Patent Application
20190361237
The present disclosure relates to a head-up display device for a vehicle, primarily in the context of a motor vehicle such as an automobile but also in the context of an aircraft or watercraft.
Various heads-up display devices are generally known for displaying information to a user, in particular a vehicle driver, on a transparent panel such as a windshield of the vehicle. If the vehicle, the head-up display device, or its holder vibrates due to certain operating conditions such as certain vehicle speeds or engine speeds, the projected image may also vibrate and thus appear blurred in the user's field of view. Apart from the fact that the recognizability or readability of the information is impacted, this can lead to a negative psychological and/or physiological effect for the viewer. For example, a vehicle driver may be irritated and/or distracted, may fatigue more quickly, or even feel nauseous.
Accordingly, there is a need in the art to reduce or prevent the effects of vibrating image projections.
The present disclosure recognizes fact that engine vibrations or external excitations such as air currents may excite the vehicle or parts of the vehicle at or near a resonant frequency, typically in the range from 30 to 120 Hz, which induces vibrations. Such vibrations can have a direct or indirect effect on the head-up display device, with the result that the projected image which is generated and projected onto the windshield or another projection surface vibrates at the excitation frequency of these vibrations. The present disclosure further recognizes that the most objectionable vibrations of the projection image are vertically oriented, but may, to a lesser extent include lateral or longitudinal directions depending on local conditions. Perception of these vibrations by the viewer may be significantly reduced by periodically and/or cyclically switching the generated projected image on and off at the excitation frequency, or a multiple thereof.
Accordingly, the present disclosure provides a solution to the undesirable vibration of image projections in a head-up display including a control unit configured to stroboscopically display the projected image at a control frequency fA as a function of an excitation frequency fE. In order to affect a stroboscopic display, the control unit is also configured to determine the excitation frequency and the control frequency. As a result, the projected image is projected at the same position according to the determined excitation frequency and otherwise turned off so that it appears to in the user's field of view as a stationary image that does not vibrate, thereby preventing the above-noted impairments for the viewer of the projected information. According to the present disclosure, the projected image is thus turned off over large portions of the vibration amplitude, and is only switched on (i.e., projected or displayed) during short pulses or phases, such that the subjective impression of a stationary projected image is created. The switched-on duration may be the repetition rate of the PWM signal having a control frequency fA corresponding to the excitation frequency fE. The control frequency fA of the PWM signal is a function of the excitation frequency fE or as expressed in an equation: fA=n·fE, where n=i or 1/i and i is a whole number (e.g., i=1, 2, 3, 4, . . . ).
According to an embodiment of the present disclosure, at least one sensor, typically configured as an accelerometer, measures a vibration response of the vehicle or a part thereof. The sensor may be configured to measure the vibration response for a component of the head-up display device for directly detecting the vibrations of the device itself as precisely as possible. Alternatively, one or more sensors which are present for other purposes can also be used for indirectly detecting the vibrations of the display device, in which case a transfer function is used to correlated the measured vibration with the vibration behavior at the head-up display device to arrive at a determined vibration.
According to an embodiment of the present disclosure, the device according to the present disclosure includes at least one data table having control data stored therein for driving conditions such as a driving speed, an engine speed or a combination thereof. This embodiment eliminates the use of a sensor for measuring a vibration response and has been found to be effective when there is a strong correlation between a driving state and the vibration behavior of the display device for a particular head-up display device in the vehicle. In this embodiment, a look-up function can be implemented with the data table to determine a transfer function or frequency response function to correlate the driving state with the vibration behavior at the head-up display device and arrive at a determined vibration. The data stored in the table preferably includes the excitation frequency and amplitude present in each driving state for determining the transfer function.
According to an embodiment of the present disclosure, the device is configured to switch on the projection device at a vibration extreme (maximum or minimum), and to otherwise switch it off. This approach takes into account the fact that, at the vibration maxima or minima, the rate of change in movement of the projected image is less pronounced than in the other vibration regions, and therefore the projection device can remain activated for a longer duration, therefore achieving a higher luminance such that the projected image appears brighter. In such a case, the excitation frequency fE and the phase position for a determined vibration, as well as the sampling rate of the PWM signal are determined. The phasing of the PWM signal is such that the projection device is switched on at a vibration extreme based on the phase position of the determined vibration. As an alternative to the activation of the projection device at the extremes, it is possible to use two shorter activation periods with the same amplitude value within a vibration period.
The term ‘determined vibrations’ in this context can mean directly-measured vibrations, or data calculated or stored in tabular form on the basis of other driving state data.
According to an embodiment of the present disclosure, the device according to the present disclosure is connected to external sensors for determining the vibrations. In this way, the structural complexity for the device according to the present disclosure is reduced, since such sensors are already regularly present in a vehicle.
The present disclosure also provides a motor vehicle which includes a head-up display device according to one of the embodiments described above. The present disclosure further provides a method for operating a head-up display device for a vehicle, having a projection device for projecting information onto a projection surface of the vehicle. The projection device is controlled by pulse width modulation (PWM) with a control frequency fA. An excitation frequency fE of the head-up display device is determined and the control frequency fA is adjusted according to the determined excitation frequency fE.
Further advantages, features and details emerge from the following description, in which at least one exemplary embodiment is described in detail, with reference to the drawings. Identical, similar and/or functionally identical parts are indicated by the same reference numbers.
The present disclosure will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements.
The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description.
The control unit 17 controls the illumination intensity of the projection device 14 by means of the PWM signal with a phase position, such that, in the embodiment shown, the projected image is projected onto the windshield 18 about the vibration maxima 30, whereas the projected image 16 remains off in the intervening periods. In this way, the effective vibration amplitude 32 of the display image 16 is considerably reduced, and appears to the viewer essentially as a stationary image.
Alternatively or in addition to the vibration sensor 24, in the illustrated embodiment, a driving state data generator 26 is included which supplies data, such as the vehicle speed or the engine speed, to the control unit 17. The control unit 17 in this case contains a stored table 34 in which vibration values of the projection device 14 with respect to the frequency and amplitude determined by previous vehicle type-specific tests are stored for this driving state data. This makes it possible to control the projected image 16 in the manner according to the present disclosure, even without a vibration sensor.
While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims and their legal equivalents.
