JP2019211641A - Light source device, display unit, display system, movable body, and light quantity control method - Google Patents

Abstract

To make it possible to optimize a light quantity control range used for light quantity control.SOLUTION: A light source device according to an embodiment of the present invention comprises: a light source element 111 (an example of a light source) that outputs a laser beam; and a control circuit 300 that controls the quantity of the laser beam output from the light source element 111. The control circuit 300 sets a light quantity control range indicating the range of a current value used for controlling the light quantity, on the basis of an output from a photo detector 119 that detects the laser beam output from the light source element 111, and controls the quantity of the laser beam output from the light source element 111 in the set light quantity control range.SELECTED DRAWING: Figure 12

Description

  The present invention relates to a light source device, a display device, a display system, a moving body, and a light amount control method.

  In a moving body such as a vehicle, a display device such as a HUD (head-up display) is used as an application that allows a driver (observer) to visually recognize various information (vehicle information, warning information, navigation information, etc.) with a small amount of line of sight. ing. In such a display device, a laser light source that outputs laser beams having different wavelengths is used to form an image that is visually recognized by an observer.

  The amount of light from the laser light source varies greatly due to temperature changes, and the amount of variation varies from light source to light source. For this reason, a technique for performing light amount control (APC) by monitoring light amount fluctuations with a photodetector is known. For example, Patent Document 1 discloses the content of optimizing the current setting with respect to the semiconductor laser at the normal time and the dimming process with higher accuracy and stabilizing the light amount control in the laser projection display device.

  However, the conventional method has a problem that the light amount control range indicating the range of the current value used for the light amount control is not optimized.

  The light source device according to claim 1 includes: a light source that outputs laser light; and a control unit that controls a light amount of the laser light output from the light source, wherein the control unit outputs the laser light output from the light source. Is set based on the output from the light detector for detecting the light amount, and a light amount control range indicating a current value range used for the light amount control is set, and the light amount is controlled in the light amount control range.

  According to the present invention, it is possible to optimize a light amount control range used for light amount control.

It is a figure which shows an example of the system configuration | structure of the display system which concerns on embodiment. It is a figure which shows an example of the hardware constitutions of the display apparatus which concerns on embodiment. It is a figure which shows an example of a function structure of the display apparatus which concerns on embodiment. It is a figure which shows an example of the specific structure of the optical deflection | deviation apparatus which concerns on embodiment. It is a figure which shows an example of the specific structure of the screen which concerns on embodiment. It is a figure for demonstrating the difference in the effect | action by the difference in the magnitude relationship of an incident light beam diameter and a lens diameter in a micro lens array. It is a figure for demonstrating the correspondence of the mirror of an optical deflection | deviation apparatus, and a scanning range. It is a figure which shows an example of the scanning line locus | trajectory at the time of two-dimensional scanning. It is a figure which shows an example of the specific structure of the light source device which concerns on embodiment. It is a figure which shows an example of the scanning area | region on the screen of the laser beam inject | emitted from the light source device which concerns on embodiment. It is the figure which showed schematically an example of the structure of the light source device which concerns on embodiment. It is a figure which shows an example of a function structure of the control circuit which concerns on embodiment. It is a figure which shows the characteristic of the analog electric current value of the output light quantity from a light source element. (A) It is a figure which shows the characteristic of the output light quantity of a light source element, and an electric current digital value. (B) It is a figure which shows the characteristic of the output of an optical detector, and an electric current digital value. It is a figure which shows an example of the fluctuation | variation of the IL characteristic by control of a gain value. It is a figure which shows an example of the fluctuation | variation of the IL characteristic by control of an offset value. It is a figure which shows IL characteristic at the time of optimizing a gain value and an offset value. 5 is a flowchart illustrating an example of a light amount control method in the light source device according to the embodiment. It is a flowchart which shows an example of the search process in an electric current determination part. It is a figure which shows the IL characteristic by the 1st search offset value and the search gain value in the light source device which concerns on embodiment. It is a figure which shows the IL characteristic by the 2nd search offset value and the search gain value in the light source device which concerns on embodiment. (A) It is a figure which shows an example of a nonlinear IL characteristic. (B) It is a figure which shows an example of the regression line calculated using a nonlinear IL characteristic. It is a figure which shows an example of the calculation method of the electric current digital value of the minimum light quantity in the light source device which concerns on embodiment. It is a figure which shows an example of the calculation method of the electric current digital value of the maximum light quantity in the light source device which concerns on embodiment. It is a figure which shows an example of the abnormal point of light quantity. It is a figure which shows an example of the relationship between the regression line calculated | required using 3 points | pieces, and the IL characteristic of the light quantity actually output from a light source element, when the abnormal point of a light quantity exists. It is a figure which shows an example of the calculation method of the oscillation threshold value in the light source device which concerns on embodiment. It is a figure which shows the modification of the light quantity control method in the light source device which concerns on embodiment. It is a figure which shows an example of the IL characteristic of a different duty ratio which changed the pulse width which lights a light source element.

  Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant descriptions are omitted.

● System configuration ●
First, a system to which the light source device in each embodiment is applied will be described with reference to FIGS. 1 to 8. FIG. 1 is a diagram illustrating an example of a system configuration of a display system according to the embodiment. The display system 1 is a system that causes a viewer 3 to visually recognize a display image by projecting projection light projected from the display device 10 onto a transmission / reflection member. The display image is an image that is superimposed and displayed as a virtual image 45 in the field of view of the observer 3.

  The display system 1 is provided in, for example, a moving body such as a vehicle, an aircraft, or a ship, or a non-moving body such as an operation simulation system or a home theater system. This embodiment demonstrates the case where the display system 1 is equipped with the motor vehicle which is an example of a mobile body. The usage pattern of the display system 1 is not limited to this.

  The display system 1 is, for example, navigation information (for example, vehicle speed, route information, distance to a destination, current location name, presence / absence of an object (object) in front of the vehicle, and the like necessary for maneuvering the vehicle via the windshield 50. Marks such as position and speed limit, information such as traffic jam information, etc.) are made visible to the observer 3 (operator). In this case, the windshield functions as a transmission / reflection member that transmits part of the incident light and reflects at least part of the remaining part. The distance from the viewpoint position of the observer 3 to the windshield 50 is about several tens of cm to 1 m.

  The display system 1 includes a display device 10, a free-form curved mirror 30, and a windshield 50. The display device 10 is, for example, a head-up display device (HUD device) mounted on an automobile that is an example of a moving object. The display device 10 is arranged at an arbitrary position in accordance with the interior design of the automobile. The display device 10 may be disposed, for example, below a dashboard of an automobile. It may be embedded in the dashboard.

  The display device 10 includes a light source device 11 that outputs laser light, a light deflection device 13 that deflects laser light output from the light source device 11, and a screen 15 that diverges the laser light deflected by the light deflection device 13. . The light source device 11 is a device that irradiates laser light emitted from a light source to the outside of the device. For example, the light source device 11 may irradiate a laser beam obtained by combining laser beams of three colors of R, G, and B. The laser light emitted (output) from the light source device 11 is guided to the reflection surface of the light deflection device 13. The light source device 11 includes a semiconductor light emitting element such as an LD (Laser Diode) as a light source. The light source is not limited to this, and may include a semiconductor light emitting element such as an LED (light emitting diode).

  The light deflecting device 13 as the light deflecting unit scans the light emitted from the light source device 11 in the main scanning direction and the sub-scanning direction orthogonal to the main scanning direction, and forms the intermediate image 40 on the screen 15 as the optical element. It is a device that changes the traveling direction of laser light using MEMS (Micro Electro Mechanical Systems) or the like. The optical deflector 13 includes scanning means such as a single minute MEMS mirror that swings about two orthogonal axes, or a mirror system that includes two MEMS mirrors that swing or rotate about one axis. Configured using. The laser beam output from the optical deflecting device 13 is scanned on the screen 15. The light deflecting device 13 is not limited to the MEMS mirror, and may be configured using a polygon mirror or the like.

  The screen 15 as an optical element for diverging light is a diverging member having a function of diverging laser light at a predetermined divergence angle. The screen 15 is configured by a transmissive optical element having a light diffusing effect such as a microlens array (MLA) or a diffusing plate in the form of EPE (Exit Pupil Expander), for example. The screen 15 may be configured by a reflective optical element having a light diffusion effect such as a micromirror array. The screen 15 scans the screen 15 with the laser beam output from the light deflecting device 13, thereby forming an intermediate image 40 that is a two-dimensional image on the screen 15.

  Here, the projection method of the display device 10 is a “panel method” in which an intermediate image 40 is formed by an imaging device such as a liquid crystal panel, a DMD panel (digital mirror device panel), or a fluorescent display tube (VFD), and an output from the light source device 11. There is a “laser scanning method” in which an intermediate image 40 is formed by scanning the laser beam with a scanning unit.

  The display device 10 according to the present embodiment employs the latter “laser scanning method”. In the “laser scanning method”, light emission or non-light emission can be assigned to each pixel, so that generally a high-contrast image can be formed. The display device 10 may use a “panel method” as a projection method.

  The virtual image 45 projected on the free-form surface mirror 30 and the windshield 50 by the laser light (light beam) output from the screen 15 is enlarged from the intermediate image 40 and displayed. The free-form surface mirror 30 is designed and arranged so as to cancel out the inclination, distortion, misalignment and the like of the image due to the curved shape of the windshield 50. The free-form surface mirror 30 may be installed to be rotatable about a predetermined rotation axis. As a result, the free-form surface mirror 30 can adjust the reflection direction of the laser beam (light beam) output from the screen 15 and change the display position of the virtual image 45.

  Here, the free-form surface mirror 30 is designed using existing optical design simulation software so as to have a constant light condensing power so that the imaging position of the virtual image 45 becomes a desired position. The display device 10 sets the condensing power of the free-form surface mirror 30 so that the virtual image 45 is displayed at a position (depth position) of 1 m or more and 30 m or less (preferably 10 m or less) from the viewpoint position of the observer 3. To do. Note that the free-form surface mirror 30 may be a concave mirror or other element having a condensing power. The free-form curved mirror 30 is an example of an imaging optical system.

  The windshield 50 is a transmission / reflection member having a function (partial reflection function) of transmitting a part of the laser light (light beam) and reflecting at least a part of the remaining part. The windshield 50 functions as a semi-transparent mirror that allows the observer 3 to visually recognize the scenery in front and the virtual image 45. The virtual image 45 is image information for causing the observer 3 to visually recognize vehicle information (speed, travel distance, etc.), navigation information (route guidance, traffic information, etc.), warning information (collision warning, etc.), and the like. The transmission / reflection member may be a front windshield provided separately from the windshield 50. The windshield 50 is an example of a reflecting member.

