Sensor Pixel Circuit Managing External Light Interference
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Solution Overview
Problem
Conventional sensors, particularly optical type sensors, face inaccuracies in sensing recognition objects due to external light interference, leading to distorted sensing results as the brightness of the sensed object is inaccurately perceived with increasing external light.
Innovation Solution
A sensor pixel circuit comprising a photodiode, a storage capacitor, and multiple transistors that manage bias and reset voltages, along with pulse signals, to accurately sense recognition objects by differentiating current flows based on incident light, thereby enhancing sensing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an optical type sensor is used to sense recognition objects, then the sensor can detect light from the recognition object, but the sensing results are distorted by external light interference and become inaccurate as external light brightness increases
Solution Approach 1:
The patent segments the sensing process into distinct time intervals: a first time interval for sensing the recognition object and a second time interval for compensating external light interference. By separating these functions temporally, the circuit can accurately measure the recognition object while excluding external light effects that occur during the compensation interval.
Solution Approach 2:
The patent employs periodic switching of transistors to alternately perform recognition object sensing and external light compensation. The first transistor is activated during the first time interval to sense the recognition object, then deactivated during the second time interval when the third transistor activates to compensate external light. This periodic action enables the system to distinguish between signal from the recognition object and external light interference.
2Measurement precision
If multiple transistors and capacitors are added to the sensor pixel circuit to manage bias and reset voltages, then sensing accuracy is improved, but the device complexity increases
Solution Approach 1:
The storage capacitor serves multiple functions: it stores the sensing signal from the photodiode during the first time interval and also stores the external light compensation signal during the second time interval. By reusing the same capacitor for both sensing and compensation operations, the circuit achieves accurate external light cancellation without adding excessive complexity.
Solution Approach 2:
The circuit temporarily stores sensing signals and compensation signals in capacitors during specific time intervals, then processes and discards these temporary storage elements after their function is complete. This approach allows complex signal processing to occur in discrete stages rather than requiring all components to be active simultaneously, effectively managing circuit complexity.
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
The solution enables precise sensing of recognition objects by effectively managing light-induced currents and voltages, reducing external light interference and improving the accuracy of sensor readings.
Implementation Method 1
a photodiode to which a current flows according to incident light
Data Source
AI summary
A sensor pixel circuit may include: a photodiode to which a current flows according to incident light; a storage capacitor connected in parallel to the photodiode; a first transistor for connecting a bias voltage and the photodiode by a contact of a recognition object; and a second transistor for transmitting charges stored in the storage capacitor to a data line.