection value of the photodiode 13 is the target value is lower than the reference, a current lower than the reference current Id is supplied to the laser diode 11 in the drawing area 31.

  In this way, the light source driving unit 73 supplies a current to the laser diode 11 so that the amount of light corresponding to certain RGB data is constant between frames. That is, when the RGB data has the same value, the adjustment unit 74 sets the power setting signal so that the light emission amounts of the laser diodes 11 are equal. Then, the light source driving unit 73 supplies current to the laser diode 11 so that the laser diode 11 emits light with a light amount corresponding to the RGB data in accordance with the power setting signal. Thereby, the fluctuation | variation of the emitted light amount of the laser diode 11 by a temperature change can be reduced.

  An image display method in the image display apparatus 100 will be described with reference to FIG. First, the black frame detection unit 72 detects whether or not a predetermined number of black frames continue after the frame being displayed (ST601). When the predetermined number of black frames are not continuous (NO in ST601), the current value input to the laser diode 11 is changed in the adjustment area 33 so that the detection value of the photodiode 13 becomes the set value (ST604). . Thereafter, the light source driving unit 73 causes the laser diode 11 to emit light with the current value changed to the set value, and displays an image of the next frame (ST605).

  When a predetermined number of black frames continue (YES in ST601), the adjustment unit 74 adjusts the current value input to the laser diode 11 so that the detection value of the photodiode 13 becomes the target value in the adjustment area 33. (ST602). The adjustment unit 74 sends a power setting signal to the light source drive unit 73 in order to instruct to drive the laser diode 11 with the adjusted current value (ST603). Thereafter, the light source driver 73 causes the laser diode 11 to emit light with the adjusted current value, and displays an image after the black frame (ST605). After the image after the black frame is displayed, it is detected whether or not a predetermined number of black frames continue for the next frame (ST601). If adjustment of the current value input to the laser diode 11 is not necessary, no adjustment is required regardless of the determination in step ST601.

  The image display apparatus 100 according to the present embodiment changes the output of the laser diode 11 at once to the target value when the black frames are continuous. Thereby, the target output of the laser diode 11 can be obtained more quickly than when the output of the laser diode 11 is changed stepwise.

  Further, at the timing when the black frames continue, the output of the laser diode 11 is adjusted so that the detection value of the photodiode 13 becomes the target value, and the power setting signal is generated. In this way, even if the power setting signal changes greatly, the influence on the image displayed in the drawing area 31 can be reduced.

  For example, when non-black frames are continuously displayed, if the power setting signal changes greatly, the color development changes greatly in two consecutive frames. In two consecutive frames, since the frame images in the drawing area are similar, it is easy for the user to recognize that the coloring has changed. On the other hand, in the present embodiment, since the black frames are continuous, the color development in the drawing area does not change significantly. Therefore, it is possible to realize a display in which the user is hardly aware of the color change.

  As described above, according to the present embodiment, it is possible to provide an image display apparatus that has a simple configuration and is less likely to be recognized by the user that the brightness of the image has been changed.

(Comparative example)
A comparative example of the APC operation of the image display apparatus 100 will be described with reference to FIG. In FIG. 5, when the black frame detecting unit 72 detects a predetermined number of black frames, the output of the laser diode 11 is changed to the target value all at once. On the other hand, in FIG. 7, the output of the laser diode 11 is changed stepwise in the blanking interval T2 regardless of whether or not the next display is a black frame. That is, in the blanking interval T2, the output of the laser diode 11 is changed to a set value that is a predetermined amount away from the current value. Then, the blanking interval T2 is repeated a plurality of times, and when the detection value of the photodiode 13 reaches the target value, the APC operation is terminated. Therefore, it takes a long time to adjust the output of the laser diode 11.

(Modification)
As illustrated in FIG. 8, the image display apparatus 100 may include a black frame generation unit 75 that generates a black frame instead of the black frame detection unit 72. When the black frame generation unit 75 generates a black frame, the black frame generation unit 75 sends black frame image data to the frame buffer 71 and sends a data 0 generation signal to the adjustment unit 74. Receiving the data 0 generation signal, the adjustment unit 74 sends a power setting signal to the light source driving unit 73, and the light source driving unit 73 causes the laser diode 11 to emit light so that the detection value of the photodiode 13 becomes the target value.

  The image display apparatus 100 according to the modification can generate a black frame at an arbitrary timing by the black frame generation unit 75, so that even when a non-black frame image continues, the laser can be generated at an arbitrary timing. The output of the diode 11 can be adjusted. For example, the black frame generation unit 75 may generate a black frame when the image display apparatus 100 is activated or in sleep mode.

  Note that the present invention is not limited to the above-described embodiment, and can be changed as appropriate without departing from the spirit of the present invention. For example, the optical scanner is not limited to a scanning mirror such as a MEMS mirror or a galvanometer mirror, and may be an optical scanner using an electro-optic effect.

DESCRIPTION OF SYMBOLS 1 Light emission unit 7 Control unit 11 Laser diode 12 Scanning mirror 13 Photodiode 14 Light-shielding part 30 Scan area 31 Drawing area 32 Blanking area 33 Adjustment area 71 Frame buffer 72 Black frame detection part 73 Light source drive part 74 Adjustment part 75 Black frame Generation unit 100 Image display device

Claims (6)

A light source unit that outputs light;
A detector for detecting the intensity of the light;
An optical scanner that scans the light to display an image composed of a plurality of frames;
An adjustment unit for adjusting the output of the light source unit so that the detection value of the detection unit becomes a target value;
A light source drive unit that drives the light source unit based on an adjustment result of the adjustment unit to output light according to image data constituting the image,
When adjusting the output of the light source unit so that the detection value of the detection unit becomes a target value, the adjustment unit is not a black frame in adjustment during a period in which the frame constituting the image is a black frame An image display device characterized by steeply changing the output up to the target value as compared with the adjustment during the period. The image display device according to claim 1,
The adjustment unit adjusts the output of the light source unit so that the detection value of the detection unit becomes a target value. In the adjustment during the period in which the frame constituting the image is a black frame, The image display apparatus is characterized in that the output is changed at a timing from the non-black frame to the appearance of the first frame in the period of the black frame. The image display device according to claim 1 or 2,
The scan area where light is scanned by the optical scanner has a drawing area where an image is displayed and a blanking area where an image is not displayed,
The image display apparatus, wherein the detection unit detects the intensity of light output to an adjustment area in the blanking area. The image display device according to any one of claims 1 to 3,
A black frame detection unit for detecting the black frame;
When the black frame detection unit detects that the black frames are continuous, the adjustment unit is configured so that the detection value of the detection unit becomes the target value during a continuous black frame period. An image display device characterized by adjusting an output. The image display device according to any one of claims 1 to 3,
It has a black frame generator that generates black frames,
The adjustment unit adjusts an output of the light source unit so that a detection value of the detection unit becomes the target value during a black frame period generated by the black frame generation unit. apparatus. An image display method in an image display device for driving a light source unit according to image data composed of a plurality of frames to output light, and displaying the image by scanning the light,
When adjusting the output of the light source unit so that the detected value of the light intensity becomes a target value, in the adjustment during the period in which the frame constituting the image is a black frame, the adjustment during the period that is not a black frame An image display method characterized by sharply changing the output up to the target value as compared with the above.