Testing For Sharpness - Nokia NHL-2NA Series Troubleshooting Instructions

NHL-2NA
If large dust particles get trapped on top of the lens surface in the cavity between cam-
era window and lens, they will cause image blurring and poor contrast (see also item
'sharpness'). The seal between the window and lens should prevent any particles from
getting into the cavity after manufacturing phase.
If dust particles are found on sensor, this is classified as a manufacturing error of the
module and thus the camera should be replaced. Any particles inside the cavity between
window and lens have most probably been trapped there in assembly phase in Nokia fac-
tory. It is of course also possible that the user has disassembled the device and caused
the problem. However, in most cases it should be possible to remove the particle(s) by
using clean compressed air. Never wipe the lens surface before trying compressed air; the
possibility of damaging the lens is substantial. Always check the image sharpness after
removing dust.

Testing for sharpness

If pictures taken with some device are claimed to be blurry, there are four possible
sources for the claim:
1 Back window is fingerprinted, soiled, dirty, visibly scratched or broken
2 User has tried to take a picture of a too close object – lens operates with dis-
tances from 30 cm to infinity
3 User has tried to take pictures in too dark conditions and images are blurred due
to handshake or movement. This is no cause to replace camera module
4 There is dirt between back window and camera lens
5 The back window is defective (somehow passed through window manufacturer's
inspection). Window should be changed
6 Camera lens is unfocused (somehow passed through camera manufacturer's
inspection)
Quantitative analysis of sharpness is very difficult to conduct in other than optics labo-
Page 10
Figure 14: Effects of dust in optical path
¤Nokia Corporation
CCS Technical Documentation
Issue 1 06/02