JP7363201B2 - Light source device, optical scanning device, display system, moving object, light source device control method, and wavelength estimation method - Google Patents

Description

The present invention relates to a light source device, an optical scanning device, a display system, a moving body, a method for controlling a light source device, and a method for estimating a wavelength.

Patent Document 1 discloses a wavelength estimation device that can accurately estimate the wavelength of light from a light source with a simple configuration.

The present invention provides a light source device, an optical scanning device, a display system, a moving object, and a method for controlling a light source device that accurately adjusts light in response to a light source that includes a plurality of wavelength components, as well as a method for controlling a light source that includes a plurality of wavelength components. The purpose of this invention is to provide a method for estimating a wavelength with high accuracy.

A light source device according to the present invention includes a plurality of light sources that output laser beams of different color components, and a light output detection section that detects light outputs of the plurality of light sources, and detects the detection results of the light output detection section; A light source device that estimates a weighted average wavelength based on a relational expression between a weighted average wavelength, which is a weighted average of a plurality of wavelength components possessed by each of a plurality of light sources, and an optical output, and controls the ratio of the optical outputs of each of the plurality of light sources. At least the first light source included in the plurality of light sources has a nonlinear characteristic in the relationship between the weighted average wavelength and the optical output, and the detection result of the optical output detection unit and the weighted average wavelength The ratio of the respective optical outputs of the plurality of light sources is controlled based on a relational expression in which the relationship with the optical output has nonlinear characteristics.

According to the present invention, there is provided a light source device, an optical scanning device, a display system, a moving body, and a control method for a light source device that accurately adjusts light in response to a light source including a plurality of wavelength components, and a method for controlling the wavelength of a light source that oscillates in a multimode. It is possible to provide a wavelength estimation method that estimates wavelength with high accuracy.

1 is a diagram illustrating an example of a system configuration of a display system according to an embodiment. FIG. 1 is a diagram illustrating an example of the configuration of a mounting device according to an embodiment. FIG. 1 is a diagram illustrating an example of a hardware configuration of a display device according to an embodiment. FIG. 1 is a diagram illustrating an example of a functional configuration of a display device according to an embodiment. FIG. 1 is a diagram showing an example of a specific configuration of a light source device according to an embodiment. 1 is a diagram showing an example of a specific configuration of an optical deflection device according to an embodiment. FIG. 3 is a diagram illustrating an example of a specific configuration of a screen according to an embodiment. FIG. 7 is a diagram for explaining the difference in effect due to the difference in magnitude between the diameter of an incident light beam and the diameter of a lens in a microlens array. FIG. 3 is a diagram for explaining the correspondence between mirrors of the optical deflection device and scanning ranges. FIG. 3 is a diagram showing an example of a scanning line locus during two-dimensional scanning. It is a figure showing an example of the functional block of the light source device concerning an embodiment. FIG. 3 is a diagram showing the spectrum distribution of a high-power semiconductor laser that oscillates in longitudinal multimode. 2 is a graph showing the self-temperature dependence and ambient temperature dependence of the wavelength of light from a semiconductor laser. 3 is a graph showing the self-temperature dependence and ambient temperature dependence of the wavelengths of light from red, green, and blue semiconductor lasers. 7 is a graph showing approximate expressions of self-temperature dependence and ambient temperature dependence of the wavelength of light from a semiconductor laser. 7 is a graph showing a modified example of an approximate formula for self-temperature dependence and ambient temperature dependence of the wavelength of light from a semiconductor laser. 3 is a flowchart for explaining light source control processing. 3 is a flowchart for explaining a light emission amount setting process. FIG. 3 is a diagram for explaining a procedure for setting the amount of light emitted from each semiconductor laser.

Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In addition, in the description of the drawings, the same elements are given the same reference numerals, and overlapping description will be omitted.

●Embodiment●
●System Configuration FIG. 1 is a diagram showing an example of the system configuration of a display system according to an embodiment.

The display system 1 allows the viewer 3 to view a displayed image by projecting projection light from a mounting device 100, which is an example of a projection device, onto a transmissive and reflective 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, for example, in a moving body such as a vehicle, an aircraft, or a ship, or a non-mobile body such as a maneuver simulation system or a home theater system. In this embodiment, a case will be described in which the display system 1 is installed in a car, which is an example of a moving object 1A. Note that the usage form of the display system 1 is not limited to this. Hereinafter, the coordinate axes will be defined with X as the traveling direction of the moving body 1A, Y as the left and right direction, and Z as the up and down direction.

For example, the display system 1 displays navigation information necessary for operating the vehicle (for example, vehicle speed, course information, distance to the destination, current location name, presence or absence of an object in front of the vehicle, etc.) through the windshield 50. The observer 3 (driver) is made to visually recognize the location, signs such as speed limit, information such as traffic jam information, etc.). In this case, the windshield 50 functions as a transmissive/reflective member that transmits a portion of the incident light and reflects at least a portion of the remaining light. The distance from the viewpoint of the observer 3 to the windshield 50 is approximately several tens of cm to 1 m. Note that a combiner made of a small transparent plastic disk or the like may be used as a transmissive and reflective member instead of the windshield 50.

The mounted device 100 is, for example, a head-up display device (HUD device). The mounting device 100 may be placed at any position according to the interior design of the automobile, and may be placed below the dashboard of the automobile, or may be embedded within the dashboard 2, for example. In this embodiment, a case will be described in which the mounting device 100 is mounted inside the dashboard 2.

FIG. 2 is a diagram showing an example of the configuration of the loading device 100 according to the embodiment. The mounting device 100 includes a display device 10 as an example of an optical scanning device, a free-form mirror 30, and a windshield 50.

