JP7114993B2 - DISPLAY DEVICE, DISPLAY SYSTEM, MOBILE, DISPLAY BRIGHTNESS CONTROL METHOD AND PROGRAM - Google Patents

Description

The present invention relates to a display device, a display system, a mobile object, a display brightness control method, and a program.

BACKGROUND ART Display devices such as HUDs (head-up displays) are used as applications that allow drivers (observers) to visually recognize various types of information (vehicle information, warning information, navigation information, etc.) in moving bodies such as vehicles with a small amount of line-of-sight movement. ing. 2. Description of the Related Art In a display device mounted on a vehicle, there is known a technique of controlling the brightness of the display according to the brightness around the vehicle so that the driver can easily see the display.

On the other hand, if the brightness of the display is made to follow the change in brightness around the vehicle, it is conceivable that the visibility of the display for the driver will be impaired due to the flickering of the display due to the sudden change in the brightness of the surroundings. . Therefore, there is known a technique for improving the visibility of the display for the driver by reducing the flickering of the display caused by the sudden change in luminance around the vehicle.

For example, Patent Document 1 discloses that the absolute value of the difference between the current illuminance value and the illuminance value at the time of the previous determination is reduced in order to reduce display flickering due to a change in display luminance without degrading the responsiveness of display luminance adjustment. If it is less than a predetermined threshold, it is determined that there is no change in illuminance. When it is determined that the illuminance has changed continuously for the first number of times, the display brightness of the light-emitting display is adjusted according to the current illuminance value.

However, in the conventional method, since the purpose is not to reduce the responsiveness of the display luminance, when a rapid change in the background luminance occurs (for example, when sunlight enters), the display luminance is also abrupt. , there is a problem that the luminance changes unfavorably for the observer, and the visibility of the displayed information is lowered.

A display device according to the present invention is a display device that displays display information visually recognized by an observer in front of a moving object, and indicates the luminance of a peripheral region including at least part of a display region serving as a background of the display information. Acquisition means for acquiring luminance information at a specific cycle; detection means for detecting that a change in luminance of the peripheral area is equal to or greater than a predetermined value based on the acquired luminance information; and the acquired luminance information. determining means for determining display luminance information indicating the display luminance based on the determining means, when a luminance change equal to or greater than the predetermined value is detected, and when a luminance change equal to or greater than the predetermined value is not detected and the delay time until the display luminance of the display information corresponds to the luminance of the peripheral area is set as a permissible range that does not give a sense of discomfort to the observer. The display luminance information is determined so as to be within the permissible time or shorter than the permissible delay time, and the display information is displayed using the determined display luminance information.

According to the present invention, it is possible to improve the visibility of display information by suppressing changes in display luminance that are undesirable for the observer in response to sudden changes in luminance of the background.

It is a figure which shows an example of the system configuration|structure of the display system which concerns on embodiment. It is a figure showing an example of concrete composition of a light source device concerning an embodiment. It is a figure which shows an example of a specific structure of the optical deflection apparatus which concerns on embodiment. It is a figure showing an example of concrete composition of a screen concerning an embodiment. FIG. 10 is a diagram for explaining the difference in action due to the difference in magnitude relationship between the diameter of an incident light beam and the diameter of a lens in a microlens array; FIG. 4 is a diagram for explaining a correspondence relationship between a mirror of an optical deflection device and a scanning range; FIG. 5 is a diagram showing an example of scanning line trajectories during two-dimensional scanning; 1 is a diagram for explaining an outline of a display system according to a first embodiment; FIG. 4 is a diagram for explaining an outline of a luminance detection area in the display system according to the first embodiment; FIG. FIG. 4 is a diagram for explaining an example of the relationship between a luminance detection area and a display background area in the display system according to the first embodiment; FIG. 4 is a diagram for schematically explaining an example of display brightness information determination processing in the display device according to the first embodiment; It is a figure showing an example of hardware constitutions of a display concerning a 1st embodiment. It is a figure showing an example of functional composition of a display concerning a 1st embodiment. It is a figure which shows an example of a detailed functional structure of the display brightness control part which concerns on 1st Embodiment. 4 is a diagram showing an example of a brightness information management table according to the first embodiment; FIG. FIG. 4 is a diagram showing an example of allowable delay time information according to the first embodiment; FIG. 4 is a flowchart showing an example of display luminance control processing in the display device according to the first embodiment. FIG. 10 is a diagram for explaining a specific example (Part 1) of the influence of a sudden change in brightness in the field of view of the observer; FIG. 10 is a diagram for explaining a specific example (Part 2) of the influence of sudden changes in brightness in the field of view of the observer; FIG. 4 is a diagram for explaining an allowable delay time in the display system according to the first embodiment; FIG. FIG. 4 is a diagram for explaining an allowable delay time in the display system according to the first embodiment; FIG. FIG. 11 is a diagram for explaining an example of the relationship between a luminance detection area and a display background area according to a modification of the first embodiment; FIG. 9 is a flowchart showing an example of display brightness control processing in the display device according to the second embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and overlapping descriptions are omitted.

●Embodiment●
●System Configuration FIG. 1 is a diagram illustrating an example of a system configuration of a display system according to an embodiment. A display system 1 shown in FIG. 1 is a system that allows an observer 3 to visually recognize display information by projecting light projected from a display device 10 onto a transmissive/reflective member. The display information is image information that is superimposed and displayed as a virtual image 45 in the field of view of the observer 3 .

The display system 1 is provided in, for example, a mobile object such as a vehicle, an aircraft or a ship, or a non-mobile object such as a maneuvering simulation system or a home theater system. This embodiment describes a case where the display system 1 is installed in an automobile, which is an example of a moving body. Note that the usage pattern of the display system 1 is not limited to this.

The display system 1 displays, for example, navigation information (such as vehicle speed, course information, distance to the destination, current location name, presence or absence of an object (object) in front of the vehicle, etc.) necessary for steering the vehicle through the windshield 50. position, signs such as speed limit, information such as traffic jam information, etc.) are visually recognized by an observer 3 (driver). In this case, the windshield 50 functions as a transmissive/reflective member that transmits part of the incident light and reflects at least part of the remaining light. The distance from the viewpoint position of the observer 3 to the windshield 50 is about several tens cm to 1 m.

A display system 1 includes a display device 10 , a free-form surface mirror 30 and a windshield 50 . The display device 10 is, for example, a head-up display device (HUD device) mounted on an automobile, which is an example of a mobile object. The display device 10 is arranged at an arbitrary position in accordance with the interior design of the automobile. The display device 10 may be arranged, for example, under the dashboard of an automobile, or may be embedded in the dashboard.

The display device 10 includes a light source device 11 , an optical deflection device 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 irradiate a laser beam obtained by synthesizing three colors of R, G, and B laser beams, for example. A laser beam emitted from the light source device 11 is guided to the reflecting 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. The light source is not limited to this, and may have a semiconductor light emitting element such as an LED (light emitting diode).

The optical deflection device 13 is a device that changes the traveling direction of laser light using MEMS (Micro Electro Mechanical Systems) or the like. The optical deflection device 13 includes scanning means such as a single minute MEMS mirror that oscillates about two orthogonal axes, or a mirror system composed of two MEMS mirrors that oscillates or rotates about one axis. configured using A laser beam emitted from the optical deflection device 13 is scanned on the screen 15 . Note that the optical deflection device 13 is not limited to the MEMS mirror, and may be configured using a polygon mirror or the like.

The screen 15 is a diverging member that has a function of diverging the laser light at a predetermined divergence angle. The screen 15 is in the form of an EPE (Exit Pupil Expander), for example. Note that the screen 15 may be composed of 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 screen 15 with the laser light emitted from the optical deflection device 13. FIG.

Here, the projection method of the display device 10 is a “panel method” in which an intermediate image 40 is formed by an imaging device such as a liquid crystal panel, a DMD panel (digital mirror device panel), or a vacuum fluorescent display (VFD). There is a "laser scanning method" in which an intermediate image 40 is formed by scanning the laser beam that has been emitted by a scanning means.

The display device 10 according to the embodiment employs the latter “laser scanning method”. Since the "laser scanning method" can assign light emission or non-light emission to each pixel, it is generally possible to form a high-contrast image. Note that the display device 10 may use a “panel system” as a projection system.

A virtual image 45 projected onto the free-form surface mirror 30 and the windshield 50 by the laser light (luminous flux) emitted from the screen 15 is enlarged from the intermediate image 40 and displayed. The free-form surface mirror 30 is designed and arranged so as to cancel the inclination, distortion, positional deviation, etc. of the image due to the curved shape of the windshield 50 . The free-form surface mirror 30 may be installed rotatably around a predetermined rotation axis. Thereby, the free-form surface 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 surface mirror 30 is designed using existing optical design simulation software so as to have a certain condensing power so that the imaging position of the virtual image 45 is at a desired position. The display device 10 sets the condensing power of the free-form surface mirror 30 so that the virtual image 45 is displayed at a position (depth position) that is, for example, 1 m or more and 30 m or less (preferably 10 m or less) from the viewpoint position of the observer 3. be done. In addition, the free-form surface mirror 30 may be a concave mirror or other element having light-collecting power. The free-form surface mirror 30 is an example of an imaging optical system.

The windshield 50 is a transmissive/reflective member having a function (partial reflection function) of transmitting part of the laser beam (luminous flux) and reflecting at least part of the rest. The windshield 50 functions as a semi-transmissive mirror that allows the observer 3 to visually recognize the scenery and the virtual image 45 ahead. The virtual image 45 is image information for allowing the observer 3 to visually recognize vehicle information (speed, travel distance, etc.), navigation information (route guidance, traffic information, etc.), warning information (collision warning, etc.), and the like. Note that the transmissive/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 the scenery in front of the windshield 50 . Also, the windshield 50 is not flat but curved. Therefore, the imaging position of the virtual image 45 is determined by the curved surfaces of the free-form surface mirror 30 and 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 such a configuration, the laser light (luminous flux) emitted from the screen 15 is projected toward the free-form surface mirror 30 and reflected by the windshield 50 . The observer 3 can visually recognize a virtual image 45 obtained by enlarging the intermediate image 40 formed on the screen 15 by the light reflected by the windshield 50 .

