JP2016057368A - Image projection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image projection device with a light source comprising laser emitting elements, capable of stably projecting images with a wide range of brightness without pulse-width-modulating drive current for the laser emitting element.SOLUTION: An image projection device comprises a laser light source that emits a laser beam by combining a plurality of first laser beams of wavelengths belonging to a same color generated by a plurality of emission points LD111, LD112 with a second laser beam. Whether to supply the drive current to some of the plurality of emission points (partial lighting) or to all the emission points (full lighting) is selected depending on whether or not a target intensity of the second laser beam is within a management range (Pb-Pa), which is a range of the second laser beam intensity obtained when the same drive current is distributed to all the emission points and one or more emission points are operating in a predefined unstable region that includes a mode competition region.SELECTED DRAWING: Figure 7

Description

  The present invention relates to an image projection apparatus, and more particularly to an image projection apparatus using a laser light emitting element as a light source.

  Conventionally, an image projection apparatus using a laser light emitting element as a light source is used as a laser projector, a vehicle-mounted HUD (head-up display), or the like. Such an image projection apparatus includes, for example, a laser light emitting element that emits red light, a laser light emitting element that emits green light, and a laser light emitting element that emits blue light, and each of these laser light emitting elements emits light. A color image is projected onto the screen by directing light to the screen.

  One of the performances of the image projection apparatus is a wide range of brightness of an image (also called a dynamic range) that can be stably projected. For example, when the image projection apparatus is used for a vehicle-mounted HUD, if the dynamic range is wide, for example, a driver depending on the situation under any circumstances where the intensity of outside light is extremely different from clear day to night. Can display an image with brightness suitable for viewing.

  As is well known, the laser light emitting element has a minimum driving current (so-called threshold current) necessary for stably performing laser oscillation. The laser light-emitting element stably emits laser light having an intensity corresponding to the amount of drive current when a drive current greater than the threshold value is supplied. On the other hand, when a current less than the threshold value is supplied, the laser beam cannot be stably emitted.

  Therefore, a technique is known in which a laser light emitting element emits light with a drive current having an amplitude equal to or greater than the threshold value and pulse width modulated (for example, Patent Document 1). According to this technique, a laser beam having a small effective intensity can be stably obtained as compared with the case where the laser light emitting element continuously emits light.

International Publication No. 2012/104967

  However, when the laser light emitting element emits pulses, a switching circuit that chops a relatively large current at a frequency higher than at least the pixel frequency is required to generate a pulse-width-modulated driving current, thereby simplifying the circuit. There are disadvantages in the above.

  Further, since the drive current is a high-frequency pulse current, mounting restrictions such as providing a drive current supply path as short as possible are likely to occur in order to reduce waveform distortion and suppress electromagnetic noise.

  The present invention has been made in view of such a problem, and is an image projection apparatus using a laser light emitting element as a light source, and without performing pulse width modulation on the driving current of the laser light emitting element, An object of the present invention is to provide an image projection apparatus capable of stably projecting in a wide luminance range.

  In order to achieve the above object, an image projection apparatus according to one aspect disclosed includes a plurality of light emitting points that emit a plurality of first laser beams having wavelengths belonging to one color, and the plurality of first laser beams. A laser light source having a beam shaper coupled to one second laser light; a beam deflector that periodically changes the traveling direction of the second laser light; and a variable drive current for the light emitting points. A driver for supplying to one or more light emitting points selected from among the drivers, and controlling the driver according to a target intensity of the second laser beam, wherein the target intensity is one drive current for all the light emitting points. Whether or not one or more of the emission points distributed is included in a management range that is a range of the intensity of the second laser beam obtained when operating in a predetermined unstable region including a mode competition region In response, one drive power The and a controller that switches whether distributed to all or to supply a portion of the plurality of light emitting points.

  As a result, when all of the plurality of light emitting points are emitted to generate light, there is a concern that the light intensity may become unstable. Is generated. That is, since the laser light having the intensity in the management range is generated by emitting a smaller number of light emitting points, the light intensity generated at each light emitting point becomes higher. As a result, each light emitting point can operate while avoiding the unstable region, and the concern that the light intensity becomes unstable is alleviated.

  In addition, the controller indicates the amount of current that can be obtained by supplying the intensity of each of the plurality of intensities included in the management range to the part of the plurality of light emitting points as the amount of drive current, The part of the plurality of light emitting points is shown as a supply destination of the light source, and each of the plurality of intensities not included in the management range is distributed to all of the plurality of light emitting points as an amount of drive current. By indicating correspondence between the plurality of light emitting points as a drive current supply destination and indicating the amount of current obtained, and controlling the driver according to the correspondence information, an amount of drive current corresponding to the target intensity is obtained. May be supplied to a supply destination corresponding to the target intensity.

