Light Detection Circuit Backlight Saturation Suppression
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Solution Overview
Problem
Current laser receivers for leveling applications face challenges with low saturation threshold, signal strength, and accuracy under bright sunlight conditions, particularly with Position Sensitive Devices (PSDs) which suffer from saturation and non-linearity, limiting their use in outdoor applications.
Innovation Solution
An electronic light detection circuit with a high input resistance amplifier and active resonator structure that provides low load impedance for low frequencies to suppress backlight saturation and high load impedance at modulation frequencies to maintain signal integrity, allowing for extended detection range and accuracy without increasing sensor size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Position Sensitive Devices (PSDs) are used for light detection, then detection sensitivity is improved, but saturation occurs under bright sunlight conditions
Solution Approach 1:
The patent applies periodic action by using amplitude modulation of the laser beam at a specific frequency and synchronizing the detection circuitry to respond only at this frequency. The resonator circuit is tuned to resonate at the modulation frequency, creating a periodic response that rejects DC and low-frequency background light, thereby preventing saturation while maintaining detection sensitivity.
Solution Approach 2:
The patent changes the frequency parameter of the laser beam through amplitude modulation and uses a resonator circuit with specific resonance frequency to select the modulated signal from the background. By changing the operational frequency parameter and using frequency-selective detection, the system distinguishes the weak modulated signal from strong background light, resolving the saturation problem.
2Measurement precision
If detection range is extended, then measurement accuracy is improved, but signal strength decreases
Solution Approach 1:
The patent uses periodic amplitude modulation of the laser beam to encode the signal at a specific frequency. The resonator circuit is tuned to this frequency, creating a selective detection mechanism that amplifies only the modulated signal components. This periodic action allows the system to maintain high signal strength at extended ranges by rejecting background noise and interference through frequency selectivity.
Solution Approach 2:
The resonator circuit provides feedback by amplifying the modulated signal components that match its resonance frequency while attenuating others. This feedback mechanism enhances the signal strength at the detection point, allowing accurate measurements at extended ranges without significant signal loss.
3Measurement precision
If non-linearity is present in the detection system, then response accuracy is degraded, but linearization requires complex circuitry
Solution Approach 1:
The patent uses periodic amplitude modulation to linearize the detection response. By modulating the laser beam at a fixed frequency and using a resonator circuit tuned to this frequency, the system creates a linear relationship between the modulated signal amplitude and the detection output. This periodic modulation approach provides linearization without requiring complex analog-to-digital conversion or digital signal processing circuits.
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 enhances the detection range and accuracy of laser receivers by effectively suppressing backlight interference and maintaining linearity, enabling reliable operation in bright sunlight conditions and extending the range of laser leveling systems.
Implementation Method 1
a photosensitive element (1), in particular a light position detector for detecting a striking position of the light signal spot within a detection window
Implementation Method 2
an active resonator structure, in particular with at least one operational amplifier, designed in such a way to provide a load impedance to an output of the photosensitive element with: a low load impedance for low frequencies, in particular for the frequency range of zero to twice of mains frequency
Data Source
Figure 1a~1b
Figure 2a~2b
Figure 3~4
AI summary
An electronic light detection circuit for detecting an intensity modulated light signal on a photosensitive element under backlight condition. The circuit comprises the photosensitive element, in particular as a light position detector for detecting a striking position of the light signal spot within a detection window, an amplifier with high input resistance connected to an output of the photosensitive element and a backlight suppression circuitry. The backlight suppression circuitry is connected to the output of the photosensitive element in parallel to the amplifier and comprises an electronic active resonator structure. The active resonator structure is designed in such a way to provide a load impedance to an output of the photosensitive element with a low load impedance for low frequencies for suppression of natural and artificial backlight-saturation of the photosensitive element and a high load impedance at the frequency of the intensity modulated light signal.