JP2017102136A - Light source driving device and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image display device capable of suppressing colour shift even when a low-brightness image is displayed.SOLUTION: A light source 51 comprising a semiconductor laser emits a laser beam. A drive part 40 drives the light source 51. When a pixel value in a predetermined pixel position is a first pixel value expressed by a laser output power equal to or less than a threshold, a pixel value substitution part 210 substitutes a pixel value in the predetermined pixel position in any frame of the plurality of frames with a second pixel value expressed by a laser output power exceeding the threshold so that an average pixel value obtained by averaging the pixel values in the predetermined pixel position by a plurality of frames is the first pixel value, and substitutes pixel values in the predetermined pixel position in the other frames of the plurality of frames with zero. The control part 200 controls the drive part 40 to drive the light source 51 based on an image signal with the pixel value substituted by the pixel value substitution part 210.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a light source driving device for driving a semiconductor laser and an image display device using an optical deflector.

  In recent years, optical deflectors using MEMS (Micro Electro Mechanical System) technology have been developed. The optical deflector is used as a display device for displaying an image. The mirror of the optical deflector is irradiated with laser light emitted from the semiconductor laser, and the mirror is deflected two-dimensionally. Accordingly, the optical deflector can cause the laser beam to scan in the horizontal direction and the vertical direction and display an image on the screen.

  As described in Patent Document 1, an optical deflector may be used for a head-up display for a vehicle, for example. The head-up display is an example of an image display device.

JP 2013-130832 A

  There is a relationship called IL characteristics between the drive current value for driving the semiconductor laser and the laser output power of the laser light emitted from the semiconductor laser. When the drive current value is equal to or greater than a predetermined threshold, the semiconductor laser emits laser light. According to the IL characteristic, the laser output power increases almost linearly when the drive current value is increased.

  For example, at night, it may be required to reduce the brightness of an image displayed by the image display device. In order to display a low-brightness image, the laser output power may be reduced by reducing the drive current value.

  However, there is a kink region where the laser output power does not increase linearly in the region where the drive current value near the threshold is small. Accordingly, if the drive current value is reduced in order to reduce the laser output power, laser light is emitted with the laser output power based on the drive current value in the kink region.

  The IL characteristics of the respective semiconductor lasers emitting red (R) light, green (G) light, and blue (B) light are different from each other. Therefore, when each of the R, G, and B laser beams is generated with the laser output power based on the drive current value in the kink region, a color shift different from the originally intended color occurs.

  In view of such problems, an object of the present invention is to provide a light source driving device and an image display device that can suppress the occurrence of color misregistration even when a low-luminance image is displayed.

  In order to solve the above-described problems of the prior art, the present invention provides a light source composed of a semiconductor laser that emits laser light, and a drive signal that increases or decreases the drive current value of the light source according to each pixel value in an image signal. When a pixel value at a predetermined pixel position of a plurality of consecutive frames in the image signal includes a first pixel value expressed by a laser output power that is equal to or lower than a threshold that is a predetermined laser output power, The pixel value at the predetermined pixel position in any one of the plurality of frames is set to the threshold value so that an average pixel value when the pixel values at the predetermined pixel position are averaged over the plurality of frames becomes the first pixel value. Is replaced with a second pixel value expressed by a laser output power exceeding the predetermined pixel position in the other frames of the plurality of frames. A pixel value replacement unit that replaces the pixel value at 0 with the pixel value, and controls the drive unit to drive the light source based on an image signal in a state where the pixel value at the predetermined pixel position is replaced by the pixel value replacement unit A light source driving device is provided.

  In order to solve the above-described problems of the prior art, the present invention provides the above-described light source driving device and an optical deflector that displays an image by deflecting the laser light emitted from the light source in the horizontal direction and the vertical direction. An image display device is provided.

  According to the light source driving device and the image display device of the present invention, it is possible to suppress the occurrence of color misregistration even when displaying a low-luminance image.

