November 30, 2010

Elphel as a line-scan camera (for river panoramas)

by M@sh

In my search for an affordable and reasonable solution of creating high-res panoramic river views I came along the Elphel camera and it’s photo-finish mode. As part of my ongoing projects Danube Panorama Project, Nile Studies and the new umbrella project River Studies, I am capturing virtually endless panoramic river views from a moving vessels with a slit- or line-scan method. I was using webcams or DV-cameras before, and all possible ways to upgrade to higher resolutions either seemed clumsy (I don’t want to be loaded with much more than a tiny laptop or tablet and the camera itself), very processing intense and/or expensive and far out of reach of my (very limited) budget.

The “all-purpose camera” Elphel stepped in as a good, reasonable and flexible solution for that task. The first season using an Elphel353 is over, so time to share some of my experiences with Elphel and it’s not so well know photo-finish mode for line-scanning.


November 18, 2010

“Zoom in. Now… enhance.” – a practical implementation of the aberration measurement and correction in a digital camera

by Andrey Filippov

Deconvolved vs. de-mosaiced original

This post describes the implementation of the optical aberration measurement and correction developed for Elphel Eyesis cameras, the same methods and the code (available under GNU GPLv3) can be applied to many other camera systems. With 1/2.5″ 5 megapixel sensor we achieved average sharpness improvement over the image area around 40% compared to the raw images, effectively doubling the resolved pixel count. The applied correction varied significantly with the location on the image plane, orientation and color channel, making simple uniform isotropic sharpening (i.e. with “unsharp mask” or similar filtering) useless in our case. The aberrations correction is based on well-known measurement and inversion of the system point-spread function (PSF), additionally we describe used frequency domain de-mosaic filtering (“spectral scissors”) compatible with the inverted PSF convolution.


November 6, 2010

Elphel cameras and 4096 (4K) sector drives – solved

by Andrey Filippov

We were assembling four of the nc353_369_hdd camera kits with internal 1.8″ HDD. Unfortunately, when we assembled them – none worked, on the serial console output we could see unhandled interrupts leading to kernel panic when we just tried to format the disk. And the same on all of the 4 cameras, all of the 4 disks, so that could not be a problem with the particular board or device.

Yes, the disks we purchased – 120GB Toshiba MK1231GAL were new for us – we never used them before, but those that we tested earlier were not available. So we looked at the specs and concluded that they should work – same PATA, same ZIF connectors.