●Light Source Device FIG. 2 is a diagram showing an example of a specific configuration of the light source device according to the embodiment. The light source device 11 includes light source elements 111R, 111G, and 111B (hereinafter referred to as light source element 111 when there is no need to distinguish between them), coupling lenses 112R, 112G, and 112B, apertures 113R, 113G, and 113B, and a composite element 114. , 115 , 116 and lens 117 .

The three-color (R, G, B) light source elements 111R, 111G, and 111B are, for example, LDs (Laser Diodes) each having a single or a plurality of light emitting points. The light source elements 111R, 111G, and 111B emit laser light (luminous flux) with different wavelengths λR, λG, and λB (eg, λR=640 nm, λG=530 nm, and λB=445 nm).

The emitted laser beams (light beams) are coupled by coupling lenses 112R, 112G, and 112B, respectively. Each coupled laser (light beam) is shaped by apertures 113R, 113G, and 113B, respectively. Apertures 113R, 113G, and 113B have shapes (for example, circular, elliptical, rectangular, square, etc.) according to predetermined conditions such as the angle of divergence of laser light (luminous flux).

The respective laser beams (luminous fluxes) shaped by the apertures 113R, 113G and 113B are synthesized by three synthesizing elements 114, 115 and 116, respectively. The synthesizing elements 114, 115, and 116 are plate-shaped or prism-shaped dichroic mirrors that reflect or transmit the laser beams (luminous fluxes) according to their wavelengths and synthesize them into one luminous flux. The combined luminous flux passes through lens 117 and is guided to optical deflection device 13 .

●Optical Deflecting Device FIG. 3 is a diagram showing an example of a specific configuration of the optical deflecting 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 a scanning section.

The mirror 130 has a reflecting surface that reflects the laser light emitted from the light source device 11 toward the screen 15 . The optical deflector 13 forms a pair of meandering beams 132 with the mirror 130 interposed therebetween. The meandering beam portion 132 has a plurality of folded portions. The folded portion is composed of first beam portions 132a and second beam portions 132b that are alternately arranged. The meandering beam portion 132 is supported by a frame member 134 . The piezoelectric member 136 is arranged to connect the first beam portion 132a and the second beam portion 132b adjacent to each other. The piezoelectric member 136 applies different voltages to the first beam portion 132a and the second beam portion 132b to cause the beam portions 132a and 132b to warp.

As a result, the adjacent beams 132a and 132b bend in different directions. Mirror 130 rotates vertically about its left-right axis due to the accumulated deflection. With such a configuration, the optical deflection device 13 can perform optical scanning in the vertical direction at a low voltage. Horizontal optical scanning around the vertical axis is performed by resonance using a torsion bar or the like connected to the mirror 130 .

●Screen FIG. 4 is a diagram showing an example of a specific configuration of the screen according to the embodiment. The screen 15 forms an image of laser light emitted from the LD 1007 forming part of the light source device 11 . Also, the screen 15 is a diverging member that diverges at a predetermined divergence angle. Screen 15 is an example of an optical element.

The screen 15 shown in FIG. 4 has a microlens array structure in which a plurality of hexagonal microlenses 150 are arranged without gaps. The width of the microlens 150 (distance between two opposing sides) is about 200 μm. By making the shape of the microlenses 150 hexagonal, the screen 15 can arrange a plurality of microlenses 150 at a high density.

Note that the shape of the microlens 150 is not limited to a hexagon, and may be, for example, a quadrangle, a triangle, or the like. Also, although a structure in which a plurality of microlenses 150 are regularly arranged is illustrated, the arrangement of the microlenses 150 is not limited to this. array. When employing such a decentered arrangement, each microlens 150 has a different shape.

FIG. 5 is a diagram for explaining the difference in action due to the difference in magnitude relationship between the diameter of the incident light beam and the diameter of the lens in the microlens array. In FIG. 5A, the screen 15 is composed of an optical plate 151 on which microlenses 150 are aligned. When the optical plate 151 is scanned with the incident light 152 , the incident light 152 is diverged by the microlens 150 and becomes divergent light 153 . The screen 15 can diverge incident light 152 at a desired divergence angle 154 due to the structure of the microlenses 150 . The period 155 of the microlenses 150 is designed to be larger than the diameter 156 a of the incident light 152 . Thereby, the screen 15 suppresses the occurrence of interference noise without causing interference between the lenses.

FIG. 5B shows the optical path of divergent light when the diameter 156b of the incident light 152 is twice as large as the period 155 of the microlens 150. FIG. Incident light 152 impinges on two microlenses 150a, 150b, producing divergent light 157, 158, respectively. At this time, since there are two diverging lights in the region 159, light interference may occur. When this interference light enters the observer's eyes, it is visually recognized as interference noise.

Considering the above, the period 155 of the microlenses 150 is designed to be larger than the diameter 156 of the incident light in order to reduce speckles. Although FIG. 5 has been described in the form of a convex lens, it is assumed that the same effect can be obtained in the form of a concave lens.

FIG. 6 is a diagram for explaining the correspondence relationship between the mirrors of the optical deflection device and the scanning range. Each light source element of the light source device 11 is controlled by the FPGA 1001 in light emission intensity, lighting timing, and light waveform. Each light source element of the light source device 11 is driven by an LD driver 1008 to emit laser light. As shown in FIG. 6, the laser beams emitted from each light source element and combined in their optical paths are two-dimensionally deflected around the α axis and around the β axis by the mirror 130 of the optical deflection device 13, and are scanned via the mirror 130. The screen 15 is irradiated with the 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 (reciprocates) the scanning range of the screen 15 in the main scanning direction (X-axis direction) at a high frequency of about 20,000 to 40,000 Hz, while scanning in the sub-scanning direction at a low frequency of about several tens of Hz. One-way scanning is performed in the (Y-axis direction). That is, the optical deflection device 13 raster scans the screen 15 . In this case, the display device 10 can draw or display a virtual image for each pixel by controlling the light emission of each light source element according to the scanning position (the position of the scanning light).

The time to draw one screen, that is, the scanning time for one frame (one cycle of two-dimensional scanning) is
Since the sub-scanning cycle is several tens of Hz as described above, it becomes several tens of milliseconds. For example, if the main scanning cycle is 20000 Hz and the sub-scanning cycle is 50 Hz, the scanning time for one frame is 20 msec.

FIG. 7 is a diagram showing an example of scanning line trajectories during two-dimensional scanning. As shown in FIG. 7, the screen 15 has an image area 61 (effective scanning area) in which the intermediate image 40 is drawn (irradiated with light modulated according to image data) and a frame area surrounding the image area 61. 62 included.

The scanning range is a range including the image area 61 on the screen 15 and part of the frame area 62 (the area near the outer edge of the image area 61). In FIG. 7, the loci of scanning lines in the scanning range are indicated by zigzag lines. In FIG. 7, the number of scanning lines is less than the actual number for the sake of convenience.

As described above, the screen 15 is composed of a transmissive optical element such as a microlens array that has a light diffusing effect. The image area 61 need not be rectangular or planar, but may be polygonal or curved. Also, the screen 15 may be a flat plate or curved plate that does not have a light diffusing effect. Furthermore, the image area 61 can be a reflective element having a light diffusing effect, such as a micromirror array, depending on the device layout.

The screen 15 has a synchronous detection system 60 including light receiving elements in a peripheral area (part of the frame area 62) of the image area 61 in the scanning range. In FIG. 7, the synchronous detection system 60 is arranged at the corner of the image area 61 on the -X side and the +Y side. A synchronous detection system 60 detects the operation of the optical deflection device 13 and outputs a synchronous signal to the FPGA 1001 for determining the scanning start timing and the scanning end timing.

●First Embodiment●
●Overview Next, the configuration of the display system 1A according to the first embodiment will be described with reference to FIGS. 8 to 21. FIG. First, the overview of the display system 1A according to the first embodiment will be described with reference to FIGS. 8 to 11. FIG.

FIG. 8 is a diagram for explaining the outline of the display system according to the first embodiment. The display system 1A shown in FIG. 8 can improve the visibility of display information (virtual image 45) by suppressing changes in display brightness that are undesirable for the observer 3 in response to sudden changes in background brightness. System.

The display system 1A includes a brightness sensor 70 in addition to the configuration of the display system 1 shown in FIG. The brightness sensor 70 is a sensing device provided to detect the brightness (illuminance) of the road surface in front of the vehicle that constitutes the display system 1 . As shown in FIG. 8, the luminance sensor 70 is installed, for example, above the windshield 50 of an automobile.

The luminance sensor 70 may be a single photoelectric conversion element or the like, a two-dimensional array sensor, or an imaging element such as an in-vehicle camera. As shown in FIG. 9, the brightness sensor 70 is installed at a position where it can detect the brightness (illuminance) of an area (brightness detection area 300) including the road surface in front of the vehicle.

The installation position of the luminance sensor 70 is not limited to the example shown in FIG. 8, and may be installed on the dashboard of the automobile, for example. Alternatively, the luminance sensor 70 may be replaced by an illuminance sensor provided to realize an automatic light function of the automobile, or a rain sensor provided to operate the wipers of the automobile in response to raindrops. Furthermore, although this embodiment describes an example in which the brightness sensor 70 is provided separately from the display device 10A, the brightness sensor 70 may be built in the display device 10A.

FIG. 10 is a diagram for explaining an example of the relationship between the luminance detection area and the display background area in the display system according to the first embodiment. The image shown in FIG. 10 is a landscape image in front of the vehicle viewed through the windshield 50 by the driver (observer 3) of the vehicle. FIG. 10 shows the relationship between the brightness detection area 300 and the display background area 350 on the scenery image visually recognized by the observer 3. As shown in FIG.