It is a block diagram which shows the light source drive device and image display apparatus of 1st Embodiment. It is a perspective view which shows schematic structure of the image display apparatus using a laser light source and an optical deflector. It is a figure which shows an example of the IL characteristic which a semiconductor laser has. It is a figure which compares and shows the drive method of the normal semiconductor laser, and the drive method of the semiconductor laser in the image display apparatus of 1st Embodiment. It is a figure which compares and shows the normal image display method and the image display method in the image display apparatus of 1st Embodiment. It is a figure which compares and shows the pixel value represented by 1 pixel of each of the normal image display method and the image display method in the image display apparatus of 1st Embodiment. It is a block diagram which shows the light source drive device and image display apparatus of 2nd Embodiment. It is a figure which shows the 1st example which compares the normal image display method and the image display method in the image display apparatus of 2nd Embodiment. It is a figure which shows the 2nd example which compares the normal image display method and the image display method in the image display apparatus of 2nd Embodiment. It is the figure which put together the method of replacement of the pixel value in the image display apparatus of 2nd Embodiment in the table form. It is a block diagram which shows the light source drive device and image display apparatus of 3rd Embodiment. It is a figure which shows an example which compares the normal image display method and the image display method in the image display apparatus of 3rd Embodiment. In order to compare the average value of the pixel values of the odd and even frames by the normal image display method and the average value of the pixel values of the odd and even frames by the image display method in the image display device of the third embodiment. FIG. It is the figure which put together the method of the replacement of the pixel value in the image display apparatus of 3rd Embodiment in the table form.

  Hereinafter, the light source driving device and the image display device of the first and second embodiments will be described with reference to the accompanying drawings. As shown in FIG. 2, the image display devices of the first and second embodiments are roughly configured by deflecting the laser light in a horizontal direction and a vertical direction, and a laser light generation unit 50 that emits laser light. And an optical deflector 100 for displaying an image on the screen 60.

<First Embodiment>
The detailed configuration and operation of the light source driving device and the image display device of the first embodiment will be described with reference to FIG. In FIG. 1, an optical deflector 100 includes a horizontal deflection element (not shown) for deflecting laser light in the horizontal direction and a vertical deflection element (not shown) for deflecting laser light in the vertical direction. It has a structured.

  The optical deflector 100 includes a mirror 12, a horizontal drive unit 11H, a vertical drive unit 11V, and a drive detection unit 13.

  An image signal indicating an image to be displayed on the image display device is input to the control unit 200. The image displayed on the image display device is an image with relatively little movement. The image signal is configured such that a plurality of the same frames are continued. The plurality of frames are preferably even numbers, but may be odd numbers. The control unit 200 includes a pixel value replacement unit 210 described later.

  Based on the horizontal synchronization signal of the input image signal, the control unit 200 generates a horizontal drive signal for swinging the optical deflector 100 in the horizontal direction and supplies it to the horizontal drive unit 11H.

  The control unit 200 generates a vertical drive signal for swinging the optical deflector 100 in the vertical direction based on the vertical synchronization signal of the input image signal, and supplies the vertical drive signal to the vertical drive unit 11V. A drive detection signal generated by detecting the swing of the horizontal deflection element by the drive detection unit 13 is input to the control unit 200.

  The drive unit 40 includes an R light source drive unit 40r, a G light source drive unit 40g, and a B light source drive unit 40b. The R light source drive unit 40r, the G light source drive unit 40g, and the B light source drive unit 40b drive the laser light generation unit 50 based on the control by the control unit 200.

  The laser beam generator 50 includes a light source 51, prisms 52 to 54, a mirror 55, and a lens 56. The light source 51 includes an R light source 51r that emits an R laser beam, a G light source 51g that emits a G laser beam, and a B light source 51b that emits a B laser beam.

  The R light source driving unit 40r drives the R light source 51r, the G light source driving unit 40g drives the G light source 51g, and the B light source driving unit 40b drives the B light source 51b. The drive unit 40 supplies a drive signal whose pulse width is constant and whose drive current value increases or decreases according to the luminance value of the image to be displayed, specifically, the pixel value of each pixel constituting the image. Each of the light source 51r, the G light source 51g, and the B light source 51b is driven.

  The control unit 200 controls the drive unit 40 to supply a drive signal having a drive current value corresponding to each pixel value to the light source 51.

  The prism 52 bends the optical path of the R laser beam emitted from the R light source 51r by 90 degrees. The prism 53 combines the R laser beam and the G laser beam. The prism 54 combines the combined light of the R laser light and the G laser light and the B laser light.

  The control unit 200 controls the drive unit 40 so that the combined light corresponding to the input image signal is output from the prism 54. The mirror 55 reflects the combined light of the R, G, and B laser beams output from the prism 54. The lens 56 collects the combined light from the mirror 55 and makes it incident on the mirror 12.

  The drive unit 40, the laser light generation unit 50, and the control unit 200 in FIG. 1 constitute the light source drive device 260 of the first embodiment.

