Combiner and head-up display device using same

The combiner has a reflecting surface that reflects incident light. When the incident light has an incident angle in a range from 0° to 25°, inclusive, defined as a first value, in a wavelength range from 400 nm to 700 nm, inclusive, the upper limit wavelength of a wavelength range having a reflectance of 90% or more of the reflectance peak of the incident light is shorter than 700 nm. When the incident angle takes a second value in a range from 60° to 85°, inclusive, in the wavelength range from 400 nm to 700 nm, inclusive, the reflectance peak of an S-wave component contained in the incident light has a wavelength shorter than 570 nm.

BACKGROUND

1. Technical Field

The present disclosure relates to a combiner that reflects a part of incident light and also relates to a head-up display device equipped with the combiner.

2. Description of the Related Art

A head-up display (hereinafter, may be referred to an HUD) device is used for showing operating information for car drivers and airplane pilots. The HUD device projects information such that the information overlaps with an image of the driver's view through the windshield. Therefore, the HUD device needs not only high transmittance so that the driver clearly sees the view ahead but also high reflectance so that the driver clearly sees a reflection image. However, transmittance and reflectance have a “trade-off” relation. A combiner improves reflectance, keeping within legal restraints about transmittance (for example, see International Publication No. 2016/056617).

SUMMARY

The present disclosure provides a technique for suppressing emission of colored reflection light from a combiner.

A combiner of an aspect of the present disclosure has a reflecting surface that reflects incident light. According to the combiner, when the incident angle of the incident light takes a first value in a range from 0° to 25°, inclusive, in a wavelength range from 400 nm to 700 nm, inclusive, the average value of reflectance of the incident light is 30% or greater, and the upper-limit wavelength of a wavelength range having a reflectance of 90% or more of a reflectance peak of the incident light is shorter than 700 nm. Besides, when the incident angle of the incident light takes a second value in a range from 60° to 85°, inclusive, in the wavelength range from 400 nm to 700 nm, inclusive, a reflectance peak of a S-wave component of the incident light has a wavelength shorter than 570 nm.

Another aspect of the present disclosure is a head-up display device. The device has a display that emits display light, a reflecting member that reflects the display light, and the aforementioned combiner into which the light reflected by the reflecting member is fed as incident light.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Prior to describing an exemplary embodiment of the present disclosure, problems in a device of the related art are described.

While driving, reflection of an HUD device into the windshield is a nuisance to the driver's view. When the HUD device has a combiner, the driver's view is further interrupted by the reflection of the combiner into the windshield. Further, the reflection seen from the driver varies as change in the relative position and relative angle between the windshield and the HUD device. According to an HUD device using a combiner, generally, only the optical system in the HUD device is designed so as to have an optimum arrangement. However, a problem occurs in a situation in which sunlight coming through the windshield diffuses on the housing of the HUD device. The diffused light reflects off the combiner and further reflects off the windshield, then coming to the driver. The light, as it is colored, becomes a nuisance to the driver's view.

The head-up display (HUD) device is disposed on the instrumental panel; the combiner is disposed on the inner side of the windshield seen from the driver's seat. The display light from the display of the HUD device is reflected by a reflecting member and is fed into the combiner, which forms a virtual image on the combiner. The driver sees the virtual image containing information as if it is shown on the windshield.

When sunlight comes into the car through the windshield, it reflects off the housing of the HUD device and then reflects off the combiner. In the reflection at the housing, the sunlight is separated into an S-wave component and a P-wave component; further, in the reflection at the combiner, the S-wave component becomes yellow while the P-wave component becomes blue. The blue P-wave component mostly goes outside of the car through the windshield. However, the yellow S-wave component is reflected by the windshield, by which yellow reflection of a combiner axis and a cover of the housing of the HUD device interrupts the driver's view. The structure described below addresses the problem.

Hereinafter, the HUD device of an exemplary embodiment of the present disclosure is described. Throughout the description, the wordings ‘parallel’ and ‘perpendicular’ may be not mentioned in a strict sense; they may contain the margin of error. Similarly, the wording ‘substantially (the same)’ means the same in an approximate range.

