JP7205418B2 - virtual image display - Google Patents

Description

The disclosure of this specification relates to a technique for displaying a virtual image.

2. Description of the Related Art A virtual image display device configured to be mounted on a vehicle and displaying an image formed as a virtual image, such as the device disclosed in Patent Document 1, is known. The apparatus disclosed in Patent Document 1 scans a light beam incident from a light source at a scanning angle of view so that an optical scanning unit draws an image.

Japanese Patent Application Laid-Open No. 2016-33528

However, in Patent Document 1, it is recognized that the scanning angle of view of the light beam is fixed in drawing control. For this reason, there is room for improvement in the control of drawing when used in vehicles that travel in various external environments.

One object of the disclosure of this specification is to provide a virtual image display device suitable for use in a vehicle.

One of the aspects disclosed herein is a virtual image display device configured to be mounted on a vehicle (1) and displaying an image formed as a virtual image (VRI),
a light source (42) for emitting a light beam;
an optical scanning unit (46) that scans a light beam incident from a light source at a scanning angle of view (SA) so as to draw an image;
A drawing control unit (61) that drives the light source and the optical scanning unit and controls image drawing,
The drawing control unit switches between a wide angle of view state in which the scanning angle of view is wide and a narrow angle of view state in which the scanning angle of view is reduced to a narrow angle of view with respect to the wide angle of view ,
The light source has semiconductor light emitting elements (42a, 42b, 42c) whose output decreases as the junction temperature increases,
The drawing control unit switches between the wide angle of view state and the narrow angle of view state according to the junction temperature .
Another disclosed aspect is a virtual image display device configured to be mounted on a vehicle (1) and displaying an image formed as a virtual image (VRI),
a light source (42) emitting a light beam;
an optical scanning unit (46) that scans a light beam incident from a light source at a scanning angle of view (SA) so as to draw an image;
A drawing control unit (61) that drives the light source and the optical scanning unit and controls the scanning angle of view,
The drawing control unit switches between a wide angle of view state in which the scanning angle of view is wide and a narrow angle of view state in which the scanning angle of view is reduced to a narrow angle of view with respect to the wide angle of view,
The light source has a plurality of semiconductor light-emitting elements that emit light beams of different colors and that have different output drop rates with increasing junction temperature,
The drawing control unit switches between a wide angle-of-view state and a narrow angle-of-view state according to the junction temperature of the semiconductor light-emitting element with the highest rate of decrease among the plurality of semiconductor light-emitting elements, and selects the semiconductor light-emitting element with the highest rate of decrease. The scanning field angle in the narrow field angle state is determined according to the junction temperature.

According to these aspects, in drawing control, a wide angle of view state in which the scanning angle of view is widened, and a narrow angle of view state in which the scanning angle of view is reduced to a narrow angle of view with respect to the wide angle of view state. is switched. By switching the scanning angle of view in this way, it is possible to achieve appropriate drawing for vehicles that move in various external environments. Therefore, the virtual image display device can be made suitable for use in vehicles.

It should be noted that the reference numerals in parentheses exemplarily indicate the correspondence with the portions of the embodiment described later, and are not intended to limit the technical scope.

It is a figure which shows the mounting state to the vehicle of HUD of 1st Embodiment. It is a block diagram which shows schematic structure, such as HCU of 1st Embodiment, and HUD. FIG. 3 is a diagram for explaining optical systems in a light source, an optical scanning unit, and a screen according to the first embodiment; It is a front view which expands and shows the optical scanning part of 1st Embodiment. FIG. 4 is a diagram showing an example of a mode of reducing the scanning angle of view according to the first embodiment, with the left side representing a wide angle of view state and the right side representing a narrow angle of view state. FIG. 10 is a diagram showing another example of a mode of reducing the scanning angle of view in the first embodiment, the left side representing a wide angle of view state and the right side representing a narrow angle of view state. FIG. 10 is a diagram showing another example of a mode of reducing the scanning angle of view in the first embodiment, the left side representing a wide angle of view state and the right side representing a narrow angle of view state. 4 is a flow chart according to the first embodiment; Fig. 4 is a flow chart according to a second embodiment; It is a block diagram which shows schematic structure, such as HCU and HUD of 3rd Embodiment. Fig. 9 is a flow chart according to a third embodiment;

A plurality of embodiments will be described below with reference to the drawings. Note that redundant description may be omitted by assigning the same reference numerals to corresponding components in each embodiment. When only a part of the configuration is described in each embodiment, the configurations of other embodiments previously described can be applied to other portions of the configuration. In addition, not only the combinations of the configurations specified in the description of each embodiment, but also the configurations of a plurality of embodiments can be partially combined even if they are not specified unless there is a particular problem with the combination. .

(First embodiment)
As shown in FIG. 1 , the virtual image display device according to the first embodiment of the present disclosure is a head-up display (HUD) 30 configured to be mounted on a vehicle 1 . HUD 30 is installed on instrument panel 2 of vehicle 1 . The HUD 30 is provided with a laser scanner module (LSM hereinafter) 41 . The LSM 41 draws an image formed as a virtual image VRI on the screen 32 provided on the HUD 30 by manipulating light beams. The image drawn on the screen 32 is projected by the HUD 30 toward the windshield 3 of the vehicle 1 with the display light diffused from the screen 32, so that the image drawn on the screen 32 is opposite to the occupant's eye point EP across the windshield 3. It is displayed as a virtual image VRI outside the vehicle on the side. The virtual image VRI may include a superimposed display object that is superimposed on the scenery outside the vehicle, and an AR display object that realizes augmented reality (AR) display that augments reality.

The windshield 3 of the vehicle 1 is a translucent plate-shaped transparent member made of, for example, glass or synthetic resin, and is arranged above the instrument panel 2 of the vehicle 1 . The windshield 3 is slanted away from the instrument panel 2 from the front of the vehicle toward the rear of the vehicle. It should be noted that the image drawn on the screen 32 may be projected onto a combiner installed separately from the vehicle 1 instead of the windshield 3 .

As shown in FIG. 2 , the vehicle 1 is equipped with a peripheral monitoring sensor 11 , an optical sensor 12 and an HCU (Human Machine Interface Control Unit) 20 . The surroundings monitoring sensor 11, the optical sensor 12, and the HCU 20 are connected as nodes to the communication bus of the in-vehicle network. These nodes connected to the communication bus can communicate with each other.