  The mirror 12 is oscillated so that the laser beam is scanned in the horizontal direction of the screen 60 by the horizontal deflection element, and is oscillated so that the laser beam is scanned in the vertical direction of the screen 60 by the vertical deflection element.

  An image based on the image signal is displayed on the screen 60 by scanning the laser beam in the horizontal direction and the vertical direction by the optical deflector 100.

  The optical deflector 100 and the light source driving device 260 in FIG. 1 constitute the image display device of the first embodiment.

  FIG. 3 shows the IL characteristic of the semiconductor laser that is one of the R light source 51r, the G light source 51g, and the B light source 51b. As shown in FIG. 3, when the drive current value is equal to or greater than the threshold value Ith, the semiconductor laser emits laser light. The drive current value and the laser output power have a substantially linear relationship as a whole.

  In FIG. 3, point p1 is a point with a laser output power of 1 mW, and point p2 is a point with a laser output power of 2 mW. The point p1 is a point corresponding to the laser output power expressing the pixel value 2, and the point p2 is a point corresponding to the laser output power expressing the pixel value 4.

  First, it is assumed that the IL characteristic is a linear characteristic as a whole. As shown in FIG. 4A, the laser output power may be increased as the luminance value of the image signal indicated by the alternate long and short dash line increases. Here, for ease of explanation, as laser output power, discrete 0.5, 1, 1.5, 2, 2.5,..., 7, 7.5, 8, 8.5 (mW) Only shows.

  Drive current values for obtaining laser output powers of 1, 2, 3, 4, 5, 6, 7, and 8 (mW) are I1, I2, I3, I4, I5, I6, I7, and I8. According to FIG. 3, for example, the drive current value I1 is about 85 (mA), and the drive current value I2 is about 87 (mA).

  As shown in FIG. 3, a kink region 30 exists in a region where the drive current value near the threshold value Ith is small, as surrounded by a one-dot chain line. In the kink region 30, the relationship between the drive current value and the laser output power is not linear. Since the IL characteristics of the R light source 51r, the G light source 51g, and the B light source 51b are not the same, the characteristics in the kink region 30 are different.

  The broken line shown in the kink area | region 30 of FIG. 3 has shown the preferable linear characteristic of a drive current value and laser output power. It is assumed that the laser output power within 1.5 mW is included in the kink region 30.

  In FIG. 3, it is assumed that the laser output power necessary for displaying a low-luminance image (pixel) is 1 mW, for example. If the inside of the kink region 30 has a linear characteristic as indicated by a broken line and the characteristics in the kink region 30 in the IL characteristics of the R light source 51r, the G light source 51g, and the B light source 51b are the same, the color shift is Almost does not occur.

  Actually, however, the characteristics in the kink region 30 are not linear, and the characteristics in the kink region 30 differ among the R light source 51r, the G light source 51g, and the B light source 51b. Therefore, color misregistration occurs.

  Therefore, in the first embodiment, when displaying each pixel constituting an image, the control unit 200 operates as follows. When the pixel has a predetermined low-brightness pixel value expressed by the laser output power in the kink region 30, the pixel value replacement unit 210 converts the low-brightness pixel value to a larger laser output outside the kink region 30. Replace with pixel value expressed in power.

  At this time, the pixel value replacement unit 210 increases the laser output power by replacing the pixel value, so that the luminance value does not become larger than a predetermined low luminance to be displayed. The pixel value at the same position in the frame is replaced with 0.

  The operation of the pixel value replacement unit 210 will be further described with reference to FIG. 5A shows a state before the pixel value is replaced by the pixel value replacement unit 210. FIG. In the image signal, the same frame is assumed to be six frames F1 to F6, and here, four frames F1 to F4 are shown. The display method for displaying the frames F1 to F4 as shown in FIG. 5A as they are is a normal image display method.

  The frames F1 to F6 are formed by arranging pixels in the horizontal direction and the vertical direction. In FIG. 5, only partial pixels Px1 to Px7 are illustrated. Here, for convenience of illustration, a state in which the number of pixels is significantly reduced is shown.

  A pixel value 2 included in the pixel Px6 illustrated in FIG. 5A is a low-brightness pixel value represented by the laser output power in the kink region 30. As shown in FIG. 5B, the pixel value replacement unit 210 replaces the pixel value of the pixel Px6 of the frame F1 with the pixel value 4 expressed by the laser output power outside the kink region 30. The pixel value replacement unit 210 replaces the pixel value of the pixel Px6 of the frame F2 with the pixel value 0.

