Fujifilm FCR XG-1 XRAY Scanner Teardown, Laser Scanner (Part 2 of 3)

[@KaizerPowerElectronicsDk]

The image is of cause generated from the PMT reading out the light level from laser exposure, please ignore my total and complete blunder in looking for the image sensor inside the laser modul :)

[@SeanBZA]

I would think the detector on the outside by itself is there to detect the beginning of a scan line, used in conjunction with a servo loop to reset a horizontal position counter in the raster scan, so that the time it takes to scan can be adjusted to a constant value by the mirror motor. That way any small motor speed variations do not result in a skew image, just up to a half pixel horizontal error. Likely the missing coating is there so the mirror and prism will not get blue light back from the plate, and only get a small part of the laser beam intensity in, so as to make the photodiode response faster.

[@TomStorey96]

Yep, my thoughts too!

[@KaizerPowerElectronicsDk]

You are right! I found the service manual for the scanner and its named "14.3 Checking the Start-Point Sensor (SYN)" . What a blunder I made there, I know perfectly alright that the image is formed from the PMT and not inside the laser module

[@zaprodk]

The beam scanning module is 100% identical to the one found in a laser printer. Totally the same setup. Thinking of it it's probably not custom at all - it's a standard part for a big digital photo copier!

[@KaizerPowerElectronicsDk]

I assume we talk a laser printer the same size, but it makes sense. Its just a change of laser diode from 633nm to 800'ish nm for laser printing and its go-time :)

[@gammaleader96]

Nice, the laser diode assembly kind of reminds me of a CD ROM drive, just bigger. Do you know the wavelength of the laser? Is it in the visible spectrum or is there a very special one needed? Greetings, Michael

[@KaizerPowerElectronicsDk]

I am not sure of this exact laser diode, but in general this technology uses a red 633 nm laser to invoke a photoluminescence effect in the image plate that returns a 400 nm blue light. There is a excerpt on that in the forum post from the link or link to my website :)

[@gammaleader96]

@@KaizerPowerElectronicsDk Nice, very interesting. I read the forum post just after commenting here, I guess I had some bad timing ;)