JPWO2019151482A1 - Head-up display device - Google Patents

Abstract

An object of the present invention is to suppress heat generation due to infrared rays and deterioration due to ultraviolet rays of the intermediate screen (2). The head-up display device of the present invention includes an intermediate screen (2) on which an image projected from an image forming unit (1) is formed, and a magnifying optical system that magnifies an image formed on the intermediate screen (2). (3) and a light-transmitting display member (5) that allows the observer to recognize the image magnified by the magnifying optical system (3) as a virtual image, and the reference sunlight irradiated from the outside is the above-mentioned. When the intermediate screen (2) is reached, the sum of the integrated value of the spectral radiation optics of ultraviolet light (wavelength range 280 to 400 nm) and the integrated value of the spectral radiation optics of infrared light (wavelength range 760 to 2500 nm) is the visible light. The head-up display device is characterized in that it is 30% or less of the integrated value of the spectral emission illuminance (wavelength range 400 to 760 nm).

Description

The present invention relates to a head-up display device mainly used for a transportation machine such as an automobile.

Conventionally, a technique of applying a diffuser plate using a microlens array (MLA) as a screen to a head-up display (HUD), a laser projector, or the like has been proposed. When a microlens array is used, compared to the case where a diffuser such as a milk half plate or frosted glass is used, the diffused light is emitted at a required angle by controlling the shape of the microlens, and the light is used efficiently. There are merits such as being able to suppress speckle noise.

Since the display light of the head-up display (HUD) device is emitted from below toward the display unit (combiner) consisting of the front windshield or the half mirror in the vicinity thereof, the sunlight heads up from the opposite direction to this display light. There is a problem that a display element such as a transmissive liquid crystal (TFT) panel is heated and deteriorated by entering the display device and reversing a magnifying optical system made of a concave mirror or the like to collect light. As a method for solving this, a method of using a transmitting member or an infrared reflecting member that transmits visible light and absorbs infrared rays has been devised (Patent Documents 1 and 2).

On the other hand, in recent years, there has been a demand for a HUD device (AR-HUD: AR is an abbreviation for Augmented Reality, a virtual image distance of 6 m or more) in which the distance to the virtual image is longer and the size of the virtual image is larger than before. In such a HUD device, the focusing ratio of sunlight becomes even larger, and the heat problem becomes more serious. For example, when the virtual image distance is changed from 2.5 m to 15 m, it is said that sunlight is focused at a higher magnification and its irradiance increases about 9 times. Therefore, instead of a TFT panel having a high light absorption rate, a projection type HUD device that forms an image projected from an image forming unit such as a DMD (Digital Mirror Device) element on a transmissive intermediate screen having a low light absorption rate. Has been proposed (Non-Patent Documents 1 and 2).

JP-A-2017-909855 JP-A-2017-129861

IDW '15: proceedings of the International Display Workshops Vol.22, p.1094, PRJ4-4L (Augmented Reality Head-Up Display: Defining Brightness Requirements) DS 16 Proceedings: Proceedings for Display Summit 2016 held in Las Vegas in June (Next-Generation Augmented Reality Head-Up Display Design Considerations)

The inventors of the present application have found the following problems.
As described in Patent Documents 1 and 2, according to a method using a transmitting member or an infrared reflecting member that transmits visible light and absorbs infrared rays, a part of infrared rays in the wavelength spectrum of sunlight is removed. can do. According to these methods, it is possible to suppress the temperature rise of the portion of the intermediate screen of the projection type HUD device where sunlight is concentrated to some extent. However, in a HUD device having a long virtual image distance and a large virtual image size, the focusing ratio of sunlight is higher, so that this method may not be able to sufficiently suppress the temperature rise.

Further, Patent Document 2 defines that the reflectance of the infrared reflecting member at a wavelength of 700 to 1400 nm is set to a certain value or more. However, when the intermediate screen is made of resin, the influence of heat generated by absorption of wavelength components of 1400 nm or more cannot be ignored.

Further, when the ultraviolet light component among the wavelength components of sunlight is condensed on the intermediate screen, there is a problem that not only the problem of heat generation but also the material of the intermediate screen is deteriorated by the ultraviolet component of sunlight.

