JP7764831B2 - Virtual image display device - Google Patents

Description

This specification discloses technology for displaying virtual images.

Display devices that display virtual images are known. The display device described in Patent Document 1 is configured so that a reflective panel is provided in the optical system, allowing some of the external light that enters the device to pass through the reflective panel.

Japanese Patent Application Laid-Open No. 2022-71763

The technology in Patent Document 1 reduces the amount of external light, such as sunlight, that enters the polarizing plate of a display panel. However, because some of the external light still enters the polarizing plate, the polarizing plate deteriorates more rapidly than when the product was shipped. Therefore, there is concern that the display quality of virtual images will deteriorate due to the deterioration of the polarizing plate.

One of the purposes of the disclosure of this specification is to provide a virtual image display device that suppresses degradation of display quality.

One aspect disclosed herein is a virtual image display device that displays a virtual image (VRI) by reflecting display light of an image on a reflective member (3),
a polarizing plate (43) that transmits a specific polarized light of the display light;
an image display control unit (61) that controls the display state of the image;
The image display control unit
a deterioration state determination unit (62) for determining the deterioration state of the polarizing plate;
a correction unit (63) that corrects the display state according to the deterioration state ,
The polarizing plate is placed in a position where it is expected to be irradiated with sunlight,
The device further includes a timer (53) that counts time and stops counting the time at the time when it is estimated that the incidence of sunlight on the polarizing plate will be blocked,
The deterioration state determining unit determines the deterioration state due to sunlight irradiation by referring to the timer .
One of the disclosed aspects is a virtual image display device that displays a virtual image (VRI) by reflecting display light of an image on a reflecting member (3),
a polarizing plate (43) that transmits a specific polarized light of the display light;
an image display control unit (61) that controls the display state of the image;
The image display control unit
a deterioration state determination unit (62) for determining the deterioration state of the polarizing plate;
a correction unit (63) that corrects the display state according to the deterioration state,
The polarizing plate is placed in a position where it is expected to be irradiated with sunlight,
The deterioration state assessment unit assesses the deterioration state due to sunlight exposure by estimating the cumulative amount of sunlight exposure to the polarizing plate from information regarding the hours of sunlight and information for identifying the positional relationship between the polarizing plate and the sun.

In this embodiment, the display state of the image is corrected according to the deterioration state of the polarizing plate. Therefore, even if the polarizing plate deteriorates, the correction can suppress deterioration in the display quality of the virtual image displayed by the display light transmitted through the polarizing plate.

Note that the reference symbols in parentheses in the claims and other sections are intended to exemplify the correspondence with the embodiments described below and are not intended to limit the technical scope.

FIG. 2 is a diagram showing a state in which the HUD is mounted on a vehicle. FIG. 1 is a diagram showing a schematic configuration of a HUD or the like. FIG. IV-IV line cross section of FIG. 3. FIG. 2 is a diagram showing the functional configuration of a control unit. 10 is a graph conceptually showing a γ table. Chromaticity diagram showing the change in the color reproduction range due to deterioration of the polarizing plate. 10 is a flowchart showing an example of a correction process performed by a control unit. FIG. 1 is a diagram showing a schematic configuration of a HUD or the like. 10A and 10B are diagrams for explaining virtual division of a polarizing plate or a screen.

Below, several embodiments will be described based on the drawings. Note that corresponding components in each embodiment will be given the same reference numerals, and duplicate explanations may be omitted. When only a portion of the configuration is described in each embodiment, the configuration of another previously described embodiment can be applied to the remaining portions of that configuration. Furthermore, in addition to the combinations of configurations explicitly stated in the description of each embodiment, configurations of several embodiments can also be partially combined together even if not explicitly stated, as long as there are no particular problems with the combination.

(First embodiment)
As shown in FIG. 1 , the virtual image display device according to the first embodiment of the present disclosure is a head-up display (hereinafter referred to as HUD) 10. The HUD 10 is configured to be mounted on a vehicle 1. Here, the term vehicle 1 is broadly interpreted to include various vehicles such as automobiles, railroad cars, aircraft, ships, and stationary game cabinets. In particular, the vehicle 1 in this embodiment is a four-wheeled automobile. In the following description, the directions of front, rear, up, down, left, and right are expressed based on the vehicle 1 on a horizontal plane HP.

