Projector Auto-Focus Calibration Using Adaptive Lens Lookup Segments
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Solution Overview
Problem
Projection images often become out of focus due to machine errors in traditional auto-focus systems, which cannot be compensated by factory corrections, leading to poor user experience from manual fine-tuning.
Innovation Solution
A projection apparatus and auto-focus method that utilizes a projection module, projection lens, actuator, distance sensor, and controller to dynamically adjust the focal length based on a look-up table and sensed projection distance, updating minimum and maximum focal-length segments after focus adjustment to enhance auto-focusing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional auto-focus method using fixed look-up table is used, then the focusing process is simple and fast, but the projection image is out of focus due to machine errors such as optical distortion
Solution Approach 1:
The patent applies dynamics by transforming the static look-up table into a dynamic one that can be updated during operation. The controller updates the look-up table based on actual focusing results and user adjustments, allowing the system to adapt to machine errors and optimize focusing accuracy over time, rather than relying on a fixed pre-programmed table
Solution Approach 2:
The patent implements feedback by using the focusing result as feedback information to update the look-up table. When the system performs auto-focus or when users manually adjust focus, this information is fed back to the controller which then modifies the look-up table entries, creating a closed-loop system that continuously improves focusing accuracy
Solution Approach 3:
The system applies self-service by automatically updating its own look-up table without requiring external intervention or recalibration procedures. The controller autonomously modifies the focusing parameters based on observed performance, enabling the system to self-correct machine errors and improve over time
2Measurement precision
If manual focus mechanism is provided for fine-tuning, then focusing accuracy can be improved, but user experience deteriorates due to the need for manual adjustment after each auto-focus
Solution Approach 1:
The system uses feedback from manual focus adjustments to automatically update the look-up table. When users manually adjust the focus, the controller captures this adjustment information and uses it to refine the look-up table, so that subsequent auto-focus operations automatically incorporate these corrections, eliminating the need for repeated manual adjustments
Solution Approach 2:
The system performs self-service by automatically learning from and adapting to manual focus adjustments. Instead of requiring users to repeatedly manually correct focus issues, the system autonomously updates its parameters based on observed adjustments, making the manual intervention unnecessary for subsequent operations
3Ease of manufacture
If look-up table correction is performed before leaving the factory, then manufacturing process is simplified, but machine errors such as optical distortion cannot be compensated
Solution Approach 1:
The patent applies preliminary action by pre-programming a basic look-up table during manufacturing that provides initial focusing capability. This preliminary table enables the projection apparatus to perform auto-focus immediately upon deployment, while allowing for subsequent updates to compensate for machine errors that become apparent during actual use
Solution Approach 2:
The system transitions from a static pre-factory look-up table to a dynamic table that evolves during operation. The look-up table is designed to be updated based on actual focusing performance and user adjustments, allowing the system to adapt to and compensate for machine errors such as optical distortion that cannot be fully corrected during manufacturing
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 addresses out-of-focus issues caused by machine errors, providing accurate and automatic focusing without the need for manual intervention, thereby improving user experience.
Implementation Method 1
Taking advantage of the small size and low cost of Time of Flight (ToF) to do autofocus is the trend of projection apparatus in recent years
Data Source
AI summary
A projection apparatus including a projection module, a projection lens, an actuator, a distance sensor and a controller is provided. The projection module is adapted to project an image beam onto a projection surface to generate a projection image. The projection lens is disposed on a transmission path of the image beam. The actuator is connected to the projection lens and configured to adjust a focal length of the projection lens. The distance sensor is configured to sense a projection distance between the projection apparatus and the projection surface. The controller is electrically connected to the projection module, the actuator and the distance sensor, and is configured to adjust the focal length of the projection lens according to a look-up table and the projection distance sensed by the distance sensor, so as to perform automatic focusing. The lookup table includes a plurality of focal-length segments. The focal length falls within one of the focal-length segments. After confirming an end of a focus adjustment phase, the controller updates a minimum value and a maximum value of the one of the focal-length segments. An auto-focus method is also provided.