  Similarly, the pixel value replacement unit 210 replaces the pixel value of the pixel Px6 in the frame F3 with the pixel value 4, and replaces the pixel value of the pixel Px6 in the frame F4 with the pixel value 0. The same applies to frames F5 and F6 not shown in FIG.

  FIG. 6 shows how the pixel value of the pixel Px6 is expressed by focusing on only the pixel Px6 in the frames F1 to F6. FIG. 6A shows a state in which the pixel value is not replaced by the pixel value replacement unit 210 as shown in FIG. That is, FIG. 6A corresponds to a normal image display method.

  In FIG. 6A, the pixels Px6 of the frames F1 to F6 are displayed with the pixel value 2 expressed by the laser output power in the kink region 30. Actually, however, since the characteristics in the kink region 30 are not linear, the pixel values different from the pixel values 2 are displayed as indicated by the one-dot chain line.

  Since the position of the alternate long and short dash line varies depending on variations in characteristics of the R light source 51r, the G light source 51g, and the B light source 51b, a color shift occurs.

  FIG. 6B shows a state in which the pixel value is replaced by the pixel value replacement unit 210 as shown in FIG. In FIG. 6B, the pixel Px6 of the frames F1, F3, and F5 is displayed with a pixel value 4 represented by the laser output power outside the kink region 30, and the pixel Px6 of the frames F2, F4, and F6 has a pixel value of 0. It is said.

  Therefore, when viewed in the entire frames F1 to F6 in FIG. 6B, the pixel value of the pixel Px6 is displayed with an average pixel value of 2 as indicated by the alternate long and short dash line. Since the pixel value 4 is a pixel value expressed by the laser output power outside the kink region 30, almost no color misregistration occurs.

  If the plurality of frames when the same frame is continuous is an even number, the following may be performed. When displaying low-luminance pixels expressed by the laser output power in the kink region 30, the pixel values in half of the plurality of frames are doubled, and the pixel values in the remaining half frames Is set to 0.

  If the number of frames is odd, increase the pixel value in a partial frame of the plurality of frames so that the average of the whole of the plurality of frames is the pixel value to be displayed. It may be 0.

  It is assumed that the pixel value at a predetermined pixel position in the image signal is a first pixel value expressed by a laser output power equal to or lower than a threshold that is a predetermined laser output power. The pixel value replacement unit 210 may replace the pixel values in the plurality of frames so that the average pixel value when the pixel values at the predetermined pixel positions are averaged in the plurality of frames becomes the first pixel value.

  The pixel value replacement unit 210 replaces a pixel value at a predetermined pixel position in any one of the plurality of frames with a second pixel value expressed by a laser output power exceeding a threshold value, and determines a predetermined value in another frame of the plurality of frames. The pixel value at the pixel position may be replaced with 0.

  In the above description, the pixel value 2 represented by the laser output power at the point p1 in the kink region 30 is taken as an example of the low luminance pixel. The same applies to the case where the pixel value is expressed by the laser output power other than the point p1 in the kink region 30.

  For example, if the pixel value 3 is a pixel value expressed by a laser output power of 1.5 mW, the pixel value replacement unit 210 may replace a pixel value equal to or lower than the pixel value 3 in the same manner as described above. According to the first embodiment, since laser output power of 1.5 mW or less is not used, the laser output power to be used is 2 mW or more as shown in FIG. It becomes.

  A point pth shown in FIG. 3 is a threshold value that is a predetermined laser output power and indicates the inner and outer boundaries of the kink region 30. The control unit 200 (pixel value replacement unit 210) may set the laser output power equal to or higher than the maximum laser output power in the kink region 30 in the IL characteristic of the semiconductor laser as the threshold value pth.

  When the control unit 200 causes the laser light output from the light source 51 to represent a pixel value having a luminance corresponding to the first laser output power exceeding the threshold value pth, the pixel value replacement unit 210 does not replace the pixel value. .

  When the control unit 200 causes the laser light output from the light source 51 to express a pixel value having a luminance corresponding to the second laser output power equal to or less than the threshold value pth, the pixel value replacement unit 210 is a part of a plurality of frames. The pixel value of this frame may be replaced with the second pixel value, the pixel values of other frames may be replaced with 0, and the average pixel value when averaged over a plurality of frames may be used as the first pixel value.

