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Welcome to the VideoFROG Help page where we have written some VideoFROG tips, suggestions, and a few things that we forgot to include in the manual (Gasp!).
Installing and Running VideoFROG under Vista
VideoFROG runs fine under Vista provided you do two things. First, when you install VideoFROG, keep the install program from autostarting. Right click on setup.exe and select “Run as Administrator.” VideoFROG will then be able to make all the changes it needs to make to run on your computer. The second, is when you run VideoFROG, select “Run as Administrator.” You may edit the shortcut to do this for you.
Installing the framegrabber under Windows XP
We have just recently become aware of a hiccup in the framegrabber installation. While the Mutech manual does not discuss the installation of the MV-510 under Windows XP, the MV-510 does work fine under Windows XP.
Generally, there is little difference between Windows 2000 and Windows XP from a hardware perspective. Thus, you should just follow the Windows 2000 instructions. Unfortunately, there is one hiccup that has recently been pointed out to us. The Mutech manual states that the framegrabber should be installed before installing the software. The new hardware wizard appears in Windows XP, similar to the way it appears under Windows 2000. However, once you start to install the Mutech software, you are asked if you want to uninstall the MV-510 driver before the installation program reinstalls it. Go ahead and say “yes” to uninstalling the MV-510 driver, then proceed with the installation.
Running the Mutech programs to test the frame grabber.
OK, so you’ve installed the Mutech framegrabber and the Mutech demonstration programs. You hook up the video signal, run the demo program, see nothing, and have an unflattering thought about Mesa Photonics. The reason why you see nothing is because the Mutech demo program defaults to video channel 0 and VideoFROG defaults to video channel 2. For purposes of the test, you can connect the video to the red channel (channel 0), or change the channel by selecting the “Video Adjustment” item from the “Adjust” pull down menu. This brings up a dialog box that allows you to change the video channel. After you do that, you’ll have to start the data acquisition by selecting the “Start Grab” item under the “Grab” pull down menu.
Saving data in VideoFROG.
VideoFROG has several methods for saving data, which can be divided up into three different basic types: 1) Raw bitmap image, 2) processed data, and 3) semi-processed data for other applications.
Bitmap images of the raw video can be saved by left clicking in the raw video image. No dialog box will appear. The data will be saved with a date and time stamp. We feel that this allows several files to be saved in fairly rapid succession.
Processed data can be saved in both VideoFROG mode and Spatial Profile mode. In fact, when in VideoFROG mode, you can ONLY save processed data. In Spatial Profile mode you can save both processed data, and semi-processed data.
The semi-processed data I’m referring to is the image save when in Spatial Profiling mode. Suppose you want to save a FROG trace for Femtosoft’s FROG program. Clicking on the “Save Image” button save the image, with the background subtracted, in an ASCII file. Use this data saving feature to save data for other programs. The processed data is mainly for plotting programs and spread sheet programs.
What’s all this gamma stuff, anyway?
Back in the good old days, when men where men and women were women, CRTs were used to display images. These devices worked by pounding a beam of electrons into a phosphor (What’s a few x-rays among friends?). This worked fine except for the fact that the light output was not linearly proportional to the electronic beam energy. Thus, a way of correcting for this nonlinearity was devised that precompensated the image intensities. This precompensation is called gamma. When gamma is equal to 1, there is no precompensation being used. If the precompensation, and hence the gamma is on, the recorded intensity is the actual intensity raised to the 0.45 power (The specification for gamma is 0.45). This is pretty close to a square root, which is what the phase retrieval algorithm wants in the first place. This has the additional advantage of improving the signal-to-noise ratio and the signal-to-background ratio.
Unfortunately, gamma correction is going the way of the dodo bird and will soon become extinct. Already, video camera manufacturers don’t really care about gamma anymore (sniff). Indeed, the Sony cameras that are shipped with the GRENOUILLE have a gamma of about 0.6 - 0.7 -- a far cry from a square-root. This causes the retrieved FROG trace error to increase. As a result, for version 4.0, we added a gamma correction to improve the performance of VideoFROG. But now, with version 7 and the USB cameras, there is really no reason to use a gamma of anything other than 1.0.
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