JP2020112667A - Virtual image display device - Google Patents

Abstract

To provide a virtual image display device with which the visibility of a virtual display image is good.SOLUTION: The virtual image display device displays a virtual display image VDP by causing the display light of an image to be reflected by a reflection unit. The virtual image display device comprises: an image display panel having a display screen for displaying an image; a backlight having a plurality of lighting segments arranged so as to divide a light source plane and lighting the image display panel from the light source plane; and a backlight control unit for switching between the turned on and turned off states of each lighting segment and locally dimming the backlight. A virtual light source plane mage VLS is formed behind the virtual display image VDP. A virtual line Lv is defined that passes through the virtual display image VDP and an assumed viewpoint position PE that is assumed as the view point of a viewer who views the virtual display image VDP. The backlight control unit turns a lighting segment on that corresponds to an intersection position PC where the virtual line Lv intersects in the virtual light source plane image VLS.SELECTED DRAWING: Figure 6

Description

The disclosure of this specification relates to a virtual image display device.

2. Description of the Related Art Conventionally, there has been known a virtual image display device that displays a display virtual image by reflecting display light of an image by a reflecting portion. The device disclosed in Patent Document 1 includes an image display panel and a backlight. The image display panel has a display screen for displaying an image. The backlight has a plurality of illumination segments arranged so as to divide the light source surface, and illuminates the image display panel from the light source surface. The backlight is locally dimming-controlled by individually switching the lighting state and the non-lighting state of each lighting segment. Here, among the respective illumination segments, only the illumination segment immediately below the area where the image display panel displays the image is selectively turned on.

Japanese Patent No. 6299523

Now, in the virtual image display device that displays the display virtual image by reflecting the display light of the image on the reflecting portion, the brightness of the display virtual image decreases when the viewpoint moves, for example, when the viewer of the display virtual image moves his/her head. Therefore, there is a problem that the visibility is lowered. This problem becomes more serious especially in a mode in which the backlight is locally dimmed.

Specifically, when only the illumination segment immediately below the display portion where the image is displayed on the display screen is turned on as in the device of Patent Document 1, the viewpoint of the viewer shifts from the front and the display virtual image is viewed obliquely. In addition, parallax occurs between the display virtual image and the light source surface virtual image formed behind it. On the extension line of the line of sight from the viewpoint to the display virtual image, the virtual image of the illumination segment may be in the off state. In this case, since the display virtual image is visually recognized as if it is not sufficiently illuminated, there is a concern that the visibility of the display virtual image is reduced.

One of the purposes of the disclosure of this specification is to provide a virtual image display device in which the visibility of a display virtual image is good.

One of the aspects disclosed herein is a virtual image display device that displays a display virtual image (VDP) by reflecting display light of an image on a reflecting portion (3a),
An image display panel (22) having a display screen (22a) for displaying an image,
A backlight (24) having a plurality of illumination segments (25) arranged to divide the light source surface (26) and illuminating the image display panel from the light source surface;
And a backlight control unit (54, 254) for individually switching the lighting state and the extinguishing state of each lighting segment to control the local dimming of the backlight,
A light source surface virtual image (VLS) of the light source surface is formed behind the display virtual image,
When a virtual line (Lv) passing through the display virtual image and the viewpoint assumed position (PE) assumed as the viewpoint of the viewer who visually recognizes the display virtual image is defined,
The backlight control unit turns on the illumination segment corresponding to the intersection position (PC) where the virtual lines intersect in the virtual image of the light source surface.

According to such an aspect, in the backlight, among the plurality of illumination segments arranged so as to divide the light source surface, the virtual light source surface virtual image formed behind the display virtual image corresponds to the intersection position where the virtual lines intersect. The lighting segment is turned on. This virtual line is defined as a line that passes through the display virtual image and the assumed viewpoint position as the viewpoint of the viewer who visually recognizes the display virtual image. That is, the virtual image of the illuminated illumination segment exists on the extension line of the line of sight from the assumed viewpoint position to the display virtual image. Therefore, when the viewer views the display virtual image from the assumed viewpoint position, the display virtual image is visually recognized as if it is illuminated by the backlight. Therefore, even if the backlight is subjected to the local dimming control, the reduction in the brightness of the display virtual image visually recognized from the viewpoint of the viewer is suppressed, so that the visibility of the display virtual image becomes good.

Another one of the aspects disclosed herein is a virtual image display device that displays a display virtual image (VDP) by reflecting the display light of an image on a reflecting section (3a),
An image display panel (22) having a display screen (22a) for displaying an image,
A backlight (24) having a plurality of illumination segments (25) arranged to divide the light source surface (26) and illuminating the image display panel with the light source surface;
A backlight control unit (54) for individually switching the lighting state and the extinguishing state of each illumination segment to control the local dimming of the backlight;
In addition to turning on the illumination segment (25a) immediately below the display portion (P1) of the image, the backlight control unit displays the entire occupied area on the light source surface as the illumination segment not directly below the display portion. The illumination segment (25b) located within a predetermined distance or less in the expansion direction from the region immediately below the part is turned on as the extended lighting region (EJA).

According to such an aspect, in the backlight, in addition to turning on the lighting segment immediately below the display portion of the image among the plurality of lighting segments arranged so as to divide the light source surface, The lighting segment is turned on. The illumination segment of the extended lighting area is an illumination segment whose entire occupation area is not directly below the display portion, and is located within a predetermined distance or less in the extension direction from the area directly below the display portion of the image on the light source surface. Lighting segment. Therefore, when the viewer's viewpoint shifts from the front to the expansion direction and the display virtual image is viewed obliquely, the probability that the virtual image of the illuminated illumination segment exists on the extension line of the line of sight from the viewpoint to the display virtual image is increased. You can Therefore, even if the backlight is subjected to the local dimming control, the display virtual image is visually recognized as being illuminated by the backlight, so that the reduction in the brightness of the display virtual image viewed from the viewpoint of the viewer is suppressed. Therefore, the visibility of the display virtual image is good.

