WO2012104968A1

WO2012104968A1 - Image display device, image display method, image display program

Info

Publication number: WO2012104968A1
Application number: PCT/JP2011/051937
Authority: WO
Inventors: 修己靭矢; 良輔下澤; 祐樹中井
Original assignee: パイオニア株式会社
Priority date: 2011-01-31
Filing date: 2011-01-31
Publication date: 2012-08-09

Abstract

An image display device has a plurality of laser light sources of varying wavelengths. A temperature detection means detects the temperature of the laser light sources. A display control means drives the laser light sources and displays an image corresponding to image data. Herein, the display control means changes the tone of the image to be displayed on the basis of the detected temperature, and displays the image. As a result, if the detected laser temperature is high, it is possible to continue displaying through changing the tone by stopping the lasers with a high temperature and reducing output, and it is possible to maintain display of the image to the extent possible, while suppressing the rise in temperature of the lasers.

Description

[Name of invention determined by ISA based on Rule 37.2] Image display device, image display method, image display program

The present invention relates to an image display device that displays an image.

Devices such as projectors that generate projection light by synthesizing light emitted from multiple color laser light sources are known. A typical example is a display device that uses three RGB laser light sources and performs color display.

In general, the operating current of a laser increases as the temperature rises, and when the temperature exceeds a certain temperature level (hereinafter referred to as “allowable maximum temperature”), no optical power is generated even if the current is increased. It is known that when the current is further increased in this state, the laser is damaged and deteriorates. For this reason, it is preferable to use a laser light source at an allowable maximum temperature or less.

In this regard, Patent Document 1 describes a device that stops light emission of a laser light source when a predetermined temperature is exceeded. Further, Patent Document 2 describes an apparatus in which a plurality of laser light sources are mounted for one color (red) and these are switched according to temperature.

Generally, laser light sources of different colors have different allowable maximum temperatures. Therefore, if all the laser light sources are stopped when one laser light source exceeds the allowable maximum temperature, the other laser light sources are not displayed at all even if they are below the allowable maximum temperature. On the other hand, if a plurality of laser light sources are mounted for the same color, an increase in cost is inevitable.

JP 2007-156438 A JP 2009-258207 A

The above are examples of problems to be solved by the present invention. An object of the present invention is to provide an image display device that performs display as much as possible while maintaining each laser light source at or below an allowable maximum temperature.

The invention according to claim 1 is an image display device, wherein at least two laser light sources each having a different wavelength of output light, temperature detecting means for detecting the temperature of the laser light source, and input means for inputting image data. And display control means for driving the laser light source to display an image corresponding to the image data, wherein the display control means changes the color tone of the image based on the temperature detected by the temperature detection means. It is characterized by that.

The invention according to claim 9 is an image display method executed by an image display device including at least two laser light sources each having a different wavelength of output light, and a temperature detection step of detecting a temperature of the laser light source; An input step for inputting image data; and a display control step for driving the laser light source to display an image corresponding to the image data. The display control step is based on a temperature detected by the temperature detecting means. The color tone of the image is changed.

The invention according to claim 10 is an image display program executed by an image display device including at least two laser light sources each having a different wavelength of output light, the temperature detecting means for detecting the temperature of the laser light source, and the image The image display device functions as input means for inputting data, display control means for driving the laser light source to display an image corresponding to the image data, and the display control means detects the temperature detected by the temperature detection means. The color tone of the image is changed based on the above.

It is a block diagram which shows the structure of the image display apparatus which concerns on the Example of this invention. (A) The relationship between the operating current of the laser light source and the output power is shown. (B) It is a chromaticity diagram which shows the range of the color which can be displayed with the laser light source of RGB 3 colors. It is an example of a display by 1st Example. It is a flowchart of the display control process by 1st Example. (A) The relationship between the usage time of the laser light source and the cumulative failure rate is shown. (B) The example of a change of the display color by 2nd Example is shown. The other example of a display color change by 2nd Example is shown. It is a flowchart of the display control process by 2nd Example.

In a preferred embodiment of the present invention, the image display device includes at least two laser light sources having different output light wavelengths, temperature detecting means for detecting the temperature of the laser light source, input means for inputting image data, Display control means for driving the laser light source to display an image corresponding to the image data, the display control means changing the color tone of the image based on the temperature detected by the temperature detection means. Features.