  The virtual image 45 may be displayed so as to overlap the scenery in front of the windshield 50. Further, the windshield 50 is not flat but curved. Therefore, the imaging position of the virtual image 45 is determined by the curved surface of the free-form surface mirror 30 and the windshield 50. The windshield 50 may use a semi-transmission mirror (combiner) as an individual transmission reflection member having a partial reflection function.

  With such a configuration, the laser light (light beam) output from the screen 15 is projected toward the free-form surface mirror 30 and reflected by the windshield 50. The observer 3 can visually recognize the virtual image 45 in which the intermediate image 40 formed on the screen 15 is enlarged by the light reflected by the windshield 50.

● Hardware configuration ●
FIG. 2 is a diagram illustrating an example of a hardware configuration of the display device according to the embodiment. 2 may be added or deleted as necessary.

  The display device 10 includes a controller 17 for controlling the operation of the display device 10. The controller 17 is a substrate or an IC chip mounted inside the display device 10. The controller 17 includes an FPGA (Field-Programmable Gate Array) 1001, a CPU (Central Processing Unit) 1002, a ROM (Read Only Memory) 1003, a RAM (Random Access Memory) 1004, an I / F (Interface) 1005, and a bus line 1006. Including.

  The FPGA 1001 is an integrated circuit that can be changed by the designer of the display device 10. The CPU 1002 is an integrated circuit that performs processing for controlling the entire display device 10. The ROM 1003 is a storage device that stores a program for controlling the CPU 1002. The RAM 1004 is a storage device that functions as a work area for the CPU 1002. An I / F 1005 is an interface for communicating with an external device. The I / F 1005 is connected to a CAN (Controller Area Network) of an automobile, for example.

  The LD 1007 is, for example, a semiconductor light emitting element that constitutes a part of the light source device 11. The MEMS 1009 is a device that constitutes a part of the light deflection apparatus 13 and displaces the scanning mirror. The motor 1011 is an electric motor that rotates the rotation shaft of the free-form curved mirror 30.

● Function structure ●
FIG. 3 is a diagram illustrating an example of a functional configuration of the display device according to the embodiment. Functions realized by the display device 10 include a vehicle information reception unit 171, an external information reception unit 172, an image generation unit 173, and an image display unit 174.

  The vehicle information receiving unit 171 has a function of receiving automobile information (information such as speed and travel distance) from CAN or the like. The vehicle information receiving unit 171 is realized by the processing of the I / F 1005 and the CPU 1002 illustrated in FIG. 2, a program stored in the ROM 1003, and the like.

  The external information receiving unit 172 has a function of receiving information outside the vehicle (position information from the GPS, route information from the navigation system, traffic information, etc.) from the external network. The external information receiving unit 172 is realized by the processing of the I / F 1005 and the CPU 1002 illustrated in FIG. 2, a program stored in the ROM 1003, and the like.

  The image generation unit 173 has a function of generating image information for displaying the intermediate image 40 and the virtual image 45 based on information input by the vehicle information reception unit 171 and the external information reception unit 172. The image generation unit 173 is realized by the processing of the CPU 1002 illustrated in FIG. 2 and the program stored in the ROM 1003.

  The image display unit 174 forms an intermediate image 40 on the screen 15 based on the image information generated by the image generation unit 173, and projects the laser light (light beam) constituting the intermediate image 40 toward the windshield 50. The virtual image 45 is displayed. The image display unit 174 is realized by the processing of the CPU 1002 and the FPGA 1001 illustrated in FIG. 2, the program stored in the ROM 1003, and the like.

The image display unit 174 includes a control unit 175, an intermediate image forming unit 176, and a projection unit 177.
The control unit 175 generates a control signal for controlling operations of the light source device 11 and the light deflection device 13 in order to form the intermediate image 40. In addition, the control unit 175 generates a control signal for controlling the operation of the free-form curved mirror 30 in order to display the virtual image 45 at a predetermined position.

  The intermediate image forming unit 176 forms the intermediate image 40 on the screen 15 based on the control signal generated by the control unit 175. The projection unit 177 projects the laser light constituting the intermediate image 40 onto a transmission / reflection member (the windshield 50 or the like) in order to form the virtual image 45 that is visually recognized by the observer 3.

● Light deflection device ●
FIG. 4 is a diagram illustrating an example of a specific configuration of the light deflection apparatus according to the embodiment. The optical deflection device 13 is a MEMS mirror manufactured by a semiconductor process, and includes a mirror 130, a meandering beam portion 132, a frame member 134, and a piezoelectric member 136. The light deflection device 13 is an example of a scanning unit.

  The mirror 130 has a reflection surface that reflects the laser beam output from the light source device 11 toward the screen 15. The light deflecting device 13 forms a pair of meandering beam portions 132 with the mirror 130 interposed therebetween. The meandering beam portion 132 has a plurality of folded portions. The folded portion is composed of first beam portions 132a and second beam portions 132b that are alternately arranged. The meandering beam portion 132 is supported by the frame member 134. The piezoelectric member 136 is disposed so as to connect the adjacent first beam portion 132a and the second beam portion 132b. The piezoelectric member 136 applies different voltages to the first beam portion 132a and the second beam portion 132b, and generates warpage in each of the beam portions 132a and 132b.

  Thereby, the adjacent beam parts 132a and 132b bend in different directions. The mirror 130 rotates in the vertical direction about the left-right axis as the deflection is accumulated. With such a configuration, the optical deflecting device 13 can perform optical scanning in the vertical direction with a low voltage. Optical scanning in the horizontal direction with the vertical axis as the center is performed by resonance using a torsion bar or the like connected to the mirror 130.

● Screen ●
FIG. 5 is a diagram illustrating an example of a specific configuration of the screen according to the embodiment. The screen 15 forms an image of the laser light output from the LD 1007 constituting a part of the light source device 11. The screen 15 is a diverging member that diverges at a predetermined divergence angle. The screen 15 is an example of an optical element. The screen 15 shown in FIG. 5 has a microlens array structure in which a plurality of hexagonal microlenses 150 are arranged without gaps. The lens diameter of the microlens 150 (distance between two opposing sides) is about 200 μm. The screen 15 can arrange a plurality of microlenses 150 at a high density by making the shape of the microlenses 150 hexagonal.

  Note that the shape of the microlens 150 is not limited to a hexagon, and may be, for example, a quadrangle, a triangle, or the like. Further, the structure in which the plurality of microlenses 150 are regularly arranged is illustrated, but the arrangement of the microlenses 150 is not limited to this, and for example, the centers of the microlenses 150 are eccentric to each other and irregularly arranged. It is good also as an arrangement. When such an eccentric arrangement is adopted, the microlenses 150 have different shapes.

  FIG. 6 is a diagram for explaining the difference in action due to the difference in the magnitude relationship between the incident light beam diameter and the lens diameter in the microlens array. In FIG. 6A, the screen 15 is constituted by an optical plate 151 in which microlenses 150 are arranged. When scanning the incident light 152 on the optical plate 151, the incident light 152 is diverged by the microlens 150 and becomes divergent light 153. The screen 15 can diverge the incident light 152 at a desired divergence angle 154 by the structure of the microlens 150. This divergence angle 154 has a corresponding relationship with the curvature of the microlens 150. The period 155 of the microlens 150 is designed to be larger than the diameter 156 a of the incident light 152. Thereby, the screen 15 suppresses generation | occurrence | production of interference noise, without causing interference between lenses.

  FIG. 6B shows an optical path of diverging light when the diameter 156 b of the incident light 152 is twice as large as the period 155 of the microlens 150. Incident light 152 is incident on two microlenses 150a and 150b to generate diverging light 157 and 158, respectively. At this time, since two divergent lights exist in the region 159, light interference may occur. When this interference light enters the observer's eyes, it is visually recognized as interference noise.

  Considering the above, in order to reduce interference noise, the period 155 of the microlens 150 is designed to be larger than the diameter 156 of the incident light. In addition, although FIG. 6 demonstrated in the form of the convex lens, the same effect shall also be obtained in the form of a concave lens.

  FIG. 7 is a diagram for explaining the correspondence between the mirror of the optical deflector and the scanning range. The light emission intensity, lighting timing, and optical waveform of each light source element of the light source device 11 are controlled by the FPGA 1001. As shown in FIG. 7, the laser light output from each light source element and combined in the optical path is two-dimensionally deflected around the α axis and the β axis by the mirror 130 of the optical deflector 13 and scanned through the mirror 130. The screen 15 is irradiated as light. That is, the screen 15 is two-dimensionally scanned by main scanning and sub-scanning by the light deflecting device 13.

  The scanning range is the entire range that can be scanned by the light deflecting device 13. Scanning light scans the scanning range of the screen 15 in the main scanning direction (X-axis direction) at a fast frequency of about 2 to 40,000 Hz, and in the sub-scanning direction at a slow frequency of about several tens of Hz. One-way scanning is performed in the (Y-axis direction). That is, the light deflecting device 13 performs a raster scan on the screen 15. In this case, the display device 10 can perform drawing or display of a virtual image for each pixel by performing light emission control of each light source element according to the scanning position (scanning light position).

The time for drawing one screen, that is, the scanning time for one frame (one cycle of two-dimensional scanning) is
As described above, since the sub-scanning cycle is several tens of Hz, it is several tens of msec. For example, when the main scanning period is 20000 Hz and the sub-scanning period is 50 Hz, the scanning time for one frame is 20 msec.

  FIG. 8 is a diagram illustrating an example of a scanning line locus during two-dimensional scanning. As shown in FIG. 8, the screen 15 has an image area 61 (effective scanning area) on which the intermediate image 40 is drawn (irradiated with light modulated according to image data), and a frame area surrounding the image area 61. 62.

  The scanning range is a range in which the image area 61 and a part of the frame area 62 on the screen 15 (a part near the outer edge of the image area 61) are combined. In FIG. 8, the trajectory of the scanning line in the scanning range is indicated by a zigzag line. In FIG. 8, the number of scanning lines is less than the actual number for convenience.

