Sawtooth waveform generating circuit for utilization in a helmet mounted display

A sawtooth waveform generating circuit for utilization in a helmet mounted display comprising, in combination:

• pulse source means having an output for generating a sync signal having a series of uniformly spaced pulses, the frequency of which is a predetermined value;
• pulse shaping means having an input connected to the output of said pulse source means and an output for narrowing the pulse width of each pulse of said sync signal to a predetermined time period;
• first voltage source means having an output for generating a constant direct current voltage;
• integrating means having an input connected to the output of said first voltage source means for providing at the output thereof a linear ramp voltage in response to the constant direct current voltage provided by said first voltage source means, said linear ramp voltage having a predetermined maximum amplitude;
• switching means having a first terminal connected to the output of said pulse shaping means, a second terminal connected to the input of said integrating means, and a third terminal connected to the output of said integrating means for shorting said integrating means each time one of the pulses of said sync signal is applied to the first terminal thereof such that said linear ramp voltage will drop to a predetermined minimum amplitude so as to form a sawtooth waveform signal, said sawtooth waveform signal having a frequency identical to the frequency of said sync signal, and a direct current component therein;
• coupling means having an input connected to the output of said switching means and an output for removing the direct current component from said sawtooth waveform signal;
• means having a first input connected to the output of said coupling means, a second input connected to the output of said first voltage source means, and an output for variably shifting the voltage level of said sawtooth waveform signal;
• second voltage source means having an output for providing a variable direct current voltage;
• and
• summing means having a first input connected to the output of said voltage level shifting means, a second input connected to the output of said second voltage source means, and an output for amplifying said sawtooth waveform signal, and for combining said amplified sawtooth waveform signal and the variable direct current voltage provided by said second voltage source means so as to form a raster drive signal at the output thereof.