The image display device has a plurality of laser light sources having different wavelengths. The temperature detecting means detects the temperature of the laser light source. The display control means drives the laser light source to display an image corresponding to the image data. Here, the display control means displays the image by changing the color tone of the displayed image based on the detected temperature. As a result, when the detected laser temperature is high, the laser can be stopped or the output can be reduced to change the color tone and continue the display, thereby suppressing the rise in the laser temperature. However, the image display can be maintained as much as possible.

In one aspect of the image display device, when the detected temperature is higher than a predetermined temperature, the display control unit stops at least one of the laser light sources and displays an image using another laser light source. Thereby, the display of an image can be maintained as much as possible while suppressing the temperature rise of the laser.

In another aspect of the image display device, each laser light source has an allowable maximum temperature indicating an upper limit temperature that can be used, and the display control unit includes the allowable maximum temperature of each laser light source, the detected temperature, The laser light source whose detection temperature is higher than the allowable maximum temperature is stopped, and an image is displayed using the laser light source whose detection temperature is lower than the allowable maximum temperature. In this aspect, even if the detection temperature exceeds the allowable maximum temperature for some laser light sources among the plurality of laser light sources, if the detection temperature is less than the maximum allowable temperature for other laser light sources, those laser light sources The display can be continued using.

In another aspect of the image display device, the display control unit reduces the output of at least one of the laser light sources below the output when the detected temperature is lower than the predetermined temperature when the detected temperature is higher than the predetermined temperature. Thereby, a display can be continued, suppressing a temperature rise.

In another aspect of the image display device, each laser light source has an operation limit temperature lower than an allowable maximum temperature, and the display control unit compares the operation limit temperature of each laser light source with the detection temperature. Then, the output of the laser light source whose detected temperature is higher than the operation limit temperature is decreased from the output when the detected temperature is lower than the operation limit temperature. In this aspect, even if the detected temperature does not exceed the allowable maximum temperature, the output of the laser light source is reduced when the detected temperature approaches the allowable maximum temperature, so that the temperature rise of the laser light source can be suppressed. As a result, the life of the laser light source can be extended.

In a preferred example in this case, the display control means sets a ratio of decreasing the output of the laser light source as the difference between the detected temperature and the operation limit temperature increases for a laser light source whose detection temperature is higher than the operation limit temperature. Enlarge. Thereby, the temperature rise of a laser light source can be suppressed more effectively.

In another preferred example, when the output of the at least one laser light source is decreased, the display control means increases the output of the other laser light source. Thereby, it can prevent that the level of the whole display image falls.

In another aspect of the above image display device, the display control unit stops the output of the at least one laser light source in an image corresponding to the image data when the output of the laser light source is stopped or decreased. Or display a message indicating the decrease. Thus, the user can know the reason why the color tone of the image has changed, and can know that the laser is at a high temperature.

In another embodiment of the present invention, an image display method executed by an image display device including at least two laser light sources each having a different output light wavelength includes a temperature detection step of detecting a temperature of the laser light source, and image data. And a display control step of displaying an image corresponding to the image data by driving the laser light source, the display control step based on the temperature detected by the temperature detection means Change the color of the image. Also by this method, it is possible to maintain image display as much as possible while suppressing the temperature rise of the laser.

In another embodiment of the present invention, an image display program executed by an image display device including at least two laser light sources each having a different wavelength of output light includes temperature detection means for detecting the temperature of the laser light source, and image data. The image display device is caused to function as input means for inputting, display control means for driving the laser light source to display an image corresponding to the image data, and the display control means is based on a temperature detected by the temperature detecting means. To change the color tone of the image. This program can also maintain image display as much as possible while suppressing the temperature rise of the laser.

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

[Image display device]
FIG. 1 shows a configuration of an image display apparatus according to an embodiment. As shown in FIG. 1, the image display device 1 includes an image signal input unit 2, a video ASIC 3, a frame memory 4, a ROM 5, a RAM 6, a laser driver ASIC 7, a MEMS control unit 8, and a laser light source unit 9. And a MEMS mirror 10.

The image signal input unit 2 receives an image signal input from the outside and outputs it to the video ASIC 3.

The video ASIC 3 is a block that controls the laser driver ASIC 7 and the MEMS control unit 8 based on the image signal input from the image signal input unit 2 and the scanning position information Sc input from the MEMS mirror 10, and is ASIC (Application Specific Integrated). Circuit). The video ASIC 3 includes a synchronization / image separation unit 31, a bit data conversion unit 32, a light emission pattern conversion unit 33, and a timing controller 34.

