A head up display apparatus includes: an image display apparatus having a light source and a display element and forming an image; an image-light projecting means displaying a virtual image onto a forward part of a vehicle by projecting the image light emitted from the image display apparatus to be reflected on a windshield 3; and a point-of-view detecting system 6 sensing a point of view of the driver. In the head up display apparatus, the image-light projecting means includes a means generating illumination light entirely made of single-color visible light emitted to a face of the driver in a predetermined state of the vehicle.

A circuit device 100 includes an error detection circuit 110 and a processing circuit 120. The error detection circuit 110 obtains a glare index value, which is an index value indicating glare of a head-up display, based on image data IMD for head-up display. The error detection circuit 110 determines whether or not a glare index value has exceeded a first threshold value, and when the glare index value exceeds the first threshold value, detects occurrence of a first glare error. When occurrence of a first glare error is detected, the processing circuit 120 performs processing corresponding to the first glare error.

A head-up display includes a display panel, a reflective optical element, a controller, and an obtainer. The display panel displays a first image. The reflective optical element reflects image light from the first image displayed by the display panel. The controller controls a position at which the first image is displayed on the display panel. The obtainer obtains, as positional information, a position of an eye of a user. The controller changes the position at which the first image is displayed on the display panel in accordance with the positional information.

A head-up display is mountable on a movable body, and includes a first display panel, a reflective optical element, and an optical member. The first display panel displays a first image. The reflective optical element at least partially reflects image light from the first image displayed by the first display panel toward a user of the movable body. The optical member is between the display panel and the reflective optical element and is light transmissive. The display panel includes a surface facing a surface of the optical member. Each of the surface of the display panel and the surface of the optical member includes a reflection reduction layer to reduce light reflection.

A head-up display system includes a first projection module that projects a first image to display the first image in a forward direction not directly facing a user, a second projection module that projects a second image to display the second image in a forward direction directly facing the user, and a reflective optical element that reflects at least a part of the first image and at least a part of the second image.

A display device includes a cover, a display, and a polarization reflection layer. The cover transmits visible light. The display displays an image. The polarization reflection layer is disposed between the cover and the display and on a surface of the display. The polarization reflection layer reflects part of light incident through the cover and transmits light of the image displayed by the display.

A vehicle display device includes a display that emits a display image to be projected onto a windshield provided to a vehicle, as display light, at least one reflecting mirror that is disposed on an optical path of the display light from the display to the windshield and reflects the display light, an optical sensor that detects external light (SL) incident from an opening through which an outside and an internal space are communicated with each other, a temperature sensor that detects a temperature of the display, a dimming member that is disposed on the optical path of the display light, and a controller that causes the dimming member to be switched between a state with a first transmissivity and a state with a second transmissivity smaller than the first transmissivity.

A head-up display system includes a first projection module, a second projection module, and a first reflective optical element. The first projection module projects a first image. The second projection module projects a second image. The first reflective optical element reflects at least a part of the first image and at least a part of the second image. The first projection module includes a first display panel that displays the first image and projects the first image toward the first reflective optical element. The second projection module includes a second display panel that displays the second image, and an optical system that directs the second image toward the first reflective optical element.

A head up display system presents a virtual image to a human driver of a motor vehicle. A picture generation unit includes a printed circuit board having at least one light emitting device emitting light from a surface of the printed circuit board. The surface has an optically reflective coating. A liquid crystal display receives the emitted light and reflects a portion of the received emitted light back to the printed circuit board. The optically reflective coating of the printed circuit board reflects the light reflected by the liquid crystal display back to the liquid crystal display. At least one mirror reflects light passed by the liquid crystal display toward a windshield of the motor vehicle such that the light is reflected by the windshield and is visible to the human driver as the virtual image.

There are provided a reflection film, a windshield glass, and a head-up display system capable of suppressing formation of double images of a display image. The reflection film has a linearly polarized light reflection layer in which optically anisotropic layers and isotropic layers are laminated and a polarization converting layer, and the polarization converting layer satisfies any of conditions below. (A) The polarization converting layer is a retardation layer in which the front retardation is 30 nm to 200 nm and the angle between a slow axis direction and a direction of the transmission axis of the linearly polarized light reflection layer is 35° or less. (B) The polarization converting layer is a layer in which a helical alignment structure of a liquid crystal compound is fixed, and the number of pitches x in the helical alignment structure and the film thickness y (unit .Math.m) of the polarization converting layer satisfy all relational expressions below.

$0.1\le \text{x}\le \text{1}\text{.0}$

$0.5\le \text{y}\le \text{3}\text{.0}$

$3000\le (1560\times \text{y)/x}\le \text{50000}$