VCSEL Light Quantity Control via Blocking Members
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Solution Overview
Problem
Optical scanning apparatuses using VCSELs face challenges in controlling the light quantity of laser beams due to variations in far field patterns caused by driving current and temperature changes, leading to inconsistent light quantity ratios between the laser beam reaching the photosensitive member and the optical sensor.
Innovation Solution
The apparatus includes a light source, collimator lens, holding member, first and second light blocking members, a separation unit, optical unit, and a control unit, where the collimator lens converts the light beam into parallel light, and the light blocking members adjust the light beam to ensure consistent light quantity control by blocking portions of the beam, thereby stabilizing the light quantity ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the light quantity of the laser beam is controlled based on the detected light quantity from the optical sensor, then the light quantity control is improved, but the light quantity ratio varies due to FFP variation caused by driving current and temperature changes
Solution Approach 1:
A light quantity ratio adjustment mechanism is introduced as an intermediary component between the light source and the optical sensor. This mechanism includes a variable aperture or attenuator that can adjust the light quantity ratio independently, compensating for FFP variations caused by driving current and temperature changes. The adjustment mechanism ensures that the ratio of light quantity reaching the photosensitive member to light quantity detected by the optical sensor remains stable despite environmental variations.
2Adaptability or versatility
If the far field pattern varies with driving current and temperature, then the light source adaptability is improved, but the light quantity ratio consistency deteriorates
Solution Approach 1:
A feedback control system is implemented that continuously monitors the light quantity ratio and adjusts the light source driving parameters accordingly. The system uses the detected light quantity from the optical sensor to calculate the actual light quantity ratio and compares it with the target ratio. Based on the deviation, the control unit adjusts the driving current or temperature compensation parameters to maintain consistent light quantity ratio, thereby resolving the contradiction between adaptability and precision.
3Measurement precision
If the light beam is separated by a half mirror to detect light quantity, then the light quantity detection is improved, but the light quantity ratio control precision deteriorates due to FFP variation
Solution Approach 1:
An additional light quantity ratio adjustment mechanism is introduced as an intermediary component between the half mirror and the optical sensor. This mechanism includes a variable aperture or attenuator that can independently adjust the light quantity ratio, compensating for FFP variations. The adjustment mechanism ensures that the ratio of light quantity reaching the photosensitive member to light quantity detected by the optical sensor remains stable despite FFP changes caused by driving current and temperature variations.
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 configuration effectively reduces the variation in light quantity ratios, allowing for precise control of the light quantity reaching the photosensitive member, even with changes in far field patterns, ensuring accurate image formation.
Implementation Method 1
a collimator lens configured to convert the light beam emitted from the light source into parallel light
Implementation Method 2
a separation unit configured to separate the light beam passing through the first light blocking member into a transmitted light beam and a reflected light beam
Data Source
AI summary
A light beam emission apparatus separates, via a half mirror, apart of a laser beam emitted from a semiconductor laser towards a photosensitive member, guides the separated laser beam to an optical sensor to detect a light quantity, and controls the light quantity based on the detected result. The light beam emission apparatus includes a first light blocking member located between the semiconductor laser and the half mirror, and a second light blocking member located between the half mirror and the optical sensor.