Projector Touch Detection Using Brightness and Position Thresholds
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Solution Overview
Problem
Interactive projectors face false touch detection issues due to fluctuations in reflected light and bright point positions when a pointer touches or approaches a display surface, leading to the display of extra lines at the start and end of drawing operations.
Innovation Solution
A display method and system that capture images before and during drawing, analyzing brightness values and positions of bright points to determine accurate touch detection, avoiding the display of extra lines by adjusting the display image based on specific brightness and position thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If touch detection is performed by detecting reflected light from a pointer, then touch detection capability is enabled, but false touch detection occurs due to fluctuations in reflected light and bright point position
Solution Approach 1:
The system performs preliminary actions by capturing a first image before the drawing operation and a second image during the drawing operation. It calculates the position and brightness of bright points in both images, then uses these preliminary measurements to determine whether to display the drawn line, thereby preventing false detection before it occurs.
Solution Approach 2:
The system implements feedback by comparing the bright point position and brightness from the first captured image with those from the second captured image. Based on this comparison feedback, the system determines whether the pointer is actually touching the display surface or merely approaching it, thereby correcting false detection issues.
2Ease of operation
If the system displays drawn lines based on bright point detection, then drawing functionality is provided, but extra lines are displayed at the start and end of drawing operations
Solution Approach 1:
The system captures a first image before the drawing operation begins and stores the bright point position and brightness as reference values. This preliminary capture allows the system to distinguish between the approach phase (before touching) and the actual drawing phase, preventing extra lines from being displayed at the start of drawing operations.
Solution Approach 2:
The system continuously compares the bright point position and brightness in the second captured image with the reference values from the first image. This feedback mechanism allows the system to accurately determine when the pointer has actually touched the display surface and when it has moved away, thereby preventing extra lines from being displayed at the end of drawing operations.
3Measurement precision
If the pointer approaches the display surface without touching, then the system can detect the approach, but false touch detection occurs when the bright point position fluctuates
Solution Approach 1:
The system uses feedback by comparing both the position and brightness of the bright point in the first captured image with those in the second captured image. This dual-parameter feedback allows the system to distinguish between pointer approach (where brightness changes but position remains relatively stable) and actual touch (where both position and brightness change significantly), thereby preventing false touch detection.
Solution Approach 2:
The system applies parameter changes by using both position coordinates and brightness values as detection parameters. By monitoring changes in both parameters simultaneously and comparing them between the first and second captured images, the system can more accurately determine actual touch events versus mere approach, resolving the false detection issue.
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
Accurately detects touch events and prevents the display of extra lines at the start and end of drawing operations, enhancing the precision of touch detection and user experience.
Implementation Method 1
acquiring a first brightness value indicating brightness of a first bright point contained in the first captured image by a reflected light from a pointer
Data Source
AI summary
A projector includes a first acquisition unit, a second acquisition unit, a first determination unit, and a display control unit. The first acquisition unit sequentially acquires a first captured image and a second captured image on a display surface. The second acquisition unit acquires a first brightness value and a first position of a bright point contained in the first captured image and a second brightness value and a second position of a bright point contained in the second captured image. The first determination unit determines whether the second brightness value is larger than the first brightness value by a first threshold or more and the second position is closer to a camera than the first position. The display control unit displays a display image containing a drawn image showing a drawn line by a pointer when a determination result is negative, and displays a display image not containing the drawn image when the determination result is positive.