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

It is a figure which shows the mounting state in the vehicle of the HUD apparatus of 1st Embodiment. It is a figure which shows typically the structure of the display of 1st Embodiment. It is a block diagram which shows the relationship between the display and control unit of 1st Embodiment. It is a figure which shows typically the relationship between the light source surface of 1st Embodiment, and a display screen. It is a figure which shows the relationship between the division area of 1st Embodiment, and an expansion determination area. It is a schematic diagram for demonstrating the virtual line of 1st Embodiment. It is a figure for demonstrating the case where it is shifted to the right from the front and the display virtual image is seen diagonally in 1st Embodiment. It is a flowchart by the backlight control part of 1st Embodiment. It is a figure corresponding to FIG. 3 in 2nd Embodiment. It is a figure for demonstrating each parameter and formula of Numerical formula f of 2nd Embodiment. It is a flowchart by the backlight control part of 2nd Embodiment. FIG. 11 is a diagram showing an expansion determination area in an example of Modification 2; FIG. 11 is a diagram showing an extension determination area in another example of Modification 2.

Hereinafter, a plurality of embodiments will be described with reference to the drawings. It should be noted that, in each of the embodiments, corresponding components may be denoted by the same reference numerals, and redundant description may be omitted. When only a part of the configuration is described in each embodiment, the configuration of the other embodiments described above can be applied to the other part of the configuration. In addition, not only the combination of the configurations explicitly described in the description of each embodiment, but if there is no particular problem in the combination, the configurations of the plurality of embodiments can be partially combined even if not explicitly stated. ..

(First embodiment)
As shown in FIG. 1, the virtual image display device according to the first embodiment of the present disclosure is used in a vehicle 1, and a head-up display device (hereinafter, a HUD device) 10 housed in an instrument panel 2 of the vehicle 1 is provided. Is. The HUD device 10 projects the display light of the image toward the reflecting portion 3 a set on the windshield 3 of the vehicle 1. Thereby, the HUD device 10 displays the image as the display virtual image VDP that can be visually recognized by the occupant as the viewer. That is, when the display light of the image reflected by the reflector 3a reaches the visual recognition area EB set inside the vehicle 1, the occupant whose viewpoint is located in the visual recognition area EB can recognize various information. ..

The various information displayed includes, for example, information indicating the state of the vehicle 1 such as vehicle speed and remaining fuel amount, or navigation information such as visibility assistance information and road information.

In the following, unless otherwise specified, the directions of front, rear, upper, lower, left, and right are described with reference to the vehicle 1 on the horizontal plane HP.

The windshield 3 of the vehicle 1 is a translucent plate-shaped member made of, for example, glass or synthetic resin and is arranged above the instrument panel 2. The windshield 3 is arranged so as to be inclined from the instrument panel 2 as it goes from the front to the rear. The windshield 3 has a reflecting portion 3a on which the display light of an image is projected, which is formed in a smooth concave shape or a flat shape. The reflection part 3a may not be provided on the windshield 3. For example, a combiner that is separate from the vehicle 1 may be installed in the vehicle 1 and the combiner may be provided with the reflecting portion 3a.

The visual recognition area EB is a space area where the display virtual image VDP can be visually recognized, and is also called an eye box. The visual recognition area EB is typically set so as to overlap with the eye lip set in the vehicle 1. The eye lip is set in a virtual ellipsoidal shape based on an eye range that statistically represents the spatial distribution of the occupant's eye points (that is, viewpoints). The eye lip is usually set in a space slightly ahead of the headrest of the seat. Then, in the front posture of the occupant (the posture in which the neck is not tilted), since the left eye and the right eye are positioned side by side in the left-right direction, the visual recognition area EB is set to a rectangular shape that is long in the left-right direction with the left-right direction as the longitudinal direction. To be done.

As described above, the HUD device 10 of the present embodiment assumes that the relative position of the occupant's viewpoint with respect to the reflecting portion 3a is slightly displaced. A specific configuration of the HUD device 10 will be described below with reference to FIGS. The HUD device 10 includes a housing 11, a display 21, an enlarged light guide unit 41, a control unit 51, and the like.

As shown in FIG. 1, the housing 11 has a hollow shape for accommodating the display unit 21, the enlarged light guide unit 41, the control unit 51, and the like, and is made of, for example, a synthetic resin or a metal. It is installed in panel 2. The housing 11 has a window portion 12 that is optically opened on an upper surface portion that faces the reflection portion 3a in the vertical direction. The window 12 is covered with, for example, a dustproof sheet 13 that can transmit display light.

The display 21 displays an image on the display screen 22a and projects the display light of the image toward the magnifying light guide unit 41. The display 21 of this embodiment is a transmissive liquid crystal display. As shown in FIGS. 2 and 3, the display device 21 includes an image display panel 22 having a display screen 22a, a backlight 24, and an illumination optical unit 30, and these are housed in a box-shaped casing having a light shielding property, for example. Is configured.

As shown in FIG. 1, the enlarged light guide section 41 forms an optical path for guiding the display light of the image emitted from the display screen 22 a of the display 21. The enlarged light guide unit 41 has, for example, a plane mirror 42 and a concave mirror 44.

The plane mirror 42 has a reflecting surface formed by evaporating aluminum on the surface of a base material made of, for example, synthetic resin or glass. The reflecting surface of the plane mirror 42 is formed into a smooth flat surface. The display light that has entered the plane mirror 42 from the display 21 is reflected by the reflecting surface toward the concave mirror 44.

