JPS609268A - Method and device for generating time traveling output pulsefrom input puse train - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for generating a clock signal, and more particularly to a method and apparatus for generating a clock signal, and more particularly to a method and apparatus for generating a clock signal, and more particularly for generating a clock signal from an input pulse train so that the clock signal is generated in precise relation to the position of a beam being scanned or plotted. The present invention relates to a method and apparatus for generating a block signal.

Laser beam scanners and plotters are well known in the electro-optical industry. In order to accurately position the pixel on the film, the laser beam must start at the precise moment when the beam covers the point of the pixel that is to be drawn.

Similarly, for accurate scanning of the image, the sampling process must be accelerated. To accomplish this, the laser beam is split into an encoder beam and a scanning (or writing) beam. Both beams are moved by the same oscillating mirror which forms part of the galvanometer assembly. The encoder beam is reflected from the encoder positioned on the X of the film. An encoder consisting of alternating dark and reflected lines automatically collimates the beam back to the galvanometer mirror and finally to the photomultiplier tube. The photomultiplier tube generates a current pulse similar to a laser beam that moves from the reflective part to the non-reflective part of the encoder. The current pulses provide the basic data for generating the clock signals for the scanner's A/D converter, memory, and D/A converter. However, since the laser beam is modulated, it is necessary to compensate for the phase delay within the laser modulator.

Accordingly, a principal object of the present invention is to provide a method and apparatus for generating time-marching output pulses from an input pulse train.

A particular object of the present invention is to provide a method and apparatus for generating a time-marching output pulse train from an input pulse train for use in a phase-locked loop with time-delayed feedback.

Another object of the present invention is to provide a method and apparatus for generating a time-marching single frequency multiplexed output pulse train from an input pulse train.

Still another object of the present invention is to provide a method and apparatus for generating a noiseless one-hour, two-frequency multiplexed output pulse train from an input pulse train.

A feature of the invention is that the method can be accomplished using easily realizable conventional electrical components.

Another feature of the invention is that the apparatus generates a clock signal that occurs in precise relationship to the position of the scanning laser beam and the writing laser beam.

These objects and features, as well as other objects and features, are accomplished by providing a perspective view and a perspective view of an exemplary embodiment of a laser beam scanner or plotter apparatus chosen for illustrative purposes, including circuitry for generating a time-varying output pulse train from an input pulse train. It may be understood by reference to the block diagram and detailed description below.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the accompanying drawings, there is shown a phase locked loop (FLL) generally designated 10 in accordance with the present invention. This phase-locked loop 10 includes a phase comparator 12,
Additional filter 141. Voltage controlled oscillator (VOO) 16
, an additional N frequency divider circuit 18 and a delay circuit 20.

The phase comparator 12 has two inputs, namely phase A
receives the input pulse train and phase B receives the feedback signal. If a phase difference exists between the phase A signal and the phase B signal, an error voltage is generated and the output of voltage controlled oscillator 16 changes until the difference becomes zero. Since phase B is delayed, this VCO advances in phase in response to the input pulse train of phase A.

A delayed feedback phase locking ring is shown in conjunction with a laser beam scanner or laser beam scanner designated by the reference numeral 22. Scanner/
The laser beam of block 22 is the encoder beam 24
and a scanning (or writing) beam 26.

Both beams are moved by an oscillating mirror 28 that is part of a scanner/plotter galvanometer assembly (not shown). The encoder 30 is a photomultiplier tube 3
It consists of dark areas and reflection lines arranged alternately to reflect the encoder beam reaching 4.

A description of such a scanner/plotter is provided by commonly assigned inventor David Renaud Morrill.
.

Mark T., Mason and Paul Marv
He is familiar with the patent application filed by in Green on the same date, ``Scanner/Block Optical System'' (Patent Application No. 1982). However, the above disclosure is sufficient to explain the invention to the painter.

Current pulses from photomultiplier tube 34 are input to the PLL and form the phase A input pulse train to PLL phase comparator 12. In this configuration, the phase-locked loop 10 performs the following four functions.

1) Continuously generate accurate pulse trains even in the presence of noise or dust on the encoder grid.

The encoder photomultiplier tube 34 is responsive to some light input such that light changes or disturbances due to dust spots on the encoder are converted into current pulses. Without the filtering action of PLL 10, these extraneous pulses would falsely trigger subsequent circuitry in scanner/plotter 22.

2) PLL10 encoder beam or missing encoder bar
It also generates a signal when it intersects r). The missing bars are disposed at predetermined positions along the encoder to provide an accurate starting reference for the pixel clock train. The signal from the galvanometer in the reversal or zero velocity position starts a timer (not shown) which after a certain delay activates a missing par detector (not shown). Missing bar is PL
It is detected when the signal from the L voltage controlled oscillator 16 is present and the signal from the encoder is absent.

