Focus Control Circuit Staged Lens Positioning
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Solution Overview
Problem
The contrast detecting method for auto-focusing in camera modules is time-consuming, making it difficult to achieve focus within one second after a shutter button is pressed halfway, especially with increasing pixel counts requiring high-resolution images and precise focus control.
Innovation Solution
A focus control circuit that includes an equalizer and a position setting unit to progressively move the lens through a series of staged positions, using a driver element and position detecting element, allowing for high-precision and rapid focus determination by sequentially setting multiple positions between the current and target lens positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the contrast detecting method is used to determine focus by actively moving the lens, then the cost is reduced compared to active methods, but the processing time increases making it difficult to complete focus within one second
Solution Approach 1:
The system performs preliminary actions by predicting the target focus position based on the relationship between previous target positions and actual focus positions. This prediction allows the lens to be positioned closer to the final target before the contrast detection search begins, reducing the distance the lens must travel during the actual focus search and thereby decreasing processing time while maintaining the cost-effective contrast detection method
2Measurement precision
If high-resolution images are taken with increasing pixel counts, then image quality is improved, but the requirement for high-precision auto-focus control increases making focus determination more time-consuming
Solution Approach 1:
The system performs preliminary positioning by predicting where the focus should be based on historical data from previous focusing operations. By pre-positioning the lens near the predicted target using this prediction mechanism, the subsequent contrast detection search starts from a position much closer to the final focus point, reducing the search distance and time required to achieve the high precision needed for high-resolution images
3Speed
If the lens is moved directly to the target position in one step, then the movement speed is maximized, but the positioning accuracy decreases making precise focus control difficult
Solution Approach 1:
The lens movement is segmented into multiple phases: a rapid preliminary movement to the predicted target position based on prediction algorithms, followed by a finer contrast detection search from that intermediate position. This segmentation allows the system to combine high-speed positioning with precise final focusing, achieving both speed and accuracy by dividing the movement into coarse and fine adjustment stages
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 reduces processing time for focus determination without compromising accuracy, enabling faster and more precise auto-focus control by progressively moving the lens to the target position, thus improving the speed and accuracy of focus adjustment.
Implementation Method 1
a driver element for adjusting the position of the lens
Implementation Method 2
a position detecting element for detecting the position of the lens
Implementation Method 3
an equalizer configured to generate a drive signal used to adjust the position of the lens identified by an output signal of the position detecting element to a position to be set, based on a difference between the position of the lens identified thereby and the set position
Data Source
AI summary
A focus control circuit is installed in an image pickup apparatus including a lens, a driver element for adjusting the position of the lens, and a position detecting element for detecting the position of the lens. An equalizer included in the focus control circuit generates a drive signal used to adjust the position of the lens to a position to be set, based on a difference between the position of the lens identified by the position detecting element and the set position. When an instruction to vary a target position of the lens is received externally, a position setting unit included in the focus control circuit sets sequentially a plurality of positions in a range covering a new target position and a previous target position, to the equalizer before the new target position is reached from the previous target position.