October 31, 2011
by Andrey Filippov
Motivation
While working on the second generation of the Eyesis panoramic cameras, we decided to try go from capturing the series of the individual panoramic images to the 3d reconstruction. There are multiple successful implementations of such process, we just plan to achieve higher precision of capturing the 3d worlds using Elphel ability to design and build the hardware specific for such purpose. While most projects are designed to work with the standard off-the-shelf cameras, we are working on building the cameras together with the devices and methods for these cameras calibration. In order to be able to precisely determine the 3-d locations of the features registered with the cameras we plan first go as far as possible to precisely map each pixel of each sub-camera (of the composite camera) image to the ray in space. That would require at least two distinctive steps:
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June 15, 2011
by Andrey Filippov
WebGL Panorama Editor (view mode)
This April we attached Eyesis camera to a backpack and took it to the Southern Utah. Unfortunately I did not finish the IMU hardware then so we could rely only on a GPS for tagging the imagery. GPS alone can work when the camera is on the car, but with a camera moving at pedestrian speed (images were taken 1-1.5 meters apart) it was insufficient even in the open areas with a clear view of the sky. Additionally, camera orientation was changing much more than when it is attached to a car that moves (normally) in the direction the wheels can roll. Before moving forward with the IMU data processing we decided to try to orient/place some of the imagery we took manually – just by looking through the panoramas, adjusting the camera heading/tilt/roll to make them look level and oriented so the next camera location matches the map. Just tweaking the KML file with the text editor seemed impractical to adjust hundreds of panoramic images so we decided to add more functionality to our simple WebGL panorama viewer, make it suitable for both walking through the panorama sets and for the editing orientations and locations of the camera spots. (more…)
May 19, 2011
by Andrey Filippov
CAD rendering of the Analog Devices ADIS-16375 Inertial Sensor, 103695 interface board and 103696 serial GPS adapter board attached to the top cover of NC353L camera
For almost 3 years we had a possibility to geo-tag the images and video using external GPS and optional accelerometer/compass module that can be mounted inside the camera. Information from the both sensors is included in the Exif headers of the images and video frames. The raw magnetometer and accelerometer data stored at the image frame rate has limited value, it needs to be sampled and processed at high rate to be useful for the orientation tracking , and for tracking position it has to be combined with the GPS measurements.
We had developed the software to receive positional data from either Garmin GPS18x (that can be attached directly to the USB port of the camera) or a standard NMEA 0183 compatible device using USB-to-serial adapter. In the last case it may need a separate power supply or a special (or modified) USB adapter that can provide power to the GPS unit from the USB bus. (more…)
March 14, 2011
by Andrey Filippov
Last week our phone system was broken into and we’ve got a phone bill for some five hundred dollars for the calls to Gambia. That expense was not terrible, but still that amount is usually enough for many months of the phone service for our small company – the international phone rates in the VoIP era are (for the destinations we use) are really low. The scary thing was that the attack lasted for very short time – just minutes, not hours, so our damage could be significantly higher. (more…)
February 28, 2011
by Andrey Filippov
Current state of the Eyesis project,
what worked and what did not. Or worked not as good as we would like it to
Most of the last year we spent developing Eyesis panoramic cameras, designing and then assembling the hardware, working on the software for image acquisition and processing. It was and continues to be a very interesting project, we had to confront multiple technical challenges, come up with the solutions we never tried before at Elphel – many of these efforts are documented in this blog.
We had built and shipped to the customers several Eyesis cameras, leaving one for ourselves, so we can use it for development of the new code and testing performance of the camera as a whole and the individual components. Most things worked as we wanted them to, but after building and operating the first revision of Eyesis we understood that some parts should be made differently.
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January 3, 2011
by Andrey Filippov
View the results
We had nice New Year vacations (but so short, unfortunately) at Maple Grove Hot Springs, and between soaking in the nice hot pools I tried the emerging technology I never dealt with before – WebGL, a part of HTML-5 standard that gives you the power of the graphic cards 3-d capability in the browser, programed (mostly) in familiar javaScript. I first searched for the existent panoramas to see how they look like and how responsive they are to the mouse controls, but could not immediately find something working (at least on Firefox 4.0b8 that I just installed – you’ll need to enable “webgl.enabled_for_all_sites” in “about:config” if you would like to try it too). Then I found a nice tutorial with the examples working without a glitch and carefully read the first few lessons.
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December 21, 2010
by Andrey Filippov
UPDATE: The latest version of the page for comparing the results.
This is a quick update to the Zoom in. Now… enhance. – a practical implementation of the aberration measurement and correction in a digital camera post published last month. It had many illustrations of the image post-processing steps, but lacked the most important the real-life examples of the processed images. At that time we just did not have such images, we also had to find out a way to acquire calibration images at the distance that can be considered “infinity” for the lenses – the first images used a shorter distance of just 2.25m between the camera and the target, the target size was limited by the size of our office wall. Since that we improved software combining of the partial calibration images, software was converted to multi-threaded to increase performance (using all the 8 threads in the 4-core Intel i7 CPU resulted in approximately 5.5 times faster processing) and we were able to calibrate the two actual Elphel Eyesis cameras (only 8 lenses around, top fisheye is not done yet). It was possible to apply recent calibration data (here is a set of calibration files for one of the 8 channels) to the images we acquired before the software was finished. (more…)
November 18, 2010
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.
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November 6, 2010
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.
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June 24, 2010
by Andrey Filippov
Designing for low parallax
When we started working on Eyesis project our first goal was to make the panoramic head as compact as possible to reduce parallax between sensors. That not only reduces the stitching artifacts but also decreases the minimal distance to object without dead zones between the individual camera.
The first practical step was to reduce the PCB area around the sensors, especially in one direction, so multiple camera boards can be placed closer to each other, For that purpose we preserved the basic design of the proven 10338 sensor board, just changed the layout to make it more compact. The board 10338D is just 15mm wide – more than twice less than the older design.
Next step was to run mechanical CAD program and try to place the boards and lenses. Most of the Elphel cameras were designed for the C/CS-mount lenses, but when I tried to place them I immediately found out that when using 10 or 8 cameras around even the C-mount thread (CS is the same size but even closer) will be the limiting factor, not the sensor PCB that we already made smaller.
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