Image Sensor North Orientation Initialization Using Digital Offset
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Solution Overview
Problem
Existing North seekers face challenges in achieving precise initialization and updating of geographic North orientation due to parasitic movements and the need for costly precision accelerometers, with current methods being ad-hoc and prone to errors when the device is moved.
Innovation Solution
A method utilizing a digital image sensor to determine the offset between images, allowing discrimination of Earth's rotation from parasitic movements, thereby eliminating the need for a precision accelerometer and enabling accurate initialization and updating of North orientation using a gyrometric North finder rigidly attached to the image sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a precision accelerometer is used to discriminate parasitic movements from Earth's rotation, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces the mechanical/physical sensor approach (precision accelerometer) with an optical/image-processing approach. By capturing images at multiple instants and computing the offset between them, the system determines angular movement without requiring additional precision accelerometers, thus reducing device complexity while maintaining measurement precision.
Solution Approach 2:
The patent introduces an intermediary element (the image sensor and image processing system) to mediate between the gyrometer and the ground. Instead of directly measuring parasitic movements with an accelerometer, the system uses image offset computation as an intermediary method to infer angular movement, thereby eliminating the need for the precision accelerometer.
2Device complexity
If initialization is performed ad-hoc, then device complexity is reduced, but reliability deteriorates when the device is moved
Solution Approach 1:
The patent transforms the ad-hoc initialization process into a continuous operation. By continuously capturing images and computing offsets between successive images, the system continuously updates orientation information, ensuring reliability even when the device is moved. This continuous useful action replaces the one-time ad-hoc initialization.
Solution Approach 2:
The patent implements a feedback mechanism where the computed offset from image comparison is fed back into the orientation value update process. The gyrometer's orientation measurement is continuously adjusted based on the image offset information, creating a feedback loop that maintains reliability during device movement.
3Ease of manufacture
If image processing is used to determine offset, then manufacturing cost is reduced, but measurement precision may be affected
Solution Approach 1:
The patent uses optical copying through image capture to represent the physical scene at different instants. By copying the scene into digital images and computing the offset between these copies, the system achieves a cost-effective method that maintains measurement precision through digital image processing rather than expensive physical sensors.
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 provides precise and cost-effective initialization and updating of North orientation, achieving milli-radian accuracy by using image processing to measure parasitic movements and Earth's rotation, allowing the system to maintain valid North information for extended periods without resetting.
Implementation Method 1
The identification of North with a gyrometer seeker is based on a process of measuring the component of the earth's rotation vector in a horizontal plane
Implementation Method 2
the offset of two images from the digital image sensor is determined at a first instant and at a second distinct instant to constitute information representative of an angular movement
Implementation Method 3
the determination of the offset of the two images is ensured by an image processing of the type used for image stabilization
Data Source
AI summary
The invention relates to a method for updating and/or for initializing, in a system comprising an image sensor oriented towards the horizon such as a pair of binoculars coupled to a geographical north seeker incorporating a gyrometer, a value representative of the orientation of the image sensor with respect to north, in which the shift of two images arising from the digital image sensor is determined at a first instant and at a second instant that are distinct so as to construct an item of information representative of an angular movement, and in which this angular movement information is utilized to: update the value of orientation of the image sensor; - and/or to discriminate the movements of the image sensor with respect to the ground from the movements of the image sensor that are due to the rotation of the earth, in a process for initializing the value of orientation of the image sensor using a north seeker of gyroscopic or gyrometric type rigidly tied to the image sensor.