  Accordingly, the controller can obtain the above-described effect by controlling the driver according to the correspondence information.

  Each of the plurality of light emitting points has an individual threshold value that is a minimum value of an operating current necessary for starting laser oscillation, and the unstable region of each of the plurality of light emitting points is: It may be defined by a predetermined current range around the threshold value of the light emitting point.

  Thereby, the above-mentioned effect can be obtained by controlling the driver based on the threshold value.

  In addition, when the target intensity is included in the management range, the controller controls the driver to supply the driving current to one light emitting point having the smallest threshold among the plurality of light emitting points. May be.

  This increases the possibility that laser light having a light intensity within the management range can be generated with a smaller drive current, which is advantageous in terms of power saving of the image projection apparatus.

  The plurality of light emitting points are provided in different laser light emitting elements, and the beam shaper includes a beam combiner for combining the plurality of first laser lights with the second laser light, and the second laser light. And a collimating lens that converts the light into substantially parallel light.

  Thereby, the laser light source can be constituted by the light emitting point, the beam combiner, and the collimating lens.

  Each of the plurality of light emitting points is provided in a single laser light emitting element, and the beam shaper includes a collimator lens that converts each of the plurality of first laser lights into substantially parallel light, and substantially parallel light. The plurality of first laser beams after conversion may be received in different regions and diffracted in substantially the same traveling direction.

  Each of the plurality of light emitting points is provided in a single laser light emitting element, and the beam shaper receives the plurality of first laser beams in different regions and diffracts them in different traveling directions. And a collimating lens that converts each of the plurality of first laser lights after diffraction into substantially parallel light, and the diffraction grating plate converts the plurality of first laser lights into light of the collimating lens. You may make it diffract in the direction which can be considered that it was radiate | emitted from one point on an axis | shaft.

  Thereby, the laser light source can be constituted by the light emitting point, the collimating lens, and the diffraction grating plate.

  The laser light source is provided corresponding to each of a plurality of colors, and the image projection apparatus further includes a beam combiner that combines the second laser light for each color into one third laser light, The beam deflector periodically changes the traveling direction of the third laser light, and the driver applies a variable driving current for each color of the plurality of light emitting points included in the laser light source corresponding to the color. The controller supplies to one or more light emitting points selected from among the plurality of light emitting points corresponding to the color, for each color, a drive current of an amount corresponding to a target intensity of the second laser light of the color. It may be switched between supplying to a part of the light emitting points and distributing to all of the light emitting points.

  Thereby, a color image projector is obtained.

  The present invention can be realized not only as such an image projection apparatus but also as a control method of an image projection apparatus including steps executed in such an image projection apparatus. Moreover, such a control method can also be realized as a program for causing a computer to execute.

  According to the present invention, an image projection apparatus using a laser light emitting element as a light source, which can stably project an image in a wide luminance range without performing pulse width modulation on the drive current of the laser light emitting element. A device is obtained.

2 is a block diagram illustrating an example of a functional configuration of the image projection apparatus according to Embodiment 1. FIG. 2 is a block diagram illustrating an example of a functional configuration of a laser light source according to Embodiment 1. FIG. 2 is a block diagram illustrating an example of a functional configuration of a laser driver according to Embodiment 1. FIG. 6 is a diagram showing an example of correspondence information according to Embodiment 1. FIG. 4 is a timing chart illustrating an example of a time change of main input / output signals of the laser driver according to the first embodiment. It is a graph explaining an example of the control method of the image projector concerning a comparative example. 6 is a graph illustrating an example of a control method for the image projection apparatus according to the first embodiment. 6 is a block diagram illustrating an example of a functional configuration of a laser light source according to Embodiment 2. FIG. 6 is a conceptual diagram illustrating an example of a detailed configuration of a diffraction grating plate according to Embodiment 2. FIG. 10 is a block diagram illustrating an example of a functional configuration of a laser light source according to Embodiment 3. FIG. 6 is a conceptual diagram illustrating an example of a detailed configuration of a diffraction grating plate according to Embodiment 3. FIG. FIG. 10 is a diagram illustrating a usage example of an image projection device in a car navigation system according to a fourth embodiment. It is a graph which shows an example of the typical light emission characteristic of a laser diode.

(Knowledge that became the basis of the present invention)
As described in the section of the background art, the present inventor has a disadvantage in simplifying the circuit when the laser light emitting element emits light by pulse width modulation, and that mounting restrictions are likely to occur. It pointed out. Accordingly, the present inventor has studied a method for obtaining a laser beam having a wide dynamic range of intensity while continuously emitting laser light emitting elements.

