JP2015065392A - Video display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a video display device that has the extended life of a laser light source.SOLUTION: A video display device 101 is a device that allows an observer ST to observe a video VM of display images, and includes a laser light source LD that emits laser beams Lc, a laser light source driving unit 14 that supplies power to the laser light source LD, light control means M15 for controlling the intensity of the laser beams Lc, and an image creating unit 11 that creates desired display images from the laser beams Lc, where the light control means M15 includes a light intensity detection unit 35 that detects the intensity of light, a control unit 55 that controls the output of the laser light source driving unit 14 on the basis of a result of the detection by the light intensity detection unit 35, and a current value detection unit 75 that detects the current value output from the laser light source driving unit 14; when the current value output from the laser light source driving unit 14 becomes larger than a predetermined limit current value stored in advance in a current storage unit K5, the control unit 55 outputs a current equal to or smaller than the limit current value to control the current value.

Description

  The present invention relates to an image display apparatus using coherent light.

  In recent years, laser light has been applied in a wide range of fields such as optical recording devices, measuring instruments, printers, medical equipment, and office equipment, taking advantage of features such as small size, high efficiency, and high directivity. In particular, recently, a so-called laser projector, which is an image display device that displays an image by irradiating a projection surface such as a screen or a wall with laser light, has been generally known. Further, as a video display device other than a laser projector, it has been applied to a three-dimensional display, a head mounted display (HMD), a head-up display (HUD), and the like.

  As a laser projector (video display device) described above, as shown in FIG. 6, a multi-beam scanning device 900 is proposed in Patent Document 1. FIG. 6 is a top view for explaining a conventional multi-beam scanning apparatus 900. A multi-beam scanning apparatus 900 shown in FIG. 6 includes a light source unit 910 having red, green, and blue laser light sources (LDR, LDG, LDB) and a horizontal deflection polygon mirror 931. The horizontal scanning direction deflection polygon motor unit 930, the fθ lens 950, and the vertical scanning direction deflection polygon motor unit 960 having the vertical deflection polygon mirror 961 are configured.

  Then, as shown in FIG. 6, laser light emitted from a CAN (CAN) package type red laser light source LDR, green laser light source LDG, and blue laser light source LDB is combined by a prism unit 912 and then a horizontal deflection polygon. The incident laser beam is incident on the reflecting surface 931a of the mirror 931, and is emitted from the reflecting surface 931a so as to be scanned in the horizontal direction (X direction shown in FIG. 6) at regular intervals. Next, the laser light emitted from the reflecting surface 931a passes through the fθ lens 950 and then enters the reflecting surface 961a of the vertical deflection polygon mirror 961, and the incident laser light is scanned in the vertical direction at a constant cycle (FIG. 6). Is emitted from the reflecting surface 961a so as to be performed in the direction of penetrating the paper surface shown in FIG. The laser beam scanned horizontally and vertically and emitted from the reflecting surface 961a is displayed as a display image on a screen 990 arranged so as to block this scanning area.

JP 2004-219480 A

  In the multi-beam scanning device 900 (video display device) using such a laser light source (LDR, LDG, LDB), a current passed through the laser light source (LDR, LDG, LDB) for an observer who visually recognizes a display image. By adjusting the value, the brightness of the display image is kept constant.

  However, as the laser light source (LDR, LDG, LDB) deteriorates, the luminance gradually decreases even at the same current value. Therefore, in order to keep the luminance constant, the flowing current value is increased. FIG. 5 is a diagram for explaining a problem in the conventional video display device, and is a graph showing a relationship between the light emission time of the laser light source and the current value of the laser light source when the luminance of the display image is kept constant. is there. As shown in FIG. 5, after initial deterioration was observed and the current value was increased (AA area shown in the figure), the current value was gradually increased almost constantly with the elapsed time (BB area shown in the figure). ). Furthermore, as the current value is increased, the deterioration of the laser light source is accelerated (CC region shown in the figure), so that not only the life of the laser light source is shortened but also suddenly no light is emitted at a certain point (in the figure). There was a problem of E point).

  The present invention solves the above-described problems, and an object of the present invention is to provide an image display device that extends the life of a laser light source.