  As described above, the screen 15 is composed of a transmissive optical element having a light diffusion effect, such as the microlens array 150. The image area 61 does not have to be a rectangle or a plane, but may be a polygon or a curved surface. The screen 15 may be a flat plate or a curved plate that does not have a light diffusion effect. Further, the screen 15 may be a reflective optical element having a light diffusion effect, such as a micromirror array, according to the device layout.

  The screen 15 includes a synchronization detection system 60 including a light receiving element in a peripheral region (a part of the frame region 62) of the image region 61 in the scanning range. In FIG. 8, the synchronization detection system 60 is disposed at the corner of the image area 61 on the −X side and the + Y side. The synchronization detection system 60 detects the operation of the optical deflecting device 13 and outputs a synchronization signal for determining the scan start timing and the scan end timing to the FPGA 1001.

● Light source device ●
Configuration Next, the light source device 11 according to the present embodiment will be described with reference to FIGS. 9 to 29. First, the configuration of the light source device 11 according to the present embodiment will be described with reference to FIGS. 9 to 12.

  FIG. 9 is a diagram illustrating an example of a specific configuration of the light source device according to the embodiment. The light source device 11 includes light source elements 111 (r), 111 (g), and 111 (b) (hereinafter referred to as the light source element 111 when it is not necessary to distinguish them), coupling lenses 112 (r) and 112 ( g), 112 (b) (hereinafter referred to as coupling lens 112 when it is not necessary to distinguish), apertures 113 (r), 113 (g), 113 (b) (hereinafter, it is not necessary to distinguish between them). In some cases, it is referred to as an aperture 113.), a mirror 114, light combining elements 115 and 116, a light branching element 117, and a photodetector 119.

  The three-color (R, G, B) light source elements 111 (r), 111 (g), 111 (b) are, for example, LDs (laser diodes) each having a single or a plurality of light emitting points. The light source elements 111 (r), 111 (g), 111 (b) output laser beams (light beams) having different wavelengths λR, λG, λB (for example, λR = 650 nm, λG = 515 nm, λB = 450 nm) ( Eject). The light source device 11 includes a plurality of light source elements 111 (111 (r), 111 (g), 111 (b)) that output light beams having different wavelengths in order to generate colors necessary for an image. The circuit board for driving the light source element 111 is common in that each light source element 111 (r), 111 (g), 111 (b) is arranged on the same surface of the light source device 11 in consideration of downsizing and low cost. It becomes. The light source element 111 shown in FIG. 9 has a configuration corresponding to the LD 1007 shown in FIG.

  Each output light beam is coupled by the corresponding coupling lens 112 (r), 112 (g), 112 (b). Since the laser light (light beam) output from the light source element 111 is diffused light, it is condensed by the corresponding coupling lens 112 to become parallel light. Since the semiconductor laser has high directivity but has a spread at the emission end, it gradually attenuates. The light source device 11 converts the emitted light beam into parallel light using the coupling lens 112 in order to reduce the loss of the emitted light beam.

  Each coupled light beam is shaped by the corresponding aperture 113 (r), 113 (g), 113 (b). The aperture 113 has a shape (for example, a circle, an ellipse, a rectangle, a square, or the like) according to a predetermined condition such as a light beam divergence angle. The light beam shaped by the aperture 113 is combined using the mirror 114 and the two combining elements 115 and 116.

  The mirror 114 deflects the light beam output from the light source element 111 (b) and guides it to the light branching element 117. The light combining element 115 combines the light beam guided by the mirror 114 and the light beam output from the light source element 111 (g). The light combining element 116 further combines the light beam combined by the light combining element 115 and the light beam output from the light source element 111 (r). The light synthesizing elements 115 and 116 are plate-shaped or prism-shaped dichroic mirrors, and reflect or transmit a light beam according to a wavelength, and synthesize it into one light beam. The light beams output from the light source elements 111 (r), 111 (g), and 111 (b) are combined by the light combining element 115 and the light combining element 116, and follow the same optical path.

  A part of the incident light incident on the light branching element 117 is transmitted through the light branching element 117, and the other part, that is, at least a part of the remaining part is reflected by the light branching element 117. That is, the light beam combined by the light combining element 116 is branched into transmitted light and reflected light by the light branching element 117. The light branching element 117 may be disposed on the optical path between the light combining element 116 and the light deflecting device 13.

  The transmitted light is applied to the light deflecting device 13 and used for image drawing and virtual image display on the screen 15. That is, the transmitted light is used as image light. On the other hand, the reflected light is applied to the photodetector 119 and used as monitor light for adjusting the color and brightness of the virtual image.

  The photodetector 119 detects the amount of monitor light branched by the light branching element 117. In order to reduce the size of the light source device 11, the photodetector 119 preferably detects laser light (light flux) output from the plurality of light source elements 111 with one element.

  In the light source device 11 using a plurality of laser light sources having different wavelengths, the expression of the color of the virtual image to be displayed is based on the white balance that realizes white as in the case of the liquid crystal display. Must be set to Since the amount of laser light (light flux) output from each light source element 111 varies due to environmental fluctuations such as temperature changes, the amount of light for realizing white balance also changes. Therefore, the light source device 11 detects the light amount fluctuation of the laser light (light beam) output from each light source element 111 by the photodetector 119 and controls the light amount of the laser light (light beam) output from the light source element 111 (APC). I do. The light source device 11 branches a part of the laser light combined by the combining element 116 to the photodetector 119 by the light branching element 117. The light source device 11 uses the branching surface of the light branching element 117 as the incident surface of the laser beam (light beam), guides the laser light reflected by the light branching element 117 to the photodetector 119, and causes the light branching element 117 to be used. An optical branching element 117 is arranged so as to guide the transmitted laser light to the optical deflecting device 13.

  Here, the timing of the light amount control performed by the light source device 11 will be described with reference to FIG. FIG. 10 is a diagram illustrating an example of a scanning area on the screen of the laser light emitted from the light source device according to the embodiment.

  The display device 10 deflects the laser light emitted from the light source device 11 by the light deflection device 13 and scans the screen 15 two-dimensionally. In the light amount control (APC), the light source device 11 uses the monitor light detected by the photodetector 119 to determine a digital current value for the light source element 111 to output a desired light amount. Need to be lit for a predetermined period. Further, the light source device 11 needs to light the light source element 111 with a plurality of light amounts in order to improve the accuracy of light amount control (APC). Therefore, as shown in FIG. 10, the scanning region 230 on the screen 15 has a light amount control region (non-image region) 210 at a position different from the image forming region 220 for forming an image with image light. The image forming area 220 is the same as the image area 61 as shown in FIG. The light source device 11 performs light amount control (APC) of the laser light output from each light source element 111 at a timing when the light deflection device 13 scans the light amount control region 210 with the image light.

  When the light amount control is performed in the image forming region 220 that forms an image to be visually recognized by the observer 3, color unevenness occurs in the formed image according to the change in the light amount. Therefore, as shown in FIG. 10, the display device 10 separates the light amount control region 210 for turning on the light amount control laser light and the image forming region 220, and transmits the light amount control laser light from the image forming region 220. By shielding the light, it is possible to suppress the occurrence of color unevenness in the image formed in the image forming region 220.

  FIG. 11 is a diagram schematically illustrating an example of the configuration of the light source device according to the embodiment. The light source device 11 includes a control circuit 300 in addition to the configuration shown in FIG. The control circuit 300 is connected to the light source element 111 and the photodetector 119 via the bus line 307. The control circuit 300 is a circuit board or an IC chip mounted inside the light source device 11. The control circuit 300 controls the amount of laser light output from the light source element 111 based on the output from the photodetector 119.

  The control circuit 300 includes an FPGA 301, a CPU 302, a ROM 303, a RAM 304, an I / F 305, a driver 306, and a bus line 307. The FPGA 301 is an integrated circuit that can be changed by the designer of the light source device 11. The driver 306 generates a drive signal for the light source element 111 in accordance with a control signal from the FPGA 301. The CPU 302 is an integrated circuit that performs processing for controlling the entire light source device 11. The ROM 303 is a storage device that stores a program for controlling the CPU 302. For example, the light source device 11 realizes the light amount control method according to the present invention by the CPU 302 or the FPGA 301 executing the program according to the present invention. Note that the light amount control method according to the present invention may be realized by the CPU 1002 or the FPGA 1001 illustrated in FIG. 2 executing the program according to the present invention. The RAM 304 is a storage device that functions as a work area for the CPU 302. The I / F 305 is an interface for communicating with the photodetector 119.

  Next, functions realized by the control circuit 300 included in the light source device 11 according to the embodiment will be described with reference to FIG. FIG. 12 is a diagram illustrating an example of a functional configuration of the control circuit according to the embodiment. 12 includes a detection unit 310, a light amount calculation unit 330, a current determination unit 350, a drive control unit 370, a storage / reading control unit 390, and a storage unit 3000. The detection unit 310, the light amount calculation unit 330, the current determination unit 350, the drive control unit 370, the storage / reading control unit 390, and the storage unit 3000 are realized by the processing of the FPGA 301, the driver 306, and the CPU 302 illustrated in FIG. . Note that the functions of the detection unit 310, the light amount calculation unit 330, the current determination unit 350, the drive control unit 370, the storage / reading control unit 390, and the storage unit 3000 are the functions of a dedicated IC (for example, as shown in FIG. 2). It may be realized by the controller 17) shown.

  The detection unit 310 has a function of detecting timing for performing light amount control (APC) of laser light output from each light source element 111 by the light source device 11. For example, the detection unit 310 detects a scanning period for the light amount control region 210 illustrated in FIG. 10 based on a synchronization signal from the light deflecting device 13. In addition, the detection unit 310 may store in advance the scanning cycle of the light deflecting device 13 and detect that it is the scanning cycle of the light amount control region 210. The detection unit 310 is mainly realized by the processing of the FPGA 301, the CPU 302, and the I / F 305 illustrated in FIG.

  The light quantity calculation unit 330 is a function that calculates the average light quantity of the laser light (light beam) detected by the photodetector 119. For example, the light amount calculation unit 330 calculates the average light amount of the laser light output from the light source element 111 based on the detection signal output from the photodetector 119. The light amount calculation unit 330 calculates the average light amount of laser light output from each of the light source elements 111. The light quantity calculation unit 330 is mainly realized by the processing of the FPGA 301, the CPU 302, and the I / F 305 illustrated in FIG.

  The current determining unit 350 has a function of determining an offset value and a gain value for setting a light amount control range and a current digital value for outputting a laser beam having a predetermined light amount from the light source element 111 by light amount control (APC). It is. The current determination unit 350 is realized mainly by the processing of the FPGA 301 and the CPU 302 shown in FIG. The current determination unit 350 is an example of a current determination unit.

