JP2014130288A - Image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image display device which requires less time to be ready for displaying an image, and to provide an image display method and a program.SOLUTION: An image display device 100 includes; a light source unit 110 capable of generating a laser beam in accordance with an input image signal using a plurality of laser diodes 111; and a scanning mirror unit 120 capable of displaying an image by oscillating in an H-axis direction, corresponding to the horizontal direction of an image corresponding to the image signal, and in a V-axis direction, corresponding to the vertical direction of the image, to reflect the laser beam generated by the light source unit 110 and scan a projection surface therewith. When temperature of each of the plurality of laser diodes 111 is within a first temperature range, the light source unit 110 generates the laser beam using only some of the plurality of laser diodes 111.

Description

  The present invention relates to an image display device.

  2. Description of the Related Art A laser scanning type image display apparatus that displays an image on a projection surface by reflecting laser light projected from a light source with a scanning mirror and raster-scanning the projection surface with the reflected light beam is known. This laser scanning type image display device reciprocally swings the scanning mirror left and right when drawing horizontal scanning lines, and swings the scanning mirror vertically according to the number of scanning lines constituting the image. . In recent years, for example, a MEMS (Micro Electro Mechanical Systems) mirror is used as the scanning mirror to reduce the size of a laser scanning image display device, and various application products such as a head-up display and a head-mounted display have been developed. ing.

  Patent Document 1 is provided with lasers of a plurality of colors, typically RGB three-color laser light sources (laser diodes), which emit three laser diodes according to the RGB levels of the pixels constituting the image, and combine them. An image display device capable of displaying a color image by wave is disclosed.

Japanese Patent Application No. 2012-147736

  In many cases, the laser diode manufacturer sets a guaranteed operating temperature for the laser diode. The operation guarantee temperature is a limit temperature at which the laser diode should operate normally, and is indicated by an upper limit temperature and a lower limit temperature. Operation outside the guaranteed operating temperature has an adverse effect on the laser diode, such as a reduction in lifetime. Since image display devices are often used for applications that require reliable and long-life operation such as in-vehicle use, it is particularly necessary to consider the guaranteed operating temperature.

  However, considering the operation guarantee temperature, when the image display device is started at a high temperature or a low temperature, the laser diode cannot be operated immediately, and as a result, there is a problem that it takes time to display an image.

  The present invention has been made to solve such a problem, and an object thereof is to provide an image display apparatus capable of reducing the time required for image display.

  Accordingly, the present invention provides a light source unit capable of outputting laser light based on an input image signal using a plurality of laser diodes, and an H-axis direction corresponding to the horizontal direction of the image based on the image signal. And a scanning mirror unit that vibrates in the V-axis direction corresponding to the vertical direction of the image, reflects the laser beam output from the light source unit, and scans the projection surface, thereby displaying an image. When the temperature of each of the plurality of laser diodes is within a first temperature range, the light source unit outputs an image using only a part of the plurality of laser diodes. Providing equipment.

  It is possible to provide an image display device capable of reducing the time required for image display.

1 is a diagram showing a configuration of an image display device 100 according to an embodiment. 1 is a diagram showing a configuration of an image display device 100 according to an embodiment. It is a figure which shows the temperature of the laser diode 111 at the time of cooling the laser diode 111 of the image display apparatus 100 concerning Embodiment. It is a figure which shows operation | movement of the image display apparatus 100 concerning embodiment.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. Specific numerical values and the like shown in the embodiment are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

  First, the configuration of the image display apparatus 100 according to the embodiment of the present invention will be described with reference to FIGS. 1 and 2. The image display device 100 is a laser-type display device such as a head-up display, a head-mounted display, or a laser-type projector, for example.

  As illustrated in FIG. 1, the image display apparatus 100 includes a light source unit 110, a scanning mirror unit 120, and a detection unit 103.

  The light source unit 110 drives a laser light source based on the input image signal, and outputs laser light to the scanning mirror unit 120 at the subsequent stage. The light source unit 110 includes, for example, a microcomputer and performs the following series of processes.

  An original image signal is input to the light source unit 110 via a video interface (not shown). The light source unit 110 decodes the original image signal according to the image type. For example, when the original image signal is an analog image signal (component video signal), the original image signal is converted into digital image data composed of digital color signals of three colors (RGB) and a horizontal synchronization signal by decoding processing. And a synchronizing signal including a vertical synchronizing signal.

