Focusing the video lens
DFNEXT
This section describes how to focus FUJINON video camera lens in DFNEXT camera systems (Point grey / FLIR digital cameras) using freeture video capture software.
Stop the freeture SW running as service
systemctl stop freeture.service
Run freeture in to display currently captured video live on screen
Login as user which is not root locally (keyboard + monitor + mouse needed).
Start windows manager
startx
Start terminal. The following commands are to be executed in x-terminal.
Switch user to root may be needed
su - root
Run freeture, zoom in, set window with video full screen or enlarge it to se the focus is sharp:
freeture -m 2 --display -g GAIN -e EXPOSURE_TIME
Use GAIN (0 .. 29.99) and EXPOSURE time (0-33000 in microseconds; max exposure time is driven by frame rate 30Hz) appropriate for the current lighting conditions.
In full screen/enlarged mode, the image update may be slow or freeze. This is related to the CPU load and I/O over USB load - transferring image from video camera over USB and scaling it to screen buffer. Restart the above command if that happens and zoom in only partially or zoom 1:1, but shrink the window.
A tiny hex/allen key (size 0.9 mm) is needed to loosen the DFNEXT's Fujinon fish-eye video lens focus fixing bolts and to tighten them again when focused. There are 3 of these tiny set screws - to access them, the lens needs to be temporarily removed from the camera enclosure (undo the flange bolts from top of the camera system box with M7 spanner). On a new lens, it may be quite hard to get the hex key into the screw head as they are fixed with thread locking glue and some of the glue might be in the hex socket insert.
Note: Set the F-stop (mechanical lever on the lens) to full open, check if the focus is sharp as with f/1.8 or f/2.0. If yes, keep the wide open setting. If not, stop down to f/1.8 or f/2.0.
Stop freeture
By pressing [Esc] in the terminal window where it was started - not in the window with live video stream.
Start the freeture SW running as service again
systemctl start freeture.service
AMOS Spec (or any machine vision camera equipped with a rectilinear lens)
Things required
- physical access to the camera
- a laptop (Windows has more software GUIs for this job)
- a USB3 Micro B cable (camera side) + whatever your computer will take on the other side (USB3 A or USB-C)
- GUI to drive the camera in live view (see below)
Software needed
Camera manufacturers typically ship basic GUIs for interacting with their cameras, should be sufficient in most cases:
- The Imaging Source: https://www.theimagingsource.com/en-us/support/download/iccapture-2.5.1557.4007/
- Allied Vision:
- Point Grey/FLIR:
Astronomy capture GUIs can sometimes offer more control:
Procedure
Best results are obtained using stars.
Using a foreground object >50m away (building, tree...) is an alternative.
- wait for a clear night, point camera at the sky.
- connect camera to your laptop directly using USB cable.
- launch GUI, connect to the camera.
- whack the gain up.
- set exposure to something high enough that enough light is collected, but live view feedback is still quick (0.1 s).
- make sure aperture ring is set to fully open (typically f/1.0 f/1.4, the lowest number possible), even if the setting in operational mode is not fully open.
- stretch the histogram on the GUI to enhance the brightness of faint detail (the live view image should be visibly noisy). Not all GUIs have this option. See "Adjusting the Display Histogram Stretch" on https://docs.sharpcap.co.uk/3.2/13_CameraControls.htm
- if focusing for the first time, play with the focus ring until you see some stars.
- fine tuning: easiest way to know you have achieved optimal focus is to look at faint stars in the field, the faintest ones will only be visible for a very short range on the focus ring.
- lock the ring with the thumb screw, and then check that you didn't accidentally move it.
- finally, check the orientation of the diffraction grating (as it sometimes rotates when focusing), so that it provides a horizontal spectra from the source. You can check this by shining a light on the camera and looking at the output.
