CT7

Note for CT-7a.

This article concerns CT-7 using reflectivity gauge  reference- a mirror characterized in a laboratory, thus with known 'ideal' reflectivity figures. CT-7 is tuned to produce the same values on this gauge. In the contrary,  CT-7a is able to measure its own optical path, obtaining absolute by definition 100.00% reference reflectivity.  However if it is used  with a gauge as reference,  it becomes standard CT-7 and presented hereby prodceure is fully applicable.  

CT7 has no intrinsic reflectivity reference. The construction of the instrument and its measurement technique ensures very high precision and stability of measured ratio of source intensity to the  returned signal.

This ratio is converted to reflectivity value by dividing it by calibration coefficient which is found by measuring a known mirror in CALIBRATION operation.

For user convenience, a first surface AL mirror, with known nominal reflectivity values for each wavelength is provided as calibration reflectivity target.

It may happen that at user location there is a reference lab and all measurement are referenced to local calibration system giving slightly different values. In this case it would be prefereble to measure locally the CT7 gauge and to use these  locally measured parameters for CT7 calibration. 

CT7 Import/Export  functions provides an easy way to do it.

IMPORTANT: the CT7 measures the refletivity at 8 degree incidence angle. 

The procedure:

1. Prepare a text file giving the gauge reflection values obtained in your laboratory. This file should look like this :

    Open soft calibration file example.

2. Connect CT7 to PC,  ( at CT7 : menu Service/PC Link,   at PC : CT7-Console,  panel CT7 Management)

3. Read the parameters from CT7: "Read CT7"

The  parameters table will be filled with CT7 parameters

4.  Load your local parameters file using funtion  "IMPORT PARAMS" 

local parameters from file will be loaded to their columns.

5. Write the parameters to CT7 using "Write CT7" function

6. Calibration to the new values ends the operation:  CT7-Console/CT7 Management /CALIBRATION

See also User Manual , chapter "Soft Calibration Target values".