  In this examination, the present inventor first confirmed the light emission characteristics of the laser light emitting element.

  FIG. 11 is a graph showing an example of typical light emission characteristics of a laser diode as an example of a laser light emitting element. FIG. 11 shows the operation mode of the laser diode and the light intensity obtained from the laser diode corresponding to various drive currents of the laser diode.

  As shown in FIG. 11, in an LED (Light Emitting Diode) light emitting region having a small driving current, the laser diode emits a light beam by spontaneous emission, like the light emitting diode. The light beam obtained in the LED light emitting region has an incoherent, broad spectrum and low intensity, but has a stable intensity that corresponds well with the drive current.

  In the multimode oscillation region where the drive current is larger, the laser diode simultaneously oscillates in a number of oscillation modes corresponding to different wavelengths. The laser light obtained in the multimode oscillation region has intensity peaks at a plurality of wavelengths, and has a stable intensity that corresponds well with the drive current as the sum of the light intensities at the respective wavelengths.

  In the mode competition region where the drive current is larger, the laser diode oscillates while rapidly hopping one of a plurality of oscillation modes corresponding to different wavelengths. In the laser light obtained in the mode competition region, the intensity peak is rapidly switched to the wavelength corresponding to the oscillation mode in which the laser oscillation occurs. Therefore, although the intensity of the laser beam corresponds to the drive current on a time average, it varies instantaneously within a range corresponding to the drive current. Note that the threshold value of the laser diode is included in the mode competition region.

  In the single mode oscillation region where the drive current is larger, the laser diode generates laser oscillation in a single oscillation mode. The laser light obtained in the single mode oscillation region is coherent, has a peak of intensity at a single wavelength, and has a stable intensity that corresponds well with the drive current.

  Conventionally, based on such light emission characteristics, it is a common sense to operate a laser diode with single mode oscillation. In order to obtain a laser beam having a small effective intensity, a conventional technique in which a laser diode emits light with a drive current having an amplitude equal to or greater than a threshold value and pulse width modulated is also based on this concept.

  On the other hand, the present inventor, for example, in an image projection apparatus, in an application that allows incoherence of a laser beam and a slight spread of a spectrum, not only a single mode oscillation region but also a multimode oscillation region It has been found that the laser diode should be allowed to emit light continuously using the LED emission region. In this case, however, it is necessary to avoid the laser diode from operating in the mode competition region. As described above, there is a temporal fluctuation in the intensity of the laser beam obtained in the mode competition region, and there is a concern that when the screen is scanned with the laser beam, luminance unevenness and color unevenness may occur in the projected image. is there.

  However, the problem that the laser beam in the intensity range corresponding to the mode competition region cannot be obtained simply by excluding the mode competition region is left.

  As a result of intensive studies based on such knowledge, the present inventor has reached the image projection apparatus of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that each of the embodiments described below shows a specific example of the present invention. The numerical values, shapes, materials, constituent elements, arrangement of constituent elements, connection forms, and the like shown in the following embodiments are merely examples, and are not intended to limit the present invention. In addition, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims are described as arbitrary constituent elements.

(Embodiment 1)
The image projection apparatus according to Embodiment 1 is an image projection apparatus that generates laser light whose intensity is modulated for each pixel with a laser light source, and scans the screen with the laser light, thereby projecting an image on the screen. .

  The laser light source is provided with a plurality of light emitting points, and the image projection apparatus is configured to obtain 1 laser light having a target intensity according to whether or not the target intensity is included in a management range. One drive current is switched to be supplied to a part of the light emitting points or distributed to all the light emitting points. The management range is the laser beam obtained when one drive current is distributed to all the light emission points and one or more of the light emission points operate in a predetermined unstable region including the mode competition region. Defined as a range of intensity.

  FIG. 1 is a block diagram illustrating an example of a functional configuration of the image projection apparatus according to the first embodiment. As shown in FIG. 1, the image projection apparatus 100 includes laser light sources 110, 120, and 130, beam combiners 151 and 152, a beam deflector 160, a laser driver 170, a deflection driver 180, a controller 190, and an operation unit 191. Prepare. FIG. 1 shows a screen 200 on which an image is projected together with the image projector 100.

  The laser light sources 110, 120, and 130 are provided corresponding to, for example, red, green, and blue, respectively, and combine a plurality of first laser beams having wavelengths belonging to one corresponding color into one second laser beam L2. A laser light source that emits light. Details of the laser light sources 110, 120, and 130 will be described later.

