Optical design of the Fresnel lens for LED-driven flashlight.

Area of Science:

• Optical engineering
• Materials science
• Photonics

Background:

• Fresnel lenses with micrometer-sized v-groove structures are vital for LED flashlights in high-quality photography.
• The fabrication quality and geometrical accuracy of these structures directly influence optical performance, specifically illuminance and brightness uniformity.

Purpose of the Study:

• To present a systematic design procedure for fabricating Fresnel lenses.
• To investigate the impact of geometrical design and fabrication processes on the optical performance of Fresnel lenses.

Main Methods:

• Optical analysis was conducted using commercial TracePro software.
• Simulations and experimental results were used to evaluate lens performance.

Main Results:

• A smaller tip radius in the v-groove microstructure was found to enhance brightness uniformity.
• Fabrication via injection molding or injection compression molding resulted in significant errors (3%-6% height, >6% curvature).

Conclusions:

• Fabrication errors in Fresnel lenses significantly affect optical performance, particularly brightness uniformity.
• Optimizing microstructure design and minimizing fabrication defects are critical for achieving high-performance Fresnel lenses for photographic applications.