  The light source driving device 260 may be used other than the image display device. When the light source driving device 260 is used in an image display device that displays an image with laser light emitted from the light source 51, the control unit 200 may control the driving unit 40 as follows.

  The control unit 200 controls the drive unit 40 such that the drive current value of the drive signal supplied from the drive unit 40 to the light source 51 increases as the luminance value of the image signal for displaying an image increases.

  As described above, the image display device according to the first embodiment includes the optical deflector 100 that displays the image by deflecting the laser light emitted from the light source 51 in the horizontal direction and the vertical direction, and the light source driving device 260. Even when a low-luminance image is displayed, the occurrence of color misregistration can be suppressed.

Second Embodiment
The configuration and operation of the light source driving device and the image display device according to the second embodiment will be described with reference to FIG. In FIG. 7, the same parts as those of the light source driving apparatus and the image display apparatus according to the first embodiment shown in FIG.

  In the light source driving device and the image display device of the second embodiment, a control unit 201 is provided instead of the control unit 200. The control unit 201 receives a vertical synchronization signal and a horizontal synchronization signal which are not shown in FIG. The control unit 201 includes a pixel value replacement unit 211.

  The drive unit 40, the laser light generation unit 50, and the control unit 201 in FIG. 7 constitute a light source drive device 261 of the second embodiment. The optical deflector 100 and the light source driving device 261 in FIG. 7 constitute the image display device of the second embodiment.

  Also in the second embodiment, when the pixel has a predetermined low-brightness pixel value expressed by the laser output power in the kink region 30, the pixel value replacement unit 211 converts the low-brightness pixel value into the kink region. Replace with a pixel value represented by a larger laser output power outside of 30.

  At this time, the pixel value replacement unit 211 increases the laser output power by replacing the pixel value, so that the luminance value does not become larger than a predetermined low luminance to be displayed. The pixel value at the same position in the frame is replaced with 0.

  However, in the second embodiment, the pixel value replacement method is different between the odd-numbered frame and the even-numbered frame.

  The operation of the pixel value replacement unit 211 will be specifically described using the first example shown in FIG. 8A shows a state before pixel values are replaced by the pixel value replacement unit 211. FIG. In the image signal, the same frame is two consecutive frames F1 and F2. The frame F1 is an odd frame, and the frame F2 is an even frame.

  L1, L2, L3, L4... Indicate the row numbers of the frames F1, F2. L1, L3,... Are odd rows, and L2, L4,. R1, R2, R3, R4... Indicate pixel column numbers.

  Since the vertical synchronization signal and the horizontal synchronization signal are input to the control unit 201, the control unit 201 (pixel value replacement unit 211) determines whether the frame of the image to be displayed is an odd frame or an even frame. Can be determined.

  Further, the control unit 201 (pixel value replacement unit 211) can determine whether the pixel of the image to be displayed is an odd row pixel or an even row pixel.

  Here, it is assumed that the pixel value of 3 or less is the first pixel value expressed by the laser output power equal to or less than the threshold that is the predetermined laser output power described above.

  In the second embodiment, in an odd frame, the pixel value of an odd row pixel having a pixel value of 3 or less is doubled, and the pixel value of an even row pixel value of 3 or less is set to 0. On the other hand, in the even-numbered frame, the pixel values of the odd-numbered pixels having the pixel value of 3 or less are set to 0, and the pixel values of the even-numbered pixels having the pixel value of 3 or less are doubled.

  Specifically, it is as follows. As shown in FIG. 8A, the pixels in the rows L1 to L4 in the column R3 have pixel values of 2, 3, 3, and 2, respectively, and are all the first pixel values. The pixels in the rows L1 to L4 in the column R6 have pixel values 2, 2, 1, and 1, respectively, and are all the first pixel values.

  As shown in FIG. 8B, the pixel value replacement unit 211 doubles the pixel value of the pixel in the row L1 in the columns R3 and R6 to obtain the pixel value 4 in the frame F1, and in the columns R3 and R6, respectively. The pixel value of the pixel in the row L3 is doubled to obtain pixel values 6 and 2, respectively.

  At the same time, as shown in FIG. 8B, the pixel value replacement unit 211 sets the pixel values of the pixels in the rows L2 and L4 in the columns R3 and R6 to 0 in the frame F1.

  On the other hand, as shown in FIG. 8B, the pixel value replacement unit 211 sets the pixel values of the pixels in the rows L1 and L3 in the columns R3 and R6 to 0 in the frame F2.