An object of the present invention is to provide a head-up display device that suppresses heat generation of an intermediate screen due to sunlight incident from the outside.

The present invention that solves the above problems
The intermediate screen on which the image projected from the image forming unit is formed, the magnifying optical system that magnifies the image formed on the intermediate screen, and the image magnified by the magnifying optical system are recognized by the observer as virtual images. It is a head-up display device including at least a light-transmitting display member for causing light transmission.
When the reference sunlight (AM1.5G) radiated from the outside into the head-up display device reaches the intermediate screen, the integrated value of the spectral irradiance of ultraviolet light (wavelength range 280 to 400 nm) and infrared light. A head-up display device characterized in that the sum of the integrated values of the spectral irradiances (wavelength range 760 to 2500 nm) is 30% or less of the integrated values of the spectral irradiances of visible light (wavelength range 400 to 760 nm). Is.

The head-up display device preferably includes an optical member having at least one function of an infrared cut filter, an ultraviolet cut filter, and an ND filter on the sunlight incident side of the intermediate screen. , It is more preferable that it is made of the same material as a part of the intermediate screen.

Further, in the present invention, when the reference sunlight (AM1.5G) reaches the intermediate screen, the maximum value of the irradiance in the intermediate screen surface is preferably 300 W / m ² or less.

In the present invention, the intermediate screen is preferably formed by forming a microlens array on at least one side of a resin film having a thickness of 0.15 to 0.4 mm or less.

Further, the head-up display device of the present invention is suitable when the virtual image distance is longer than 5 m.

According to the present invention, there is provided a head-up display device that suppresses heat generation of an intermediate screen due to sunlight incident from the outside.

It is sectional drawing which shows the schematic structure of the head-up display device (HUD) of this invention. The relationship between the film thickness and the temperature rise is shown. It is a schematic diagram which shows the measurement method which obtained the result of FIG. It is an irradiance spectrum of a reference sunlight (AM1.5G). This is an example of the absorption spectrum of the intermediate screen 2. It is a figure which shows the spectral irradiance of the sunlight absorbed by the intermediate screen when the reference sunlight of FIG. 4 is incident on the intermediate screen of FIG. It is a figure which shows the experimental result which measured the relationship between the irradiance and the temperature rise when the sunlight collected by a Fresnel lens irradiates an intermediate screen or a TFT panel. It is a figure which shows the result of converting the horizontal axis of FIG. 7A into a light condensing magnification. It is a figure which shows the experimental result when the optical member other than a Fresnel lens is inserted. It is a figure which shows the relationship between the temperature rise after correction and the condensing magnification. It is a figure which shows the spectral transmittance or the spectral reflectance of the optical member used in an Example / comparative example.

(Configuration of head-up display device)
FIG. 1 is a cross-sectional view showing an example of a schematic configuration of the head-up display device (HUD) of the present invention. The HUD of the present invention is mounted on a vehicle and mainly includes an image forming unit (PGU) 1, an intermediate screen 2, a concave mirror 3, a cover portion 4, a windshield 5, and a HUD module housing 6.

The image formed by the PGU is imaged on an intermediate screen. The intermediate screen forms a real image on the screen by expanding the divergence angle of the image light emitted from the PGU. The image light emitted from the intermediate screen reaches a display member (combiner) made of a windshield or the like through a magnifying optical system using a concave mirror or the like. The magnifying optics magnifies the image displayed on the intermediate screen, and the image light is reflected by the combiner consisting of the windshield and reaches the observer's eyes. This allows the observer to see the magnified virtual image. The cover portion is usually fitted in an opening provided in the dashboard, and dust invades into the housing of the HUD and suppresses deterioration of image quality due to adhesion to optical members such as an intermediate screen and a concave mirror. The cover is transparent and transmits light.

