Sinusoidal Spatial Light Modulator for Autofocus Signal Processing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current autofocus mechanisms in optical devices face challenges with accuracy and speed in focus estimation due to the use of rotating perforated metal optical chopping wheels, which result in complex signal processing and noise interference, limiting their ability to provide precise and fast defocus correction.
Innovation Solution
A focusing module utilizing a spatial light modulator (SLM) configured to yield a circumferentially sinusoidal pattern, such as an optical chopper wheel with a glass disc, in conjunction with a diode array and processing unit, to simplify phase derivation and improve focus estimation accuracy and speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a rotating perforated metal optical chopping wheel is used in the autofocus mechanism, then the device can generate on and off periods in the illumination signal, but the signal processing becomes complex and noise interference increases
Solution Approach 1:
The patent changes the geometric parameters of the optical chopping wheel from a standard perforated pattern to a specific sinusoidal pattern with defined amplitude and period. This parameter change transforms the output signal from a complex multi-harmonic waveform to a pure sinusoidal waveform, simplifying the phase detection algorithm and reducing noise susceptibility while maintaining the same basic function of modulating illumination.
Solution Approach 2:
The patent modifies the optical transmission characteristics of the chopping wheel by using a sinusoidal pattern instead of a binary perforated pattern. This creates a continuous variation in light transmission analogous to a gradient, which produces a cleaner harmonic signal that is easier to process and less susceptible to noise, thereby reducing signal processing complexity.
2Measurement precision
If a rotating perforated metal optical chopping wheel is used in the autofocus mechanism, then the device can modulate illumination to detect defocus, but noise interference increases and measurement precision decreases
Solution Approach 1:
The patent changes the geometric parameters of the optical chopping wheel from a standard perforated pattern to a specific sinusoidal pattern with defined amplitude and period. This parameter change transforms the output signal from a complex multi-harmonic waveform to a pure sinusoidal waveform, simplifying the phase detection algorithm and reducing noise susceptibility while maintaining the same basic function of modulating illumination.
Solution Approach 2:
The patent converts the potentially harmful effect of light scattering and diffraction from the sharp edges of perforated patterns into a benefit by using smooth sinusoidal transitions. This eliminates the generation of spurious diffraction orders and reduces noise, while the periodic nature of the sinusoidal pattern maintains the necessary modulation for defocus detection.
3Measurement precision
If a sinusoidal pattern is used on the optical chopper wheel, then phase derivation is simplified and noise susceptibility is reduced, but the manufacturing complexity increases
Solution Approach 1:
The patent replaces the mechanical process of creating precise sinusoidal physical features on the chopper wheel with an optical/electronic approach. The sinusoidal pattern can be implemented as a transmission mask or generated through optical processing, eliminating the need for complex mechanical machining or lithography processes while achieving the same signal simplification and noise reduction benefits.
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 sinusoidal pattern enables faster and more accurate focus estimation by providing a single harmonic signal, reducing noise susceptibility and enhancing phase measurement sensitivity, resulting in quicker and more robust autofocus capabilities with improved stability and reduced noise.
Implementation Method 1
The sinusoidal pattern enables faster and more accurate focus estimation by providing a single harmonic signal
Data Source
AI summary
Focusing modules and methods are provided, which use a spatial light modulator (SLM) configured to yield a circumferentially sinusoidal pattern to derive focusing signals. For example, the SLM may comprise an optical chopper wheel made of a glass disc with a circumferentially sinusoidal pattern. The circumferentially sinusoidal pattern simplifies phase derivation from the focusing signal, providing a faster and more accurate estimation of defocusing. Signal detection may be carried out by a diode array that provides a more accurate signal faster, as well as a more differentiated analysis of the focusing signal than the one available by current technology.