  The beam combiners 151 and 152 are optical elements that combine the second laser light L2 for each color emitted from each of the laser light sources 110, 120, and 130 into one third laser light L3. The beam combiners 151 and 152 may be constituted by, for example, dichroic prisms.

  The beam deflector 160 is an optical element that periodically changes the traveling direction of the third laser light L3 combined with the second laser light L2. The beam deflector 160 deflects the third laser light L3 toward the screen 200 so as to scan the screen 200. The beam deflector 160 may be composed of, for example, a biaxial movable mirror and an actuator that moves the movable mirror.

  The laser driver 170 is a driver that supplies a drive current to the laser light sources 110, 120, and 130 based on control by the controller 190. Details of the laser driver 170 will be described later.

  The deflection driver 180 is a driver that controls the direction of the beam deflector 160 based on the control by the controller 190.

  The controller 190 controls the laser driver 170 and the deflection driver 180 to generate intensity-modulated laser light for each pixel, and scans the screen 200 with the laser light, thereby projecting a desired image on the screen 200. To do. For example, the controller 190 may project each frame of a video represented by a video signal (not shown) supplied from the outside of the image projection device 100 onto the screen 200.

  The controller 190 may be configured by, for example, a one-chip microcomputer having an MPU (Micro Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), an I / O (Input / Output) port, and the like. The control function of the controller 190 may be a software function performed by the MPU executing a program recorded in the ROM using the RAM as a working memory.

  The operation unit 191 is a unit that receives a user operation for instructing the operation of the image projection apparatus 100. The instruction received by the operation unit 191 from the user may include, for example, an instruction to turn on and off the power of the image projection apparatus 100. The operation unit 191 may be configured by a mechanical switch or a touch panel provided in the casing of the image projection apparatus 100, and is configured by a remote control interface that receives a signal transmitted from a remote controller separate from the image projection apparatus 100. May be.

  Next, the configuration of the laser light sources 110, 120, and 130 will be described.

  FIG. 2 is a block diagram illustrating an example of a functional configuration of the laser light sources 110, 120, and 130. FIG. 2 shows the beam combiners 151 and 152 together with the laser light sources 110, 120 and 130.

  Since all of the laser light sources 110, 120, and 130 have the same configuration, the configuration of the laser light source 110 will be described below as a representative. In addition, the following description is valid also about the laser light sources 120 and 130 by changing the code | symbol of a corresponding component.

  As shown in FIG. 2, the laser light source 110 includes emission points 111 and 112, a beam combiner 113, and a collimating lens 114.

  Each of the light emitting points 111 and 112 emits a first laser beam L1 having a wavelength belonging to a color corresponding to the laser light source 110. The light emitting points 111 and 112 may be constituted by, for example, single-beam output type laser diodes as discrete components enclosed in separate packages. The wavelength of the first laser light L1 emitted from the light emitting points 111 and 112 does not need to be exactly the same. For example, any one of red, green, and blue used in the color image projector is used. There may be an error in the visible range.

  The beam combiner 113 is an optical element that combines a plurality of first laser beams L1 into one second laser beam L2. The beam combiner 113 may be configured with a polarization beam splitter, for example.

  The collimating lens 114 is an optical element that converts the second laser light L2 into substantially parallel light. The second laser light L2 may be strictly parallel light, or may be parallel light including an error depending on the accuracy of the optical system. In addition, the second laser light L2 may be intentionally converged light that slightly deviates from parallel light, and may be converged on the screen 200.

  Here, the beam combiner 113 and the collimating lens 114 constitute a beam shaper in the laser light source 110.

  Next, the configuration and operation of the laser driver 170 will be described.

  FIG. 3 is a block diagram illustrating an example of a functional configuration of the laser driver 170. FIG. 3 shows the laser light sources 110, 120, and 130 and the controller 190 together with the laser driver 170. In the example of FIG. 3, for example, in the laser light source 110, the light emitting points 111 and 112 are connected by the cathode common, and the same applies to the laser light sources 120 and 130.

  As shown in FIG. 3, the laser driver 170 includes a DAC (digital-analog converter) 171, an AND gate 172, a latch 173, and switches 174 to 179.

  The controller 190 supplies the data signal DATA, the selection signal SEL, the data clock signal DCLK, and the pixel clock signal PCLK to the laser driver 170.

  Here, the data signal DATA indicates the amount of drive current to be supplied to each of the laser light sources 110, 120, and 130 as a digital value. The selection signal SEL indicates, as a binary value, whether or not to supply a drive current to each of the light emitting points 111, 112, 121, 122, 131, and 132. The data clock DCLK indicates the synchronization of the data signal DATA. The pixel clock PCLK indicates pixel synchronization.

