Laser Diode Drive Control Using Offset Light Compensation
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Solution Overview
Problem
Existing driving devices for light-emitting elements, such as laser diodes, fail to accurately set bias and target currents due to the influence of background light, leading to errors in light emission and potential misdriving of the elements.
Innovation Solution
A driving device and method that includes a setting section to determine the offset light amount when the light-emitting element does not emit light, allowing for the accurate setting of bias and target currents, and an output controller to control the driving current based on these settings, thereby accounting for background light and ensuring proper light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a threshold current of the LD is calculated by means of the invention of PTL 1, then the calculation process is simple, but the influence of background light causes an error in a calculation result
Solution Approach 1:
The patent applies preliminary action by detecting and storing the offset light amount (background light) before calculating the threshold current. The light-receiving element detects the offset light amount when the LD does not emit light, and this detected value is stored as offset information. This preliminary detection eliminates background light interference from subsequent threshold current calculations, thereby improving calculation accuracy without significantly increasing system complexity.
2Adaptability or versatility
If the LD is installed in a position that allows laser light to be outputted to the outside, then the ranging function is enabled, but background light exists around the LD causing errors
Solution Approach 1:
The patent converts the harmful background light into a useful measurement parameter. By detecting the offset light amount caused by background light and using it to compensate for subsequent light-receiving power measurements, the system transforms the interference into a correction factor. This allows the LD to be installed in positions enabling ranging functionality while maintaining measurement accuracy despite the presence of background light.
3Measurement precision
If the offset light amount detection is performed, then the threshold current calculation accuracy is improved, but the measurement time increases
Solution Approach 1:
The offset light amount detection is performed as a preliminary step before threshold current calculation and can be stored for reuse. This preliminary measurement of background light is conducted once, and the resulting offset value is stored as offset information that can be applied to multiple subsequent measurements, thereby improving accuracy while minimizing the time penalty to a single initial measurement.
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 enables precise setting and control of bias and target currents, preventing errors in light emission and ensuring the light-emitting element is driven appropriately, improving the accuracy of distance measurements and reducing delays in light emission.
Implementation Method 1
a light-receiving element that receives a portion of the output light
Data Source
AI summary
The present invention relates to a driving device, a driving method, and a light-emitting unit that make it possible to appropriately drive a light-emitting element.The driving device according to the present invention includes: a setting section (161) that sets at least one of a bias current of a light-emitting element (an LD 121) or a target current for setting output light from the light-emitting element (the LD 121) to desired intensity on the basis of a result of detection of an offset light amount when the light-emitting element (the LD 121) does not emit light; and an output controller (164) that controls an output of a driving current of the light-emitting element (the LD 121) on the basis of at least one of the set bias current or the set target current. The detection of the offset light amount is performed by a light-receiving element (a PD 122) that receives a portion of the output light.The present invention is applicable to a ranging module, for example.