LED Projector Lens
Reliving moments by watching family videos is now possible with the help of projectors. These devices are becoming increasingly popular for home use.
A good led projector lens has only one primary job-to produce enough light that conforms to road safety rules. So how do we achieve that? A simple optical system consists of a WLLED, an elliptical reflector, and a light stop is proposed.
The Fresnel Lens
In 1822 French civil engineer Augustin-Jean Fresnel invented a lens that revolutionized the way light was used in lighthouses. The first-order Fresnel lens consisted of rings of glass prisms with a central bullseye that worked like a magnifying lens to concentrate the light into a powerful beam. Today you’ll find a similar concept in the lenses of movie projectors, spacecraft and even the lights on your car.
In addition to being an incredible source of light, Fresnel lenses are also quite durable. They’re extremely thin and lightweight, yet they can withstand significant weather conditions and high temperatures. They are available in a wide range of shapes and sizes, making them perfect for virtually any application that requires a positive-index optical lens.
Moreover, Fresnel lenses are ideal for solar concentration, solar cell heat collection and overhead projection applications, as well as any non-imaging light focusing. The groove-like microstructures of a Fresnel lens provide individual refracting surfaces that can be tuned to meet specific performance requirements.
To manufacture a micro-Fresnel, it’s necessary to use lithographic techniques that can produce functional surfaces with feature heights that are in the millimeter range. This paper presents an overview of the current state-of-the-art in micro machining technology that led projector lens is capable of developing functional surfaces with the required geometry. It then describes several lithographic processes that are employed to fabricate micro-Fresnel lenses, as well as the challenges that remain in this exciting area of technology.
The Two Lens Collimator
The double freeform lens design presented in this paper provides a simple, yet effective way to collimate light emitted by commercial UV-LEDs. In this study, the lens surface profiles were characterized mathematically by polar coordinates and their performance was evaluated using Zemax simulations for the chosen NCSU276A UV-LED. The simulation results confirmed that the lens could perfectly collimate rays from the point source at a single, zero-divergent angle.
Unlike conventional positive meniscus lenses, which consist of two spherical lens surfaces and can only provide a limited number of collimating angles, the proposed freeform lens design is a much more flexible solution. In addition to providing a wide range of collimating angles, the proposed lens also ensures that around half of the total LED light intensity is provided by rays at all larger radiation angles, as opposed to just paraxial rays (Figure 4).
Moreover, because the surface of the lens is completely open and exposed, it is easy to clean and maintain, which greatly reduces maintenance costs. Moreover, it can be made from inexpensive materials such as poly(methyl methacrylate) (PMMA). Its compact design makes it easy to integrate into existing headlights without the need for complicated optical adapters. It is the perfect solution for applications where the distance between the fiber end-face and the collimating optics needs to be adjusted.
The Three Lens Collimator
With the advent of advanced LEDs, the projector lens is now made of high-temperature-resistant plastic instead of metal. This is for the sake of cost-saving and it will still be able to work for long-term usage. However, there are some people who are still worried about the quality of the lens. This is why it is important to buy your lens from a reputable manufacturer.
The collimating lens is a crucial sub assembly for many optical systems such as spectrometer, beam-expander system, display measuring system, laser illumination system and sensor testing equipment. It helps to ensure that the source of light is properly collimated so that it produces a parallel light beam with the desired spatial resolution.
It is also possible to design a three-dimensional freeform lens using the simultaneous multiple surface method. This type of lens is more efficient and has a narrower angle of divergence than the conventional multi-convex lenses.
To illustrate the advantages of this design, we characterized the performance of a commercial straight cylindrical lens (LJ1598L2-C) and a dedicated 3D printed curved lens. The results show that the 3D printed curved lens can provide better beam steering at large angles. It has a Rayleigh range about four times larger and a divergence angle that is about twice smaller than the commercial lens. Moreover, it can significantly reduce side lobes.
The Plastic Optical Lens
Plastic optical lenses are grabbing more demand than glass variants as they are inexpensive, lighter in weight and offer shatter resistance. These lenses are also tintable and can be easily adapted to a range of prescriptions. They are also resistant to glare and have a good range of coatings. However, they do not provide the same clarity and anti-scratch properties as glass lenses.
Acrylic polymers like CR-39 are commonly used. These have a low native stress birefringence and can withstand high led projector lens temperature distortion. They are highly scratch resistant but do not resist ultraviolet rays. Polycarbonate is another popular choice for optics. It is a very tough and impact resistant material, but does not allow for the use of rimless frames. It can be tinted but does not accept UV rays.
Trivex is a newer form of optical plastic that offers a higher refractive index than CR-39, and therefore, better optical quality. This is especially important for lenses that require a high degree of correction. However, these types of lenses do tend to suffer from chromatic aberrations, so they should be coated with an AR (anti-reflective) layer to help reduce this effect.
Most people do not fully understand the pros and cons of different lens materials when they are choosing their eyeglasses, and rely on the advice of their optician. However, with a bit of research, it is possible to find the ideal lens for your needs.