The HUD 10 is mounted on the instrument panel 2 of the vehicle 1. The HUD 10 projects display light toward the front windshield (hereinafter referred to as FWS) 3 of the vehicle 1. As a result, the HUD 10 displays an image as a virtual image VRI that can be viewed by an occupant (e.g., the driver) of the vehicle 1. In other words, the display light reflected by the FWS 3 reaches a viewing area EB set within the interior of the vehicle 1, allowing an occupant with their eye point EP positioned in the viewing area EB to view various information.

The FWS 3 is formed into a translucent plate made of, for example, glass or synthetic resin, and is positioned above the instrument panel 2. The FWS 3 is tilted so that it moves away from the instrument panel 2 as it moves from the front to the rear. The reflective surface of the FWS 3 onto which the image display light from the HUD 10 is projected is formed into a smooth concave or flat shape. Therefore, the FWS 3 functions as a reflective member that reflects the display light. Through the FWS 3, the occupant can view the outside world, superimposed on the virtual image VRI. The FWS 3 has the property of transmitting external light such as sunlight, but may be configured to block external light other than visible light. For example, the FWS 3 may have a UV-blocking function.

The display light does not have to be projected onto the FWS 3. For example, a translucent, plate-shaped combiner may be installed inside the vehicle 1, separate from the FWS 3, and the display light may be projected onto the combiner. In this case, the combiner functions as a reflective member.

The visible area EB is a spatial region that becomes visible to the occupants of the vehicle 1 when the virtual image VRI displayed by the HUD 10 meets a predetermined standard (for example, the entire virtual image VRI has a predetermined brightness or higher), and is also called the eye box. The visible area EB is typically set to overlap with the iris set in the vehicle 1. The iris is set in the shape of a virtual ellipsoid based on the eye range, which statistically represents the spatial distribution of the occupants' eye points EP within the interior of the vehicle 1.

As shown in Figures 1 and 2, the HUD 10 includes a housing 11, an optical system 20, an optical path changing mechanism 30, a display 40, and a control unit 50.

The housing 11 is installed within the instrument panel 2. The housing 11 is a hollow box that houses the other elements of the HUD 10. The housing 11 has a window 11a at its upper part, facing the FWS 3. The window 11a may be physically open, or may be covered with a dustproof sheet that allows display light to pass through.

The optical system 20 guides the display light emitted from the display 40 to the FWS3. The optical system 20 may be a magnifying optical system that magnifies the virtual image VRI relative to the image on the display 40. The optical system 20 forms an optical path for the display light from the display 40 through the FWS3 to the viewing area EB. The optical system 20 includes mirrors such as a first mirror and a second mirror. The first mirror is formed into a rectangular plate shape from, for example, synthetic resin or glass. The first mirror and the second mirror have reflective surfaces formed by, for example, depositing a reflective film made of aluminum on their surfaces. The reflective surfaces may be formed into a smooth flat surface, a smooth concave surface, a smooth convex surface, or the like.

Here, of the first and second mirrors, the mirror located on the FSW side of the optical path may be able to change the orientation of its reflective surface using the optical path changing mechanism 30. The optical path changing mechanism 30 may be configured to include a motor, such as a stepping motor, that rotates the mirror.

The display 40 shown in Figure 3 is, for example, a transmissive liquid crystal display. The display 40 is formed by housing a dot-matrix TFT (Thin Film Transistor) liquid crystal panel 41 and a backlight in a casing. The display 40 displays an image on the screen 44 by transmitting illumination through the screen 44 of the liquid crystal panel 41 using the backlight, and projects display light that contributes to the display through the screen 44.

The display 40 is connected to the control unit 50 via a flexible cable 45. The flexible cable 45 also has a board mounted thereon that includes a drive circuit for driving the liquid crystal panel 41.

As shown in the cross section of Figure 4, the liquid crystal panel 41 is formed by stacking multiple functional layers. For example, the multiple functional layers are arranged in order from the backlight side: HC layer 41a, TAC layer 41b, PVA polarizer layer 41c, TAC layer 41d, glass layer 41e, glass layer 41f, viewing angle compensation layer 41g, TAC layer 41h, PVA polarizer layer 41i, TAC layer 41j, and HC layer 41k.

HC layers 41a and 41k are abbreviations for hard coat layers. HC layers 41a and 41k may be composed of, for example, HC films. A pair of HC layers 41a and 41k are provided at the outermost positions of the liquid crystal panel 41. HC layers 41a and 41k have high hardness and function to protect the liquid crystal panel 41. HC layers 41a and 41k have high light transmittance.