The surroundings monitoring sensor 11 is an autonomous sensor that monitors the surrounding environment of the vehicle 1 . The peripheral monitoring sensor 11 detects moving objects such as pedestrians, cyclists, animals other than humans, and other vehicles from the detection range around the vehicle 1, as well as falling objects on the road, guardrails, curbs, road signs, lane markings, and the like. Road markings and stationary objects such as mulberry on the road frame can be detected. The surroundings monitoring sensor 11 provides the HCU 20 and the like with detection information obtained by detecting objects around the vehicle 1 through the communication bus.

The perimeter monitoring sensor 11 has a front camera and a millimeter wave radar as detection components for object detection. The front camera outputs, as detection information, at least one of imaging data obtained by imaging a range in front of the vehicle 1 and an analysis result of the imaging data. A plurality of millimeter wave radars are arranged, for example, on the front and rear bumpers of the vehicle 1 at intervals. The millimeter wave radar radiates millimeter waves or quasi-millimeter waves toward the front range, the front side range, the rear range, the rear side range, and the like of the vehicle 1 . Millimeter-wave radar generates detection information by receiving reflected waves reflected by moving and stationary objects. In addition, detection configurations such as lidar and sonar may be included in the perimeter monitoring sensor 11 .

The optical sensor 12 is arranged, for example, on the instrument panel 2 so as to face the windshield 3 . The optical sensor 12 detects the brightness around the vehicle 1 (more specifically, around the virtual image VRI). The optical sensor 12 can adopt a configuration using, for example, a photodiode, a CCD sensor, or a photomultiplier tube. The optical sensor 12 provides detection information to the HUD 30 or the like. Note that the optical sensor 12 may be included in the configuration of the HUD 30 by being integrally formed with the HUD 30 .

The HCU 20 is an electronic control unit that controls display by the HUD 30 . The HCU 20 mainly includes a computer including a processing unit, a RAM (random access memory), a storage unit, an input/output interface, and a bus connecting them. The processing unit is hardware for arithmetic processing coupled with RAM. The processing unit is configured to include at least one arithmetic core such as a CPU (Central Processing Unit) and a GPU (Graphic Processing Unit). The processing unit may have a configuration including an IP core having an FPGA (Field-Programmable Gate Array) and other dedicated functions. The processing unit accesses the RAM to execute various processes for realizing the functions of each functional unit, which will be described later. The storage unit is configured to include, for example, a non-volatile storage medium. The storage unit stores various programs executed by the processing unit.

The HCU 20 has a plurality of functional units for presenting information to a driver as a passenger by executing a program stored in a storage unit by a processing unit. Specifically, the HCU 20 has a display layout section 21 and an image data generation section 22 .

The display layout unit 21 selects display content to be displayed on the HUD 30 and determines the layout of the plurality of display content in the image. The display content is selected based on information detected by the perimeter monitoring sensor 11, state information of the vehicle 1 such as vehicle speed provided through the communication bus, traffic information, and the like.

Display content includes follow content and non-follow content. The display position of the follow-up content is an AR display object, and is associated with a specific superimposed object such as a road surface, another vehicle ahead, a pedestrian, or the like. The superimposition target may be visible to the driver or may be hidden in a blind spot and invisible to the driver. The follow-up content is superimposed and displayed on a specific superimposition target, and moves the apparent display position of the virtual image VRI from the viewer so as to follow the superimposition target. Non-following content is a non-AR display object that does not follow a specific superimposition target.

The layout of the display content by the display layout unit 21 is a layout peculiar to virtual image display superimposed on the scenery outside the vehicle. Specifically, in order to avoid unnecessarily obstructing the view of the scenery outside the vehicle by the occupants, the background color, background pattern, etc. are not displayed in the blank areas where the display content is not arranged, and the occupants The display is regulated so that it can be recognized from It is rare that brightness is applied to the entire area that can be drawn as an image, and display content emerges only in a portion of the area that can be drawn as an image.

The image data generation unit 22 implements a function of generating image data, and converts the display content whose layout is determined by the display layout function into image data that can be displayed by the HUD 30 . The image data generated by the HCU 20 is sequentially provided to the HUD 30 in accordance with the drawing frame rate of the LSM 41 . Along with the provision of the image data, the HCU 20 outputs to the LSM 41 a prohibition command prohibiting reduction of the display size when the follow-up content is included in the display content that is the source of the image data. On the other hand, the HCU 20 outputs to the LSM 41 a permission command permitting reduction of the display size when the display content from which the image data is based consists only of non-following content.

For example, the HCU 20 acquires peripheral information of the vehicle 1 including information detected by the peripheral monitoring sensor 11 . The HCU 20 also acquires vehicle information indicating the state of the vehicle 1 and the like from various devices of the vehicle 1 . When the HCU 20 determines that an abnormality exists in the vicinity of the vehicle 1 or in the vehicle itself using the acquired peripheral information, the HCU 20 determines to display on the HUD 30 abnormality notification content for notifying the abnormality, and includes the abnormality notification content. Generate image data.

Examples of abnormalities around the vehicle 1 include, for example, a state in which a traffic accident has occurred, a state in which a traffic accident is highly likely to occur, and the like. Abnormalities of the vehicle 1 include, for example, failure of the brakes, depletion of fuel for running the vehicle 1 or depletion of remaining battery power, and the like.

Anomaly notification content is, for example, display content belonging to non-following content. The anomaly notification content is content that has extremely high urgency and importance in driving the vehicle 1 . For this reason, the HCU 20 requests the HUD 30 to display the abnormality notification content with a required luminance and a required contrast higher than predetermined values, and also requests the HUD 30 to display the content in red, which is easy for the driver to look at.

The HUD 30 includes a screen 32, a light guide section 33, a main control unit 35, an LSM 41, and the like. The screen 32, the light guide section 33, the main control unit 35 and the LSM 41 are housed in a hollow housing 31. As shown in FIG. The housing 31 has an optically open window 31a on its upper surface facing the windshield 3 . The window portion 31a may be opened mechanically, and may be covered with a dustproof sheet capable of transmitting display light, for example.