The synchronization / image separation unit 31 separates the image data displayed on the screen as the image display unit and the synchronization signal from the image signal input from the image signal input unit 2 and writes the image data to the frame memory 4.

The bit data conversion unit 32 reads the image data written in the frame memory 4 and converts it into bit data.

The light emission pattern conversion unit 33 converts the bit data converted by the bit data conversion unit 32 into a signal representing the light emission pattern of each laser.

The timing controller 34 controls the operation timing of the synchronization / image separation unit 31 and the bit data conversion unit 32. The timing controller 34 also controls the operation timing of the MEMS control unit 8 described later.

In the frame memory 4, the image data separated by the synchronization / image separation unit 31 is written. The ROM 5 stores a control program and data for operating the video ASIC 3. Various data are sequentially read from and written into the RAM 6 as a work memory when the video ASIC 3 operates.

The laser driver ASIC 7 is a block that generates a signal for driving a laser diode provided in a laser light source unit 9 described later, and is configured as an ASIC. The laser driver ASIC 7 includes a red laser driving circuit 71, a blue laser driving circuit 72, and a green laser driving circuit 73.

The red laser driving circuit 71 drives the red laser LD1 based on the signal output from the light emission pattern conversion unit 33. The blue laser drive circuit 72 drives the blue laser LD2 based on the signal output from the light emission pattern conversion unit 33. The green laser drive circuit 73 drives the green laser LD3 based on the signal output from the light emission pattern conversion unit 33.

The MEMS control unit 8 controls the MEMS mirror 10 based on a signal output from the timing controller 34. The MEMS control unit 8 includes a servo circuit 81 and a driver circuit 82.

The servo circuit 81 controls the operation of the MEMS mirror 10 based on a signal from the timing controller.

The driver circuit 82 amplifies the control signal of the MEMS mirror 10 output from the servo circuit 81 to a predetermined level and outputs the amplified signal.

The laser light source unit 9 emits laser light to the MEMS mirror 10 based on the drive signal output from the laser driver ASIC 7.

The MEMS mirror 10 as a scanning unit reflects the laser light emitted from the laser light source unit 9 toward the screen 11. Further, the MEMS mirror 10 moves so as to scan on the screen 11 under the control of the MEMS control unit 8 in order to display the image input to the image signal input unit 2, and the scanning position information (for example, the mirror) (Information such as angle) is output to the video ASIC 3.

Next, the detailed configuration of the laser light source unit 9 will be described. The laser light source unit 9 includes a case 91, a wavelength selective element 92, a collimator lens 93, a red laser LD1, a blue laser LD2, a green laser LD3, a monitor light receiving element (hereinafter simply referred to as “light receiving element”). 50) and the thermistor 98.

The case 91 is formed in a substantially box shape with resin or the like. In order to attach the green laser LD3, the case 91 is provided with a hole penetrating into the case 91 and a CAN attachment portion 91a having a concave cross section, and a surface perpendicular to the CAN attachment portion 91a. A hole penetrating inward is formed, and a collimator mounting portion 91b having a concave cross section is formed.

The wavelength-selective element 92 as a combining element is configured by, for example, a trichroic prism, and is provided with a reflective surface 92a and a reflective surface 92b. The reflection surface 92a transmits the laser light emitted from the red laser LD1 toward the collimator lens 93, and reflects the laser light emitted from the blue laser LD2 toward the collimator lens 93. The reflecting surface 92b transmits most of the laser light emitted from the red laser LD1 and the blue laser LD2 toward the collimator lens 93 and reflects a part thereof toward the light receiving element 50. The reflection surface 92 b reflects most of the laser light emitted from the green laser LD 3 toward the collimator lens 93 and transmits part of the laser light toward the light receiving element 50. In this way, the emitted light from each laser is superimposed and incident on the collimator lens 93 and the light receiving element 50. The wavelength selective element 92 is provided in the vicinity of the collimator mounting portion 91b in the case 91.

The collimator lens 93 emits the laser beam incident from the wavelength selective element 92 to the MEMS mirror 10 as parallel light. The collimator lens 93 is fixed to the collimator mounting portion 91b of the case 91 with a UV adhesive or the like. That is, the collimator lens 93 is provided after the synthesis element.