The display background area 350 is an area where the display information (virtual image 45) output from the display device 10A is superimposed on the landscape image (background image) and displayed. That is, the driver of the car (observer 3 ) can visually recognize the virtual image 45 within the display background area 350 . The display background area 350 includes display information displayed by the display device 10A and a road surface in front of the vehicle serving as a background image for the display information. The background image of the display information is not limited to the road surface, and may be scenery around the vehicle such as an outer wall of a building located in front of the vehicle, a sign, or the sky.

The luminance detection area 300 includes a display background area 350 and surrounding scenery such as a road surface, an outer wall of a building, a sign, or the sky. Here, the luminance detection area 300 is an area including at least a spatial section of a space where the viewer 3 visually recognizes display information displayed by the display device 10A.

The display device 10A samples the luminance around the automobile in which the display device 10A is mounted, thereby monitoring the luminance change of the display background region 350, which is the region on which the display information is superimposed. The luminance detection area 300 is an example of a peripheral area. Also, the display background area 350 is an example of a display area.

A luminance detection area 300 shown in FIG. 10 includes a display background area 350 . Further, an area outside the display background area 350 exists within the area of the luminance detection area 300 . Since the area outside the display background area 350 is not an area on which display information is superimposed, it is originally an area that should not be subjected to luminance change sampling.

Here, for example, in an area within the luminance detection area 300 but outside the area of the display background area 350, luminance changes in a relatively short period (hereinafter referred to as period noise) may occur. In this case, when the display brightness of the display information is determined based on the brightness data detected in the brightness detection area 300, the display information (virtual image 45 ) will change. Such a change in the display brightness that does not match the change in the background brightness of the display background area 350 gives the observer 3 a feeling of strangeness, and as a result, becomes a factor in impairing the visibility of the display information.

Therefore, the display system 1</b>A according to the first embodiment intentionally does not cause the display luminance of the display information to follow the periodic noise in the luminance detected in the luminance detection area 300 , so that the luminance that is uncomfortable for the observer 3 is displayed. It is possible to reduce the change and improve the visibility of the display information.

FIG. 11 is a diagram for schematically explaining an example of display brightness information determination processing in the display device according to the first embodiment. FIG. 11 shows changes in the background luminance in front of the vehicle in which the display device 10A is mounted (solid line shown in FIG. 11), luminance data sampled by the luminance sensor 70 (solid circles shown in FIG. 11), and determined by the display device 10A. 11 shows information of display brightness information 500 (Δ in FIG. 11) indicating the display brightness of the displayed information.

As shown in FIG. 11, the background luminance in front of the vehicle initially has a low luminance value (IL), but suddenly changes to a high luminance value (IH) on the way. The display device 10A detects a rapid change in background luminance as shown in FIG. 11, for example, when relatively high luminance light such as headlights of an oncoming vehicle or sunlight enters in front of the vehicle.

Further, the luminance sensor 70 samples the luminance data indicating the luminance within the luminance detection area 300 at a predetermined sampling period. In the example shown in FIG. 11, the luminance sensor 70 samples luminance data (S1 to S10) at a predetermined sampling period (sampling time t).

When the display luminance is changed to follow the luminance data sampled by the luminance sensor 70 without a time lag, the display luminance follows the rapid luminance changes such as S4 to S6 shown in FIG. It will be. Therefore, the observer 3 feels uncomfortable with the display, and the visibility of the displayed information is deteriorated. On the other hand, even if the display brightness follows the change in the background brightness for a long time, the observer 3 will feel a delay in the display, and the visibility of the display information will be deteriorated.

Therefore, the display device 10A allows the display luminance to follow a rapid change in the background luminance while providing an appropriate delay with respect to the change in the background luminance. change.

As shown in FIG. 11, the display device 10A determines display luminance information 500 using sampled luminance data. The display device 10A determines the display luminance information 500 using, for example, the average value of the sampled luminance data. In this case, the display device 10A changes stepwise at least one luminance data used for calculating the average value. For example, the display brightness information 500 determined at the time of sampling of sampling number S4 shown in FIG. 11 is the average value of the brightness data of sampling numbers S1 to S4. On the other hand, the display brightness information 500 determined at the time of sampling of sampling number S5 shown in FIG. 11 is the average value of the brightness data of sampling numbers S2 to S5. The display brightness information 500 determined at the time of sampling of sampling number S9 shown in FIG. 11 is the average value of the brightness data of sampling numbers S6 to S9. The display brightness information 500 determined at the time of sampling with the sampling number S9 has the same value as the brightness value of the background brightness IH.

Thus, the display device 10A determines the display luminance information 500 using the average value of the luminance data sampled by the luminance sensor 70. FIG. Therefore, the display device 10A smoothes the change in display luminance with respect to the change in background luminance, thereby reducing the discomfort given to the observer 3 by the change in display luminance.

In addition, the display device 10A sets the time required for the display luminance to follow the luminance value (IH) of the background luminance that has changed abruptly within the allowable delay time T. FIG. The allowable delay time T is a time set as an allowable range of the delay time until the display luminance follows the background luminance so that the observer 3 does not feel uncomfortable. The display device 10A stores in advance the permissible delay time information 90 indicating the permissible delay time T as a set value. Here, when the luminance data sampling time (sampling cycle) is t and the number of times of delay consideration processing is n, the display device 10A specifies the number of delay consideration processing times n so as to satisfy the condition of Expression 1 below. It is assumed that the sampling time t is set in advance as a constant value.

Here, the number of delay consideration processing times n indicates the number of times delay consideration processing is performed by providing a delay time within the allowable delay time T and causing the display luminance to follow the background luminance. The delay-consideration processing count n may be, for example, the same as the number of times the luminance data is sampled by the luminance sensor 70 (sampling count). In this case, the display device 10A specifies the number of times of sampling corresponding to the sampling time (sampling cycle) t of the luminance data so as to satisfy the condition of Expression 1 above. Note that the delay-consideration processing count n may be a count less than the luminance data sampling count.

As shown in Equation 1 above, the display device 10A specifies the delay-consideration processing count n that is equal to or less than T/t. Specifically, for example, when the allowable delay time T=1400 msec and the sampling time t=250 msec, T/t=5.6. (specification), and the delay consideration processing is performed five times or less (for example, five times). In this case, the display device 10A determines the display brightness information 500 so that the display brightness is a brightness value [cd/m ² ] corresponding to the background brightness in the fifth delay consideration process, for example.

In this way, the display device 10A delays the change in the display luminance for the time within the delay allowable time T with respect to the change in the background luminance while causing the display luminance to follow the rapid change in the background luminance. Therefore, the display device 10A can improve the visibility of display information by suppressing changes in display luminance that are undesirable for the observer 3 in response to sudden changes in background luminance.

●Hardware Configuration FIG. 12 is a diagram showing an example of the hardware configuration of the display device according to the first embodiment. Note that the hardware configuration shown in FIG. 11 may have the same configuration in each embodiment, and components may be added or deleted as necessary.

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

The FPGA 1001 is an integrated circuit whose settings can be changed by the designer of the display device 10A. 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 for controlling the entire display device 10A. A ROM 1003 is a storage device that stores programs for controlling the CPU 1002 . The display device 10A realizes the display brightness control method according to the present invention, for example, by having the CPU 1002 execute the program according to the present invention. A RAM 1004 is a storage device that functions as a work area for the CPU 1002 .

An I/F 1005 is an interface for communicating with an external device. The I/F 1005 is connected to, for example, a CAN (Controller Area Network) of an automobile. Also, the I/F 1005 is connected to the brightness sensor 70 . The luminance sensor 70 transmits sensing data (luminance data) to the control device 17 via the I/F 1005 .

The LD 1007 is, for example, a semiconductor light emitting element forming part of the light source device 11 . The LD driver 1008 is a circuit that generates drive signals for driving the LD 1007 . The MEMS 1009 is a device that forms part of the optical deflector 13 and displaces the scanning mirror. The MEMS controller 1010 is a circuit that generates drive signals for driving the MEMS 1009 . A motor 1011 is an electric motor that rotates the rotating shaft of the free-form surface mirror 30 . A motor driver 1012 is a circuit that generates a drive signal for driving the motor 1011 .

●Functional Configuration FIG. 13 is a diagram showing an example of the functional configuration of the display device according to the first embodiment. Functions realized by the display device 10A include a vehicle information receiving portion 171, an external information receiving portion 172, a display brightness control portion 178, an image generating portion 173 and an image display portion 174. FIG.

The vehicle information receiving unit 171 has a function of receiving vehicle information (information such as speed and travel distance) from a 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. 12, the programs stored in the ROM 1003, and the like.

The external information receiving unit 172 is a function of receiving information (position information from GPS, route information or traffic information from a navigation system, etc.) outside the vehicle from an external network. The external information receiving unit 172 is implemented by the processing of the I/F 1005 and the CPU 1002 shown in FIG. 12, the programs stored in the ROM 1003, and the like.

The display brightness control section 178 has a function of controlling the display brightness of the display information output from the display device 10A. The display brightness control unit 178 is realized by the processing of the I/F 1005 and the CPU 1002 shown in FIG. 12, the programs stored in the ROM 1003, and the like. A detailed configuration of the display brightness control unit 178 will be described later.

Image generating portion 173 generates display information (image information) for displaying intermediate image 40 and virtual image 45 based on the information input by vehicle information receiving portion 171, external information receiving portion 172, and display brightness control portion 178. It is a function to generate. The image generator 173 is implemented by the processing of the CPU 1002 shown in FIG. 12, the programs stored in the ROM 1003, and the like.

The image display unit 174 forms the intermediate image 40 on the screen 15 based on the display information generated by the image generation unit 173 , and projects the laser beam (luminous flux) forming the intermediate image 40 toward the windshield 50 . It is a function of displaying a virtual image 45 by pressing the button. The image display unit 174 is implemented by the processes of the CPU 1002, FPGA 1001, LD driver 1008, MEMS controller 1010 and motor driver 1012 shown in FIG. 12, programs stored in the ROM 1003, and the like.