TAC layers 41b, 41d, 41h, and 41j are abbreviations for triacetyl cellulose layers. The TAC layers 41b, 41d, 41h, and 41j may be composed of, for example, TAC film. The TAC layers 41b, 41d, 41h, and 41j are arranged to sandwich the corresponding PVA polarizer layers 41c and 41i from both sides. The TAC layers 41b, 41d, 41h, and 41j function as the base material for the PVA polarizer layers 41c and 41i, and also protect the PVA polarizer layers 41c and 41i. The TAC layers 41b, 41d, 41h, and 41j have high light transmittance.

PVA polarizer layers 41c and 41i are abbreviations for polyvinyl alcohol polarizer layers. PVA polarizer layers 41c and 41i are composed of, for example, a PVA polarizing film. A PVA polarizing film is formed by, for example, adding iodine to polyvinyl alcohol and stretching it to form a film in which the iodine molecules are aligned. PVA polarizer layers 41c and 41i have a transmission axis and an absorption axis that are substantially perpendicular to each other, depending on the orientation of the iodine molecules. PVA polarizer layers 41c and 41i have the property of transmitting polarized light along the transmission axis and absorbing polarized light along the absorption axis.

The glass layers 41e and 41f include a highly translucent glass substrate and thin-film transistors or color filters formed on its surface. The pair of glass layers 41e and 41f sandwich the liquid crystal on both sides. The liquid crystal changes its orientation in response to the voltage applied to each pixel by the thin-film transistor. Depending on the orientation, the polarization direction of the backlight passing through the liquid crystal can be rotated.

Here, a pair of PVA polarizer layers 41c, 41i are arranged to sandwich the liquid crystal, with their transmission axes substantially perpendicular to each other. This makes it possible to control the transmittance of backlight through the liquid crystal panel 41 for each pixel in accordance with the voltage applied to each pixel.

The viewing angle compensation layer 41g may be composed of, for example, a viewing angle compensation film. The viewing angle compensation layer 41g improves the degradation of viewing angle characteristics caused by the liquid crystal or PVA polarizer layers 41c and 41i.

Here, the PVA polarizer layer 41c and the pair of TAC layers 41b and 41d sandwiching it constitute the polarizing plate 42, which transmits specific polarized light and absorbs other polarized light. The PVA polarizer layer 41i and the pair of TAC layers 41h and 41j sandwiching it constitute the polarizing plate 43. The polarizing plates 42 and 43 have the property of deteriorating in response to heat generation. For example, degraded polarizing plates 42 and 43 exhibit a decrease in transmittance and a discoloration to red.

In this embodiment, sunlight enters the interior of the HUD 10 through the FWS 3 and the window portion 11a, travels along an optical path opposite to the display light, and can reach the display 40. Therefore, of the pair of polarizing plates 42, 43 of the liquid crystal panel 41, the polarizing plate 43 located on the mirror side is positioned in a position where it is expected to be irradiated with sunlight. This polarizing plate 43 generates heat in response to sunlight irradiation, and exhibits degradation characteristics that progress with deterioration.

According to experiments conducted by the inventors, when polarizing plate 43 is irradiated with a xenon lamp simulating sunlight for 300 hours, the transmittance of polarizing plate 43 decreases by approximately 30% compared to its initial state. Furthermore, the chromaticity coordinates on the xy chromaticity diagram of the CIE 1931 color space of an image displayed using polarizing plate 43 change by approximately 0.03.

The control unit 50 is a unit that controls the virtual image display of the HUD 10. The control unit 50 may be stored inside the housing 11. The control unit 50 may also be located outside the housing 11. The control unit 50 is capable of controlling the image display on the display 40 and the light path changing mechanism 30. The control unit 50 includes a timer 53 and a computer 51.

Timer 53 is a circuit that counts time. Timer 53 may be set to 0, for example, at the time of product shipment. When installed in vehicle 1, timer 53 is preferably configured to continue counting time even when control unit 50 is in a sleep state. The sleep state here refers to a state in which no operating clock signal is supplied to processor 51b (described below), and the control unit 50 is stopped from functioning.