  The light source unit 110 once writes the decoded image data in the buffer, then reads the image data from the buffer line by line on the main scanning line at a timing suitable for the laser scanning type image display device, and outputs it to the subsequent stage. That is, the light source unit 110 reads out image data in accordance with a timing signal (dot clock, display period instruction signal) adjusted based on horizontal swing of a scanning mirror unit to be described later.

  The light source unit 110 includes a D / A conversion unit (not shown), and applies a drive current to the laser light source according to the three colors (RGB) constituting the read image data to obtain a laser light source of three colors (RGB). It emits light with the brightness of.

  As shown in FIG. 2, the light source unit 110 includes a red laser diode 111R, a blue laser diode 111B, and a green laser diode 111G as laser light sources in order to obtain three colors of RGB. Each laser diode is driven by a red driver, a green driver, and a blue driver (not shown).

  Each pixel data constituting the image data has color information composed of three colors of R (red), G (green), and B (blue) for each pixel. The red driver, the green driver, and the blue driver apply current to the laser diode 111 of each color according to the luminance information of each color of each pixel. Note that it is preferable that each laser does not emit light when drawing black. If black is drawn in this way, the laser scanning image display device can reduce power consumption as compared with a liquid crystal display or the like that always emits light to the entire drawing area by a backlight.

  The light source unit 110 further includes a temperature sensor that detects the temperatures of the red laser diode 111R, the blue laser diode 111B, and the green laser diode 111G, and is configured so that the microcomputer can acquire the detection value.

  The light source unit 110 further includes mirrors 112R, 112G, and 112B. Each of the mirrors 112 is a dichroic mirror that transmits or reflects a color having a predetermined wavelength. The dichroic mirror has a property of substantially reflecting light incident on one surface and substantially transmitting light incident on the other surface. By combining a plurality of mirrors 112, the laser beams of three colors are incident on the scanning mirror unit 120 at a predetermined angle as a light beam combined on one axis. A condensing lens (not shown) may be appropriately disposed on the optical path to collect the laser light.

  In addition, the light source unit 110 rearranges drawing data when drawing in both the forward path and the return path in horizontal vibration. Moreover, you may correct | amend the image distortion by the amplitude of the MEMS device mentioned later, and the distortion by the curved surface of the glass at the time of vehicle mounting. In addition, the projection axis of each laser may be corrected and the drawing start position may be adjusted.

  As described above, in the present embodiment, the light source unit 110 also has functions as an image processing unit, a laser driving unit, and a control unit, but these may be integrated, It may be a separate body.

  Next, the configuration of the scanning mirror unit 120 will be described. The scanning mirror unit 200 is a so-called MEMS device, and includes a mirror driven by a piezoelectric element, and a control unit that drives the mirror by applying a current to the piezoelectric element at a predetermined timing. The mirror has two swing axes orthogonal to each other, and the image light beam is raster-scanned by swinging the mirror in two directions. Hereinafter, for convenience of explanation, the mirror swing axis corresponding to the horizontal scan (main scanning direction) of the image is the H-axis, and the mirror swing axis corresponding to the vertical scan (sub-scanning direction) of the image is shown. This will be described as the V axis.

  In the present embodiment, the oscillation of the mirror in the H-axis direction, that is, the main scanning direction is resonance oscillation. The oscillation may be performed based on another oscillation source, but even in that case, the frequency is preferably close to the resonance frequency. On the other hand, the swing in the V-axis direction, that is, the sub-scanning direction is non-resonant drive. The control unit included in the light source unit 110 synchronizes the vibration cycle in the V-axis direction with the swing of the H-axis, and Adjust according to the rate.

  Here, the problem of the present invention will be described again in detail. The guaranteed operating temperature of the laser diode 111 varies greatly depending on the color. For example, the guaranteed operating temperature of the laser diode 111B that outputs blue laser is an upper limit of 80 degrees and a lower limit of -10 degrees. The guaranteed operating temperature of the laser diode 111R that outputs the red laser is an upper limit of 60 degrees and a lower limit of -10 degrees. The guaranteed operating temperature of the laser diode 111G that outputs the green laser has an upper limit of 60 degrees and a lower limit of 0 degrees.

