Projector Keystone Correction Using Distance and Gravity Sensors
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Solution Overview
Problem
Conventional methods for keystone correction in projectors, particularly ultra short throw beam projectors, face challenges in precise angle measurement due to the close proximity of the projection surface, requiring wide-angle cameras and leading to increased errors in calibration and warping, especially when small distortions result in significant image warping.
Innovation Solution
An electronic apparatus utilizing a plurality of distance sensors arranged to face one another on its surface, along with an acceleration sensor, calculates rotation angles for keystone correction by determining the direction of gravity and the projection surface, enabling precise measurement without the need for separate image sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an image sensor (camera) is used to calculate the yaw angle for keystone correction, then the projector can determine the projection surface orientation, but calibration errors significantly affect the angle calculation accuracy
Solution Approach 1:
The patent replaces the optical/image-based measurement system with an acceleration sensor-based mechanical sensing system. Instead of using an image sensor to capture and analyze projection surface images for angle calculation, the system uses acceleration sensors to directly measure the projector's tilt angles (pitch and roll) relative to gravity, and combines this with geometric calculations from distance sensors to determine the yaw angle. This substitution eliminates calibration requirements and reduces sensitivity to calibration errors.
Solution Approach 2:
The patent changes the measurement parameters from image-based optical measurements to acceleration-based physical measurements. By measuring acceleration components along three orthogonal axes and deriving rotation angles from these physical quantities, the system achieves more reliable angle measurement that is not dependent on optical calibration. The system calculates pitch angle from acceleration components, roll angle from acceleration components, and derives yaw angle from the combination of distance measurements and the first two rotation angles.
2Area of stationary object
If a wide-angle lens camera is used in ultra short throw beam projectors to view the entire screen from close distance, then the projection surface can be detected, but warping becomes severe and calibration becomes difficult leading to increased errors
Solution Approach 1:
The patent replaces the wide-angle camera system with a combination of acceleration sensors and distance sensors. Instead of capturing a wide-angle image of the entire screen from close distance (which causes severe warping), the system uses acceleration sensors to measure the projector's orientation angles and distance sensors to measure the distance to the projection surface. This mechanical sensing approach avoids the warping problem entirely while providing sufficient information for keystone correction.
Solution Approach 2:
The patent segments the measurement function into multiple independent sensors: acceleration sensors for measuring tilt angles (pitch and roll), distance sensors for measuring the distance to the projection surface, and computational processing to derive the yaw angle. This segmentation allows each sensor to perform its specialized function optimally without the compromises required by a single wide-angle camera system, thereby improving overall measurement precision.
3Measurement precision
If an image sensor is used for keystone correction, then the projection surface can be analyzed, but a great amount of calculation is required
Solution Approach 1:
The patent replaces complex image processing calculations with simpler acceleration-based angle measurements. Instead of capturing images, detecting edges, finding contours, and performing complex geometric analysis, the system directly measures acceleration components and calculates rotation angles using straightforward trigonometric relationships. This mechanical measurement approach dramatically reduces computational requirements while maintaining measurement precision.
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 allows for precise keystone correction by accurately measuring rotation angles, even in narrow spaces, improving the accuracy of image projection and reducing errors associated with conventional methods.
Implementation Method 1
calculate a first rotation angle and a second rotation angle for the direction of gravity of the electronic apparatus based on sensing values acquired by using the acceleration sensor
Implementation Method 2
calculate a third rotation angle of the electronic apparatus for the projection surface based on sensing values acquired by using the plurality of distance sensors
Data Source
AI summary
An electronic apparatus includes a projection part, an acceleration sensor, a plurality of distance sensors arranged on one surface of the electronic apparatus facing a projection surface, a memory storing at least one instruction, and a processor, wherein the plurality of distance sensors are arranged side by side on left and right sides on one surface of the electronic apparatus, and are arranged to be rotated by a first angle to face one another, and the processor is configured to calculate a first rotation angle and a second rotation angle for the direction of gravity of the electronic apparatus based on sensing values acquired by using the acceleration sensor, calculate a third rotation angle of the electronic apparatus for the projection surface based on sensing values acquired by using the plurality of distance sensors and the first angle, and perform keystone correction based on the first to third rotation angles.