ToF Distance Measurement With Optical-Axis Deviation Correction
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Solution Overview
Problem
Existing distance measurement technologies using a time-of-flight method with a vertical cavity surface emitting layer (VCSEL) and a ToF sensor suffer from errors due to misalignment of optical axes, especially when using large lenses, leading to inaccurate distance measurements.
Innovation Solution
A distance information acquisition device that includes an irradiation unit, a ToF sensor, and a correcting arithmetic operation unit, which uses a numerical expression and correction values to calculate distance information by considering the angle of view and optical path lengths, and adjusts for deviations between the optical axis of the lens and the irradiation unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a large lens (with large barrel diameter and long barrel length) is used, then the field of view and imaging quality are improved, but the gap between the optical axis of the lens and the optical axis of the irradiation unit increases, causing measurement errors
Solution Approach 1:
The patent replaces the mechanical alignment approach (physically aligning optical axes) with a computational correction approach. The correction arithmetic operation unit calculates and corrects distance measurement errors based on the known gap distance between optical axes, eliminating the need for precise mechanical alignment while enabling use of larger lenses.
2Measurement precision
If the optical axis of the lens and the optical axis of the irradiation unit are disposed to match, then measurement errors due to axis deviation are reduced, but it cannot accommodate objects located away from the optical axis center where first and second optical path lengths differ
Solution Approach 1:
The patent changes the computational parameters used in distance calculation. Instead of assuming equal optical path lengths, the system calculates separate first and second optical path lengths based on the object's position and the geometric relationship between components, then uses these differentiated parameters to compute accurate distances for objects anywhere in the field of view.
3Device complexity
If the first optical path length and the second optical path length are considered as the same distance, then the calculation is simplified, but measurement errors occur when objects are not located at the optical axis center
Solution Approach 1:
The patent performs preliminary calculation of the first and second optical path lengths based on the object's position and system geometry before computing the final distance. This pre-computation of path lengths allows the system to maintain accurate measurements for off-axis objects while keeping the overall calculation process systematic and manageable.
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
Enables accurate distance measurement by correcting for optical axis deviations, allowing the use of larger lenses and improving the precision of distance calculations.
Implementation Method 1
measures the distance to an object by measuring the time from emission of light from the light emitting element to reception of light by the ToF sensor through reflection by the object
Implementation Method 2
receive light emitted from the irradiation unit and reflected by the object via an optical-system lens
Data Source
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AI summary
A distance information acquisition device includes an irradiation unit configured to irradiate an object with light and a time of flight (ToF) sensor configured to receive light emitted from the irradiation unit and reflected by the object via an optical-system lens and acquires distance information for the object. The distance information acquisition device further includes: a distance value acquiring unit configured to acquire a distance value on the basis of a timing at which emission of light is performed by the irradiation unit, a timing at which light is received by the ToF sensor, and the speed of light; a storage unit configured to store a predetermined numerical expression including at least information on an angle of view of the optical-system lens as a parameter; and a correcting arithmetic operation unit configured to calculate the distance information for the object by applying the acquired distance value to the predetermined numerical expression stored in the storage unit.