  The drive control unit 370 has a function of controlling the driving of the light source element 111 based on the parameter determined by the current determination unit 350. The drive control unit 370 is mainly realized by the processing of the FPGA 301 and the CPU 302 shown in FIG. The drive control unit 370 is an example of a drive control unit. The drive control unit 370 includes a conversion unit 371, an offset control unit 372, and a gain control unit 373.

  The conversion unit 371 has a function of converting the current digital value determined by the current determination unit 350 into an analog current value for driving the light source element 111. The analog current value converted by the conversion unit 371 is an example of the output current value of the laser beam output from the light source element 111.

  The offset control unit 372 has a function of offsetting the current value of the light source element 111 based on the offset value set by the current determination unit 350.

  The gain control unit 373 has a function of amplifying the current value of the light source element 111 based on the gain value set by the current determination unit 350.

  The storage / reading control unit 390 has a function of storing various data in the storage unit 3000 or reading various data from the storage unit 3000. The storage / reading control unit 390 is realized mainly by the processing of the FPGA 301 and the CPU 302 shown in FIG. The storage unit 3000 is mainly realized by the FPGA 301, the CPU 302, and the ROM 303 illustrated in FIG.

Light quantity control Next, the light quantity control by the light source device 11 will be described with reference to FIGS. 13 to 17.

  FIG. 13 is a diagram showing the characteristics of the amount of light output from the light source element and the analog current value. FIG. 13 shows an example of the current value characteristic (IL characteristic) of the output light quantity of the light source element whose absolute maximum rating is 50 mW. As shown in FIG. 13, the output light quantity of the light source element 111 has different characteristics before and after the oscillation threshold current (100 mA), hardly emits light at a current value smaller than the oscillation threshold value, and has linearity at a current value larger than the oscillation threshold value. high. The light source device 11 controls the amount of light output from the light source element 111 by using a drive control unit 370 as shown in FIG. The light source device 11 sets a digital value (hereinafter referred to as a current digital value) in the drive control unit 370 instead of an analog value (hereinafter referred to as an analog current value). For example, when the drive control unit 370 processes the current value with 10 bits, the analog current value 0 mA corresponds to 0 digit, and the analog current value 300 mA corresponds to 1023 digit, an IL characteristic as shown in FIG. 14A is obtained. The light source device 11 causes the light source element 111 to emit light with a plurality of light amounts in the light amount control region 210 as illustrated in FIG. 10 and obtains an output from the photodetector 119, thereby obtaining a light amount necessary for image drawing and virtual image display ( The current digital value that is the output value) is searched.

  Part of the laser light output from the light source element 111 reaches the photodetector 119. The laser beam incident on the photodetector 119 is processed with a digital value as shown in FIG. Therefore, the light source device 11 acquires the output value of the light detector 119 as shown in FIG. It can convert into the light source light quantity as shown to Fig.14 (a). The light amount calculation unit 330 calculates the light amount of the laser light output from the light source element 111 from the output value output from the light detector 119 based on the relationship between the output of the light detector 119 and the light source light amount. Note that the relationship (approximate expression) between the output of the photodetector 119 and the light amount of the light source is stored in the storage unit 3000 in advance.

  The resolution per 1 digit of the current digital value is about 0.3 mA / digit, and the amount of light above the oscillation threshold current is 0.07 mW / digit. When the ambient illuminance is low, the upper limit of the amount of light output from the light source element 111 required by the display device 10 that is an in-vehicle device such as HUD is, for example, 10 mW. In this case, an effective current digital value (hereinafter referred to as an effective current digital value) ranges from a digital current value (340 digit) corresponding to the oscillation threshold current to a digital current value (480 digit) corresponding to the upper limit value (10 mW) of the output light amount. Will be called). The range of the effective current digital value is a range in which the light amount control can be performed (hereinafter referred to as a light amount control range).

  Here, generally, the gradation of an image is expressed in 256 levels. On the other hand, since the light quantity control range is 140 digits (340 to 480 digits), it is difficult to perform smooth gradation expression. Further, the maximum current value (maximum analog current value) that can be output by the light source element is designed to be 300 mA or more in order to provide a margin for the current value necessary for image drawing. When the analog current value corresponding to the current digital value is increased, the range of the control current value per 1 digit of the digital value is increased, so that the resolution of the light amount control is decreased. Accordingly, the analog current value corresponding to 1023 digits becomes high and the light quantity control range becomes 140 digits or less, so that the resolution of the light quantity control is further reduced.

  Therefore, as a method for increasing the resolution of the light amount control, there is a method for setting the gain value and the offset value for driving the light source element 111 to optimum values. Here, the relationship between the analog current value, the current digital value, the gain value, and the offset value is expressed as the following Expression 1. As shown in Expression 1, the light source device 11 outputs an output from the light source element 111 even if the same current digital value is input by controlling an offset value and a gain value set to drive the light source element 111. The analog current value (output current value) of the laser beam to be changed can be changed.

  Analog current value = current digital value × gain value + offset value (Equation 1)

  Further, as shown in Expression 1, the light source device 11 can multiply the output current value (analog current value) corresponding to the current digital value by g by controlling the gain value. FIG. 15 is a diagram illustrating an example of variation in IL characteristics due to gain value control. FIG. 15 shows an example in which a current value capable of outputting a light amount of 10 mW is associated with a current digital value of 1023 digits. The IL characteristic shown in FIG. 15 is obtained by doubling the gain value of the IL characteristic as shown in FIG. As shown in FIG. 15, since the current digital value corresponding to the light amount of the oscillation threshold is set to 730 digits and the current digital value corresponding to the light amount of 10 mW is set to 1023 digits, the light amount control range is about 300 digits. Thus, the light source device 11 can improve the resolution of the light amount control by controlling the gain value.

  Further, as shown in Expression 1, the light source device 11 can increase the output current value (analog current value) with respect to the current digital value by a certain amount by controlling the offset value. FIG. 16 is a diagram illustrating an example of variation in IL characteristics due to offset value control. FIG. 16 shows an example in which the current value for outputting the light amount of 1 mW is offset when the minimum light amount necessary for image drawing and virtual image display is 1 mW. The IL characteristic shown in FIG. 16 is obtained by shifting the IL characteristic as shown in FIG. 14A in a direction in which the current digital value is low. Since the light amount of the laser light output from the light source element 111 is stabilized at a current value equal to or greater than the oscillation threshold value, the light amount control (current value control) uses a light amount equal to or greater than the oscillation threshold value, and the light amount control (current value) equal to or less than the oscillation threshold value Control) is not required. Therefore, as illustrated in FIG. 16, the light source device 11 offsets the digital current value so that the current digital value for outputting the minimum light amount (1 mW) approaches zero.

  As described above, by combining the optimum values of the gain value and the offset value, the light source device 11 can acquire an ideal IL characteristic as shown in FIG. Here, the resolution of the light amount control is such that the current value corresponding to the 10-bit maximum value 1023 digit is the current value (Imax_n) that outputs the maximum light amount, and the current value corresponding to 0 digit is the current value (Imax_0) that outputs the minimum light amount. ) Is the highest. If the resolution of the light quantity control is high, the accuracy of the light quantity control is also high, so that the light source device 11 can set the white balance appropriately. In the case of the IL characteristic as shown in FIG. 17, the range of 0 digit to 1023 digit is the light amount control range, so that the control accuracy is improved by improving the light amount control resolution. The light source device 11 can increase the resolution of the light amount control by controlling the gain value and the offset value before searching for the current digital value for the light amount necessary for image drawing and virtual image display.

  In the present embodiment, the light source device 11 sets the offset value and the gain value to optimum values so as to cover the dynamic range of the output light amount of the light source element 111 in accordance with environmental changes such as temperature changes, thereby controlling the light amount. It is an object of the present invention to reduce the number of trials required for light amount control by optimizing the light amount control range used for the above.

Setting of light quantity control range Next, a method of setting the light quantity control range in the present embodiment will be described with reference to FIGS. A display device 10 such as a HUD changes an output light amount of the light source element 111 in order to display an image with appropriate luminance with respect to various environmental illuminances, or changes an IL characteristic of the light source due to a temperature variation or the like. Appropriate gain and offset values must be determined and the light intensity control range set. Here, when variation, aging degradation, and the like are included, it is more accurate to search for an appropriate value each time than to hold an optimum value as a table in advance. However, when the search for the gain value and the offset value takes time and processing is delayed, the resolution of the light amount control is deteriorated, and the contrast and color of the image cannot be expressed. Therefore, the light source device 11 needs to perform a quick search and set an appropriate light amount control range.

  FIG. 18 is a flowchart illustrating an example of a light amount control method in the light source device according to the embodiment. In step S101, when the detection unit 310 of the light source device 11 detects the timing of light amount control (APC), the process proceeds to step S102. Specifically, when the detection unit 310 detects the scanning period for the light amount control region 210 shown in FIG. 10 based on the synchronization signal from the light deflecting device 13, the detection unit 310 detects the light amount control timing. In addition, the detection unit 310 may store the scanning cycle of the light deflecting device 13 in advance and detect that it is the light amount control timing when it is detected that it is the scanning cycle of the light amount control region 210. On the other hand, the light source device 11 repeats the process of step S101 until the detection unit 310 detects that the light amount control timing is reached.

  In step S <b> 102, the current determination unit 350 of the light source device 11 performs a light amount control range search process when the detection unit 310 detects the light amount control timing.

  Here, the details of the light amount control range search process in the current determination unit 350 will be described. FIG. 19 is a flowchart illustrating an example of search processing in the current determination unit. As shown in Equation 1, it can be seen that the gain value contributes to the current digital value, and the offset value is independent of the current digital value. Therefore, an appropriate value is obtained for the gain value from one IL characteristic, and an appropriate value is obtained for the offset value from the difference between the two IL characteristics. The search for the appropriate value is performed, for example, by acquiring IL characteristics of different gain values and offset values in the non-image region 210 for determining the light amount, and calculating the current digital values of the minimum light amount and the maximum light amount and their inclinations. Done.