The concave mirror 44 forms a reflecting surface by, for example, vapor-depositing aluminum on the surface of a base material made of synthetic resin or glass. The reflecting surface of the concave mirror 44 is formed in a smooth concave shape by being curved in a concave shape. The display light that has entered the concave mirror 44 from the plane mirror 42 is reflected by the reflecting surface toward the reflecting portion 3a. Here, the display virtual image VDP can be enlarged with respect to the image on the display screen 22a by reflection on the reflection surface of the concave mirror 44 having positive optical power.

The display light thus reflected by the concave mirror 44 is emitted to the outside of the HUD device 10 by passing through the dustproof sheet 13, and enters the reflection portion 3 a of the windshield 3. When the display light reflected by the reflector 3a reaches the occupant's viewpoint, the occupant can visually recognize the display virtual image VDP. Here, since the reflecting portion 3a is set on the windshield 3 as a transmissive member, the display virtual image VDP is displayed so as to be superimposed on the scenery outside the vehicle visually recognized through the windshield 3.

The concave mirror 44 is rotatable about a rotary shaft 44a extending in the left-right direction according to the driving of a stepping motor controlled by the control unit 51. By such rotation, the display position of the display virtual image VDP can be adjusted so as to be displaced in the vertical direction.

Below, the display 21 of this embodiment and its control are demonstrated in detail. As shown in FIG. 2, the image display panel 22 of the display 21 is a TFT liquid crystal panel using a thin film transistor (TFT), and includes, for example, a plurality of liquid crystal pixels 23 arranged in a two-dimensional array. It is an active matrix type liquid crystal panel formed.

The image display panel 22 has a rectangular shape having a longitudinal direction LD and a lateral direction SD. Since the liquid crystal pixels 23 are linearly arranged in the longitudinal direction LD and the lateral direction SD, the display screen 22a that faces the enlargement light guide portion 41 and emits an image as display light also has a rectangular shape. The longitudinal direction LD of the display screen 22a corresponds to the horizontal direction of the display virtual image VDP, and the lateral direction SD of the display screen 22a corresponds to the vertical direction of the display virtual image VDP. Each liquid crystal pixel 23 is provided with a transmissive portion that is provided so as to penetrate in the normal direction of the display screen 22a, and a wiring portion that is formed so as to surround the transmissive portion.

The image display panel 22 has a flat plate shape by being formed by laminating a pair of polarizing plates and a liquid crystal layer sandwiched between the pair of polarizing plates. Each polarizing plate has a transmission axis and an absorption axis that are substantially orthogonal to each other, and has a property of transmitting light polarized in the transmission axis direction and absorbing light polarized in the absorption axis direction. The pair of polarizing plates are arranged with their transmission axes orthogonal to each other. By applying a voltage to each liquid crystal pixel, the liquid crystal layer can rotate the polarization direction of light incident on the liquid crystal layer according to the applied voltage. In this way, the image display panel 22 can change the ratio of the light transmitted through the polarizing plate on the side of the magnifying light guide 41, that is, the transmittance for each liquid crystal pixel 23 (more strictly, for each sub pixel) by the rotation of the polarization direction. it can.

Therefore, in the image display panel 22, the transmittance of each liquid crystal pixel 23 is controlled according to the incidence of the light source light from the illumination target surface 22b, which is the surface on the side of the backlight 24, so that the image is displayed on the display screen 22a. Is displayed. A plurality of sub-pixels forming one liquid crystal pixel 23 are provided with color filters of different colors (for example, red, green and blue), and various colors are realized by combining these. There is.

The backlight 24 is used to illuminate the illumination target surface 22b of the image display panel 22. The backlight 24 is a so-called direct-type or direct-type backlight, and includes a plurality of illumination segments 25, a substrate 24 a that holds the illumination segments 25, and the like.

In this embodiment, each lighting segment 25 employs one light emitting diode element. Each lighting segment 25 is electrically connected to a power supply through a wiring pattern formed by a lighting circuit on the board 24a. More specifically, each of the illumination segments 25 is formed by sealing a chip-shaped blue light emitting diode with a yellow phosphor in which a yellow fluorescent agent is mixed with a translucent synthetic resin. The blue light emitted from the blue light emitting diode according to the amount of electric current excites the yellow phosphor to emit yellow light, and by mixing the blue light and the yellow light, pseudo white light source light is emitted from each illumination segment 25. Is emitted. Each lighting segment 25 can be individually switched between a lighting state and a non-lighting state.

In the present embodiment, a plurality of illumination segments 25 are arranged along the surface of the substrate 24a, so that a light source surface 26 in the form of a surface light source is formed by the set of illumination segments 25. Each illumination segment 25 is arranged so as to divide the planar light source surface 26. More specifically, since the illumination segments 25 are arranged in a two-dimensional direction so as to form a rectangular lattice, the area occupied by each illumination segment 25 is defined in a rectangular shape.

The image display panel 22 is arranged to be inclined with respect to the light source surface 26. Thereby, when the light source light is emitted from each illumination segment 25 with the direction substantially perpendicular to the light source surface 26 as the intensity peak direction, the light source light that contributes to the display is obliquely transmitted through the image display panel 22.

In addition, each illumination segment 25 is configured to mainly illuminate a corresponding partial area of the illumination target surface 22b of the image display panel 22 or the display screen 22a. In other words, the display screen 22a is set with the divided areas DA virtually divided corresponding to the arrangement of the illumination segments 25. In the present embodiment, when the light source surface 26 and the image display panel 22 are viewed along the intensity peak direction, the illumination segment 25 and the divided area DA, which are in the individual correspondence relationship, have a positional relationship in which they overlap with each other. In the present embodiment, the “superposed state” and “non-superposed state” are based on the case where the light source surface 26 and the image display panel 22 are viewed along the intensity peak direction.

