Photochromic lens spectrophotometer

BPC300 from Bentham

The BPC300 spectrophotometer offers accurate characterisation of photochromic (photosensitive) lens transmission in the faded and AM2 conditioned states.The fully automated BPC300 enables product testing of prescription and non-prescription sunglasses in accordance with international standards, and the development of photochromic formulations.The versatile BPC300 permits darkening and fading-back kinetic studies, whilst the modification of sample temperature, conditioning beam illuminance and spectrum accounts for a broad range of lens exposure conditions. An optional polarising lens capability is on offer for the extension of the measurement scope.

Features

Monochromator based, collimated tuneable light source (280-780nm)
Temperature-controlled water bath with mount for plano lens sample
AM2 conditioning beam (including facility to attenuate and filter spectrum)
Optically chopped monochromatic beam with lock-in signal recovery enables measurement under AM2 activation
Automated reference level measurement
Fully-automated by Windows application including establishment and running of pre-defined measurement profiles
Generation of measurement report including parameters required by standards

Further information

Core benefits

Accurate transmission testing of photochromic lenses
Explore lens performance in range of conditions
Monitor rates of darkening and fading
Easy and highly repeatable process

Reported parameters

τ_V0 : Luminous transmittance in the faded state at (25±2)°C
τ_V1 : Luminous transmittance in the darkened state at (25±2)°C
τ_V0 /τ_V1 : Photochromic Response
Lens category
Colourimetric parameters: CIE 1931 & CIE Lab
τ_SUVA : Mean UVA spectral transmittance weighted by AM2
τ_SUVB : Mean UVB spectral transmittance weighted by AM2
Q_sign : Visual attenuation coefficient for red, green, blue and yellow incandescent
τ_sb : Solar blue light transmittance
The rate of darkening and fading at a single wavelength

Optional reports include:

τ_VW : Luminous transmittance at (5±2)°C
τ_VS : Luminous transmittance at high temperature (35±2)°C
τ_VA : Luminous transmittance at reduced solar simulator level and (25±2)°C

Specifications

Measurement

Spectral range of operation	280-780nm
Bandwidth	5nm
Wavelength accuracy	± 0.1nm (2400g/mm), ± 0.2nm (1200g/mm)
Beam diameter at sample plane	4mm diameter
Measured transmission range	0.5-100%
Maximum sample diameter	75mm
Conditioning beam	AM2 with requirements of ISO8980-3:2013 0-50klx Shutter Optional filtering
Temperature range	5-50°C
Temperature accuracy	± 0.2°C
Bench space required	1m deep x 2.5m wide
Services requirements	6 x main sockets 1200W power consumption Nitrogen gas supply where measurements below ambient are required

Monochromatic probe source

UV source	30W Deuterium lamp
UV-Vis source	100W Quartz Halogen lamp
Monochromator configuration	Symmetric, single Czerny-Turner
Monochromator focal length	300mm
Diffraction gratings	2400 & 1200 g/mm
Diffraction grating mount	Triple grating turret
Dispersion	5.4nm/mm (2400g/mm) 2.7nm/mm
Bandwidth	5nm
Wavelength accuracy	± 0.1nm (2400g/mm) ± 0.2nm (1200g/mm)
Chopping frequency	175 Hz (typical)
Beam diameter at sample plan	4mm diameter

Water bath

Temperature range	5-50°C
Temperature accuracy	±1°C

Conditioning beam

Spectral match	AM2 with requirements of ISO8980-3:2013
Beam illuminance	0-50klx
Beam filtering	Optional filtering

Computer requirements

OS	Windows 7, Windows 8 (32-/64-bit) operating systems (or newer)
Software control	BenWin+ Spectral acquisition software
Minimum hard disk space	Approx. 100MB
Minimum RAM	2 GB
Interface	4 x USB 2.0 ports

Applications

ISO/ EN 8980-3:2013 - "Ophthalmic optics. Uncut finished spectacle lenses. Transmittance specifications and test methods."
ISO/ EN 12312-1:2013 - "Eye and face protection. Sunglasses and related eyewear. Sunglasses for general use."
ANSI Z80.3: 2015 - "Non-prescription Sunglass and Fashion Eyewear Requirements."
A S/NZS 1067-2016 - "Sunglasses and fashion spectacles."