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Camera Aided Robot Calibration

Robot calibration is the process of enhancing the accuracy of a robot by modifying its control software. This book provides a comprehensive treatment of the theory and implementation of robot calibration using computer vision technology. It is the only book to cover the entire process of vision-based robot calibration, including kinematic modeling, camera calibration, pose measurement, error parameter identification, and compensation.

The book starts with an overview of available techniques for robot calibration, with an emphasis on vision-based techniques. It then describes various robot-camera systems. Since cameras are used as major measuring devices, camera calibration techniques are reviewed.

Camera-Aided Robot Calibration studies the properties of kinematic modeling techniques that are suitable for robot calibration. It summarizes the well-known Denavit-Hartenberg (D-H) modeling convention and indicates the drawbacks of the D-H model for robot calibration. The book develops the Complete and Parametrically Continuous (CPC) model and the modified CPC model, that overcome the D-H model singularities. The error models based on these robot kinematic modeling conventions are presented.

No other book available addresses the important, practical issue of hand/eye calibration. This book summarizes current research developments and demonstrates the pros and cons of various approaches in this area. The book discusses in detail the final stage of robot calibration - accuracy compensation - using the identified kinematic error parameters. It offers accuracy compensation algorithms, including the intuitive task-point redefinition and inverse-Jacobian algorithms and more advanced algorithms based on optimal control theory, which are particularly attractive for highly redundant manipulators.

Camera-Aided Robot Calibration defines performance indices that are designed for off-line, optimal selection of measurement configurations. It then describes three approaches: closed-form, gradient-based, and statistical optimization. The included case study presents experimental results that were obtained by calibrating common industrial robots. Different stages of operation are detailed, illustrating the applicability of the suggested techniques for robot calibration. Appendices provide readers with preliminary materials for easier comprehension of the subject matter. Camera-Aided Robot Calibration is a must-have reference for researchers and practicing engineers-the only one with all the information!

To calibrate the focus on a Zeiss Super Ikonta and Moskva coupled rangefinder cameras.
You need a tiny screwdriver, a "crystal" CD case, and a powerful loupe. Oh, the cable trigger is useful too.

First, manufacture yourself a nice ground "glass" using the CD case. You know how these things break easily. Well this time to it on purpose. Using a sharp knife, just strongly "mark" a 65mm by 120mm strip of the case.
Then take a very very thin sandpaper and gently polish the surface you marked until it is perfectly opaque. When you are happy with a nice smooth finish, *break* the surrounding plastic until you have your nice strip of rigid and clean ground glass. Be sure to clean the plastic properly afterward.

Next, remove the camera back, and use rubber bands to hold the piece og "ground glass" on the film transport. The face you polished must be toward the lens, it is on that surface that the image forms. Make sure the plastic is perfectly placed on the film plane.

Next, make sure your rangefinder is set and blocked on infinity. Use a very distant landmark, like a church or similar. Pick a very contrasty feature, set on a nice sky, this will help a lot.

Now, using the small screwdriver, unscrew the 3 tiny screws that are set along the border of the lens front element. Do *not* unscrew all the way, just a couple turns will suffice for the purpose.

Once this is done you should be able to remove that ring.

At that point, you will have access to the front element proper, including it's treads.

If you feel brave, you can unscrew it completely (make sure you mark the thread position when it comes off, so you can out it back exactly as it was) and clean the glass.
You can also use lighter fuel to disolve the grease of the thread and replace it with new one. A good compromise is to let a couple of drops of lighter fuel on the crew threads to soften the old grease...

Anyway, once you are happy that the glass is clean the the focusing is smooth, screw back the front element in completely in.

Next position the camera on a tripod and direct it at your favourite contrasty landmark; set the lens to wide open aperture, then use the cable trigger with the camera set on "B" bulb mode to open the shutter.
You will see your landmark, in reverse, on your ground glass.

Now it's a question of using the loupe to find the perfect focus position for infinity. take your time, and when you are happy make sure you don't touch the focus ring any further.

When that is done, position back the ring you had unscrewed and removed earlier (again, being careful not to move the front element) and re-screw your 3 little screws to hold it in place. Don't force anything, just use "reasonable" to "light" torque.

There you are ! perfectly calibrated rangefinder !

So, in the spirit of getting cameras actually doing exactly what you tell them to do, I offer the total ghetto method shutter tester for dapper old film cameras. It is very accurate.

All you need is some frosty invisible tape, your camera, an old television or CRT computer monitor.

Since the television sweeps at 60 frames a second, (set the refresh rate of computer monitors to 60 to work right) it will show you the exact fraction of a 60th you camera would be exposing your film.

The easy ghetto way is to open up the back of your camera, and make a ground glass out of frosted tape. Just stretch it in front of the shutter (don't touch the shutter with the tape or anything else!) and attach it to the pressure plate rails. These are shiny areas on either side that have been precisely machined to hold the film in the correct place. My next few pics are of that process.

With all this nonsense in place, you can leave the back of your camera open, and take pictures of the old television. You will see the image on the tape. It will look like these examples and be pretty obvious. at 125th you should see half of the screen illuminated. 250th: a quarter... You get the idea.

Just thought I should get this out of my head. I think it's kind of nice to know.

This is the NEWEST GENERATION of Microscope cameras!!! Our latest generation of MU cameras features upgraded electronics, streamlined software, and a compact design with smaller dimensions and reduced weight. Our company is located in the USA and all cameras come with a 1-YEAR WARRANTY! Featuring built-in C-mount compatibility and 23mm reduction lens adapter, our camera can be attached to any instrument with a C-mount or a 23mm photo port, including microscopes, telescopes, endoscopes, and etc. The camera's optics offers 3264x2448 pixel resolution, and the included software allows you to capture real-time, high-definition videos and stills without requiring any additional equipment. The included user-friendly software and calibration kit allow you to make notes, shapes, watermarks, and precise measurements with ease. You can analyze, present, and share images of samples and specimen by simply plugging one end into your PC's USB 2.0 port, and the other on your microscope's eye-tube or trinocular port. In addition, the newest generation of MU camera comes with a preassembled 0.5X reduction lens, giving your PC screens the same field of view as your microscope's eyepiece. With the reduction lens in place, your camera tube is 23mm in diameter, making it compatible with pretty much any microscope's eye tube or trinocular port! We also include 2 eyepiece adapters for FREE - 30.0mm and 30.5mm. With its unique stand alone design, the MU series camera is equipped with CMOS color sensor, and comes with a high-speed USB 2.0 cord, advanced software (Windows XP/Vista/7 compatible), 4 mounting sizes (23mm, 30mm, 30.5mm, and C-mount), and instructions. We are based in the USA and all our cameras come with a 1-year full-coverage warranty and a life-time of free software upgrades. It arrives brand new in a factory sealed box and retails for more than $1,100.