As the intermediate screen, various members can be applied regardless of whether it is a transmission type or a reflection type as long as it is an optical member having a diffusing action, but a transmission type screen in which a microlens array is formed on at least one surface of a transparent resin base material. Is preferably used. The microlens array can be formed by a known method. The mold used for molding the microlens array may be formed by cutting. Alternatively, a mold may be made by photolithography and a mold may be formed based on the mold. Any mold that can withstand molding of the microlens array sheet can be used.
For molding the microlens array, a means suitable for molding a resin film, such as injection molding, press molding, and molding by ultraviolet curing, can be widely used. Further, the sheet obtained by molding may be attached to a transparent base material. Further, the resin arranged on the transparent base material may be molded. As the transparent substrate, PC, PET, PMMA, PET, COP, glass and the like can be used, but PC, COP and glass are preferable in terms of optical physical characteristics and reliability in an in-vehicle environment.

FIG. 2 shows the relationship between the film thickness and the temperature rise. The plot of "actual measurement" marked with a circle in FIG. 2 represents the result of actual measurement of the temperature rise value when 5,000 W / m ² of sunlight is condensed on a PMMA sheet having a thickness of 1 mm. The plot of the “calculation result” marked with ■ in FIG. 2 is the result of calculating the thickness dependence by the heat transfer calculation.

FIG. 3 is a schematic view showing a measurement method obtained with the result of FIG. Sunlight was focused on the intermediate screen 8 by the Fresnel lens 7. For the irradiance of sunlight, the relationship between the distance from the Fresnel lens 7 to the intermediate screen 8 and the irradiance is measured in advance with an illuminometer, and the height of the Fresnel lens 7 is adjusted so that the desired irradiance can be obtained. did. The temperature of the intermediate screen was measured by the infrared camera 9. The result of FIG. 2 is an experimental result when a PMMA sheet having a thickness of 1 mm is placed instead of the intermediate screen 8. At this time, the emissivity for measuring the temperature with the infrared camera was 0.996 obtained from the absorption spectrum.

When the thickness of the intermediate screen 2 is reduced, the amount of sunlight that has entered from the outside of the vehicle is reduced and the heat generation of the intermediate screen 2 can be suppressed. Therefore, the thickness of the intermediate screen 2 can be set to 0.15 to 0.5 mm. preferable. For example, when the thickness of the intermediate screen 2 is reduced from 3 mm to 1 mm, as shown in FIG. 2, the temperature rise due to heat generation can be reduced by about 20%. Further, when the thickness is reduced to 0.3 mm, the temperature rise due to heat generation can be reduced to about 50%, and it can be seen that a large heat generation suppressing effect can be obtained by thinning the intermediate screen 2. On the other hand, if the thickness of the intermediate screen 2 becomes too thin, it tends to bend, which causes problems such as difficulty in handling when assembling the head-up display device and being easily affected by vibration when used in a vehicle. There is a fear.

(About the wavelength component of sunlight that affects the heat generation of the intermediate screen)
FIG. 4 is an irradiance spectrum of reference sunlight (AM1.5G). AM1.5G is an abbreviation for "Air Mass 1.5 Global", and ASTM G173-03 Reference Spectra Derived from SMART v. It is a solar spectroscopic irradiation spectrum defined by Global tilt of 2.9.2, and the irradiance obtained by integrating the wavelength range from 280 nm to 4000 nm is set to 1,001 W / m ² .
FIG. 5 is an example of the absorption spectrum of the intermediate screen 2. Here, the measurement result of the absorption spectrum of an intermediate screen in which a UV curable resin layer having a thickness of 0.05 mm is coated on a polycarbonate base material having a thickness of 0.3 mm and a microlens array pattern is formed on the surface thereof is shown.
FIG. 6 shows the spectral irradiance of sunlight absorbed by the intermediate screen when the reference sunlight of FIG. 4 is incident on the intermediate screen of FIG. 5, and the data of FIGS. 4 and 5 are integrated for each wavelength. It is the result of The temperature rise of the intermediate screen due to sunlight irradiation is proportional to the integrated value of the spectral irradiance absorbed by the intermediate screen. From the results of FIG. 6, it was found that the absorption at wavelengths around 350 nm, around 1680 nm, and on the longer wavelength side than 2000 nm was large.