The illumination optical unit 30 is arranged between the light source surface 26 of the backlight 24 and the image display panel 22. The illumination optical unit 30 adjusts the directivity of the light source while maintaining the individual correspondence relationship between the illumination segment 25 and the divided area DA. The illumination optical unit 30 has, for example, a lens array 31, a Fresnel lens 32, and a diffusion plate 33.

The lens array 31 is formed by arranging a plurality of convex lens elements 31 a according to the number and arrangement of the illumination segments 25. In particular, each convex lens element 31a of the present embodiment has a rectangular outer peripheral contour and is arranged so as to face the corresponding illumination segment 25 individually. Each convex lens element 31a is formed of, for example, synthetic resin or glass so as to have a light-transmitting property, and collects the light source light from the corresponding illumination segment 25.

The Fresnel lens 32 is made of, for example, synthetic resin or glass and has a light-transmitting property and is formed in a flat plate shape. The Fresnel lens 32 further condenses and collimates the light source light incident from the lens array 31 side.

The diffusion plate 33 is arranged in a state of being close to or in an adhesive state with respect to the illumination target surface 22b of the image display panel 22, and for example, by mixing diffusing particles such as microbeads with a base material made of translucent synthetic resin, a sheet It is formed in a shape. The diffusion plate 33 diffuses the light incident from the Fresnel lens 32 side and further adjusts the directivity of the light source light incident on the image display panel 22.

The control unit 51 shown in FIGS. 1 and 3 is a so-called computer, and is mainly composed of an electronic circuit including at least one processor, a memory device, and an input/output interface. The processor is an arithmetic circuit that executes a computer program stored in the memory device. The memory device is a non-transitional tangible recording medium that is provided by, for example, a semiconductor memory or the like, and non-temporarily stores a computer program readable by a processor.

The control unit 51 is communicatively connected to the display 21 and the stepping motor of the concave mirror 44. In addition, the control unit 51 is configured to be able to acquire various information from an ECU (Electric Control Unit) of the vehicle 1 or the like by inputting an electric signal using communication. For communication between the control unit 51 and each element, various suitable communication methods may be adopted regardless of wired communication or wireless communication.

The control unit 51 includes control units such as the image control unit 52 and the backlight control unit 54 as functional units that perform arithmetic processing by executing computer programs.

The image control unit 52 controls the image display panel 22 so that the image generated by the ECU and input from the ECU is displayed on the display screen 22a. Alternatively, the image control unit 52 generates an image according to the information from the ECU and controls the image display panel 22 so that the image is displayed on the display screen 22a.

The image displayed on the display screen 22a is laid out on the assumption that it is formed as the display virtual image VDP that is superimposed on the scenery outside the vehicle. Specifically, only a part of the display screen 22a is set as the image display portion P1. A character or a pattern is displayed as an image on the display portion P1, the transmittance of the pixel 23 is set to a predetermined value, and the display light is emitted on the display portion P1. A background portion P2 in which substantially nothing is displayed is set in other portions except the display portion P1. In the background portion P2, the image display panel 22 is controlled so that the transmittance of the pixel 23 is set to the minimum value and the display light is not emitted from the display screen 22a as much as possible.

As shown in FIG. 4, the backlight control unit 54 performs local dimming control (also referred to as partial drive control) on the backlight 24 in cooperation with the image control unit 52. Specifically, the backlight control unit 54 individually switches between the lighting state and the extinguishing state of each lighting segment 25. Of the plurality of illumination segments 25, only the illumination segment 25 related to the visual recognition of the display portion P1 described above is in the lighting state, and the other illumination segments 25 are in the non-lighting state.

In FIG. 4, on the light source surface 26 side, the illuminated illumination segments 25 are shown without hatching, and the illuminated illumination segments 25 are shown with dot hatching. Further, on the display screen 22a side, the display portion P1 is shown without hatching, the divided area DA overlapping the lighting segment 25 in the lighting state is shown with thin dot hatching, and overlapping with the lighting segment 25 in the unlit state. The divided area DA to be shaded is shown with thick dot hatching. On the display screen 22a side, the liquid crystal pixels 23 are shown by being divided by thin lines. In addition, in FIG. 4, the reference numerals of the illumination segment 25 and the like are not attached to all (the same applies to FIGS. 5 and 7).

Switching on and off of each illumination segment 25 is determined by the backlight control unit 54 based on the arrangement of the display portion P1 on the display screen 22a.

In the conventional local dimming control, if the display portion is set in the divided area individually corresponding to the specific illumination segment, the specific illumination segment is turned on, and if the display portion is not set, the specific illumination segment is set. The lighting segment is turned off. Therefore, only the illumination segment overlapping the display portion (in other words, directly below the display portion) is set to the lighting state.

However, in the local dimming control of the present embodiment, the extension determination area EJA (see the broken line in FIG. 5) obtained by extending each divided area DA is used for the determination. Specifically, if the display portion P1 is set in the expansion determination area EJA in which the divided area DA individually corresponding to the specific illumination segment 25 is set, the specific illumination segment 25 is turned on, and the display portion P1. Is not set, the specific illumination segment 25 is turned off.

As a result, the illumination segment 25a that is in the overlapping state with the display portion P1 (in other words, immediately below the display portion P1) is set to the lighting state, and the entire occupied area is not in the overlapping state with the display portion P1 (in other words, in other words). The illumination segment 25 that is not directly below the display portion P1 or immediately below the background portion P2) and that is around the illumination segment 25a may also be set to the lighting state. More specifically, the display portion P1 is an illumination segment in which the entire occupied area is in a non-overlapping state, and is predetermined in the expansion direction from an area (in other words, an area immediately below the display portion P1) overlapping the display portion P1 on the light source surface 26. The illumination segment 25b located within the distance or less is turned on as the extended lighting area ELA (see the broken line in FIG. 4).