The screen 32 is a reflective screen formed in the form of a micromirror array, for example, by evaporating a metal film such as aluminum on the surface of a substrate made of synthetic resin or glass. The screen 32 has a plate-like shape in which micromirrors having mirror curved surfaces that reflect light are arranged in a grid pattern in the projection correspondence range PR. When a light beam is incident on the screen 32, the screen 32 expands the spread angle of the light beam while forming an image of the light beam near the curved surface of the mirror, and emits the light beam from the screen 32 as display light. be able to. As a result, the spatial region within the vehicle 1 where the occupant can visually recognize the virtual image VRI, that is, the eyebox is enlarged. As the screen 32, a transmissive screen formed in a microlens array, a diffusion plate, or the like may be employed instead of the reflective screen.

The light guide section 33 is an optical system that guides display light emitted from the screen 32 toward the windshield 3 . As the light guide section 33, various configurations can be employed, such as a configuration consisting of one concave mirror, a configuration combining one plane mirror and one concave mirror, and a configuration combining one convex mirror and one concave mirror. . The light guide section 33 preferably has an enlarging function of enlarging the virtual image VRI visually recognized by the passenger with respect to the image drawn on the screen 32 .

The main control unit 35 is a unit mainly composed of an electronic control device that controls the entire HUD 30 . The main control unit 35 has a function of supplying power to the LSM 41 to control the LSM 41, and a function of controlling the movable mechanism when the light guide section 33 has a movable mechanism. The main control unit 35 mainly includes a computer having a processing section, a RAM, a storage section, an input/output interface, and a bus connecting these. The processing unit is hardware for arithmetic processing coupled with RAM. The processing unit is configured to include at least one arithmetic core such as a CPU. The processing unit may be configured to include an IP core or the like with FPGA and other dedicated functions. The processing unit accesses the RAM to execute various processes for realizing the functions of each functional unit, which will be described later. The storage unit is configured to include, for example, a non-volatile storage medium. The storage unit stores various programs executed by the processing unit.

2 and 3, the LSM 41 includes a light source 42, a laser guide section 44, an optical scanning section 46, a temperature monitor 48, a drive control unit 51, and the like.

The light source 42 includes a plurality of semiconductor lasers 42a, 42b, 42c. The semiconductor lasers 42a to 42c are semiconductor light emitting devices that use semiconductors and oscillate (emits light) pulsed light beams by the energy of the current flowing through the PN junctions of the semiconductors. For example, three semiconductor lasers 42a to 42c are provided.

The three semiconductor lasers 42a to 42c oscillate light beams with mutually different wavelengths α, β, γ. The peak wavelength α of the light beam oscillated by the semiconductor laser 42a is, for example, a green wavelength in the range of 500 to 560 nm, preferably 540 nm. The peak wavelength β of the light beam oscillated by the semiconductor laser 42b is, for example, a blue wavelength in the range of 430 to 470 nm, preferably 450 nm. The peak wavelength γ of the light beam oscillated by the semiconductor laser 42a is, for example, a red wavelength in the range of 600 to 650 nm, preferably 640 nm.

As the temperature of the PN junctions (hereinafter referred to as junction temperature) of the semiconductor lasers 42a to 42c increases, the amount of light emitted per unit applied current decreases. The temperature characteristics (also referred to as temperature dependence) of the output values for unit input values of the semiconductor lasers 42a to 42c, ie, the temperature characteristics of the amount of light emitted for unit applied current, differ from each other. That is, the decrease curve of the output with respect to the junction temperature differs for each of the semiconductor lasers 42a to 42c. In particular, in the present embodiment, the semiconductor laser 42c that oscillates a red wavelength light beam has a larger rate of decrease in output with increasing temperature than the semiconductor laser 42a with a green wavelength and the semiconductor laser 42b with a blue wavelength.

The laser guide section 44 guides the light beams emitted from the semiconductor lasers 42a to 42c to a common optical path so that the light beams are superimposed. The laser guide section 44 is composed of a plurality of condenser lenses 44a, 44b, 44c, a folding mirror 44d, dichroic mirrors 44e, 44f, and the like. The condenser lenses 44a-c are provided in the same number (for example, three) as the semiconductor lasers 42a-c. The number of dichroic mirrors 44e and 44f is one less than that of the semiconductor lasers 42a to 42c (for example, two).

The three condensing lenses 44a-c are arranged at predetermined intervals in the traveling direction of the respective light beams with respect to the corresponding semiconductor lasers 42a-c. Each of the condensing lenses 44a to 44c is made of, for example, synthetic resin or glass, and is translucent. Each condensing lens 44a-c collects the light beams from the corresponding semiconductor lasers 42a-c by refraction, and adjusts the beam waist of each light beam so that it is positioned near or on the screen 32. do.

The folding mirror 44d is arranged at a predetermined distance from the condensing lenses 44a to 44c in the traveling direction of the light beam, and reflects the green wavelength laser beam transmitted through the condensing lens 44a.

The two dichroic mirrors 44e and 44f are arranged with a predetermined spacing in the traveling direction of each light beam with respect to the corresponding condenser lenses 44b and 44c. Each of the dichroic mirrors 44e and 44f reflects light beams of specific wavelengths among the light beams transmitted through the condensing lenses 44a to 44c, and transmits other light beams. Specifically, the dichroic mirror 44e corresponding to the condenser lens 44b reflects the blue wavelength light beam and transmits the green wavelength light beam. A dichroic mirror 44f corresponding to the condenser lens 44c reflects the red wavelength light beam and transmits the green and blue wavelength light beams.

Here, a dichroic mirror 44e is arranged at a predetermined interval in the traveling direction of the green wavelength light beam after being reflected by the folding mirror 44d. A dichroic mirror 44f is arranged at a predetermined interval in the traveling direction of the blue wavelength light beam after being reflected by the dichroic mirror 44e. With these arrangements, the green wavelength light beam reflected by the folding mirror 44d passes through the dichroic mirror 44e and is superimposed on the blue wavelength light beam reflected by the dichroic mirror 44e. Also, the green wavelength and blue wavelength light beams are transmitted through the dichroic mirror 44f and are superimposed on the red wavelength light beam after being reflected by the dichroic mirror 44f.

Further, each of the semiconductor lasers 42a to 42c is electrically connected to the drive control unit 51. As shown in FIG. Each of the semiconductor lasers 42a to 42c emits a pulsed light beam in accordance with an electrical signal from the drive control unit 51. FIG. By additively mixing the three-color light beams emitted from the semiconductor lasers 42a to 42c, various colors can be reproduced in an image. In this way, the laser beams enter the optical scanning section 46 from substantially the same direction while being superimposed on the common optical path.

