Optoelectronic Sensor Reception Level Determination
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Solution Overview
Problem
Optoelectronic sensors face challenges in accurately determining object distance due to high signal dynamics caused by varying reflectance and distance, which require complex hardware and processing to manage the large dynamic range and correct for signal distortions.
Innovation Solution
An optoelectronic sensor system that determines the reception level using an additional circuit, such as a power supply and current measurement unit, allowing for cost-effective expansion of the dynamic range without affecting the actual signal measurement, and enables correction and algorithm selection based on the reception level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sampling of the received signal with several thresholds or an A/D converter is used to determine the reception level, then the reception level can be determined accurately, but the hardware complexity increases significantly
Solution Approach 1:
The patent introduces an intermediary current mirror circuit that copies the photocurrent from the light receiver. This current mirror acts as a mediator that provides measurement information about the reception level without requiring complex sampling or A/D conversion of the main signal path, thus maintaining measurement accuracy while reducing hardware complexity
Solution Approach 2:
The patent extracts the reception level information from the photocurrent using a separate current mirror circuit rather than processing the main reception signal. This extraction approach allows the main signal path to remain simple while obtaining the necessary measurement information through a dedicated auxiliary circuit
2Adaptability or versatility
If non-linear or logarithmic amplifiers are used to handle the large dynamic range, then the dynamic range can be managed, but these amplifiers are not available with sufficient bandwidth for nanosecond pulse processing
Solution Approach 1:
The patent creates a copy of the photocurrent signal using a current mirror circuit. This copied signal provides information about the reception level and can be processed separately, allowing the main high-speed signal path to operate at full bandwidth without being constrained by dynamic range compression requirements
Solution Approach 2:
The patent moves the dynamic range management to a different dimension by using a parallel current mirror circuit that operates independently from the main high-speed signal path. This allows dynamic range information to be obtained without compromising the bandwidth of the primary detection channel
3Adaptability or versatility
If multiple receiving channels with complementary amplification ranges are implemented, then the dynamic range is divided and managed, but the hardware outlay increases significantly
Solution Approach 1:
The current mirror circuit serves multiple functions: it provides reception level measurement information, enables dynamic range management, and maintains signal integrity for time-of-flight measurement. This single auxiliary circuit replaces what would otherwise require multiple separate receiving channels with different amplification characteristics
Solution Approach 2:
The patent combines the dynamic range management function with the existing photocurrent measurement circuitry by implementing a current mirror. This merges multiple functions (signal copying, level measurement, dynamic range handling) into a single integrated approach rather than requiring separate channels
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 approach simplifies signal evaluation, reduces hardware complexity, and improves accuracy by using simple means to determine the reception level, enabling reliable and inexpensive distance measurement even in high dynamic range scenarios.
Implementation Method 1
converts the returning light signal in a light receiver, in particular an APD (Avalanche Photo Diode), into an electrical reception signal
Implementation Method 2
the voltage drop in the supply of the light receiver during the reception of a light signal is used as an additional measurement signal
Data Source
Figure 1~2
Figure 3
AI summary
An optoelectronic sensor (10) for detecting objects in a monitoring area (20) is described, comprising a light transmitter (12) for emitting a light signal into the monitoring area (20), a light receiver (26) for converting the light signal (22) reflected or remitted by an object into an electrical received signal, an auxiliary circuit (38) for operating the light receiver (26), and an evaluation unit (32) configured to determine the received signal level and to derive object information from the received signal. The evaluation unit (32) is further configured to determine the received signal level from measurement information in the auxiliary circuit (36, 38).