  FIG. 4 shows an example of the data signal DATA, the selection signal SEL, the data clock signal DCLK, and the pixel clock signal PCLK, and the light emitting points (abbreviated as LD in the drawing) 111, 112, 121, 122 according to these signals. , 131, 132 is a timing chart showing an example of the amount of current supplied to the circuit.

  In the laser driver 170, the DAC 171 acquires the data signal DATA in synchronization with the data clock DCLK, and outputs the driving current of the amount indicated by the acquired data signal DATA for each of the laser light sources 110, 120, and 130 to the pixel clock PCLK. Generate in sync with.

  The AND gate 172 generates a latch trigger signal by obtaining a logical product of the data clock DCLK and the pixel clock PCLK.

  The latch 173 latches the selection signal SEL for each pixel clock PCLK according to the latch trigger signal, and outputs the latched selection signal SEL as a control signal for the switches 174 to 179.

  The switches 174 to 179 are provided in the drive current paths of the light emitting points 111, 112, 121, 122, 131, 132, respectively, and are turned on and off according to the selection signal SEL, thereby driving to the corresponding light emitting point. Switch between current supply and interruption. For example, according to the operation of the switches 174 and 175 in accordance with the selection signal SEL, whether one driving current generated for the laser light source 110 is supplied to one of the light emitting points 111 and 112 or distributed to both is switched. Similarly, for the laser light sources 120 and 130, the supply destination of the drive current is switched according to the operation of the corresponding switch.

  Next, the correspondence between the light intensity, the amount of drive current, and the supply destination will be described.

  FIG. 5 is a diagram illustrating an example of correspondence information indicating correspondence between the light intensity, the amount of drive current, and the supply destination. The correspondence information shown in FIG. 5 includes the amount of drive current supplied to the laser light source 110 corresponding to a plurality of different intensities of the laser light emitted from the laser light source 110 (the second laser light L2 described above), and It shows which of the light emitting points 111 and 112 the drive current is supplied to. For the laser light sources 120 and 130, the correspondence information indicates the correspondence between the light intensity, the amount of drive current, and the supply destination. Such correspondence information may be expressed by any known method such as a numerical table or a mathematical expression.

  The correspondence information associates the light intensity with the amount of drive current and the supply destination based on the following concept.

  First, a management range is defined for the light intensity of each of the laser light sources 110, 120, and 130. The management range is when one driving current is distributed to both of two light emitting points included in the laser light source and at least one of the light emitting points operates in a predetermined unstable region including the mode competition region Further, it is defined as the range of the intensity of the laser light obtained from the laser light source.

  The correspondence information includes, for each of a plurality of light intensities included in the management range, supplying a current amount of the second laser light having the intensity by supplying one of the plurality of light emitting points as a drive current amount. The one of the plurality of light emitting points is shown as a drive current supply destination.

  Further, the correspondence information is obtained by distributing the driving current amount to all of the plurality of light emitting points for each of a plurality of intensities not included in the management range, thereby obtaining the second laser light having the intensity. All of the plurality of light emitting points as the supply destination of the drive current.

  Detailed description will be continued on the unstable area, the management range, the amount of drive current, and the technical significance of the supply destination.

  FIG. 6 is a diagram for explaining the unstable region and the management range.

  The graphs of FIGS. 6A and 6B are graphs showing the relationship between the drive current and the light intensity when the light emitting points 111 and 112 emit light independently. As described above with reference to FIG. 11, there is a mode competition region in these individual light emission characteristics.

  An unstable region including such a mode competition region is determined in advance. The unstable region may be, for example, a region in which the width of the mode competition region is widened with a predetermined safety margin. Specifically, the unstable region is defined by a predetermined current range around the threshold value of the light emitting point. Also good. Such a current range may be defined by a ratio to a threshold current, for example. As an example, when the threshold current is 50 mA and ± 30% of the threshold current is defined as an unstable region, a driving current range of 35 mA to 65 mA is defined as the unstable region.

  As shown in FIGS. 6A and 6B, the unstable regions of the light emitting points 111 and 112 have a current range having a first width above the threshold values Ith1 and Ith2 of the light emitting points 111 and 112, respectively. You may prescribe | regulate by the electric current range which united the electric current range of the 2nd width | variety on the lower side. Generally, unlike the threshold value Ith1 and the threshold value Ith2, in the example shown in FIGS. 6A and 6B, the threshold value Ith2 is smaller than the threshold value Ith1.

  The graph of FIG. 6C is a graph showing the relationship between the drive current and the total light intensity when one drive current is distributed to both the light emitting points 111 and 112 (also referred to as all lighting). is there. In all lighting, the drive current is distributed to both the light emitting points 111 and 112 at a ratio according to the characteristics of the light emitting points 111 and 112. In accordance with this distribution, the aforementioned light intensity management range is specified as follows.

