The significance of the cosine response of the input optic (typically a diffuser or integrating sphere) for irradiance measuring spectroradiometers has often been rather overlooked.

Radiometric errors of up to 50% are often recorded by some commercially available spectroradiometers when measuring sunbeds, solar simulator cabinets, etc., simply because of the inherent lack of cosine response. Further errors due to calibration factors, poor stray light rejection, etc., can make the situation even worse.

Bentham is able to supply the very highest quality cosine response diffusers with f₂ errors of less than 1%. Each diffuser is supplied with its own calibration certificate.

Options
Model	Spectral Range of use (nm)	f error (typ) %	f error (max) %	Notes
D6	200-600	0.75	1.0	In-line
D6-H	200-600	0.75	1.0	Horizontal
D6-ENV	200-600	1.5	2.0	Quartz dome
D6-SMA	200-600	1.5	2.0	SMA
D6-SMA-ENV	200-600	1.5	2.0	Dome & SMA
D7	200-1100	0.75	1.0	In-line
D7-H	200-1100	0.75	1.0	Horizontal
D7-ENV	200-1100	1.5	2.0	Quartz dome
D7-SMA	200-1100	1.5	2.0	SMA
D7-SMA-ENV	200-1100	1.5	2.0	Dome & SMA