Data preprocessing system for character recognition systems

Claim 2

A character recognition system including a data preprocessing system for compensating for errors in scanning characters to be recognized, comprising in combination, scanning means for scanning characters to be recognized and generating scanning signals in response to said scanning, amplifier means having an input and an output, the input being connected to said scanning means to receive signals therefrom and amplify the signals, recognition circuit means, and feedback compensating means comprising a Kalman filter network connected to the output of said amplifier means and the input of said recognition circuit means, said filter network being selected and arranged to compensate for inherent transfer characteristics in said scanning means and said amplifier means, said filter network including means for feeding back a portion of the signal at the output of said network to the input of said network, said network having a transfer characteristic similar to the combination of said scanning means and said amplifier means.

Claim 3

A system as claimed in claim 1, said filter further including an active feedback network having a transfer characteristic similar to the inherent response of said scanning means and said amplifier means, and connectiNg the output of said filter to the input thereof to provide negative feedback.

Claim 4

A predictive filter system for a signal channel of a character recognition system comprising, in combination, a first amplifier having an input terminal connected to said channel to receive input signals therefrom, and an output terminal connected to said channel to deliver output signals thereto, a second amplifier having an input terminal and and output terminal, a first passive impedance network connected between the output terminal of said first amplifier and the input terminal of said second amplifier, and a second passive impedance network connected between the output terminal of said second amplifier and the input terminal of said first amplifier, said amplifiers and said networks having a transfer characteristic similar to that of said channel which removes the distortion effects in said channel.

Claim 5

A predictive filter system for a signal channel of a character recognition system comprising, in combination, a first amplifier having an input terminal connected to said channel to receive input signals therefrom, and an output terminal connected to said channel to deliver output signals thereto, a second amplifier having an input terminal and and output terminal, a first passive impedance network connected between the output terminal of said first amplifier and the input terminal of said second amplifier, and a second passive impedance network connected between the output terminal of said second amplifier and the input terminal of said first amplifier, said amplifiers and said networks having a transfer characteristic similar to that of said channel which removes the distortion effects in said channel.

Claim 6

A predictive filter system as claimed in claim 3, in which said first and said second amplifiers are operational amplifiers.

Claim 7

A predictive filter system as claimed in claim 4, in which passive impedance feedback networks are provided for each of said amplifiers and connected between the output terminal and an input terminal of the associated operational amplifier.

Claim 8

A predictive filter system as claimed in claim 5, in which said feedback networks comprise parallel combinations of resistance and capacitance.

Claim 9

A predictive filter system as claimed in claim 3, in which said impedance networks comprise at least a series circuit combination of resistance and capacitance.

Claim 10

A predictive filter system as claimed in claim 7, in which said second impedance network includes a series-parallel resistance-capacitance network.

Claim 11

A predictive filter for a signal channel in a character recognition system comprising, in combination, a filter input terminal, a filter output terminal, a first operating amplifier having a first terminal of two input terminals connected to the filter input terminal and having its output terminal connected to the filter output terminal, a first passive impedance feedback network connected from the output terminal of said first amplifier to the first input terminal thereof, an active feedback network connected form the output terminal of the first amplifier to the second input terminal thereof, comprising a second operating amplifier having a first terminal of two input terminals connected to the output terminal of the first amplifier via a first series impedance network, circuit means connecting the second input terminal of said second amplifier to a common ground connection, a second passive impedance feedback network connected from the output terminal of said second amplifier to the first input terminal of said second amplifier, and a second series inpedance network coupling the output terminal of the second amplifier to the second input terminal of the first amplifier, said filter having a transfer characteristic similar to the characteristic of said channel for removing distortion effects in said channel.

Claim 12

A predictive filter for a signal channel in a character recognition system comprising, in combination, a filter input terminal, a filter output terminal, a first operating amplifier having a first terminal of two input terminals connected to the filter input terminal and having its output terminal connected to the filter output terminal, a first passive impedance feedback network connected from the output terminal of said first amplifier to the first input terminal thereof, an active feedback network connected form the output terminal of the first amplifier to the second input terminal thereof, comprising a second operating amplifier having a first terminal of two input terminals connected to the output terminal of the first amplifier via a first series impedance network, circuit means connecting the second input terminal of said second amplifier to a common ground connection, a second passive impedance feedback network connected from the output terminal of said second amplifier to the first input terminal of said second amplifier, and a second series inpedance network coupling the output terminal of the second amplifier to the second input terminal of the first amplifier, said filter having a transfer characteristic similar to the characteristic of said channel for removing distortion effects in said channel.

Claim 13

A predictive filter network as claimed in claim 9, in which said impedance feedback networks comprise resistance and capacitance elements connected in parallel combinations.