Angle-of-View Compensation for ToF Distance Measurement Errors
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Solution Overview
Problem
Existing distance measurement technologies using ToF methods suffer from errors due to misalignment of optical axes between the lens and irradiation unit, particularly with larger lenses, leading to inaccuracies in distance calculations.
Innovation Solution
A distance information acquisition device that includes a correcting arithmetic operation unit to calculate distance information using a predetermined numerical expression, considering the angle of view of the optical-system lens and storing correction values to correct for deviations between the optical axes, allowing for high-accuracy measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large lens (with large barrel diameter and long barrel length) is used in the related art, 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 distance measurement errors to increase
Solution Approach 1:
The patent replaces the mechanical alignment approach (physically aligning optical axes) with a computational approach. The arithmetic operation unit calculates correction values based on the known angle of view and geometric relationships, then applies these corrections to the measured distance data, eliminating the need for precise mechanical co-alignment of optical axes
Solution Approach 2:
The patent changes the parameter used for distance calculation from a simple time-of-flight division by 2 to a corrected value that accounts for the angular deviation. By introducing the angle of view parameter and calculating the actual optical path difference, the system compensates for the misalignment without requiring physical realignment
2Ease of operation
If the optical axis of the lens and the optical axis of the irradiation unit are disposed to match, then alignment is simplified, but when the object is not located at the optical axis center, the first optical path length and the second optical path length are different, causing distance measurement errors
Solution Approach 1:
The patent replaces the assumption of equal optical path lengths (mechanical symmetry assumption) with a computational correction model. The arithmetic operation unit calculates the actual different path lengths based on the angle of view and object position, replacing the need for symmetric optical path design
Solution Approach 2:
The patent introduces an intermediary computational step (the arithmetic operation unit) that mediates between the raw time-of-flight measurement and the final distance calculation. This intermediary calculates correction values based on the angle of view and applies them to compensate for the unequal optical path lengths
3Device complexity
If the related art method of dividing time-of-flight by 2 is used, then the calculation is simple, but distance measurement errors occur when first and second optical path lengths differ
Solution Approach 1:
The patent changes the calculation parameter from a fixed division by 2 to a dynamic correction value that depends on the angle of view and object position. The arithmetic operation unit computes this correction based on geometric relationships, providing accurate results without excessive computational complexity
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, improving measurement precision and reducing errors in distance calculations.
Implementation Method 1
a light emitting element such as a vertical cavity surface emitting layer (VCSEL) and a light receiving element such as a ToF sensor at positions around a lens of an imaging device and 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
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 3
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
Data Source
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.