Optical Position Sensor Packaging to Avoid Current Sensor Interference
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Solution Overview
Problem
Existing position sensors, particularly those using magnetic field sensing elements, suffer from accuracy degradation when integrated with current sensors due to mutual interference, and they lack efficient methods for determining the position of rotating or linearly moving targets with high precision and reliability.
Innovation Solution
A position sensor system incorporating an optical sensing element and image processor to capture images of a visual mark on a target, coupled with a current sensor to measure electrical current, and a motor controller, all encapsulated in a semiconductor package with a light transmissive portion to enable accurate position determination without interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If magnetic field sensing elements are integrated with current sensors in the same package, then device integration and compactness are improved, but measurement precision deteriorates due to mutual interference between the sensors
Solution Approach 1:
The sensor package is segmented into distinct functional regions: an optical sensing region for position detection and a current sensing region for electrical measurement. This spatial segmentation prevents mutual interference between optical and magnetic field sensing elements while maintaining compact integration, directly resolving the contradiction between integration and measurement precision
Solution Approach 2:
A magnetic shield or Faraday cage structure acts as an intermediary barrier between the optical sensing elements and current sensing elements. This intermediary component blocks magnetic field interference from the current sensor from affecting the optical position sensor, enabling accurate simultaneous operation of both sensor types in an integrated package
2Measurement precision
If optical sensing elements are used for position detection, then measurement precision is improved, but device complexity increases due to additional optical components and light transmissive package requirements
Solution Approach 1:
The optical position sensing system and current sensing system are merged into a single integrated semiconductor package. The package combines optical components (lens, photodetector array), processing circuitry, and current sensing elements in one unified structure, reducing overall system complexity despite the advanced functionality provided
Solution Approach 2:
The integrated sensor package performs multiple functions simultaneously: optical position detection, current measurement, and signal processing. This multi-functionality eliminates the need for separate discrete components and reduces system-level complexity, making the increased internal integration worthwhile for achieving high precision
3Reliability
If the semiconductor package encapsulates all sensing elements, then protection and reliability are improved, but light transmission to the optical sensing element becomes restricted
Solution Approach 1:
The semiconductor package exhibits local quality variations: most of the package provides protective encapsulation, while a specific region (the light transmissive portion) is designed with optically transparent or translucent material. This localized transparency allows sufficient light transmission to the optical sensing element while maintaining protection elsewhere in the package structure
Solution Approach 2:
The package uses composite material construction combining protective materials (epoxy, plastic) with light-transmissive materials (glass, transparent polymer) in strategic locations. This composite approach maintains the protective benefits of encapsulation while enabling the optical function to operate effectively through the transmissive portion
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 system provides precise and reliable position feedback for rotating or linearly moving targets, maintaining sensor accuracy by avoiding mutual interference and enabling integration with current sensors, suitable for applications requiring high precision and redundancy.
Implementation Method 1
an optical sensing element and an image processor, the image processor being configured to use the optical sensing element to take images of a visual mark
Implementation Method 2
a semiconductor package that is configured to encapsulate the position sensor, the current sensor, and the motor controller, the semiconductor package including a light transmissive portion that is configured to pass through light originating from outside of the package to the optical sensing element
Implementation Method 3
a current sensor including one or more magnetic field sensing elements, the current sensor being configured to measure a level of electrical current through a conductor
Data Source
AI summary
A device, comprising: a position sensor including an optical sensing element and an image processor, the image processor being configured to use the optical sensing element to take images of a visual mark that is formed on a target, detect a position of the target based on the images, and generate a first signal that is indicative of the position of the target; a current sensor including one or more magnetic field sensing elements, the current sensor being configured to measure a level of electrical current through a conductor, and generate a second signal that is indicative of the level of the electrical current through the conductor; and a motor controller that is configured to receive the first and second signals and generate a third signal for powering an electric motor, the third signal being generated based on the first and second signals; and a semiconductor package.