  At the same time, as shown in FIG. 8B, the pixel value replacement unit 211 doubles the pixel values of the pixels in the row L2 in the columns R3 and R6 to become pixel values 6 and 4, respectively, in the frame F2. The pixel values of the pixels in row L4 in columns R3 and R6 are doubled to become pixel values 4 and 2, respectively.

  In the first example shown in FIG. 8, the pixel value of some pixels remains the first pixel value after the pixel value replacement (pixel value 3 or less), but if the pixel value before replacement is 2 or more, All are replaced with the second pixel value expressed by the laser output power exceeding the threshold value.

  Furthermore, the operation of the pixel value replacement unit 211 will be specifically described using a second example shown in FIG. As shown in FIG. 9A, in the second example, the pixel values of the pixels in the rows L2 and L3 in the column R3 are 5.

  Also in this case, according to the pixel value replacement method described above, the pixel value replacement unit 211 doubles the pixel value of the pixel in the row L1 in the column R3 in the frame F1, as shown in FIG. 9B. The pixel value is 4, and the pixel value of the pixel in the row L4 is 0.

  On the other hand, as shown in FIG. 9B, the pixel value replacement unit 211 sets the pixel value of the pixel in the row L1 in the column R3 to 0 and doubles the pixel value of the pixel in the row L4 in the frame F2. The pixel value is 4.

  FIG. 10 summarizes the pixel value replacement method in the pixel value replacement unit 211 in a table format. In the odd frame, the pixel value replacement unit 211 doubles the pixels below the threshold in the odd rows (pixels having the first pixel value) and sets the pixels below the threshold in the even rows to 0.

  In the even frame, the pixel value replacement unit 211 sets the pixels below the threshold in the odd rows to 0, and doubles the pixels below the threshold in the even rows.

  If the pixel exceeds the threshold value (if the pixel has the second pixel value), the pixel value replacement unit 211 converts the pixel value regardless of the odd-numbered frame and the even-numbered row regardless of the odd-numbered frame and the even-numbered frame. Instead, the pixel value is used as it is.

  Of course, the pixel value replacement unit 211 may interchange the condition for doubling the pixel value and the condition for setting it to 0. That is, the pixel value replacement unit 211 sets the pixels below the threshold in the odd rows to 0 in the odd frame, doubles the pixels below the threshold in the even rows, and doubles the pixels below the threshold in the odd rows in the even frame. The pixels below the threshold value in even rows may be set to 0.

  The pixel value replacement unit 211 doubles the pixel value at the predetermined pixel position in the odd row and the pixel value at the predetermined pixel position in the even row in one of the odd frame and the even frame among the plurality of frames. It may be 0.

  As described above, the predetermined pixel position is the position of the pixel having the first pixel value expressed by the laser output power equal to or lower than the threshold value.

  The pixel value replacement unit 211 may set the pixel value at the predetermined pixel position in the odd row to 0 and the pixel value at the predetermined pixel position in the even row to 0 in the other frame of the odd frame and the even frame.

  According to 2nd Embodiment described above, in addition to the effect similar to 1st Embodiment, there exist the following effects. According to the second embodiment, the pixel values of adjacent rows in the same column do not become 0 at the same time. Therefore, compared to the first embodiment, it is possible to display a smooth image (moving image).

<Third Embodiment>
The configuration and operation of the light source driving device and the image display device according to the third embodiment will be described with reference to FIG. In FIG. 11, the same parts as those of the light source driving apparatus and the image display apparatus according to the second embodiment shown in FIG.

  In the light source driving device and the image display device of the third embodiment, a control unit 202 is provided instead of the control unit 201. The control unit 202 includes a pixel value replacement unit 212.

  The drive unit 40, the laser light generation unit 50, and the control unit 202 in FIG. 11 constitute a light source drive device 262 of the third embodiment. The optical deflector 100 and the light source driving device 262 in FIG. 11 constitute the image display device of the third embodiment.

  The operation of the pixel value replacement unit 212 will be specifically described using an example shown in FIG. 12A shows a state before the pixel value is replaced by the pixel value replacing unit 212. FIG. The frame F1 is an odd frame, the frame F2 is an even frame, and the frames F1 and F2 are not the same. Definitions of L1, L2, L3, L4... And R1, R2, R3, R4... Are the same as those in FIGS.

