Collimator Lens for Laser Diode Light Source Unit
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Solution Overview
Problem
Conventional projectors using laser diodes face challenges in achieving uniform light intensity distribution due to the elliptical cross-sectional shape of laser rays, leading to inefficient light utilization and potential enlargement of the projector size, as well as non-uniform emission angles that can affect the utilization of laser rays.
Innovation Solution
A light source unit with a collimator lens having an entrance portion with an elongated recess curved inward and an exit portion formed into a convex shape, which aligns the major axis of the elliptic cross-section of the laser diode with the incident light axis, allowing for a circular cross-sectional shape and symmetrical exit angles, thereby expanding the shining range of the laser ray while maintaining a compact projector size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the number of microlenses through which a laser ray passes is increased by expanding the shining range of the laser ray with a collimator lens, then the uniformity in intensity distribution is improved, but a large collimator lens is needed which calls for an enlargement in size of the projector
Solution Approach 1:
The collimator lens applies different optical powers in different directions: a first optical power in the first direction (major axis of elliptic cross-section) and a second optical power in the second direction (minor axis). This anisotropic optical design allows the lens to expand the shining range selectively along the major axis where expansion is most needed, while maintaining a compact overall lens size and avoiding projector enlargement.
2Manufacturing precision
If small microlenses are used for the microlens array to enhance the uniformity in intensity distribution of a laser ray, then the uniformity is improved, but the loss of transmitted light is increased resulting in a reduction in light utilization efficiency
Solution Approach 1:
The collimator lens performs preliminary expansion of the laser ray's shining range before the light reaches the microlens array. By pre-expanding the beam diameter in the first direction using the first optical power, the laser ray covers more microlenses, distributing light more uniformly without requiring smaller microlenses that would cause higher connection losses.
3Device complexity
If an elliptic cross-sectional shape of laser ray is not corrected, then the device complexity is reduced, but the emission angle is not uniform which affects the utilization of laser ray
Solution Approach 1:
The collimator lens combines two optical functions into a single element: it acts as a collimator to parallelize the laser ray while simultaneously functioning as a cylindrical lens to reshape the elliptic cross-section into a more uniform profile. This merged design achieves uniform emission angles without adding separate optical components, maintaining device simplicity.
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 ensures uniform emission angles and increased light utilization efficiency, allowing for a wider shining range without enlarging the projector, resulting in improved image projection quality and reduced size.
Implementation Method 1
a collimator lens having an entrance portion and an exit portion; wherein light emitted from the laser diode is defined as incident light which is caused to enter the collimator lens
Data Source
AI summary
A light source unit includes a laser diode and a collimator lens having an entrance portion and an exit portion, with light emitted from the laser diode being incident light which is caused to enter the collimator lens. The laser diode is disposed so that a direction of a major axis of an elliptic cross section which intersects an axis of the incident light at right angles is defined as a direction of a first axis, and the entrance portion includes an elongated recess portion which is formed into a recess shape which is curved inwards towards a direction in which the incident light exits. In addition, a recessed edge of the elongated recess portion in a cross section, which intersects the first axis at right angles, is formed into an arc shape, and the incident light which enters the entrance portion is caused to exit from the exit portion.