  First, in step S201, the current determination unit 350 sets the first search offset value α1 and the search gain value β1, and in step S202, the current determination unit 350 sets the first search offset value. Using the value α1 and the search gain value β1, the light source element 111 is caused to emit light with the current digital value I1 so that the light amount is equal to or greater than the oscillation threshold. Specifically, the current determination unit 350 determines the current digital value I1 so that the light amount is equal to or greater than the oscillation threshold. The conversion unit 371 of the drive control unit 370 converts the current digital value I1 into an analog current value for driving the light source element 111. The offset control unit 372 of the drive control unit 370 offsets the current value of the light source element 111 based on the first search offset value α1. The gain control unit 373 of the drive control unit 370 amplifies the current value of the light source element 111 based on the search gain value β1. Then, the drive control unit 370 causes the light source element 111 to emit light using the set parameters.

  In step S <b> 203, the current determination unit 350 detects the amount of light output by the photodetector 119. Specifically, the photodetector 119 detects the laser beam of the light source element 111 emitted in the process of step S202. The light amount calculation unit 330 calculates the average light amount of the monitor light detected by the photodetector 119. For example, the light amount calculation unit 330 detects the output signal of the light detector 119, and based on the relationship between the output of the light detector 119 stored in the storage unit 300 and the light source light amount, the output signal of the light detector 119 is output. The output value is converted into the amount of monitor light. Then, the current determination unit 350 detects the amount of light output by the light detector 119 calculated by the light amount calculation unit 330.

  In step S204, the current determination unit 350 uses the first search offset value α1 and the search gain value β1 set by the process in step S201 to set the current digital value I1 so that the light amount is equal to or greater than the oscillation threshold. Causes the light source element 111 to emit light with a different current digital value I2. Specifically, the current determination unit 350 determines the current digital value I2 so that the light amount is equal to or greater than the oscillation threshold. The conversion unit 371 of the drive control unit 370 converts the current digital value I2 into an analog current value for driving the light source element 111. The offset control unit 372 of the drive control unit 370 offsets the current value of the light source element 111 based on the first search offset value α1. The gain control unit 373 of the drive control unit 370 amplifies the current value of the light source element 111 based on the search gain value β1. Then, the drive control unit 370 causes the light source element 111 to emit light using the set parameters.

  In step S <b> 205, the current determination unit 350 detects the amount of light output by the photodetector 119. Specifically, the photodetector 119 detects the laser light of the light source element 111 emitted in the process of step S204. The light amount calculation unit 330 calculates the average light amount of the monitor light detected by the photodetector 119. For example, the light amount calculation unit 330 detects the output signal of the light detector 119, and based on the relationship between the output of the light detector 119 stored in the storage unit 300 and the light source light amount, the output signal of the light detector 119 is output. The output value is converted into the amount of monitor light. Then, the current determination unit 350 detects the amount of light output by the light detector 119 calculated by the light amount calculation unit 330.

  In step S206, the current determination unit 350 calculates a current digital value (Imin_1) corresponding to the minimum light amount and a current digital value (Imax_1) corresponding to the maximum light amount. Here, Imin_1 is an example of a first minimum light quantity digital value, and Imax_1 is an example of a maximum light quantity digital value. Specifically, first, the current determination unit 350 increases the light amount between the light amount in the current digital value I1 detected in the process of step S204 and the light amount in the current digital value I2 detected in the process of step S205. An amount (hereinafter referred to as a first increase amount) is calculated. When the maximum light amount in image drawing and virtual image display is 40 mW, the current determination unit 350 converts the output value of the photodetector 119 into the light source light amount, and obtains a regression line as shown in FIG. Then, the current determination unit 350 calculates the current digital value Imin_1 with the minimum light amount and the current digital value Imax_1 with the maximum light amount.

  Furthermore, in step S207, the current determination unit 350 sets a second search offset value α2 and a search gain value β1. In step S208, the current determination unit 350 uses the set second search offset value α2 and search gain value β1 to set the light source element 111 with the current digital value I1 so that the light amount is equal to or greater than the oscillation threshold. Make it emit light. Specifically, the current determination unit 350 determines the current digital value I1 so that the light amount is equal to or greater than the oscillation threshold. The conversion unit 371 of the drive control unit 370 converts the current digital value I1 into an analog current value for driving the light source element 111. The offset control unit 372 of the drive control unit 370 offsets the current value of the light source element 111 based on the second search offset value α2. The gain control unit 373 of the drive control unit 370 amplifies the current value of the light source element 111 based on the search gain value β1. Then, the drive control unit 370 causes the light source element 111 to emit light using the set parameters.

  In step S209, the current determining unit 350 detects the amount of light output by the photodetector 119. Specifically, the photodetector 119 detects the laser beam of the light source element 111 emitted in the process of step S208. Then, the current determination unit 350 detects the output light amount output from the photodetector 119. The light amount calculation unit 330 calculates the average light amount of the monitor light detected by the photodetector 119. For example, the light amount calculation unit 330 detects the output signal of the light detector 119, and based on the relationship between the output of the light detector 119 stored in the storage unit 300 and the light source light amount, the output signal of the light detector 119 is output. The output value is converted into the amount of monitor light. Then, the current determination unit 350 detects the amount of light output by the light detector 119 calculated by the light amount calculation unit 330.

  In step S210, the current determination unit 350 uses the second search offset value α2 and the search gain value β1 set by the process in step S207 to set the current digital value I1 to a light amount that is equal to or greater than the oscillation threshold. Causes the light source element 111 to emit light with a different current digital value I2. Specifically, the current determination unit 350 determines the current digital value I2 so that the light amount is equal to or greater than the oscillation threshold. The conversion unit 371 of the drive control unit 370 converts the current digital value I2 into an analog current value for driving the light source element 111. The offset control unit 372 of the drive control unit 370 offsets the current value of the light source element 111 based on the second search offset value α2. The gain control unit 373 of the drive control unit 370 amplifies the current value of the light source element 111 based on the search gain value β1. Then, the drive control unit 370 causes the light source element 111 to emit light using the set parameters.

  In step S <b> 211, the current determination unit 350 detects the amount of light output by the photodetector 119. Specifically, the photodetector 119 detects the laser light of the light source element 111 emitted in the process of step S204. The light amount calculation unit 330 calculates the average light amount of the monitor light detected by the photodetector 119. For example, the light amount calculation unit 330 detects the output signal of the light detector 119, and based on the relationship between the output of the light detector 119 stored in the storage unit 300 and the light source light amount, the output signal of the light detector 119 is output. The output value is converted into the amount of monitor light. Then, the current determination unit 350 detects the amount of light output by the light detector 119 calculated by the light amount calculation unit 330.

  In step S212, the current determination unit 350 calculates a current digital value Imin_2 corresponding to the minimum light amount and a current digital value Imax_2 corresponding to the maximum light amount. Here, Imin_2 is an example of the second minimum light quantity digital value. Specifically, the current determination unit 350 obtains a regression line as shown in FIG. 21 as in the case of step S204. Then, the current determination unit 350 calculates the current digital value Imin_2 with the minimum light amount and the current digital value Imax_2 with the maximum light amount.

  In step S213, the current determination unit 350 determines that the current digital value (Imax_0) corresponding to the minimum light amount approaches 0 digit from the current digital values Imin_1 and Imin_2 of the minimum light amount and the current digital values Imax_1 and Imax_2 of the maximum light amount, and the maximum light amount. The current determination unit 350 calculates the optimum offset value and gain value so that the current digital value (Imax_n) corresponding to 1 approaches n (0 to n, where n is a natural number). Specifically, the current determination unit 350 calculates the calculated current digital values Imin_1 and Imin_2 for the minimum light amount, the current digital value Imax_1 for the maximum light amount, the first search offset value α1, and the second search offset value α2. Based on the search gain value β1, the gain value β2 and the offset value α3 are determined by the following formulas 2 and 3. n is, for example, 1023 digits.

  As described above, the light source device 11 can set the light amount control range indicating the current value range used for the light amount control by determining the offset value α3 and the gain value β2. The set light amount control range is, for example, a current digital value range such as the IL characteristic shown in FIG. The current determination unit 350 of the light source device 11 performs a search process of a digital current value corresponding to the light amount of the laser light output from the light source element 111 in the set light amount control range. The search process for the current digital value will be described later.

  Returning to FIG. 18, the description of the light amount control process in the light source device 11 is continued. In step S <b> 103, the current determination unit 350 outputs the determined gain value β <b> 2 and offset value α <b> 3 and the current digital value determined by the search process described later to the drive control unit 370.

  In step S <b> 103, the drive control unit 370 of the light source device 11 outputs a drive signal based on the determined drive condition to the light source element 111. Specifically, the conversion unit 371 of the drive control unit 370 converts the current digital value determined by the current determination unit 350 into an analog current value for driving the light source element 111. The offset control unit 372 of the drive control unit 370 offsets the current value of the light source element 111 based on the offset value α3 determined by the current determination unit 350. Further, the gain control unit 373 of the drive control unit 370 amplifies the current value of the light source element 111 based on the gain value β2 determined by the current determination unit 350. In this way, the light source device 11 generates a drive signal for driving the light source element 111 by the processing of the conversion unit 371, the offset control unit 372, and the gain control unit 373 based on the parameters determined by the current determination unit 350. Generate.

  The drive control unit 370 outputs a drive signal to the light source element 111 based on the drive conditions (parameters) set by the conversion unit 371, the offset control unit 372, and the gain control unit 373. The light source element 111 outputs laser light based on the drive signal output from the drive control unit 370.

  Here, since the search process as shown in FIG. 19 is unnecessary light emission for the user, it is preferable that the search process is performed using the light amount control region 210 as shown in FIG. Further, from the viewpoint of a high angle of view, luminance, and the like, it is better that the light amount control area 210 is narrower, that is, the number of scanning lines in the horizontal direction with respect to the vertical direction of the light deflector 13 is smaller. Since the time for one scanning in the horizontal direction is several tens of μs, in consideration of the time for detecting the light amount by the photodetector 119, the number of times that the light amount control area 210 can be lit in one reciprocation (one frame) in the vertical direction is limited. It has been. For this reason, the light source device 11 requires time for the search process because it is necessary to acquire the light quantity over a plurality of frames when the number of times of light emission required for the search process increases. Accordingly, in the case of the search process for the offset value α3 and the gain value β2 as shown in FIG. 19, since the minimum number of lighting of the light source element 111 is four, the search process is performed in a small number of trials, that is, in a short time. Can finish.

  As described above, the light source device 11 sets and sets the light amount control range indicating the range of the current value used for controlling the light amount of the laser light output from the light source element 111 based on the output from the light detector 119. In the light quantity control range, the light quantity of the laser light output from the light source element 111 is controlled. For this reason, the light source device 11 sets the light amount control range based on the output from the light detector 119 so as to cover the dynamic range of the output light amount of the light source element 111 according to environmental changes such as temperature changes. The range used for control can be optimized.

