Case Study: 910 nm Long Pass Filter

Data Table

Specification

Value

50% T%

910 nm +/- 10 nm

Transmission Range

900 – 1700 nm

Blocking Range

UV– 895 nm

Peak Transmission %

T% >90%

Substrate

RG 850

Dimensions

19.5 mm Dia

Thickness

2 mm

Scratch/Dig

60/40

Quantity Per Year

100

Case Study: Filter for UV and Visible Blocking with Near Infrared Transmission

 

Customer Challenge: This customer wanted a steep visible blocking filter that transmitted in the near infrared from 900 to 1700 nm but blocked from the UV through to 900 nm, this was for an InGaAs based system and the customer saw a risk with visible signal giving ‘false positive’ results within their measuring system. The filter had to have a less than 2% slope and there was also a ‘cost budget challenge’ to meet.

Vortex’s Solution: There are 2 possible Long Pass Filters that could solve the problem, the first one involves coating a standard glass such as borosilicate glass or Schott B270 with a multiple stack filter, this is approach is shown in Fig 2. Although Fig 2 is an effective solution, it is however quite costly. Fig 1 shows a lower cost solution we proposed using Schott RG 850 glass. Using the Schott glass, the coating ‘contribution’ to blocking is limited to a single stack Long Pass Filter, thus reducing the total cost by about 50%.

The Result: This solution demonstrates how good advice can help when considering solutions. In general, talking to filter designers early in instrument design can help reduce cost through open and confidential discussion. Vortex are only too happy to provide experience-based ‘system advice’ as well as the problem solving filter.  In this case a solution was found which met the financial budget challenge and the optical performance.