Versatile video CRT display

A sizing circuit for producing a sawtooth signal for driving a cathode ray tube to provide a constant display size regardless of timing changes in the frequency of sync signals, comprising:

• a first charge storing means;
• constant current generating means for charging said first charge storing means in a linear manner;
• means responsive to each incoming sync signal for abruptly discharging said first charge storing means whereby the maximum voltage developed across said first capacitor represents the repetition rate of said sync signal;
• peak detector means coupled to said first charge storing means for storing the peak voltage value developed by said first charge storing means;
• second charge storing means;
• adjustable current drive means for charging said second charge storing means;
• and
• comparing means having first and second inputs for comparing said peak voltage value applied at said first input by said peak detector means against a fixed reference level applied at said second input to develop a signal which represents the ratio of the signals being compared at said first and second inputs for adjusting the current gain of said adjustable current drive means to control the charging rate of said second charge storing means.

Automatic sizing means for converting sync signals of a variable repetition rate to a sawtooth signal having a repetition rate equal to or less than the repetition rate of said sync signals and a control peak value, comprising:

• means responsive to said sync signals for generating a first linear sawtooth signal having a repetition rate equal to the repetition rate of said sync signals;
• means for detecting the peak level of said first sawtooth signal;
• a reference level for use in ratio or difference comparisons;
• means for generating a linear output sawtooth signal of a constant peak value and a repetition rate equal to the repetition rate of said sync signals and at a lesser ratio when sync signals are absent;
• and
• means responsive to said reference level and said peak level for adjusting the ramp of said output sawtooth signal as a function of the ratio of said peak and reference levels.

A comparison circuit for generating a signal representing the ratio of an incoming signal and a fixed reference level comprising:

• first means for converting the incoming signal to a first signal representing the logarithm of said peak value signal;
• second means for converting said fixed reference level to a signal representing the logarithm of said reference level;
• third means for taking the difference between said first and second signals;
• and
• fourth means for converting said difference signal into its antilog for controlling the gain of said adjustable current driving means.

Automatic sizing circuit means for providing sawtooth signals suitable for driving the horizontal and vertical deflection means of cathode ray tubes and the like, responsive to horizontal and vertical sync signals, each of said sawtooth signals being generated by means comprising:

• charge storing means;
• adjustable current drive means for charging said charge storing means in a linear fashion;
• means for determining the peak level of the charge developed in said charge storing means;
• a reference level;
• means comparing said peak level against said predetermined reference level for controlling the current gain of said current drive means;
• means responsive to each sync signal for discharging said charge storing means;
• and
• said charge storing means being charged to a predetermined constant level prior to the initiation of each sync signal.

Dynamic focus control means for focusing the electron beam of a cathode ray tube responsive to first and second sawtooth signals employed for deflecting the electron beam in mutually perpendicular directions, said focus control means comprising:

• first and second means for inverting said first and second sawtooth signals;
• third means generating a signal representing the instantaneous absolute value of the inverted and uninverted first sawtooth signals;
• fourth means for generating a signal representing the instantaneous absolute value of the inverted and uninverted second sawtooth signals;
• and
• means for combining the output signals generated by said third and fourth means including means for converting the current output of said combining means in a non-linear fashion as a function of the instantaneous level of the output signal developed by each of said third and fouth means to obtain dynamic focus of the electron beam over the entire display surface of the cathode ray tube.

Means for selectively coupling the control signals employed to drive the cathode and control grid electrodes of cathode ray tube display tubes and the like while minimizing the skewing or delay experienced by the signals applied to the cathode and control grid due to buffering or inversion operations, comprising:

• first and second gates each having a pair of inputs and being adapted to generate a first output level only when both of its inputs are either high or low and a second output level when its inputs are at different levels;
• third and fourth means coupled to the outputs of said first and second gates respectively, for developing current signals when the outputs of said gates are at said first level whereby one input of each of said gates receives a digital control signal and the other inputs of said gates receive polarity control signals;
• and
• means for controlling the levels of the polarity control signals to couple control signals to the cathode and control grid electrodes of said display tube which are compatible with the operating characteristics of the display tube.

