Transversal filter for convoluted image reconstruction

• US 4,149,259 A
• Filed: 05/12/1978
• Issued: 04/10/1979
• Est. Priority Date: 05/16/1975
• Status: Expired due to Term

• Current Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Kowalski, Gunter
• Primary Examiner(s): Atkinson, Charles E.
• Assistant Examiner(s): Krass, Errol A.
• Application Number:
  US05/905,378
• Time in Patent Office: 333 Days
• Field of Search: 364/724, 364/728, 364/414, 364/527, 364/572, 364/604, 364/819, 364/824, 364/825, 250/272, 250/308, 250/510, 250/550, 250/362, 250/369, 250/445 R, 250/445 T, 340/347 AD, 340/347 R, 333/28 R, 333/29, 333/28 T, 328/37, 328/142
• US Class Current: 708/315
• CPC Class Codes: G01J 1/00 Photometry, e.g. photographic exposure meter spectrophotometry G01J3/00; specially adapted for radiation pyrometry G01J5/00 ; exposure meters built in cameras G03B17/06
• CPC Class Codes: G06T 11/005 Specific pre-processing for tomographic reconstruction, e.g. calibration, source positioning, rebinning, scatter correction, retrospective gating
• CPC Class Codes: G11C 19/00 Digital stores in which the information is moved stepwise, e.g. shift registers
• CPC Class Codes: H03H 15/00 Transversal filters electromechanical filters H03H9/46, H03H9/70
• CPC Class Codes: H03H 17/06 Non-recursive filters
• CPC Class Codes: Y10S 378/901 Computer tomography program or processor

Abstract

A device for reconstruction of the absorption values in a layer of a body from measured values taken along strips in the body is disclosed. The absorption values are obtained from the measured values by an analog or a digital device, using a transversal filter in which the measured values are assigned weighting factors in accordance with predetermined criterion.

Claims

1. A signal processing device comprising:

means for supplying a time-sequence of n analog signals; and

transversal filter means which function to perform a convolution on said sequence of signals including;

an analog shift register having a serial input connected to said means for supplying and 2n-1 parallel outputs;

2n-1 resistors, each having first and second terminals, the first terminal of each one of said resistors being connected to a corresponding one of said parallel outputs, the value of a k th resistor being equal to the value of a 2n-k th resistor, for k=1, 2, . . . (2n-1), and

superposition means having inputs connected to said second terminals of said plurality of resistors which function to form a superposition of the signals on said inputs.

2. A device as claimed in claim 1, wherein said superposition means comprises an operational amplifier.

3. A transversal filter for processing a time sequence of digital signals which are presented as a plurality of signal inputs each corresponding to a different significant digit of said signals in said sequence, comprising:

a plurality of digital shift registers, an input of each of said shift registers being connected to a corresponding one of said signal inputs each of said shift registers having a plurality of outputs;

convolving means having inputs connected to said outputs of said shift registers which function to produce a convolution transform of said sequence of signals said convolving means including a plurality of first resistors each having first and second terminals, the first terminal of each of said resistors being connected to a corresponding output of said shift registers;

a plurality of superposition units, each of said superposition units having inputs connected to said respective second terminals of ones of said resistors associated with the corresponding outputs of one of said shift registers; and

a plurality of second resistors, each connected between the output of a corresponding one of said superposition units and an input of adding means, the value of each of the resistors being inversely proportional to 2^k, where k is a non-negative integer which represents the position of the associated digit in said digital signals.

4. In a computed tomography system, the combination comprising:

computed tomography detection means which function to take measurements along strips which are oriented approximately parallel to each other in a plane through a body and to produce a time-sequence of analog signals corresponding thereto; and

transversal filter means which function to perform a convolution on said sequence of signals, having an input connected to said detection means and an output on which a corresponding sequence of convoluted signals is produced, said filter means including;

an analog shift register having a serial input connected to said detection means and a plurality of parallel outputs; and

superposition means which are connected to said parallel outputs of said analog shift register and which function to form a superposition of the signals on said outputs.

5. In a computed tomography system, the combination comprising:

computed tomography detection means which function to take measurements along strips which are approximately parallel to each other in a plane through a body and to produce a time-sequence of digital representations thereof at a plurality of outputs, each output corresponding to a different significant digit of said digital representations; and

transversal filter means including;

a plurality of digital shift registers, each of said shift registers being connected to a corresponding one of said outputs of said detection means;

convolving means having inputs connected to said shift registers which function to perform a convolution on said sequence of signals, said convolving means comprising a plurality of resistors having first and second terminals, the first terminal of each of said resistors being connected to a corresponding output of said shift register;

a plurality of superposition units, each of said superposition units having inputs connected to said second terminals of ones of said resistors and adding means which function to sum outputs of said superposition units.