  In order to solve this problem, an image display apparatus according to the present invention includes a laser light source that emits laser light, a laser light source driving unit that supplies power to the laser light source, and light control that controls the light intensity of the laser light. Means and an image generation unit for generating a desired display image from the laser light, and an image display device for allowing an observer to observe the image of the display image, wherein the light control means A light intensity detection unit to detect, a control unit to control the output of the laser light source driving unit based on a detection result of the light intensity detection unit, and a current value detection to detect a current value output from the laser light source driving unit And when the current value becomes larger than a predetermined limit current value previously stored in the current storage unit, the control unit outputs and controls a current equal to or less than the limit current value. It is characterized by that.

  According to this, in the video display device of the present invention, even when the current flowing to the laser light source must be increased as the laser light source deteriorates, a current exceeding the limit current value can flow constantly to the laser light source. Absent. This can prevent the laser light source from being acceleratedly deteriorated by increasing the current value, and can extend the life of the laser light source.

  The image display apparatus of the present invention is characterized in that a plurality of the laser light sources are provided and a plurality of the light control means are provided corresponding to the plurality of laser light sources.

  According to this, since a plurality of laser light sources are provided, it is possible to enrich the expression of the image visually recognized by the observer. Further, since a plurality of light control means are provided corresponding to a plurality of laser light sources, even if the display image area is different in different colors, the output to each laser light source is output by each light control means. The light intensity (luminance) of each image to be adjusted and displayed can be maintained at a desired value.

  In the video display device of the present invention, the image generation unit includes a holographic optical element that diffracts the laser light to generate video light, and an optical member that guides the video light from the holographic optical element. The light intensity detection unit detects the light intensity of the image light, and the light control unit controls an output of the laser light source driving unit based on a detection result of the light intensity detection unit. It is said.

  According to this, the output to the laser light source can be matched in accordance with the displayed display image, and the brightness of the display image can be adjusted as needed. For this reason, the light intensity (luminance) can be accurately adjusted to the target light intensity (luminance), and the light utilization efficiency can be improved. As a result, deterioration of the laser light source can be further prevented, and the life of the video display device can be further extended.

  In the video display device of the present invention, even when the current flowing through the laser light source must be increased as the laser light source deteriorates, the current exceeding the limit current value does not constantly flow through the laser light source. This can prevent the laser light source from being acceleratedly deteriorated by increasing the current value, and can extend the life of the laser light source.

It is a block diagram explaining the video display apparatus of 1st Embodiment of this invention. It is a figure explaining the control method in the video display device of a 1st embodiment of the present invention. It is a figure explaining the control method in the video display apparatus of 1st Embodiment of this invention, Comprising: It is an enlarged view of the P1 part shown in FIG. FIG. 4A is a diagram illustrating a modification of the video display device according to the first embodiment of the present invention, FIG. 4A is a diagram of Modification 1 compared with FIG. 3, and FIG. It is a figure of the modification 2 compared with FIG. It is a figure explaining the subject in the conventional video display apparatus, Comprising: It is the graph which showed the relationship between the light emission time of a laser light source, and the electric current value of a laser light source when the brightness | luminance of a display image is kept constant. It is a top view explaining the multi-beam scanning apparatus 900 of a prior art example.

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

[First Embodiment]
FIG. 1 is a configuration diagram illustrating a video display apparatus 101 according to the first embodiment of the present invention.

  As shown in FIG. 1, the video display device 101 according to the first embodiment of the present invention is mounted on a vehicle and used as a head-up display (HUD).

  In addition, as shown in FIG. 1, the video display apparatus 101 according to the first embodiment of the present invention includes a laser light source LD that emits laser light Lc, a laser light source driver 14 that supplies power to the laser light source LD, and a laser. The image generation unit 11 generates a desired display image from the light Lc, and a light control unit M15 that controls the light intensity of the laser light Lc. Then, the output to the laser light source LD is adjusted by the light control means M15, and the observer ST is made to observe (make visible) the image VM by the adjusted image light Lf through the windshield FG.

