TOF Distance Measurement Device External Light Illuminance Calculation
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Solution Overview
Problem
Conventional TOF cameras face significant challenges in distance measurement accuracy due to external light, as they are not designed to measure illuminance at the spectral sensitivity relevant to their operation, leading to saturation issues and inaccurate distance calculations, especially when objects with varying reflectivity enter the measurement space.
Innovation Solution
A distance measurement device equipped with a light emission unit, optical filter, and external light illuminance calculation unit that measures external light illuminance at the spectral sensitivity of the optical filter, allowing for accurate calculation of external light illuminance based on charge amounts and object reflectivity, enabling continuous monitoring during operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external light illuminance is not measured at the spectral sensitivity of the optical filter, then the device complexity is reduced, but the distance measurement accuracy deteriorates due to saturation and shot noise
Solution Approach 1:
The light reception unit performs dual functions: it receives reflected measurement light for distance calculation and simultaneously receives reflected external light for illuminance measurement. By utilizing the same hardware component for multiple purposes, the patent avoids adding separate illuminance measurement devices, thereby maintaining distance measurement accuracy without significantly increasing device complexity
Solution Approach 2:
The patent measures external light illuminance at the specific spectral sensitivity of the optical filter, which is a parameter optimized for the distance measurement function. This parameter alignment ensures that the illuminance measurement directly reflects the conditions affecting distance measurement accuracy, resolving the contradiction between measurement precision and device complexity
2Device complexity
If the light reception unit receives both reflected measurement light and reflected external light, then the device structure is simplified, but the light reception unit becomes saturated under strong external light
Solution Approach 1:
The system continuously monitors external light illuminance levels and uses this feedback information to determine whether distance measurement should be performed. When external light exceeds threshold levels that would cause saturation, the system appropriately responds by avoiding measurements or adjusting operation, thereby maintaining reliability while keeping the light reception structure simple
Solution Approach 2:
The patent performs preliminary measurement of external light illuminance before conducting distance measurement. This preliminary action allows the system to assess whether conditions are suitable for accurate measurement, preventing saturation-related errors while maintaining a simple light reception structure that receives both measurement and external light
3Ease of operation
If conventional illuminance measurement methods are used, then the measurement approach is simplified, but the measurement does not account for the spectral sensitivity of the optical filter
Solution Approach 1:
The distance measurement device performs its own illuminance measurement function using its existing light reception unit and spectral characteristics. By serving its own illuminance measurement needs, the device ensures that the measurement is precisely aligned with its operational spectral sensitivity without requiring external specialized equipment, thus achieving both ease of operation and measurement precision
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 device can accurately measure external light illuminance, preventing saturation and ensuring stable distance measurement accuracy, even in environments with strong external light, by accounting for the spectral sensitivity and reflectivity of objects, thus enhancing operational reliability.
Implementation Method 1
light-receiving elements generate so-called 'shot noise' when detecting the number of photons by the photoelectric effect
Data Source
AI summary
A distance measurement device includes a light emission unit which is capable of emitting measurement light to be irradiated toward an object, a light reception unit configured to receive light from the object via an optical filter through which light having the same wavelength band as the measurement light passes, a distance calculation unit configured to calculate a distance to the object based on each charge amount obtained by accumulating a charge corresponding to the received light at a plurality of timings which are delayed by a predetermined phase with respect to emission timing of the measurement light, and an external light intensity calculation unit configured to calculate external light illuminance of external light illuminating the object at the spectral sensitivity of the optical filter based on the charge amounts acquired at the light reception unit and a reflectivity of the object.