FIG. 1is an external view showing the structure of HUD device100in accordance with an exemplary embodiment.FIG. 2is a cross-section view, taken along line2-2ofFIG. 1, showing the structure of HUD device100. As shown inFIG. 1andFIG. 2, a Cartesian coordinate system having an x-axis, a y-axis, and a z-axis is defined. The x-axis and the y-axis orthogonally cross to each other in a plane that includes the bottom of HUD device100. The z-axis is vertical to the x-axis and the y-axis and extends in the height direction of HUD device100. Each positive direction of the x-axis, the y-axis, and the z-axis is defined to respective direction shown by the arrows inFIG. 1andFIG. 2. The negative direction of each axis is opposite to the direction shown by each of the arrows. The positive direction of the z-axis means the upper-face side or the upper side, and the negative direction of the z-axis means the lower-face side or the lower side.

Housing10has bottom20. Wall22is disposed on bottom20so as to extend from the edge of bottom20along the positive direction of the z-axis. The top of housing10is open into outside, and lid14(will be described below) is attached thereto. Housing10and lid14form a shell of HUD device100. The shell accommodates shielding cover12, combiner30, display50, transparent cover54, reflecting member56, and stopper58.

Shielding cover12has first end part18adisposed in the positive direction of the x-axis and second end part18bdisposed in the negative direction of the x-axis. Second end part18bis fixed to housing10, while first end part18ais not fixed to anything. At least a part of shielding cover12is made of, for example, a flexible synthetic resin. By virtue of the flexibility, when a part close to first end part18ais pressed along the negative direction of the z-axis, shielding cover12is deformed such that first end part18acomes close to transparent cover54.

Lid14, which is disposed on the upper end of wall22of housing10, partly covers the opened top of housing10. Lid14has opening16at the center of its upper side, and combiner30protrudes through opening16.FIG. 1shows a state where lid14is removed.

Display50is, for example, a liquid crystal display; specifically, a 7-segment display. Display50outputs display light from output plane52. The 7-segment display employs a single-colored segment LCD, for example. Output plane52is disposed with a tilt so that the display light from it goes into reflecting member56. Transparent cover54, which is disposed on the upper side of display50and on the lower side of shielding cover12, covers output plane52. Transparent cover54is formed of a transparent resin, for example. The display light fed from display50toward reflecting member56penetrates transparent cover54. Transparent cover54protects display50from an object accidentally fallen into housing10through opening16. Reflecting member56is a mirror and is disposed in the upper side of transparent cover54. The display light fed from display50penetrates transparent cover54. Reflecting member56reflects the light toward reflecting surface32of combiner30.

As described earlier, combiner30is disposed to housing10so as to protrude through opening16. Combiner30is, for example, a half mirror. Combiner30is formed of a resin-molded component and a semi-transmitting film, such as a dielectric multilayer, vapor-deposited on one surface of the resin-molded component. As the semi-transmitting film also serves as a reflection film, it is described in the description below as reflecting surface32that reflects incident light. Combiner30is semipermeable, which enables the driver to look ahead through combiner30.

In the standing state of combiner30, the display light emitted from display50reflects off reflecting member56and then comes to reflecting surface32. At least a part of the light that hits reflecting surface32is reflected toward the driver. Through the structure, the driver sees the information projected on combiner30as if it overlaps with the view ahead through the windshield. The information as images shown to the driver includes the followings, for example: the current speed of the car, a remaining amount of the fuel, the distance to a destination, a traveling direction, the name of the present location, and names of neighboring facilities and shops.

Stopper58is disposed on the lower side of shielding cover12. InFIG. 2, a clearance is disposed between first end part18aand stopper58. As described earlier, in a case where shielding cover12is deformed so that first end part18acomes close to transparent cover54, stopper58holds first end part18aand prevents shielding cover12from being excessively deformed such that first end part18agoes down further. If first end part18ais lowered excessively, a large stress can be exerted onto a part to which second end part18bis fixed, or first end part18acan make contact with transparent cover54. The support of stopper58also prevents the fixing part and transparent cover54from being damaged.