The predetermined distance here is a value larger than 0 and is based on the expansion width of the expansion determination area EJA with respect to the divided area DA. The larger the expansion width is set, the larger the substantial predetermined distance is. For example, the predetermined distance and the expansion width match. In the present embodiment, the expansion width in the longitudinal direction LD and the expansion width in the lateral direction SD are set respectively, and the rectangular expansion determination area EJA is set for the rectangular divided area DA, so that the predetermined distance is also set. , The longitudinal direction LD and the lateral direction SD are different.

For example, the expansion width of the expansion determination area EJA with respect to the divided area DA in the longitudinal direction LD is set to be larger than the expansion width of the expansion determination area EJA with respect to the divided area DA in the lateral direction SD. Particularly in this embodiment, the expansion width in the lateral direction SD is set to zero. In this way, if the predetermined distance is set to a value larger than 0 in the expansion direction along the tangential direction of the light source surface 26, the predetermined distance is set to 0 (in other words, the lighting area is not expanded). May be. In the present embodiment, since the expansion direction is set to the longitudinal direction LD, the illumination segment 25b that is deviated in the longitudinal direction LD from the illumination segment 25a that overlaps the display portion P1 is also turned on.

In this way, the respective extended determination areas EJA used for determination have overlapping portions with each other. When the display portion P1 is set in this overlapping portion, the plurality of illumination segments 25 corresponding to the respective expansion determination areas EJA forming the overlapping portion are turned on.

Now, as shown in FIG. 1, in the optical system that displays the display virtual image VDP by the HUD device 10, the backlight 24 is located on the opposite side of the visible region EB with the windshield 3 in between, and more specifically, as compared with the display virtual image VDP. A virtual image of the light source surface 26 (hereinafter, light source surface virtual image VLS) is formed behind the display virtual image VDP that is distant. The light source surface virtual image VLS can be recognized by the occupant through the display virtual image VDP, for example, in the form of a luminance distribution of the display virtual image VDP. The display virtual image VDP and the light source surface virtual image VLS are separated from each other based on the configuration of the backlight 24, the enlargement magnification of the enlargement light guide portion 41, and the like.

Here, as shown in FIG. 6, an imaginary line Lv passing through the display virtual image VDP and the assumed viewpoint position PE assumed as the viewpoint of the occupant who visually recognizes the display virtual image VDP is defined. Then, when the display virtual image VDP is seen from the assumed viewpoint position PE, the occupant visually recognizes the light source surface virtual image VLS along the virtual line Lv. Therefore, the intersection position where the virtual line Lv intersects the light source surface virtual image VLS The brightness of the illumination segment 25 corresponding to the PC will be recognized as the brightness of the display virtual image VDP.

Then, since the display virtual image VDP and the light source surface virtual image VLS are separated from each other as described above, the virtual line Lv does not penetrate the virtual image of the display screen 22a in the normal direction but obliquely from the assumed viewpoint position PE. In this case, the intersection position PC may be located in the illumination segment 25 that is not superposed on the display virtual image VDP. In the present embodiment, the local dimming control is performed such that the illumination segment 25 at the intersection position PC is in the lighting state, that is, the intersection position PC is included in the extended lighting area ELA.

More specifically, in the present embodiment, the assumed viewpoint position PE is defined in the entire rectangular visual recognition area EB that is long in the left and right directions. That is, a plurality of virtual lines Lv are defined corresponding to each location in the visual recognition area EB (for example, each location set in a virtual lattice shape at predetermined intervals in the visual recognition area EB). In this way, the illumination segment 25 at the intersection position PC corresponding to each of the virtual lines Lv defined in plural is in the lighting state.

Therefore, for example, when the viewpoint of the occupant is shifted from the front to the right (see FIG. 7 ), it can be recognized that the lighting segment 25 in the lighting state is displaced to the right with respect to the display portion P1. The extended lighting area ELA remains on the extension of the line of sight from the viewpoint to the display portion P1.

Hereinafter, the processing by the HUD device 10 of the first embodiment, particularly the processing by the backlight control unit 54 will be described with reference to the flowchart of FIG. The flowchart of FIG. 8 is executed, for example, every time an image is rewritten, and is repeatedly executed during the operation of the HUD device 10.

First, in step S111, the backlight control unit 54 determines whether or not the brightness of the image displayed on the display screen 22a exceeds the illumination threshold of the backlight 24. This illumination threshold is set to prevent erroneous lighting due to noise when the image data is compressed. Pixels 23 having a luminance equal to or lower than the illumination threshold are regarded as the background portion P2 (including a portion where noise has occurred). Pixels 23 having a brightness exceeding the illumination threshold are regarded as the display portion P1. After the process of step S111, the process proceeds to step S112.

In step S112, the backlight control unit 54 determines whether or not the display portion P1 of the image is set in the extended determination area EJA for each illumination segment 25. The illumination segment 25 in which the image display portion P1 is set in the expansion determination area EJA is an illumination segment to be turned on. On the other hand, the illumination segment 25 in which the image display portion P1 is not set in the expansion determination area EJA is an illumination segment that is not required to be turned on. After the process of step S112, the process proceeds to step S113.

In step S113, the backlight control unit 54 turns on the illumination segment 25 to be turned on. With the above, a series of processing is completed. In this way, local dimming control suitable for visual recognition of the display virtual image VDP is realized.

