Color Separating Optical System Ghost Management
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Solution Overview
Problem
High-definition color imaging devices with Phillips-type color separating optical systems suffer from ghosting issues when a bright subject is at the image center, leading to degraded image sharpness due to diffraction effects from the image sensor's microstructure.
Innovation Solution
The color separating optical system is designed with prisms and dichroic films where the tilt angle of the second dichroic film is set to approximately the average of the diffraction angles of the second and third-order diffraction rays, ensuring that ghosts are distributed outside the center subject area by optimizing the tilt angle α to (βm+βm+1)/2, and an air gap is introduced to reduce total reflection critical angle within the second prism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Phillips-type color separating optical system with prisms and dichroic films is used, then color separation performance is improved and optics are compacted, but ghosting occurs on bright center subjects degrading image sharpness
Solution Approach 1:
The patent changes the parameter of the dichroic film tilt angle to a specific value that is the average of the diffraction angles of the second and third order diffraction rays. This parameter adjustment redirects the ghosting rays away from the center subject area, eliminating the harmful ghosting effect while preserving the color separation function of the optical system.
2Object-affected harmful factors
If the dichroic film tilt angle is adjusted to redirect diffraction rays, then ghosting is reduced, but color separation accuracy may be affected
Solution Approach 1:
The patent converts the harmful diffraction effect that causes ghosting into a beneficial element by calculating the specific tilt angle as the average of the second and third order diffraction angles. This transforms the diffraction phenomenon from a source of interference into a controlled optical path that separates ghosts from the center subject while maintaining color separation accuracy.
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 prevents ghosts from overlapping on the center subject, maintaining sharp image quality even in scenes with bright center subjects against dark backgrounds by carefully managing diffraction angles and tilt angles of dichroic films.
Implementation Method 1
the first dichroic film reflects a first color light component therefrom and transmits second and third color light components therethrough
Implementation Method 2
the first dichroic film reflects a first color light component therefrom
Implementation Method 3
the second color light component reflected from the second dichroic film is totally and internally reflected within the second prism
Implementation Method 4
ghosts can be superposed on the center subject in an image frame... diffraction effects from the image sensor's microstructure
Data Source
AI summary
A color separating optical system including first to third prisms for separating incident light from an objective lens into three primary color light components, so as to project three color-separated images of a subject onto first to third image sensors, respectively. In order to prevent ghosts from being superposed on a center area of an image frame, the color separating optical system satisfies the condition: α≈(βm+βm+1)/2, wherein “α” represents a tilt angle of a second dichroic film on the second prism to a perpendicular plane to an optical axis of the objective lens, and “βm” a diffraction angle of the second light component diffractively reflected from the second image sensor and reentering the second prism.