(Method of attenuating components other than visible light of sunlight)
An example of a method for effectively attenuating the sunlight absorbed by the intermediate screen shown in FIG. 6 is shown below.
Generally, the windshield 5 is made of laminated glass, but by appropriately selecting the interlayer film thereof, the above-mentioned ultraviolet and infrared components can be effectively cut.
If a resin material is used as the cover portion 4, the resin alone can absorb ultraviolet rays. Further, more ultraviolet rays can be absorbed by adding or coating an ultraviolet absorber. If the cover portion is made of the same material as the intermediate screen 2 or the same material as the transparent base material of the intermediate screen 2, it is possible to significantly reduce the wavelength component of sunlight absorbed by the intermediate screen 2.

When the radiant intensity of ultraviolet rays or infrared rays of sunlight transmitted through the windshield 5 and the cover portion 4 is too high, an optical thin film can be laminated on the surface of the concave mirror to absorb the ultraviolet rays and infrared rays. Further, an optical thin film can be laminated on the surface of the cover portion 4 to have a function of reflecting ultraviolet rays and infrared rays. It is also possible to install a member that reflects infrared rays between the cover portion 4 and the intermediate screen 2. It is also effective to install the polarizing plate between the cover portion 4 and the intermediate screen 2 in order to reduce the irradiance of sunlight.

By combining these optical members, it is possible to attenuate the ultraviolet and infrared components of sunlight that enter the HUD device from the outside. In reference sunlight (AM1.5G), the integrated value of the spectral irradiance of ultraviolet light (wavelength range 280 to 400 nm) is about 5% of the integrated value of the spectral irradiance of the entire wavelength region (wavelength range 250 to 2500 nm). It is a ratio. By attenuating this ratio to 0.5% or less by combining the above optical members, it is possible to prevent ultraviolet deterioration of the intermediate screen, which is preferable. Further, the integrated value of the spectral irradiance of ultraviolet light (wavelength range 280 to 400 nm) and the spectral irradiance of infrared light (wavelength range 760 to 2500 nm) when the reference sunlight (AM1.5G) reaches the intermediate screen. It is necessary to make the sum of the integrated values of the above 30% or less of the integrated value of the spectral irradiance of visible light (wavelength range 400 to 760 nm) in order to suppress the temperature rise of the intermediate screen, and to make it 20% or less. Is preferable.
Under this condition, even if sunlight enters the HUD device from the outside of the vehicle and irradiates the intermediate screen 2, the deterioration of the intermediate screen due to ultraviolet rays can be prevented and the temperature rise of the intermediate screen due to the concentration of sunlight can be suppressed. ..

(Method of further suppressing heat generation of the intermediate screen due to sunlight condensing)
When the magnification of the virtual image is large, the focusing magnification of sunlight entering from the outside of the vehicle is also large, so that the above method may not be effective in suppressing the temperature rise of the intermediate screen. In such cases, use a windshield with low transmittance, use a windshield laminated with Fresnel half mirrors, reduce the transmittance of the cover, reduce the reflectance of the concave mirror, and reduce the transmittance of the intermediate screen. A method such as laminating on low glass and arranging the glass surface on the concave mirror side can be used.
When the Fresnel half mirror is laminated on the windshield, the magnification of the image light is affected by the effect of the Fresnel half mirror, but the sunlight is not affected by it, so the collection until the sunlight reaches the intermediate screen. The light rate can be kept low.

Of the above methods, it is preferable to use a windshield having a low transmittance, because it is possible to simultaneously improve the decrease in image contrast during sunlight irradiation. Sunlight that enters from outside the vehicle and reaches the screen is reflected by the screen, and part of it reaches the observer's eyes, reducing image contrast. At this time, one of the methods of lowering the transmittance of the cover portion, lowering the reflectance of the concave mirror, laminating the intermediate screen on the glass having low transmittance and arranging the glass surface on the concave mirror side, or a combination thereof. If is adopted, these members are transmitted twice before the sunlight returns to the observer's pupil to attenuate the intensity of the sunlight. On the other hand, since the image light emitted from the PGU passes through these members only once, it is possible to suppress a decrease in image contrast due to sunlight. When a windshield with low transmittance is adopted, it is not effective in preventing a decrease in image contrast because it only transmits the windshield once before the sunlight returns to the observer's eyes.

