Rotating Mirror Sensor for Automatic Door Scanning
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Solution Overview
Problem
Existing sensors for automatic doors and gates fail to effectively monitor objects during the opening operation, particularly when a sliding door opens against a wall, as they primarily focus on the main closing edges and lack precision in scanning the area parallel to the door plane.
Innovation Solution
A sensor system utilizing a rotating mirror with multiple reflecting facets and optical paths that create a scanning field of over 180°, allowing for precise detection of objects by evaluating the time-of-flight of light pulses and providing a control signal to the door controller to manage door behavior, thereby enhancing safety during both opening and closing operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a rotating mirror with multiple facets and dual optical paths is used to achieve a scanning field of over 180°, then the scanning area parallel to the door plane is improved, but the device complexity increases
Solution Approach 1:
The rotating mirror is divided into multiple facets (at least three different reflecting emitting mirror facets) arranged around the rotational axis. Each facet can be independently oriented to reflect light pulses into different directions, enabling the system to achieve a wide scanning field of over 180° by segmenting the reflection function across multiple surfaces rather than requiring a single complex mirror configuration.
Solution Approach 2:
The patent introduces a second optical path in addition to the first optical path, creating a three-dimensional spatial arrangement of optical components. The two optical paths are positioned at different locations and angles, with their incident beam projections intersecting at an angle of less than 160°. This dimensional arrangement allows the system to cover a wider scanning area by utilizing spatial distribution of light sources and reflection paths.
2Area of stationary object
If the incident beam projections intersect at an angle of less than 160°, then the scanning field exceeds 180°, but the positioning precision of optical components becomes more difficult
Solution Approach 1:
The patent incorporates evaluation units that detect objects in the scanning field and provide feedback signals to the control unit. The system evaluates the time-of-flight of light pulses to determine object positions and provides feedback for adjusting the scanning operation. This feedback mechanism enables precise positioning and detection despite the complex geometric arrangement of optical components with intersecting beams at angles less than 160°.
Solution Approach 2:
The patent replaces mechanical positioning systems with optical detection and evaluation methods. Instead of relying on mechanical precision for positioning optical components, the system uses light pulse time-of-flight measurement and electronic evaluation to achieve precise object detection. The control unit processes detection signals electronically to determine object positions with high accuracy, substituting mechanical precision requirements with optical measurement capabilities.
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 sensor system provides a high-resolution, large-scanning-range capability, enabling effective monitoring of the entire door area, including secondary closing edges, and preventing accidents such as pinching between the door and the wall during opening, while maintaining a compact device size.
Implementation Method 1
The rotating mirror has at least three different reflecting emitting mirror facets arranged around its rotational axis. The light-pulse generation unit generates light-pulses which are reflected by the mirror facets. The two emitting optical paths define an incident pulse direction that is the direction of the pulse with which it hits the mirror.
Implementation Method 2
The sensor works based on pulse echo evaluation of a light-pulse, preferably by evaluating the time-of-flight of emitted and echoed light-pulses, to determine the distance of an object relative to the sensor.
Implementation Method 3
The light-pulses are sent towards the rotating mirror via two different emitting optical paths. Each of the different emitting optical paths comprises at least one optical component. Especially emitters, lenses and mirrors are understood as optical components.
Data Source
AI summary
A sensor for automatic doors or gates that works based on a pulse-echo evaluation comprises a rotating mirror having at least three different emitting mirror facets, where the rotational axis lies normal to a reference plane, and at least one light-pulse generation unit generating infrared pulses having a certain beam width. The pulses are sent along two different emitting optical paths, each having at least one optical component, where the emitted pulses can be reflected by the mirror facets, and the emitting optical path defines an incident pulse direction of the emitted pulses. The reflected pulses establish a scanning field, where each of the reflected pulse directions defines a reflected beam projection on the reference plane (R), where the angle (IA) between the projections of the incident beams, namely the projection of the incident pulse directions onto the reference plane, is between 30° and 160°. The rotational axis (A) lies on the bisectrix (BS) of the beam projections between the intersection plane and the optical component closest to the rotating mirror along the optical path. The rotating mirror and its rotational axis (A) are set such that each reflected beam projection from both incident optical paths has an innermost reflected pulse (IB) at least parallel to the bisectrix (BS) or even crossing the bisectrix (BS) on the side of the scanning field. The scanning field is delimited by two outermost reflected pulses (OBa, OBb), where the scanning field therebetween has an angular range of more than 150°. The rotating mirror has the same amount of receiving mirror facets as the emitting mirror facets. The reflected pulse is echoed back by an object in the scanning field where the echoed pulse is reflected by the receiving mirror facet and then received by a receiver such that it is distinguishable over which emitting optical path the emitted pulse of the echoed pulse was sent.