The red laser LD1 as a laser light source emits red laser light. The red laser LD1 is fixed at a position that is coaxial with the wavelength selective element 92 and the collimator lens 93 in the case 91 while the semiconductor laser light source is in the chip state or the chip is mounted on a submount or the like. ing.

Blue laser LD2 as a laser light source emits blue laser light. The blue laser LD2 is fixed at a position where the emitted laser light can be reflected toward the collimator lens 93 by the reflecting surface 92a while the semiconductor laser light source is in the chip state or the chip is mounted on the submount or the like. ing. The positions of the red laser LD1 and the blue laser LD2 may be switched.

The green laser LD3 as a laser light source is attached to the CAN package or attached to the frame package, and emits green laser light. The green laser LD 3 has a semiconductor laser light source chip B that generates green laser light in a CAN package, and is fixed to a CAN mounting portion 91 a of the case 91.

The light receiving element 50 receives a part of the laser light emitted from each laser light source. The light receiving element 50 is a photoelectric conversion element such as a photodetector, and supplies a detection signal Sd, which is an electrical signal corresponding to the amount of incident laser light, to the laser driver ASIC 7. Actually, at the time of power adjustment, one of red laser light, blue laser light, and green laser light is sequentially incident on the light receiving element 50, and the light receiving element 50 outputs a detection signal Sd corresponding to the amount of the laser light. To do. The laser driver ASIC 7 adjusts the power of the red laser LD1, the blue laser LD2, and the green laser LD3 according to the detection signal Sd.

For example, when the power of the red laser LD1 is adjusted, the laser driver ASIC 7 operates only the red laser driving circuit 71, supplies a driving current to the red laser LD1, and emits red laser light from the red laser LD1. A part of the red laser light is received by the light receiving element 50, and a detection signal Sd corresponding to the amount of light is fed back to the laser driver ASIC7. The laser driver ASIC 7 adjusts the drive current supplied from the red laser drive circuit 71 to the red laser LD1 so that the light amount indicated by the detection signal Sd is an appropriate light amount. In this way, power adjustment is performed. The power adjustment of the blue laser LD2 and the power adjustment of the green laser LD3 are similarly performed.

Note that it is also possible to simultaneously make red laser light, blue laser light, and green laser light incident on the light receiving element 50 and simultaneously adjust the power of each laser light.

The thermistor 98 detects the temperature of the laser light source unit 9. The thermistor 98 has a role of detecting temperatures representative of the temperatures of the red laser LD1, the blue laser LD2, and the green laser LD3 provided in the laser light source unit 9, so that the temperatures of these three lasers themselves are as high as possible. It is desirable to arrange at a position where a close temperature can be detected. The temperature detected by the thermistor 98 (hereinafter referred to as “detected temperature”) is supplied to the video ASIC 3 as a detection signal St. The video ASIC 3 performs display control described below based on the detected temperature, and changes the color tone of the displayed image.

In the above configuration, the thermistor 98 is an example of the temperature detection means of the present invention, the image signal input unit 2 is an example of the input means, and the video ASIC 3 is an example of the display control means.

[Display control]
As described above, in the video ASIC 3, the image data in the image signal input from the image signal input unit 2 is converted into bit data. For example, when the number of display bits is 8 bits, the bit data conversion unit 32 supplies bit data having gradation values of 0 to 255 to the light emission pattern conversion unit 33 for each color of RGB. The light emission pattern conversion unit 33 supplies a drive waveform corresponding to the input gradation value to each of the RGB colors to the laser drive circuits 71 to 73 of the laser driver ASIC 7 to drive the lasers LD1 to LD3 of each color to emit light.

FIG. 2 (a) shows the relationship between the laser operating current at 50 ° C., 60 ° C. and 70 ° C. and the output power. As shown in the figure, the operating current of the laser increases as the temperature rises, and when the allowable maximum temperature (60 ° C. in the example of FIG. 2A) is exceeded, the optical power is not emitted even if the current is increased. . If a current is further input in this state, the laser chip is damaged and deteriorates. For this reason, it is necessary to use the lasers LD1 to LD3 of each color at an allowable maximum temperature or less.

Normally, the lasers LD1 to LD3 of the respective colors have different temperature characteristics and different allowable maximum temperatures. Hereinafter, the allowable maximum temperature Tr ° C of the red laser LD1, the allowable maximum temperature Tb ° C of the blue laser LD2, and the allowable maximum temperature Tg ° C of the green laser LD3,
Tr <Tg <Tb
Suppose there is a relationship. In this embodiment, when the detected temperature exceeds the allowable maximum temperature, the laser is not used, and only the remaining laser is used to display the display image after changing the color tone.