The display device 10 includes a light source device 11 , a light deflection device (light deflection unit) 13 , and a screen 15 . The light source device 11 is a device that irradiates laser light emitted from a light source to the outside of the device. The light source device 11 may emit laser light that is a combination of laser light of three colors, R, G, and B, for example. Laser light emitted from the light source device 11 is guided to the reflective surface of the light deflection device 13. The light source device 11 has a semiconductor light emitting element such as an LD (Laser Diode) as a light source. Note that 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 deflection device 13 is an example of an image forming unit that receives the irradiation light emitted from the light source device 11 and emits image light that forms an image. This is a device that changes the direction of light. The optical deflection device 13 includes scanning means such as a single micro 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 by using The laser beam emitted from the optical deflector 13 is scanned onto the screen 15. Note that the optical deflection device 13 is not limited to a MEMS mirror, and may be configured using a polygon mirror or the like.

The screen 15 is an example of a screen on which an image is formed by focusing the image light emitted from the light deflection device 13, and is a divergent member that has a function of divergent laser light at a predetermined divergence angle. The screen 15 is configured, for example, in the form of an EPE (Exit Pupil Expander) by a transmissive optical element having a light diffusion effect, such as a microlens array (MLA) or a diffusion plate. Note that the screen 15 may be configured with a reflective optical element having a light diffusion effect, such as a micromirror array. The screen 15 forms an intermediate image 40, which is a two-dimensional image, on the screen 15 by scanning the laser beam emitted from the light deflection device 13 onto the screen 15.

Here, the projection method of the display device 10 is a “panel method” in which the 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 a “panel method” in which the intermediate image 40 is There is a "laser scanning method" in which an intermediate image 40 is formed by scanning the emitted laser light with a scanning means.

The display device 10 according to this embodiment employs the latter "laser scanning method." In the "laser scanning method," each pixel can be assigned to emit light or not emit light, so it is generally possible to form a high-contrast image. Note that the display device 10 may use a "panel method" as a projection method.

A virtual image 45 projected onto the free-form mirror 30 and the windshield 50 by the laser beam (luminous flux) emitted from the screen 15 is enlarged from the intermediate image 40 and displayed. The free-form mirror 30 is designed and arranged so as to offset image tilt, distortion, positional shift, etc. caused by the curved shape of the windshield 50. The free-form mirror 30 may be rotatably installed around a predetermined rotation axis. Thereby, the free-form mirror 30 can adjust the reflection direction of the laser beam (luminous flux) emitted from the screen 15 and change the display position of the virtual image 45.

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

The windshield 50 is a transmissive/reflective member that has a function of transmitting a portion of the laser beam (luminous flux) and reflecting at least a portion of the remaining portion (partial reflection function). The windshield 50 functions as a semi-transparent mirror that allows the observer 3 to view the scenery in front of him and the virtual image 45 . The virtual image 45 is image information for the observer 3 to visually recognize, for example, vehicle information (speed, mileage, etc.), navigation information (route guidance, traffic information, etc.), warning information (collision warning, etc.). Note that the transmissive and reflective member may be a front windshield or the like provided separately from the windshield 50. The windshield 50 is an example of a reflective member.

The virtual image 45 may be displayed so as to overlap with 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 free-form mirror 30 and the curved surface of the windshield 50. Note that the windshield 50 may utilize a semi-transmissive mirror (combiner) as an individual transmissive/reflective member having a partial reflection function.

With this configuration, the laser beam (luminous flux) emitted from the screen 15 is projected toward the free-form mirror 30 and reflected by the windshield 50. The observer 3 can now visually recognize a virtual image 45 that is an enlarged intermediate image 40 formed on the screen 15 by the light reflected by the windshield 50.

●Hardware Configuration FIG. 3 is a diagram showing an example of the hardware configuration of the display device according to the embodiment. Note that components may be added or deleted from the hardware configuration shown in FIG. 3 as necessary.

The display device 10 includes a control device 17 for controlling the operation of the display device 10. The control device 17 is a controller such as a board or an IC chip mounted inside the display device 10. The control device 17 includes an FPGA (Field-Programmable Gate Array) 1001, a CPU (Central Processing Unit) 1002, a ROM (Read Only Memory) 1003, and a RAM (Random Access s Memory) 1004, I/F (Interface) 1005, bus line 1006 , an LD driver 1008, a MEMS controller 1010, and a motor driver 1012.

The FPGA 1001 is an integrated circuit whose settings can be changed by the designer of the display device 10. LD driver 1008, MEMS controller 1010, and motor driver 1012 generate drive signals according to control signals from FPGA 1001. The CPU 1002 is an integrated circuit that performs processing to control the entire display device 10. The ROM 1003 is a storage device that stores a program that controls the CPU 1002. The RAM 1004 is a storage device that functions as a work area for the CPU 1002. I/F 1005 is an interface for communicating with external devices. The I/F 1005 is connected to, for example, a CAN (Controller Area Network) of a car.

The LD 1007 is, for example, a semiconductor light emitting element that constitutes a part of the light source device 11. The LD driver 1008 is a circuit that generates a drive signal to drive the LD 1007. The MEMS 1009 is a device that constitutes a part of the optical deflection device 13 and displaces the scanning mirror. MEMS controller 1010 is a circuit that generates a drive signal to drive MEMS 1009. The motor 1011 is an electric motor that rotates the rotation axis of the free-form mirror 30. Motor driver 1012 is a circuit that generates a drive signal to drive motor 1011.

●Functional Configuration FIG. 4 is a diagram showing an example of the functional configuration of the display device according to the embodiment. The functions realized by the display device 10 include a vehicle information receiving section 171, an external information receiving section 172, an image generating section 173, and an image display section 174.

