Optical Sensor Sensing Circuit Fast Response
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Solution Overview
Problem
Optical sensors face limitations in sensitivity and response speed due to the constraints of integration periods and noise components, particularly in applications requiring fast response, where the stepwise discharge period often becomes a bottleneck, limiting the ability to maintain sensitivity and secure a sufficient integration period.
Innovation Solution
The optical sensor incorporates an analog/digital converter and a controller that discharges the analog output signal when the digital output reaches a threshold during the integration period, eliminating the need for a stepwise discharge period and allowing for a longer integration period, thereby enhancing sensitivity and reducing noise components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a stepwise discharge period is used to reset the integrator, then the integrator can be reused for the next measurement, but the response speed is limited due to the additional time required for discharge
Solution Approach 1:
The patent extracts the discharge function from the main measurement cycle by using a separate discharge switch (125) that operates independently. The discharge operation is performed in parallel with the integration preparation, allowing the integrator to be reset without blocking the measurement process. This separation of discharge and measurement operations eliminates the time loss associated with sequential stepwise discharge.
Solution Approach 2:
The patent implements preliminary discharge action by controlling the discharge switch to reset the integrator before the next measurement cycle begins. The discharge operation is performed in advance during the period when the previous measurement is being processed or when the system is preparing for the next measurement, ensuring the integrator is ready without delaying the measurement speed.
2Measurement precision
If the integration period is extended to improve sensitivity, then more light charge is accumulated, but the response speed decreases due to the longer measurement cycle
Solution Approach 1:
The patent implements dynamic control of the integration period through the controller (129) which can adjust the integration time based on measurement conditions. The integration period is dynamically optimized to accumulate sufficient light charge for high sensitivity while maintaining a short overall measurement cycle for fast response. This dynamic adjustment allows the system to achieve both high sensitivity and fast response speed adaptively.
Solution Approach 2:
The patent ensures continuous useful action by overlapping the discharge operation with the preparation phase of the next measurement cycle. While the integrator is being discharged, the system is already preparing for the next measurement, eliminating idle time and maintaining continuous productive operation. This continuity allows extended integration periods for sensitivity without proportionally increasing the total measurement cycle time.
3Reliability
If multiple discharge operations are performed stepwise, then the integrator is fully reset, but the measurement cycle becomes longer and sensitivity is compromised
Solution Approach 1:
The patent rushes through the discharge process by using a dedicated discharge switch (125) that performs rapid discharge in a single operation rather than multiple stepwise discharges. The discharge is completed quickly during a brief discharge period, skipping the time-consuming sequential discharge steps. This allows complete integrator reset without compromising measurement efficiency or sensitivity.
Solution Approach 2:
The patent introduces a discharge switch (125) as an intermediary component that mediates the discharge process. This switch provides a controlled pathway for rapid discharge of the integrator, separating the discharge function from the measurement function. The intermediary switch enables complete and reliable reset of the integrator while maintaining short measurement cycles, as the discharge operation is efficiently managed by this dedicated component.
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 enables fast operation with an improved signal-to-noise ratio (SNR) and increased sensitivity, even in applications requiring rapid response, by extending the integration period without compromising sensitivity.
Implementation Method 1
a light-sensing element 11 that generates a light-sense signal IPD
Data Source
AI summary
For example, a sensing circuit includes: an integrator configured to generate an analog output signal by integrating an analog input signal; an analog/digital converter configured to convert the analog output signal into a digital output signal; and a controller configured to discharge the analog output signal when, during an integration period of the integrator, the digital output signal reaches a first threshold value.