JPS60142321A - Light beam scanner - Google Patents

Abstract

PURPOSE:To scan a light beam from a constant initial position by detecting the starting point of a main scan, detecting the scanned light beam by a photodetector, and controlling the initial scanning position so that the time when the light beam scans in the section from the starting point to the photodetector is constant. CONSTITUTION:A scan on a recording medium 3 is performed by the rotation of a mirror 10 by a galvanometer 2 to form a scanning line 12 and a subscan is performed to scan the recording surface 13 of the recording medium 3. A photodetector 4 is arranged on the scanning line 12 at an end part of the recording medium 3 to detect the beam. A pulse P4 outputted from the photodetector 4 is inputted to the set terminal S of a flip-flop 15 and a pulse P5 outptted from a means which detects the starting point 6 of the main scan is inputted to the reset terminal R of the flip-flop 15. The galvanometer 3 is so controlled that the number (n) of pulses is invariably n0, and the initial position of the beam is controlled to a fixed position.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a light beam scanning device, and more particularly to a light beam scanning device used for reading or recording image information.

(Technical Background of the Invention) A light beam scanning device is, for example, a light beam scanning device that reflects a light beam from a laser light source by a galvanometer mirror to scan a recording medium in the main scan direction, and scans the recording medium in a direction approximately perpendicular to the main scanning direction. This is a device that records or reads image information by relatively performing sub-scanning using, for example, mechanical feeding means.

Among these, in an image information recording device that records image information, a light beam is transmitted through an acousto-optic modulator (AO), for example.
The image information is recorded by scanning the recording medium with this light beam. In addition, in an image information reading device that reads image information, a light beam is used to scan a recording medium on which image information is recorded, and the reflected light or transmitted light of this light beam is used to detect the information contained in the recording medium. Read the image information contained in the image.

In particular, in a radiation image information reading device that reads a radiation image recorded on a stimulable phosphor sheet made of a stimulable phosphor, a light beam is used as excitation light to scan the phosphor, and this scanning causes the sheet to Image information is obtained by photoelectrically reading the stimulated luminescence light emitted from the sensor.

In either such an image information recording device or an image information reading device, it is desirable that the light beam be scanned in a certain scanning range. That is, it is desirable to perform stable image scanning by starting main scanning from a fixed initial position.

However, the optical system of the light beam scanning device has many mechanically movable parts such as mirrors and galvanometers, and it is extremely difficult to set and maintain these parts in an optimal state by manual adjustment.

For example, even small errors in mirror alignment or light source set position can significantly affect the initial position offset of the scanning beam. Furthermore, the influence that changes in ambient temperature have on the optical system cannot be ignored.

Therefore, in order to obtain a high-quality image by scanning within a fixed scanning range, it is desirable to have an apparatus in which the initial position offset of the scanning beam is also automatically adjusted.

In view of these circumstances, the present inventors have developed a light beam scanning device as described below and have already filed a patent application (Japanese Patent Application No. 182172/1982).

That is, this device includes scanning means for scanning a light beam in response to a first signal, and a plurality of optical gratings arranged in the direction in which the light beam is scanned, and the light beam scans over the array of gratings. a control means for generating a first signal in response to the second signal; and a control means for generating the first signal in response to the second signal. The time from the starting point of scanning of the beam to the end of the grating array is detected, and the initial level of the first signal is adjusted according to the detected time to determine the position of the starting point of scanning of this scanning beam. It is characterized by controlling. This device can always automatically adjust for changes in the initial position offset that occur due to errors caused by manual adjustment of optical components or changes in ambient temperature, and can set the beam scanning to the optimal state. can be retained.

However, such a light beam scanning device has a large number of parts, making the entire device large and difficult to handle, and furthermore, it is expensive to manufacture (because the grid is expensive). There is.

Furthermore, the above-mentioned light beam scanning device also has the problem that if atmospheric dust adheres to the surface of the grid, it is not possible to obtain a stable synchronization signal for controlling the scanning of the light beam from the grid. There is.

