Aberration Control Element for Depth of Field and Noise Reduction
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Solution Overview
Problem
Existing imaging apparatuses face challenges in extending the depth of field while reducing noise in images, as increasing the F value to achieve this results in lack of light and increased noise in captured images.
Innovation Solution
An imaging apparatus with a photographic optical system incorporating an aberration control element that sets the response of the optical transfer function to zero at specific spatial frequencies, improving image characteristics by positioning the field distances of spherical aberration curves to reduce noise and blur.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the F value is increased to extend the depth of field, then the depth of field is extended, but the light intensity decreases and noise increases
Solution Approach 1:
The patent changes the optical parameters by introducing an aberration control element that generates specific spherical aberration, transforming the optical transfer function characteristics. This allows the system to achieve extended depth of field while maintaining adequate light intensity by redistributing the optical energy across different spatial frequencies rather than simply stopping down the aperture.
Solution Approach 2:
The aberration control element acts as an intermediary component between the lens system and the image sensor. It introduces controlled spherical aberration that modifies the point spread function and optical transfer function, enabling the system to achieve extended depth of field without the adverse effects of aperture reduction.
2Stability of the object's composition
If the F value is increased to extend the depth of field, then the depth of field is extended, but the noise in captured images increases
Solution Approach 1:
The patent modifies the optical transfer function parameters by introducing controlled spherical aberration. The aberration control element is designed to set the OTF response to zero at specific spatial frequencies (below the Nyquist frequency) while positioning the spherical aberration curve characteristics to optimize the trade-off between depth of field extension and noise reduction.
Solution Approach 2:
The patent converts the typically harmful spherical aberration into a beneficial element. By carefully controlling the amount and characteristics of spherical aberration introduced by the aberration control element, the system achieves extended depth of field while the specific OTF zero-point positioning reduces noise in the captured images.
3Stability of the object's composition
If restoration processing is carried out to reduce blur, then the depth of field is extended, but the noise increases due to low optical transfer function response
Solution Approach 1:
The patent optimizes the optical transfer function parameters by positioning the OTF zero-point at a specific spatial frequency below the Nyquist frequency. This parameter optimization ensures that the modulation transfer function maintains adequate response characteristics, reducing the need for aggressive restoration processing and thereby minimizing noise amplification.
Solution Approach 2:
The aberration control element performs preliminary optimization of the optical transfer function before image capture. By pre-positioning the OTF zero-point and shaping the spherical aberration curve, the system prepares the optical path to minimize blur and noise simultaneously, reducing the burden on subsequent restoration processing.
Data Source
AI summary
An imaging apparatus includes a photographic optical system, an image sensor, and an image processing unit. The system includes an aberration control element for generating a predetermined aberration. The system forms an optical image. The image sensor generates an image signal corresponding to the image. The processing unit processes the image signal to improve image characteristics degraded based on the predetermined aberration. The aberration control element, at a first spatial frequency less than a Nyquist frequency of the image sensor, sets a response of a system optical transfer function to a reducible maximum value. The aberration control element positions a field distance of a maximum pupil height of a spherical aberration curve of the system, and a field distance of an inflection point proximate to the maximum pupil height, on either a plus side or a minus side with respect to a field distance of the pupil height of zero.