Projection Device Auto Focus Using Distance Sensor and Transfer Function
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Solution Overview
Problem
Conventional auto focus methods in projection devices face challenges such as fixed focus adjustment parameters, high computational requirements, slow response times, and image quality issues due to temperature changes affecting the projection lens structure, limiting optimal focus adjustment across varying projection distances.
Innovation Solution
A projection device and auto focus method that utilize a distance sensor, focus adjustment module, and control unit to calculate focus adjustment parameters using an auto focus transfer function, allowing for dynamic adjustment of the projection lens focal length to maintain optimal image clarity, with the ability to calibrate and correct focus deviations based on user feedback and temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If auto focus by ranging technique is used, then focus adjustment can be performed based on projection distance, but the focus adjustment parameters are fixed and cannot be adjusted by users, causing inability to achieve optimal focus when image clarity issues occur
Solution Approach 1:
The patent transforms the fixed lookup table into a dynamic calibration system. The control unit stores multiple sets of correspondence relationships between projection distances and focus adjustment parameters, and can dynamically select and update these parameters based on actual usage conditions and user feedback, making the system adaptable rather than static.
Solution Approach 2:
The patent introduces a feedback mechanism where user feedback on image clarity is received and used to update the focus adjustment parameters. The control unit adjusts the parameters based on this feedback, creating a closed-loop system that continuously improves focus accuracy according to actual performance.
2Measurement precision
If auto focus by camera technique is used, then focus can be adjusted based on image processing, but the system requires high computational power and has slow response speed
Solution Approach 1:
The patent replaces the complex image processing system with a simpler optical detection system. Instead of using a camera to capture and process images, the invention uses a detection component to directly detect focus status, significantly reducing computational requirements while maintaining focus accuracy.
Solution Approach 2:
The patent extracts only the essential focus detection function from the complex image processing system. By using a dedicated detection component rather than a full camera system, it isolates and performs only the necessary focus measurement task, eliminating unnecessary computational overhead.
3Duration of action of stationary object
If projection lens is used for long term, then temperature rises causing structure change, but this results in unclear projection image focus when object distance changes
Solution Approach 1:
The patent introduces temperature as a variable parameter in the focus adjustment process. The control unit stores correspondence relationships that account for temperature effects, and adjusts focus parameters based on detected temperature conditions, compensating for thermal expansion and structural changes in the projection lens.
Solution Approach 2:
The patent implements temperature monitoring and feedback to the focus control system. By continuously monitoring temperature and adjusting focus parameters accordingly, the system compensates for thermal effects on lens structure, maintaining focus stability during prolonged operation.
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
The solution enables improved auto focus performance by dynamically adjusting the focal length based on projection distance and temperature, providing a preferable projection effect and user-friendly operation by allowing for calibration and correction of focus errors, thus enhancing user experience.
Implementation Method 1
enable the distance sensor to sense a projection distance between the projection device and the projection surface
Data Source
AI summary
A projection device, including a projection module, a projection lens, a distance sensor, a focus adjustment module, and a control unit, is provided. The projection module is configured to generate an image beam. The projection lens is disposed on a transmission path of the image beam. The focus adjustment module is connected to the projection lens. The control unit is configured to enable the projection device to enter a focus mode; enable the projection module to project the image beam to a projection surface; enable the distance sensor to sense a projection distance; calculate a focus adjustment parameter by using an auto focus transfer function according to the projection distance; and control the focus adjustment module to adjust a focal length of the projection lens according to the focus adjustment parameter. An auto focus method is also provided.