GmAPD Imager FOV Expansion via Digital Micro-Mirror Switching
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Solution Overview
Problem
Current single-photon imaging systems, particularly Geiger-mode avalanche diode (GmAPD) arrays, face limitations in scaling pixel formats to increase the field-of-view (FOV) due to technological and cost constraints, as well as reduced fill factor and image resolution.
Innovation Solution
Employing a digital micro-mirror device (DMD) array in conjunction with a static mirror to switch between two angular positions, allowing a single GmAPD-based imager to capture two or more fields of view without scaling the pixel format, thereby increasing the FOV while maintaining cost-effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the pixel format of GmAPD arrays is scaled up to increase field-of-view, then the FOV is improved, but the manufacturing cost and technological complexity increase significantly
Solution Approach 1:
The field-of-view is segmented into multiple discrete angular positions, each captured by the same GmAPD array. The DMD array segments the incoming light field into different angular sectors that can be sequentially directed to the detector, allowing FOV expansion without increasing detector pixel count or format size.
Solution Approach 2:
A digital micro-mirror device (DMD) array is introduced as an intermediary optical element between the scene and the GmAPD detector. The DMD acts as a programmable beam director that redirects light from different angular positions to the fixed detector array, enabling FOV multiplication without scaling the detector format.
2Area of stationary object
If the pixel format of GmAPD arrays is scaled up to increase field-of-view, then the FOV is improved, but the fill factor and image resolution are reduced
Solution Approach 1:
The optical system is made dynamic through the DMD array, which can rapidly switch between different angular positions. This dynamic beam steering allows a single static detector array to effectively sample multiple spatial positions sequentially, achieving high resolution in each position without requiring a larger detector format that would reduce fill factor.
Solution Approach 2:
The system adds the time dimension to the spatial sampling process. Instead of capturing all spatial positions simultaneously with a large-format detector, the DMD enables sequential sampling of different angular positions over time, transforming a spatial problem into a temporal-spatial solution that maintains high resolution.
3Area of stationary object
If a larger pixel format is used to increase field-of-view, then the FOV is improved, but the cost increases due to more expensive detector real estate
Solution Approach 1:
The DMD array creates virtual copies of the detector's field-of-view by digitally redirecting light from different angular positions to the same physical detector pixels. Each angular position is effectively a copied view that can be captured by the same detector real estate, multiplying the effective FOV without increasing the physical detector size.
Solution Approach 2:
The same GmAPD detector array serves multiple functions by capturing images from different angular positions sequentially. The detector real estate is universally utilized for multiple viewing directions, maximizing the utility of each detector pixel and avoiding the need for additional detector real estate to expand FOV.
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 effectively doubles or quadruples the FOV of GmAPD imagers without the need for larger pixel formats, ensuring no blind spots and maintaining high image resolution, while reducing costs by using less expensive DMD technology compared to scaling pixel formats.
Implementation Method 1
a digital micro-mirror device (DMD) array in conjunction with a static mirror to switch between two angular positions
Implementation Method 2
photo-excited carriers induced in the absorption region of the device are injected into a multiplication region where they are accelerated by a large electric field. When an injected carrier reaches a sufficiently high kinetic energy, it can generate another free electron-hole pair through an inelastic collision with lattice atoms in a process referred to as 'impact ionization'
Implementation Method 3
At a sufficiently large electric-field intensity, known as the 'avalanche breakdown field,' there is a finite probability that the avalanche multiplication process can lead to a self-sustaining avalanche
Data Source
AI summary
A GmAPD imager with an increased field of view includes at least one array of movable mirrors. Each movable mirror in the array switches between at least two positions (states). The movable mirrors receive light coming from a first direction when the mirror is in the first state and a second direction when the mirror is in the second state, thus increasing the field of view of the imager.