  Further, the light source device 11 determines the offset value α3 and the gain value β2 to be appropriate values based on the output from the photodetector 119, thereby optimizing the light amount control range and performing light amount control. The number of trials required can be reduced.

  Furthermore, for example, a display device such as a HUD needs to perform image drawing and virtual image display with appropriate display luminance for various environmental illuminances, so that the current value of the laser beam is increased or decreased and the light source element is turned on. The average light quantity of the laser beam output from the light source device is optimized by changing the duty ratio of the pulse. Therefore, even if the offset value and gain value are set so as to cover the dynamic range of the output light amount of the light source element 111 according to the environmental illuminance, the IL characteristics change due to temperature fluctuations, or the environmental illuminance differs based on the change. When the IL characteristic is changed by changing to the duty ratio of the lighting pulse or the dynamic range to be used is changed, the offset value and the gain value are not appropriate. Therefore, the light source device 11 sets the light amount control range based on the output from the photodetector 119 even when the dynamic range of the laser light output from the light source element 111 changes at any time. It can correspond to.

  In addition, the light source device 11 sets an optimum light amount control range by determining the offset value α3 and the gain value β2 so that the dynamic range output from the light source element 111 can be controlled with high resolution. The amount of light can be controlled so as to reduce the conversion error.

  Furthermore, since the light source device 11 can perform setting switching by the drive control unit 370 by a simple process, when a plurality of light amounts can be adjusted in the same frame, the search process can be completed within one frame. Further, the light source device 11 can improve the estimation accuracy of the offset value α3 and the gain value β2 by measuring the light amount by the light source device 11 at two or more points with respect to the current value characteristic of one light amount.

Search for Current Digital Value of Minimum Light Amount and Maximum Light Amount Next, a search process for a digital value of a minimum light amount will be described with reference to FIGS. The characteristics of the output light quantity and current digital value of the light source element 111 may have poor linearity as shown in FIG. When a regression line as shown in step S206 and step S212 of FIG. 19 is obtained using such linear current value characteristics, the result shown in FIG. 22B is obtained. As shown in FIG. 22B, the regression line obtained from the two points of the current digital values 100 digit and 200 digits is different from the regression line obtained from the two points of the current digital values 700 digits and 800 digits. For this reason, the calculation result of the current digital value of the minimum light amount and the current digital value of the maximum light amount differ depending on the value used for obtaining the regression line.

  Therefore, when calculating the current digital value of the minimum light amount, the light source device 11 uses the regression line obtained on the low light amount side, and when calculating the current digital value of the maximum light amount, the light source device 11 is obtained on the high light amount side. A regression line may be used. When calculating the digital value of the minimum light amount, it is preferable to use a light amount in the vicinity of the minimum light amount, and the light amount used for obtaining the regression line is not more than half of the value n of the maximum current digital value (Imax_n). Is preferred. That is, the current digital value used for obtaining the regression line is preferably a value of 0 or more and n / 2 or less. On the other hand, when calculating the digital value of the maximum light amount, it is preferable to use a light amount near the maximum light amount, and the light amount used for obtaining the regression line is more than half of the value n of the maximum current digital value (Imax_n). It is preferable. That is, the current digital value used for obtaining the regression line is preferably n / 2 or more and n or less.

  To search for the minimum light amount, it is necessary to acquire IL characteristics having different offset values as shown in FIG. First, the drive control unit 370 uses the first search offset value α1 and the search gain value β1 to set the light source element 111 at two points of the current digital values I3 and I4 so that the light amount is equal to or greater than the oscillation threshold value. Make it emit light. The current determination unit 350 obtains a regression line based on the laser light output by the first search offset value α1 and the search gain value β1 detected by the photodetector 119, and obtains the current digital value of the minimum light amount. Imin_3 is calculated. Similarly, the drive control unit 370 uses the second search offset value α2 and the search gain value β1 to provide light source elements at two points of the current digital values I3 and I4 so that the light amount is equal to or greater than the oscillation threshold value. 111 is caused to emit light. The current determination unit 350 obtains a regression line based on the laser light output by the second search offset value α2 and the search gain value β1 detected by the photodetector 119, and obtains the current digital value of the minimum light amount. Imin_4 is calculated. Then, the current determination unit 350 uses the above equation 3 to calculate the difference between the difference between the first search offset value α1 and the second search offset value α2 and the calculated two current digital values of the minimum light amount ( The offset value α3 is calculated from Imin — 3—Imin — 4) so that the current digital value at the minimum light amount approaches 0 digit.

  At this time, the current determination unit 350 makes the difference between the current digital values I3 and I4 smaller than the difference between the current digital values I1 and I2 as shown in FIGS. The calculation accuracy of can be improved.

  Next, the search process for the current digital value of the maximum light amount will be described. In the search for the maximum light amount, the drive control unit 370 uses the first search offset value α1 and the search gain value β1 at two points of the current digital values I5 and I6 so that the light amount is equal to or greater than the oscillation threshold value. The light source element 111 is caused to emit light. Then, the current determination unit 350 generates a regression line as shown in FIG. 24 based on the laser light output by the first search offset value α1 and the search gain value β1 detected by the photodetector 119. The current digital value Imax_n of the maximum light quantity is calculated. Then, the current determination unit 350 calculates the gain value β2 by using the above formula 2 so that the current digital value Imax_n of the maximum light amount approaches 1023 digits.

  At this time, the current determination unit 350 makes the difference between the current digital values I5 and I6 smaller than the difference between the current digital values I1 and I2 as shown in FIGS. The calculation accuracy of can be improved.

  Thus, the light source device 11 uses the search offset value and the search gain value suitable for determining the minimum light amount and the maximum light amount current digital value used for the light amount control, thereby calculating the light amount control range calculation accuracy. Can be improved.

  Further, the current value characteristic of the output light amount of the light source element 111 changes according to the environmental change, and the current value for outputting the same light amount increases as the temperature increases. Therefore, even if the current digital value Imax_n of the maximum light quantity is adjusted to be n, if the temperature when searching for the current digital value is rising, the current digital value is greater than n as the search result of the maximum light quantity. growing. In anticipation of this increase, it is preferable that the current digital value Imax_n of the maximum light amount is set with a margin with respect to the settable maximum digital value N (N = 0 to N, where N is a natural number). The settable maximum digital value N is, for example, the maximum digital value that can be converted into an analog current value by the conversion unit 371 of the drive control unit 370. The current determination unit 350 sets the gain value β2 such that the value n of the current digital value (Imax_n) of the maximum light amount is n = 900 digits with respect to the settable maximum digital value N = 1023 digits. Thus, the light source device 11 can improve the accuracy of the light amount control by setting the light amount control range so that it can cope with environmental fluctuations such as a temperature change.

  Note that if the margin for the maximum digital value N that can be set is increased, the effective current digital value decreases and the quantization error increases, so the value n of the maximum current digital value (Imax_n) can be set. Preferably, it is above the half of the maximum digital value N. That is, n is preferably a value that satisfies the relationship 2 / N <n <N.

Determination of Current Digital Value Next, a process for determining a current digital value used for scanning an image signal will be described with reference to FIGS. 25 and 26. FIG. When the search process for the offset value and the gain value is completed, the light source device 11 searches for a digital current value used for image drawing and virtual image display. For example, when the image signal is composed of 256 gradation values as in a general display, it is preferable that the light source device 11 obtains the amount of light corresponding to each gradation, and the current digital value search process In this case, the greater the number of times the amount of light is acquired, the better. However, the number of times that the amount of light can be acquired in the light amount control region 210 is limited, and the number of times of acquiring the amount of light for the light source element 111 of one color is limited. Therefore, the light source device 11 calculates the current digital value of each gradation from the regression line, similarly to the offset value and the gain value.

  First, in the search process of the current digital value, when the light source device 11 acquires the IL characteristic from the current digital value for p points, the value n (p / n) of the value n of the current digital value of the maximum light quantity is equally divided. Every time, the current digital value is increased to obtain the IL characteristic. In this case, the amount of increase in light quantity (n / p) between adjacent points is taken as the second amount of increase. On the other hand, the first increase amount for determining the gain value and the offset value as shown in FIG. 19 is for more accurately acquiring the fluctuation of the light amount with respect to the current digital value near the minimum light amount and the maximum light amount. It is preferable to obtain a light amount in a narrower region by making it smaller than the second increase amount.

  Further, the regression line for calculating the current digital value is less affected by the linearity of the IL characteristic when it is obtained from a smaller number of acquisition points. However, even if the IL characteristic has linearity, due to the influence of the quantization error, noise, etc. of the drive control unit 370 and the photodetector 119, an abnormal point having no reproducibility as shown in FIG. The current digital value shown may be a point near 400). The light amount for obtaining the regression line is preferably a value close to the digital current value to be calculated. However, when the regression line is obtained between two points as in the search process shown in FIG. Will be greatly affected.

  In FIG. 25, the ideal IL characteristic is indicated by a solid line. In the solid line of FIG. 25, the current digital value for outputting a light amount of 7 mW is 280 digits. When a digital current value is acquired at 200 digit intervals and a light amount of 7 mW is obtained from a regression line between two points of the current digital value 200 digit and 400 digit, the current digital value is calculated as 400 digit because it is affected by an abnormal point. . However, since this abnormal point is not reproducible, a light amount of 10 mW is output from the light source element 111, and the error becomes large.

  In order to reduce the influence of such abnormal points, it is preferable that the light source device 11 obtains a regression line using at least three acquisition points. FIG. 26 shows a regression line obtained using three points in a dotted line when there are abnormal points, and a solid line showing the IL characteristic of the light amount actually output from the light source element 111. In FIG. 26, when the current digital value corresponding to the light amount of 7 mW is obtained from three points of the current digital values 200 digit, 400 digit and 600 digit, the calculated current digital value is 328 digits. On the other hand, the light amount actually output from the light source element 111 at the current digital value 328 digit is 8.2 mW. That is, it can be seen that the regression line obtained using the three acquisition points has a smaller error than the regression line obtained using the two acquisition points.

  As described above, the light source device 11 determines the current digital value used for image drawing and virtual image display using the regression line calculated using the number of acquired light quantities of three or more points, thereby obtaining an abnormality in the acquired light quantity. The influence of the value can be reduced, and a current digital value with little error from the IL characteristic of the laser light actually output from the light source element 111 can be calculated.

