Head up display apparatus with a bright energy efficient backlight for a vehicle
A head up display apparatus for a vehicle includes an imaging unit that generates a projection light beam with display content and includes a transmissive display indication layer with selectively controllable display elements distributed over an area, a matrix backlight that provides backlighting therefor and includes selectively controllable light sources distributed along the transmissive display indication layer, and a collimation array with collimators arranged between a light source and the transmissive display indication layer, and a projection panel in the beam path of the projection light beam generated by the imaging unit for reflecting the projection light beam to a user, the projection panel being arranged in the beam path such that a virtual display image is generated therebehind in the visual field of the user.
1 . A head-up display apparatus comprising:
an imaging unit for generating a projection light beam with a display content, the imaging unit having a transmissive display layer with a plurality of selectively controllable display elements distributed in areal fashion, a matrix backlight configured for the backlighting of the transmissive display layer and having a plurality of selectively controllable light sources distributed along the transmissive display layer, and a collimation array with collimators arranged between a light source and the transmissive display layer; and
a projection screen arranged in a beam path of the projection light beam generated by the imaging unit, and configured to reflect the projection light beam toward a user, such that a virtual display image is generated behind the projection screen in the user's field of view, wherein:
each collimator is configured to focus a partial beam emanating from an associated light source in accordance with a predetermined emission characteristic for restricting the projection light beam reflected to the user to a spatial region predetermined for the user's eyes,
the entire collimation array is configured to be laterally displaceable relative to a plane or an area of the matrix backlight in which the light sources are arranged,
the collimators are movable relative to the light sources, and
the head-up display apparatus further comprises a control unit configured to track the collimators and thus predetermined emission characteristics of the projection light beam to a current user position ascertained by eye tracking to an eye position or viewing direction.
2 . The head-up display apparatus according to claim 1 , wherein the light sources are distributed substantially uniformly along the transmission display layer.
3 . The head-up display apparatus according to claim 1 , wherein each light source is arranged at or close to a focal point or in or close to a focal plane of an associated optical collimator, such that a divergent partial beam emitted by the light source is collimated to form a largely parallel partial beam with a predetermined small aperture angle of approximately +/−5°, and a propagation direction that varies from a first light source to a second light source in accordance with the respective predetermined emission characteristic.
4 . The head-up display apparatus according to claim 1 , wherein the eye tracking is performed by laterally displacing the collimation array along the matrix backlight.
5 . The head-up display apparatus according to claim 1 , wherein a distance between the matrix backlight and the collimation array in a beam propagation direction is mechanically adjustable for changing the predetermined emission characteristics, thereby switching between a private mode provided for a single user, in which only a predetermined spatial region provided for the single user's eyes is illuminated by the projection light beam, and a shared mode provided for a plurality of users, in which a predetermined spatial region provided for eyes of the plurality of users is illuminated by the projection light beam.
6 . The head-up display apparatus according to claim 1 , wherein:
the light sources of the matrix backlight are configured to be dimmable independently of one another, and
the head-up display apparatus further comprises a first control unit configured to dim the light sources of the matrix backlight independently of one another in accordance with a first predetermined correction function for increasing a brightness homogeneity in the virtual display image and/or for situation-dictated brightness adaptation of the matrix backlight in an area, and/or
the head-up display apparatus further comprises a second control unit configured, during generation of display contents to be represented, to take account of brightness values of the display elements of the transmissive display layer independently of one another in accordance with a second predetermined correction function for increasing the brightness homogeneity in the virtual display image in the area.
7 . The head-up display apparatus according to claim 6 , wherein the light sources of the matrix backlight are configured to be dimmable by use of potentiometers and/or by temporal pulsing with a specific ratio of bright and dark times within a period not discernible as an individual image by a human eye.
8 . The head-up display apparatus according to claim 7 , wherein the period is less than 20 ms.
9 . The head-up display apparatus according to claim 1 , wherein the imaging unit comprises optical diffusers for increasing a brightness homogeneity in the virtual display image, and the optical diffusers are arranged in a beam path of a partial beam of a light source between the light source and an associated collimator and/or between the associated collimator and the transmissive display layer.
10 . The head-up display apparatus according to claim 9 , wherein the optical diffusers are arranged symmetrically about a propagation direction of the partial beam.
11 . The head-up display apparatus according to claim 9 , wherein the optical diffusers have a radially symmetrical diffusion and/or transmission characteristic about a respective propagation direction of the partial beam.
12 . The head-up display apparatus according to claim 1 , further comprising:
a reflection-suppressing arrangement arranged on the imaging unit, wherein the reflection-suppressing arrangement is configurable as a deflection arrangement with one or more planar reflection areas extending along the transmissive display layer at a predetermined acute angle thereto, wherein the reflection areas are configured and arranged to direct the projection light beam onto the projection screen for generating the virtual display image behind the projection screen in the user's field of view and are configured to be light-absorbing on rear sides for suppression of disturbing reflections; and/or
additional optical deflecting elements in a beam path of the projection light beam between the display area and the projection screen, such that only predetermined partial sections of the display area can contribute to the virtual display image.
13 . The head-up display apparatus according to claim 12 , wherein the reflection-suppressing arrangement is arranged directly on a reflection area of the imaging unit formed by the transmissive display layer.
14 . The head-up display apparatus according to claim 12 , wherein:
the transmissive display layer has display elements only in partial sections and/or mutually spaced apart strips assigned to the individual reflection areas of the reflection-suppressing deflection arrangement, from which strips and/or partial sections emanating projection light is incident on the projection screen as a result of deflection at the reflection areas and/or the additional optical deflecting elements, and/or
the matrix backlight has light sources only in partial sections and/or mutually spaced apart strips assigned to the individual reflection areas of the reflection-suppressing deflection arrangement, from which strips and/or partial sections emanating projection light is incident on the projection screen as a result of deflection at the reflection areas and/or the additional optical deflecting elements.
15 . The head-up display apparatus according to claim 12 , wherein at least one of the reflection areas of the reflection-suppressing deflection arrangement is formed by a lateral surface side of a prism arranged on the imaging unit.
16 . The head-up display apparatus according to claim 15 , wherein the lateral surface side at the prism has a triangular, quadrilateral, trapezoidal, or pentagonal cross-sectional area.
17 . The head-up display apparatus according to claim 12 , wherein:
the light sources of the matrix backlight are configured to be dimmable independently of one another, and
the head-up display apparatus further comprises a first control unit configured to dim the light sources of the matrix backlight independently of one another in accordance with a first predetermined correction function for increasing a brightness homogeneity in the virtual display image and/or for situation-dictated brightness adaptation of the matrix backlight in an area, and/or
the head-up display apparatus further comprises a second control unit configured, during generation of display contents to be represented, to take account of brightness values of the display elements of the transmissive display layer independently of one another in accordance with a second predetermined correction function for increasing the brightness homogeneity in the virtual display image in the area, and
the first control unit and/or the second control unit is configurable to increase a brightness homogeneity in image sections of the virtual display image which are deflected in an edge region of a reflection area or at a transition between individual reflection areas of the reflection-suppressing deflection arrangement.
18 . A vehicle comprising:
a windshield;
an instrument panel arranged under the windshield; and
the head-up display apparatus according to claim 1 , wherein the projection screen is formed by the windshield and the imaging unit and/or the reflection-suppressing arrangement are arranged on or in a top side of the instrument panel, in a manner terminating flush with the latter, for inserting the virtual display image into the user's field of view as the user looks through the windshield, wherein the user is a driver of the vehicle.