The timer 53 of this embodiment is also configured to stop or resume counting the time at night, when it is estimated that sunlight will be blocked from reaching the polarizing plate 43. The timer 53 is also configured to stop or resume counting the time while the vehicle 1 is parked in a garage or other location where sunlight is blocked from reaching the polarizing plate 43. Specifically, the timer 53 of this embodiment is configured to stop or resume counting the time in response to a signal from the solar radiation sensor 4. If the amount of light detected by the solar radiation sensor 4 exceeds a predetermined amount (when the amount of light is equivalent to that expected during the day), the timer continues counting the time during that period. If the amount of light detected by the solar radiation sensor 4 is equal to or less than the predetermined amount (when the amount of light is equivalent to that expected during the night), the timer stops counting the time during that period.

The solar radiation sensor 4 is mounted, for example, on the instrument panel 2 of the vehicle 1, and is positioned facing upward toward the FWS 3. The solar radiation sensor 4 includes a light-receiving element such as a photodiode and a spectral filter that blocks unnecessary light other than sunlight wavelengths from the light incident on the solar radiation sensor 4.

The computer 51 may have at least one memory 51a and one processor 51b. The memory 51a may be at least one type of non-tangible storage medium, such as semiconductor memory, magnetic media, or optical media, that non-temporarily stores programs and data readable by the processor 51b. Furthermore, the memory 51a may be a rewritable volatile storage medium, such as RAM (Random Access Memory). The processor 51b may include at least one type of core, such as a CPU (Central Processing Unit), GPU (Graphics Processing Unit), or RISC (Reduced Instruction Set Computer)-CPU. Furthermore, the control unit 50 may be configured to further include circuits such as an FPGA (Field-Programmable Gate Array) or ASIC (Application Specific Integrated Circuit).

As shown in FIG. 5, the control unit 50 includes an image display control unit 61 that controls the display state of an image as a functional block implemented by a processor 51b that executes a program. Here, the image display control unit 61 includes a deterioration state determination unit 62 and a correction unit 63.

The deterioration state assessment unit 62 assesses the deterioration state of the polarizing plate 43. While the deterioration state assessment unit 62 may directly inspect the deterioration state of the polarizing plate 43, in this embodiment, the deterioration state of the polarizing plate 43 is indirectly estimated. In this embodiment, the deterioration state assessment unit 62 references the timer 53.

Specifically, the deterioration state assessment unit 62 acquires the cumulative time counted by the timer 53. The deterioration state assessment unit 62 estimates the deterioration state of the polarizing plate 43 based on this cumulative time. Here, because the timer 53 is designed to operate in response to a signal from the solar radiation sensor 4, times such as nighttime and time when the vehicle is in a garage are excluded from the time that contributes to deterioration. Therefore, with a simple configuration and processing, the accuracy of the deterioration state assessment can be improved.

The deterioration state assessment unit 62 provides the assessment result to the correction unit 63. The assessment result here may be a numerical value representing the deterioration state. In this embodiment, the assessment result may also be the cumulative time acquired from the timer 53, in which case the deterioration state assessment unit 62 simply functions as a cumulative time acquisition unit.

The correction unit 63 corrects the display state of the image according to the result of the deterioration state determination. Specifically, the correction unit 63 corrects at least one of the brightness and display color of the image according to the deterioration state. In this embodiment, the correction unit 63 refers to the correction table 71 and corrects both the brightness and display color of the image.

When correcting the luminance tone, the correction unit 63 references a database of gamma tables, for example, as a correction table 71 non-temporarily stored in memory 51a. The database has multiple gamma tables. A gamma table is a lookup table used for gamma (gamma) correction, and is used to reduce the computational processing load required to apply gamma correction to each pixel. A gamma table stores pairs of pre-correction luminance values (e.g., referred to as gradations) and post-correction luminance values (e.g., referred to as luminance) in an array. The correspondence between the luminance values before and after correction is based on a gamma curve.

Multiple γ tables are prepared in advance based on an estimate of the change in brightness of the virtual image VRI perceived by the occupant due to the progression of deterioration of the polarizing plate 43. For example, as shown in Figure 6, tables with different γ values, such as γ = 2.1, 2.2, and 2.3, are prepared. The total number of γ tables prepared may be two or three. A large number of γ tables, such as 50 to 100, may be prepared by setting the γ value in small increments, such as 0.1.