Hereinafter, the present invention will be described in more detail based on examples of the present invention.

(Example)
FIG. 7A is an experimental result of measuring the relationship between the irradiance and the temperature rise when the sunlight focused by the Fresnel lens irradiates the intermediate screen or the TFT panel. Here, the Fresnel lens replaces the image magnifying optical system (concave mirror and the like) in the HUD.
In the experiment, the measurement system shown in FIG. 3 was used, and the irradiance of the focused sunlight was changed by changing the distance between the Fresnel lens and the intermediate screen or the TFT panel. As the intermediate screen, a UV curable resin (thickness 0.05 mm) is coated on one side of a PC film base material (thickness 0.3 mm), and a microlens array is formed on the surface thereof. The sunlight was irradiated from the surface of the PC film substrate with the UV curable resin side facing down. The emissivity of the intermediate screen for temperature measurement by the infrared camera can be obtained from the absorption spectrum, and 0.902 was adopted in this example. The TFT panel used is taken out from the in-vehicle HUD device, and its emissivity can be obtained from the absorption spectrum, and is set to 0.980 in this example.

Here, the Fresnel lens used in the experiment of FIG. 7A is made of acrylic resin. The horizontal axis of the graph is the irradiance after a part of the wavelength component of sunlight is absorbed by the Fresnel lens made of acrylic resin, and the wavelength spectrum irradiated to the intermediate screen or TFT panel is AM1.5G standard sunlight. There will be some divergence. In order to understand the relationship between the experimental results of FIG. 7A and the geometrical optics focusing magnification of sunlight by the optical system in the HUD device, the horizontal axis of FIG. 7A is the result of condensing sunlight at many times. You need to know if it corresponds. Therefore, the geometrical optics focusing magnification of sunlight was obtained by the following procedure 1.

(Procedure 1)
Back calculation is performed from the transmission spectrum of the Fresnel lens, and the horizontal axis is calculated and corrected to the irradiance without absorption of the Fresnel lens. The geometrical optics condensing magnification of sunlight is obtained by dividing the corrected irradiance by the irradiance of sunlight at the time of the experiment.
FIG. 7B shows the result of converting the horizontal axis of FIG. 7A into the focusing magnification according to the procedure 1. At this time, the horizontal axis was corrected to 1.24 times according to the procedure 1. Solar irradiance at the time of addition of the TFT panel experiment 640W / ^{m 2,} at the time of the intermediate screen experiments was 540 W / ^{m 2.}
From FIG. 7B, it can be seen that the temperature rise of the intermediate screen is proportional to the irradiance of sunlight incident on the screen. This is because the rising temperature of the intermediate screen is proportional to the irradiance of sunlight absorbed by the intermediate screen. Comparing the intermediate screen and the TFT panel, it is also clear that the intermediate screen absorbs less sunlight, so that the temperature rise due to solar condensing is smaller.

FIG. 8A shows the experimental results when an optical member other than the Fresnel lens is inserted. The spectral transmittance or spectral reflectance spectrum of each optical member including the Fresnel lens shown in FIG. 8A is shown in FIG.
The horizontal axis of FIG. 8A is the same as that of FIG. 7B when the optical member is not inserted at the position of the optical member 10 of FIG. 3 and the sunlight focused by the Fresnel lens is focused on the intermediate screen or the TFT panel. The geometrical optics focusing magnification of. The vertical axis of FIG. 8A is the temperature rise of the intermediate screen when the acrylic Fresnel lens and the optical member such as the windshield and the cover member are combined.

Since the acrylic Fresnel lens is not used in the actually mounted HUD device, the spectral spectrum of the sunlight focused on the intermediate screen or the TFT panel in this experiment is different from the actual HUD device. Further, in an actual HUD device, a concave mirror is usually used to form a virtual image, but in the experimental system of FIG. 3, since only a transmission member can be inserted as the optical member 10, the effect of the concave mirror can be actually measured. Not. As mentioned above, the temperature rise of the intermediate screen is proportional to the irradiance of sunlight absorbed by the intermediate screen. Therefore, the temperature rise of the intermediate screen in the HUD device actually mounted on the vehicle can be estimated by calculating and correcting the experimental data of FIG. 8A from the transmission spectrum of the acrylic Fresnel lens and the reflection spectrum of the concave mirror. The procedure is shown below.