Calculation of Oscillation Threshold at Startup Next, the calculation process of the oscillation threshold at the startup of the light source device 11 will be described. When the search process for the gain value and the offset value is performed, the light source device 11 needs to store the current digital value of the oscillation threshold value. However, since the oscillation threshold value (current digital value) is not known when the light source device 11 is powered on, the light source device 11 first performs a search process of the oscillation threshold current digital value.

  The light source device 11 uses the current digital values I7, I8, and I9 as light source elements so that the amount of increase in the light amount in the adjacent current digital values such as I7, I8, and I9 shown in FIG. 111 is caused to emit light. The light source device 11 causes the drive control unit 370 to change the current digital value until it acquires at least two outputs from the photodetector 119. Then, the light source device 11 uses the two points of the current digital values I8 and I9 that are equal to or greater than the oscillation threshold value, and the relationship between the current digital value and the output of the photodetector 119 as shown in FIGS. The current digital value (Imin_0) corresponding to the oscillation threshold light quantity is calculated according to the characteristics.

Next, a light amount control method using the display device 10 including the light source device 11 will be described. As illustrated in FIG. 9, the light source device 11 includes three color light source elements 111. When the number M of times the light source element 111 is turned on is determined in the light quantity control region 210, the display device 10 quickly searches for the current digital value, so that the light deflection device 13 performs one round trip (one frame) in the vertical direction. It is preferable to obtain three-color IL characteristics. Therefore, the number of times p of acquisition of the amount of light with respect to the laser light output from the light source element 111 of one color is equal to or less than M / 3, which is the total number of times M of the light source elements 111 in one frame distributed in three colors. The nearest integer.

  For example, assume that M = 28 and p = 9. In this case, the light source device 11 uses nine current digital values (current digital values every 100 digits when n = 900 digit) for each IL characteristic of the three color light source elements 111 for one frame. Can be obtained within.

  Further, from the viewpoint of stray light, it is preferable that the light emission position in the light amount control region 210 is away from the image forming region 220. Therefore, as shown in FIG. 28, the light quantity control region 210 is preferably divided into a left end 210a and a right end 210b. In this case, since the IL characteristic is acquired once at the left end 210a and the right end 210b, the total number M of lighting of the light source elements 111 within one frame is a multiple of two.

  When the search period of the setting parameter is one round trip (one frame) in the vertical direction of the light deflecting device 13, when the number of IL characteristic acquisition points is increased, the image forming area 220 becomes narrower, so that balance is considered. There is a need. In order to reduce the influence of abnormal points, when the regression line is obtained by grouping every 3 points or every 4 points, the light source device 11 calculates the current digital values for 9 points even if the IL characteristic has poor linearity. If the IL characteristic is obtained by using this, sufficient light quantity control accuracy can be obtained from the viewpoint of color reproducibility.

  Further, the light source device 11 can switch the offset value and the gain value in the image forming area 220 and the light amount control area 210, for example. Thereby, the light source device 11 can prevent the change in the setting value of the drive control unit 370 by the search process of the offset value and the gain value from affecting the image forming region 220. Further, when the light source device 11 can change the offset value and the gain value even in the light quantity control region 210, the light source device 11 searches each of the offset value and the gain value within one round trip (one frame) in the vertical direction of the light deflection device 13. Can be completed.

  Further, as a method of changing the display brightness of the display device 10, there is a method of changing the pulse width for turning on the light source element 111 to make the duty ratio variable. As shown in FIG. 29, when the pulse width is different, the IL characteristic also changes. Therefore, the light source device 11 can perform light amount control with higher accuracy when the offset value and the gain value are set for each pulse width. it can.

  Further, in the image forming region 220 and the light amount control region 210, the gain value and the offset value are changed in the light amount control region 210 separately from the pulses used for image drawing and virtual image display by switching the duty ratio of the pulse for turning on the light source element 111. In addition, the search process for the current digital value can be performed. For example, when the display device 10 is a HUD, the display luminance is switched with high frequency. Therefore, if the display device 10 searches for setting parameters in different pulses in advance using the light amount control area 210, the display device 10 can quickly reflect appropriate settings even when there is a pulse change command. .

● Summary ●
As described above, the light source device according to the embodiment of the present invention includes the light source element 111 (an example of a light source) that outputs laser light and the control circuit 300 that controls the amount of laser light output from the light source element 111. (An example of a control unit). Then, the control circuit 300 sets and sets the light amount control range indicating the range of the current value used for the light amount control based on the output from the light detector 119 that detects the laser light output from the light source element 111. The light quantity of the laser beam output from the light source element 111 is controlled in the light quantity control range. Therefore, the light source device 11 can optimize the light amount control range by setting the light amount control range based on the output of the photodetector 119.

  In the light source device according to the embodiment of the present invention, the control circuit 300 causes the current digital value corresponding to the minimum amount of laser light to approach 0 and the current digital value Imax_n corresponding to the maximum amount of laser light to be n. A light amount control range indicating a current value range used for light amount control is set so as to approach (0 to n, where n is a natural number). In the light source device 11, the maximum amount of laser light is the maximum amount of light for maintaining the white balance required in the image forming region 220 (an example of the image region), and the minimum amount of laser light. Is the minimum amount of light required to generate a color in the image forming area 220. Therefore, the light source device 11 can increase the resolution of the light amount control by setting the light amount control range in accordance with the range of the light amount of the laser light used for image drawing and virtual image display.

  Furthermore, in the light source device according to the embodiment of the present invention, the control circuit 300 (an example of the control unit) determines an output current value of the laser light output from the light source element 111 (an example of the light source) in the light amount control range. The light source element 111 outputs laser light with the determined output current value. Therefore, the light source device 11 determines the output current value of the laser light output from the light source element 111 within the light amount control range optimally set based on the output of the light detector 119. Can be reduced.

  In addition, the light source device according to the embodiment of the present invention has an offset value for setting a light amount control range indicating a current value range used for controlling the light amount of laser light output from the light source element 111 (an example of a light source). A current determining unit 350 (an example of a current determining unit) that determines α3, a gain value β2, and a current digital value for outputting laser light having a predetermined light amount from the light source element 111, and a light source in a set light amount control range A drive control unit 370 (an example of a drive control unit) that controls driving of the element 111. The drive control unit 370 increases the current digital value I1 (an example of the first current digital value) that outputs a light amount that is equal to or greater than the oscillation threshold of the laser light by a first increase amount from the light amount corresponding to the current digital value I1. The laser light is output from the light source element 111 using the current digital value I2 (an example of the second current digital value) that outputs the amount of light. The current determination unit 350 outputs the laser beam using the first search offset value α1 and the search gain value β1, and uses the second search offset value α2 and the search gain value β1. When the laser beam is output, the relationship between the current digital value and the output of the photodetector 119 is calculated, and the offset value α3 and the gain value β2 for setting the light amount control range are determined based on the calculated result. To do. Therefore, the light source device 11 determines the offset value α3 and the gain value β2 that can control the dynamic range output from the light source element 111 with high resolution, and determines the current digital value corresponding to the desired light amount with high accuracy. Thus, it is possible to set the optimum light amount control range and perform light amount control so as to reduce the quantization error.

  Furthermore, in the light source device according to the embodiment of the present invention, the current determination unit 350 (an example of the current determination unit) outputs the laser beam output using the first search offset value α1 and the search gain value β1. Based on the detected output of the photodetector 119, a current digital value Imin_1 (an example of a first minimum current digital value) corresponding to the minimum light amount of the laser light and a current digital value Imax_1 (an example of the first light amount of the laser light) ( An example of the maximum current digital value) is calculated, and the minimum of the laser beam is calculated based on the output of the photodetector 119 that detects the laser beam output using the second search offset value α2 and the search gain value β1. A current digital value Imin_2 (an example of a second minimum current digital value) corresponding to the amount of light is calculated. The current determination unit 350 controls the light amount based on the calculated current digital values Imin_1, Imax_1, and Imin_2, the first search offset value α1, the second search offset value α2, and the search gain value β1. The offset value α3 and the gain value β2 for setting the light amount control range indicating the range of the analog current value used in the above are determined. Therefore, the light source device 11 determines an offset value and a gain value that can control the dynamic range output from the light source element 111 with high resolution, and determines a current digital value corresponding to a desired light amount with high accuracy. Therefore, it is possible to control the light quantity so as to reduce the quantization error by setting an optimum light quantity control range.

  In the light source device according to the embodiment of the present invention, the current digital value I1 (an example of the first current digital value) that outputs a light amount that is equal to or greater than the oscillation threshold value of the light source element 111, and the light amount corresponding to the current digital value I1. The current digital value I2 (an example of the second current digital value) that outputs the amount of light increased by the first increase amount is a value that is greater than or equal to 0 and less than or equal to n / 2. Then, the current determination unit 350 (an example of the current determination unit) is configured such that the difference between the first search offset value α1 and the second search offset value α2 and the current digital value Imin_1 (an example of the first minimum current digital value). ) And the current digital value Imin_2 (an example of the second minimum current digital value), the offset value α3 is determined so that the current digital value approaches zero. Therefore, the light source device 11 can improve the calculation accuracy of the offset value α3 by using a suitable search offset value to determine the current digital value of the minimum light amount used for the light amount control.

  Furthermore, in the light source device according to the embodiment of the present invention, the current digital value I1 (an example of the first current digital value) and the current digital value I2 (an example of the second current digital value) are n / 2 or more and The value is n or less. Then, the current determination unit 350 (an example of the current determination unit) determines the gain value β2 so that the current digital value Imax_1 (an example of the maximum current digital value) approaches n. Therefore, the light source device 11 can improve the calculation accuracy of the gain value β1 by using a suitable search gain value in order to determine the current digital value of the maximum light amount used for the light amount control.

  Further, in the light source device according to the embodiment of the present invention, the drive control unit 370 (an example of the drive control unit) uses the current digital value determined by the current determination unit 350 (an example of the current determination unit) as an analog current value. A conversion unit 371 for converting into an output current value output from the light source element 111, an offset control unit 372 for offsetting the converted analog current value based on the offset value α3 determined by the current determination unit 350, A gain control unit 373 that amplifies the converted analog current value based on the gain value β2 determined by the current determination unit 350; In the light source device 11, the current digital value Imax_n corresponding to the maximum light amount of the laser light is N (N = 0 to N, where N is a natural number) that is the maximum digital value that the conversion unit 371 can convert to an analog current value. Is a value satisfying the relationship of 2 / N <Imax_n <N. Therefore, the light source device 11 can improve the accuracy of the light amount control by setting the light amount control range so that it can cope with environmental fluctuations such as a temperature change.