The correction unit 63 selects one of multiple gamma tables to be used for the entire image, depending on the result of determining the deterioration state of the polarizing plate 43. This selection can be achieved by pre-setting tables that individually correspond to ranges of values indicating the deterioration state. As the transmittance of the polarizing plate 43 decreases as the polarizing plate 43 deteriorates, the correction unit 63 can be configured to select a table in which the gamma value gradually increases as the deterioration of the polarizing plate 43 progresses. In this way, one or both of the backlight and the liquid crystal panel 41 can be controlled so that the brightness increases as the transmittance of the polarizing plate 43 decreases.

When correcting the display color, the correction unit 63 corrects the display color based on the color reproduction ranges (also called color gamuts) CG0 and CG1 corresponding to the deterioration state. As shown by the triangle in Figure 7, the color reproduction range CG1 corresponding to a deterioration state where a certain degree of deterioration has progressed changes compared to the color reproduction range CG0 corresponding to the initial state. Accordingly, even if the display color is controlled to have the same gradation, the actual display color displayed as a virtual image will change as deterioration progresses.

Therefore, if the correction unit 63 determines that substantially the same color as in the initial state can be reproduced by correcting the color tone in the deteriorated state, it corrects the color tone so that the same color as in the initial state is reproduced. On the other hand, if the correction unit 63 determines that substantially the same color as in the initial state cannot be reproduced even by correcting the color tone in the deteriorated state, it corrects the color tone so that the color is reproduced as close as possible to the initial state.

When correcting the display color, the correction unit 63 may refer to a database of chromaticity correction tables, for example, as correction table 71 non-temporarily stored in memory 51a. The chromaticity correction table may store the correspondence between the deterioration state and the amount of color tone correction. In this way, the correction unit 63 generates a video signal based on the correction results and outputs the video signal to the display device 40.

Next, an example of a correction method performed by the control unit 50 will be described using the flowchart in Figure 8. The series of processes shown in steps S11 to S13 are executed by at least one processor at a predetermined execution cycle or based on a predetermined trigger.

In S11, the deterioration state determination unit 62 refers to the timer 53 to determine the deterioration state of the polarizing plate 43. After processing S11, proceed to S12.

In S12, the correction unit 63 determines whether the deterioration of the polarizing plate 43 has progressed compared to the past. If the answer is Yes, proceed to S13. If the answer is No, the correction unit 63 continues to use the past correction amount or correction table 71, and ends the series of processes.

In S13, the correction unit 63 changes the correction table 71 to be adopted depending on the deterioration state. S13 ends this series of processes.

In the first embodiment described above, the display state of the image is corrected according to the deterioration state of the polarizing plate 43. Therefore, even if the polarizing plate 43 deteriorates, the correction can suppress deterioration in the display quality of the virtual image VRI displayed by the display light transmitted through the polarizing plate 43.

Furthermore, according to the first embodiment, the brightness of the image displayed on the screen 44 is corrected. This prevents the brightness of the virtual image VRI from decreasing and visibility from deteriorating as the polarizing plate 43 deteriorates.

Furthermore, according to the first embodiment, the memory 51a serving as a storage medium is configured to store multiple γ tables, and the γ table to be used is changed depending on the state of deterioration. By using a correction method that selects a γ table, the response characteristics of the image's gradation characteristics are changed, thereby reducing the occurrence of visual discomfort when the driver views the corrected display.

Furthermore, according to the first embodiment, the display color of the image displayed on the screen 44 is corrected. This makes it possible to prevent the display color from changing from the intended color as the polarizing plate 43 deteriorates.

Furthermore, according to the first embodiment, the polarizing plate 43 is placed in a position where it is expected to be irradiated with sunlight. The state of deterioration due to sunlight irradiation is then determined. Because the deterioration of the polarizing plate 43 in the HUD 10 is closely related to sunlight irradiation, the accuracy of determining the state of deterioration of the polarizing plate 43 can be improved.

Furthermore, according to the first embodiment, a timer 53 is provided that counts time and stops counting time at the time when it is estimated that sunlight will be blocked from entering the polarizing plate 43. The state of deterioration is then determined by referring to the timer 53. Since the state of deterioration of the polarizing plate 43 is determined based on the actual time count, the accuracy of determining the state of deterioration of the polarizing plate 43 can be improved.

Second Embodiment
As shown in Fig. 9, the second embodiment is a modification of the first embodiment. The second embodiment will be described, focusing on the differences from the first embodiment.