The vehicle information receiving unit 171 has a function of receiving vehicle information (information such as speed and mileage) 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 shown in FIG. 3, the program stored in the ROM 1003, and the like.

The external information receiving unit 172 has a function of receiving information external to the vehicle (position information from GPS, route information or traffic information from a navigation system, etc.) from an external network. The external information receiving unit 172 is realized by the processing of the I/F 1005 and the CPU 1002 shown in FIG. 3, the program stored in the ROM 1003, and the like.

The image generation section 173 has a function of generating image information for displaying the intermediate image 40 and the virtual image 45 based on the information input by the vehicle information reception section 171 and the external information reception section 172. The image generation unit 173 is realized by the processing of the CPU 1002 shown in FIG. 3, a program stored in the ROM 1003, and the like.

The image display section 174 forms an intermediate image 40 on the screen 15 based on the image information generated by the image generation section 173, and projects the laser beam (luminous flux) forming the intermediate image 40 toward the windshield 50. This is a function to display a virtual image 45. The image display unit 174 is realized by the processing of the CPU 1002, FPGA 1001, LD driver 1008, MEMS controller 1010, and motor driver 1012 shown in FIG. 3, and the program stored in the ROM 1003.

Image display section 174 includes a control section 175, intermediate image forming section 176, and projection section 177. The control unit 175 generates control signals that control the operations of the light source device 11 and the light deflection device 13 in order to form the intermediate image 40. Further, the control unit 175 generates a control signal that controls the operation of the free-form mirror 30 in order to display the virtual image 45 at a predetermined position.

Intermediate image forming section 176 forms intermediate image 40 on screen 15 based on the control signal generated by control section 175. The projection unit 177 projects the laser light forming the intermediate image 40 onto a transmissive reflective member (such as the windshield 50) in order to form a virtual image 45 that is visible to the observer 3.

●Light Source Device FIG. 5 is a diagram showing an example of a specific configuration of the light source device 11 according to the embodiment. The light source device 11 includes light source elements 111(r), 111(g), 111(b) (hereinafter referred to as light source element 111 unless it is necessary to distinguish between them), coupling lenses 112(r), 112( g), 112(b) (hereinafter referred to as coupling lens 112 when there is no need to distinguish), aperture 113(r), 113(g), 113(b) (hereinafter referred to as coupling lens 112 when there is no need to distinguish) ), a mirror 114 , light combining elements 115 and 116 , a light branching element 117 , a photodetector 119 , and a temperature detector 120 .

The three-color (R, G, B) light source elements 111(r), 111(g), and 111(b) are LDs (laser diodes) each including a plurality of wavelength components and each having a single or multiple light emitting points. (an example of a plurality of light sources that each output laser light of different color components). The light source elements 111(r), 111(g), and 111(b) output ( injection). The light source device 11 includes a plurality of light source elements 111 (111(r), 111(g), 111(b)) that output light beams of different wavelengths in order to generate colors necessary for an image. The circuit board for driving the light source element 111 is common by arranging each light source element 111(r), 111(g), and 111(b) on the same surface of the light source device 11 in consideration of miniaturization and low cost. be converted into Note that the light source element 111 shown in FIG. 5 has a configuration corresponding to the LD 1007 shown in FIG. 3.

Each of the output light beams is coupled by a corresponding coupling lens 112(r), 112(g), and 112(b), respectively. Since the laser light (luminous flux) output from the light source element 111 is diffused light, it is focused by the corresponding coupling lens 112 and becomes parallel light. Semiconductor lasers have high directivity but have a spread at the emission end, so they gradually attenuate. The light source device 11 uses a coupling lens 112 to convert the emitted light beam into parallel light in order to reduce the loss of the emitted light beam.

Each coupled light beam is shaped by corresponding apertures 113(r), 113(g), and 113(b), respectively. The aperture 113 has a shape (for example, circular, elliptical, rectangular, square, etc.) according to predetermined conditions such as the divergence angle of the light beam. The light beams shaped by the aperture 113 are combined using a mirror 114 and 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 combining elements 115 and 116 are plate-shaped or prism-shaped dichroic mirrors, and reflect or transmit light beams depending on the wavelength, and combine them 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 that has entered 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 by the light branching element 117 into transmitted light and reflected light. Note that the optical branching element 117 only needs to be placed on the optical path between the optical combining element 116 and the optical deflection device 13.

The transmitted light is irradiated onto the light deflection device 13 and used for image drawing and virtual image display in a scanning area (scanning range) 230 on the screen 15. That is, the transmitted light is used as image light. On the other hand, the reflected light is irradiated onto the photodetector 119 and is used as monitor light for adjusting the color and brightness of the virtual image.

A photodetector 119, which is an example of a light output detection section, detects the amount of monitor light branched by the light branching element 117. In order to downsize the light source device 11, it is preferable that the photodetector 119 detects the laser beams (luminous flux) output from the plurality of light source elements 111 with one element.

In the light source device 11 that uses a plurality of laser light sources with different wavelengths, the color expression of the virtual image to be displayed is based on the white balance that achieves white color, similar to a liquid crystal display, so the white balance (light amount ratio) must be adjusted appropriately. It is necessary to set it to . Since the amount of laser light (luminous flux) output by each light source element 111 changes due to environmental changes such as temperature changes, the amount of light used to achieve white balance also changes.

Therefore, the light source device 11 uses a photodetector 119 to detect variations in the light intensity of the laser beam (luminous flux) output from each light source element 111, and performs light intensity control (APC) of the laser beam (luminous flux) output by the light source element 111. I do. The light source device 11 branches part of the laser light combined by the combining element 116 to the photodetector 119 by the optical branching element 117 . Note that the light source device 11 uses the branching surface of the optical branching element 117 as an incident surface of the laser beam (luminous flux), guides the laser beam reflected by the optical branching element 117 to the photodetector 119, and makes the optical branching element 117 A light branching element 117 is arranged to guide the transmitted laser light to the light deflection device 13.

