Safety Zone Monitoring with TOF Reference Distance Detection
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Solution Overview
Problem
Existing optoelectronic protective devices using time-of-flight sensors struggle to reliably detect objects smaller than their depth resolution, particularly in the vicinity of the protection area boundary, requiring complex and costly sensors to detect objects the size of a finger or smaller.
Innovation Solution
The device employs a time-of-flight sensor system where light beams are reflected or remitted at a reference element farther away than the delimiting element, ensuring a distance difference greater than the sensor's depth resolution, allowing for reliable detection of objects smaller than the sensor's resolution using less complex and inexpensive sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If time-of-flight sensors with sufficient depth resolution are used to detect objects smaller than 20 mm, then detection reliability improves, but device complexity and cost increase significantly
Solution Approach 1:
A reference element is introduced as an intermediary object at a known second distance from the sensor. This reference element provides a stable reference measurement that enables the calculation of depth differences without requiring the sensor itself to have high depth resolution. The reference element acts as a mediator that transforms the measurement problem from direct depth measurement to relative distance calculation.
Solution Approach 2:
The system transitions from relying solely on the sensor's depth resolution capability to using spatial arrangement in multiple dimensions. By positioning both a delimiting element and a reference element at different distances from the sensor, the system creates a geometric configuration where depth information is derived from the spatial relationship between multiple elements rather than from the sensor's intrinsic depth resolution.
2Reliability
If time-of-flight sensors with sufficient depth resolution are used to detect objects smaller than 20 mm, then detection reliability improves, but cost increases significantly
Solution Approach 1:
The reference element serves as a cost-effective intermediary that enables high detection reliability without requiring expensive high-resolution sensors. By using simple reflective or remitting materials for the reference element, the system achieves accurate small object detection through geometric arrangement rather than through costly sensor technology.
Solution Approach 2:
The reference element can be implemented using inexpensive materials such as reflective foils or simple remitting structures. These cheap reference elements replace the need for expensive high-resolution sensors, making the overall system more cost-effective while maintaining the ability to detect small objects reliably.
3Length of stationary object
If the reference element is positioned close to the delimiting element, then the monitored area is compact, but detection reliability decreases due to limited depth resolution
Solution Approach 1:
Instead of relying on the sensor's depth resolution to distinguish between closely spaced objects, the system uses the spatial dimension by positioning the reference element at a greater distance. This creates a measurable distance difference that can be reliably detected even with standard depth resolution, allowing the monitored area to remain compact while maintaining detection reliability.
Solution Approach 2:
The system pre-establishes a geometric configuration where the reference element is positioned at a calculated distance that ensures sufficient distance difference for reliable detection. This preliminary spatial arrangement is designed to work with the sensor's known depth resolution capabilities, ensuring detection reliability before actual measurement begins.
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 reliable detection of objects as small as a finger, reducing the complexity and cost of the sensor system while ensuring accurate intrusion detection, even when the object's size is less than the sensor's depth resolution.
Implementation Method 1
at least one time-of-flight sensor (14) with at least one transmitter (16) for emitting light rays (24) into the protected area (12) and with at least one receiver (18) for receiving light rays (28) reflected or remitted from the protected area (12)
Implementation Method 2
light beams which are reflected or remitted at a reference element farther away than the delimiting element
Data Source
Figure 1~2
AI summary
A device for monitoring a protected area is described, comprising at least one time-of-flight sensor, which has a transmitter for emitting light beams into a protected area and a receiver for receiving reflected or remitted light beams, an evaluation unit for determining the time of flight between the emission and reception of the light beams, and a monitoring unit for generating an interruption signal if the determined time of flight deviates from a predetermined maximum time of flight by at least a predetermined threshold value, a boundary element opposite the time-of-flight sensor at a first distance and at least partially limiting the protected area, and a reference element opposite the time-of-flight sensor at a second distance for reflecting or remitting the emitted light beams, wherein the second distance is greater than the first distance.