The deterioration state assessment unit 62 in the second embodiment estimates the cumulative amount of sunlight irradiated onto the polarizing plate 43 and assesses the deterioration state of the polarizing plate 43 from the estimation result. Specifically, the deterioration state assessment unit 62 acquires various information from the locator 5 and DCM (Data Communication Module) 6, which are communicatively connected to the control unit 250.

The locator 5 generates highly accurate position information for the vehicle 1 through composite positioning that combines multiple pieces of acquired information. The locator 5 includes, for example, a GNSS (Global Navigation Satellite System) receiver 5a, an inertial sensor 5b, a high-accuracy map database (hereinafter referred to as "map DB") 5c, and a locator ECU 5d.

The GNSS receiver 5a receives positioning signals transmitted from multiple artificial satellites (positioning satellites). The inertial sensor 5b includes, for example, a gyro sensor and an acceleration sensor. The map DB 5c is primarily composed of non-volatile memory and stores map data with higher accuracy than that used in normal navigation.

The locator ECU 5d is primarily composed of a computer having at least one memory and one processor. The locator ECU 5d combines the positioning signals received by the GNSS receiver 5a, the measurement results of the inertial sensor 5b, and the vehicle 1's speed information, etc., to generate position information and direction information for the vehicle 1, and can provide this information to various devices on the vehicle 1, including the control unit 50 of the HUD 10.

DCM 6 is a communication module installed in vehicle 1. DCM 6 transmits and receives radio waves to and from base stations around vehicle 1 via wireless communication based on communication standards such as LTE (Long Term Evolution), 4G, and 5G. Installing DCM 6 makes vehicle 1 a connected car that can connect to the Internet.

The deterioration state assessment unit 62 acquires weather information through the DCM 6. The weather information may be acquired from the database of a national meteorological agency (e.g., the Japan Meteorological Agency) or from the database of a weather information company. The weather information may include past weather information or current weather information. The weather information may include information on the hours of sunshine in the area where the vehicle 1 is located, and may also include information on the position of the sun.

The deterioration state assessment unit 62 estimates the cumulative amount of sunlight irradiance on the polarizing plate 43 from the position and direction of the vehicle 1 obtained from the locator 5 and weather information obtained through the DCM 6. Specifically, the deterioration state assessment unit 62 calculates the amount of sunlight irradiance incident on the HUD 10 or polarizing plate 43 at each time based on the sunshine hours in the area and the relationship between the position and direction of the vehicle 1 and the position of the sun.

At this time, it is preferable to take into account the attenuation of sunlight due to the UV-cutting function of the FWS3. Since the reflectance of sunlight reflected by the FWS3 also changes depending on the angle of incidence of sunlight on the FWS3, it is preferable to calculate the amount of irradiation taking into account the angle-dependent reflectance.

Furthermore, if the deterioration state assessment unit 62 determines from the map DB 5c and the vehicle 1 location information that the vehicle 1 is located in a covered parking lot, garage, etc., and sunlight is not irradiating the polarizing plate 43, it may set the amount of irradiation for that time to 0 (exclude it).

Furthermore, the deterioration state assessment unit 62 accumulates the amount of irradiation for the number of years (period of use) that have passed since the polarizing plate 43 was last used. The deterioration state assessment unit 62 assesses the deterioration state based on the accumulated amount of irradiation and provides the assessment result to the correction unit 63.

According to the second embodiment described above, information regarding the hours of sunlight and information for identifying the positional relationship between the polarizing plate 43 and the sun are acquired. The state of deterioration is then determined by estimating the cumulative amount of sunlight irradiated onto the polarizing plate 43. This improves the accuracy of determining the state of deterioration of the polarizing plate 43.

(Third embodiment)
As shown in Fig. 10, the third embodiment is a modification of the first embodiment. The third embodiment will be described, focusing on the differences from the first embodiment.

Sunlight that enters the HUD 10 and travels the opposite optical path to the display light to reach the display 40 is concentrated by the optical system 20, which acts as a magnifying optical system. This concentrating effect of the sunlight accelerates the deterioration of the polarizing plate 43 of the display 40. At this time, the degree of deterioration may differ between regions of the polarizing plate 43 due to unevenness in the amount of irradiation caused by the concentration of light or the parking environment, etc. For example, the deterioration of the region corresponding to the center of the polarizing plate 43 may progress more quickly than the deterioration of the region corresponding to the outer periphery of the polarizing plate 43.

