Plano-Convex lenses are the best choice for focusing parallel rays of light to a single point. They can be used to focus, collect and collimate light. The asymmetry of this lens shape minimizes spherical aberration in situations where the object and image are located at unequal distance from the lens. The optimum case is where the object is placed at infinity with parallel rays entering lens and the final image is a focused point.

The lenses can be mounted in LT series lens tube for constructing a complex optical system or quickly connecting to other threaded lens mounts: A-Line™ series fixed lens mount, or adjustable lens positioner (with thread adapter). Use LT-WR series spanner wrench for easy lens installation.

N-SF11 is an excellent lens material for most visible and near infrared applications (400 nm to 2.5 µm). N-SF11 is one of the most common flint optical glass used in harsh environments making them ideal for use in biology or chemical labs, and provides great performance at a good value. Its high homogeneity, low bubble and inclusion content, and straightforward manufacturability make it a good choice for transmissive optics. N-SF11 is also relatively hard and shows good scratch resistance. Our high index N-SF11 lenses are polished to 40-20 scratch-dig surface quality and λ/4 P-V irregularity. Compared to typical N-BK7 and UV fused silica lenses, their high index and lower F/# values allow for more light collection at a shorter focal distance. 

Our broadband AR.16H antireflection coating improves the transmission efficiency of these lenses by reducing surface reflections over a 600-1050 nm wavelength range. The Visible multi-layer coating improves the performance over uncoated surfaces. It features a damage threshold of 7 J/cm‌² for 10 ns pulses at 10 Hz and 1064 nm.

For an application example, let’s look at the case of the output from a Newport N-LGP-173 HeNe laser focused to a spot using a SFPX040 Plano-Convex Lens. This Hene laser has a beam diameter of 0.79 mm and a divergence of 0.88 mrad. Note that these are beam diameter and full divergence, so in the notation of our figure, y₁ = 0.395 mm and θ₁ = 0.44 mrad. The SFPX040 lens has a focal length of 12.7 mm. Thus, at the focused spot, we have a radius θ₁f = 5.6 µm. So, the diameter of the spot will be 11.2 µm.

Since a common application is the collimation of the output from an Optical Fiber, let’s use that for our numerical example. The Newport F-MBB fiber has a core diameter of 200 µm and a numerical aperture (NA) of 0.37. The radius y₁ of our source is then 100 µm. NA is defined in terms of the half-angle accepted by the fiber, so θ₁ = 0.37. If we again use the SFPX040 , 12.7 mm focal length lens to collimate the output, we will have a beam with a radius of 9.4 mm and a half-angle divergence of 7.9 mrad.