(Action effect)
The effects of the first embodiment described above will be described below.

According to the first embodiment, in the backlight 24, among the plurality of illumination segments 25 arranged so as to divide the light source surface 26, the virtual line Lv intersects with the light source surface virtual image VLS formed behind the display virtual image VDP. The lighting segment 25 corresponding to the intersecting position PC is turned on. The virtual line Lv is defined as a line that passes through the display virtual image VDP and the assumed viewpoint position PE that is assumed as the viewpoint of the viewer who visually recognizes the display virtual image VDP. That is, the virtual image of the illuminated illumination segment 25 exists on the extension line of the line of sight from the assumed viewpoint position PE to the display virtual image VDP. Therefore, when the viewer looks at the display virtual image VDP from the assumed viewpoint PE, the display virtual image VDP is visually recognized as if it is illuminated by the backlight 24. Therefore, even if the backlight 24 is subjected to the local dimming control, the reduction in the brightness of the display virtual image VDP visually recognized from the viewpoint of the viewer is suppressed, so that the visibility of the display virtual image VDP becomes good.

Further, according to the first embodiment, a plurality of virtual lines Lv are defined corresponding to each position of the visual recognition area EB, with the entire visual recognition area EB in which the display virtual image VDP can be visually recognized as the assumed viewpoint position PE. Then, each illumination segment 25 corresponding to the intersection position PC where each virtual line Lv intersects in the virtual light source surface image VLS is turned on. Therefore, in the state in which the viewpoint of the viewer is in the visible region EB and the display virtual image VDP is visible, the virtual image of the illuminated illumination segment 25 exists on the extension of the line of sight from the viewpoint to the display virtual image VDP. It will be. Therefore, since the reduction in the brightness of the display virtual image VDP visually recognized from the visual recognition area EB is suppressed, the visibility of the display virtual image VDP becomes good.

Further, according to the first embodiment, in the backlight 24, among the plurality of illumination segments 25 arranged so as to divide the light source surface 26, the illumination segment 25a immediately below the image display portion P1 is turned on. In addition, the illumination segment 25b of the extended lighting area ELA is turned on. The illumination segment 25b of the extended lighting area ELA is an illumination segment whose entire occupied area is not directly below the display portion P1, and is located within a predetermined distance or less in the extension direction from the area directly below the display portion P1 on the light source surface 26. Lighting segment. Therefore, when the viewer's viewpoint is shifted from the front in the expansion direction and the display virtual image VDP is viewed obliquely, it is probable that the virtual image of the illuminated illumination segment 25 exists on the extension line of the line of sight from the viewpoint to the display virtual image VDP. Can be increased. Therefore, even if the backlight 24 is subjected to the local dimming control, the display virtual image VDP is visually recognized as being illuminated by the backlight 24, so that the brightness of the display virtual image VDP visually recognized from the viewpoint of the viewer is reduced. Since the display virtual image VDP is suppressed, the visibility of the display virtual image VDP becomes good.

Further, according to the first embodiment, the extension width of the extension lighting area ELA is larger in the left-right direction than in the up-down direction. With this configuration, even if the viewer views the display virtual image VDP with the left and right eyes arranged side by side, the brightness of both the display virtual image VDP viewed from the right eye and the display virtual image VDP viewed from the left eye is reduced. Since it is suppressed, it is possible to reduce a feeling of strangeness when visually recognizing the display virtual image VDP.

(Second embodiment)
As shown in FIGS. 9 to 11, the second embodiment is a modification of the first embodiment. The second embodiment will be described focusing on the points different from the first embodiment.

The backlight control unit 54 of the second embodiment constitutes a virtual image display system together with the driver status monitor (hereinafter referred to as DSM) 4. The control unit 51 can communicate with the DSM 4, and the backlight control unit 254 cooperates with the DSM 4 to perform the local dimming control of the backlight 24.

The DSM 4 functions as an eye detection unit that detects the position of the left eye and the position of the right eye of the occupant by capturing the image of the occupant's face and analyzing the image, and more preferably, monitors the occupant's drowsiness and aside. To do. The DSM 4 is installed, for example, above the instrument panel 2 and the windshield 3 at a position where it is easy to photograph the occupant's face in the vehicle 1. The DSM 4 is composed of an illumination body, a camera 4a (see FIG. 10), an image analysis unit, and the like.

The illuminating body illuminates the occupant's face with illumination light. Since it is preferable that the occupant cannot sense the illumination light, a near infrared light source that uses near infrared light as the illumination light is used for the illumination body. The camera 4a shoots the occupant's face as a shooting target. The camera 4a has an image sensor and a lens unit for forming an image of a subject on the image sensor. As the image pickup element, for example, an element such as a CMOS sensor which has a good sensitivity to near infrared light and has a high resolution of an image to be detected is employed.

The image analysis unit is a control unit realized by an electronic circuit such as a so-called computer or FPGA (Field-Programmable Gate Array). The image analysis unit analyzes image data from the image sensor. The position of the left eye and the position of the right eye of the occupant obtained by the analysis are sequentially output to the control unit 51 of the HUD device 10.

In the second embodiment, the formula f(E(px, py, pz), A(ix, iy)) is stored in advance in the memory device of the control unit 51. In Expression f, E(px, py, pz) represents the viewpoint position on the visual recognition area EB. A(ix, iy) represents the image coordinates of the display portion P1 on the display virtual image VDP. Then, the mathematical expression f is an expression representing an intersection position PC between the virtual line Lv passing through the viewpoint position E (px, py, pz) and the image coordinate A (ix, iy) and the light source surface virtual image VLS. The x direction corresponds to the left-right direction of the vehicle 1, the y direction corresponds to the up-down direction of the vehicle 1, and the z direction corresponds to the front-back direction of the vehicle 1.