  Assuming that the driving current for distributing the upper limit current Ia1 of the unstable region to the light emitting point 111 is Ia1 + Ia2, the remaining current Ia2 is distributed to the light emitting point 112 in accordance with the driving current Ia1 + Ia2. When the light intensities obtained at the light emitting points 111 and 112 by the currents Ia1 and Ia2 are Pa1 and Pa2, respectively, the upper limit of the management range is specified by the total light intensity Pa1 + Pa2.

  Further, if the driving current for distributing the lower limit current Ib2 of the unstable region to the light emitting point 112 is Ib1 + Ib2, the remaining current Ib1 is distributed to the light emitting point 111 according to the driving current Ib1 + Ib2. When the light intensities obtained at the light emission points 111 and 112 by the currents Ib1 and Ib2 are Pb1 and Pb2, respectively, the lower limit of the light intensity management range is specified by the total light intensity Pb1 + Pb2.

  In this way, a range of light intensity obtained in total when one drive current is distributed to both of the light emitting points 111 and 112 and at least one of the light emitting points 111 and 112 operates in the unstable region (that is, The management range that is the light intensity Pb to Pa) is specified.

  The currents Io1 and Io2 shown in FIG. 6 represent the rated currents of the light emitting points 111 and 112, respectively, and the light intensities Po1 and Po2 represent the rated light intensities of the light emitting points 111 and 112, respectively.

  As described above, there is a concern that at least one of the light emitting points 111 and 112 may operate in the unstable region when the laser light source 110 generates all the laser light having the light intensity included in the management range by lighting. Therefore, when the target intensity of the laser light generated by the laser light source 110 is included in the management range, a drive current is supplied to only one of the light emitting points 111 and 112 (also referred to as partial lighting). In addition, the drive current is supplied in such an amount that the laser beam having the target intensity can be obtained by one of the light emitting points 111 and 112 alone.

  FIG. 7 is a diagram for explaining the amount of drive current for generating a part of the laser beam having an intensity included in the management range by lighting.

  The graphs of FIGS. 7A and 7B are the same as the graphs of FIGS. 6A and 6B. In the example of FIG. 7C, only the light emitting point 112 emits light (partially lights up) in order to obtain laser light having an intensity within the management range.

  From FIG. 7B, the drive currents for obtaining the light intensity of the lower limit Pb and the upper limit Pa of the management range with the light emitting point 112 alone are Ib and Ia, respectively. Therefore, in the partial lighting of FIG. 7C, by supplying a drive current in the range from Ib to Ia only to the light emitting point 112, laser light having a target intensity included in the management range is generated. Yes.

  As long as the unstable region, the management range, the amount of drive current, and the supply destination are specified based on the above-mentioned concept, for example, they may be specified by actual measurement, and simulation, logical calculation, catalog specifications It may be specified by any well-known method such as reference.

  The management range identified in this way, the amount of drive current, and the supply destination are held as correspondence information in FIG.

  For example, the controller 190 may hold the correspondence information shown in FIG. 5 in advance for each of the laser light sources 110, 120, and 130. The controller 190 generates a data signal DATA and a selection signal SEL indicating a current amount and a supply destination of the drive current associated with the light intensity for each pixel based on the correspondence information held, and supplies the data signal DATA and the selection signal SEL to the laser driver 170. Also good.

  Thereby, the operation in the unstable region is avoided, and as a result, the laser beam having the intensity within the management range can be stably obtained.

  In the above description, for example, as shown in FIG. 7C, the drive current is supplied only to the light emitting point 112 in partial lighting. In this way, in partial lighting, by turning on a light emitting point having a smaller threshold value, the possibility that laser light having a light intensity within the management range can be generated with a smaller driving current is increased. This is advantageous in terms of power saving performance of 100.

  In the above description, two light emitting points are provided in each of the laser light sources 110, 120, and 130, but the number of light emitting points provided in one laser light source is not limited. The number of light emitting points may be three or more, and may be different for each laser light source. The number of light emitting points provided in one laser light source may be determined, for example, according to the required maximum intensity of laser light.

  Further, all the light emitting points may be turned on in the all lighting, and one or more but not all the light emitting points may be turned on in the partial lighting. The number of light emission points provided in one laser light source and the number of light emission points to be turned on by partial lighting are, for example, individual light emission so that the light intensity obtained by partial lighting matches the light intensity in the management range. It may be determined in consideration of the light emission characteristics of points.

(Embodiment 2)
The image projection apparatus according to the second embodiment is different in the configuration of the laser light source from the image projection apparatus according to the first embodiment.

