Photoelectric Sensor Scan-Line Reset for Uniform Detection Values
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Solution Overview
Problem
Optical detection devices with photoelectric conversion elements, such as PIN photodiodes, face differences in detection values due to variations in time constants generated by differences in wiring length of scan lines, affecting the accuracy of biological information detection in sensors like fingerprint or vein sensors.
Innovation Solution
A detection device with a matrix configuration of detection elements, using reset control scan lines driven by a circuit with transistors that apply specific potentials to reduce the time constant differences, including a first transistor for a high potential, a second transistor in series for a lower potential, and a third transistor in parallel to moderate the potential supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common scan line drives a plurality of photoelectric conversion elements, then the device complexity is reduced, but detection precision deteriorates due to differences in time constant generated in drive signals caused by differences in wiring length of the scan line
Solution Approach 1:
The patent divides the scan line driving into two independent parts: a first scan line for resetting detection elements and a second scan line for reading detection signals. This segmentation allows each scan line to be optimized for its specific function, eliminating the time constant differences that occur when a single scan line performs both operations. The first scan line can be designed with longer wiring to reach all detection elements for reset, while the second scan line can be optimized for signal reading without the same timing constraints.
Solution Approach 2:
The patent applies preliminary reset action before signal reading by using the first scan line to reset all detection elements to a known initial state before the second scan line reads the detection signals. This preliminary action ensures that all detection elements start from the same electrical state, eliminating variations caused by different wiring lengths and time constants during the subsequent signal reading phase.
2Measurement precision
If reset control scan lines are added to manage potential differences, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent segments the scan line functions into dedicated first scan lines for reset control and second scan lines for signal reading. This segmentation allows the reset control to be independently optimized without interfering with the signal reading process, improving measurement precision while keeping the added complexity manageable through clear functional separation.
Solution Approach 2:
The patent introduces intermediate reset control transistors and circuitry that act as mediators between the control signals and the detection elements. These intermediate components ensure uniform reset potential distribution across all detection elements, eliminating the direct impact of wiring length variations while adding controlled complexity only where necessary for potential management.
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 reduces variations in detection values across the detection area, enhancing the accuracy and consistency of biological information detection by minimizing the impact of wiring resistance and parasitic capacitance on the reset control scan lines.
Implementation Method 1
a plurality of photoelectric conversion elements such as positive-intrinsic-negative (PIN) photodiodes are arranged on a substrate
Data Source
AI summary
A detection device includes a plurality of detection elements arranged in a matrix having a row-column configuration in a detection area, a plurality of scan lines each coupled to the detection elements arranged in a first direction, a drive circuit configured to drive the scan lines, a plurality of output signal lines each coupled to the detection elements arranged in a second direction different from the first direction, and a detection circuit configured to be supplied with detection signals from the detection elements through the output signal lines.