(Objective of the Invention) The present invention was made to solve the above-mentioned problems, and is inexpensive to manufacture and easy to handle, and furthermore, it is possible to control the scanning of a light beam even if it is contaminated by dust. It is an object of the present invention to provide a light beam scanning device that can stably obtain a constant synchronization signal and maintain the initial position (starting point) of light beam scanning at a constant position.

(Constitution of the Invention) The light beam scanning device of the present invention includes a photodetector such as a phototransistor in the main scanning area, and uses this photodetector to determine the scanning time from the start of main scanning to this photodetector. The initial position of the main scanning is controlled so that a predetermined number of pulses of a pulse signal having a constant period are always manually input within this time. .

Specifically, by receiving an output signal from a means for detecting the initial position (for example, the starting point of main scanning) and an output pulse from a photodetector provided at an arbitrary position in the main scanning area, the photodetector is detected from the scanning starting point. A square wave signal indicating the time period between The number of pulses of the pulse signal input within the corresponding time is counted and compared with a fixed reference value, and the scanning start point of the main scanning means is controlled based on the difference, so that the light beam always scans from a fixed initial position. It was designed so that

As described above, a square wave signal indicating the scanning period from the main scanning start point to a predetermined position and a pulse signal having a predetermined period generated by the pulse generating means are input to the gate means. The pulses input within the time corresponding to the scanning period (usually the high level period of the square wave) are output, and as this gate means, for example, 2 horn 1 output (7) AND'7''- TTL
<741SO8) may be used. Next, the pulse signal output from the gate means described above is input to the counting means, which counts the number of pulses and outputs the counted value n as, for example, a decimal digital value.

As this counting means, for example, a decimal counter TTL
(74LS196) may be used.

Next, the Todoroki 1 numerical value n and the reference setting value n outputted from the counting means. (set by an external digital volume or the like) is input to the comparing means, n and -n are calculated, and a difference signal (for example, voltage Δ■) proportional to this difference value is generated.

This difference signal is added to the previously output signal,
The signal is inputted to an integrator constituted by, for example, an operational amplifier, converted into a ramp function, that is, a sawtooth wave signal, outputted, and inputted to the drive circuit of the main scanning means.

Examples of the main scanning means used in the present invention include a galvanometer mirror. Further, the photodetector used in the present invention may be of any type as long as it can detect a light beam and output a positive logic pulse of about +5V, and for example, a commonly available phototransistor may be used.

In addition, as the square wave generating means used in the present invention, for example, a flip-flop diode L (74LS74) can be mentioned.

In the present invention, various known means are used for detecting the starting point of main scanning. For example, the main scanning periodic signal (pulse) can be used as is, or a pulse obtained by detecting the falling or rising position of the main scanning sawtooth wave with a comparator or the like can be used. There is no limit to the width of the pulse as used herein, and it also includes pulses with a large width that use only the rising or falling portions.

(Effects of the Invention) According to the light beam scanning device of the present invention, the starting point of main scanning is detected, and the light beam scanned by the photodetector arranged within this main scanning area is detected, thereby starting from the starting point. Since the initial scan position is controlled so that the time it takes for the light beam to scan the area up to the photodetector is constant, it is possible to scan the light beam from a constant initial position. When this device is applied to an image information recording device, image information can be accurately recorded in a certain range, while when this light beam scanning device is applied to an image information reading device, image information can be recorded in a certain range. can be read accurately.

In addition, this light beam scanning device does not require expensive optical components as a light beam sensor, and only requires the use of a photodetector such as a phototransistor that outputs one pulse, so it is inexpensive to manufacture. is extremely cheap and easy to handle. In general, even if the light-receiving surface of this photodetector is somewhat contaminated with dust or the like, output pulses can be obtained and there is no functional problem.

(Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a perspective view conceptually showing an embodiment of a light beam scanning device according to the present invention, and this device basically consists of a light source 1 consisting of a laser oscillator that generates a laser light beam 8.
and a galvanometer 2 that sweeps the light beam 8.