(Procedure 2)
By multiplying the spectral spectrum of sunlight, the spectral transmission spectrum of the acrylic Frenel lens, and the spectral absorption spectrum of the intermediate screen or TFT panel at each wavelength, the intermediate screen or TFT panel with the acrylic Frenel lens Find the spectral emission illuminance of the absorbed sunlight.
(Procedure 3)
By integrating the results of step 2 in the wavelength range of 250 to 2500 nm, the irradiance of sunlight absorbed by the intermediate screen or TFT panel with the Fresnel lens is determined.
(Procedure 4)
By multiplying the spectral spectrum of sunlight by the spectral absorption spectrum of the intermediate screen or TFT panel at each wavelength, the spectral irradiance of sunlight absorbed by the intermediate screen or TFT panel without an acrylic Fresnel lens Ask for.
(Procedure 5)
By integrating the results of step 4 in the wavelength range of 250 to 2500 nm, the irradiance of sunlight absorbed by the intermediate screen or TFT panel without the Fresnel lens is determined.
(Procedure 6)
From the ratio of the irradiance obtained in steps 3 and 5, it is determined how many times the irradiance of sunlight absorbed by the intermediate screen or the TFT panel without the Fresnel lens is higher than that with the Fresnel lens.
(Procedure 7)
The vertical axis is corrected by multiplying the temperature rise obtained in the experiment by the magnification obtained in step 6.
(Procedure 8)
By multiplying the reflection spectrum of the concave mirror with the spectral irradiance of sunlight absorbed by the intermediate screen or TFT panel obtained in step 4, the spectral radiation of sunlight absorbed by the intermediate screen or TFT panel when the concave mirror is present Find the irradiance. The irradiance obtained by integrating this in the wavelength range of 250 to 2500 nm is obtained, and the ratio to the irradiance obtained in step 5 is calculated. The vertical axis is further corrected by multiplying this ratio by each temperature rise value obtained in step 7.

The result of correcting the vertical axis of FIG. 8A by the above steps 2 to 8 is shown in FIG. 8B. Here, it is assumed that two concave mirrors are used. FIG. 8B (A) shows the temperature rise assuming that sunlight is directly focused on the intermediate screen. The reason why the temperature rise is significantly increased as compared with FIG. 8A (A) is that the UV light absorbed by the acrylic Fresnel lens is absorbed by the intermediate screen. On the other hand, from the comparison between FIGS. 8B (E) and 8A (E), the influence of the presence or absence of the acrylic Fresnel lens on the TFT panel is smaller than that on the intermediate screen. This is because the TFT panel has a high absorption rate that is almost constant from UV to the visible region.

FIG. 8B (B) is Example 1 of the present invention. Sunlight is focused on the intermediate screen via the windshield, cover member, infrared reflective filter and two concave mirrors. In this case, it can be read from the graph that the temperature rise becomes 45 ° C. when the light collection magnification is about 45 times. When the environmental temperature inside the HUD device reaches a maximum of 105 ° C, when the temperature rise of the intermediate screen is 45 ° C, the temperature rise of the intermediate screen reaches 150 ° C, which is the melting point of the PC film base material, so that the temperature rise is maximized. However, it is necessary to keep the temperature below 45 ° C.

FIG. 8B (C) is a second embodiment of the present invention. As a result of adding an infrared ND filter in addition to the optical member shown in FIG. 8B (B), the temperature rise is 45 ° C. when the focusing magnification is about 130 times, and it can be used even at a higher focusing magnification. I know I can do it.

Table 1 is a list of combinations of optical members used in Examples, Comparative Example 1 and experiments of the present invention.

