Image Sensor Microlens Layout for Stable Pupil-Divided Focusing
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Solution Overview
Problem
Variation in pupil intensity distribution of pixels for focusing due to positional production tolerance of image sensor components leads to unstable focus detection accuracy and parallax signals.
Innovation Solution
An image sensor design where pixels for focusing and imaging are two-dimensionally arranged with a micro lens, photoelectric conversion units, and a light-shielding layer. The light-shielding layer has an opening with its central point eccentric relative to the photoelectric conversion unit, and the focal position of the micro lens is positioned further on the micro lens side than the light-shielding layer, with a distance greater than 0 and less than nFΔ, where n is the refractive index, F is the aperture value, and Δ is the diffraction limit of the micro lens.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a light-shielding layer with an opening is provided between the micro lens and photoelectric conversion unit for pupil division, then focus detection accuracy can be improved through controlled pupil intensity distribution, but variation in pupil intensity distribution occurs due to positional production tolerance of components
Solution Approach 1:
The patent applies parameter changes by positioning the focal point of the micro lens at a specific distance from the light-shielding layer, defined as greater than 0 and less than or equal to 0.6 times the diffraction limit (λ/NA). This precise control of the focal position parameter ensures that the light spot size remains within acceptable bounds, making the pupil intensity distribution less sensitive to positional variations in the light-shielding layer opening, thereby improving reliability while maintaining focus detection accuracy
Solution Approach 2:
The patent implements beforehand cushioning by pre-positioning the focal point at an optimized distance from the light-shielding layer before production variations occur. This pre-configured focal position acts as a buffer that compensates for potential positional tolerances in manufacturing, ensuring that even with variations in the light-shielding layer opening position, the pupil intensity distribution remains stable and focus detection accuracy is maintained
2Manufacturing precision
If the light-shielding layer opening is positioned to achieve desired pupil intensity distribution, then peak intensity and half-value width can be optimized, but positional production tolerance causes variation in pupil intensity distribution
Solution Approach 1:
The patent changes the critical parameter from the position of the light-shielding layer opening to the focal position of the micro lens. By controlling the focal position to be within a specific range (0 < focal distance ≤ 0.6λ/NA), the system achieves pupil intensity distribution control that is less sensitive to opening position variations, thereby improving reliability while maintaining manufacturing precision
Solution Approach 2:
The patent employs feedback by using the focal position as a controllable parameter that influences the pupil intensity distribution. The designed focal position range provides a feedback mechanism where deviations in light-shielding layer position are compensated by the optical system's response, ensuring stable pupil intensity distribution characteristics
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 configuration suppresses variation in pupil intensity distribution, enhancing the stability of focus detection accuracy and parallax signals by maintaining the desired pupil intensity distribution characteristics despite production tolerance variations.
Implementation Method 1
a micro lens provided on a light-receiving side of each of the plurality of pixels; a photoelectric conversion unit provided in each of the plurality of pixels, and for receiving light collected by the micro lens
Implementation Method 2
a photoelectric conversion unit provided in each of the plurality of pixels, and for receiving light collected by the micro lens
Implementation Method 3
a light-shielding layer provided between the micro lens and the photoelectric conversion unit of the pixel for focusing, and having an opening whose central point is eccentric relative to a central point of a light-receiving surface of the photoelectric conversion unit
Data Source
AI summary
In an image sensor, if a pixel for focusing has a structure having a light-shielding layer for performing pupil division, between the micro lens and the photoelectric conversion unit, the pixel may be configured such that the focal position of the micro lens is positioned further on the micro lens side than the light-shielding layer, and the distance from the focal position of the micro lens to the light-shielding layer is greater than 0 and less than nFΔ, where n is the refractive index at the focal position of the micro lens, F is the aperture value of the micro lens, and Δ is the diffraction limit of the micro lens. This enables variation in the pupil intensity distribution of the pixel for focusing due to positional production tolerance of components to be suppressed.