Curve reader

Claim 2

A curve reader according to claim 1, wherein said scanning means comprises means generating a sawtooth wave voltage; and further comprising means triggering said sawtooth wave generating means by a first reference pulse in an input pulse train comprising two reference pulses and a signal pulse therebetween; means sampling said sawtooth wave voltage with a second reference pulse, said sampled wave being held in a sample-hold circuit; means comparing the resulting sampled signal with a standard voltage; means changing the rate of said scanning to maintain the peak value of said sawtooth wave voltage at said standard voltage, including means feeding back to said sawtooth wave generator the difference between said sampled signal and said standard voltage; and means sampling said sawtooth wave with said signal pulse.

Claim 3

A curve reader according to claim 1, further comprising means for detecting marks recorded at intervals on said recording medium along the direction of motion thereof; means measuring the time interval between said marks; and means controlling, relative to said measured time interval, the scanning rate of said scanning means.

Claim 4

A curve reader according to claim 1, further comprising means for detecting marks recorded at intervals on said recording medium along the direction of motion thereof; and means for measuring the interval between said marks, including means counting horizontal scanning lines, and means controlling, relative to said measured interval between marks, the scanning lines of said scanning means.

Claim 5

A curve reader according to claim 1, further comprising means adding the outputs of said further determining means for a predetermined number of sweeps and means dividing the output of said adding means by said predetermined number of sweeps.

Claim 6

A curve reader according to claim 1, wherein the output of a clock oscillator is gated and counted during the interval between the reference pulses, the counted value is compared with a standard value to control the frequency of oscillation of said clock oscillatOr through negative feedback, and the output of said clock oscillator is gated by the signal pulse and counted, thereby measuring the position of the signal pulse between the reference pulses.

Claim 7

A curve reader according to claim 1, wherein the frequency of oscillation of a variable frequency clock oscillator is determined in accordance with the measurement of the interval between the reference pulses in the input pulse train comprising reference pulses and a signal pulse, and the output of said oscillator is gated by said signal pulse serving as a gate signal and the number of waves or pulses during the gating period is counted to measure the position of the signal pulse between the reference pulses.

Claim 8

A curve reader according to claim 8, wherein the interval between the reference pulses contained in said input pulse train is measured by sampling a sawtooth wave, the frequency of oscillation of the variable frequency oscillator is controlled in accordance with said measurement, the output of said oscillator is gated by said signal pulse serving as a gate signal, and the time-position of the signal pulse between the reference pulses is measured by counting the number of waves of the output during the gating period.

Claim 9

A curve reader according to claim 1, comprising detector means for scanning in a direction perpendicular with respect to the time-axis of a curve to be read out thereby optically detecting the curve and reference lines, gate means adapted to be opened and closed by the output of said detector means, a clock oscillator of which the output is supplied to the input of said gate means, a countercircuit for counting the number of waves of the clock signal which have passed through said gate means so as to produce an output corresponding to the distance between the curve and reference lines, and means for modulating the frequency of oscillation of said oscillator in accordance with the sweep velocity.

Claim 10

A curve reader according to claim 1, comprising a counter circuit adapted for counting the number of pulses generated during the scanning operation for readout, a discriminating circuit for discriminating whether the counted value of said counter circuit coincides with a predetermined value, and an erroneous operation preventing circuit including a control circuit for controlling a readout circuit in accordance with the result of said discrimination.