  FIG. 8 is a block diagram illustrating an example of a functional configuration of the laser light source according to the second embodiment. The laser light source 140 shown in FIG. 8 is replaced with the laser light sources 110, 120, and 130 of the image projection apparatus 100 according to the first embodiment.

  The laser light source 140 includes a semiconductor chip 145 on which light emitting points 141 and 142 are formed, a collimating lens 114, and a diffraction grating plate 143.

  Each of the light emitting points 141 and 142 emits a first laser beam L1 having a wavelength belonging to a color corresponding to the laser light source 140. The light emitting points 141 and 142 may be constituted by, for example, a multi-beam output type laser diode as a discrete component enclosed in a single package.

  The collimating lens 114 is an optical element that converts each of the plurality of first laser beams L1 into substantially parallel light.

  The diffraction grating plate 143 is an optical element that receives a plurality of first laser beams L1 converted into substantially parallel light in different regions and diffracts them in substantially the same traveling direction.

  The laser light source 140 emits a plurality of first laser beams L1 whose traveling directions are aligned by the diffraction grating plate 143 as the second laser beams L2.

  FIG. 9 is a conceptual diagram illustrating an example of a detailed configuration of the diffraction grating plate 143.

  As shown in FIG. 9, the diffraction grating plate 143 receives the first laser light L <b> 1 from the light emitting point 142 in the region 1431 and receives the first laser light L <b> 1 from the light emitting point 141 in the region 1432.

  The region 1431 is provided with a diffraction grating that strongly emits the −1st order light of the first laser light L1 incident from the light emitting point 142, and the region 1432 is the + 1st order of the first laser light L1 incident from the light emitting point 141. A diffraction grating that emits light strongly is provided. The traveling directions of the −1st order light and the + 1st order light are substantially the same. The diffraction grating may be constituted by, for example, a surface (blazed surface) whose groove has a sawtooth cross-sectional shape.

  In the image projection apparatus according to the second embodiment, the laser light source 140 configured as described above is used in place of the laser light sources 110, 120, and 130 of the image projection apparatus 100 according to the first embodiment. It is possible to obtain the same effect as that described in the first image projection apparatus 100.

(Embodiment 3)
In the second embodiment, the example of the laser light source 140 in which the light emitting points 141 and 142, the collimating lens 114, and the diffraction grating plate 143 are arranged in this order in the traveling direction of the laser light has been described. However, the arrangement of the components of the laser light source is described. Is not limited to this example. In the third embodiment, an example of a laser light source having a different arrangement of components will be described.

  FIG. 10 is a diagram illustrating an example of a configuration of a laser light source according to the third embodiment.

  As shown in FIG. 10, the laser light source 150 is different from the laser light source 140 shown in FIG. 8 in that the arrangement order of the collimating lens 114 and the diffraction grating plate 143 is reversed. That is, in the laser light source 150, the light emitting points 141 and 142, the diffraction grating plate 143, and the collimating lens 114 are arranged in this order in the traveling direction of the laser light.

  FIG. 11 is a conceptual diagram showing an example of a detailed configuration of the diffraction grating plate 143.

  As shown in FIG. 11, the diffraction grating plate 143 in the laser light source 150 receives the first laser light L1 emitted from the light emitting points 141 and 142 in different areas, and receives one point on the optical axis of the collimating lens 114. Diffracted in a direction that can be regarded as being emitted from. Thereby, the virtual images of the light emitting points 141 and 142 can be matched.

  In the image projection apparatus according to the third embodiment, the laser light source 150 configured as described above is used in place of the laser light sources 110, 120, and 130 of the image projection apparatus 100 according to the first embodiment. It is possible to obtain the same effect as that described in the first image projection apparatus 100.

(Embodiment 4)
FIG. 10 is a diagram illustrating an example of a HUD as an example of use of the image projection apparatus according to the fourth embodiment.

  As shown in FIG. 10, HUD 1 includes image projection apparatus 100 and screen 200 according to Embodiments 1, 2, and 3. The HUD 1 is mounted on, for example, an automobile and used as a display device for a car navigation system.

  The image projection device 100 projects an image including navigation information on the screen 200. The screen 200 projects the projected image in the driver's field of view as a virtual image at the tip of the windshield (in the scenery outside the vehicle). The screen 200 used for the HUD is also called a combiner.

  As described above, the image projection apparatus 100 is excellent for stably projecting an image in a wide luminance range. For example, in any situation where the intensity of outside light is extremely different from a clear day to a dark night. Even underneath, the car navigation information can be presented to the driver with an image having a luminance suitable for the driver to visually recognize the situation.