  As shown in FIG. 1, in the first embodiment of the present invention, the laser light source LD of the video display device 101 is a laser light source LD (RLD, RLD, three colors) of red (Red), green (Green), and blue (Blue). GLD, BLD). Although not shown in detail, three types of semiconductor laser elements are used to emit red, green and blue light. Thereby, since the semiconductor laser element is used, the laser light Lc having high coherence (coherent) can be emitted from the laser light source LD. In addition, since a plurality of laser light sources LD are provided in this way (three in the first embodiment of the present invention, three), the image VM visually recognized by the observer ST can have a plurality of colors. The expression of the video VM can be enriched.

  Further, as the semiconductor laser element, for example, an element that emits light having a wavelength of 642 nm is preferably used in the case of red, and an element that emits light having a wavelength of 515 nm is preferably used in the case of green. In the case of blue, an element that emits light having a wavelength of 445 nm or the like is preferably used.

  The laser light source drive unit 14 of the video display device 101 is a drive circuit in which an operational amplifier is incorporated. As shown in FIG. 1, each laser light source LD (RLD, GLD, BLD) is connected to each laser light source LD. The laser light source driving unit 14R, the laser light source driving unit 14G, and the laser light source driving unit 14B are connected to drive the respective laser light sources LD (RLD, GLD, BLD).

  The image generation unit 11 of the video display device 101 includes a holographic optical element 41 that diffracts the laser light Lc into the video light Lf, and an optical member OP that guides the video light Lf from the holographic optical element 41. Is done.

  The holographic optical element 41 has a function of diffracting the laser light Lc from the laser light source LD into the image light Lf. Specifically, in the first embodiment of the present invention, phase modulation LCOS (Liquid crystal on silicon) is used, and the “hologram pattern” written in the phase modulation LCOS is irradiated with coherent light. As a result, diffracted light is generated and emitted as image light Lf, which is coherent light, through the Fourier lens FL1 shown in FIG. The “hologram pattern” records the intensity and phase of light.

  Further, as shown in FIG. 1, an LCOS driver 51 is connected to the holographic optical element 41. The LCOS driver 51 converts the “hologram pattern” created by the central processing unit 71 into a phase modulation type LCOS. In addition, it has a function of writing at any time. In the first embodiment of the present invention, since the desired display image is generated using the holographic optical element 41, the output to the laser light source LD can be adjusted for each display image of the displayed video VM. This makes it possible to finely adjust the output of the laser light source driving unit 14. That is, when the display area of the display image is different, the value of the current passed through the laser light source LD can be set finely in proportion to the display area of the display image. Thereby, the light intensity (luminance) can be accurately adjusted to the target light intensity (luminance), and the quality of the video VM visually recognized by the observer ST can be improved. Furthermore, since the output of the laser light source driving unit 14 can be finely adjusted, the light utilization efficiency can be improved.

  The optical member OP is mainly composed of an optical component that guides the image light Lf from the holographic optical element 41. In the first embodiment of the present invention, as shown in FIG. 22), an optical lens 32 that collects or collimates the light, a slitter 52 that defines the display range of the display screen, and a diffuser 13 that diffuses the video light Lf that is coherent light. In addition, an optical lens 42 that condenses or collimates the laser light Lc from the laser light source LD is also provided.

  The slitter 52 passes most of the irradiation range of the video light Lf, and the range corresponding to the video light Lf that has passed through is the display range of the video VM (see FIG. 1) visually recognized by the observer ST, that is, It becomes a display image.

  As shown in FIG. 1, the diffuser 13 is disposed on the rear side of the optical path of the slitter 52 and diffuses the transmitted video light Lf. The diffuser 13 is connected to a drive unit 13d that drives the diffuser 13, and rotates the diffuser 13. Thereby, the directivity of the image light Lf which is coherent light is reduced. Thereby, the speckle pattern resulting from coherent light can be reduced, and the quality of the video VM visually recognized by the observer ST can be improved. The speckle pattern referred to here means that when light having high coherence is scattered on the irradiated object, the scattered light scattered at each part on the irradiated object interferes with each other. This refers to the fine interference fringes that occur. In the first embodiment of the present invention, the diffuser 13 is rotated. However, the present invention is not limited to this. For example, the diffuser 13 may be vibrated and moved.