Since the PLL filter 14 blocks high frequency distortion, the VO
It functions so that O16 is not affected by missing bars and noise.

3) The sixth function of PLL 10 is to multiplex specific frequencies of the encoder. This multiplexing is performed by the PLL phase comparator 12
This is achieved by a divide-by-N circuit 18 disposed in the feedback circuit for the signal. Phase B to phase comparator 12
The signals are delayed and pre-multiplexed (by N division) of the VCO. and) Since phase B is equal to phase A, VC
Phase O is advanced in phase and multiplexing of the phase A encoder signals is performed.

4) The fourth function of PI, Llo is to generate a pulse train with an advanced phase to compensate for the phase lag in the laser modulator (not shown). The necessary phase advance is achieved by inserting a delay circuit 20 between VOO 16 and phase comparator 12 within the PLL.

Although the preferred embodiments of the invention have been described in detail herein, it will be apparent to those skilled in the art that many modifications can be made without departing from the scope of the invention as set forth in the claims below. Will.

[Brief explanation of the drawing]

The attached drawings show a partial perspective view and a block diagram of a mounting surface according to the present invention. The correspondence of reference numerals in the figure is as follows. 10: Phase Locked Loop (PLL') 12: Phase Comparator 14: Filter 16: Voltage Controlled Oscillator (VCO) 18: II Frequency Divider 20: Delay Circuit 22: Galvanometer Assembly (Galvo) 24: Encoder Beam 26: Scanning or grout beam 28: galvanometer mirror 50 = encoder 32: dark and reflected line 54: photomultiplier procedure correction; ,picture. Kazuo Wakasugi, Commissioner of the Japan Patent Office, Showa 8/2019 Showa 8, Showa 8, Showa 8, Showa 8, Patent Application No. 1, Showa 8, Showa 8, 2003, 2013, Name of the invention, 3, Person making the amendment, Relationship with the case, Applicant 4. Agent address: 2-8-1 Toranomon, Minato-ku, Tokyo (Toranomon Electric Building) [Telephone: 03 (502) 1476 (Representative)]
6. Subject of correction

Claims (1)

[Claims] 1) (a) generate an input pulse train; (b) generate a feedback pulse train; (c)
(e) delaying the feedback pulse train, and (e) comparing the phase of the input pulse train with the phase of the delayed feedback pulse train; A method for generating a time-advanced output pulse train from an input pulse train, comprising the steps of: generating a control signal; and adjusting the phase of the feedback pulse train in response to the control signal. 2. The method according to claim 1, further comprising the step of dividing the frequency of the feedback pulse train by N before delaying the feedback pulse train. 3) A method as claimed in claim 1, including the step of filtering the control signal before adjusting the phase of the feedback pulse train in response to the control signal. 4) (a) A device that generates an input pulse train, and (b)
(c) a device that delays the feedback pulse train; (d) a device that compares the phase of the input pulse train with the phase of the feedback signal delayed by the delaying device; (e) the a device for generating a control signal that is a function of a phase difference between an input pulse train and the delayed feedback pulse train; and (f) a device for adjusting the phase of the feedback pulse train in response to the control signal. A device that generates a time-varying output pulse train from an input pulse train. 5) The apparatus according to claim 4, wherein the delay device for delaying the feedback pulse train includes a device for dividing the frequency of the feedback pulse train by N. 6) The apparatus of claim 4, wherein the feedback pulse train generator responsive to the control signal includes a device for filtering the control signal. 7) (a) a laser light beam generating device; (b) an encoder device having a plurality of laser light beam reflecting elements and absorbing elements alternately; and (c) alternatingly crossing the reflecting elements and absorbing elements of the encoder device. (a) a device responsive to the scanning laser light reflected from the encoder device to generate a pulse train signal; a phase comparator that generates a control signal; (f) a feedback pulse train signal generator that responds to the control signal of the phase comparator; (g) a device that delays the feedback pulse train signal; and (1) the phase comparator. a device for providing said pulse train signal as a first input signal to said phase comparator; and a device for providing a delayed feedback pulse train to another input of said phase comparator; 8) The laser beam encoder according to claim 7, wherein the delay device has a frequency dividing device that delays obtaining a new feedback pulse train signal and divides the frequency of the feedback pulse train signal by N. thing. ? ) The laser beam encoder according to claim 7, wherein the feedback pulse train signal generator is responsive to the p-wave control signal and is adapted to react to the control signal generated by the phase comparator. Those with