Auto Focus Apparatus Encoder Initial Position Optimization
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Solution Overview
Problem
Existing auto focus camera systems face inefficiencies due to the use of a single minimum VCM driving current value for all Voice Coil Motors, leading to increased AF driving time and unnecessary steps, as they cannot be optimized for individual VCM current values, resulting in suboptimal AF performance.
Innovation Solution
The implementation of an encoder-based method that sets the initial auto focus position to a specific value, dividing the focus distance into preset steps, and adjusting the lens position based on detected edge values to minimize unnecessary steps and optimize AF driving time, regardless of VCM driving current values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single minimum VCM driving current value is used for all Voice Coil Motors, then manufacturing complexity is reduced, but auto focus driving time increases and performance deteriorates
Solution Approach 1:
The patent applies parameter changes by measuring the actual driving current value of each individual VCM and using this measured parameter to determine the optimal number of AF driving steps. Instead of using a fixed minimum current value for all motors, the system adjusts the driving parameters (number of steps) based on the actual current characteristics of each motor, thereby reducing AF time while maintaining manufacturing simplicity.
2Device complexity
If a single minimum VCM driving current value is used for all Voice Coil Motors, then device complexity is reduced, but auto focus performance deteriorates
Solution Approach 1:
The patent implements self-service by having each VCM measure its own driving current value, which is then used to determine the appropriate number of AF driving steps for that specific motor. This self-measurement and self-adjustment mechanism allows the system to optimize performance for each individual motor without requiring complex external calibration or control systems.
Solution Approach 2:
The system employs feedback by measuring the actual driving current value of each VCM and using this feedback information to adjust the number of AF driving steps. The measured current value feeds back into the control logic to determine the optimal stopping point for the AF process, ensuring reliable performance while maintaining simple system architecture.
3Reliability
If individual optimization for each VCM current value is implemented, then auto focus performance improves, but manufacturing complexity and cost increase
Solution Approach 1:
The patent resolves this contradiction by having each VCM measure its own driving current value during the manufacturing or initialization process. This self-measurement approach eliminates the need for complex external testing equipment or manual calibration procedures, allowing individual optimization without significantly increasing manufacturing complexity or cost.
Solution Approach 2:
The system changes the approach from using fixed manufacturer-specified current values to using actually measured current values from each individual VCM. This parameter change allows the system to achieve optimal performance for each motor while keeping the manufacturing process simple, as the measurement and adjustment are performed automatically by the camera system itself.
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 auto focus driving time by eliminating unnecessary steps and ensuring rapid AF operation, allowing for efficient focus adjustment irrespective of VCM driving current values, thereby improving manufacturing yield and AF performance.
Implementation Method 1
detecting an encoder initial value by measuring an initial position of a lens unit by means of an encoder
Implementation Method 2
a driving unit for moving the lens unit, and including a Voice Coil Motor for driving the lens unit
Data Source
AI summary
An auto focus (AF) apparatus and method for a camera that improves the AF action by reducing the number of time and steps required of a conventional apparatus and method. An encoder initial value is detected by measuring an initial position of a lens unit by means of an encoder; matching the measured encoder initial value to an initial position value to which the lens unit is to move while performing the auto focus; performing the auto focus starting from the matched initial position value, and dividing a distance that the lens unit is to cover into sections corresponding to a preset number of steps; detecting an edge value which shows a brightness change for a contour of a subject for as many as the number of the preset steps. The AF is completed by moving the lens unit to a position corresponding to a maximum edge value selected from among the detected edge values.