In order to brighten the image of the HUD device, it is necessary to increase the transmittance of each optical member with respect to visible light. On the other hand, in order to prevent the intermediate screen from overheating due to the condensing of sunlight entering from the outside, the transmittance of each optical member other than visible light should be reduced. Therefore, when the ratio of the sum of the irradiance of ultraviolet light and infrared light to the irradiance of visible light is taken, the sum of the irradiance of ultraviolet light and infrared light should be 30% or less of the irradiance of visible light. Yes, it is preferably 20% or less. The total irradiance of ultraviolet light, visible light, and infrared light is 300 W / m ² or less, and preferably 260 W / m ² or less.

(Comparison example)
FIG. 8B (D) shows the temperature rise of the intermediate screen in the case of the conventional configuration in which sunlight is focused on the intermediate screen via each member of the windshield, the cover member, and the concave mirror. With a conventional projection HUD device with a virtual image distance of ~ 2.5 m, which is equivalent to the direct-view HUD device already installed in commercial vehicles, the optical focusing magnification of sunlight focused on the intermediate screen is about 11 times. However, when the virtual image distance is 7 m, it is about 5 times that, when the virtual image distance is 15 m, it is about 9 times, and when the virtual image distance is infinite, it is about 16 times (Non-Patent Document 2). When read from the graph of FIG. 8B (D), the temperature rise is about 20 ° C. when the virtual image distance is about 2.5 m, but the temperature of the intermediate screen is when the virtual image distance is about 7 m (condensing magnification to about 55 times). The rise reaches about 70 ° C. and is thermally deformed by overheating. Therefore, when the virtual image distance of the conventional HUD device is increased to AR (Augmented Reality), if the virtual image distance exceeds 5 m, the intermediate screen may be overheated and damaged due to the concentration of sunlight entering the device. There is. That is, the application of the present invention is effective in the HUD where the virtual image distance exceeds 5 m, and is particularly effective when the virtual image distance is 6 m or more.

FIG. 8B (E) shows the relationship between the focusing ratio and the temperature rise when it is assumed that sunlight is directly focused on the TFT panel. FIG. 8B (F) shows the relationship between the light collection magnification and the temperature rise of Example 2 in which sunlight is focused on the TFT panel via the windshield, the cover member, the polarizing plate, and the two concave mirrors. Although the temperature rise of the TFT panel is considerably suppressed by inserting each member, it can be seen that even in this configuration, the temperature rise is larger than that using the intermediate screen such as Comparative Example 1 in FIG. 8B (D).

This application claims priority on the basis of Japanese Patent Application No. 2018-017463 filed on 2 February 2018 and incorporates all of its disclosures herein.

1: Image forming unit (PGU) 2: Intermediate screen 3: Concave mirror 4: Cover part 5: Windshield 6: HUD module housing 7: Fresnel lens 8: Intermediate screen 9: Infrared camera 10: Optical member

Claims (6)

The intermediate screen on which the image projected from the image forming unit is formed, the magnifying optical system that magnifies the image formed on the intermediate screen, and the image magnified by the magnifying optical system are recognized by the observer as virtual images. It is a head-up display device including at least a light-transmitting display member for causing light transmission.
When the reference sunlight (AM1.5G) radiated from the outside into the head-up display device reaches the intermediate screen, the integrated value of the spectral irradiance of ultraviolet light (wavelength range 280 to 400 nm) and infrared light. A head-up display device characterized in that the sum of the integrated values of the spectral irradiances (wavelength range 760 to 2500 nm) is 30% or less of the integrated values of the spectral irradiances of visible light (wavelength range 400 to 760 nm). .. The first aspect of the head-up display device is characterized in that an optical member having at least one function of an infrared cut filter, an ultraviolet cut filter, and an ND filter is provided on the sunlight incident side of the intermediate screen. The head-up display device described. The head-up display device according to claim 2, wherein the optical member is made of the same material as a part of the intermediate screen. Any of claims 1 to 3, wherein when the reference sunlight (AM1.5G) reaches the intermediate screen, the maximum value of the irradiance in the intermediate screen surface is 300 W / m ² or less. The head-up display device described in. The head-up display according to any one of claims 1 to 4, wherein the intermediate screen is formed by forming a microlens array on at least one side of a resin film having a thickness of 0.15 to 0.4 mm or less. apparatus. The head-up display device according to any one of claims 1 to 5, wherein the virtual image distance is longer than 5 m.

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