The light source device 11 also includes a temperature detector 120 that detects the temperature around each light source element 111, and based on the temperature detected by the temperature detector 120, the amount of laser light (luminous flux) output by the light source element 111 is determined. Performs control (APC).

●Light deflection device FIG. 6 is a diagram showing an example of a specific configuration of the light deflection device 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 optical deflection device 13 is an example of an optical deflection unit that scans in a main scanning direction, which is an example of a first scanning direction, and a sub-scanning direction, which is an example of a second scanning direction that intersects the first scanning direction.

The mirror 130 has a reflective surface that reflects the laser light emitted from the light source device 11 toward the screen 15 side. The optical deflection device 13 forms a pair of meandering beam portions 132 with a mirror 130 in between. The meandering beam portion 132 has a plurality of folded portions. The folded portion includes first beam portions 132a and second beam portions 132b arranged alternately. The meandering beam portion 132 is supported by a frame member 134. The piezoelectric member 136 is arranged to connect the adjacent first beam portion 132a and second beam portion 132b. The piezoelectric member 136 applies different voltages to the first beam portion 132a and the second beam portion 132b, thereby causing each of the beam portions 132a and 132b to warp.

As a result, adjacent beam portions 132a and 132b are bent 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 deflection device 13 can perform optical scanning in the vertical direction with a low voltage. The horizontal optical scanning centered on the vertical axis is performed by resonance using a torsion bar or the like connected to the mirror 130.

●Screen FIG. 7 is a diagram showing an example of a specific configuration of the screen according to the embodiment. The screen 15 forms an image of the laser light emitted from the LD 1007 that forms part of the light source device 11 . Further, the screen 15 is a divergent member that emits light at a predetermined divergence angle. The screen 15 shown in FIG. 7 has a plurality of hexagonal microlenses 150 (a convex portion as a form of a curved portion) arranged without gaps, as an example of a screen 15 having a plurality of curved portions that curve to diverge light. It has a microlens array structure. The lens diameter (distance between two opposing sides) of the microlens 150 is approximately 200 μm. By making the microlenses 150 hexagonal in shape, the screen 15 can arrange a plurality of microlenses 150 at high density. Note that details of the microlens array 200 and the microlens 150 according to this embodiment will be described later.

FIG. 8 is a diagram for explaining the difference in effect due to the difference in magnitude between the incident light beam diameter and the lens diameter in the microlens array. In FIG. 8(a), the screen 15 is constituted by an optical plate 151 on which microlenses 150 are arranged in alignment. When the incident light 152 is scanned onto the optical plate 151, the incident light 152 is diverged by the microlens 150 and becomes diverging light 153. The screen 15 can diverge the incident light 152 at a desired divergence angle 154 due to the structure of the microlens 150. A lens diameter 155 of the microlens 150 is designed to be larger than a diameter 156a of the incident light 152. Thereby, the screen 15 suppresses the generation of interference noise without causing interference between lenses.

FIG. 8B shows the optical path of diverging light when the diameter 156b of the incident light 152 is twice as large as the lens diameter 155 of the microlens 150. Incident light 152 enters two microlenses 150a and 150b, producing divergent lights 157 and 158, respectively. At this time, since two diverging lights exist in the region 159, light interference may occur. When this interference light enters the observer's eyes, it is visually perceived as interference noise.

In consideration of the above, in order to reduce interference noise, the lens diameter 155 of the microlens 150 is designed to be larger than the diameter 156 of the incident light. Although FIG. 8 has been described using a convex lens, it is assumed that a concave lens also has the same effect.

●Light scanning by a light deflection device FIG. 9 is a diagram for explaining the correspondence between the mirror of the light deflection device and the scanning range. The light emission intensity, lighting timing, and light waveform of each light source element of the light source device 11 are controlled by the FPGA 1001. Each light source element of the light source device 11 is driven by an LD driver 1008 and emits laser light. As shown in FIG. 9, the laser beams emitted from each light source element and whose optical paths have been combined are two-dimensionally deflected around the α axis and β axis by the mirror 130 of the optical deflection device 13, and are scanned via the mirror 130. The light is irradiated onto the screen 15 as light. That is, the screen 15 is two-dimensionally scanned by main scanning and sub-scanning by the optical deflection device 13.

The scanning range is the entire range that can be scanned by the optical deflection device 13. The scanning light oscillates the scanning range of the screen 15 in the main scanning direction at a fast frequency of about 20,000 to 40,000 Hz (reciprocating scanning), and scans one way in the sub-scanning direction at a slow frequency of about several tens of Hz. That is, the light deflection device 13 performs raster scanning on the screen 15. In this case, the display device 10 can perform drawing or display of a virtual image for each pixel by controlling the light emission of each light source element according to the scanning position (position of scanning light).

The time to draw one screen, that is, the scanning time for one frame (one period of two-dimensional scanning) is several tens of milliseconds because the sub-scanning period is several tens of Hz as described above. For example, when the main scanning period is 20,000 Hz and the sub-scanning period is 50 Hz, the scanning time for one frame is 20 msec.

FIG. 10 is a diagram showing an example of a scanning line locus during two-dimensional scanning. The screen 15 includes an image area 61 (effective scanning area) in which the intermediate image 40 is drawn, and a frame area 62 surrounding the image area 61, as shown in FIG. In the image area 61, an image is formed by turning on the light source device 11 (irradiating modulated light) based on image information (image data).