As shown inFIG. 2, sunlight80comes into the car through windshield70. The workings of the device under the situation is described below. In the description below, combiner130is referred as a comparative combiner and combiner30is referred as the combiner of the exemplary embodiment.

On reflecting off shielding cover12or lid14, sunlight80is separated into first S-wave component82aand first P-wave component84a. First S-wave component82ais perpendicular to an incident plane while first P-wave component is parallel to the incident plane. The incident plane contains incident light that enters into combiner30(130) and reflecting light that reflects off combiner30(130). First S-wave component82aand first P-wave component84aenter into combiner30(130), having incident angle α of approximately 70° with respect to normal line N of combiner30(130).

When first S-wave component82aand first P-wave component84aare reflected by combiner130having comparative reflection characteristics, first S-wave component82abecomes yellow second S-wave component82band first P-wave component84abecomes blue second P-wave component84b. At that time, second S-wave component82band second P-wave component84bhave reflection angle β of approximately 70° with respect to normal line N of combiner30(130).

Second S-wave component82band second P-wave component84benters windshield70, having incident angle γ of approximately 70° with respect to normal line O of windshield70. When the incident light has an incident angle of approximately 70°, windshield70has a reflectance of 41% for the S-wave component and has a reflectance of 7% for the P-wave component. Therefore, second P-wave component84bmostly passes though windshield70as third P-wave component84cinFIG. 2. When second S-wave component82bhits windshield70, third S-wave component82creflects off windshield70, having reflection angle δ of approximately 70° with respect to normal line O of windshield70. Like second S-wave component82b, third S-wave component82cis yellow, which is seen by the driver as yellow reflection.

In combiner130, reflection characteristics of the S-wave component causes the yellow reflection. The reflection characteristics of the S-wave component is the result of designing combiner130with no consideration of reflection characteristics of incident light at an incident angle of approximately 70°. To reduce the yellow reflection, combiner30of the exemplary embodiment processes the reflected color of light having an incident angle of approximately 70° so as to be whitish. First, in order to describe the reflection characteristics of combiner30, the reflection characteristics of combiner130which generates the yellow reflection will be described below.

FIG. 3AandFIG. 3Bshow reflection characteristics of combiner130as a comparative device to combiner30. Specifically,FIG. 3Ashows reflection characteristics at incident angle α of 0°. The reflection characteristics show a relation between reflectance with respect to incident light and wavelength of the incident light. In the wavelength range from 400 nm to 700 nm, inclusive, in the visible region (hereinafter, referred to the first wavelength range), peak P1of the reflectance of the incident light has a wavelength of 440 nm. A wavelength range having a reflectance of 90% or more of peak P1is from 420 nm to 710 nm, inclusive. A wavelength range having a reflectance of 80% or more of peak P1is from 410 nm to 730 nm, inclusive.

FIG. 3Bshows reflection characteristics at incident angle α of 70°. The reflection characteristics show a relation between reflectance with respect to the incident light and wavelength of the incident light. In the description, incident angle α of 0° is defined as a first value and incident angle α of 70° is defined as a second value; that is, the first value is smaller than the second value. In the first wavelength range, peak P2of the reflectance of S-wave component82included in the incident light has a wavelength of 590 nm. The wavelength of peak P2belongs to the wavelength range of yellow light that ranges from 570 nm to 590 nm, inclusive. A wavelength range having a reflectance of 90% or more of peak P2is from 550 nm to 630 nm, inclusive. A wavelength range having a reflectance of 80% or more of peak P2is from 530 nm to 650 nm, inclusive. In the first wavelength range, peak P3of the reflectance of P-wave component84included in the incident light has a wavelength of 480 nm. The wavelength of peak P3belongs to the wavelength range of blue light that ranges from 400 nm to 480 nm, inclusive. Due to the characteristics above, second S-wave component82bbecomes yellow and second P-wave component84bbecomes blue.

