Two Mirror Optical Arrangement for DMD Confocal Microscopy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Digital micromirror devices (DMDs) face challenges when used in bidirectional modes, particularly in confocal microscopy, due to the 24° illumination angle causing optical aberrations and astigmatism in existing Offner triplet mirror arrangements, which are not optimized for angles greater than 24° and can lead to suboptimal performance in cameras and semiconductor chip illumination.
Innovation Solution
An optical arrangement featuring a convex and concave mirror pair with a 2.5:1 radius ratio and a collimated space adjacent to the convex mirror, allowing light to be directed normal to an image receptor, reducing optical aberrations and enabling bidirectional imaging without obstructing the mirrors, and incorporating a DMD at the effective focal length for improved image formation and refocusing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a Schwarzschild-type mirror arrangement (Offner triplet) is used to deliver light to and collect light from a DMD at a 24° illumination angle, then the system can achieve bidirectional operation for confocal microscopy, but optical aberrations and astigmatism occur because the arrangement is not optimized for angles greater than 24°
Solution Approach 1:
The patent changes the illumination angle parameter from the conventional 24° to a higher angle (greater than 24°), and accordingly optimizes the mirror radii ratio to 2.5:1 (concave to convex) to maintain optimal optical performance at this new angle, thereby resolving the contradiction between bidirectional operation capability and optical aberration control
Solution Approach 2:
The patent introduces a collimated space immediately adjacent to and extending from the convex mirror towards the image receptor device, creating a localized region with specific optical properties (collimated light paths normal to the detector surface) that improves image quality at the detection plane without compromising the overall bidirectional operation
2Device complexity
If the DMD is used at a 24° illumination angle in an Offner triplet arrangement, then the system structure is established, but cameras and semiconductor chips cannot operate optimally because they are designed for significantly smaller angles of incidence
Solution Approach 1:
The patent changes the angle of incidence parameter for the image receptor from the conventional small angle to normal incidence (90°) by introducing a collimated space, thereby enabling cameras and semiconductor chips to operate at their optimal design conditions while maintaining the overall system structure
3Adaptability or versatility
If excitation light is introduced into the Offner triplet system in a conventional manner, then the system can be configured for confocal microscopy, but astigmatism is introduced because the light source creates asymmetry in the optical path
Solution Approach 1:
The patent introduces a collimated space as an intermediary region between the convex mirror and the image receptor, where excitation light can be introduced without directly disrupting the symmetric optical path of the Offner triplet, thereby enabling confocal microscopy configuration while minimizing astigmatism
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 enhances image quality by minimizing astigmatism and third-order optical aberrations, allowing for efficient fluorescence confocal microscopy with reduced focus distortion and improved illumination uniformity, enabling the use of DMDs in confocal systems with better optical performance and flexibility in optical component placement.
Implementation Method 1
a mirror pair formed from a convex mirror and a concave mirror having a common centre of curvature... Light from an object is collected over an oblique range of angles to form a 1:1 image laterally inverted with respect to the object
Implementation Method 2
each micromirror can be moved electrostatically between two fixed positions, typically 12° either side of the plane of the device
Implementation Method 3
the concave mirror is offset from the convex mirror so as to be capable of forming an image at an effective focal length of the mirror pair
Data Source
Figure 1
Figure 2
Figure 3
AI summary
There is provided an optical arrangement comprising a digital micromirror device (62) having a plurality of individually adjustable mirrors, a mirror pair formed from a convex mirror (70) and a concave mirror (72) having a common centre of curvature, the concave mirror (72) having a greater radius than the convex mirror (70), characterised in that a collimated space (76) is immediately adjacent the convex mirror (70), and the concave mirror (72) is offset from the convex mirror (70) so as to be capable of forming an image at an effective focal length of the mirror pair. The convex mirror (70) and the concave mirror (72) have radii substantially in the proportion 2.5:1, the concave mirror having the greater radius. A confocal microscope using such an arrangement is also provided.