Hyperchromatic Lens Depth of Field Extension
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Solution Overview
Problem
Optical tomography systems face limitations in achieving high resolution and signal-to-noise ratio while maintaining acceptable resolution, particularly in sampling biological cells, due to the depth of field constraints and the need for rapid image acquisition.
Innovation Solution
The implementation of a hyperchromatic optical lens system that utilizes chromatic aberrations to extend the depth of field by focusing multiple focal depths on a detector, allowing for simultaneous imaging of multiple object planes within a narrow wavelength range, and the use of a chromatic filter array to separate and process signals from different focal ranges, reducing the need for high-speed lens translation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a PZT actuator is used to move the objective lens transverse to the capillary tube to extend depth of field, then multiple focal planes can be scanned through the specimen, but the scan rate is limited to roughly 60 cycles per second due to inertia of the objective lens mass
Solution Approach 1:
The patent replaces the mechanical PZT actuator system with an acousto-optic modulator (AOM) that uses sound waves to diffract light. Instead of physically moving the objective lens, the AOM creates multiple virtual images of the specimen at different apparent focal planes by modulating the light path with acoustic waves. This substitution eliminates the inertia limitations of mechanical systems while achieving the same depth of field extension effect.
Solution Approach 2:
The patent introduces an acousto-optic modulator as an intermediary element between the light source and the specimen. The AOM uses acoustic waves as a mediator to control the optical path, creating frequency-shifted diffracted orders that correspond to different focal planes. This intermediary approach allows rapid switching between focal planes without moving the heavy objective lens.
2Productivity
If the objective lens is scanned rapidly to acquire multiple images per second, then image acquisition speed can be improved, but the complexity of synchronizing lens scanning with rotation and the inertia of the lens mass increase
Solution Approach 1:
The patent eliminates the mechanical scanning system entirely and replaces it with an acousto-optic modulator that can switch between focal planes electronically. The AOM can be modulated at very high frequencies by simply changing the electrical drive signal, eliminating the need for complex mechanical synchronization between lens scanning, stage rotation, and camera exposure timing.
Solution Approach 2:
The patent transforms the static mechanical scanning system into a dynamic acousto-optic system where the focal plane selection is controlled by the frequency and phase of acoustic waves. This allows rapid, flexible switching between focal planes without the mechanical inertia and synchronization complexity of the original system.
3Speed
If chromatic aberrations are used to extend depth of field by focusing multiple focal depths, then simultaneous imaging of multiple object planes is achieved, but the system requires a chromatic filter array to separate signals from different focal ranges
Solution Approach 1:
The patent converts the typically harmful chromatic aberration into a useful feature. By deliberately using the chromatic dispersion of the objective lens, different wavelengths are focused at different depths, creating extended depth of field. The chromatic filter array then separates these wavelength-encoded depth signals, converting what is normally an optical defect into a functional depth-multiplexing mechanism that enables simultaneous multi-plane imaging.
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 approach enhances image acquisition speed, reduces the complexity of instrument control, and improves spatial resolution and contrast by allowing multiple pseudo-projections to be acquired from various angles without high-speed lens movement, thereby overcoming the limitations of traditional systems.
Implementation Method 1
A hyperchromatic lens is located to receive light transmitted through the microcapillary tube viewing area. A tube lens is located to focus light rays transmitted through the hyperchromatic lens, such that light rays from multiple object planes in the microcapillary tube viewing area simultaneously focus on the at least one detector.
Implementation Method 2
the use of a chromatic filter array to separate and process signals from different focal ranges
Implementation Method 3
A motor is located to attach to and rotate a microcapillary tube
Implementation Method 4
A device is arranged for transmitting broadband light having wavelengths between 550 nm and 620 nm into the microcapillary tube viewing area
Data Source
AI summary
An optical tomography system for viewing an object of interest includes a microcapillary tube viewing area for positioning the object of interest in an optical path including a detector. A motor is located to attach to and rotate a microcapillary tube. A device is arranged for transmitting broadband light having wavelengths between 550 nm and 620 nm into the microcapillary tube viewing area. A hyperchromatic lens is located to receive light transmitted through the microcapillary tube viewing area. A tube lens is located to focus light rays transmitted through the hyperchromatic lens, such that light rays from multiple object planes in the microcapillary tube viewing area simultaneously focus on the at least one detector.