Optical Sensor Digital Gain Control for Linear Light Sensing
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Solution Overview
Problem
Existing optical sensors amplify currents in an analog manner, leading to an amplification factor that is not proportional to the preset current factor due to their sensing circuit structure, especially when the sensed current and amplification factor are large, resulting in non-linear sensing curves and increased complexity in designing analog circuits.
Innovation Solution
An optical sensor with a high linearity digital controlling mechanism, comprising an optoelectronic component, current mirror, capacitor, comparator, and digital signal processor, which converts light energy into photocurrent, amplifies it, and uses a digital algorithm to generate a comparison signal, count bit values, and remove noise, ensuring the amplification factor is proportional to the preset gain and improving linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If analog current amplification is used in the sensing circuit, then the circuit structure is simple, but the amplification factor is not proportional to the preset current factor resulting in poor linearity
Solution Approach 1:
The patent replaces the analog current amplification mechanism with a digital counting mechanism. The sensing circuit still uses analog components (photodetector, current mirror, capacitor, comparator), but the amplification and measurement function is transferred to the digital domain where the counter counts clock cycles proportional to the charging current. This substitution eliminates the non-linear analog amplification while maintaining circuit simplicity.
Solution Approach 2:
The patent changes the measurement parameter from directly measuring analog current amplitude to measuring the time duration (number of clock cycles) required to charge the capacitor to a reference voltage. This parameter transformation from amplitude-domain to time-domain measurement ensures linearity because the charging time is directly proportional to the current magnitude, and the counter provides a linear digital representation of this time interval.
2Adaptability or versatility
If analog current amplification with large gain is used, then the sensing range is extended, but the linearity deteriorates and noise interference increases
Solution Approach 1:
The patent implements dynamic gain adjustment through the gain control circuit that modifies the charging current based on ambient light conditions. In low-light conditions, the gain is increased to extend the sensing range, while in bright conditions, the gain is reduced to maintain linearity and prevent saturation. The digital counter adapts its counting range accordingly, providing optimal performance across varying light levels without compromising linearity.
3Measurement precision
If digital signal processing with noise cancellation is applied, then the signal-to-noise ratio is improved, but the response time increases slightly
Solution Approach 1:
The patent employs periodic sampling and averaging of multiple measurement cycles to cancel random noise. The counter performs multiple counting operations and the results are averaged, which reduces the impact of random fluctuations and noise. This periodic action improves the signal-to-noise ratio while keeping the additional time required minimal compared to the benefit gained in measurement precision.
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 digital controlling mechanism effectively eliminates noise interference, improves linearity of the sensed curve, and ensures the amplification factor is proportional to the preset gain, simplifying analog circuit design, reducing errors due to light instability and noise, and enhancing signal-to-noise ratio at the expense of slight response time.
Implementation Method 1
the optoelectronic component is configured to convert light energy irradiating through the optoelectronic component into a photocurrent
Data Source
AI summary
An optical sensor and a method having a high linearity digital controlling mechanism are provided. An optoelectronic component converts a light energy into a photocurrent. Then, the photocurrent flows to a current mirror and is amplified by a gain to form a charging current by the current mirror to charge a capacitor. A comparator compares a voltage of the capacitor with a reference voltage multiple times to generate a comparison signal. A counter determines a digital value capturing range according to the gain, and counts bit values that fall within the digital value capturing range from the comparison signal to output a counted signal. A noise cancellation processor reduces the digital value capturing range according to the gain, and removes one or more of the bit values that do not fall within the digital value capturing range from the counted signal to output a sensed signal.