The scanning range is a range that includes the image area 61 and a part of the frame area 62 (a part near the outer edge of the image area 61) on the screen 15. In FIG. 10, the locus of the scan line in the scan range is indicated by a zigzag line. In FIG. 10, the number of scanning lines is smaller 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 200. The image area 61 does not need to be rectangular or flat, and may be polygonal or curved. Further, the screen 15 may be a reflective optical element having a light diffusion effect, such as a micromirror array, depending on the device layout. In the following description, the present embodiment will be described assuming that the screen 15 is constituted by a microlens array 200.

The screen 15 includes a synchronization detection system 60 including a light receiving element in a peripheral area of the image area 61 (a part of the frame area 62) in the scanning range. In FIG. 10, the synchronization detection system 60 is arranged at the corner of the image area 61 on the −X side and the +Y side. A synchronization detection system 60 detects the operation of the optical deflection device 13 and outputs a synchronization signal to the FPGA 1001 for determining scan start timing and scan end timing.

FIG. 11 is a diagram showing an example of functional blocks of the light source device 11 according to the embodiment. Note that descriptions of functions that overlap with those described in FIG. 4 will be omitted.

The image generation unit 173 generates image information for displaying the intermediate image 40 and the virtual image 45, and generates a control signal for controlling the operation of the optical deflection device 13, including a horizontal synchronization signal and a vertical synchronization signal synchronized therewith.

A non-volatile memory (ROM) 1003 stores the relationship between the weighted average wavelength, which is a weighted average of a plurality of wavelength components, and the optical output for each of the plurality of light source elements 111(r), 111(g), and 111(b). The information shown is memorized. The relationship between the weighted average wavelength and the optical output is explained in ``Temperature dependence of the oscillation wavelength is self-temperature dependent due to self-heating according to the amount of emitted light'' disclosed in Japanese Patent Application Laid-Open No. 2017-183690. It is compatible, and details will be explained later.

The image generation unit 173 uses the light amount information obtained from the photodetector 119, the temperature information obtained from the temperature detector 120, and the plurality of light source elements 111(r) and 111(g) obtained from the nonvolatile memory (ROM) 1003. and 111(b), a control signal is generated to control the operation of the light source device 11 so as to generate light of a desired color, based on information indicating the relationship between the weighted average wavelength and the optical output.

The control unit 175 includes a laser control unit 175L and a MEMS control unit 175M, and the MEMS control unit 175M controls the operation of the optical deflection device 13 based on the control signal generated by the image generation unit 173.

The laser control unit 175L controls the operation of the light source device 11 based on the control signal generated by the image generation unit 173. Specifically, the laser control unit 175L controls the output ratio (power balance) of each of the laser beams of the plurality of light source elements 111 so as to generate light of a desired color.

In this embodiment, temperature information obtained from the temperature detector 120, light amount information obtained from the photodetector 119, and a plurality of light source elements 111(r) and 111(g) obtained from the nonvolatile memory (ROM) 1003 are used. and 111(b), the ratio of the respective outputs of the laser beams of the plurality of light source elements 111 is controlled based on information indicating the relationship between the weighted average wavelength and the optical output.

Here, the temperature information, the light amount information, and the information indicating the relationship between the weighted average wavelength and the optical output are defined as "ambient temperature dependence" and "self-temperature dependence" as disclosed in JP2017-183690A. This information is necessary for estimating the wavelength of the emitted light from each semiconductor laser from both sides of the property, so in this embodiment, even if the wavelength of the laser light fluctuates due to temperature changes, it is possible to generate light of the desired color. can do.

FIG. 12 is a diagram showing the spectral distribution of a high-power semiconductor laser performing longitudinal multimode oscillation. In this embodiment, the spectrum distribution of the light emitted from the light source element 111(g) is shown.

In a semiconductor laser having such a spectral distribution in the oscillation wavelength band, as disclosed in Japanese Patent Application Laid-open No. 2017-183690, the output wavelength of the laser is a weighted average wavelength obtained by weighting the weighted average of multiple wavelength components. I'm considering it.

However, in the laser shown in FIG. 12, there is one peak of a plurality of wavelength components when the power is low, but three peaks occur when the power is high. That is, it can be seen that the weight in the weighted average wavelength changes depending on the magnitude of the power.

FIG. 13 is a graph showing the self-temperature dependence and ambient temperature dependence of the wavelength of light from a semiconductor laser. Specifically, the weighted average wavelength of the light source element 111 (g) at ambient temperatures of 15° C. and 80° C. was measured with respect to the time average light amount, and an approximate line is also shown.

As shown in FIG. 13, the relationship between the weighted average wavelength and the light output (the amount of emitted light) is approximated by nonlinear characteristics at both ambient temperatures of 15° C. and 80° C. That is, the light source element 111(g) is an example of a first light source in which the relationship between the weighted average wavelength obtained by weighting a plurality of wavelength components and the optical output has a nonlinear characteristic.

By storing information indicating this nonlinear characteristic in the nonvolatile memory (ROM) 1003 shown in FIG. Based on the light amount information in (g) and the information indicating the relationship between the nonlinear characteristics between the weighted average wavelength and the optical output for the light source element 111 (g) acquired from the nonvolatile memory (ROM) 1003, the light source element 111 ( g) The weighted average wavelength can be estimated with high accuracy.

The light source device 11 then controls the output ratio of the laser beams of the plurality of light source elements 111 based on the estimated weighted average wavelength of the light source elements 111 (g) to generate light of a desired color. I can do it.

Note that FIG. 13 collectively shows the results under a plurality of pulse lighting conditions. The reason for using a plurality of pulse conditions is that pulse modulation (PWM) is required as a means for dimming the display device 10. Thereby, even if PWM is used for dimming, the wavelength can be estimated to a certain extent.