The optical scanning unit 46 is a MEMS mirror that uses a micro-electro-mechanical system (MEMS) and is configured to be able to temporally scan a light beam. A reflective surface 46a is formed on a surface of the optical scanning unit 46 facing the dichroic mirror 44f with a predetermined gap therebetween by vapor deposition of aluminum or the like. The reflecting surface 46a can swing about two rotation axes Ax and Ay substantially perpendicular to each other along a tangential plane of the reflecting surface 46a.

As shown in FIG. 4, the reflecting surface 46a is supported on both sides by inner support beams 46b. The inner support beam 46b is arranged to extend along the rotation axis Ay. Outside the inner support beam 46b, an inner frame 46c is formed so as to entirely surround the outer periphery of the reflecting surface 46a. The inner frame 46c supports the inner support beams 46b and is supported by the outer support beams 46d. The outer support beam 46d is arranged to extend in a direction substantially perpendicular to the inner support beam 46d, that is, along the rotation axis Ax. An outer frame body 46e is formed outside the outer support beams 46d so as to surround the entire circumference of the inner frame body 46c. The outer frame body 46e supports the outer support beams 46d.

The reflective surface 46a of the optical scanning unit 46 is electrically connected to the drive control unit 51, and can be oscillated by the electric signal to change its orientation. By controlling the direction of the optical scanning unit 46, the direction of projection of the light beam onto the screen 32 is temporally deflected starting from the deflection point TP where the light beam is incident on the reflecting surface 46a. becomes possible. In this way, the light beam is scanned within the range of the scanning angle of view SA, and an image can be drawn on the rectangular projection corresponding range PR provided on the screen 32 .

Here, when the reflecting surface 46a is swung around the rotation axis Ay, the light beam is scanned in the longitudinal direction of the projection corresponding range PR. The longitudinal direction of the projection corresponding range PR corresponds to the horizontal direction of the virtual image VRI (in other words, the horizontal direction of the vehicle 1). The angle formed by both ends in the longitudinal direction of the projection correspondence range PR with respect to the deflection point TP is particularly defined as the horizontal angle of view SAh of the scanning angle of view SA. When the reflecting surface 46a is swung around the rotation axis Ax, the light beam is scanned in the short direction of the projection corresponding range PR. The short direction of the projection correspondence range PR corresponds to the vertical direction of the virtual image VRI (in other words, the vertical direction of the vehicle 1). The angle formed by both ends of the projection corresponding range PR in the short direction with respect to the deflection point TP is particularly defined as the vertical angle of view SAv of the scanning angle of view SA.

A temperature monitor 48 monitors the junction temperature of the semiconductor laser 42c. The temperature monitor 48 has a temperature sensor and conversion circuit corresponding to one representative semiconductor laser 42c or corresponding to each of the semiconductor lasers 42a to 42c. Especially in this embodiment, the junction temperature of the semiconductor laser 42c of the red wavelength among the plurality of semiconductor lasers 42a to 42c is monitored. When the junction temperature of one representative semiconductor laser 42c is monitored, the junction temperatures of the other semiconductor lasers 42a and 42b may be considered to be the same as the junction temperature of the representative semiconductor laser 42c. It may be estimated based on an experimentally obtained relational expression from the junction temperature of the semiconductor laser 42c.

The temperature sensor is, for example, a thermistor type temperature sensor, a thermocouple, or the like, and detects the temperature around each semiconductor laser 42c or the temperature of the case of each semiconductor laser 42c. The conversion circuit calculates and outputs the junction temperature from the temperature detected by the temperature sensor and the power consumption of the semiconductor laser 42c. The temperature monitor 48 outputs the calculated junction temperature to the main control unit 35 and the like.

The drive control unit 51 outputs a voltage waveform to the optical scanning section 46 and controls driving of the optical scanning section 46 . At the same time, the drive control unit 51 controls the driving of the semiconductor lasers 42a to 42c to draw an image on the screen 32 according to the light beam emission timing linked with the scanning. The drive control unit 51 includes a drawing controller 52, a light emission driver 58, a resonant scanning driver 54, a forced scanning driver 56, and the like.

A control system of the HUD 30, which includes the main control unit 35 and the drive control unit 51, drives the light source 42 and the optical scanning unit 46, and constitutes a drawing control unit 61 that controls drawing of an image. The drawing control section 61 is a functional section jointly implemented by the processing of the main control unit 35 and the processing of the drive control unit 51 .

The drawing controller 52 is implemented in hardware by an FPGA, for example. An FPGA is a type of integrated electronic circuit such as a so-called PLD (Programmable Logic Device), and is included in a broad definition of processor. An FPGA realizes complex processing by arranging a large number of logic gates, and can execute the processing at a higher speed or with less delay than processing by executing a computer program.

The drawing controller 52 is electrically connected to the main control unit 35 and drivers 54, 56, 58 via a bus or the like. The drawing controller 52 decomposes and converts the image signal input from the main control unit 35 into a signal for controlling the light emission driver 58, a signal for controlling the resonance scanning driver 54, and a signal for controlling the forced driving scanning driver 56, and outputs the signals. and controls the drivers 54, 56 and 58 in cooperation with each other.

A light emission driver 58 is a circuit that controls the light source 42 . Specifically, the light emission driver 58 controls the light emission timing and the light emission amount of each of the semiconductor lasers 42a to 42c based on the signal from the drawing controller 52. FIG.

The resonance scanning driver 54 is a circuit that controls operations around the rotation axis Ay in scanning by the optical scanning unit 46 . Specifically, based on the signal from the drawing controller 52, the resonance scan driver 54 generates and outputs a voltage waveform to be applied to the piezoelectric element for twisting the inner support beam 46b.

In scanning around the rotation axis Ay, the inner support beam 46b is twisted by controlling the voltage value applied to the piezoelectric element in a relatively small cycle. Due to the twisting of the support beam 46b, the reflection surface 46a swings around the rotation axis Ay. When the support beam 46b is twisted, the elastic reaction force of the support beam 46b acts in the direction opposite to the twisting direction. Using this elastic reaction force, the reflection surface 46a can be resonated at a predetermined natural vibration frequency according to the spring constant of the support beam 46b. Therefore, in the optical scanning unit 46, driving in the direction corresponding to the horizontal angle of view SAh is resonance driving using a resonance phenomenon. The voltage waveform for resonance driving is, for example, a sine wave, and by changing the amplitude of the sine wave, the magnitude of the horizontal angle of view SAh can be changed.

