Focus Detection Device Correlated Noise Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional focus detection devices suffer from increased random noise due to correlated noise components in image signals, which degrades image quality and focus detection accuracy, especially in low contrast and luminance conditions.
Innovation Solution
A focus detection device that generates pairs of image signals from first and second photoelectric conversion portions, with a generation unit producing first and second image signals, and an adjustment unit adjusting the focus distance based on the correlation of noise components in these signals, minimizing the influence of correlated noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the B signal is generated by subtracting the A signal from the A+B signal, then three types of signals can be obtained by performing readout twice, but the B signal includes a noise component that is correlated to the noise component included in the A signal, which deteriorates focus detection accuracy
Solution Approach 1:
The patent divides the pixel array into multiple regions, with odd-numbered pixels reading out A signals and even-numbered pixels reading out B signals separately. This segmentation ensures that A and B signals are obtained through independent readout operations, eliminating correlated noise while maintaining efficient single-pass readout capability.
2Reliability
If the A+B signal is obtained by adding the A signal and the B signal, then the random noise of both signals is included, which deteriorates image quality, but reading out A and B signals separately increases readout operations
Solution Approach 1:
The pixel array is segmented into odd and even regions that independently read out A and B signals in a single pass. This eliminates the need for multiple readout operations to obtain both signals separately, while also avoiding the noise accumulation problem of adding A and B signals.
Solution Approach 2:
The patent introduces a spatial dimension solution by using different pixel positions (odd vs even) to capture different signal types. This dimensional approach allows simultaneous acquisition of A and B signals without temporal or operational multiplication.
3Measurement precision
If multiple pairs of image signals are generated for focus detection, then focus detection accuracy can be improved through multiple measurements, but the correlated noise components in each pair still affect the detection accuracy
Solution Approach 1:
By segmenting the pixel array into odd and even regions with independent readout paths, the patent generates multiple A and B signal pairs where each pair comes from spatially separated pixels. This segmentation breaks the correlated noise relationship, allowing multiple measurements to genuinely improve focus detection accuracy through statistical averaging.
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 effectively suppresses the impact of correlated noise on focus detection, improving image quality and accuracy by adjusting the focus distance based on the correlation of noise components in the image signals.
Implementation Method 1
a plurality of first signals obtained from a plurality of first photoelectric conversion portions that receive light flux that passes through a first pupil area of an exit pupil of an imaging optical system and a plurality of second signals obtained from a plurality of second photoelectric conversion portions that receive light flux that passes through a second pupil area of the exit pupil
Data Source
AI summary
A plurality of pairs of image signals each constituted by a first signal obtained by performing photoelectric conversion on light flux that passes through a first pupil area in the exit pupil of an imaging optical system and a second signal obtained by performing photoelectric conversion on light flux that passes through a second pupil area are generated. The plurality of pairs of signals differ in the correlation amount of noise components of the first and second signals constituting the pairs of signals. One of defocus amounts obtained from the pairs of signals is used to adjust the focus distance of the imaging optical system. Accordingly, a focus detection device that can suppress the influence of correlated noise included in the pairs of image signals on focus detection and a control method thereof are obtained.