However, if the pulse widths are different, the wavelength may not be fully expressed by the amount of emitted light alone. This is because the wavelength may have a different response to the time-averaged light amount depending on the heat dissipation characteristics of the LD package and the structures surrounding the LD.

JP 2017-183690A states that wavelength estimation can be performed using the definition of "time-average light intensity" regardless of pulse conditions, but even if the time-average light intensity is the same, the wavelength may differ depending on the pulse conditions. There is. This is thought to be caused by the heat dissipation characteristics of the LD light source or transient saturation of the injection current, and therefore the nonlinearity of wavelength change may not be negligible.

To solve this problem, it is preferable to store the nonlinear characteristics shown in FIG. 13 in a nonvolatile memory (ROM) 1003 shown in FIG. 11 for each pulse condition.

FIG. 14 is a graph showing the self-temperature dependence and ambient temperature dependence of the wavelengths of light from red, green, and blue semiconductor lasers. Specifically, the weighted average wavelength of the light source elements 111(r), 111(g), and 111(b) at ambient temperatures of 15°C, 25°C, 40°C, 60°C, and 80°C was measured against the time-averaged light intensity. The approximation line is also shown.

As shown in FIG. 14(a), the weighted average wavelength and light output (emission light amount) of the light source element 111(r) at ambient temperatures of 15° C., 25° C., 40° C., 60° C., and 80° C. The relationship is approximated by a linear characteristic.

As shown in FIG. 14(b), the weighted average wavelength and light output (emission light amount) of the light source element 111(g) at ambient temperatures of 15° C., 25° C., 40° C., 60° C., and 80° C. The relationship is approximated by nonlinear characteristics.

As shown in FIG. 14(c), the weighted average wavelength and light output (emission light amount) of the light source element 111(b) at ambient temperatures of 15° C., 25° C., 40° C., 60° C., and 80° C. The relationship is approximated by a linear characteristic.

By storing information indicating these linear characteristics and nonlinear characteristics in a nonvolatile memory (ROM) 1003 shown in FIG. The obtained light amount information and the nonlinear characteristics or linear characteristics of the weighted average wavelength and optical output for each of the light source elements 111 (r), 111 (g), and 111 (b) acquired from the nonvolatile memory (ROM) 1003. Based on the information indicating the relationship, the weighted average wavelength of the light source elements 111(r), 111(g), and 111(b) can be estimated with high accuracy.

Then, the light source device 11 controls the output ratio of each of the laser beams of the plurality of light source elements 111 based on the estimated weighted average wavelength of the light source elements 111(r), 111(g), and 111(b). , can produce light of desired color.

Note that in FIG. 14, a case has been described in which the relationship between the weighted average wavelength and the light output (light emission amount) of the light source element 111(g) is approximated by nonlinear characteristics. When the relationship between the weighted average wavelength and optical output (light emission amount) is approximated by nonlinear characteristics, or when the weighted average of two or all of the light source elements 111(r), 111(g), and 111(b) The same applies when the relationship between the wavelength and the optical output (the amount of emitted light) is approximated by nonlinear characteristics.

FIG. 15 is a graph showing an approximate expression of the self-temperature dependence and ambient temperature dependence of the wavelength of light from a semiconductor laser. In this embodiment, the self-temperature dependence and ambient temperature dependence of the wavelength of the light source element 111(g) are shown.

The approximate expression shown in FIG. 15 is expressed by a function shown in (Formula 1).

However, λ: estimated weighted average wavelength [nm]
T: ambient temperature of the light source element 111 (g) [°C]
P: Light intensity [mW]
λ(0): Reference weighted average wavelength (wavelength at light intensity 0) [nm] = a1・T+b1
Δλ: wavelength transition amount [nm] =a2・T+b2
Pt: Light intensity at wavelength transition point [mW] =a3・T+b3
S: Transition slope [1/mW] =a4・T+b4
Note that the slope of the tangent at Pt is Δλ·S/4.

The function expressed by (Formula 1) is a function that has one or more inflection points. An inflection point is a point where the second derivative becomes zero and the sign of the second derivative changes before and after that point.

The function expressed by (Equation 1) is characterized by an asymptote for the amount of light emission P, such that λ=λ0 in the limit of P→−∞, and λ=λ0+Δλ in the limit of P→+∞. Furthermore, as P increases, the transition from λ0 to λ0+Δλ continues.

Here, the light intensity at the wavelength transition point is defined as Pt, and the wavelength at the wavelength transition point is defined as λ0+Δλ/2. Further, the slope at the wavelength transition point is Δλ·S/4, which means the slope at which the transition occurs with respect to the amount of light.

Furthermore, each parameter was assumed to change depending on the temperature. (Equation 1) assumes that each parameter is linear with respect to temperature, but each parameter may be nonlinear with respect to temperature.

By storing information indicating the function expressed by (Formula 1) in nonvolatile memory (ROM) 1003 shown in FIG. The weighted average wavelength of the light source element 111 (g) is determined based on the acquired light amount information and the information indicating the function expressed by (Formula 1) for the light source element 111 (g) acquired from the nonvolatile memory (ROM) 1003. can be estimated with high accuracy.

The light source device 11 then controls the output ratio of the laser beams of the plurality of light source elements 111 based on the estimated weighted average wavelength of the light source elements 111 (g) to generate light of a desired color. I can do it.

FIG. 16 is a graph showing a modified example of the approximate equation of the self-temperature dependence and ambient temperature dependence of the wavelength of light from a semiconductor laser. In this embodiment, the self-temperature dependence and ambient temperature dependence of the wavelength of the light source element 111(g) are shown.

