


QC
PLOTS 

CURRENT 
HISTORY 
X0
and Y0 


translational matrix
coefficients 


rotational matrix
coefficients 


image quality 


ellipticity 


QC1
database (advanced users): browse
 plot 
Click on CURRENT
to see the current trending (Health Check).
Click on HISTORY
to see the historical evolution of the trending. 
The Mask to CCD Transformation Matrix translates mask
coordinates into CCD pixels. It is determined with special MOS masks having
pinholes on a regular grid. Measurements using these mask are typically
executed once a day for health check purposes. Since August 2010, these frames are also used to check the VIMOS focus.

Example MOS pinhole mask image 
top
Mask
to CCD transformation parameters 
The transformation matrix has the following form:
X = a_xx * x + a_xy * y + x_0
Y = a_yx * x + a_yy * y + y_0
with (x,y) being mask coordinates in mm and (X,Y) CCD
coordinates in pixels. X direction is along the slit orientation, y direction
is perpendicular to the slits (i.e. in dispersion direction).
The matrix coefficients a_xx, etc. and the zeropoints
x_0 and y_0 are determined from the pinhole image for each quadrant. The
diagonal coefficients a_xx and a_yy give the scale factor between mask
and CCD (around 8.4 pixels/mm). The coefficients a_xy and a_yx give the
rotation and are nearly zero.
QC1 parameters
parameter 
QC1 database: table, name

procedure 
x_0 
vimos_mask2ccd, x0 
x0 coefficient of mask to CCD transformation 
y_0 
vimos_mask2ccd, y0 
y0 coefficient of mask to CCD transformation 
a_xx 
vimos_mask2ccd, xx 
xx coefficient of mask to CCD transformation 
a_xy 
vimos_mask2ccd, xy 
xy coefficient of mask to CCD transformation 
a_yy 
vimos_mask2ccd, yy 
yy coefficient of mask to CCD transformation 
a_yx 
vimos_mask2ccd, yx 
yx coefficient of mask to CCD transformation 
From the pinhole images, also QC parameters for checking the focus are calculated. These are image quality (as FWHM in pixels of the major axis fo the pinhole ellipses), ellipticity, and orientation (of the pinhole ellipses). Each quadrant is divided into 3x3 sub cells (squares). All parameters and their standard deviations are calculated in each cell and globally per quadrant.
QC1 parameters
parameter 
QC1 database: table, name 
procedure 
pinhole_count 
vimos_mask2ccd, pinhole_count 
total number of identified pinholes per quadrant 
image_quality_mean 
vimos_mask2ccd, image_quality_mean 
averaged image quality per quadrant 
image_quality_rms 
vimos_mask2ccd, image_quality_rms 
standard deviation of image quality per quadrant 
ellipticity_mean 
vimos_mask2ccd, ellipticity_mean 
averaged ellipticity per quadrant 
ellipticity_rms 
vimos_mask2ccd, ellipticity_rms 
standard deviation of image quality per quadrant 
orientation_mean 
vimos_mask2ccd, orientation_mean 
averaged orientation of pinhole ellipses per quadrant 
orientation_rms 
vimos_mask2ccd, orientation_rms 
standard deviation of orientation per quadrant 
iq_mean_cell[19] 
vimos_mask2ccd, iq_mean_cell[19] 
averaged image quality in each cell (per quadrant) 
iq_rms_cell[19] 
vimos_mask2ccd, iq_rms_cell[19] 
standard deviation of image quality in each cell 
ellip_mean_cell[19] 
vimos_mask2ccd, ellip_mean_cell[19] 
averaged ellipticity in each cell 
ellip_rms_cell[19] 
vimos_mask2ccd, ellip_rms_cell[19] 
standard deviation of ellipticity in each cell 
orient_mean_cell[19] 
vimos_mask2ccd, orient_mean_cell[19] 
averaged orientation in each cell 
orient_rms_cell[19] 
vimos_mask2ccd, orient_rms_cell[19] 
standard deviation of orientation in each cell 
History
date 
event 
201105 
tilt between focal plane and detector plane fixed, image quality and ellipticity improved; there is, however, a dependency between ellipticity and temperature 
20110827 
Q3 out of focus, fixed 20110906 