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

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

Next, a detailed functional configuration of the display brightness control section 178 will be described. 14 is a diagram illustrating an example of a detailed functional configuration of a display brightness control unit according to the first embodiment; FIG. Display brightness control unit 178 includes brightness information acquisition unit 81 , sampling cycle management unit 82 , storage/readout unit 83 , brightness change detection unit 84 , display brightness determination unit 85 and storage unit 800 .

The brightness information acquisition unit 81 has a function of acquiring brightness information 450 including brightness data detected by the brightness sensor 70 from the brightness sensor 70 . The luminance data detected by the luminance sensor 70 is data indicating the luminance value (illuminance value) within the luminance detection area 300 . The luminance information acquisition unit 81 acquires the luminance information 450 at a specific sampling period (sampling time t). The brightness information acquisition unit 81 is an example of acquisition means.

The sampling period management unit 82 has a function of managing a sampling period for detecting luminance data by the luminance sensor 70 . A sampling period (sampling time t) is preset as a design value. The brightness information acquisition unit 81 acquires brightness information 450 including brightness data detected based on the set sampling period from the brightness sensor 70 .

The sampling period is preferably shorter than the period of periodic noise that occurs in the background luminance. The period of periodic noise generated in the background luminance is, for example, the blinking period of a direction indicator (blinker) of an automobile. Also, the period of the periodic noise generated in the background luminance may be the blinking period of the lights blinking on the road shoulder, the driving period of the wipers of the automobile, or the like. Note that the periodic noise is not limited to this, and may be a sudden change in luminance that occurs in a relatively short period detected by the luminance sensor 70 . The luminance sensor 70 can detect luminance changes that are undesirable for the observer 3 by sampling luminance data at intervals shorter than the period of such periodic noise. The brightness information acquisition unit 81 acquires brightness information 450 including brightness data detected based on the set sampling period from the brightness sensor 70 .

The storage/readout unit 83 has a function of storing various data in the storage unit 800 or reading out various data from the storage unit 800 . The storage/readout unit 83 has a function of storing the brightness information 450 acquired by the brightness information acquisition unit 81 in the brightness information management table 400 of the storage unit 800 . The storage/readout unit 83 is an example of storage control means. The storage unit 800 also stores a brightness information management table 400 and allowable delay time information 90 . Details of the luminance information management table 400 and the allowable delay time information 90 will be described later.

The brightness change detection unit 84 has a function of detecting a brightness change in the background brightness. For example, the brightness change detection unit 84 compares the brightness value indicated by the brightness information 450 acquired by the brightness information acquisition unit 81 with the brightness value indicated by the brightness information 450 stored in the brightness information management table 400, and determines a predetermined value. If there is a difference greater than or equal to the value, detect a luminance change in the background luminance. Further, when the luminance change detection unit 84 detects a luminance change in the background luminance, the luminance change detection unit 84 determines whether the background luminance has increased or decreased. A predetermined value for detecting luminance change is stored in the display device 10A in advance as a set value. The predetermined value for detecting changes in brightness is set to a value that allows detection of sudden changes in background brightness caused by sunlight, headlights of oncoming vehicles, or the like, for example. The brightness change detection section 84 is an example of detection means.

The display brightness determination unit 85 has a function of determining the display brightness of the display information output from the display device 10A. For example, when the brightness change detection unit 84 detects a brightness change in the background brightness, the display brightness determination unit 85 determines that the delay time until the display brightness corresponds to the background brightness is within the allowable delay time T or within the allowable delay time T The display brightness information 500 indicating the display brightness is determined so as to be shorter.

Specifically, the display brightness determination unit 85 determines the number of delay consideration processing of the brightness information 450 based on the sampling period (sampling time t) so that the display brightness becomes the brightness value of the background brightness within the allowable delay time T. Identify. Further, the display brightness determination unit 85 determines display brightness information 500 indicating the display brightness of the display information (virtual image 45) based on the representative value of the brightness information 450 stored in the brightness information management table 400, for example. The representative value of the luminance information 450 is a numerical value that serves as a scale indicating the characteristics and trends of the values of the luminance information 450 stored in the luminance information management table 400 . A representative value of the luminance information 450 is, for example, an average value or median value of the luminance information 450 stored in the luminance information management table 400 . The display brightness determination unit 85 is an example of determination means.

○Brightness Information Management Table Here, details of the brightness information management table stored in the storage unit 800 will be described with reference to FIG. 15 . FIG. 15 is a diagram illustrating an example of a luminance information management table according to the first embodiment; The brightness information management table 400 is a buffer area having a fixed size for storing the brightness information 450 acquired by the brightness information acquisition section 81 . The luminance information management table 400 is an example of a storage area.

The brightness information management table 400 stores the brightness information 450 acquired by the brightness information acquiring section 81 along the acquired time series. In the brightness information management table 400 shown in FIG. 15, the storage/reading unit 83 stores the acquired brightness information 450 in order from the area of the sampling number (m) "1".

Since the brightness information management table 400 has a finite size, there is no free space when the sampling number (m) reaches the upper limit. Therefore, when the storage/reading unit 83 determines that the brightness information management table 400 has no free space, it deletes the oldest brightness information 450 . That is, the storage/readout unit 83 deletes the luminance information 450 stored in the area of the sampling number (m) “1” of the luminance information management table 400 and stores it in the areas after the sampling number (m) “2”. The sampling number (m) of the obtained brightness information 450 is incremented by one.

Then, the storage/readout unit 83 stores the newly acquired brightness information 450 in the area at the end of the sampling number (m). For example, when the upper limit of the sampling number (m) of the luminance information management table 400 is "4". The storage/readout unit 83 stores the newly acquired luminance information 450 in the region of the sampling number (m) “4”.

Although FIG. 15 illustrates an example in which the luminance information 450 includes the luminance value [cd/m ² ] in the luminance information management table 400, the luminance information 450 may include the illuminance value [lx (lux)]. . In this case, the display device 10A acquires the brightness information 450 including the illuminance value [lx] (illuminance data) of the brightness detection area 300 detected by the brightness sensor 70, and stores the acquired brightness information 450 in the brightness information management table 400. Memorize.

○ Allowable Delay Time Information Subsequently, details of the allowable delay time information 90 stored in the storage unit 800 will be described with reference to FIG. 16 . FIG. 16 is a diagram showing an example of permissible delay time information according to the first embodiment. Permissible delay time information 90 gives the observer 3 a sense of discomfort due to the delay time until the display luminance follows the background luminance. This information includes the allowable delay time T set as an allowable range.

The permissible delay time information 90 includes different permissible delay times T according to the luminance change state of the background luminance. Specifically, the allowable delay time information 90 corresponds to a case where the luminance value of the background luminance is increased (dark→bright) and a case where the luminance value of the background luminance is decreased (bright→dark). It contains two different delay tolerances T.

For example, the allowable delay time T corresponding to the case where the luminance value of the background luminance increases (from dark to bright) is 1.7 s. On the other hand, the allowable delay time T corresponding to the case where the luminance value of the background luminance is low (bright→dark) is 2.0 s.

For example, the permissible delay time T is set to a delay time range in which 80% of the observers 3 feel comfortable with the change in display brightness, as statistics of the sensory evaluation of the observers 3 who visually recognize the display information. The display device 10A changes the display brightness so that the display brightness corresponds to the background brightness within the time indicated by the allowable delay time T included in the allowable delay time information 90, thereby reducing discomfort given to the observer 3. It is possible to improve the visibility of the display information while increasing the visibility of the display information.

In addition, the display device 10A uses different allowable delay times T according to the luminance change state of the background luminance (dark→bright, light→dark), so that the display luminance can be adjusted according to the luminance change state of the background luminance. can be made different. Note that the value of the allowable delay time T included in the allowable delay time information 90 is not limited to this, and can be appropriately set and changed by the designer or the like of the display device 10A. Also, the permissible delay time information 90 may include only one permissible delay time T regardless of the luminance change state of the background luminance.

●Control Processing of Display Brightness Next, the control processing of the display brightness of the display information (virtual image 45) in the display device 10A will be described with reference to FIG. FIG. 17 is a flowchart illustrating an example of display brightness control processing in the display device according to the first embodiment. FIG. 17 shows an example in which the display device 10A executes delay consideration processing in which a delay time is provided until the display luminance of the display information follows the background luminance, or smoothing processing that reduces the influence of periodic noise on the background luminance. explain.

In step S101, the brightness information acquisition unit 81 of the display device 10A acquires the brightness information 450 from the brightness sensor 70 (an example of an acquisition step). Specifically, the luminance sensor 70 detects the luminance data of the luminance detection area 300 at a sampling period predetermined by the sampling period management section 82 . The luminance data is the luminance value [cd/m ² ] within the luminance detection area 300 . The brightness data may be the illuminance value [lx] within the brightness detection area 300 . Then, the luminance information obtaining unit 81 obtains luminance information 450 including luminance data detected by the luminance sensor 70 from the luminance sensor 70 .

It should be noted that the sampling period of the luminance data by the luminance sensor 70 and the acquisition period of the luminance information 450 by the luminance information acquisition section 81 do not necessarily have to be the same. In this case, for example, a buffer is provided to temporarily store the luminance data detected by the luminance sensor 70, and the luminance sensor 70 stores (updates) the detected luminance data in the buffer at each sampling cycle. The luminance information acquisition unit 81 may acquire the luminance information 450 including the luminance data stored in the buffer at an acquisition cycle different from the sampling cycle. As an example, the luminance sensor 70 detects luminance data with a period of 200 ms, and the luminance information acquisition section 81 acquires luminance information 450 including the luminance data stored in the buffer with a period of 150 ms.

