Tutorial example 1

Getting acquainted with the drawer tools

You can down load a folder of files from my web site [http://homepage.mac.com/adcottrell/OpticsSoftware/] which contains some of the files refered to in this document along with some of the answers.

Open a new document window by selecting file>new window (or N) and selecting 256 for the array size.

Click the drawer button at the upper right, and then select the Drawing tab at the top of the drawer.

At the upper left of the block of icons select and then click the Histogram tab at the top. Draw lines on the main window and click the Enter 1-0 button or use E. You see several changes. The histogram now has a line at the top and center, and the screen has turned mostly gray. The reason this has happened is that the drawing has been entered into the big array (real part) and the contents of the real part have been displayed on the screen, and the histogram has been changed to reflect the contents of the real part of the big array. A value of zero is displayed at neutral gray, with more positive values darker and negative values a lighter. Notice that under Max |value| the number one is displayed.

Select the popup menu near the top of the main window which says real part and change it to imaginary part. The screen looks blank. Try the other settings. As you move the cursor back and forth over the screen notice the numbers changing in the upper left corner. These give you the coordinates of the point under the cursor and the values stored in the big array for that point.

Now click the Fourier button. The screen changes and the histogram changes as well at the value at the upper left of the histogram. Again look at the real and imaginary views of the big array. Click Fourier again.

You can clear the screen by K or using Clear Screen on the Goodies menu. The big array can be cleared by entering ( E.)a cleared screen into it.

Now lets draw a small rectangle on the screen a little off center. To do this it is useful to enlarge the screen by clicking the little up arrow on the stepper under the word magnification. Click it until the number 8 shows next to the stepper. This value tells you that each pixel of the big array is displayed as an 8 by 8 square on the screen. This makes precise drawing much easier. Now make a small rectangle 3 pixels wide and 2 high. And then put this on the clip board (C). If the rectangle was drawn so that the lower right pixel was located at x = -4 and y = 4 the Fourier transform should look like the one below. Return the magnification to 2, which is the lowest for a 256 array.

The difference between the two images above is the status of the black & white checkbox. You will notice that a blue line appears on the histogram in the black & white checkbox is checked. This line sets the value above which the display is black and below which the pixels are displayed a white. Click on the histogram. The blue line jumps to the point of the click and the main window changes to reflect the change. The cut of value is displayed in the text box at the upper right of the histogram. Change the number in this text box and see the display change. Try -0.0001 for example. Click the enter 1-0 or the enter 1-1 button. Uncheck the black & white checkbox.

By pasting with V you can restore the rectangle to the screen. Try sliding it around on the screen with the three hand tools while it is at high and low magnification to see the difference in action. Enter the rectangle in several different places to see the difference in the Fourier transform.

If you see a feature on the screen you wish to magnify, use the magnifying glass and click on the feature. The screen magnification will increase (if possible) and the feature will jump to the center (again if passable). If the magnification is at the maximum the screen will still jump about trying to center the click spot. Holding down the shift button while clicking will decrease the magnification.

If you choose Graph 3D... while the above view is is the document window, and then choose the default options in the dialog you will see the following.