  In the image display device 100, when the image display device 100 is activated in a state where the temperature of the laser diode 111 is higher than the upper limit of the operation guaranteed temperature of the laser diode 111, the light source unit 110 or the like is provided by a cooling element (not shown) or the like (for example, Peltier element). Cooling of the laser diode 111 is started.

  FIG. 3 shows a temperature change of the laser diode 111 when the image display apparatus 100 is started at the ambient temperature of 85 degrees and is cooled by the cooling element. In this graph, the vertical axis represents the temperature change. That is, at 0 degrees on the vertical axis, the temperature of the laser diode 111 is 85 degrees. At −25 degrees on the vertical axis, the temperature of the laser diode 111 is 60 degrees.

  According to the graph of FIG. 3, the laser diodes 111R (red) and the laser diode 111G (green) having the lowest upper limit of the guaranteed operating temperature reach the guaranteed operating temperatures of all the RGB laser diodes 111. Is the time when the upper limit of 60 degrees is reached. That is, the image display apparatus 100 can start full-color image display only after about 120 seconds from the activation.

  However, since the image display apparatus is often used for applications that require a quick operation such as in-vehicle, it is desired that the time lag until such image display is reduced as much as possible.

  Based on the above, the characteristic operation of the image display apparatus 100 in the present embodiment will be described using the flowchart of FIG.

(S101: Determine whether only one of the laser diodes 111 is within the guaranteed operating range)
The light source unit 110 acquires the temperatures of the laser diode 111R, the laser diode 111G, and the laser diode 111B from the temperature sensor. Further, it is assumed that the light source unit 110 stores therein information indicating the guaranteed operating temperature of the laser diode 111 in advance. If one of the laser diodes 111 is within the guaranteed operating temperature while the other laser diode 111 is outside the guaranteed operating temperature, the process of S102 is performed. That is, the temperature of each of the laser diode 111R, the laser diode 111G, and the laser diode 111B is within a temperature range in which only a part of the laser diodes (here, the laser diode 111B) is guaranteed to operate (in this embodiment, 60 degrees to 80 degrees). ), The light source unit 110 performs the process of S102. In other cases, the process of S103 is performed.

(S102: Display using laser diode 111 that is within the guaranteed operating range)
The light source unit 110 starts image display using the laser diode 111 determined to be within the guaranteed operating temperature. For example, if the temperature of each laser diode is in the range of 60 to 80 degrees C and only the laser diode 111B is within the guaranteed operating temperature, use only a blue laser that can be driven and a message such as "Please wait" Draw images prepared in advance, such as opening screens such as logos. Here, three types of images to be displayed may be prepared in a single color of RGB. Alternatively, a monochrome image prepared in advance may be displayed in a single color.

  Alternatively, instead of a screen prepared in advance, a normal screen, for example, a speed display that is normally performed in full color may be displayed in a single color. Specifically, an input image signal (RGB signal) for displaying a normal screen is converted into a monochrome image signal, and the monochrome image is obtained by using only a part of the laser diodes (here, the laser diode 111B). A monochrome image can be displayed by outputting a laser beam based on the above.

  As described above, when the temperature of each of the laser diode 111R, the laser diode 111G, and the laser diode 111B is within a temperature range in which only some laser diodes (here, the laser diode 111B) are guaranteed to operate, the light source unit 110 Outputs laser light using only some of the laser diodes.

(S103: Determine whether all laser diodes 111 are within the guaranteed operating range)
When all the laser diodes 111 are within the guaranteed operating temperature, the light source unit 110 performs the process of S104. On the other hand, when all the laser diodes 111 are outside the guaranteed operating temperature, the process proceeds to S105.

(S104: Full color display using all laser diodes 111)
The light source unit 110 starts full-color display using all the laser diodes 111. For example, when an image prepared in advance is drawn using only a drivable monochromatic laser, the display of the image is terminated, and a normal screen display using RGB full color is performed. Alternatively, if the normal screen is displayed in a single color, the normal screen display in RGB full color is continued. That is, in the light source unit 110, when the temperature of all the laser diodes 111 is within the temperature range that is within the operation guarantee range (in the present embodiment, the range of 0 to 60 degrees), Is used to output laser light based on the input image signal.

  In general, after the image display apparatus 100 is started, the temperature of the laser diode 111 is maintained by a cooling element or the like. Therefore, after all the laser diodes 111 are within the guaranteed operating range, the laser diode 111 does not go out of the guaranteed operating range unless the image display apparatus 100 stops operating. However, in preparation for a failure of the cooling device or the like, it may be configured to periodically check S101 and transition to the processing of S102 if necessary.