(First embodiment)
The first embodiment will be described below. Specifically, when the temperature Td detected by the thermistor 98 is not more than the minimum value Tr of the maximum allowable temperatures of the three lasers LD1 to LD3 (ie, Td <Tr), all the three lasers LD1 to LD3 can be used. Therefore, the image display device can display colors in the triangle RGB formed by the three vertices R, G, and B in the chromaticity diagram shown in FIG.

When the detected temperature Td is higher than the allowable maximum temperature Tr of the red laser LD1 and lower than the allowable maximum temperature Tg of the green laser LD3 (that is, Tr <Td <tg), the red laser LD1 is not used. In this case, the image display apparatus performs display using only the color on the line segment GB in the chromaticity diagram shown in FIG.

When the detection temperature Td is higher than the allowable maximum temperature Tg of the green laser LD3 and lower than the allowable maximum temperature Tb of the blue laser (that is, Tg <Td <Tb), the red laser LD1 and the green laser LD3 are not used. In this case, the image display apparatus performs display using only blue.

Further, when the detected temperature Td is higher than the allowable maximum temperature Tb of the blue laser (that is, Tb <Td), the display is stopped because all the laser LDs exceed the allowable maximum temperature.

3A to 3C show examples of display images when the display control of this embodiment is performed. FIGS. 3A to 3C are display image examples of the navigation device, and the display contents are the same. Since the display color differs depending on the temperature, the display color is shown in parentheses.

When the detected temperature Td <Tr, all the colors in the triangle RGB in FIG. 2B can be displayed. As shown in FIG. 3A, the image is displayed in various colors such as red, yellow, blue, and purple. Is displayed. In addition, when Tr <Td <Tg, only the colors on the line segment GB shown in FIG. 2B can be used. Therefore, as shown in FIG. 3B, the image is displayed only with blue, green, and their intermediate colors. Is displayed. When Tg <Td <Tb, as shown in FIG. 3C, the image is displayed only in blue.

Note that, as shown in FIGS. 3B and 3C, when a part of the laser LD is stopped, it is desirable to display a message 42 indicating that in the display image. Accordingly, when the display color is limited by the temperature and the color tone of the display image changes, it is possible to prevent the user from misunderstanding that the image display apparatus is defective.

FIG. 4 is a flowchart of the display control process according to the first embodiment. This processing is executed mainly by the video ASIC 3 controlling the laser driver ASIC 7 and the like. Further, this process is repeatedly executed at predetermined time intervals.

First, the video ASIC 3 acquires the detection temperature Td based on the detection signal St from the thermistor 98 (step S11). Then, the video ASIC 3 determines whether or not the detected temperature Td is higher than the lowest allowable maximum temperature Tr among the allowable maximum temperatures of the three lasers LD (step S12). Display is performed using the lasers LD1 to LD3 (step S13).

On the other hand, when the detected temperature Td is higher than the allowable maximum temperature Tr (step S12; Yes), the video ASIC 3 determines whether the detected temperature Td is higher than the allowable maximum temperature Tg (step S14). If not high (step S14; No), the video ASIC 3 performs display using the green laser LD3 and the blue laser LD2 (step S15).

On the other hand, when the detected temperature Td is higher than the allowable maximum temperature Tg (step S14; Yes), the video ASIC 3 determines whether the detected temperature Td is higher than the allowable maximum temperature Tb (step S16). If not high (step S16; No), the video ASIC 3 performs display using only blue (step S17). On the other hand, when the detected temperature is higher than the allowable maximum temperature Tg (step S16; Yes), the video ASIC 3 stops all the lasers LD1 to LD3 and stops the display (step S18).

As described above, in the first embodiment, based on the temperature detected by the thermistor 98, the laser exceeding the allowable maximum temperature is stopped, and only the laser that does not exceed the allowable maximum temperature is used to change the color tone for display. . Therefore, even when the detected temperature exceeds the allowable maximum temperature of some lasers, the color of the display image changes, but the display can be continued. Therefore, even when the laser becomes high temperature, it is possible to continue displaying information as much as possible while protecting the laser.