The forced drive scanning driver 56 is a circuit that controls scanning around the rotation axis Ax among the scanning by the optical scanning unit 46 . Specifically, the forced scan driver 56 generates and outputs a voltage waveform to be applied to the piezoelectric element for twisting the outer support beam 46d based on the signal from the drawing controller 52. FIG.

In scanning around the rotation axis Ax, the voltage applied to the piezoelectric element is controlled to twist the outer support beam 46d, and the inner frame body 46c rotates around the rotation axis Ax together with the support beam 46b and the reflecting surface 46a. swing. In order to suppress vibration due to the elastic reaction force of the support beam 46d, the voltage waveform of this oscillation has a period sufficiently larger than the natural oscillation period in resonance driving. Therefore, in the optical scanning unit 46, driving in the direction corresponding to the vertical angle of view SAv is forced driving in which the voltage value applied to the piezoelectric element determines the instantaneous amplitude of oscillation about the rotation axis Ax. The voltage waveform for forced driving is, for example, a sawtooth wave, and by changing the amplitude of the sawtooth wave, the magnitude of the vertical angle of view SAv can be changed.

By combining resonance scanning and forced driving scanning in this way, the light beam is scanned two-dimensionally and periodically, and a predetermined drawing frame rate (for example, 40 to 80 fps).

Here, in the present embodiment, a wide angle of view state in which the scanning angle of view SA is a wide angle of view, and a narrow angle of view state in which the scanning angle of view SA is reduced to a narrow angle of view with respect to the wide angle of view state are Switching is possible by controlling the amplitude of the voltage waveform described above.

In the wide angle of view state, the display size of the virtual image VRI can be made larger than in the narrow angle of view state. On the other hand, in the narrow angle of view state, unless the drawing frame rate is significantly changed from that in the wide angle of view state, the drawing time per unit solid angle (that is, the irradiation time of the light beam) becomes longer. Since the density of the light beam can be increased, the brightness of the virtual image VRI can be increased compared to the wide angle of view state. Also, in the narrow angle of view state, power consumption can be reduced compared to the wide angle of view state.

In the narrow angle of view state, various modes of reducing the scanning angle of view SA can be employed. For example, as shown in FIG. 5, by maintaining the amplitude of the voltage waveform in the resonant scanning and reducing the amplitude of the voltage waveform in the forced drive scanning, the horizontal angle of view SAh is the same scanning angle of view as in the wide angle of view state. SA can be maintained and only the vertical angle of view SAv can be reduced.

Further, as shown in FIG. 6, for example, the amplitude of the voltage waveform in forced drive scanning is maintained and the amplitude of the voltage waveform in resonance scanning is reduced, so that the vertical angle of view SAv is the same angle of view as in the wide angle of view state. can be maintained and only the horizontal angle of view SAh can be reduced.

Further, for example, as shown in FIG. 7, both the horizontal angle of view SAh and the vertical angle of view SAv can be reduced at the same time by reducing both the amplitude of the voltage waveform in resonant scanning and the amplitude of the voltage waveform in forced drive scanning. can.

In this embodiment, the wide angle of view in the wide angle of view state is restricted by the size of the screen 32, the size of the concave mirror of the light guide section 33, and the display range of the virtual image VRI. Among the suitable angles of view, the largest angle of view is adopted.

Now, when the HCU 20 inputs the image data including the abnormality notification content to the main control unit 35, the main control unit 35 acquires information on the junction temperature of the semiconductor laser 42c from the temperature monitor 48, Acquire the information of the ambient illuminance of 1. The main control unit 35 calculates the target brightness of the virtual image VRI in order to achieve the brightness or contrast requested from the HCU 20 (particularly the contrast requested in this embodiment) based on the information about the ambient illuminance. The main control unit 35 calculates the maximum output of the light beam that can be transmitted by the semiconductor laser 42c from the junction temperature information, and scans this light beam to achieve the above-described display luminance. Calculate the critical angle of view.

If the narrow angle of view state reduces both the horizontal angle of view SAh and the vertical angle of view SAv, this maximum angle of view is preferably calculated as a solid angle. The angle of view to be compared with the maximum angle of view used in the following determination is also preferably compared as a solid angle. When the narrow angle of view state reduces one of the horizontal angle of view SAh and the vertical angle of view SAv, the critical angle of view may be calculated according to the plane angle, and may be compared according to the plane angle in the determination.

Next, the main control unit 35 determines whether the calculated display brightness can be realized in the wide angle of view state, in other words, whether it is necessary to reduce the scanning angle of view SA by switching to the narrow angle of view state. judge. Specifically, the main control unit 35 determines whether or not the pre-calculated critical angle of view is greater than or equal to the wide angle of view in the wide angle of view state. If the critical angle of view is greater than or equal to the wide angle of view, the target luminance can be achieved even in the wide angle of view state, so the main control unit 35 determines to set the scanning angle of view SA to the high angle of view state. .

If the critical angle of view is less than the wide angle of view, the target luminance cannot be achieved in the wide angle of view state. The subsequent scanning angle of view SA is determined to be the above-described critical angle of view or an angle of view smaller than the critical angle of view.

The main control unit 35 determines whether the display size of the abnormality notification content as generated by the HCU 20 can be realized by the determined reduced scanning angle of view SA, in other words, whether image data including the abnormality notification content needs to be reduced. It is determined whether or not there is When it is necessary to reduce the image data including the anomaly notification content, the main control unit 35 calculates the reduced size of the anomaly notification content so that the display content fits within a narrow angle of view, and determines the display size of the image. , perform the process of shrinking the

In this way, the main control unit 35 sets the display form, converts the image data into an image signal suitable for the LSM 41 , and then inputs the angle-of-view control signal and the image signal to the drive control unit 51 of the LSM 41 . The drive control unit 51 drives the semiconductor lasers 42a to 42c and the optical scanning section 46 through respective drivers based on the angle-of-view control signal and the image signal. The abnormality notification content displayed by the HUD 30 is rendered solely by the semiconductor laser 42c of the red wavelength among the plurality of semiconductor lasers 42a to 42c.

Next, an image drawing control method for controlling drawing of an image, particularly a method for controlling drawing of abnormality notification content, using the HCU 20, the main control unit 35 and the drive control unit 51 will be described with reference to the flowchart of FIG.

In S<b>101 , the HCU 20 acquires surrounding information of the vehicle 1 . After the processing of S101, the process proceeds to S102.