Therefore, in the third embodiment, the polarizing plate 43 or screen 44 is virtually divided into multiple regions, and different correction amounts are applied between the multiple regions.

For example, as shown in Figure 10, the polarizing plate 43 or screen 44 may be virtually divided into nine areas A1 to A9. The deterioration state assessment unit 62 then assesses the deterioration state for each of the areas A1 to A9 individually. The correction unit 63 performs individual corrections for each of the areas A1 to A9.

The correction unit 63 may also apply the optimal correction amount to each region by filtering to output a gradation effect, so that the correction amount changes continuously on the screen 44. For example, if it is expected that the area corresponding to the central portion will deteriorate faster than the outer peripheral portion, the correction amount may be changed radially from the central portion to the outer peripheral portion. The correction amount here may be a correction amount for luminance or a correction amount for chromaticity.

According to the third embodiment described above, a display 40 is provided that includes a polarizing plate 43 whose deterioration state is determined and that forms an image on a screen 44. An optical system 20 is also provided as a magnifying optical system that magnifies the virtual image VRI. In this configuration, bias in the deterioration tendency may occur between multiple regions of the polarizing plate 43 due to the influence of the magnifying optical system. However, by applying different correction amounts between multiple regions depending on the bias in the deterioration tendency, it is possible to prevent a situation in which a biased deterioration in the display quality of the virtual image VRI occurs.

(Other embodiments)
Although multiple embodiments have been described above, the present disclosure should not be construed as being limited to those embodiments, and can be applied to various embodiments and combinations within the scope that does not deviate from the gist of the present disclosure.

In another embodiment, the brightness may be corrected by the correction unit 63, and the display color may be managed or adjusted by at least one of the user, car dealer, and vehicle inspection company.

In the first embodiment, the deterioration state assessment unit 62 may refer to a calendar date instead of the timer 53 and assess the deterioration state based on the number of days that have passed since the product was shipped.

In the second embodiment, the deterioration state assessment unit 62 may refer to both meteorological information and the detection results of the solar radiation sensor 4 to improve the accuracy of calculating the amount of solar radiation.

In another embodiment, of the pair of polarizers 42, 43 provided on either side of the liquid crystal in the liquid crystal panel 41, the polarizer 42 on the backlight side may have lower light resistance than the polarizer 43 on the mirror side. By using a cheaper polarizer 42, which is not expected to be exposed to sunlight, procurement costs can be reduced.

In another embodiment, of the pair of polarizers 42, 43 provided on either side of the liquid crystal in the liquid crystal panel 41, the polarizer 43 on the mirror side may have a lower iodine density than the polarizer 42 on the backlight side. By lowering the iodine density of the polarizer 43 placed in a position expected to be irradiated with sunlight, the rate of deterioration can be slowed.

In other embodiments, the polarizing plate placed in a position expected to be irradiated with sunlight may be a polarizing plate other than the polarizing plate 43 provided on the liquid crystal panel 41. Specifically, the polarizing plate may be a polarizing plate placed in the optical path of the HUD 10 to prevent damage to the liquid crystal panel 41. As an example of this, a polarizing plate may be used in a dustproof sheet that covers the window portion 11a of the HUD 10.

The control unit and method described herein may be implemented by a special-purpose computer comprising a processor programmed to perform one or more functions embodied in a computer program. Alternatively, the device and method described herein may be implemented by a special-purpose hardware logic circuit. Alternatively, the device and method described herein may be implemented by one or more special-purpose computers configured by a combination of a processor that executes a computer program and one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions executed by a computer on a computer-readable non-transitory tangible storage medium.

(Disclosure of technical ideas)
This specification discloses multiple technical ideas described in the following multiple clauses. Some clauses may be written in a multiple dependent form, where the subsequent clause alternatively refers to the preceding clause. These multiple dependent clauses define multiple technical ideas.

<Technical philosophy 1>
A virtual image display device that displays a virtual image (VRI) by reflecting display light of an image on a reflecting member (3),
a polarizing plate (43) that transmits a specific polarized light of the display light;
an image display control unit (61) that controls the display state of the image,
The image display control unit
a deterioration state determination unit (62) that determines the deterioration state of the polarizing plate;
and a correction unit (63) that corrects the display state in accordance with the deterioration state.

