Focusing DIDSON
Most sonars are fixed focus like an inexpensive camera. Looking at an object close up can cause it to go out of focus, similar to print going out of focus for people who need bifocals. DIDSON has an adjustable focus that automatically sets the focus to be optimum in the center of the selected display range. When one views an object at a closer range and decreases the maximum and/or minimum ranges, the auto-focus adjusts to a closer range as well. Generally focus is transparent to the user. However if the window length is large and the object is near the close edge of the displayed window, the user may need to override the auto-focus and type in the specific range desired for optimum focus. The film shows a block taken in and out of focus. Aliasing is also evident.