This also has the effect of shortening the startup time of the apparatus. In a situation where the device is hot, such as during the summer, in a normal device equipped with cooling means, if all lasers are not cooled until the temperature falls below the lowest allowable maximum temperature among a plurality of lasers, the device is started. I can't. For example, in the above-described three-color laser example, the apparatus is not started unless the laser is cooled below the lowest allowable maximum temperature Tr of the three lasers. In contrast, in the first embodiment, when the laser is cooled to the maximum allowable maximum temperature Tb or less, display can be started using only blue. Therefore, it is possible to shorten the time until the apparatus is activated and display information to the user quickly.

(Second embodiment)
Next, a second embodiment will be described. Also in the second embodiment, display is performed without using a laser whose allowable maximum temperature has been exceeded. However, in the second embodiment, even if the detected temperature Td does not exceed the allowable maximum temperature, if the detected temperature Td approaches the allowable maximum temperature, the output of the laser is decreased.

As shown in FIG. 5A, when the temperature of the semiconductor laser rises, the time required to reach the same cumulative failure rate is shortened. That is, the lifetime is shortened as the temperature increases. Use of the laser with the shortest lifetime among the RGB three-color lasers at a lower temperature leads to extending the lifetime of the entire apparatus. Therefore, in the second embodiment, in order to use the laser with the shortest lifetime for a long time, when the temperature rises, the output of the laser is lowered to lower the temperature of the light emitting unit, and the display function is maintained. Extend life.

Now, the allowable maximum temperature Tr of the red laser LD1 is set to 60 ° C., and the operation limit temperature Trx is set to 40 ° C. The “operation limit temperature” is a temperature that does not reach the maximum allowable temperature but approaches it, so that the output level is lowered. Therefore, when the detected temperature Td reaches the operation limit temperature Trx, the output of the red laser LD1 is decreased, and when the detected temperature Td reaches the allowable maximum temperature Tr, the red laser LD1 is stopped. Similarly, the allowable maximum temperature Tg of the green laser LD3 is 80 ° C., and the operation limit temperature Tgx is 60 ° C. Further, the allowable maximum temperature Tb of the blue laser LD2 is set to 85 ° C.

An example of a specific control method is shown in FIG. First, when the detected temperature Td is equal to or lower than the operation limit temperature Trx of the red laser LD1, the image display device performs display using the lasers LD1 to LD3 of three colors without limitation. Therefore, the image to be displayed in red is displayed in red corresponding to the point R in the chromaticity diagram of FIG. In this case, the display can be performed using the colors in the triangle RGB in FIG.

When the detected temperature Td becomes 40 to 45 ° C., the output of the red laser LD1 is lowered, and an image to be displayed in red corresponding to the point R is displayed using the color of the point R1. In this case, the displayable colors are limited within the triangle formed by the points R1, G, and B in FIG.

Similarly, when the detected temperature Td becomes 45 to 50 ° C., an image that should be displayed in red corresponding to the point R is displayed in the color of the point R2, and when the detected temperature Td becomes 50 to 55 ° C. The image that should originally be displayed in red corresponding to the point R is displayed in the color of the point R3. When the detected temperature Td reaches the allowable maximum temperature Tr (= 60 ° C.) of the red laser LD1, the red laser LD1 is stopped and is not used, so that only the color on the line segment GB is used for display. It will be.

Next, when the detected temperature reaches 60 to 65 ° C., the output of the green laser LD3 is reduced, and an image to be displayed in green corresponding to the point G is displayed using the color of the point G1. In this case, the displayable color is limited to the color on the line segment G1B formed by the point G1 and the point B.

Similarly, when the detected temperature Td is 65 to 70 ° C., an image that should be displayed in green corresponding to the point G is displayed in the color of the point G2, and when the detected temperature Td is 70 to 75 ° C., An image that should originally be displayed in green corresponding to the position of the point G is displayed in the color of point G3, and when the detected temperature Td reaches 75 to 80 ° C., an image that should be displayed in green that originally corresponds to the position of the point G Is displayed in the color of point G4. When the detected temperature Td reaches the allowable maximum temperature Tg (= 80 ° C.) of the green laser LD3, the green laser LD3 is stopped and is not used, so that display is performed using only blue.

Note that when the detected temperature Td exceeds the operation limit temperature, the ratio of decreasing the laser output may be constant, and the difference between the detection temperature and the operation limit temperature is large, that is, the amount exceeding the operation limit temperature. The reduction rate of the laser output may be increased.