In step S102, if the brightness information management table 400 has an empty area, the storage/reading unit 83 of the display device 10A shifts the process to step S104. On the other hand, if the brightness information management table 400 has no free space, the storage/readout unit 83 shifts the process to step S103.

Since the brightness information management table 400 is a buffer area having a fixed size, when the number of samples of the stored brightness information 450 reaches the upper limit, there is no free area. Therefore, the display device 10A needs to newly create an area for storing the brightness information 450, and thus determines whether or not there is an empty area in the brightness information management table 400. FIG. For example, if the upper limit of the number of samplings is 4, the brightness information management table 400 shown in FIG. state.

In step S<b>103 , the storage/reading unit 83 of the display device 10</b>A deletes the oldest luminance information 450 stored in the luminance information management table 400 . Specifically, in order to create an empty area in the brightness information management table 400, the storage/reading unit 83 stores in the area of the sampling number (m) “1” included in the brightness information management table 400 shown in FIG. Delete the luminance information 450. When the luminance information 450 is deleted from the luminance information management table 400, the storage/readout unit 83 shifts the process to step S104.

In step S<b>104 , the storage/reading unit 83 of the display device 10</b>A stores the brightness information 450 acquired by the brightness information acquisition unit 81 in the brightness information management table 400 . At this time, new brightness information 450 is stored at the end of the brightness information management table 400 in order to clarify the time series of the acquired brightness information 450 . For example, in the brightness information management table 400 shown in FIG. 15, if the brightness information 450 is stored up to the region of the sampling number (m) “3”, the storage/reading unit 83 stores the newly acquired brightness information 450. , sampling number (m) "4".

In step S105, the display device 10A shifts the process to step S109 when the delay consideration process is being performed. On the other hand, the display device 10A shifts the process to step S106 when the delay consideration process is not performed.

In step S106, the brightness change detection unit 84 of the display device 10A detects a brightness change of a predetermined value or more in the background brightness based on the brightness value [cd/m ² ] indicated by the brightness information 450 acquired by the brightness information acquisition unit 81. is detected, the process proceeds to step S107 (an example of the detection step). Specifically, the luminance change detection unit 84 detects the luminance value [cd/m ² ] indicated by the luminance information 450 newly acquired by the luminance information acquisition unit 81 and the luminance information stored in the luminance information management table 400. The luminance value [cd/m ² ] indicated by 450 is compared, and if there is a difference of a predetermined value or more, a luminance change of a predetermined value or more is detected. A predetermined value for detecting luminance change is stored in the display device 10A in advance as a set value. The predetermined value for detecting changes in brightness is set to a value that allows detection of sudden changes in background brightness caused by sunlight, headlights of oncoming vehicles, or the like, for example.

Further, when detecting a luminance change equal to or greater than a predetermined value in the background luminance, the luminance change detection unit 84 determines the state of the detected luminance change. For example, the luminance change detection unit 84 detects an increase in the luminance value [cd/m ² ] of the background luminance (for example, the luminance change from IL to IH shown in FIG. 11), or the luminance value [cd/m ² ] of the background luminance. (eg, luminance change from IH to IL shown in FIG. 11). Then, the brightness change detection section 84 outputs the determination result to the display brightness determination section 85 .

In step S<b>107 , the display brightness determination unit 85 of the display device 10</b>A reads out the allowable delay time information 90 stored in the storage unit 800 . Specifically, the display luminance determination unit 85 reads the allowable delay time T corresponding to the state of luminance change, which is the determination result of the luminance change detection unit 84 . When the brightness change detection unit 84 determines that the brightness value of the background brightness has increased, the display brightness determination unit 85 reads, for example, the allowable delay time T corresponding to the brightness change “dark→bright” shown in FIG.

In step S108, the display luminance determination unit 85 of the display device 10A specifies the number of times the delay consideration process is performed based on the read delay allowable time T. FIG. The number of delay-consideration processing times indicates the number of times delay-consideration processing is performed in which a delay time within the allowable delay time T is provided and the display luminance follows the background luminance. The delay-consideration processing count may be the same as the number of times the luminance data is sampled by the luminance sensor 70 (sampling count), for example. In this case, the display device 10A specifies the number of times the luminance data is sampled based on the read allowable delay time T. FIG. The display luminance determining unit 85 specifies the delay-considering processing count n so as to satisfy the condition of Expression 1 below, where t is the sampling time (sampling cycle) and n is the delay-considering processing count.

For example, when T=1400 ms and sampling time t=250 ms, T/t=5.6. In this case, the display device 10A specifies the delay-consideration processing count n as 5 or less. As a result, the time (delay time) required for the display brightness to follow the brightness value [cd/m ² ] of the background brightness is within the allowable delay time T. FIG. As described above, when the luminance data sampling period by the luminance sensor 70 and the luminance information acquisition unit 81 acquisition period of the luminance information 450 are different, the sampling time t is may be the interval (time) of the acquisition cycle of .

Here, the display device 10A may require a predetermined processing time d until the brightness data detected by the brightness sensor 70 is reflected in the display brightness of the display information. The treatment time d is the time until the brightness data detected by the brightness sensor 70 is acquired as the brightness information 450 by the brightness information acquisition unit 81 (communication time between the brightness sensor 70 and the display device 10A). Calculation time of the display brightness information 500 by using the display brightness information 500, time until the display information (virtual image 45) is projected and displayed, and the like are included.

In this case, the display device 10A may set the delay-consideration processing count n so as to satisfy the condition of Expression 2 below. As a result, the display device 10A calculates the delay time in consideration of the internal processing time, so it is possible to improve the accuracy of the display brightness control process.

In this manner, the display brightness determining unit 85 specifies the number of delay consideration processing times n so that the delay time until the display brightness follows the background brightness is within the delay allowable time T. Therefore, the display device 10A can perform natural display that does not give the observer 3 a sense of discomfort even when a sudden change in background luminance occurs. Although the case where the sampling period (sampling time t) of luminance data is constant has been described, the sampling period (sampling time t) may be changed. In this case, the display device 10A specifies the delay-consideration processing count n based on the sampling time t at the time of sampling the luminance data so as to satisfy the condition of Expression 1 or Expression 2.

In step S109, the display brightness determination unit 85 of the display device 10A determines the display brightness information 500 using the representative value of the brightness information 450 stored in the brightness information management table 400 (an example of the determination step). Specifically, the display brightness determination unit 85 calculates a representative value of the brightness information 450 stored in the brightness information management table 400 . The representative value of the brightness information 450 is, for example, the average value or median value of the brightness values [cd/m ² ] included in the brightness information 450 stored in the brightness information management table 400 .

Here, the display brightness determining unit 85 determines the display brightness information 500 by using the representative value of the brightness information 450 corresponding to the specified delay-consideration process number n among the brightness information 450 stored in the brightness information management table 400. may decide. Further, the display brightness determination unit 85 may determine the display brightness information 500 using a representative value of all brightness information 450 stored in the brightness information management table 400 . The display device 10A can smooth the change in display luminance as the number of pieces of luminance information 450 used for determining the display luminance information 500 increases.

Note that when the luminance data detected by the luminance sensor 70 is the illuminance value [lx], the display luminance determining unit 85 calculates a representative value of the illuminance value [lx] included in the luminance information 450, and converts the calculated value to , into luminance values [cd/m ² ]. The conversion process from the illuminance value [lx] to the luminance value [cd/m ² ] is performed, for example, by multiplying the illuminance value [lx] calculated as the representative value by a predetermined constant. Further, when the luminance data detected by the luminance sensor 70 is an illuminance value [lx], the display luminance determination unit 85 converts the illuminance value [lx] included in the luminance information 450 into a luminance value, and then converts the luminance A representative value of the values may be calculated.

In step S<b>110 , the display brightness determination unit 85 of the display device 10</b>A outputs the determined display brightness information 500 to the image generation unit 173 . The image generator 173 reflects the value of the display luminance indicated by the display luminance information 500 in the display luminance of the display information (virtual image 45). Then, the image display unit 174 displays the display information using the display luminance indicated by the display luminance information 500 (an example of the display step).

In step S111, the display device 10A causes the process to proceed to step S114 when n times of delay consideration processing specified by the display brightness determining unit 85 have been completed. In step S114, the display brightness control unit 178 of the display device 10A repeats the process from step S101 when continuing to control the display brightness. On the other hand, if the display luminance control unit 178 does not continue controlling the display luminance, the process ends.

In step S111, the display device 10A repeats the process from step S101 when the delay consideration process specified by the display luminance determination unit 85 is being performed n times. Then, the display device 10A repeats the specified delay consideration process n times, for example, as shown in FIG. The display brightness is made to correspond to the brightness value [cd/m ² ] of the background brightness. Therefore, even when a sudden change in background luminance is detected, the display device 10A changes the display luminance with an appropriate delay, thereby reducing the discomfort given to the observer 3 and changing the display luminance to the background luminance. can be followed.

In the processing of step S<b>109 , the display brightness determining unit 85 calculates the representative value of the brightness information 450 included in the brightness information management table 400 as the display brightness information 500 . The value to be set is not limited to this. The display brightness information 500 only needs to correspond to the brightness value [cd/m ² ] of the background brightness in the n-th delay consideration process. In this case, the display brightness information 500 in the 1st to n-1th delay consideration processes may be appropriately set so that the brightness value [cd/m ² ] changes stepwise.

Note that the display device 10A updates the brightness information management table 400 in steps S101 to S104 at the sampling cycle of the brightness data from the brightness sensor 70, and performs the processing from step S105 onward at a processing cycle different from the sampling cycle. may be configured to perform the processing of In this case, the sampling time t shown in Equation 1 above may be the interval (time) of the processing cycle in the processing after step S105.

Next, a description will be given of processing when a rapid luminance change is not detected in the display device 10A. The display device 10A improves the visibility of display information by smoothing the luminance information 450 when a rapid change in background luminance is not detected. In step S106, the luminance change detection unit 84 of the display device 10A does not detect a luminance change equal to or greater than a predetermined value based on the luminance value [cd/m ² ] indicated by the luminance information 450 acquired by the luminance information acquisition unit 81. If so, the process proceeds to step S112.