In S<b>102 , the HCU 20 determines whether or not there is an abnormality around the vehicle 1 . If affirmative determination is made in S102, it will move to S105. If a negative determination is made in S102, the process proceeds to S103.

In S103, the HCU 20 acquires vehicle information. After the processing of S103, the process proceeds to S104.

In S104, the HCU 20 determines whether or not the vehicle 1 has an abnormality. If an affirmative determination is made in S104, the process moves to S105, and if a negative determination is made in S104, the series of processes is terminated.

In S<b>105 , the HCU 20 selects anomaly notification content in selecting display content to be displayed on the HUD 30 . After the processing of S105, the process proceeds to S106.

In S106, the main control unit 35 acquires information on the junction temperature of the semiconductor laser 42c. After the processing of S106, the process proceeds to S107.

In S107, the main control unit 35 acquires surrounding illuminance information. After the processing of S107, the process proceeds to S108.

In S108, the main control unit 35 calculates the critical angle of view for achieving the required brightness or required contrast of the anomaly notification content. After the processing of S108, the process proceeds to S109.

In S109, the main control unit 35 determines whether or not it is necessary to reduce the scanning angle of view SA. If an affirmative determination is made in S109, the process proceeds to S110. If a negative determination is made in S109, the scanning angle of view SA is set to a wide angle of view adopted in the wide angle of view state, and the process proceeds to S114.

In S110, the main control unit 35 determines the scanning angle of view SA for displaying the abnormality notification content. After the processing of S110, the process proceeds to S111.

In S111, the main control unit 35 determines whether or not it is necessary to reduce the display size of the abnormality notification content. If an affirmative determination is made in S111, the process moves to S112. If a negative determination is made in S111, the process of reducing the display size of the abnormality notification content is skipped, and the process proceeds to S114.

In S112, the main control unit 35 calculates the maximum display size of the abnormality notification content that can be displayed at the reduced scanning angle of view SA. After the processing of S112, the process proceeds to S113.

In S113, the main control unit 35 executes processing for reducing the display size of the abnormality notification content to the size calculated in S112. After the processing of S113, the process proceeds to S114.

In S<b>114 , the drive control unit 51 draws an image according to the processing of the main control unit 35 and displays the anomaly notification content as a virtual image VRI. A series of processing ends with S114.

Note that in the first embodiment, the HUD 30 corresponds to a “virtual image display device” including the drawing control unit 61 .

(Effect)
The effects of the first embodiment described above will be described again below.

According to the first embodiment, in drawing control, a wide angle of view state in which the scanning angle of view SA is a wide angle of view, and a narrow angle of view state in which the scanning angle of view SA is reduced to a narrow angle of view with respect to the wide angle of view state. is switched. By switching the scanning angle of view SA in this way, it is possible to achieve suitable drawing for the vehicle 1 that moves in various external environments. Therefore, the HUD 30 can be made suitable for adoption in the vehicle 1 .

Further, according to the first embodiment, when abnormality notification content for notifying the surroundings of the vehicle 1 or abnormality in the vehicle 1 is drawn, the scanning angle of view SA is switched to the narrow angle of view state. By drawing the anomaly notification content in the narrow angle of view state, the display brightness of the anomaly notification content can be made higher than in the wide angle of view state. Therefore, the abnormality notification content, which is display content with extremely high urgency and importance in traveling of the vehicle 1, can be displayed in a manner that is likely to attract the attention of the occupants.

Further, according to the first embodiment, it is determined whether or not the display content drawn in the wide angle of view state can be displayed with the target luminance. Switches to the narrow angle of view state. By switching to the narrow angle-of-view state, it is possible to display the display content with target brightness or brightness close to the target brightness that cannot be achieved in the wide-angle state. Therefore, it is possible to easily achieve the display brightness required for the vehicle 1 .

Further, according to the first embodiment, in the narrow angle of view state, the display size of the display content is reduced so as to fit within the narrow angle of view. By reducing the display size, it is possible to display the entire display content so that it can be visually recognized by the occupants. It can be implemented while controlling the situation.

(Second embodiment)
As shown in FIG. 9, the second embodiment is a modification of the first embodiment. The second embodiment will be described with a focus on points different from the first embodiment.

In the second embodiment, the reduction of the scanning angle of view SA can be implemented not only for the abnormality notification content but also for various display content. The main control unit 35 determines switching between the wide angle of view state and the narrow angle of view state according to the junction temperature monitored by the temperature monitor 48 .

The semiconductor laser 42c that oscillates a light beam with a red wavelength has a larger rate of decrease in output with increasing temperature than the semiconductor laser 42a with a green wavelength and the semiconductor laser 42b with a blue wavelength. Therefore, if the wide angle of view state is maintained at a high temperature, there is a possibility that the output of red will be insufficient with respect to the output of green and blue in the high temperature state of the semiconductor lasers 42a to 42c. is worried about collapsing.

Therefore, the main control unit 35 of the second embodiment grasps the junction temperature of the red-wavelength semiconductor laser 42c, and calculates the maximum output, which is the maximum amount of light that can be output from the red-wavelength semiconductor laser 42c, from the junction temperature. do. Then, if the red brightness for enabling the white balance of the displayed content to be positioned in the wide angle of view state can be achieved with an output equal to or less than the maximum output, the high angle of view state is selected; , switching to the narrow angle of view state is performed. At the same time, the main control unit 35 calculates the amount of light emitted from the semiconductor laser 42a with the green wavelength and the semiconductor laser 42b with the blue wavelength so that the white balance of the displayed content in the narrow angle of view state does not collapse.

Specifically, the main control unit 35 calculates the critical angle of view, which is the maximum angle of view at which the white balance of the displayed content can be maintained, based on the maximum output. Then, based on the critical angle of view, the main control unit 35 determines whether the calculated display luminance can be realized in the wide angle of view state, in other words, switches to the narrow angle of view state, as in the first embodiment. determines whether or not it is necessary to reduce the scanning angle of view SA.

By reducing the scanning angle of view SA, even if the output of the red wavelength semiconductor laser 42c is reduced, the brightness of red in the display content can be maintained or increased. Therefore, it is possible to maintain the desired white balance of the displayed content.

Next, an image drawing control method for controlling image drawing using the main control unit 35 and the drive control unit 51 will be described with reference to the flow chart of FIG. This flowchart starts when the HCU 20 generates image data including display content and the image data is input to the main control unit 35 .