A mirror 10 is supported on the rotating shaft 9 of the galvanometer 2, and maintains a mechanical neutral position when the galvanometer 2 is not driven. When the galvanometer is driven, the mirror 10 can be rotated to either side of the neutral position depending on the drive current, and the beam can be swept from 118 to 11B. For example, applying a negative voltage to galvanometer 2 will sweep the beam to the side of IIA, while a positive voltage will sweep the beam to the side of IIA.
It is swept to the B side and maintains a nearly neutral position at 0 voltage. As will be described later, by changing the negative or positive voltage level, the position of the starting point 6 or the ending point 7 of scanning by the beams 11A or 11B is adjusted, and the rate of voltage change between the starting point 6 and the ending point 7, that is, the voltage change, is adjusted. In the case of a straight line, the scanning speed is adjusted by changing the slope.

When the beams 11A and 11B scan the recording medium 3, they also slightly scan the outside of the recording medium 3.

The recording medium 3 can store, for example, a sheet-like image (
This is a recording medium (which may include characters), and is fed in the direction of arrow B by a feeding mechanism (not shown). Therefore, main scanning of the recording medium 3 is performed by rotation of the mirror 10 by the galvanometer 2 to form a scanning line 12, and sub-scanning is performed by feeding the recording medium 3 in the direction of arrow B. The recording surface 13 of the recording medium 3 is scanned.

As shown in the figure, a photodetector 4 is disposed on the scanning line 12 at the end of the recording medium 3 to perform beam detection.

In this embodiment, the photodetector 4 receives a beam on its light receiving surface and outputs a positive logic pulse of TT level.
・Transistors are used.

When this device is applied to a reading device, information from the recording medium 3 is read by reflection or transmission of the beams 11A and 11B on the recording surface 13 by this scanning. As an example, if the recording medium 3 is an image recording medium containing a stimulable phosphor that accelerates photostimulability, the phosphor is excited to emit light by scanning with the laser beams 11A or 11B, and thereby the image is recorded. It is possible to read radiation image information. When this device is applied to a recording device, the recording medium 3 includes a photosensitive material, and the laser beam 8 from the laser light source 1 is transmitted through an acousto-optic modulator (AO).
An image can be recorded on a photosensitive material by modulating it according to an information signal by some modulation means (not shown) such as M).

FIG. 2 shows an example of a circuit for controlling main scanning of this apparatus. In this figure, elements that are the same as those shown in FIG. 1 are designated by the same reference numerals. The pulse P4 output from the photodetector 4 is input to the set terminal S of the flip 70 tube 15 (R-8 type), and is also output from the means (for example, a synchronization signal detector) 5 for detecting the starting point 6 of the main scan. The generated pulse P5 is flipped.
It is input to the reset terminal R of the flop 15. At this time,
From the output terminal Q, a high level square wave pulse p indicating a scanning period between the photodetector 4 and the starting point detector 5 is output.
a is output. This timing chart is shown in FIG.

This square wave pulse is applied to an AND gate 16 (e.g. 74L).
A pulse signal pb from an oscillator 17 that oscillates pulses with a constant period is input to a second terminal of the gate 16. Also, this gate 1
From the output terminal 6, a number of pulses pc corresponding to the number of pulses Pb inputted to the second terminal of the gate 16 within a time corresponding to the scanning period is outputted.

This timing chart is shown in FIG.

The pulse PC output from this gate 16 is the counter 1
For example, the counted value n is inputted to a decimal counter 74LS196) and counted, and the counted value n is sent to the comparator circuit 19. On the other hand, the reference setting value n, which is the number of pulses desired to be generated within the time corresponding to this scanning period, is set by the external digital volumes 20a and 20b, and the comparison circuit 1
Sent on 9th. The comparison circuit 19 compares the count value n with the reference setting value n, ) and generates a voltage ΔV proportional to the difference value rlo -n. This voltage ΔV is the reference voltage V (
This voltage is superimposed on the voltage that had been output until then and is output as the voltage applied to the lamp generator 21. This output has a sawtooth waveform and is supplied to the galvanometer 2.