In step S112, the display brightness determining unit 85 of the display device 10A uses the brightness information 450 stored in the brightness information management table 400 to determine the display brightness information 500 indicating the display brightness of the display information (virtual image 45). Specifically, for example, the display brightness determination unit 85 calculates an average value of the brightness information 450 stored in the brightness information management table 400 and determines the calculated average value as the display brightness information 500 . In addition, the display luminance determining unit 85 calculates, for example, the median value of the luminance information 450 stored in the luminance information management table 400 and determines the calculated median value as the display luminance information 500 .

Here, when the display device 10A performs the processing up to step S104, the brightness information management table 400 stores the number of samples (buffer size ) is held. The display brightness determination unit 85 determines display brightness information 500 indicating the display brightness of the display information based on the representative value of all the brightness information 450 during the above time.

In step S<b>113 , the display brightness determination unit 85 of the display device 10</b>A outputs the determined display brightness information 500 to the image generation unit 173 . The image generator 173 reflects the value of the display brightness indicated by the display brightness information 500 in the display brightness of the display information (virtual image 45). Then, the image display unit 174 displays the display information using the display brightness indicated by the display brightness information 500 (an example of the display step).

In step S114, the display brightness control unit 178 of the display device 10A repeats the process from step S101 when continuing to control the display brightness. On the other hand, if the display luminance control unit 178 does not continue controlling the display luminance, the process ends.

In this way, the display device 10A controls the display luminance of the display information based on the representative value of the luminance information 450 acquired along the time series, thereby reducing the influence of background luminance noise that is undesirable for the observer 3. can be reduced. In addition, the display device 10A can suppress the delay until the acquired brightness information 450 is reflected in the display brightness by repeating addition or deletion of the acquired brightness information 450 in time series, thereby reducing the background brightness. noise can be reduced.

In step S112 of FIG. 17, the display luminance determination unit 85 calculates the average value of the luminance information 450, but the display luminance determination unit 85 calculates the average value of the luminance information 450. may be used to determine the display luminance information 500 . Furthermore, the display brightness determination unit 85 may determine, as the display brightness information 500, a value obtained by multiplying the calculated average value or median value by a predetermined constant.

Concrete Example Here, a concrete example of sudden luminance change in the field of view of the driver (observer 3) will be described with reference to FIGS. 18 and 19. FIG. FIG. 18 is a diagram for explaining a specific example (part 1) of the influence of sudden luminance changes in the field of view of the observer. The image shown in FIG. 18(a) is a landscape image (background image) in front captured using a drive recorder attached to a vehicle. FIG. 18(a) shows a state in which sunlight penetrates into the inside of a multi-storey parking lot that has an atrium structure. FIG. 18(b) shows luminance data 600 detected in the luminance detection area 300 and processed data 650 obtained by performing display luminance control processing based on the luminance data 600 in the situation of the image shown in FIG. 18(a). show. In the graph of FIG. 18(b), the vertical axis indicates the luminance value [cd/m ² ] of the detected luminance data, and the horizontal axis indicates the time when the luminance data was acquired.

The luminance sensor 70 mounted on the vehicle detects a sudden change in background luminance as shown in FIG. In the situation shown in FIG. 18(a), the inside of the multi-storey parking lot itself is dark, so the luminance contrast increases and the effect of sudden noise increases.

At this time, the display luminance value obtained by performing only the smoothing process (for example, the process of step S112 in FIG. 17) on the sampled luminance data is smoother than the sampled luminance data (actual background luminance). shows a large luminance change. However, the display brightness that has undergone only the smoothing process still has noise due to abrupt changes in the background brightness, and the effect of this noise gives the observer 3 a sense of discomfort in the display.

On the other hand, the display luminance values obtained by subjecting the sampled luminance data to delay-consideration processing (for example, the processing of steps S107 to S109 in FIG. 17) are affected by sudden noise caused by sudden changes in background luminance. However, it can be seen that it is rarely seen. This is because, in the display device 10A, the change in display luminance is delayed with respect to the change in background luminance by the delay consideration process, thereby attenuating the peak of the luminance value [cd/m ² ] due to the influence of sudden noise. Because

FIG. 19 is a diagram for explaining a specific example (Part 2) of the influence of sudden luminance changes in the field of view of the observer. The image shown in FIG. 19( a ) is, like FIG. 18( a ), a landscape image (background image) in front captured using a drive recorder attached to a vehicle. FIG. 19(a) shows a situation in which a running vehicle moves from the shade to the sun. FIG. 19(b) shows luminance data 600 detected in the luminance detection area 300 and processed data 650 obtained by performing display luminance control processing based on the luminance data 600 in the situation of the image shown in FIG. 19(a). show. In the graph of FIG. 19B, the vertical axis indicates the luminance value [cd/m ² ] of the detected luminance data, and the horizontal axis indicates the time when the luminance data was obtained.

The luminance sensor 70 mounted on the vehicle detects a sudden change in background luminance as shown in FIG. At this time, the value of the display luminance obtained by performing only the smoothing process (for example, the process of step S112 in FIG. 17) on the sampled luminance data is gentler than the actual background luminance indicated by the sampled luminance data. shows a large luminance change.

In addition, the display luminance value subjected to the delay consideration processing (for example, the processing of steps S107 to S109 in FIG. 17) on the sampled luminance data is higher than the display luminance value subjected to only smoothing processing. It shows a more gentle luminance change. This is because in the display device 10A, a delay time is provided until the display luminance follows the background luminance by the delay consideration process.

In the situation shown in FIG. 19, the display device 10A performs the delay-consideration process to moderate the luminance change of the display luminance as compared with the case where only the smoothing process is performed. Discomfort in display can be reduced. On the other hand, in the situation shown in FIG. 19, the change in luminance value of the background luminance is large, so the delay time is longer than when only the smoothing process is performed. If the delay time is too long, the observer 3 will feel uncomfortable. In the example shown in FIG. 19(b), the display device 10A makes the display brightness correspond to the brightness value of the background brightness with a delay time of about 0.8 s with respect to the allowable delay time T=1.4 s.

18 and 19, the influence of incident light in a multi-storey parking lot and backlight due to movement from shade to sunshine has been described, but the display brightness control processing according to the present embodiment is not limited to these situations. . The display luminance control processing according to the present embodiment can be applied in various situations in which sudden luminance changes occur.

Allowable Delay Time Subsequently, the allowable delay time in the display system 1A will be described with reference to FIGS. 20 and 21. FIG. 20 and 21 show statistical results of sensory evaluations conducted by the inventors on a subject (observer 3) who visually recognizes displayed information.

FIG. 20 is a diagram for explaining the allowable delay time in the display system according to the first embodiment; The graph shown in FIG. 20(a) shows the relationship between the change time of the display brightness and the sense of discomfort given to the subject (observer 3) when the background brightness is greatly changed from dark to bright. In the graph of FIG. 20( a ), the vertical axis indicates the probability (%) that the subject (observer 3) does not feel discomfort with respect to the luminance change of the display luminance as statistics of the sensory evaluation of the subject (observer 3), and the horizontal axis The axis indicates the delay time (s) of luminance change in display luminance.

FIG. 20(a) shows that when the luminance value of the background luminance is changed from 100 [cd/m ² ] to 500 [cd/m ² ], 100 [cd/m ² ] to 1000 [cd/m ² ] Statistical results are shown for three luminance changes when changing from 100 [cd/m ² ] to 1800 [cd/m ² ]. In either case, it can be seen that the longer the delay time of the luminance change of the display luminance, the lower the probability that the subject (observer 3) will not feel uncomfortable with the luminance change of the display luminance.

FIG. 20(b) shows the delay time at which 80% of the subjects (observer 3) feel comfortable with the change in display brightness in the graph of FIG. 20(a). As shown in FIG. 20(b), it can be seen that the greater the luminance change in the background luminance, the shorter the delay time that does not give the subject (observer 3) a sense of discomfort. In the display device 10A, the delay time when the background luminance is changed from 100 [cd/m ² ] to 1800 [cd/m ² ], which is the shortest delay time that does not cause discomfort to the subject (observer 3), is It is preferable to set the allowable delay time T. In this case, the allowable delay time T=1.45 s.

Next, with reference to FIG. 21, a case where the background luminance is greatly changed from a bright situation to a dark situation will be described. The graph shown in FIG. 21(a) shows the relationship between the change time of the display brightness and the sense of discomfort given to the subject (observer 3) when the background brightness is greatly changed from bright to dark. In the graph of FIG. 21( a ), the vertical axis represents the probability (%) that the subject (observer 3) does not feel discomfort with respect to the luminance change of the display brightness as statistics of the subject's (observer 3) sensory evaluation, and the horizontal axis. The axis indicates the delay time (s) of luminance change in display luminance.

FIG. 21(a) shows 1000 [cd/m ² ] to 100 [cd/m ² ] when the luminance value of the background luminance is changed from 500 [cd/m ² ] to 100 [cd/m ² ]. Statistical results are shown for three luminance changes when changing from 1800 [cd/m ² ] to 100 [cd/m ² ]. In either case, it can be seen that the longer the delay time of the luminance change of the display luminance, the lower the probability that the subject (observer 3) will not feel uncomfortable with the luminance change of the display luminance.

FIG. 21(b) shows the delay time at which 80% of the subjects (observer 3) felt that the change in display luminance was comfortable in the graph of FIG. 21(a). As shown in FIG. 21B, it can be seen that the smaller the luminance change in the background luminance, the shorter the delay time that does not give the subject (observer 3) a sense of discomfort. In the display device 10A, the delay time when the background luminance is changed from 500 [cd/m ² ] to 100 [cd/m ² ], which is the shortest delay time that does not cause discomfort to the subject (observer 3), is It is preferable to set the allowable delay time T. In this case, the allowable delay time T=1.9 s.

