8° incidence
7 wavelengths 
0.01% resolution
0.1% accuracy



CT-7:   high precision, handheld, reflectometer-scatterometer  UV-VIS-NIR

New! Introducing CT-7a:  absolute reflectometer-scatterometer

Well known CT-7 instrument is dedicated to monitoring of the coating quality of the high grade optical surfaces like telescope mirror. CT-7 measures the specular reflection and the scatter using seven wavelengths spanning from UV to near IR.

CT7 with reflectivity gauge
CT-7a:Re-calibrating  absolute 100%
CT-7 with reflectivity gaugeCT-7a: absolute calibration in process 

The only difference between CT-7 and CT-7a lays in how they do refer to the real word. 
To set its scale, CT-7 uses a gauge calibrated in a laboratory.  All  measurements refere to this calibration:  CT-7 is a comparison reflectometer. As long as the gauge mirror is stable, the measurments are absolutely precise.

CT-7a  has a built-in  laboratory:  a rotating  arm  enables measurement of the complete optical path except the  examinated mirror, thus absolute, not subjected to aging or contamination, reference value of 100.00% reflectivity is obtained and maitaned.  CT-7a is an absolute reflectometer. 

Low noise, excellent  time and temperature stability makes both instruments perfect choice  for tracing the state of the coatings with evolution of contamination, cleaning and aliminization cycles during miror life time.  Detailed description can be found in the Application Note#11 Open PDF.

CT-7 is delivered with factory calibration and a reference gauge characterized in OPO laboratory. In addition, as in essence CT-7 is an optical caliper, it can be set to fit your laboratory standard and repeat the measurements at the remote location. CT-7a can work either with absolute 100.0% reference or with reflectivity gauge exactly as standard CT-7

The current model reaches repeatability of 0.01% fully benefiting from it's high precision optical head stability and data processing algorithm.

The incidence angle is set to 8° from normal which is close approximation of the work configuration of telescope mirrors and a practical minimum for such compact instrument.
Measurements are performed in such manner that the risk of damaging the precious mirror surface is minimized. The measure starts after a countdown of a few seconds, allowing gently placement of the instrument on the mirror. A three point isostatic contact is provided by spherical white Teflon touching feet. Moreover, the small incidence angle of the measuring beams makes the result little sensitive to the measurement distance so that the instrument can stand on an optical tissue.

Configurations of the instrument and data retrieval are facilitated by PC application CT-7 Console.

Measuring reflectivity of a telescope mirror.

CT-7 facts:

Optical principe of CT-7/ CT-7a

Protective tissue
Taking a measurement with a protective tissue.
/Note: there is a 20mm hole in the center of the tissue/

Release: 2010,
Major revisions: 2012, 2015, 2019
Last revision: March, 2020

Reflectivity    0-100.00% 
Scatter          0- 20.0%  ( TIS for lambertian surfaces)
  CT7   - calibration gauge with known parameters 
  CT7a - integrated absolute calibration of optical path
7 LED sources UV to NIR (e.g. : 365-405-464-522-624-750-970nm)
8° incidence
Reflectivity 8° from normal in incidence plane (specular)
Scatter    14° from normal, perpendicular to incidence plane


Power Source:
– Rechargeable Li-ION
– Duration > 200 measurements
– Charge Time ~ 3 hours
External: USB 5V 500mA

Data Transfer and control:

USB 2.0

Temperature Range:

Operations -30°C to + 45°C
Storage -40°C to + 50°C
Temperature drift 0.03%/°C:
Scatter ±0.1% overall
Reflectance ±0.1% overall
Temperature Coefficient:
Scatter detectors <±0.001% per °C
Reflectance detector <±0.001% per °C

Non-Volatile Memory:

Storage capacity >2M measurements
Real Time Clock time stamp for measurements
Named  measurements (for easy data selection)

OLED 1.7" (high contrast, works in negative temperatures)

PC Software – Included-
Downloads data to PC for statistical analysis.
Export of data for further processing
Data Archive
Control and diagnostics of CT-7
Win 7,8,10