Control circuitry for use in a display system comprising:

• first means for receiving sync signals having a variable frequency for externally controlling the size of the data to be displayed on a fixed raster size;
• second means coupled to said first means and responsive to said variable frequency sync signals for generating a sawtooth deflection signal of a constant peak value and a frequency rate equal to the variable frequency rate of said sync signals;
• a deflection means;
• third means coupled to said second means for driving said deflection means in a linear fashion;
• fourth means for generating an input for electron beam geometric correction waveforms;
• fifth means responsive to said third means for generating a dynamic focusing signal to maintain the electron beam waveform generated by said fourth means in focus regardless of the velocity and position to which the resulting electron beam is deflected and regardless of the manual adjustment of the focus at a position off display center;
• and
• sixth means responsive to digital information including up to four intensity levels for coupling binary control signals differentially to said electron beam waveforms without introducing skewing or delay problems at any display system raster frequency.

Automatic sizing circuit means for generating a sawtooth waveform deflection signal for cathode ray tube displays and the like from incoming sync signals, comprising:

• charge storing means;
• adjusting current drive means for charging said charge storing means in a linear fashion;
• a predetermined reference level;
• means for determining the peak level of the signal developed by said charge storing means;
• means comparing said peak level against said predetermined reference level for controlling the current gain of said current drive means as a function of the ratio of said predetermined reference level and said peak level;
• means responsive to each sync signal for rapidly discharging said charge storing means;
• said charge storing means being charged to said peak level prior to the initiation of each sync signal;
• and
• means for automatically discharging said charge storing means at a predetermined frequency rate in the absence of sync signals to assure generation of said sawtooth deflection signal, said predetermined frequency rate being equal to or less than any frequency rate established by said sync signals.

Automatic sizing circuit means for generating a sawtooth waveform deflection signal for cathode ray tube displays and the like from incoming sync signals, comprising:

• charge storing means;
• adjustable current drive means for charging said charge storing means in a linear fashion;
• a predetermined reference level;
• means for determining the peak level of the signal developed by said charge storing means;
• means comparing said peak level against said predetermined reference level for controlling the current gain of said current drive means as a function of the ratio of said predetermined reference level and said peak level;
• means responsive to each sync signal for rapidly discharging said charge storing means;
• said charge storing means being charged to said peak level prior to the initiation of each sync signal;
• and
• means responsive to the discharging of said charge storing means for generating a blanking pulse having a pulse interval equal to the time interval during which said charge storing means is discharged.

Automatic sizing circuit means for generating a sawtooth waveform deflection signal for cathode ray tube displays and the like from incoming sync signals, comprising:

• charge storing means;
• adjustable current drive means for charging said charge storing means in a linear fashion;
• a predetermined reference level;
• means for determining the peak level of the signal developed by said charge storing means;
• means comparing said peak level against said predetermined reference level for controlling the current gain of said current drive means as a function of the ratio of said predetermined reference level and said peak level, said means for comparing including low pass filter means for stabilizing the comparison operation;
• means responsive to each sync signal for rapidly discharging said charge storing means;
• and
• said charge storing means being charged to said peak level prior to the initiation of each sync signal.

Automatic sizing circuit means for generating a sawtooth waveform deflection signal for cathode ray tube displays and the like from incoming sync signals, comprising:

• charge storing means;
• adjustable current drive means for charging said charge storing means in a linear fashion;
• a predetermined reference level;
• means for determining the peak level of the signal developed by said charge storing means, said peak level determining means comprising delay means having a time constant which is small enough to respond to changes in frequency of said sync signal and large enough to assure linear charging of said charge storing means;
• means comparing said peak level against said predetermined reference level for controlling the current gain of said current drive means as a function of the ratio of said predetermined reference level and said peak level;
• means responsive to each sync signal for rapidly discharging said charge storing means;
• and
• said charge storing means being charged to said peak level prior to the initiation of each sync signal.