In this manner, the display device 10A sets the delay time until the display luminance of the display information (virtual image 45) follows the background luminance to be within the delay allowable time T at which the observer 3 feels comfortable with the change in the display luminance. to Note that the probability that the observer 3 does not feel uncomfortable with the change in display brightness, which is used as a statistical value for setting the allowable delay time T, is not limited to 80% and can be adjusted as appropriate.

Further, as shown in FIGS. 20 and 21, the delay time at which the observer 3 does not feel uncomfortable with the change in display luminance is different. Therefore, the display device 10A sets different permissible delay times T according to the state of luminance change, like the permissible delay time information 90 shown in FIG. , the display brightness can be changed. Note that the allowable delay time T may be set to a different value depending not only on the state of luminance change, but also on the magnitude of luminance change as shown in FIGS.

Effects of the First Embodiment As described above, when the display system 1A according to the first embodiment detects a luminance change in the background luminance, a delay time within the allowable delay time T is provided to reduce the display luminance. change step by step. Therefore, the display system 1A can improve visibility of display information while reducing discomfort given to the observer 3 even when a sudden change in background luminance occurs. Further, when the luminance change of the background luminance is not detected, the display system 1A determines the display luminance information 500 using the representative value of the luminance information 450 stored in the display device 10A, thereby detecting the presence or absence of a sudden luminance change. The display brightness control process can be continuously performed without depending on the display brightness.

●Modified example of the first embodiment●
Next, a configuration of a modified example of the first embodiment will be described. The same reference numerals are given to the same configurations and the same functions as those of the first embodiment, and the description thereof is omitted. The display system according to the modification of the first embodiment is a system in which the positional relationship between the luminance detection area 300 by the luminance sensor 70 and the display background area 350 is different from that of the first embodiment.

FIG. 22 is a diagram for explaining an example of the relationship between the luminance detection area and the display background area according to the modification of the first embodiment; 10, the luminance detection area 300 includes the display background area 350 in the first embodiment, but the positional relationship between the luminance detection area 300 and the display background area 350 is not necessarily It is not limited to this example.

In the example shown in FIG. 22A, part of the luminance detection area 301 and part of the display background area 351 are superimposed. Similarly, in the example shown in FIG. 22(b), part of the luminance detection area 302 and part of the display background area 352 are superimposed. In the example shown in FIG. 22(b), the range of the luminance detection area 302 outside the display background area 352 is smaller than that in FIG. 22(a) compared to that in FIG. 22(a). When the positional relationship shown in FIG. 22(b) is applied, the display device 10A reduces the possibility of detecting noise that does not contribute to luminance change in the display background region 352 compared to the example of FIG. 22(a). be able to.

In the example shown in FIG. 22(c), the luminance detection area 303 is included in the display background area 353. In the example shown in FIG. When the display device 10A applies the positional relationship shown in FIG. Changes in the background brightness of the display background area 353 can be accurately reflected.

The display system 1A can apply the display luminance control process shown in FIG. 17 in any of the cases shown in FIGS. Although FIGS. 10 and 22 show examples in which at least a portion of the luminance detection area and the display background area overlap, the luminance detection area and the display background area do not necessarily have to overlap.

●Second Embodiment●
Next, the configuration of the second embodiment will be described. The same reference numerals are given to the same configurations and the same functions as those of the first embodiment, and the description thereof is omitted. The display system 1B according to the second embodiment determines, as a fixed value, the display brightness information 500 for the number of specified delay consideration processes based on the brightness value [cd/m ² ] of the background brightness, and the determined display brightness Information 500 is used to change the display brightness in steps.

FIG. 23 is a flowchart illustrating an example of display brightness control processing in the display device according to the second embodiment. Note that the processing from step S201 to step S204 shown in FIG. 23 is the same as the processing from step S101 to step S104 shown in FIG. 17, so description thereof will be omitted. As in the first embodiment, the value included in the luminance information 450 is not limited to the luminance value [cd/m ² ], and may be the illuminance value [lx].

In step S205, the display device 10B shifts the process to step S210 when the delay consideration process is being performed. On the other hand, if the delay consideration process is not performed, the display device 10B shifts the process to step S206.

In step S206, the brightness change detection unit 84 of the display device 10B detects a brightness change in the background brightness based on the brightness value [cd/m ² ] indicated by the brightness information 450 acquired by the brightness information acquisition unit 81. , the process proceeds to step S207. Specifically, the luminance change detection unit 84 detects the luminance value [cd/m ² ] indicated by the luminance information 450 newly acquired by the luminance information acquisition unit 81 and the luminance information stored in the luminance information management table 400. The luminance value [cd/m ² ] indicated by 450 is compared, and if there is a difference of a predetermined value or more, a luminance change of a predetermined value or more is detected. A predetermined value for detecting luminance change is stored in advance as a set value in the display device 10B. The predetermined value for detecting changes in brightness is set to a value that allows detection of sudden changes in background brightness caused by sunlight, headlights of oncoming vehicles, or the like, for example.

Further, when detecting a luminance change equal to or greater than a predetermined value in the background luminance, the luminance change detection unit 84 determines the state of the detected luminance change. For example, the luminance change detection unit 84 detects an increase in the luminance value [cd/m ² ] of the background luminance (for example, the luminance change from IL to IH shown in FIG. 11), or the luminance value [cd/m ² ] of the background luminance. (eg, luminance change from IH to IL shown in FIG. 11). Then, the brightness change detection section 84 outputs the determination result to the display brightness determination section 85 .

On the other hand, in step S206, the luminance change detection unit 84 of the display device 10B detects a luminance change equal to or greater than a predetermined value based on the luminance value [cd/m ² ] indicated by the luminance information 450 acquired by the luminance information acquisition unit 81. is not detected, the process proceeds to step S212. The contents of the luminance data smoothing process in steps S212 to S214 are the same as those in steps S112 to S114 shown in FIG.

In step S<b>207 , the display luminance determination unit 85 of the display device 10</b>B reads out the allowable delay time information 90 stored in the storage unit 800 . Specifically, the display luminance determination unit 85 reads the allowable delay time T corresponding to the state of luminance change, which is the determination result of the luminance change detection unit 84 . When the brightness change detection unit 84 determines that the brightness value of the background brightness has increased, the display brightness determination unit 85 reads, for example, the allowable delay time T corresponding to the brightness change “dark→bright” shown in FIG.

In step S<b>208 , the display brightness determination unit 85 of the display device 10</b>B specifies the delay consideration processing count n of the brightness information 450 for determining the display brightness information 500 based on the read allowable delay time T. The method of specifying the delay-consideration processing count n is the same as the content shown in step S108 of FIG. 17, and thus the description thereof is omitted.

In step S209, the display brightness determination unit 85 of the display device 10B changes the display brightness stepwise so that the brightness value [cd/m ² ] corresponding to the background brightness is reached at the n-th specified number of delay-consideration processes. Therefore, the display brightness information 500 for n times is determined as a fixed value. Specifically, for example, when the luminance value indicated by the newly acquired luminance information 450 is 1000 [cd/m ² ] and the specified number of delay consideration processing times is 4, the display luminance determining unit 85 The display brightness information 500 for four times is specified so that the brightness value indicated by the display brightness information 500 of is 1000 [cd/m ² ]. In this case, the display brightness determination unit 85 adds a predetermined constant corresponding to each delay consideration processing count to the difference value between the current display brightness and the background brightness. Then, the display luminance determining unit 85 determines the display luminance information 500 corresponding to the first to fourth delay consideration processing times by adding the integrated value to the current display luminance value.

For example, the first constant is 0.16, the second constant is 0.256, the third constant is 0.655, the fourth constant is 1.0, and the current display luminance is 500 [cd/m ² ] and the current background luminance is 1000 [cd/m ² ]. In this case, the display luminance information 500 corresponding to the number of times of the first delay consideration process is obtained by multiplying the difference value 500 between the current background luminance and the display luminance by the first constant 0.16 ( 80) is added to the current display luminance value, resulting in "580 [cd/m ² ]". Similarly, the display brightness information 500 corresponding to the second delay-consideration processing count is “628 [cd/m ² ]”, and the display brightness information 500 corresponding to the third delay-consideration processing count is “827. 5 [cd/m ² ]", and the display brightness information 500 corresponding to the fourth delay consideration processing count is "1000 [cd/m ² ]".

In this way, the display brightness determination unit 85 of the display device 10B adjusts the specified display brightness information 500 for the n-th delay consideration process to the brightness value [cd/m ² ] of the current background brightness. The display brightness information 500 corresponding to the number of delay-consideration processes is changed stepwise.

In step S<b>210 , the display brightness determination unit 85 of the display device 10</b>B outputs the determined display brightness information 500 to the image generation unit 173 . The image generator 173 reflects the value of the display luminance indicated by the display luminance information 500 in the display luminance of the display information (virtual image 45). Then, the image display unit 174 uses the display brightness indicated by the display brightness information 500 to display the display information.

In step S211, the display device 10B shifts the process to step S214 when n times of the delay consideration process specified by the display brightness determination unit 85 have been completed. In step S214, the display brightness control unit 178 of the display device 10B repeats the process from step S201 when continuing to control the display brightness. On the other hand, if the display luminance control unit 178 does not continue controlling the display luminance, the process ends.

In step S211, the display device 10B repeats the process from step S201 when the delay consideration process specified by the display luminance determination unit 85 is being performed n times. Then, the display device 10B repeats the specified delay consideration process n times, for example, as shown in FIG. The display brightness is made to correspond to the brightness value of the background brightness. Therefore, even when a sudden change in background luminance is detected, the display device 10B changes the display luminance with an appropriate delay so that the display luminance follows the background luminance without giving the observer 3 a sense of discomfort. can be made

Effects of the Second Embodiment As described above, the display system according to the second embodiment causes the display luminance to follow the background luminance within the allowable delay time T. is determined based on the luminance value [cd/m ² ] of the background luminance, and the determined display luminance information 500 is used to change the display luminance stepwise. Therefore, the display system 1B can use the delay time within the allowable delay time T to achieve a more natural change in display brightness.