In S201, the main control unit 35 acquires junction temperature information of the red wavelength semiconductor laser 42c. After the processing of S201, the process proceeds to S202.

In S202, the main control unit 35 calculates the maximum output of the red wavelength semiconductor laser 42c from the junction temperature. After the processing of S202, the process proceeds to S203.

In S203, the main control unit 35 calculates a critical angle of view that can maintain the white balance of the displayed content. After the processing of S203, the process proceeds to S204.

S204 to S209 are the same as S109 to S114 of the first embodiment. A series of processing ends with S209.

According to the second embodiment described above, the wide angle of view state and the narrow angle of view state are switched according to the junction temperature of the semiconductor lasers 42a to 42c. By switching according to the temperature, it is possible to suppress a decrease in image brightness due to a decrease in the output of the semiconductor lasers 42a to 42c at high temperatures.

Further, according to the second embodiment, among the semiconductor lasers 42a to 42c as a plurality of semiconductor light emitting elements, the semiconductor laser 42c, which has the highest rate of decrease in output due to temperature rise, is selected according to the junction temperature of the semiconductor laser 42c. The angle of view state is switched. Furthermore, the scanning angle of view SA in the narrow angle of view state is determined according to the junction temperature of the semiconductor laser 42c. By matching the setting of the scanning angle of view SA to the semiconductor laser 42c that is most affected by the decrease in output, it is possible to suppress the deterioration of the display quality of the entire image due to the inability to appropriately display only the color by the semiconductor laser 42c. can be done.

Further, according to the second embodiment, in determining the scanning angle of view SA in the narrow angle of view state, the scanning angle of view SA is determined so as to achieve the target white balance. Since it is possible to realize a white balance of the displayed content that is better than in the wide-angle state, it is possible to maintain high image display quality.

(Third Embodiment)
As shown in FIGS. 10 and 11, the third embodiment is a modification of the first embodiment. The third embodiment will be described with a focus on points different from the first embodiment.

In the third embodiment, the HCU 320 is the subject of control of the scanning angle of view SA in drawing an image. The HCU 320 has an angle-of-view control unit 23 shown in FIG. 10 as a functional unit for executing a program stored in a storage unit by a processing unit.

The angle-of-view control unit 23 switches between the wide-angle state and the narrow-angle state based on whether or not there is a blank area in which display content is not arranged in the outer periphery of the image to be drawn. A blank area is, for example, an area in an image whose brightness is lower than the brightness that can be recognized by the passenger, and which cannot be recognized by the passenger.

The angle-of-view control unit 23 sets the scanning angle-of-view SA to a wide-angle state when there is no blank area in the outer periphery of the image to be drawn. If there is a blank area on the periphery of the image and the blank area can be excluded by reducing the scanning angle of view SA, the angle of view control unit 23 sets the scanning angle of view SA to a narrow angle of view state. .

For example, if there is a blank area in, for example, the upper portion (or the lower portion) of the outer peripheral portion, sweeping of the voltage corresponding to the blank area above the sawtooth wave in the voltage waveform of the forced drive scanning is performed. By restricting, drawing corresponding to the blank area can be stopped. At this time, if the speed of sweeping the voltage in the remaining portion is set to the same speed as in the high angle of view state, one cycle of drawing is shortened, so the frame rate of drawing can be increased. Further, at this time, if the speed of sweeping the voltage in the remaining portion is set to be lower than that in the high angle of view state without changing one cycle of the sawtooth wave, the brightness of the display content can be increased.

Further, for example, if there are blank areas on the right and left sides of the outer periphery, by reducing the amplitude of the sine wave in the voltage waveform of the resonance drive, the blank areas on the right and left sides are filled. Both corresponding drawings can be stopped.

On the other hand, if there is a blank area on the right side of the outer periphery and no blank area on the left side, the view angle at the center of resonance cannot be changed. you can't just stop. Therefore, the angle-of-view control unit 23 sets the scanning angle-of-view SA to a wide-angle state.

Next, an image drawing control method for controlling image drawing using the HCU 320, the main control unit 335, and the drive control unit 51 will be described with reference to the flowchart of FIG.

In S301, the HCU 320 selects display content to be displayed on the HUD 330 and determines the layout of the selected display content. After the processing of S301, the process proceeds to S302.

In S302, the HCU 320 determines whether or not there is a blank area in the outer periphery of the image. More strictly, as described above, it is determined whether or not there is an area that can be excluded from the blank area by reducing the scanning angle of view SA. If an affirmative determination is made in S302, the process proceeds to S303. If a negative determination is made in S302, the scanning angle of view SA is set to the wide angle of view adopted in the wide angle of view state, and the process proceeds to S304.

In S303, the HCU 320 determines the reduced scanning angle of view SA based on the position and size of the blank area. After the processing of S303, the process proceeds to S304.

In S304, the main control unit 335 acquires the image data and the scanning angle of view SA information output by the HCU 320, and converts them into an angle of view control signal and an image signal. The drive control unit 51 that has obtained this draws an image and displays the display content as a virtual image VRI. A series of processing ends with S304.

Note that in the third embodiment, the HCU 320 corresponds to a “drawing control device” including the view angle control unit 23 .

According to the third embodiment described above, based on the layout of the display content to be displayed in the image, there is a wide angle of view state in which the scanning angle of view SA is wide, and a state in which the scanning angle of view SA is narrow with respect to the wide angle of view. The narrow angle of view state in which the angle of view is reduced is switched. It is possible to control the scanning angle of view SA in correspondence with the layout unique to virtual image display superimposed on the scenery outside the vehicle. Therefore, the HCU 320 can be made suitable for adoption in the vehicle 1 .

Further, according to the third embodiment, when an image to be drawn has a blank area in the outer peripheral portion, the scanning angle of view SA of the portion corresponding to the blank area is reduced. By reducing the scanning angle of view SA in this way, the power consumption of the optical scanning unit 46 can be suppressed. By suppressing the power consumption, it is possible to increase the power that can be used by other devices provided in the vehicle 1, and to improve the fuel efficiency of the vehicle 1, for example. Therefore, the HCU 320 can be made suitable for adoption in the vehicle 1 .

(Other embodiments)
Although a plurality of embodiments have been described above, the present disclosure is not to be construed as being limited to those embodiments, and can be applied to various embodiments and combinations within the scope of the present disclosure. can be done.