  Furthermore, a display device according to an embodiment of the present invention includes a light source device 11, a light deflection device 13 (an example of a scanning unit) that performs two-dimensional scanning with laser light output from the light source device 11, and an image obtained by two-dimensional scanning. A screen 15 (an example of an optical element) irradiated with light, and a predetermined image is displayed by reflecting image light irradiated on the screen 15 with a windshield 50 (an example of a reflecting member). In the display device 10, the screen 15 includes an image forming area 220 (an example of an image area) irradiated with image light, and a light amount control area 210 (an example of a non-image area) irradiated with monitor light used for light amount control. And having. Then, the control circuit 300 (an example of the control unit) of the light source device 11 uses the monitor light emitted in the light amount control area 210 to set the light amount control range or control the light amount of the laser light output from the light source element 111. I do. Therefore, the display device 10 performs the light amount control by the light source device 11 using the monitor light irradiated to the light amount control area 210 different from the image forming area 220, and thereby the color of the image formed in the image forming area 220. Generation of unevenness can be suppressed.

  In addition, the display system according to the embodiment of the present invention includes a free-form surface mirror 30 (imaging optics) that forms an image with a display device 10 and image light irradiated on a screen 15 (an example of an optical element). An example of a system). And in the display system 1, the display apparatus 10 is a head-up display which displays a predetermined | prescribed image on the windshield 50 (an example of a reflecting member) of a moving body. Therefore, the display system 1 can display a predetermined image corresponding to the influence of environmental fluctuations, etc. by optimizing the light amount control range used for the light amount control by the light source device 11.

  Furthermore, the light quantity control method according to an embodiment of the present invention includes a light source element 111 (an example of a light source) that outputs laser light, and a control circuit 300 (control unit) that controls the light quantity of the laser light output from the light source element 111. The light quantity control method executed by the light source device 11 including In the light amount control method according to the embodiment of the present invention, the light source device 11 sets a light amount control range indicating a current value range used for light amount control based on the output from the photodetector 119; And a step of controlling the light amount of the laser light output from the light source element 111 in the set light amount control range. Therefore, the light source device 11 can optimize the light amount control range by setting the light amount control range based on the output of the photodetector 119.

  In addition, a light source device according to an embodiment of the present invention includes a light source element 111 that outputs laser light (an example of a light source), and a control circuit 300 that controls the amount of laser light output from the light source element 111 (of a control unit). An example). The control circuit 300 controls the light amount of the laser light output from the light source element 111 in the light amount control range indicating the range of the current value used for controlling the light amount of the laser light output from the light source element 111, and the light amount control range. Is a range of current values equal to or greater than the oscillation threshold of the laser beam. Therefore, the light source device 11 can optimize the light amount control range and reduce the number of trials required for the light amount control by performing light amount control in a current value range that is equal to or greater than the laser light oscillation threshold.

● Supplement ●
In addition, although the light source device, the display device, the display system, and the moving body according to one embodiment of the present invention have been described, the present invention is not limited to the above-described embodiment, and those skilled in the art can conceive. It can be changed within the possible range.

  Further, the display device 10 equipped with the light source device according to the embodiment of the present invention is not limited to the HUD device, and may be, for example, a head mounted display device, a prompter device, or a projector device. For example, when the light source device 11 according to an embodiment of the present invention is applied to a projector device, the projector device can be configured similarly to the display device 10. That is, the display device 10 may project the image light through the free-form curved mirror 30 onto a projection screen, a wall surface, or the like. Note that the display device 10 may project the image light through the screen 15 onto a projection screen, a wall surface, or the like without using the free-form curved mirror 30.

DESCRIPTION OF SYMBOLS 1 Display system 10 Display apparatus 11 Light source apparatus 13 Optical deflection apparatus (an example of a scanning part)
15 screen (example of optical element)
30 Free-form surface mirror (an example of an imaging optical system)
50 Windshield (an example of a reflective member)
111 Light source element (an example of a light source)
119 Photodetector 300 Control circuit (an example of control unit)
350 Current determining unit (an example of current determining means)
370 Drive control unit (an example of drive control means)
371 Conversion unit 372 Offset control unit 373 Gain control unit

JP 2017-173716 A

Claims (24)

A light source that outputs laser light;
A control unit for controlling the amount of laser light output from the light source,
The control unit sets a light amount control range indicating a range of a current value used for the light amount control based on an output from a photodetector that detects the laser light output from the light source, and in the light amount control range, A light source device for controlling the light quantity.   In the control unit, the current digital value corresponding to the minimum light amount of the laser light approaches 0, and the current digital value corresponding to the maximum light amount of the laser light approaches n (0 to n, where n is a natural number). The light source device according to claim 1, wherein the light quantity control range is set as described above. The control unit determines an output current value of the laser beam in the light amount control range;
The light source device according to claim 1, wherein the light source outputs the laser light at the determined output current value. The light source device according to any one of claims 1 to 3,
The control unit further includes:
Current determining means for determining an offset value and a gain value for setting the light amount control range, and a current digital value for outputting a laser light of a predetermined light amount from the light source;
Drive control means for controlling drive of the light source using an output current value corresponding to the determined current digital value in the set light amount control range;
A light source device. The drive control means includes
A first current digital value that outputs a light amount equal to or greater than the oscillation threshold of the laser light, and a second current digital that outputs a light amount increased by a first increase amount from the light amount corresponding to the first current digital value. Using the value, the laser light is output from the light source,
The current determining means includes
In the case where the laser beam is output using the first search offset value and the search gain value, and in the case where the laser beam is output using the second search offset value and the search gain value, 5. The light source device according to claim 4, wherein a relationship between a digital current value and an output of the photodetector is calculated for each, and an offset value and a gain value for setting the light amount control range are determined based on the calculated result. . The current determining means includes
A first minimum current corresponding to a minimum light amount of the laser beam based on an output of the photodetector that detects the laser beam output using the first search offset value and the search gain value. Calculate the digital value, and the maximum current digital value corresponding to the maximum amount of laser light,
A second minimum current corresponding to a minimum light amount of the laser beam based on an output of the photodetector that detects the laser beam output using the second search offset value and the search gain value. Calculate digital values,
The calculated first minimum current digital value, the maximum current digital value, and the second minimum current digital value, the first search offset value, the second search offset value, and the search gain. The light source device according to claim 5, wherein an offset value and a gain value for setting the light amount control range are determined based on a value. The first current digital value and the second current digital value are values of 0 or more and n / 2 or less,
The current determining means includes
The current digital value approaches 0 based on the difference between the first search offset value and the second search offset value and the difference between the first minimum current digital value and the second minimum current digital value. The light source device according to claim 6, wherein the offset value is determined. The first current digital value and the second current digital value are n / 2 or more and n or less,
The current determining means includes
The light source device according to claim 6, wherein the gain value is determined so that the maximum current digital value approaches n. The drive control means includes
The laser beam is output with a current digital value at a different p point, and the laser beam corresponding to the amount of light that is larger than the first increase amount and increased by a second increase amount that is n / p is output. ,
The current determining means includes
9. The current digital value for outputting a predetermined amount of laser light from the light source is determined based on a relationship between at least three current digital values and the output of the photodetector. The light source device according to one item. The light source device according to any one of claims 4 to 9,
The drive control means further includes:
A converter that converts the current digital value determined by the current determining means into the output current value that is an analog current value;
An offset control unit for offsetting the converted analog current value based on the offset value determined by the current determining means;
And a gain control unit configured to amplify the converted analog current value based on the gain value determined by the current determination unit.   n is a value that satisfies the relationship 2 / N <n <N, where N (N = 0 to N, where N is a natural number) is the maximum digital value that can be converted into an analog current value by the conversion unit. The light source device according to claim 10. The light source device according to any one of claims 1 to 11,
A scanning unit for two-dimensionally scanning laser light output from the light source device;
An optical element irradiated with image light by the two-dimensional scanning,
A display device that displays a predetermined image by reflecting the image light applied to the optical element by a reflecting member. The optical element is
An image region irradiated with the image light, and a non-image region irradiated with monitor light used for controlling the light amount,
The controller is
The display device according to claim 12, wherein the setting of the light amount control range or the control of the light amount is performed using monitor light emitted to the non-image region. The controller is
The monitor light emitted to the non-image area is used to output laser light from the light source with a plurality of different light quantities, and the light quantity control range is set based on the output of the photodetector that detects the laser light. The display device according to claim 13, wherein an offset value and a gain value for performing and a current digital value for outputting a predetermined amount of laser light from the light source are determined.   The display device according to claim 13 or 14, wherein the maximum light amount of the laser light is a light amount that provides a maximum luminance for maintaining the white balance required in the image area.   The display device according to claim 13, wherein the minimum light amount of the laser light is a minimum light amount required for generating a color in the image region.   When the number of times that the laser beam can be irradiated to the non-image area in one frame of the two-dimensional scanning is M, the number of times that the laser beam output from the specific light source can be irradiated is The display device according to claim 13, wherein the display device is an integer smaller than M / 3 and closest to M / 3. The drive control means includes
The display device according to claim 13, wherein the offset value and the gain value are switched between the image region and the non-image region. The drive control means includes
The display device according to any one of claims 13 to 18, wherein a duty ratio of a lighting pulse of the light source is switched between the image region and the non-image region. A display device according to any one of claims 13 to 19,
An imaging optical system that forms an image of the image by the image light applied to the optical element;
A display system comprising:   The display system according to claim 20, wherein the display device is a head-up display that displays the image on the reflecting member of a moving body. A display system according to claim 20 or 21,
A windshield as the reflective member;
A moving object comprising: A light amount control method executed by a light source device comprising: a light source that outputs laser light; and a control unit that controls the amount of laser light output from the light source,
Setting a light amount control range indicating a range of a current value used for controlling the light amount, based on an output from a photodetector that detects the laser light output from the light source;
Controlling the light amount in the set light amount control range;
The light quantity control method to execute. A light source that outputs laser light;
A control unit for controlling the amount of laser light output from the light source,
The control unit controls the light amount in a light amount control range indicating a range of a current value used for the light amount control,
The light amount control range is a light source device in which the current value is equal to or greater than an oscillation threshold value of the laser light.