  The plane mirrors (12, 22), the optical lens 32, and the optical lens 42 use commonly used optical components and do not have special specifications. In addition, in order to prevent the bad influence of daylight as an optical member OP, various filters may be used and arranged in the middle of the optical path, or a curved mirror may be used instead of the flat mirrors (12, 22). . Further, the present invention is not limited to the combination of the optical members OP shown in FIG.

  As shown in FIG. 1, the light control means M15 of the video display device 101 controls the output of the laser light source driving unit 14 based on the detection result of the light intensity detecting unit 35 and the light intensity detecting unit 35. And a current value detection unit 75 that detects a current value output from the laser light source driving unit 14.

  The light intensity detector 35 of the light control means M15 detects the light intensity of the image light Lf, which is laser light, and is arranged in the vicinity of the slitter 52 as shown in FIG. 1, and includes three laser light sources RLD, Corresponding to the laser light source GLD and the laser light source BLD, three light intensity detectors 35R, a light intensity detector 35G, and a light intensity detector 35B are provided. The light intensity is detected separately for each color of red (Red), green (Green), and blue (Blue) with respect to the video light Lf irradiated to each light intensity detector 35. As the light intensity detection unit 35, a photodiode (PD) is suitably used.

  As shown in FIG. 1, the control unit 55 of the light control means M15 includes output control units 15 (15R, 15G, 15B) provided corresponding to the three laser light sources LD (RLD, GLD, BLD), respectively. The central control unit C5 that controls the output control unit 15 and the current storage unit K5 that is connected to the central control unit C5 and stores a predetermined limit current value in advance are configured. The central control unit C5 of the control unit 55 is connected to the light intensity detection unit 35 (35R, 35G, 35B). Based on the detection result of the light intensity detection unit 35, the control unit 55 (15R, 15G, 15B) is controlled to control the output of the laser light source drive unit 14 (14R, 14G, 14B). The central control unit C5 is configured using an integrated circuit (IC).

  The output control unit 15 (15R, 15G, 15B) is provided corresponding to each of the three laser light sources LD (RLD, GLD, BLD), and controls the current flowing through the laser light source LD. . The current storage unit K5 is for storing a predetermined limit current value. For example, a memory card is used, and the predetermined limit current value can be freely rewritten. In the first embodiment of the present invention, an external storage device such as a memory card is used. However, the function of the current storage unit K5 may be provided in an integrated circuit (IC).

  Further, as shown in FIG. 1, a current value detector 75 (75R, 75G, 75B) corresponding to three laser light sources LD (RLD, GLD, BLD) is also connected to the central controller C5 of the controller 55. Has been. In addition to the function of adjusting the output of the laser light source driving unit 14 (14R, 14G, 14B) based on the detection result of the light intensity detection unit 35, the control unit 55 is adapted to the temperature change due to the heat generation of the laser light source LD. It also has a function to adjust the output change of the accompanying laser light source LD.

  As shown in FIG. 1, the current value detection unit 75 of the light control means M15 is connected to the central control unit C5 of the control unit 55 and corresponds to three laser light sources LD (RLD, GLD, BLD). It is connected to the laser light source drive unit 14 (14R, 14G, 14B). And the electric current value output from the laser light source drive part 14 is detected.

  In the video display device 101 configured as described above, the light control means M15 adjusts the output to the laser light source LD, and the brightness of the displayed video VM with respect to the change in the display image of the displayed video VM. Is kept constant so that the viewer ST can comfortably observe the video VM. In particular, in the video display apparatus 101 according to the first embodiment of the present invention, the control unit 55 of the light control unit M15 controls the currents that flow through the three laser light sources LD (RLD, GLD, BLD), and the three lasers. The lifetime of the light source LD (RLD, GLD, BLD) is extended.

  Means for extending the lifetime will be described with reference to FIGS. FIG. 2 is a diagram illustrating a control method in the video display apparatus 101 according to the first embodiment of the present invention. The horizontal axis in FIG. 2 indicates the light emission time of the laser light source LD, the vertical axis of the solid line shown in the figure indicates the current value of the laser light source LD, and the vertical axis of the broken line in the figure indicates the light intensity of the laser light source LD. Indicates the target value. FIG. 3 is a diagram for explaining a control method in the video display apparatus 101 according to the first embodiment of the present invention, and is an enlarged view of a portion P1 shown in FIG. 2 and 3 are diagrams for explaining three types of laser light sources LD (RLD, GLD, BLD), and in the case of each of the laser light sources LD, only the flowing current value is different.