The approximate expression shown in FIG. 16(a) is expressed by the function shown in (Formula 2).

However, M: light intensity proportionality coefficient.

The function expressed by (Formula 2) does not asymptote to λ=λ0+Δλ at the limit of P→+∞ like the function expressed by (Formula 1), but asymptotes to a straight line that depends on the amount of light.

The approximate expression shown in FIG. 16(b) is expressed by the function shown in (Equation 3).

The function expressed by (Equation 3) shows an approximate expression having two inflection points. If the usage range of the optical output of the light source element 111(g) is wide, the wavelength characteristics may exhibit complicated behavior, so it is recommended to approximate it with a function having multiple inflection points as shown in (Equation 3). This enables more accurate wavelength estimation.

If the wavelength characteristics of the light source element 111(g) exhibit more complex behavior, another term may be added to (Formula 1), such as (Formula 2) or (Formula 3). good.

By storing information indicating the function expressed by (Equation 2) or (Equation 2) in the nonvolatile memory (ROM) 1003 shown in FIG. Based on the light amount information obtained from the photodetector 119 and the information indicating the function expressed by (Equation 2) or (Equation 2) about the light source element 111 (g) obtained from the nonvolatile memory (ROM) 1003, The weighted average wavelength of the light source element 111(g) can be estimated with high accuracy.

The light source device 11 then controls the output ratio of the laser beams of the plurality of light source elements 111 based on the estimated weighted average wavelength of the light source elements 111 (g) to generate light of a desired color. I can do it.

Note that in FIGS. 15 and 16, a case has been described in which the relationship between the weighted average wavelength and the light output (light emission amount) of the light source element 111(g) is approximated by nonlinear characteristics. The same holds true when the relationship between the weighted average wavelength and the optical output (light emission amount) in (b) is approximated by nonlinear characteristics.

FIG. 17 is a flowchart for explaining the light source control process (an example of a method of controlling the light source device 11).

First, the laser control unit 175L shown in FIG. 11 turns on the light source elements 111(r), 111(g), and 111(b) based on the control signal generated by the image generating unit 173 shown in FIG. Step S1).

Then, the MEMS control unit 175M shown in FIG. 11 controls the operation of the optical deflection device 13 based on the control signal generated by the image generation unit 173, and counts the number of scans performed by the optical deflection device 13 (step S2).

In step S2, when the number of scans by the light deflection device 13 reaches a predetermined number, the image generation unit 173 performs a light emission amount setting process of the light source elements 111(r), 111(g), and 111(b). Step S3).

The laser control unit 175L turns on the light source elements 111(r), 111(g), and 111(b) based on the amount of emitted light set by the image generating unit 173 (step S4). Thereby, the power balance of the emitted light from the light source elements 111(r), 111(g), and 111(b) becomes appropriate, and light of a desired color is generated.

Then, the process returns to step S2 and repeats steps S2 to S4 until the process is completed (step S5). As a result, an image of a desired color is formed.

FIG. 18 is a flowchart for explaining the emitted light amount setting process. Specifically, the process in step S3 of the flowchart shown in FIG. 17 is performed.

The image forming unit 173 shown in FIG. 11 acquires the time average light amount of each of the light source elements 111 (r), 111 (g), and 111 (b) based on the light amount detected by the photodetector 119 (step S12 ). Step S12 is an example of a step in which the photodetector 119 detects the light output of each of the light source elements 111(r), 111(g), and 111(b).

The image forming unit 173 acquires the ambient temperature detected by the temperature detecting unit 120 (step S13).

The image forming unit 173 uses the time average light amount obtained in step S12, the ambient temperature obtained in step S13, and the plurality of light source elements 111(r), 111(g), and 111 obtained from the nonvolatile memory (ROM) 1003. Weighting of each of the light source elements 111(r), 111(g), and 111(b) based on information indicating the relationship between the weighted average wavelength and the nonlinear characteristic or linear characteristic of the optical output for each of (b) The average wavelength is estimated (step S14). Step S14 is an example of a step of estimating the weighted average wavelength of the optical output of each of the light source elements 111(r), 111(g), and 111(b). Steps S12 to S14 are an example of a wavelength estimation method for estimating the wavelength of each output light of the light source elements 111(r), 111(g), and 111(b) that output laser light.

The image forming unit 173 selects the light source element 111 to generate light of a desired color based on the weighted average wavelength of each of the light source elements 111(r), 111(g), and 111(b) estimated in step S14. (r), 111(g) and 111(b) are set (step S15).

FIG. 19 is a diagram for explaining the procedure for setting the amount of light emitted from each semiconductor laser.

In the chromaticity coordinates shown in FIG. 19, if the estimated weighted average wavelengths of the light source elements 111(r), 111(g), and 111(b) are 650 nm, 515 nm, and 445 nm, respectively, then the light source elements 111(r), 111 A color P is generated by appropriately determining the amount of light emitted from two of the light source elements 111 out of (g) and 111(b), and the amount of light emitted from the remaining one light source element 111 is set to a desired color (target color). Set an appropriate value according to the color P.

In FIG. 19, all the colors in the triangle whose vertices are 650 nm, 515 nm, and 445 nm can be generated. The edge of the horseshoe in FIG. 19 is called a "spectral locus" and is a line where wavelengths and colors correspond.

As described above, the light source device 11 according to an embodiment of the present invention includes a plurality of light source elements 111(r), 111(g), and 111(b) each outputting a laser beam of a different color component, and a plurality of a detector 119 that detects the light output of the light source elements 111(r), 111(g), and 111(b), and the first light source element 111(g) included in the plurality of light source elements is The relationship between the weighted average wavelength, which is a weighted average of the wavelength components of g) and 111(b).