  Here, it is assumed that the pixel value of 3 or less is the first pixel value expressed by the laser output power equal to or less than the threshold that is the predetermined laser output power described above. In the example shown in FIG. 12A, in the frame F1, the pixel values of the pixels in the rows L1 and L4 in the column R3 and the rows L1 to L4 in the column R6 are equal to or less than the pixel value 3, and in the frame F2, The pixel values of the pixels in the row L1 in R3 and the rows L3 and L4 in the column R6 are equal to or less than the pixel value 3.

  In the third embodiment, in the odd-numbered frame, when any pixel value at the same position in the odd-numbered frame and the even-numbered frame is less than or equal to the pixel value 3, the pixel value of the odd-numbered row is changed to the pixel value of the odd-numbered frame and the even-numbered frame. And the pixel value of pixels in even rows are set to 0.

  On the other hand, in the even-numbered frame, if any of the pixel values at the same position in the odd-numbered frame and the even-numbered frame is 3 or less, the pixel value of the odd-numbered pixel is set to 0, and the pixel value of the even-numbered pixel is set to the odd-numbered frame. The sum of the pixel value and the pixel value of the even frame is used.

  Specifically, it is as follows. As shown in FIG. 12A, in the frame F1, the pixels in the rows L1 and L4 in the column R3 and the pixels in the rows L1 to L4 in the column R6 have a pixel value of 3 or less, and the pixel to be replaced is a pixel value. It becomes.

  In the frame F2, each pixel in the row L1 in the column R3 and the rows L3 and L4 in the column R6 has a pixel value of 3 or less, and is a pixel to be replaced. In addition to this, each pixel in the row L4 in the column R3 and each of the rows L1 and L2 in the column R6 exceeds the pixel value 3, but the pixel at the same position in the frame F1 is less than or equal to the pixel value 3, so the pixel value is replaced. This is the target pixel.

  In the frame F1, the pixel value replacement unit 212, as shown in FIG. 12B, the pixel values 2, 2, and 2 of the pixels in the odd rows L1 and the odd rows L1 and L3 in the column R3. 1 and the pixel values 3, 5, and 3 of the pixels at the same position in the frame F2 are added, and the pixel values 2, 2, and 1 are replaced with the pixel values 5, 7, and 4, which are addition values.

  In the frame F1, the pixel value replacement unit 212, as shown in FIG. 12B, the pixel values 2 of the pixels in the even-numbered rows L4 and the even-numbered rows L2, L4 in the column R3. 2 and 3 are all replaced with a pixel value of 0.

  On the other hand, in the frame F2, as shown in FIG. 12B, the pixel value replacement unit 212 sets all the pixel values 2, 5, and 3 of the pixels in the row L1 in the column R3 and the rows L1 and L3 in the column R6. Replace with the value 0.

  Further, in the frame F2, as shown in FIG. 12B, the pixel value replacement unit 212 and the pixel values 5, 5, and 2 of the pixels in the rows L4 and L4 in the column R3 and the rows L2 and L4 in the column R6 and the frame F1. The pixel values 2, 2, and 3 of the pixels at the same position in are added, and the pixel values 5, 5, and 2 are replaced with the pixel values 7, 7, and 5, which are addition values.

  FIG. 13A shows the average value Ave (F1, F2) of the frames F1, F2 shown in FIG. FIG. 13B shows the average value Ave (F1, F2) of the frames F1, F2 shown in FIG. The average value Ave (F1, F2) is the same before and after the pixel value replacement by the pixel value replacement unit 212.

  FIG. 14 summarizes the pixel value replacement method in the pixel value replacement unit 212 in a tabular form. The pixel value replacement unit 212 executes the following replacement process when any pixel has a threshold value or less (the pixel having the first pixel value) at the same pixel position in the odd frame and the even frame.

  In the odd frame, the pixel values at the same pixel positions in the odd and even frames are added in the odd row, and the original pixel value is replaced with the added value. In the even row, the original pixel value is replaced with the pixel value 0. To do.

  In the even frame, the original pixel value is replaced with the pixel value 0 in the odd row, and the pixel value at the same pixel position in the odd frame and the even frame is added in the even row, and the original pixel value is replaced with the added value. To do.

  When both pixels exceed the threshold value (the pixel having the second pixel value) at the same pixel position in the odd frame and the even frame, the pixel value replacement unit 212 sets the odd row and the odd row regardless of the odd frame and the even frame. Regardless of the even-numbered row, the pixel value is not converted and is used as it is.