Specifically, as a modification 1, the light source 42 may include an LED as a semiconductor light-emitting element instead of or together with the semiconductor lasers 42a-c.

As a modification 2 of the first embodiment, the abnormality notification content may be displayed in blue, green, white, etc. instead of red, or may be displayed in a plurality of colors.

As a third modification of the first embodiment, when the abnormality notification content is drawn, switching to the narrow angle of view state is performed regardless of whether or not the target luminance can be achieved in the document angle of view state. may

As a fourth modification of the first embodiment, when rendering display content that is required to be displayed with high required brightness or required contrast, different from the abnormality notification content, the scanning angle of view SA is narrow. It may be switched to the angular state.

As a fifth modified example of the third embodiment, the main control unit 35 of the HUD 30 may be the main control unit for controlling the scanning angle of view SA, as in the first and second embodiments.

As a sixth modification of the first and second embodiments, the HCU 320, which corresponds to the drawing control device, may be the main body for controlling the scanning angle of view SA, as in the third embodiment.

As a modification 7, each function provided by at least one of the main control units 35 and 335, the drive control unit 51 and the HCUs 20 and 320 is replaced by software and hardware for executing it, only software, or only hardware. , or a complex combination thereof. Furthermore, if such functions are provided by electronic circuits as hardware, each function can also be provided by digital circuits, including numerous logic circuits, or analog circuits.

As an eighth modification, the form of a storage medium that stores a program or the like capable of implementing the display control method described above may be changed as appropriate. For example, the storage medium is not limited to the configuration provided on the circuit board, but is provided in the form of a memory card or the like, inserted into the slot, and electrically connected to the control circuits of the HCUs 20, 320 and the main control units 35, 335. may be configured to be connected to . Furthermore, the storage media may be optical discs, hard discs, etc., from which programs are copied to the HCUs 20, 320 and the main control units 35, 335. FIG.

As a ninth modification, the main control units 35 and 335 and the drawing controller 52 may be integrated to constitute one electronic control device. In addition, the main control units 35 and 335 may implement the functions of the HCUs 20 and 320 that control the display of the HUDs 30 and 330 to form one electronic control device.

As a tenth modification, the HCUs 20 and 320 may not be mounted on the vehicle 1 together with the HUDs 30 and 330 . When the HCUs 20 and 320 are not mounted on the vehicle 1 and are fixedly arranged outside the vehicle 1 or mounted on another vehicle, the HUD 30, 320 can be connected to the HUD 30, 320 by communication such as the Internet, road-to-vehicle communication, and vehicle-to-vehicle communication. The display by 330 may be remotely controlled.

The controller and techniques described in this disclosure may be implemented by a special purpose computer comprising a processor programmed to perform one or more functions embodied by a computer program. Alternatively, the apparatus and techniques described in this disclosure may be implemented by dedicated hardware logic circuitry. Alternatively, the apparatus and techniques described in this disclosure may be implemented by one or more special purpose computers configured in combination with a processor executing a computer program and one or more hardware logic circuits. The computer program may also be stored as computer-executable instructions on a computer-readable non-transitional tangible recording medium.

1: vehicle, 20, 220: HCU (drawing control unit), 21: display layout unit, 23: angle of view control unit, 30, 330: HUD (virtual image display unit), 35, 335: main control unit (drawing control unit ), 42: light source, 46: optical scanning unit, 51: drive control unit (drawing control unit), SA: scanning angle of view, VRI: virtual image

Claims (7)

A virtual image display device configured to be mounted on a vehicle (1) and displaying an image formed as a virtual image (VRI),
a light source (42) for emitting a light beam;
an optical scanning unit (46) that scans the light beam incident from the light source at a scanning angle of view (SA) so as to draw the image;
a drawing control unit (61) that drives the light source and the optical scanning unit and controls the scanning angle of view;
The drawing control unit switches between a wide angle of view state in which the scanning angle of view is a wide angle of view and a narrow angle of view state in which the scanning angle of view is reduced to a narrow angle of view with respect to the wide angle of view state ,
The light source has a semiconductor light emitting element (42a, 42b, 42c) whose output decreases as the junction temperature increases,
The rendering control unit is a virtual image display device that switches between the wide angle of view state and the narrow angle of view state according to the junction temperature . A virtual image display device configured to be mounted on a vehicle (1) and displaying an image formed as a virtual image (VRI),
a light source (42) for emitting a light beam;
an optical scanning unit (46) that scans the light beam incident from the light source at a scanning angle of view (SA) so as to draw the image;
a drawing control unit (61) that drives the light source and the optical scanning unit and controls the scanning angle of view;
The drawing control unit switches between a wide angle of view state in which the scanning angle of view is a wide angle of view and a narrow angle of view state in which the scanning angle of view is reduced to a narrow angle of view with respect to the wide angle of view state ,
The light source has a plurality of semiconductor light-emitting elements that emit light beams of different colors and that have different rates of decrease in output with respect to an increase in junction temperature,
The drawing control unit switches between the wide angle-of-view state and the narrow angle-of-view state according to the junction temperature of the semiconductor light-emitting element having the highest rate of decrease among the plurality of semiconductor light-emitting elements, and A virtual image display device, wherein the scanning angle of view in the narrow angle of view state is determined according to the junction temperature of the semiconductor light emitting element having the highest ratio . 3. The virtual image display device according to claim 2, wherein, in determining the scanning angle of view in the narrow angle of view state, the drawing control unit determines the scanning angle of view so as to achieve a target white balance. 4. The drawing control unit according to any one of claims 1 to 3, wherein the drawing control unit switches the scanning angle of view to the narrow angle of view state when drawing display content for notifying the surroundings of the vehicle or an abnormality in the vehicle. virtual image display device. The drawing control unit determines whether the display content drawn in the wide angle of view state can be displayed at the target brightness, and if the display content cannot be displayed at the target brightness, the scanning angle of view is changed. The virtual image display device according to any one of claims 1 to 4, wherein the virtual image display device is switched to the narrow angle of view state. The virtual image display device according to any one of claims 1 to 5 , wherein, in the narrow angle of view state, the drawing control unit reduces the display size of the display content so as to be within the narrow angle of view. 7. The drawing control unit according to any one of claims 1 to 6 , wherein when the image to be drawn has a blank region in an outer peripheral portion, the drawing control unit reduces the scanning angle of view of a portion corresponding to the blank region. Virtual image display device.

Images