Projection Apparatus Autofocus Using Optical-Axis Imaging
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Solution Overview
Problem
Existing projection apparatuses face challenges in achieving autofocus for a wide projection range without increasing size or cost, and methods like laser-based distance measurement are inadequate for handling projection image position changes.
Innovation Solution
The projection apparatus employs an imaging unit to capture a region near the optical axis, using a processor to control focus adjustment on the wider projection image based on acquired information, with conditional expressions to ensure a deep depth of field and efficient focus adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an imaging unit captures the entire projection image for autofocus, then the autofocus coverage is complete, but the apparatus size and cost increase
Solution Approach 1:
The projection image is divided into two regions: a first region including the optical axis position that is captured by the imaging unit, and a second region closer to the edge that uses different focus adjustment. This segmentation allows the imaging unit to be smaller while still achieving effective autofocus coverage for the entire projection image.
Solution Approach 2:
Different focus adjustment methods are applied to different regions of the projection image. The first region (center) uses autofocus based on imaging unit capture, while the second region (edge) uses alternative focus adjustment, optimizing both coverage and apparatus size.
2Area of stationary object
If the projection optical system has a wide angle of view for large projection, then the projection coverage increases, but the depth of field decreases making focus adjustment difficult
Solution Approach 1:
The projection image is divided into a first region including the optical axis and a second region closer to the edge. The imaging unit captures the first region to determine focus, while the second region receives focus adjustment based on this information, enabling precise focus control across the entire wide-angle projection image.
Solution Approach 2:
Different focus adjustment strategies are applied to different regions: the first region (center) serves as the reference for focus determination, while the second region (edge) receives compensatory focus adjustment to ensure uniform sharpness across the entire wide projection image.
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 approach allows for autofocus over a wide range while maintaining a compact size and low cost, ensuring almost the entire projection image remains in focus despite distance changes.
Implementation Method 1
an imaging optical system which images a first region including an optical axis of the projection optical system in the projection image
Implementation Method 2
a projection optical system that forms a projection image by projecting the image
Data Source
AI summary
A projection apparatus includes a display element that displays an image, a projection optical system that forms a projection image by projecting the image, an imaging unit that includes an imaging optical system which images a first region including an optical axis of the projection optical system in the projection image, and an imaging element which captures an image formed by the imaging optical system, and a processor that controls focus adjustment on a second region not including the optical axis in the projection image based on information acquired from the imaging unit, in which a position of the projection image is changeable by changing a relative position between at least a part of the projection optical system and the display element, and a predetermined conditional expression is satisfied.