  Of course, the pixel value replacement unit 212 may exchange the condition for setting the pixel value to the addition value and the condition for setting the value to 0. That is, the pixel value replacement unit 212 replaces the pixel value with 0 in the odd-numbered row in the odd-numbered frame, replaces with the added value in the even-numbered row, replaces with the added value in the odd-numbered row in the even-numbered frame, You may substitute 0.

  According to 3rd Embodiment described above, in addition to the effect similar to 1st and 2nd embodiment, there exist the following effects. According to the third embodiment, even if the same pixel value does not exist in successive frames, an image can be displayed without using a low-brightness pixel value represented by the laser output power in the kink region 30. .

  When displaying a moving image such as a natural image or a movie, the same pixel value is not always continuous in successive frames. In addition, when displaying information related to vehicles such as navigation images and fuel level, in general, the same frame often continues in succession, but the same frame does not continue when the image is changed at high speed. Sometimes. Thus, the third embodiment can be used even when the same frame is not continuous.

  The present invention is not limited to the first to third embodiments described above, and various modifications can be made without departing from the scope of the present invention. The optical deflector 100 is preferably configured using MEMS technology, but is not limited thereto. The optical deflector 100 only needs to have a function of deflecting laser light in the horizontal direction and the vertical direction, and the specific configuration is not particularly limited.

40 Drive Unit 51 Light Source 51r R Light Source (Semiconductor Laser)
51g G light source (semiconductor laser)
51b B light source (semiconductor laser)
DESCRIPTION OF SYMBOLS 100 Optical deflector 200,201,202 Control part 210, 211,212 Pixel value substitution part 260 Light source drive device

Claims (6)

A light source composed of a semiconductor laser that emits laser light;
A drive unit that drives the light source by a drive signal that increases or decreases a drive current value according to each pixel value in the image signal;
A pixel value at the predetermined pixel position when a pixel value at a predetermined pixel position of a plurality of consecutive frames in the image signal includes a first pixel value expressed by a laser output power equal to or lower than a threshold that is a predetermined laser output power; The pixel value at the predetermined pixel position in any one of the plurality of frames is expressed by the laser output power exceeding the threshold value so that the average pixel value when the two pixels are averaged is the first pixel value. A pixel value replacement unit that replaces the pixel value at the predetermined pixel position in another frame of the plurality of frames with 0,
A control unit that controls the drive unit to drive the light source based on an image signal in a state where the pixel value at the predetermined pixel position is replaced by the pixel value replacement unit;
A light source driving device comprising: The plurality of frames are even;
The pixel value replacement unit doubles the pixel value at the predetermined pixel position in a half frame of the plurality of frames, and sets the pixel value at the predetermined pixel position in the remaining half frame to 0. The light source driving device according to claim 1. The plurality of frames are even;
The pixel value replacement unit includes:
Of the plurality of frames, in one of the odd frame and the even frame, the pixel value at the predetermined pixel position in the odd row is doubled, and the pixel value at the predetermined pixel position in the even row is set to 0,
Among the plurality of frames, in the other frame of the odd frame and the even frame, the pixel value at the predetermined pixel position in the odd row is set to 0, and the pixel value at the predetermined pixel position in the even row is doubled. The light source driving device according to claim 1, wherein: The plurality of frames are even;
The pixel value replacement unit includes:
When any of the plurality of frames has the first pixel value at the same pixel position in the odd frame and the even frame,
In one of the odd frame and the even frame, the pixel value at the predetermined pixel position in the odd row is added to the pixel value at the predetermined pixel position in the odd frame and the pixel value at the predetermined pixel position in the even frame. And the pixel value at the predetermined pixel position in the even-numbered row is replaced with 0,
In the other of the odd frame and the even frame, the pixel value at the predetermined pixel position in the odd row is replaced with 0, and the pixel value at the predetermined pixel position in the even row is replaced with the pixel value at the predetermined pixel position in the odd frame. The light source driving device according to claim 1, wherein the light source driving device is replaced with an added value obtained by adding the pixel value and the pixel value at the predetermined pixel position in the even frame.   The pixel value replacement unit sets a laser output power equal to or higher than a maximum laser output power in a kink region in the IL characteristic of the semiconductor laser as the threshold value. The light source driving device according to any one of the preceding claims. The light source driving device according to any one of claims 1 to 5,
An optical deflector for displaying an image by deflecting laser light emitted from the light source in a horizontal direction and a vertical direction;
An image display device comprising:

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