  The image display apparatus according to the embodiment of the present invention and the HUD as an example of use thereof have been described above, but the present invention is not limited to this embodiment. Unless it deviates from the meaning of this invention, the form which gave various deformation | transformation which those skilled in the art can think to this Embodiment can be contained in the scope of the present invention.

  The present invention can be applied as a projector device to, for example, a head-up display device mounted on an automobile.

1 HUD
100 Image projector 110, 120, 130, 140, 150 Laser light source 111, 112, 121, 122, 131, 132, 141, 142 Light emitting point 113, 123, 133 Beam combiner 114, 124, 134 Collimator lens 143 Diffraction grating Plate 145 Semiconductor chip 151, 152 Beam combiner 160 Beam deflector 170 Laser driver 171 DAC
172 AND gate 173 Latch 174 to 179 Switch 180 Deflection driver 190 Controller 191 Operation unit 200 Screen

Claims (8)

A laser light source having a plurality of light emitting points that emit a plurality of first laser beams having wavelengths belonging to one color, and a beam shaper that couples the plurality of first laser beams to one second laser beam;
A beam deflector that periodically changes the traveling direction of the second laser light;
A driver for supplying a variable drive current to one or more light emitting points selected from the plurality of light emitting points;
The driver is controlled in accordance with a target intensity of the second laser light, and the target intensity is distributed in advance so that one driving current is distributed to all the light emitting points, and one or more of the light emitting points include a mode competition region in advance. Depending on whether or not it is included in the management range that is the range of the intensity of the second laser beam obtained when operating in a defined unstable region, one drive current is made a part of the plurality of light emitting points. A controller that switches between supplying or distributing to all,
An image projection apparatus comprising: The controller is
Holding correspondence information indicating the correspondence between the plurality of intensities of the second laser light, the amount of drive current, and the supply destination;
The correspondence information includes, for each of a plurality of intensities included in the management range, an amount of current by which the second laser beam having the intensity can be obtained by supplying the part of the plurality of light emission points as a drive current amount. The part of the plurality of light emission points is shown as a drive current supply destination, and the amount of drive current is distributed to all of the plurality of light emission points for each of a plurality of intensities not included in the management range. Showing the amount of current from which the second laser beam of the intensity can be obtained, showing all of the plurality of light emitting points as a drive current supply destination,
The controller is
By controlling the driver according to the correspondence information, an amount of drive current corresponding to the target strength is supplied to a supply destination corresponding to the target strength.
The image projection apparatus according to claim 1. Each of the plurality of light emitting points has an individual threshold value that is a minimum value of an operating current necessary for starting laser oscillation,
The unstable region of each of the plurality of light emitting points is defined by a current range that is predetermined around the threshold value of the light emitting points.
The image projection device according to claim 1. When the target intensity is included in the management range, the controller supplies the driving current to one light emitting point having the smallest threshold value among the plurality of light emitting points by controlling the driver.
The image projection apparatus according to claim 3. The plurality of light emitting points are provided in different laser light emitting elements,
The beam shaper includes a beam combiner that combines the plurality of first laser lights with the second laser light, and a collimator lens that converts the second laser light into substantially parallel light.
The image projection apparatus of any one of Claims 1-4. Each of the plurality of light emitting points is provided in a single laser light emitting element,
The beam shaper receives substantially the same collimating lens that converts each of the plurality of first laser beams into substantially parallel light, and the plurality of first laser beams that have been converted into substantially parallel light in different regions. A diffraction grating plate that diffracts in the traveling direction,
The image projection apparatus of any one of Claims 1-4. Each of the plurality of light emitting points is provided in a single laser light emitting element,
The beam shaper includes a diffraction grating plate that receives the plurality of first laser beams in different regions and diffracts them in different traveling directions, and makes each of the plurality of first laser beams after diffraction be substantially parallel beams. A collimating lens for conversion, and the diffraction grating plate diffracts the plurality of first laser lights in a direction that can be regarded as emitted from one point on the optical axis of the collimating lens.
The image projection apparatus of any one of Claims 1-4. The laser light source is provided corresponding to each of a plurality of colors,
The image projection apparatus further includes a beam combiner that combines the second laser light for each color into one third laser light,
The beam deflector periodically changes the traveling direction of the third laser light,
The driver supplies a variable drive current for each color to one or more light emitting points selected from the plurality of light emitting points included in the laser light source corresponding to the color,
Whether the controller supplies, for each color, a drive current of an amount corresponding to the target intensity of the second laser light of the color to some or all of the plurality of light emitting points corresponding to the color Switch
The image projection apparatus of any one of Claims 1-7.

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