FIG. 3Cshows the structure of a semi-transmitting film on reflecting surface132of combiner130. The forming process of the semi-transmitting film is specifically described with reference toFIG. 3C. In the description below, the reference wavelength is assumed to be 500 nm. The semi-transmitting film is a dielectric multilayer film having seven layers. The seven layers are formed by vacuum deposition with the following materials layered from the side of a base member: the first layer of SiO2with a film thickness of 162 nm; the second layer of Ta2O5with a film thickness of 101 nm; the third layer of SiO2with a film thickness of 115 nm; the fourth layer of Ta2O5with a film thickness of 26 nm; the fifth layer of SiO2with a film thickness of 135 nm; the sixth layer of Ta2O5with a film thickness of 47 nm; and the seventh layer of SiO2with a film thickness of 120 nm. Taking difference in refractive index of SiO2and Ta2O5into account, the film is formed of alternately layered SiO2and Ta2O5. A desired reflection characteristic is obtained by changing the film thickness of each layer and the number of layers. As for combiner30having reflection characteristics shown inFIG. 4A,FIG. 4B,FIG. 5A, andFIG. 5B, a semi-transmitting film is formed on reflecting surface32. In the forming process, each layer is formed while being monitored the reflectance of an optical monitor glass disposed at the center of a deposition dome. When the reflectance of the optical monitor glass reaches a desired value (corresponding to a desired film thickness), the deposition process is stopped. Such structured semi-transmitting film has reflection characteristics to incident light at an incident angle of 0° shown inFIG. 3AandFIG. 3B.

Next, an example of the reflection characteristics of combiner30is described, with reference toFIG. 4AandFIG. 4B. Each ofFIG. 4AandFIG. 4Bshows an example where the average reflectance of the first wavelength range is set to 30%. Setting the average reflectance to 30% allows the driver to have increased visibility through the combiner. Generally, the lower the average reflectance, the higher the transparence of the combiner, which means enhanced visibility of the driver; on the other hand, the lower the average reflectance, the more increase the necessity of the illumination intensity for a liquid crystal display (hereinafter, LCD). An image shown by the LCD of the display is projected on the combiner to obtain a virtual image. Under the state with lowered average reflectance, the LCD has to be illuminated by intense light to maintain sufficient brightness of the virtual image to be formed on the combiner. For example, display50is formed of a blue LED (light emitting diode). Increasing illumination light for the LCD increases the current value of the LED, further increasing the cost of the LED driver. Besides, such a device tends to have a large housing for sufficient heat dissipation. Considering above condition, the average reflectance is preferably 30% or greater when the device has a sufficient heat dissipation performance.

FIG. 4Ashows reflection characteristics at incident angle α of 0°. The reflection characteristics show a relation between reflectance with respect to incident light and wavelength of the incident light. In the first wavelength range, peak P1′ of the reflectance of the incident light has a wavelength of 610 nm. A wavelength range having a reflectance of 90% or more of peak P1′ is from 380 nm to 690 nm, inclusive (hereinafter, this range is referred to as the second wavelength range). A wavelength range having a reflectance of 80% or more of peak P1′ is from 380 nm to 710 nm, inclusive (hereinafter, this range is referred to as the third wavelength range). Therefore, the upper-limit wavelength of the second wavelength range is shorter than the upper-limit wavelength of the wavelength range having a reflectance of 90% or more of peak P1. Further, the upper-limit wavelength of the third wavelength range is shorter than the upper-limit wavelength of the wavelength range having a reflectance of 80% or more of peak P1.

FIG. 4Bshows reflection characteristics at incident angle α of 70°. The reflection characteristics show a relation between reflectance with respect to the incident light and wavelength of the incident light. In the first wavelength range, peak P2′ of the reflectance of S-wave component82included in the incident light has a wavelength of 540 nm, which is shorter than the lower-limit wavelength of the wavelength range of yellow light that ranges from 570 nm to 590 nm, inclusive. A wavelength range having a reflectance of 90% or more of peak P2′ of S-wave component82is from 480 nm to 610 nm, inclusive. A wavelength range having a reflectance of 80% or more of peak P2′ of S-wave component82is from 460 nm to 650 nm, inclusive. As described above, the upper-limit wavelength of the wavelength range having a reflectance of 90% or more of peak P2′ is shorter than 620 nm. On the other hand, in the first wavelength range, peak P3′ of the reflectance of P-wave component84included in the incident light has a wavelength of 400 nm, which equals to the lower-limit wavelength of the wavelength range of blue light that ranges from 400 nm to 480 nm, inclusive. The characteristics above allows not only second S-wave component82bto have less yellow component but also second P-wave component84bto have less blue component.