Formula f stored in advance may be calculated by an experiment in an actual machine or may be calculated by an optical simulation. Since the distance between the display virtual image VDP and the light source surface virtual image VLS becomes large due to the influence of the enlargement in the enlargement light guide portion 41, this influence is naturally incorporated in the mathematical expression f.

The backlight control unit 54 of the second embodiment acquires the position of the left eye and the position of the right eye input from the DSM 4, and the image coordinates A(ix, iy) of the display portion P1 that is currently displayed. The backlight control unit 54 obtains the intersection position PC of the virtual line Lv and the virtual image of the light source surface VLS by substituting the obtained values into the mathematical expression f, and turns on the backlight based on the intersection position PC. The write position L(lx, ly) is determined. In other words, the backlight controller 54 solves the following equation.
f(E(px, py, pz), A(ix, iy))----= L(lx, ly)

That is, the imaginary line Lv is defined with the position of the left eye and the position of the right eye of the occupant detected by the DSM 4 as the assumed viewpoint position PE. In the present embodiment, the position of the left eye is substituted into the mathematical expression f to obtain the intersection position PC, and the position of the right eye is substituted into the mathematical formula to obtain the intersection position PC, and the illumination segment 25 corresponding to each intersection position PC is obtained. The lighting state is set.

Further, in the present embodiment, the image coordinates A(ix, iy) of the display portion P1 that is substituted into the mathematical expression f is often the display portion P1 having a plurality of pixels 23 and having an area. By substituting the coordinates of each pixel 23 into the mathematical expression f, the intersection position PC of each pixel 23 is obtained, and the illumination segment 25 corresponding to the intersection position PC of each pixel 23 is set to the lighting state.

That is, in the present embodiment, the formula f is calculated by the product of the total number of eyes and the total number of pixels 23 of the display portion P1. The calculation can be simplified as in Modifications 4 to 6 described later.

Hereinafter, processing by the HUD device 210 of the second embodiment, particularly processing by the backlight control unit 254 will be described with reference to the flowchart of FIG. The process according to the flowchart of FIG. 11 is performed, for example, every predetermined time and is repeatedly performed during the operation of the HUD device 10.

First, in step S211, the backlight control unit 254 acquires the viewpoint position E (px, py, pz) detected by the DSM 4. After the process of step S211, the process proceeds to step S212.

In step S212, as in step S111 of the first embodiment, the backlight control unit 254 determines whether or not the brightness of the image displayed on the display screen 22a exceeds the illumination threshold of the backlight 24. After the process of step S212, the process proceeds to step S213.

In step S213, the backlight control unit 254 calculates the backlight position L(lx, ly) using the mathematical expression f for the image coordinates A(ix, iy) of the lighting state of the display screen 22a. After the process of step S213, the process proceeds to step S214.

In step S113, the backlight control unit 254 turns on the illumination segment 25 corresponding to the backlight position L(lx, ly) to be turned on. With the above, a series of processing is completed. In this way, local dimming control suitable for visual recognition of the display virtual image VDP is realized.

According to the second embodiment described above, the virtual line Lv is defined with the eye position detected by the DSM 4 for detecting the eye position of the viewer as the assumed viewpoint position PE. By narrowing down the assumed viewpoint position PE using the DSM 4 to a narrow area, it is possible to set a larger number of illumination segments 25 in the off state while suppressing a decrease in the brightness of the display virtual image VDP. Therefore, more efficient local dimming control can be realized.

(Other embodiments)
Although a plurality of embodiments have been described above, the present disclosure should not be construed as being limited to those embodiments, and may be applied to various embodiments and combinations without departing from the scope of the present disclosure. You can

Specifically, as a modified example 1 of the first embodiment, the backlight is set so that the brightness of the lighting segment 25b that is turned on as the extended lighting area ELA is smaller than the brightness of the lighting segment 25a immediately below the image display portion P1. The control unit 54 controls the backlight 24. In this way, it is likely that the front view is more likely to be selected as the visual aspect of the display virtual image VDP than the oblique view while suppressing the decrease in brightness when the display virtual image VDP is viewed from the diagonal. In view of this, it is possible to increase the energy efficiency in the extended lighting area ELA.

As a modified example 2 of the first embodiment, the extension direction of the extension lighting area ELA may be both the left-right direction and the up-down direction. In this case, as shown in FIGS. 12 and 13, the expansion width in the longitudinal direction LD of the expansion determination area EJA with respect to the divided area DA is set to a value larger than 0, and the expansion width in the lateral direction SD is larger than 0. Set to the value. In the example of FIG. 12, the extension width in the longitudinal direction LD and the extension width in the lateral direction SD are set to be equal. Further, in the example of FIG. 13, the expansion width in the longitudinal direction LD is set to be larger than the expansion width in the lateral direction SD.

As a modified example 3 of the first embodiment, a configuration in which the assumed viewpoint position PE is defined in the entire rectangular visual recognition area EB that is long in the left and right, and a plurality of virtual lines Lv are defined corresponding to the respective locations in the visual recognition area EB. In place of the determination by the extended determination area EJA, the illumination segment 25 in the lighting state may be determined by using the mathematical expression f as in the second embodiment. For example, a plurality of viewpoint positions E (px, py, pz) set in a virtual grid pattern at predetermined intervals in the visual recognition area EB are respectively substituted into the mathematical expression f, and each viewpoint position E (px, py, pz) is calculated. All the illumination segments 25 corresponding to the calculated backlight position L(lx, ly) are turned on.

As a modified example 4 of the second embodiment, it is not necessary to calculate each of the virtual line Lv corresponding to the left eye and the virtual line Lv corresponding to the right eye. The average value of the positions of the left eye and the position of the right eye detected by the DSM 4 may be substituted into the expression f as the viewpoint position E(px, py, pz).

