Projection Display Detecting Finger Input Using Structured Light
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Solution Overview
Problem
Existing projection video display systems struggle to accurately detect finger operations due to external light interference, leading to false recognition and non-detection of user inputs.
Innovation Solution
A projection video display apparatus equipped with a projection unit, image capture unit, and operable region specifying unit that distinguishes between detectable and undetectable regions on a projection surface based on image data, adjusting the display to ensure operations are only performed within detectable areas and guiding users to improve their environment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If shadow-based finger detection is used, then finger operation can be detected without special equipment, but detection accuracy deteriorates under external light influence
Solution Approach 1:
The patent introduces a structured light pattern (laser line or grid pattern) as an intermediary carrier to encode position information. Instead of relying solely on shadow shapes that are vulnerable to external light, the structured light serves as a stable reference framework that the imaging device can track accurately even in varying ambient conditions. The finger position is detected by analyzing the distortion or occlusion of this structured light pattern rather than relying on shadow alone.
Solution Approach 2:
The patent changes the detection parameter from shadow shape analysis to structured light pattern analysis. By projecting a known light pattern and analyzing its interaction with the finger (occlusion, reflection, or distortion), the system transforms the detection problem into one that is less sensitive to ambient light conditions. The structured light provides a controlled optical field whose parameters (intensity, pattern geometry) can be optimized for detection reliability.
2Illumination intensity
If illumination is increased to improve shadow detection, then finger operation becomes more detectable, but external light interference increases
Solution Approach 1:
The patent employs dynamic temporal modulation of the structured light projection and synchronized gating of the imaging device. The structured light is projected in pulses or sequences, and the imaging device captures images only during specific time windows when the structured light is active. This temporal dynamics allows the system to distinguish between the controlled structured light and ambient external light, effectively rejecting the harmful external light interference while maintaining sufficient illumination for detection.
Solution Approach 2:
The system uses periodic projection of structured light patterns at specific frequencies. By modulating the structured light at a known frequency and using synchronous detection or frequency-based filtering in the image processing, the system can distinguish the structured light signal from ambient light noise. This periodic action creates a temporal signature that separates the useful illumination from harmful external light interference.
3Device complexity
If shadow-based detection is used in bright environments, then device simplicity is maintained, but operability is lost in undetectable regions
Solution Approach 1:
The patent makes the projection unit serve multiple functions: it both displays the video content and projects the structured light pattern for finger detection. The same projector hardware is used to create both the visual display and the detection framework, eliminating the need for separate illumination devices or sensors. This multi-functionality maintains device simplicity while enabling reliable operation detection across the entire projection surface area, even in bright environments where traditional shadow detection would fail.
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
Enhances user convenience by accurately detecting finger operations and preventing false recognition, allowing users to improve their usage environment and maintain operability even under external light interference.
Implementation Method 1
an operation detection apparatus used together with illumination means and image capture means, the apparatus including: means for causing the image capture means to capture an operator with the operator illuminated by the illumination means
Implementation Method 2
means for extracting a portion of a shadow from the detected region of the specific part of the operator
Data Source
AI summary
An operation target device projects a display video onto a projection surface, which is captured by a camera. An operation detectable region specifying unit specifies respective regions where an operation is detectable and is undetectable in a range in which the display video is projected, based on image data captured by the camera. Finger and pen contact position detection units detect the operation to the operation object based on the image data. The operation target device displays the display video so that the region where the operation to the operation object is detectable, which is specified by the operation detectable region specifying unit, is distinguished from the region where the operation to the operation object is undetectable. The operation target device changes a display position of the operation object so the operation object is displayed within a range of the region where the operation to the operation object is detectable.