  The control unit 55 of the light control means M15 has an initial deterioration of the laser light source LD after the laser light source LD first emits light. As shown in FIG. 2, as the light emission time of the laser light source LD elapses, the laser light source LD In order to keep the light intensity constant, the current flowing through the laser light source LD is gradually increased.

  Thereafter, as the emission time of the laser light source LD elapses, as shown in FIGS. 2 and 3, a predetermined limit current value R1 (shown in FIGS. 2 and 3) previously stored in the current storage unit K5 is obtained. Control is performed so as to keep the light intensity of the laser light source LD constant by flowing a current exceeding the above value. At this time, it is often seen that the predetermined limit current value R1 is repeatedly exceeded or not exceeded depending on the light emission state of the laser light source LD. In the example of FIG. 3, the predetermined limit current value R1 is exceeded three times. The predetermined limit current value R1 may be a constant value determined according to the type of the laser light source LD and stored in the current storage unit K5, or a ratio with respect to the initial current value (for example, an initial value) For each laser light source LD to be used, the value may be stored in the current storage unit K5. Further, whether or not the predetermined limit current value R1 has been exceeded or not exceeded is determined by comparison with the current value detected by the current value detection unit 75.

  Next, when the control unit 55 exceeds the predetermined limit current value R1 a plurality of times (three times in the example shown in FIG. 3), the control unit 55 decreases the target value of the light intensity of the laser light source LD, and supplies the current flowing through the laser light source LD. I'm trying to lower it significantly. That is, control is performed by outputting a current equal to or less than the limit current value R1 from the laser light source driving unit 14. In the first embodiment of the present invention, when the predetermined limit current value R1 is exceeded a plurality of times, the current flowing to the laser light source LD is greatly reduced. Therefore, the predetermined limit current value R1 is temporarily set for some reason. It is possible to eliminate the case of exceeding.

  Next, the control unit 55 gradually increases again the current flowing through the laser light source LD as the light emission time of the laser light source LD elapses so that the newly set target value of the light intensity of the laser light source LD is obtained.

  Thereafter, when a certain time has elapsed, as shown in FIG. 2, a current exceeding a predetermined limit current value R1 previously stored in the current storage unit K5 is again flowed to make the light intensity of the laser light source LD constant. Control to keep is performed (P2 shown in FIG. 2). Then, when the predetermined limit current value R1 is exceeded a plurality of times, the control unit 55 further lowers the target value of the light intensity of the laser light source LD so as to greatly reduce the current flowing through the laser light source LD. Thereafter, the control unit 55 repeatedly performs this control (P3 and P4 shown in FIG. 2). If the method of gradually reducing the target value of the light intensity of the laser light source LD is taken in this way, the brightness of the video VM is felt to the observer ST to some extent (for example, a 50% decrease in light intensity). There is no problem in actual use.

  With the control as described above, even when the current flowing through the laser light source LD must be increased due to the deterioration of the laser light source LD, a current equal to or greater than the limiting current value R1 does not constantly flow through the laser light source LD. Thus, it is possible to prevent the laser light source LD from being acceleratedly deteriorated by increasing the current value, thereby extending the life of the laser light source LD.

  The effects of the video display device 101 according to the first embodiment of the present invention configured as described above will be described below.

  The video display device 101 according to the first embodiment of the present invention has a control unit when the current value detected by the current value detection unit 75 becomes larger than a predetermined limit current value R1 stored in the current storage unit K5 in advance. 55 controls the laser light source LD (RLD, GLD, BLD) by outputting a current equal to or less than the limit current value R1, so even when the current flowing through the laser light source LD must be increased as the laser light source LD deteriorates. The current exceeding the limit current value R1 does not constantly flow through the laser light source LD. Thus, it is possible to prevent the laser light source LD from being acceleratedly deteriorated by increasing the current value, thereby extending the life of the laser light source LD.