(S105: Standby)
If all the laser diodes 111 are outside the operation guarantee temperature, no image display can be executed, and the light source unit 110 waits until any laser diode 111 is cooled to within the operation guarantee temperature. Specifically, the light source unit 110 periodically executes the process of S101.

  The effect by this Embodiment is demonstrated using FIG. 3 again. According to this embodiment, when any one of the laser diodes 111 falls within the guaranteed operating temperature, the monochrome image display by the laser diode 111 can be started. In the example of FIG. 3, since the laser diode 111B (blue) is cooled to 80 degrees, which is the upper limit of the guaranteed operating temperature, about 15 seconds after the image display device 100 is activated, display in a single color can be started.

  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, in the above-described embodiment, the case where the high-temperature laser diode 111 is cooled has been described as an example. However, the present invention is not limited to this, and the same processing can be applied when the laser diode 111 is heated from a low temperature outside the operation guarantee temperature. For example, in the laser diode 111 of the present embodiment, when the temperature of all the laser diodes 111 is within a range of −10 degrees to 0 degrees, laser light is output using only the laser diode 111B and the laser diode 111R. You may make it do. Note that the laser diodes are often provided close to each other, and in this case, the temperatures of the laser diodes are substantially equal. In that case, one temperature sensor may be sufficient.

  In the above-described embodiment, the case where one laser diode 111 first reaches the guaranteed operating temperature is described as an example. However, the present invention is not limited to this, and the present invention is also applicable to cases where a plurality of laser diodes 111 reach the guaranteed operating temperature and other laser diodes 111 are outside the guaranteed operating temperature. In this case, the light source unit 110 can perform monochromatic display using any one of the laser diodes 111 within the guaranteed operating temperature. Alternatively, an image composed of a plurality of colors may be prepared in advance, and the image may be displayed using a plurality of laser diodes 111 that have reached the guaranteed operating temperature in S102.

  In the above-described embodiment, the present invention has been mainly described as a hardware configuration. However, the present invention is not limited to this, and a CPU (Central Processing Unit) executes a computer program for arbitrary processing. Can also be realized. In this case, the computer program can be stored and provided to the computer using various types of non-transitory computer readable media. Non-transitory computer readable media include various types of tangible storage media. Examples of non-transitory computer-readable media include magnetic recording media (for example, flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (for example, magneto-optical disks), CD-ROMs (Read Only Memory), CD-Rs, CD-R / W, semiconductor memory (for example, mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM (Random Access Memory)). The program may also be supplied to the computer by various types of transitory computer readable media. Examples of transitory computer readable media include electrical signals, optical signals, and electromagnetic waves. The temporary computer-readable medium can supply the program to the computer via a wired communication path such as an electric wire and an optical fiber, or a wireless communication path.

DESCRIPTION OF SYMBOLS 100 Image display apparatus 110 Light source part 111 Laser diode 112 Dichroic mirror 120 Scanning mirror part

Claims (5)

A light source unit capable of outputting laser light based on an input image signal using a plurality of laser diodes;
It vibrates in the H-axis direction corresponding to the horizontal direction of the image based on the image signal and the V-axis direction corresponding to the vertical direction of the image, and scans the projection plane by reflecting the laser light output from the light source unit. A scanning mirror unit capable of displaying an image,
The light source unit outputs laser light using only a part of the laser diodes when the temperature of each of the plurality of laser diodes is within a first temperature range;
Image display device. When the temperature of each of the plurality of laser diodes is within a second temperature range different from the first temperature range, the light source unit uses the plurality of laser diodes to input the image signal. The image display apparatus according to claim 1, wherein a laser beam based on the output is output. The image display apparatus according to claim 1, wherein the light source unit outputs laser light based on a single-color image signal prepared in advance when outputting laser light using only the part of the laser diodes. 2. The light source unit, when outputting laser light using only the part of the laser diodes, performs monochrome conversion on the input image signal and outputs laser light based on the monochrome converted image signal. Or the image display apparatus of 2. The first temperature range is within a guaranteed temperature range of the part of the plurality of laser diodes and outside a guaranteed temperature range of the other laser diodes of the plurality of laser diodes. is there,
The image display apparatus of any one of Claims 1-4.