●Summary●
As described above, the display device according to one embodiment of the present invention is the display device 10A that displays the virtual image 45 (an example of display information) visually recognized by the observer 3 in front of the moving body. Luminance information 450 indicating the luminance of a luminance detection area 300 (an example of a peripheral area) including at least part of a display background area 350 (an example of a display area) that serves as a background is acquired at a specific sampling time t (an example of a cycle). Then, based on the obtained luminance information 450, the luminance change of the luminance detection area 300 is detected. Then, when the display device 10A detects a luminance change, the delay time until the display luminance of the virtual image 45 corresponds to the luminance of the luminance detection area 300 is within the allowable delay time T or shorter than the allowable delay time T. , the display brightness information 500 indicating the display brightness of the virtual image 45 is determined, and the virtual image 45 is displayed using the determined display brightness information 500 . Therefore, the display device 10A can improve the visibility of display information by suppressing changes in display luminance that are undesirable for the observer 3 in response to sudden changes in background luminance.

Further, in the display device according to the embodiment of the present invention, the delay time until the display brightness of the virtual image 45 corresponds to the brightness of the brightness detection region 300 (an example of the peripheral region) is less than or equal to the allowable delay time T or equal to or greater than the allowable delay time T. The delay-consideration processing count n (an example of the acquisition count) of the luminance information 450 based on the sampling time t is specified so as to be shorter than T. Therefore, the display device 10A sets the delay time until the display luminance of the display information corresponds to the background luminance within the allowable delay time T at which the observer 3 does not feel uncomfortable with the change in the display luminance. visibility can be improved.

Furthermore, the display device according to one embodiment of the present invention specifies the delay-consideration processing count n (an example of the acquisition count) so as to satisfy the condition of (Equation 1) below. In the following (Equation 1), n represents the number of delay consideration processes, t represents a sampling time (an example of a period), and T represents an allowable delay time.

Therefore, the display device 10A keeps the delay time for the display luminance to follow the background luminance within the range of the allowable delay time T, thereby reducing the display luminance to the extent that the observer 3 does not feel uncomfortable. Background luminance can be tracked.

Further, when detecting a luminance change in the luminance detection region 300 (an example of the peripheral region), the display device according to an embodiment of the present invention determines the state of the detected luminance change, and responds to the determined state of the luminance change. The display brightness information 500 is determined based on the allowable delay time T. Therefore, the display device 10A uses different allowable delay times T according to the luminance change state of the background luminance (dark→bright, bright→dark), thereby varying the delay time required to change the display brightness. can be done.

Furthermore, the display system according to one embodiment of the present invention scans the screen 15 two-dimensionally with light emitted from the screen 15 (an example of an optical element) that emits light and the light source device 11 (an example of a light source). and a display device 10</b>A that displays a virtual image 45 formed by divergent light diverged from the screen 15 . The display system 1A also includes a brightness sensor 70 (an example of a detection device) that detects the brightness of a brightness detection area 300 (an example of a peripheral area), and a windshield 50 (a reflective member) that reflects divergent light emitted from the screen 15. an example), and a free-form surface mirror 30 (an example of an imaging optical system) that projects divergent light diverged from the screen 15 toward the windshield 50 to form a virtual image 45 . Therefore, the display system 1A can improve the visibility of display information by suppressing changes in display brightness that are undesirable for the observer 3 in response to sudden changes in background brightness.

A display brightness control method according to an embodiment of the present invention is a display brightness control method executed by the display device 10A that displays a virtual image 45 (an example of display information) visually recognized by the observer 3 in front of a moving object. acquires luminance information 450 indicating the luminance of a luminance detection area 300 (an example of a peripheral area) including at least a portion of a display background area 350 (an example of a display area) serving as a background of the virtual image 45 at a specific cycle. a detection step of detecting a luminance change in the luminance detection area 300 based on the acquired luminance information 450; ) is equal to or less than the allowable delay time T or shorter than the allowable delay time T; and a display step of displaying the virtual image 45 using the luminance information 500 . Therefore, the display brightness control method according to one embodiment of the present invention suppresses changes in display brightness that are undesirable for the observer 3 in response to sudden changes in background brightness, thereby improving the visibility of display information. be able to.

● Supplement ●
Although a display device, a display system, a moving object, a display brightness control method, and a program according to an embodiment of the present invention have been described, the present invention is not limited to the above-described embodiments, and a person skilled in the art can It can be changed within the conceivable range.

Further, the display device according to one embodiment of the present invention has been described as a HUD device mounted on an automobile, which is an example of a moving body, but the display device according to one embodiment of the present invention may be, for example, a head It may be a mount display device or the like. In this case, the display device according to one embodiment of the present invention applied to the head-mounted display device superimposes and displays the external world and the virtual image. Furthermore, the display device according to one embodiment of the present invention can also be applied to a device having a display system that transmits the display surface so that the scenery (background) of the outside world can be seen, such as a see-through display.

Furthermore, the functions of each embodiment can be realized by a computer-executable program written in a legacy programming language such as assembler, C, C++, C#, Java (registered trademark), an object-oriented programming language, or the like. Programs to perform the functions of may be distributed over telecommunications lines.

Programs for executing the functions of each embodiment include ROM, EEPROM (Electrically Erasable Programmable Read-Only Memory), EPROM (Erasable Programmable Read-Only Memory), flash memory, flexible disk, CD (Compact Disc)- Storing and distributing in device-readable recording media such as ROM, CD-RW (Re-Writable), DVD-ROM, DVD-RAM, DVD-RW, Blu-ray disc, SD card, MO (Magneto-Optical disc), etc. can also

Furthermore, part or all of the functionality of each embodiment can be implemented on a programmable device (PD), such as an FPGA (Field Programmable Gate Array), or can be implemented as an ASIC, and each embodiment Circuit configuration data (bit stream data) downloaded to the PD to realize the function of PD, HDL (Hardware Description Language) for generating circuit configuration data, VHDL (Very High Speed Integrated Circuits Hardware Description Language), It can be distributed on a recording medium as data described in Verilog-HDL or the like.

1, 1A, 1B display system 10, 10A, 10B display device 11 light source device 13 optical deflection device (an example of a scanning unit)
15 screen (an example of an optical element)
30 free-form surface mirror (an example of an imaging optical system)
50 windshield (an example of a reflective member)
70 luminance sensor (an example of a detection device)
81 luminance information acquisition unit (an example of acquisition means)
83 storage/readout unit (an example of storage control means)
84 Luminance change detection unit (an example of detection means)
85 Display brightness determination unit (an example of determination means)
400 luminance information management table (an example of a storage area)

JP 2013-239243 A

Claims (9)

A display device for displaying display information visually recognized by an observer in front of a moving body,
acquisition means for acquiring luminance information indicating luminance of a peripheral area including at least part of a display area serving as a background of the display information in a specific cycle;
detection means for detecting that the change in luminance of the peripheral area is equal to or greater than a predetermined value based on the acquired luminance information;
determining means for determining display luminance information indicating display luminance based on the acquired luminance information;
The determining means
When a luminance change of the predetermined value or more is detected, the display luminance of the display information is adjusted to the surrounding area so that the change in the display luminance is delayed compared to when the luminance change of the predetermined value or more is not detected. determining the display brightness information so that the delay time until it corresponds to the brightness is within or shorter than the allowable delay time set as an allowable range that does not cause discomfort to the observer;
A display device for displaying the display information using the determined display luminance information.
The determining means
specifying the number of acquisition times of the brightness information based on the cycle so that the delay time until the display brightness corresponds to the brightness of the peripheral area is within the allowable delay time or shorter than the allowable delay time;
2. The display device according to claim 1 , wherein said display brightness information is determined such that said display brightness changes stepwise by said number of acquisitions when a brightness change equal to or greater than said predetermined value is detected . 3. The display device according to claim 2, wherein said determining means specifies said number of acquisitions so as to satisfy the following condition (Equation 1).

(In the above (Formula 1), n represents the number of acquisitions, t represents the period, and T represents the allowable delay time.) When the detection means detects the luminance change, the detection means determines the state of the detected luminance change,
4. The display device according to any one of claims 1 to 3, wherein said determining means determines said display brightness information based on said allowable delay time corresponding to said determined state. The display device according to any one of claims 1 to 4, further comprising:
an optical element that diverges light;
a scanning unit that two-dimensionally scans the optical element with light emitted from a light source;
A display device for displaying a virtual image formed by divergent light diverged from the optical element. a display device according to claim 5;
a detection device for detecting the brightness of the peripheral area;
a reflecting member that reflects divergent light diverged from the optical element;
an imaging optical system that projects divergent light diverged from the optical element toward the reflecting member to form a virtual image;
display system. A display system according to claim 6,
The moving body, wherein the reflecting member is a windshield. A display brightness control method executed by a display device for displaying display information visually recognized by an observer in front of a moving object,
an acquiring step of acquiring luminance information indicating luminance of a peripheral area including at least part of a display area serving as a background of the display information at a specific cycle;
a detection step of detecting that a luminance change in the peripheral area is equal to or greater than a predetermined value based on the obtained luminance information;
a determination step of determining display luminance information indicating display luminance based on the acquired luminance information;
a display step of displaying the display information using the determined display luminance information;
The determining step includes:
When a luminance change of the predetermined value or more is detected, the display luminance of the display information is adjusted so that the change in the display luminance is delayed compared to when the luminance change of the predetermined value or more is not detected, and the display luminance of the display information is adjusted to the peripheral area. A display brightness control method for determining the display brightness information so that the delay time until it corresponds to the brightness is within or shorter than the allowable delay time set as an allowable range that does not give discomfort to an observer.
A program that causes a computer to execute the display brightness control method according to claim 8 .

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