Prism-Based Optical Axis Alignment for Mobile Projectors
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Solution Overview
Problem
Current mobile devices face challenges in aligning the optical axes of projectors and cameras due to physical and technological limitations, where the projector's optical axis is typically aligned along the device's length, while the camera's optical axis is perpendicular, making it difficult to overlap the projection and viewing volumes effectively.
Innovation Solution
Incorporating a prism, such as a right-angle or pentaprism, within or outside the mobile device to reflect and align the projector's optical axis with the camera's axis, allowing for the overlap of projection and viewing volumes, and utilizing an integrated circuit to process captured images for activity detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the projector's optical axis is aligned along the length of the device body, then the projector can be integrated into the mobile device, but the optical axis cannot be aligned with the camera's optical axis which is perpendicular to the device length
Solution Approach 1:
A reflective surface (mirror or prism) is introduced as an intermediary component to redirect the optical path between the projector and camera. This mediator changes the direction of light propagation, enabling the optical axes to be aligned despite their perpendicular orientations in the device body, thereby resolving the alignment contradiction without increasing fundamental system complexity
Solution Approach 2:
The optical path is redirected by utilizing a different spatial dimension through the reflective surface. By reflecting light at an angle (typically 45 degrees), the system transitions from a direct linear optical path to a multi-dimensional path, allowing the projector and camera to share a common optical axis while maintaining their perpendicular mounting orientations
2Measurement precision
If a reflective surface is used to align the optical axes, then alignment accuracy is improved, but the system is exposed to dust and moisture affecting the reflective surface
Solution Approach 1:
The reflective surface is nested within a protective housing structure that seals it from the external environment. This nested configuration allows the reflective surface to maintain high alignment accuracy while being protected from dust and moisture contamination, as the housing creates a barrier between the sensitive optical component and harmful environmental factors
Solution Approach 2:
The reflective surface is extracted from the direct optical path environment and placed within a separate protected compartment. This extraction isolates the reflective surface from exposure to dust and moisture while maintaining its optical function, as the protective housing allows light to pass through while blocking environmental contaminants
3Manufacturing precision
If the projector length is increased to at least one centimeter, then projection quality is improved, but the device size increases
Solution Approach 1:
The increased projector length is accommodated by utilizing the longitudinal dimension of the device body, with the reflective surface positioned to fold the optical path back toward the camera. This dimensional arrangement allows a longer projector (≥1 cm) to be integrated without proportionally increasing the overall device footprint, as the optical path is redirected through the available internal space
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
This solution improves the alignment accuracy and reliability of the projector and camera axes, reducing signal loss and exposure to dust and moisture, while enhancing thermal stability and alignment precision, enabling effective image capture and processing for applications like computational photography and human-computer interaction.
Implementation Method 1
a prism that is configured with the mobile device to reflect the optical image by controlling the angle of the reflective surface, thereby aligning the optical axis of the projection unit
Data Source
AI summary
A system comprising: a handheld mobile device comprising: a projector unit configured to project an image; a camera; and a prism configured to reflect the image projected by the projector such that the camera can capture the projected image.