Combiner30having the characteristics shown inFIG. 4AandFIG. 4Bhas a base member made of an optical resin (ne=1.53). After the base member is injection-molded, a semi-transmitting film is formed on a surface of the base member as reflecting surface32. Hereinafter, the forming process of the semi-transmitting film is described in detail with reference toFIG. 4C.FIG. 4Cshows the structure of the semi-transmitting film of combiner30. In the description below, the reference wavelength is assumed to be 500 nm. The semi-transmitting film is a dielectric multilayer film having five layers. The five layers are formed by vacuum deposition with the following materials layered from the side of the base member: the first layer of SiO2with a film thickness of 402 nm; the second layer of Ta2O5with a film thickness of 54 nm; the third layer of SiO2with a film thickness of 81 nm; the fourth layer of Ta2O5with a film thickness of 57 nm; and the fifth layer of SiO2with a film thickness of 78 nm. Such structured semi-transmitting film has reflection characteristics at an incident angle of 0° shown inFIG. 4A. The reflection characteristics show an average reflectance of 30% in the first wavelength range. Further, the S-wave has a reflected color of white when incident light at an incident angle of 70° hits the semi-transmitting film according toFIG. 4B.

Each ofFIG. 5AandFIG. 5Bshows reflection characteristics of another example in which the average reflectance of the first wavelength range is set to 35%. From the point of the cost of the LED driver and/or in a case where it is difficult to ensure a sufficient heat dissipation performance, the average reflectance is preferably set to 35%. This is because setting the average reflectance to 35% allows the combiner to have enough brightness without increasing the cost of the LED driver and without deteriorating the heat dissipation performance. Besides, compared to the case in which the average reflectance is determined to 30%, setting the average reflectance to 35% decreases the probability of lack of brightness caused by lack of the current value of the LED.

FIG. 5Ashows reflection characteristics at incident angle α of 0°. The reflection characteristics show a relation between reflectance with respect to incident light and wavelength of the incident light. In the first wavelength range, peak P1″ of the reflectance of the incident light has a wavelength of 550 nm. A wavelength range having a reflectance of 90% or more of peak P1″ is from 470 nm to 640 nm, inclusive. A wavelength range having a reflectance of 80% or more of peak P1″ is from 450 nm to 670 nm, inclusive. That is, both the wavelength ranges above-having a reflectance of 90% or more and 80% or more of the peak—have the upper-limit wavelength shorter than 700 nm. The upper-limit wavelength of the wavelength range having a reflectance of 90% or more of the peak value of reflectance is shorter than the upper-limit wavelength of the comparative example; similarly, the upper-limit wavelength of the wavelength range having a reflectance of 80% or more of the peak value of reflectance is shorter than the upper-limit wavelength of the comparative example. Further, the lower-limit wavelength of the wavelength range having a reflectance of 90% or more of the peak value of reflectance is longer than 460 nm. Furthermore, the wavelength range having a reflectance of 90% or more of the peak value of reflectance is narrower than the wavelength range of the comparative example. Similarly, the wavelength range having a reflectance of 80% or more of the peak value of reflectance is narrower than the wavelength range of the comparative example.

