Aspheric Condenser Lenses with Diffuser Surface

Table 1.2  General Specifications
Substrate	B270 Optical Crown Glass
Wavelength Range	Uncoated: 380 - 2100 nm A: 350 - 700 nm B: 650 - 1050 nm
Reflectance Over AR Coating Range for Coated Optics (Avg., AOI = 0°)	Ravg < 0.5%
Focal Length Tolerance	±8%
Design Wavelength	Visible
Surface Quality (Asphere Side)	80-50 Scratch-Dig
Uncoated Transmission Graph (Click Here to Download Raw Data)
A Coating Reflectance Graph (Click Here to Download Raw Data)
B Coating Reflectance Graph (Click Here to Download Raw Data)
Diameter Tolerance	+0.0 mm / -0.5 mm
Center Thickness Tolerance	±0.3 mm
Centration	<30 arcmin
Temperature (Max)	250 °C (482 °F)

Click to Enlarge
Figure 1.1  Light from an LED Collimated by a Non-Diffusing Condenser Lens

Click to Enlarge
Figure 1.3  Light from an LED Collimated by a Condenser Lens with a Diffuser Surface

Features

• Combines a Condenser and a Diffuser into a Single, Compact Optic
• 25 mm and 50 mm Diameters Available
• 600 or 1500 Grit Polished Versions Available
• 20 mm or 40 mm Focal Length Versions Available
• Available Uncoated or AR-Coated for 350 - 700 nm or 650 - 1050 nm on Aspheric Surface
• Offers Higher NA and Larger Aperture than Spherical Lenses

Thorlabs' Aspheric Condenser Lenses with Diffusers are designed for collimating light from lamps, LEDs, or similar sources into a highly uniform illumination pattern. We offer two sizes (Ø25 mm and Ø50 mm) to accommodate varying application needs. These lenses are available in either 600 grit or 1500 grit polished versions. A finer grit (e.g. 1500) has a small diffusion pattern, while a coarser grit (e.g. 120) will have a larger diffuser pattern. These aspheric condenser lenses are available uncoated for use in the 380 - 2100 nm range or with an AR coating for the 350 to 700 nm (-A Coating) or 650 to 1050 nm (-B Coating) range. For reflectance plots, please see Table 1.2.

When collimating high-power LEDs with a standard lens, the structure of the source can ultimately be imaged through the lens, resulting in a highly non-uniform illumination pattern (see Figure 1.1). For many applications, this is not desired. Adding a diffuser on the plano surface ensures a uniform illumination of the light source in the far field (see Figure 1.3).

The aspheric surface is precision molded on the aspheric side and polished with 600 or 1500 grit on the plano side. Polished diffusers are advantageous over sand blasted diffusers as their surfaces have greater uniformity.

Thorlabs offers many types of mounting solutions for these lenses. Extra-thick retaining rings are available with SM1 (1.035"-40) and SM2 (2.035"-40) threading that provide extra clearance for spanner wrenches when mounting these lenses (see the Lens Mounting Guide tab for more information). Please visit our Fixed Optic Mounts Guide and Mirror Mounts Guide for possible mouting options available.

Click to Enlarge
Figure 2.1
Reference Drawing

Aspheric Lens Design Formula

The aspheric surface of these lenses may be described using a polynomial expansion in Y, the radial distance from the optical axis. The surface profile or sagitta (often abbreviated as sag) is denoted by z, and is given by the following expression:

where R is the radius of curvature, k is the conic constant, and the A_n are the nth order aspheric coefficients. The sign of R is determined by whether the center of curvature for the lens surface is located to the right or left of the lens' vertex; a positive R indicates that the center of curvature is located to the right of the vertex, while a negative R indicates that the center of curvature is located to the left of the vertex. For example, the radius of curvature for the left surface of a biconvex lens would be specified as positive, while the radius of curvature for its right surface would be specified as negative.

Aspheric Lens Coefficients

Due to the rotational symmetry of the lens surface, only even powers of Y are contained in the polynomial expansion above. The target values of the aspheric coefficients for each product can be found in Table 2.2 or by clicking on the red documents icon () next to each lens sold below.