Head-Up Display Screen Positioning via Voice Coil Motor and Phase Correction
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Solution Overview
Problem
Head-up displays in vehicles face challenges in synchronizing the movement of a screen with the formation of images due to low responsiveness of actuators, leading to delays and inappropriate viewing distances for drivers.
Innovation Solution
An image display device and driving device that incorporate a position detector and a servo circuit with a correction circuit to synchronize the movement of the screen with the image formation, reducing timing deviations and ensuring proper viewing distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a motor, feed screw, and rack are used to drive the screen, then the device structure is simple and reliable, but the screen cannot be moved at high speed and images whose viewing distance changes cannot be smoothly displayed
Solution Approach 1:
The patent replaces the traditional mechanical drive system (motor, feed screw, rack) with a VCM (Voice Coil Motor) based drive mechanism. This substitution enables high-speed screen movement while maintaining system reliability, as the VCM can rapidly adjust screen position in the optical axis direction to display images with changing viewing distances.
Solution Approach 2:
The patent implements dynamic control of the screen position by using servo control to follow a target position waveform. The screen position is continuously adjusted in real-time to match the desired viewing distance changes, enabling smooth display of images whose viewing distance varies over time.
2Manufacturing precision
If servo control is performed such that the screen position follows a target position waveform, then the screen can be moved at high speed, but the actual screen position follows the target position with a predetermined time lag causing inappropriate viewing distance
Solution Approach 1:
The patent applies preliminary action by advancing the phase of the target position waveform ahead of the actual screen position. This phase advance compensates for the inherent time lag in the servo system, ensuring that the screen reaches the desired position at the correct time for proper image display at the intended viewing distance.
Solution Approach 2:
The patent uses feedback from a position detector to continuously monitor the actual screen position and adjust the drive signal accordingly. This closed-loop control enables real-time compensation for position deviations and time lags, improving the accuracy of screen position following the target waveform.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables stable and synchronized image display at appropriate viewing distances, reducing delays and improving the overall performance of head-up displays in vehicles.
Implementation Method 1
an actuator configured to move the screen in an optical axis direction
Implementation Method 2
a position detector configured to detect a movement position of the screen
Implementation Method 3
an optical system configured to generate a virtual image by light from the screen
Implementation Method 4
light modulated by image information is projected toward a windshield, and the reflected light is applied to the eyes of a driver
Data Source
AI summary
An image display device includes: a light source; a screen on which an image is formed when light from the light source is applied thereto; an optical system configured to generate a virtual image by light from the screen; an actuator configured to move the screen in an optical axis direction; a position detector configured to detect a movement position of the screen; a servo circuit configured to cause the movement of the screen by the actuator to follow a target waveform on the basis of a signal from the position detector; and a correction circuit configured to reduce a deviation between a timing to move the screen by the servo circuit and a timing to form the image on the screen.