FIG. 5Bshows reflection characteristics at incident angle α of 70°. The reflection characteristics show a relation between reflectance with respect to the incident light and wavelength of the incident light. In the first wavelength range, peak P2″ of the reflectance of S-wave component82included in the incident light has a wavelength of 500 nm, which is shorter than the lower-limit wavelength of the wavelength range of yellow light that ranges from 570 nm to 590 nm, inclusive. A wavelength range having a reflectance of 90% or more of peak P2″ of S-wave component82is from 410 nm to 580 nm, inclusive. A wavelength range having a reflectance of 80% or more of peak P2″ is from 390 nm to 610 nm, inclusive. That is, the upper-limit wavelength of the wavelength range having a reflectance of 90% or more of the peak value is shorter than 620 nm. In contrast, P-wave component84of the incident light has no reflectance peak in the first wavelength range. The characteristics above allows not only second S-wave component82bto have less yellow component but also second P-wave component84bto have less blue component.

As described above,FIG. 5AandFIG. 5Bshows the case in which the average reflectance of the first wavelength range is determined to 35%. Hereinafter, the characteristics further added to combiner30in the aforementioned case is described. As shown inFIG. 5A, the reflectance decreases in the wavelength range of blue light (ranging from 400 nm to 480 nm, inclusive) and in the wavelength range of red light (ranging from 620 nm to 700 nm, inclusive). Accordingly, a blue component and a red component of sunlight80easily pass through combiner30. Thus, the driver's eyes catch the light tinged with purple as a mixture of the blue and the red components from combiner30. At that time, it is preferable that the material of combiner30has an average transmittance in the wavelength range of green light (ranging from 495 nm to 570 nm, inclusive) is higher not only than an average transmittance of the wavelength range from 400 nm to 495 nm, inclusive, but also than the average transmittance of the wavelength range from 570 nm to 700 nm, inclusive. By virtue of the average transmittance above, the green component of sunlight80easily passes through combiner30as well. As a result, the driver's eyes catch white light as a mixture of the purple light and the green light. In this way, the light from combiner30is controlled so as not to be tinged with purple.

The average transmittance of at least reflecting surface32of combiner30in the wavelength range of green light (ranging from 495 nm to 570 nm, inclusive) may be higher not only than the average transmittance of the wavelength range from 400 nm to 495 nm, inclusive, but also than the average transmittance of the wavelength range from 570 nm to 700 nm, inclusive. By virtue of the average transmittance above, the green component of sunlight80easily passes through combiner30as well. As a result, the driver's eyes catch white light as a mixture of the purple light and the green light. In this way, the light from combiner30is controlled so as not to be tinged with purple.

As shown inFIG. 5A, light having a wavelength that belongs to the wavelength range of green light (ranging from 495 nm to 570 nm, inclusive) or the wavelength range of yellow light (ranging from 570 nm to 590 nm, inclusive) has an increased reflectance. As described earlier, the display light from display50comes into combiner30. Accordingly, an increased amount of the green component and the yellow component is contained in the display light reflected by combiner30, so that a green-yellow virtual image is seen by the driver. In such a green-yellow virtual image, blue color is weakened. Therefore, it is preferable that the intensity of the display light in the wavelength range of blue light ranging from 400 nm to 480 nm, inclusive, is increased. To be specific, display50outputs display light in which the light intensity is controlled as described above.

Combiner30having the characteristics shown inFIG. 5AandFIG. 5Bhas a base member made of an optical resin (ne=1.53). After the base member is injection-molded, a semi-transmitting film is formed on a surface of the base member as reflecting surface32. Hereinafter, the forming process of the semi-transmitting film is described in detail with reference toFIG. 5C.FIG. 5Cshows the structure of the semi-transmitting film of combiner30. In the description below, the reference wavelength is assumed to be 500 nm. The semi-transmitting film is a dielectric multilayer film having five layers. The five layers are formed by vacuum deposition with the following materials layered from the side of the base member: the first layer of SiO2with a film thickness of 191 nm; the second layer of Ta2O5with a film thickness of 53 nm; the third layer of SiO2with a film thickness of 91 nm; the fourth layer of Ta2O5with a film thickness of 52 nm; and the fifth layer of SiO2with a film thickness of 55 nm. Such structured semi-transmitting film has reflection characteristics at an incident angle of 0° shown inFIG. 5A. The reflection characteristics show an average reflectance of 35% in the first wavelength range. Further, the S-wave has a reflected color of white when incident light at an incident angle of 70° hits the semi-transmitting film according toFIG. 5B.