Fig. 6 (a) shows another example of the control method. In this example, when the detected temperature Td exceeds the operation limit temperature Trx (= 40 ° C.) of the red laser LD1, the output of the red laser LD1 is decreased and the display color is shifted in the blue direction on the chromaticity diagram. Specifically, when the detected temperature Td is 40 to 45 ° C., the image originally displayed in the color of the point R is displayed in the color of the point R11, and when the detected temperature Td is 45 to 50 ° C., the color of the original point R is displayed. The image to be displayed is displayed in the color of the point R12. When the detected temperature Td is 50 to 55 ° C., the image originally displayed in the color of the point R is displayed in the color of the point R13. When the detected temperature Td reaches the allowable maximum temperature Tr (= 60 ° C.), the red laser LD1 is stopped and display is performed in the color on the line segment GB.

FIG. 6B shows still another example of the control method. In this example, when the detected temperature Td exceeds the operation limit temperature Trx (= 40 ° C.) of the red laser LD1, the output of the red laser LD1 is decreased, and the display color is shown in FIG. 8B on the chromaticity diagram. This is an example of shifting in the direction indicated by the arrow. Specifically, when the detected temperature Td is 40 to 45 ° C., the image originally displayed in the color of the point R is displayed in the color of the point P1, and when the detected temperature Td is 45 to 50 ° C., the color of the original point R is displayed. The image to be displayed is displayed in the color of the point P2, and when the detected temperature Td is 50 to 55 ° C., the image originally displayed in the color of the point R is displayed in the color of the point P3. When the detected temperature Td reaches the allowable maximum temperature Tr (= 60 ° C.), the red laser LD1 is stopped and display is performed in the color on the line segment GB.

It should be noted that the display color shift as described above can actually be realized by using a conversion table in which colors in an image signal are associated with gradation values of RGB colors. Specifically, a plurality of conversion tables having different temperature ranges are prepared in advance, such as a table when the detected temperature Td is 40 ° C. or less, a conversion table when the temperature is 40 to 45 ° C., and a conversion table when the temperature is 45 to 50 ° C. Keep it. For example, the red color corresponding to the point R has a gradation value of R set to 255 in the conversion table when the detection temperature Td is 40 ° C. or lower, and R of the conversion table when the detection temperature Td is 40 to 45 ° C. The gradation value is set to 240. In this way, the image processing apparatus may determine the gradation value of each RGB color by referring to the conversion table of the corresponding temperature range according to the detected temperature Td, and drive the laser of each color based on that.

As described above, in the second embodiment, even if the detected temperature Td does not reach the operation allowable temperature, when the operation limit temperature is reached, the output of the laser LD is decreased to further increase the temperature. The laser is used at a temperature lower than the allowable operating temperature as much as possible. By extending the lifetime of the laser in this way, the lifetime of the entire apparatus can be extended.

In the second embodiment, when the detected temperature Td reaches the operation limit temperature, the output of the laser is decreased. However, in order to compensate for the decrease, the outputs of lasers of other colors may be increased. . For example, when the detection temperature Td exceeds the operation limit temperature of the red laser LD1, the output of the red laser LD1 is decreased, and the green laser LD3 and / or the blue laser LD2 whose allowable maximum temperature is higher than that of the red laser LD1. The output may be increased to prevent the display image level from being lowered.

Also in the second embodiment, when a part of the laser LD is stopped or its output is reduced, it is desirable to display a message indicating that in the display image. Thereby, it can be known that the laser is at a high temperature and that the display color is limited by the temperature and the color tone of the display image has changed.

FIG. 7 is a flowchart of the display control process according to the second embodiment. This process is also executed mainly by the video ASIC 3 controlling the laser driver ASIC 7 and the like. Further, this process is repeatedly executed at predetermined time intervals.

First, the video ASIC 3 acquires the detection temperature Td based on the detection signal St from the thermistor 98 (step S21). Then, the video ASIC 3 determines whether or not the detected temperature Td is higher than the operation limit temperature Trx of the red laser LD1 that is the lowest of the three laser LD operation limit temperatures (step S22). The display is performed using the three color lasers LD1 to LD3 (step S23).

On the other hand, when the detected temperature Td is higher than the operation limit temperature Trx (step S22; Yes), the video ASIC 3 determines whether or not the detected temperature Td is higher than the allowable maximum temperature Tr (step S24). If not high (step S24; No), the video ASIC 3 performs display using the three-color lasers LD1 to LD3 while reducing the output of the red laser LD1 as described above (step S25).