  Further, since a plurality of laser light sources LD are provided, the expression of the video VM visually recognized by the observer ST can be enriched. Further, since a plurality of light control means M15 are provided corresponding to a plurality of laser light sources LD, even if the display image area is different in different colors, each laser light source LD is provided by each light control means M15. The light intensity (luminance) of each displayed video VM can be held at a desired value.

  Further, the light intensity detection unit 35 detects the light intensity of the image light Lf from the holographic optical element 41, and the light control means M15 controls the output of the laser light source driving unit 14 based on the detection result. Corresponding to the displayed image, the output to the laser light source LD can be adjusted, and the brightness of the displayed image can be adjusted as needed. For this reason, the light intensity (luminance) can be accurately adjusted to the target light intensity (luminance), and the light utilization efficiency can be improved. As a result, the deterioration of the laser light source LD can be further prevented, and the life of the video display device 101 can be further extended.

  In addition, this invention is not limited to the said embodiment, For example, it can deform | transform and implement as follows, These embodiments also belong to the technical scope of this invention.

  4 is a diagram for explaining a modification of the video display apparatus 101 according to the first embodiment of the present invention, and FIG. 4A is a diagram of the modification 1 compared with FIG. (B) is the figure of the modification 2 compared with FIG.

<Modification 1>
In the first embodiment, when the predetermined limit current value R1 is exceeded three times, the current flowing to the laser light source LD is greatly reduced. However, as shown in FIG. You may make it control by determining in multiple times.

<Modification 2>
Further, as shown in FIG. 4B, the time-based control is performed such that the current flowing through the laser light source LD is greatly reduced when the time exceeding the predetermined limit current value R1 is the predetermined time T1. You may do it.

<Modification 3>
In the first embodiment, the laser light source LD is preferably configured so as to provide the laser light sources LD (RLD, GLD, BLD) of three colors, red (Red), green (Green), and blue (Blue). Furthermore, a configuration in which four color laser light sources with yellow (Yellow) added may be provided, or a configuration in which four or more color laser light sources may be provided. Conversely, it may be configured to use only one color laser light source or a combination of two color laser light sources.

<Modification 4>
In the first embodiment, the image generation unit 11 is configured by the holographic optical element 41 that diffracts the coherent light into the image light Lf. However, the image generation unit 11 is not limited to this, and is the same scanning type image generation unit as the conventional example. Also good.

<Modification 5>
In the first embodiment, the diffuser 13 is preferably disposed on the rear side of the optical path of the slitter 52. However, the diffuser 13 may be disposed on the optical path after the Fourier lens FL1.

<Modification 6>
In the said 1st Embodiment, although it was application to the head up display (HUD, Head-Up Display) mounted in the vehicle, it is not restricted to this, For example, a three-dimensional display, a head mounted display (HMD, It is also applicable to Head Mounted Display).

  The present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the scope of the object of the present invention.

11 Image generation unit 14, 14R, 14G, 14B Laser light source drive unit 35, 35R, 35G, 35B Light intensity detection unit 55 Control unit 75 Current value detection unit Lc Laser light Lf Video light LD, RLD, GLD, BLD Laser light source K5 Current storage unit M15 Light control means OP Optical member ST Observer VM Video 101 Video display device

Claims (3)

A laser light source for emitting laser light;
A laser light source driving unit for supplying power to the laser light source;
Light control means for controlling the light intensity of the laser light;
An image generation unit that generates a desired display image from the laser beam,
A video display device that allows an observer to observe the video of the display image,
The light control means includes a light intensity detector that detects the light intensity;
A control unit for controlling the output of the laser light source driving unit based on the detection result of the light intensity detection unit;
A current value detection unit for detecting a current value output from the laser light source driving unit,
When the current value becomes larger than a predetermined limit current value previously stored in the current storage unit, the control unit outputs and controls a current equal to or less than the limit current value. apparatus.   2. The video display device according to claim 1, wherein a plurality of the laser light sources are provided, and a plurality of the light control means are provided corresponding to the plurality of the laser light sources. The image generation unit, a holographic optical element that diffracts the laser light to make video light,
An optical member for guiding the image light from the holographic optical element,
The light intensity detector detects the light intensity of the image light;
The video display device according to claim 1, wherein the light control unit controls an output of the laser light source driving unit based on a detection result of the light intensity detection unit.