The semi-transmitting films ofFIG. 3C,FIG. 4C, andFIG. 5Chave similar layered structures of SiO2layers and Ta2O5layers but have different reflection characteristics. That is, changing the number of layers and the thickness of each layer allows the semi-transmitting film to have different reflection characteristics.

FIG. 3AandFIG. 5Ashow reflectance characteristic with respect to the incident light at an incident angle of 0°. Compared toFIG. 3A, the graph ofFIG. 5Ashows large difference in reflectance with respect to wavelength, and a clear peak in the visible wavelength range. Compared toFIG. 3A, the graph ofFIG. 4Ashows reflectance that starts to decrease from around 630 nm. According to the embodiment, the design of a semi-transmitting film puts weight on obtaining desired reflection characteristics at an incident angle of 70°, making some degree of sacrifice on reflection characteristics at an incident angle of 0°.

As described above, combiner30of the exemplary example has the structure in which, as for incident light at an incident angle of 0°, the upper-limit wavelength of the wavelength range having a reflectance of 90% or more of the peak value of reflectance is shorter than 700 nm; and as for incident light at an incident angle of 70°, the peak of the reflectance of S-wave component has a wavelength shorter than the lower-limit wavelength of the wavelength range of yellow light. The structure of combiner30allows the light having a wavelength shorter than yellow light to have increase in amount of reflection, which decreases reflection of yellow light. That is, decrease in reflection of yellow light means that reflection of colored light is decreased. As for incident light at an incident angle of 70°, the upper-limit wavelength of the wavelength range having a reflectance of 90% or more of the peak value of reflectance of the S-wave component is shorter than 620 nm, thereby decreasing yellow component contained in the reflected wave.

As for incident light at an incident angle of 0° of combiner30, the lower-limit wavelength of the wavelength range having a reflectance of 90% or more of the peak value of reflectance is longer than 460 nm, which narrows the wavelength range having a reflectance of 90% or more of the peak value of reflectance. This allows reflection characteristics at an incident angle of 70° to be changed. Besides, with the structure above, a green component contained in sunlight easily passes through combiner30. As a result, the driver's eyes catch white light as a mixture of the purple light and the green light. In this way, the light from combiner30is controlled so as not to be tinged with purple.

Further, at least on the reflecting surface of combiner30, the transmittance of a wavelength range of green light is set to be higher than the transmittance on the range lower than the wavelength range and the transmittance on the range upper than the wavelength range. As a result, the driver's eyes catch white light as a mixture of the purple light and the green light. In this way, the light from combiner30is controlled so as not to be tinged with purple. Enhancing intensity in the wavelength range of blue light in the display light allows a virtual image to have increase in blue color complementarily. This provides the virtual image with being less green-yellow.

So far, taking some examples, the structure of the embodiment has been described. These are merely examples, and it is apparent to those skilled in the art that changes and modifications may be made for combining components or processes without departing from the scope of the present disclosure.

In the examples, the first value is assumed to be 0° and the second value is assumed to be 70°. The first value means a reflection angle of the image of the HUD device when incident light comes from a direction confronting to the device; it practically ranges from 0° to 25°, inclusive, for example. The second value means a reflection angle when sunlight reflects on the HUD device disposed on a generally intended position; it practically ranges from 60° to 85°, inclusive, for example. In this way, the variation example of the embodiment allows combiner30to have flexibly determined characteristics.

Although the embodiment describes that combiner30is included in HUD device100, it is not limited to; combiner30may be separated from HUD device100. In that case, combiner30may receive the display light fed from the display of a smartphone. In this way, the variation example of the embodiment increases the degree of flexibility in structure.

According to the embodiment, combiner30is formed of a resin-molded member over which a reflection film having reflecting surface32is deposited; however, it is not limited to. A reflection film having reflecting surface32may be independently formed as a film, and then the film may be attached to the resin-molded member to form combiner30. In the structure above, the reflection characteristics of combiner30correspond to the reflection characteristics of the film. In this way, the variation example of the embodiment increases the degree of flexibility in structure.

