Patent ID: 7411679

Claim:
An emission filter for use in a spectroscopy system comprising a beamsplitter having a first wedge angle α Di , said emission filter comprising: a substrate; a first thin-film interference filter disposed directly on said substrate, said first interference filter comprising a first plurality of hard coating thin film layers of alternating high and low index of refraction and being configured for transmitting a first range of wavelengths; a second thin-film interference filter disposed directly on a second surface of said substrate opposed to said first surface, said second interference filter comprising a second plurality of hard coating thin film layers of alternating high and low index of refraction and being configured for transmitting a second range of wavelengths, said second range of wavelengths being different from said first range of wavelengths, said first and second thin-film interference filters, thereby establishing a bandpass transmission characteristic for said filter; and wherein said emission filter has a second wedge angle α Em in accordance with the equation 0.072α Em +0.12α Di <±1 pixel.