Figure 5.6 Catching the optical axis and centring the field. a) When you first insert the camera you may see
no image at all. The small blurry circles are dust specs on the eyepiece. b) and c) Adjusting the angle of the
camera on the scope will begin to bring the optical axis into alignment. d) The optical axis is almost centred
but the fact that the brightest spot is off-centre means there is still some adjustment to make. e) The optical
axis is aligned (the brightest area is central) BUT the circular field of view disc is not centred in the camera’s
rectangular field of view. f) A few more small adjustments centres everything – the field of view disc is
centred in the rectangular camera field and the central bright area is centred in the circular field of view. We
can now progress to reducing the vignetting by height adjustments (see figure 5.7).
Do not be concerned about vignetting at this stage (the light being darker at the periphery
than the centre) but do ensure that the brightest part of the image is well centred in the
circular field of view. Also, ignore the position of the specimen under the microscope – you
are only concerned about the patterns of illuminating light (in figure 5.6 I moved the
specimen on the stage in between image captures so it will not look in the same position
in each image – but that is irrelevant, as is any slight defocussing).
Angular adjustment tends to move the circular eyepiece field more than XY translational
adjustment but too much adjustment of either angular or XY shift on their own will tend to
loose the image as the optical axis of the scope and camera lens come out of alignment.
These two adjustments must therefore be made incrementally with each other.
If the camera is extremely out of alignment you will loose image altogether so if you do not
see an image at all you should adjust angle and XY shift till you ‘catch’ the image from the
eyepiece. This can be quite tricky sometimes because there is a very narrow window of
adjustment settings where the image can be seen.
OptArc AF51 Camera Page 58 of 99 User Guide v1.02