As a modified example 5 of the second embodiment, a fixed value determined by design in the visual recognition area EB is adopted for pz of the viewpoint position E (px, py, pz) instead of the value acquired from the DSM 4. Good. As a result, the amount of calculation can be reduced.

As a modified example 6 of the second embodiment, the virtual line Lv corresponding to the coordinates of each pixel 23 of the display portion P1 does not have to be calculated for the image coordinates A(ix, iy). For example, only the virtual line Lv corresponding to the coordinates of the pixel 23 corresponding to the contour of the display portion P1 is calculated, and the illumination segment 25 inside the set of intersection positions PC is turned on. can do. Further, for example, only the virtual line Lv corresponding to the pixel 23 corresponding to the center coordinates of the display portion P1 may be calculated, and the illumination segment 25 to be turned on may be estimated from the shape of the display portion P1.

As a modified example 7 of the second embodiment, the position of the left eye and the position of the right eye of the occupant may be detected using a distance sensor instead of the camera 4a of the DSM4.

As a modified example 8, the magnifying light guide unit 41 may employ a configuration in which various optical elements such as a concave mirror, a plane mirror, a convex mirror, a convex lens and a concave lens are combined. Further, the enlarged light guide section 41 itself may not be provided.

As a ninth modification, various configurations can be adopted for the illumination optical unit 30 without departing from the backlight configuration according to the direct type. Further, the illumination optical section 30 itself may not be provided.

As a tenth modification, one illumination segment 25 may be composed of a plurality of light emitting diode elements.

As a modified example 11, an independent light source may not be arranged for each illumination segment 25. For example, even if one surface light source using an OLED (Organic Light-Emitting Diode) is controllably divided to form a plurality of illumination segments 25, and these can be individually switched between a lighting state and a non-lighting state. Good.

As a modified example 12, at least a part of the processing by the control unit 51 may be realized by hardware by a classical analog circuit, FPGA (Field-Programmable Gate Array) or the like, and artificial processing using a neural network may be used. It may be realized by an intelligent algorithm.

As a thirteenth modification, the virtual image display device can be applied to various vehicles such as an aircraft, a ship, and a case that does not move (for example, a game case).

The control unit and the method thereof described in the present disclosure may be realized by a dedicated computer that configures a processor programmed to execute one or more functions embodied by a computer program. Alternatively, the apparatus and method described in the present disclosure may be realized by a dedicated hardware logic circuit. Alternatively, the device and the method described in the present disclosure may be realized by one or more dedicated computers configured by a combination of a processor that executes a computer program and one or more hardware logic circuits. Further, the computer program may be stored in a computer-readable non-transition tangible recording medium as an instruction executed by the computer.

3a: Reflector, 22: Image display panel, 22a: Display screen, 24: Backlight, 25, 25a, 25b: Illumination segment, 26 Light source surface, 54, 254: Backlight controller, ELA: Extended lighting area, Lv : Virtual line, P1: Display part, PC: Crossing position, PE: Viewpoint assumed position, VDP: Display virtual image, VLS: Light source surface virtual image

Claims (6)

A virtual image display device for displaying a display virtual image (VDP) by reflecting display light of an image on a reflecting section (3a),
An image display panel (22) having a display screen (22a) for displaying the image;
A backlight (24) having a plurality of illumination segments (25) arranged to divide the light source surface (26) and illuminating the image display panel from the light source surface;
A backlight control unit (54, 254) for individually switching the lighting state and the extinguishing state of each of the lighting segments to perform local dimming control of the backlight,
A light source surface virtual image (VLS) of the light source surface is formed behind the display virtual image,
When a virtual line (Lv) passing through the display virtual image and a viewpoint assumed position (PE) assumed as a viewpoint of a viewer who visually recognizes the display virtual image is defined,
The said backlight control part is a virtual image display apparatus which makes the said illumination segment corresponding to the intersection position (PC) which the said virtual line cross|intersects in the virtual image of the said light source surface the lighting state. A plurality of virtual lines are defined corresponding to each position in the visual recognition area, with the entire visual recognition area (EB) in which the display virtual image is visually recognizable as the viewpoint assumed position,
The virtual image display device according to claim 1, wherein the backlight control unit sets each of the illumination segments corresponding to the intersecting position where each of the virtual lines intersects in the virtual image of the light source surface to a lighting state. The virtual image display device according to claim 1, wherein the virtual line is defined with the eye position detected by an eye detection unit (4) that detects the eye position of the viewer as the assumed viewpoint position. A virtual image display device for displaying a display virtual image (VDP) by reflecting display light of an image on a reflecting portion (3a),
An image display panel (22) having a display screen (22a) for displaying the image;
A backlight (24) having a plurality of illumination segments (25) arranged so as to divide the light source surface (26), and illuminating the image display panel with the light source surface;
A backlight control unit (54) for individually switching the lighting state and the extinguishing state of each of the lighting segments to perform local dimming control of the backlight,
In addition to turning on the illumination segment (25a) immediately below the display portion (P1) of the image, the backlight control unit may make the entire occupied area be the illumination segment not directly below the display portion. A virtual image display device in which the illumination segment (25b) located within a range of a predetermined distance or less in the expansion direction from the region immediately below the display portion on the light source surface is turned on as an extended lighting region (EJA). The virtual image display device according to claim 4, wherein the extension width of the extension lighting region is larger in the left-right direction than in the up-down direction. The virtual image display device according to claim 4, wherein the brightness of the lighting segment of the extended lighting region in the lighting state is smaller than the brightness of the lighting segment immediately below the display portion.

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