<Technical philosophy 2>
a display (40) configured to include the polarizer or separate from the polarizer and to form the image on a screen (44);
The virtual image display device according to Technical Idea 1, wherein the correction unit corrects the brightness of the image displayed on the screen.

<Technical philosophy 3>
Further provided is a storage medium (51a) storing a plurality of γ tables,
The virtual image display device according to Technical Concept 2, wherein the correction unit changes the γ table to be used depending on the deterioration state.

<Technical philosophy 4>
a display configured to include the polarizer or separately from the polarizer and to form the image on a screen;
The virtual image display device according to any one of Technical Ideas 1 to 3, wherein the correction unit corrects a display color of the image displayed on the screen.

<Technical philosophy 5>
The polarizing plate is disposed at a position where it is assumed that sunlight will be irradiated,
The virtual image display device according to any one of Technical Ideas 1 to 4, wherein the deterioration state determining unit determines the deterioration state caused by irradiation with sunlight.

<Technical philosophy 6>
The apparatus further includes a timer (53) that counts time and stops counting the time at a time when it is estimated that sunlight will be blocked from entering the polarizing plate,
The virtual image display device according to Technical Idea 5, wherein the deterioration state determination unit determines the deterioration state by referring to the timer.

<Technical philosophy 7>
The virtual image display device described in Technical Idea 5, wherein the deterioration state assessment unit assesses the deterioration state by estimating the cumulative amount of sunlight irradiated onto the polarizing plate from information regarding the hours of sunlight and information for identifying the positional relationship between the polarizing plate and the sun.

<Technical philosophy 8>
a display including the polarizing plate and forming the image on a screen;
and a magnifying optical system (20) for magnifying the virtual image,
A virtual image display device described in any one of technical ideas 5 to 7, wherein the correction unit applies different correction amounts between multiple areas (A1 to A9) of the polarizing plate depending on the bias in deterioration tendency due to the influence of the magnifying optical system between the multiple areas.

3: FWS (reflecting element), 10: HUD (virtual image display), 43: polarizing plate, 61: image display control unit, 62: deterioration state assessment unit, 63: correction unit, VRI: virtual image

Claims (6)

A virtual image display device that displays a virtual image (VRI) by reflecting display light of an image on a reflecting member (3),
a polarizing plate (43) that transmits a specific polarized light of the display light;
an image display control unit (61) that controls the display state of the image,
The image display control unit
a deterioration state determination unit (62) that determines the deterioration state of the polarizing plate;
a correction unit (63) that corrects the display state in accordance with the deterioration state ,
The polarizing plate is disposed at a position where it is assumed that sunlight will be irradiated,
The apparatus further includes a timer (53) that counts time and stops counting the time at a time when it is estimated that sunlight will be blocked from entering the polarizing plate,
The deterioration state determination unit determines the deterioration state due to irradiation of sunlight by referring to the timer . A virtual image display device that displays a virtual image (VRI) by reflecting display light of an image on a reflecting member (3),
a polarizing plate (43) that transmits a specific polarized light of the display light;
an image display control unit (61) that controls the display state of the image,
The image display control unit
a deterioration state determination unit (62) that determines the deterioration state of the polarizing plate;
a correction unit (63) that corrects the display state in accordance with the deterioration state ,
The polarizing plate is disposed at a position where it is assumed that sunlight will be irradiated,
The deterioration state assessment unit assesses the deterioration state due to sunlight irradiation by estimating the cumulative amount of sunlight irradiation on the polarizing plate from information regarding the hours of sunlight and information for identifying the positional relationship between the polarizing plate and the sun . a display (40) configured to include the polarizer or separate from the polarizer and to form the image on a screen (44);
The virtual image display device according to claim 1 , wherein the correction unit corrects the luminance of the image displayed on the screen. Further provided is a storage medium (51a) storing a plurality of γ tables,
The virtual image display device according to claim 3 , wherein the correction unit changes the γ table to be used depending on the deterioration state. a display configured to include the polarizer or separately from the polarizer and to form the image on a screen;
The virtual image display device according to claim 1 , wherein the correction unit corrects a display color of the image displayed on the screen. a display including the polarizing plate and forming the image on a screen;
and a magnifying optical system (20) for magnifying the virtual image,
The virtual image display device according to claim 1 or 2, wherein the correction unit applies different correction amounts between the multiple regions (A1 to A9 ) of the polarizing plate depending on the bias in deterioration tendency due to the influence of the magnifying optical system between the multiple regions.