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Diffraction-limited and very cost effective, a precision-molded glass aspheric lens is an attractive compromise between a multi-element lens and a molded plastic lens. The molded glass asphere has two basic advantages over a multi-element lens; first, the aspheric design reduces spherical aberration and coma in a single element; and second, overall light transmission is generally greater with fewer optical surfaces.
As compared with plastic lenses; molded glass aspheric lenses will operate over a much broader temperature and humidity range without performance degrading. Because of these advantages, molded glass lenses are often used in products such as laser printers, optical disc storage devices, and optical communications systems.
New Lens —
A
larger numerical aperture is often very desirable when coupling a collimating lens with a
laser diode. The newest molded glass asphere P/N 305-0464-780, has an NA of 0.5 and a
focal length of 4mm which seems ideally suited for many laser diode applications. With a
0.5 NA a coupling efficiency over 90% can be achieved with most diodes. For an
example of the typical beam size from this lens, refer to the web page
describing the laser diode mounting kit that uses this lens, LDM
3300 KIT. Detailed
specifications for all of the aspheric lenses are listed
below:
Unmounted Molded Glass Aspheric Lens Specifications:
| Part Number (unmounted lens) | 305-0464-780 | 305-0066-780 | 305-8040-780 | 305-8045-780 |
| Unit price (Qty 1-49) | $17.70 | $17.20 | $24.70 | $22.85 |
| Description | Molded Glass Aspheric Lens, Unmounted | |||
| Conjugate Distance | Infinite | |||
| Design Wavelength | 780 nm | |||
| Focal Length | 4.00 mm | 6.25 mm | 8.00 mm | |
| Working/Source Distance | 3.942 mm | 4.57 mm | 5.82 mm | 6.60 mm |
| Numerical Aperture | 0.50 | 0.40 | 0.30 | 0.25 |
| Clear Aperture | 4.00 mm | 5.00 mm | 4.80 mm | 4.06 mm |
| F# | 1.00 | 1.25 | 1.67 | 1.97 |
| Field Size (diameter) * |
0.050 mm | 0.100 mm | 0.100 mm | 0.200 mm |
| AR Coating, MgF2 | 780 nm | |||
| Transmission | > 97% | > 98% | > 98% | > 96% |
| Cover Glass Thickness | 0.25 ~ 0.30 mm | |||
| Cover Glass Index (n) | 1.500 | 1.511 | 1.511 | 1.50 |
| Temperature Range (�C) | -20 ~ +85 | |||
| Dimensions (diameter x length) | �6.40 x 2.5 mm | �6.40 x 2.5 mm | �6.37 x 4.0 mm | �6.40 x 2.5 mm |
* The Field Diameter of a collimating lens defines the largest size emitter the lens will accommodate and still maintain other optical specifications, such as the wavefront aberration specification.
Example: If the field diameter specification is 100 microns, then the size of the laser diode emitter must be less than 100 microns in either axis. Generally, when using lower powered diodes (1mW to 100mW) the emitter size is not a concern, as the emitter is typically only a few microns in the perpendicular or parallel axis. When using higher power diodes, diodes arrays, or LED’s the emitter can be significantly larger – emitters larger than 100 microns are common.
Molded Glass Aspheric Lens with an Extra-fine Pitch Threaded Mount:
The lenses listed in the table below are supplied mounted in an aluminum cell which has an extra fine-pitch thread on the outside diameter. The thread is defined as a 3/8"-64 UNS (or .375-64 UNS in decimal notation). While this is a special thread, there are thread cutting taps available from machine tool suppliers and we stock the taps as well for your convenience, p/n 900-3864-000. These thread taps can be used for prototype work by a skilled machinist however, in a production environment the thread should be machined by single-point turning on a CNC lathe.
Basic optical specifications are the same as the lenses listed in the "unmounted" table above.
Threaded Mount, with 3/8-64 (.375-64) fine pitch thread, part numbers and prices:
| Part Number (threaded mount) | Unit price (Qty 1-49) | Dimensions (thread diameter x overall length) |
| 306-0066-780 | $22.70 | 3/8-64 x 3.17 mm |
| 307-0464-780 | $23.70 | |
| 307-8040-780 | $32.00 | 3/8-64 x 4.7 mm |
| 307-8045-780 | $29.10 | 3/8-64 x 4.83 mm |
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