When the detected temperature Td is higher than the allowable maximum temperature Tr (step S24; Yes), the video ASIC 3 determines whether the detected temperature is higher than the operation limit temperature Tgx of the green laser LD3 (step S26). If not high (step S26; No), the video ASIC 3 performs display using the green laser LD3 and the blue laser LD2 (step S27). On the other hand, when the detected temperature Td is higher than the operation limit temperature Tgx (step S26; Yes), the video ASIC 3 determines whether the detected temperature Td is higher than the allowable maximum temperature Tg of the green laser LD1 (step S28). If not high (step S28; No), the video ASIC 3 performs display using the green laser LD3 and the blue laser LD2 while reducing the output of the green laser LD3 (step S29).

When the detected temperature Td is higher than the allowable maximum temperature Tg (step S28; Yes), the video ASIC 3 determines whether the detected temperature Td is higher than the allowable maximum temperature Tb of the blue laser LD2 (step S30). If not high (step S30; No), the video ASIC 3 displays using only the blue laser LD2 (step S31). On the other hand, when the detected temperature Td is higher than the allowable maximum temperature Tb (step S30; Yes), the video ASIC 3 stops all the lasers LD1 to LD3 and stops displaying (step S32).

As described above, in the second embodiment, in addition to the effects of the first embodiment, when the detected temperature approaches the allowable maximum temperature, the laser output is reduced to suppress the temperature rise, so that each laser is more It can be used in a low temperature state, and the life can be extended.

The present invention can be used for video equipment using an RGB laser, such as a laser projector, a head-up display, and a head-mounted display.

1 Image display device 3 Video ASIC
7 Laser driver ASIC
8 MEMS control unit 9 Laser light source unit 50 Light receiving element 98 Thermistor

Claims

At least two laser light sources each having a different output light wavelength;
Temperature detecting means for detecting the temperature of the laser light source;
Input means for inputting image data;
Display control means for driving the laser light source to display an image corresponding to the image data,
The image display apparatus, wherein the display control means changes a color tone of the image based on a temperature detected by the temperature detection means.
2. The image according to claim 1, wherein when the detected temperature is higher than a predetermined temperature, the display control unit stops at least one of the laser light sources and displays an image using another laser light source. Display device.
Each laser light source has an allowable maximum temperature indicating an upper limit temperature that can be used,
The display control means compares the maximum allowable temperature of each laser light source with the detection temperature, stops the laser light source whose detection temperature is higher than the maximum allowable temperature, and uses the laser light source whose detection temperature is lower than the maximum allowable temperature. The image display device according to claim 2, wherein the image is displayed.
2. The image display according to claim 1, wherein when the detected temperature is higher than a predetermined temperature, the display control unit reduces an output of at least one of the laser light sources to be lower than an output when the detected temperature is lower than the predetermined temperature. apparatus.
Each laser light source has an operation limit temperature lower than the maximum allowable temperature,
The display control means compares the operation limit temperature of each laser light source with the detection temperature, and reduces the output of the laser light source whose detection temperature is higher than the operation limit temperature than the output when the detection temperature is lower than the operation limit temperature. The image display device according to claim 3.
The display control means increases the ratio of decreasing the output of the laser light source as the difference between the detected temperature and the operation restricted temperature is larger for a laser light source whose detected temperature is higher than the operation restricted temperature. Item 6. The image display device according to Item 5.
The image display device according to claim 4, wherein the display control means increases the output of the other laser light source when the output of the at least one laser light source is decreased.
When the output of the at least one laser light source is stopped or reduced, the display control means displays a message indicating the stop or reduction in an image corresponding to the image data. The image display device according to claim 2 or 4.
An image display method executed by an image display device including at least two laser light sources each having a different wavelength of output light,
A temperature detecting step for detecting the temperature of the laser light source;
An input process for inputting image data;
A display control step of driving the laser light source to display an image corresponding to the image data,
The display control step of changing the color tone of the image based on the temperature detected by the temperature detecting means.
An image display program executed by an image display device including at least two laser light sources each having a different wavelength of output light,
Temperature detecting means for detecting the temperature of the laser light source;
Input means for inputting image data;
Causing the image display device to function as display control means for driving the laser light source to display an image corresponding to the image data;
The image display program characterized in that the display control means changes the color tone of the image based on the temperature detected by the temperature detection means.