Interactive Projection Apparatus Ambient Light Interference
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Solution Overview
Problem
Current touch projection apparatuses face interference from ambient light, affecting the accuracy of touch position determination due to stray light sources.
Innovation Solution
An interactive projection apparatus with a projection unit, photosensitive unit, and control unit that projects a positioning pattern, calculates coordinate information, and defines an effective touch area to distinguish between valid and ambient light sources, using both visible and invisible light modes to sense and adjust the touch position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an infrared laser curtain is used to sense touch position, then touch detection capability is achieved, but ambient light interference affects measurement precision
Solution Approach 1:
The sensing area is segmented into multiple regions including a valid sensing area and an invalid sensing area. The valid sensing area corresponds to the projection area where touch input should occur, while the invalid sensing area corresponds to regions where ambient light may cause false detections. By segmenting the sensing area, the system can selectively process signals from different regions, accepting touches within the valid area while rejecting false signals from the invalid area, thus resolving the contradiction between achieving touch detection and avoiding ambient light interference.
Solution Approach 2:
A positioning pattern is introduced as an intermediary element to establish the relationship between the projection area and the sensing area. The positioning pattern consists of multiple positioning light spots that define the boundaries and characteristics of the valid sensing area. This intermediary positioning pattern allows the system to accurately identify which sensed light spots correspond to actual user touches versus ambient light interference, thereby improving measurement precision while maintaining the ability to detect ambient light conditions.
2Area of stationary object
If the sensing area covers the entire projection area, then complete touch coverage is achieved, but false detection from ambient light increases
Solution Approach 1:
The sensing area is divided into a valid sensing area and an invalid sensing area. The valid sensing area is positioned to coincide with the projection area where legitimate touch input occurs, while the invalid sensing area encompasses regions prone to ambient light interference. This segmentation enables the system to maintain comprehensive sensing coverage while selectively validating signals only from the valid area, thus preserving both coverage and reliability.
Solution Approach 2:
Different regions of the sensing area are assigned different functional qualities. The valid sensing area is configured with high sensitivity to detect user touches, while the invalid sensing area is either excluded from touch validation or monitored separately to identify ambient light patterns. This local differentiation of quality allows the system to optimize touch detection in critical areas while filtering out interference from other regions, maintaining overall system reliability.
3Measurement precision
If positioning pattern is projected to define effective touch area, then touch position accuracy is improved, but device complexity increases
Solution Approach 1:
The positioning pattern is projected in advance to pre-establish the valid sensing area boundaries before actual touch detection begins. This preliminary action defines the spatial relationship between the projection area and the sensing area, creating a reference framework that simplifies subsequent touch position calculations. By performing this setup action beforehand, the system avoids complex real-time calculations during touch events, thus improving accuracy without proportionally increasing operational complexity.
Solution Approach 2:
The positioning pattern creates an optical copy or representation of the projection area boundaries within the sensing space. Instead of requiring complex geometric calculations to map touch positions, the system uses the positioning light spots as direct optical references that define the valid sensing area. This copying approach simplifies the computational burden by providing pre-established spatial references, thereby improving measurement precision while minimizing the increase in device complexity.
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
Effectively avoids ambient light interference, ensuring accurate touch position determination and maintaining interactive operation quality by defining and adjusting the effective touch area based on coordinate information.
Implementation Method 1
a projection unit (102), a photosensitive unit (106) and a control unit (104). The projection unit (102) projects a positioning beam onto a surface F1 to form a positioning pattern on the surface F1
Implementation Method 2
the photosensitive unit (106) senses the positioning pattern in the sensing area A1
Implementation Method 3
When the user's finger or the stylus of a touch pen touches the screen, the light beam of the IR laser curtain would be reflected to an infrared sensor
Data Source
AI summary
An interactive projection apparatus and a touch position determining method thereof are provided. The invention adopts such a scheme of defining the effective touch area according to the coordinate information of the positioning pattern and judging whether or not the light spot is located in the effective touch area. If the light spot is located in the effective touch area, the position of the light spot is taken as the touch position of an input tool.