Thereby, it is possible to precisely control the light in accordance with the first light source element 111 (g) in which the relationship between the weighted average wavelength and the optical output has nonlinear characteristics.

Even if the first light source element 111(g) has nonlinear characteristics including an inflection point, the light source device 11 is configured to correspond to the first light source element 111(g) having nonlinear characteristics including an inflection point. , the light can be adjusted with high precision.

The second light source elements 111(r) and 111(b) included in the plurality of light sources have linear characteristics in the relationship between the weighted average wavelength and the optical output, and the light source device 11 has linear characteristics. Thus, the ratio of the light outputs of the plurality of light source elements 111(r), 111(g), and 111(b) is controlled.

Thereby, it is possible to precisely control the light in correspondence with the first light source element 111(g) having nonlinear characteristics and the second light source elements 111(r) and 111(b) having linear characteristics. .

The light source device 11 includes a temperature detection section 120 that detects temperature, and takes into account the detection results of the temperature detection section 120 to determine the light output of each of the plurality of light sources 111(r), 111(g), and 111(b). control the ratio of Thereby, it is possible to accurately control the light based on the detected temperature.

A wavelength estimation method according to an embodiment of the present invention is a wavelength estimation method for estimating the wavelength of output light of a light source element 111 (g) that outputs a laser beam, and the light source element 111 (g) has a plurality of wavelengths. The relationship between the weighted average wavelength, which is a weighted average of the components, and the optical output has a nonlinear characteristic, and the process of detecting the optical output of the light source element 111 (g) with the photodetector 119 and the detection with the photodetector 119 estimating the weighted average wavelength of the output light of the light source element 111(g) based on the obtained optical output and the nonlinear characteristics.

Thereby, the weighted average wavelength can be accurately estimated for the light source element 111(g) in which the relationship between the weighted average wavelength and the optical output has nonlinear characteristics.

●Supplement●
Although a display device, a display system, and a moving body according to an embodiment of the present invention have been described, the present invention is not limited to the above-described embodiment, and can be applied within the range that a person skilled in the art can conceive. It can be changed with .

Further, the display device according to an embodiment of the present invention is not limited to a HUD device, and may be, for example, a head-mounted display device, a teleprompter device, or a projector device. For example, when applying the display device according to an embodiment of the present invention 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 via the free-form 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, etc., without going through the free-form mirror 30.

1 Display system 10 Display device (an example of an optical scanning device)
11 Light source device 13 Light deflection device (an example of a light deflection unit)
15 Screen 30 Free-form mirror (an example of an imaging optical system)
45 Virtual image 50 Windshield (an example of a reflective member)
100 Projection device 111 Light source element 119 Photodetector (an example of a light output detection section)
120 Temperature detection section

Japanese Patent Application Publication No. 2017-183690

Claims (10)

Multiple light sources each outputting laser light with different color components,
a light output detection unit that detects the light output of the plurality of light sources,
The weighted average wavelength is estimated based on the detection result of the optical output detection unit and the relational expression between the weighted average wavelength, which is a weighted average of a plurality of wavelength components of each of the plurality of light sources, and the optical output. A light source device that controls the ratio of light outputs of each light source,
At least a first light source included in the plurality of light sources has a nonlinear characteristic in the relationship between the weighted average wavelength and the optical output,
A light source device that controls a ratio of light outputs of each of the plurality of light sources based on a detection result of the light output detection section and a relational expression in which the relationship between the weighted average wavelength and the light output has nonlinear characteristics. The light source device according to claim 1, wherein the nonlinear characteristic includes an inflection point. The second light source included in the plurality of light sources has a linear characteristic in which the relationship between the weighted average wavelength obtained by weighting the plurality of wavelength components and the optical output,
The light source device according to claim 1 or 2, wherein the ratio of the light outputs of the plurality of light sources is controlled by taking the linear characteristic into account. Equipped with a temperature detection section that detects temperature,
4. The light source device according to claim 1, wherein a ratio of light outputs of each of the plurality of light sources is controlled in consideration of the detection result of the temperature detection section. The light source device according to any one of claims 1 to 4,
a light deflection unit that scans the irradiation light emitted from the light source device in a first scanning direction and a second scanning direction orthogonal to the first scanning direction;
An optical scanning device equipped with The optical scanning device according to claim 5, wherein the light deflector turns on the light source based on image information within an image area included in a scanning range in which the irradiation light is scanned, and forms an image in the image area. comprising a screen on which the irradiation light is scanned by the light deflection unit,
The optical scanning device according to claim 6, wherein an image is formed in the image area on the screen. The optical scanning device according to any one of claims 5 to 7,
an imaging optical system that reflects projection light projected from a screen on which the irradiation light is scanned by the light deflection unit;
a reflecting member that reflects reflected light reflected from the imaging optical system,
The imaging optical system is a display system that reflects the projected light toward the reflective member to form a virtual image. comprising the display system according to claim 8,
The reflecting member is a moving object that is a windshield. Multiple light sources each outputting laser light with different color components,
a light output detection unit that detects the light output of the plurality of light sources ,
The weighted average wavelength is estimated based on the detection result of the optical output detection unit and the relational expression between the weighted average wavelength, which is a weighted average of a plurality of wavelength components of each of the plurality of light sources, and the optical output. A method for controlling a light source device that controls a ratio of light outputs of respective light sources, the method comprising:
At least a first light source included in the plurality of light sources has a nonlinear characteristic in the relationship between the weighted average wavelength and the optical output,
A method for controlling a light source device, comprising controlling a ratio of light outputs of each of the plurality of light sources based on a detection result of the light output detection unit and a relational expression in which the relationship between the weighted average wavelength and the light output has a nonlinear characteristic.