Photon-Counting Imaging Circuits with Shared Time Measurement
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Solution Overview
Problem
Existing photoelectric conversion apparatuses increase circuit size due to the inclusion of photon and time counters for each pixel, leading to inefficiencies in pixel readout processing.
Innovation Solution
A photoelectric conversion apparatus with a shared time counter for a group of pixels and individual photon counters for each pixel, reducing circuit size by optimizing the distribution of measurement circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a time counter and photon counter are provided for each pixel, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The pixel array is divided into multiple blocks, with each block containing multiple pixels that share common measurement circuits. This segmentation allows reduction of per-pixel circuit complexity while maintaining measurement capabilities through block-level sharing of time counters and addition circuits.
Solution Approach 2:
The time counter and addition circuit are designed as shared resources that serve multiple pixels within a block. The time counter measures timing information for multiple pixels sequentially, and the addition circuit accumulates signals from multiple photons across different pixels, enabling one circuit to perform functions that would otherwise require dedicated circuits for each pixel.
2Measurement precision
If measurement circuits are provided for each pixel, then measurement precision is improved, but manufacturing precision requirements increase
Solution Approach 1:
Multiple pixel measurement functions are merged into shared circuits at the block level. The time counter, addition circuit, and threshold comparison logic are combined into common resources that serve multiple pixels, reducing the total number of discrete circuits that require precise manufacturing and integration.
Solution Approach 2:
The pixel array is segmented into blocks with shared resources, allowing manufacturing precision requirements to be distributed and managed at a coarser granularity level rather than requiring ultra-precise integration of individual circuits for every single pixel.
3Device complexity
If a time counter is shared among multiple pixels, then device complexity is reduced, but measurement precision may deteriorate
Solution Approach 1:
The shared time counter operates in a periodic manner, sequentially serving different pixels within a block. Each pixel receives dedicated time measurement service in turn, with the time counter being reset and restarted for each pixel's measurement cycle. This periodic operation ensures that each pixel receives accurate time measurement while allowing the same circuit to be shared across multiple pixels.
Solution Approach 2:
The system performs preliminary organization of pixel measurement sequences, assigning specific time slots and measurement cycles to different pixels before actual measurement begins. This preliminary scheduling ensures that the shared time counter can accurately measure time for each pixel without interference, maintaining precision while enabling sharing.
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 allows for efficient pixel readout processing while minimizing circuit size, enhancing the apparatus's performance and efficiency.
Implementation Method 1
a photoelectric conversion apparatus has been discussed in which the number of photons incoming and incident on an avalanche photo diode is digitally counted and the counted number is output from a pixel as a digital signal through photoelectric conversion
Data Source
AI summary
A photoelectric conversion apparatus includes a pixel including a photoelectric conversion circuit configured to output a signal corresponding to photon incidence. The photoelectric conversion apparatus further includes a first measurement circuit, an addition circuit, and a second measurement circuit. The first measurement circuit is configured to measure the signal output from the pixel. The addition circuit is configured to add measured values of a plurality of the first measurement circuits. The second measurement circuit is configured to measure a time from when each of the plurality of first measurement circuits starts measuring the signal to when the measured values added by the addition circuit reach a first threshold value.