An aspect of the present disclosure is outlined as follows. The combiner of the aspect of the present disclosure has a reflecting surface that reflects incident light and satisfies the two conditions below:

(1) when a first value is given to an incident angle that is defined as an angle formed between the normal line of the reflecting surface and incident light, in a first wavelength range from 400 nm to 700 nm, inclusive, the average value of reflectance of the incident light is 30% or greater, and the upper-limit wavelength of a second wavelength range having a reflectance of 90% or more of the reflectance peak of the incident light is shorter than 700 nm; and

(2) when a second value larger than the first value is given to the incident angle, in the wavelength range of visible light from 400 nm to 700 nm, inclusive, the reflectance peak of the S-wave component contained in the incident light has a wavelength shorter than 570 nm that corresponds the lower-limit value of the wavelength range of yellow light.

According to the aspect, when the incident angle takes the first value, the upper-limit wavelength of the second wavelength range is shorter than 700 nm; and when the incident angle takes the second value, the wavelength of the reflectance peak of the S-wave component is shorter than the lower-limit wavelength of the wavelength range of yellow light. Such structured combiner decreases reflection of colored light.

When the incident angle takes the second value, in the first wavelength range, the upper-limit wavelength of the wavelength range having a reflectance of 90% or more of the reflectance peak of the S-wave component included in incident light may be shorter than 650 nm. The aforementioned upper-limit wavelength is shorter than 650 nm; more exactly shorter than 620 nm, thereby decreasing a yellow component contained in the reflected light.

When the incident angle takes the first value, in the first wavelength range, the lower-limit wavelength of the wavelength range having a reflectance of 90% or more of the reflectance peak of incident light may be longer than 450 nm. The aforementioned lower-limit wavelength is longer than 450 nm; more exactly longer than 460 nm. This makes the wavelength range narrow, allowing the reflection characteristics at an incident angle of the second value to be changed.

The average transmittance of at least the reflecting surface of the combiner in the wavelength range that ranges from 495 nm to 570 nm, inclusive, may be greater than the average transmittance of the following two ranges: the wavelength range that ranges from 400 nm to 495 nm, inclusive; and the wavelength range that ranges from 570 nm to 700 nm, inclusive. In this case, a green component contained in sunlight easily passes through the combiner. As a result, the driver's eyes catch white light as a mixture of the purple light and the green light. In this way, the light from combiner30is controlled so as not to be tinged with purple.

In another aspect, the present disclosure provides a head-up display device. The device has a display that emits display light, a reflecting member that reflects the display light, and a combiner into which light reflected off the reflecting member is fed as incident light. The combiner has a reflecting surface that reflects the incident light, and it satisfies the following two conditions:

(1) when a first value is given to an incident angle that is defined as an angle formed between the normal line of the reflecting surface and incident light, in a first wavelength range from 400 nm to 700 nm, inclusive, the average value of reflectance of the incident light is 30% or greater, and the upper-limit wavelength of a second wavelength range having a reflectance of 90% or more of a reflectance peak of the incident light is shorter than 700 nm; and

(2) when a second value larger than the first value is given to the incident angle, in the first wavelength range, the reflectance peak of the S-wave component contained in the incident light has a wavelength shorter than 570 nm.

According to this aspect, when the incident angle takes the first value, the upper-limit wavelength of the second wavelength range is shorter than 700 nm. Besides, when the incident angle takes the second value, the reflectance peak of the S-wave component has a wavelength shorter than the lower-limit wavelength of the wavelength range of yellow light. The structure thus decreases reflection of colored light.

In display light, average intensity of light belonging to the wavelength range from 400 nm to 480 nm, inclusive, may be greater than average intensity of light belonging to the wavelength range from 480 nm to 700 nm, inclusive. In this case, intensity of the display light in the wavelength range of blue light is enhanced, allowing blue color in a virtual image to be added complementarily.

The display may be a single-colored segment LCD. This allows the display to have a simple structure.

The present disclosure relates to a combiner and is applicable to a combiner that reflects a part of incident light, and a head-up display device equipped with the combiner.