Galvanometer mirror 10 is rotated by this sawtooth output and beam 8 is swept from 11A to 118 to form scan line 12. This beam also scans the photodetector 4 at the same time, and the photodetector 4 generates the aforementioned pulse P4. Furthermore, a detection pulse P5 at the starting point 6 is also generated at the same time.

The number of pulses n between the outputs from the detector 4 and the starting point detector 5
When the difference ΔV between and the predetermined number of pulses n□ is zero, the initial position of the galvanometer mirror 10 is maintained as it is, and when this difference is large, the initial position is changed to reduce this difference.

In this way, the galvanometer 2 is controlled so that the number of pulses n is always n□, and thereby the initial position of the beam is controlled to be constant.

The starting point 6 of the main scan may be detected using the synchronization pulse as described above, but it may also be detected by detecting the falling or rising edge of the sawtooth wave galvanometer drive signal.

[Brief explanation of drawings]

1 is a conceptual perspective view showing an embodiment of a light beam scanning device according to the present invention, FIG. 2 is a block diagram showing an example of a circuit for controlling the device shown in FIG. 1, and FIG. 4 is a timing chart showing the output of the photodetector and the output of the flip 70 tube of the circuit shown in FIG. 4, and the AN of the circuit shown in FIG.
FIG. 5 is a timing chart showing the input and output of the D gate, FIG. 5 is a 70-channel diagram showing the waveforms and timings appearing in each part of the circuit shown in FIG. 2, and FIG. 6 is a schematic diagram showing an example of the ramp generator in FIG. It is a circuit diagram. 1... Light I 2... Galvanometer 3... Recording medium 4... Photodetector 5... Start point detection means 10... Galvanometer mirror 15... Flip-flop 16... AND gate 17... Oscillator 18...
Counter 19... Comparison circuit 21... Engraving of lamp generator drawing (no changes in content) 6 Figure 2 Figure 3 Figure 4 Figure 0 (Voluntary) Procedure City - Shoshu March 2, 1982 Commissioner of the Japan Patent Office 1. Indication of the case Patent Application No. 58-251917 2. Name of the invention Optical beam scanning device 3. Relationship with the case of the person making the amendment Patent applicant's address Address 210 Nakanuma, Minamiashigara City, Kanagawa Prefecture Name: Tomiju Photo Noilm Co., Ltd. 4, Agent: 5-2-1-6, Roppongi, Minato-ku, Tokyo Number of inventions to be increased by the amendment: None 7: 1lliIJ3 of "Detailed Description of the Invention in Part 1 of Specification Subject to Amendment P1" and drawings 1) ``Arises due to U...'' on page 6 of the specification'' followed by ``of the scanning beam''
Insert. 2) On page 9, line 19, "period" is corrected to "synchronization." 3) Page 14, lines 5 to 10 1 - The pulse P4 output from the photodetector 4 is...
・Input. ” to “Start point 6 of main scanning of laser beam 8
The pulse P5 output from the means (for example, a synchronization signal detector) 5 for detecting the
The pulse P4 output from the photodetector 4 is input to the reset terminal R of the flip-70 tube 15. ” he corrected. 4> On page 161, lines 11 and 12, "this photodetector 4 and the starting point detector 5" are corrected to "the starting point detector 5 and the photodetector 4."5> Insert [based on the starting point detector 5] after the second line [-Also] on page 16. 6) In the fourth line of the same page, correct "detector 4 and starting point detector 5" to "starting point detector 5 and photodetector 4." 7) Lines 13-14 of the same page [The starting point 6 may be detected using the synchronizing pulse as described above. You can use Pulse as is.
I corrected Riru. 8> Correct the attached directions in Figures 2 and 3. (Opening Ceremony for Proceeding Amendment) Dear Commissioner of the Japan Patent Office, April 25, 1980, Application No. 1, Indication of the Case, Patent Application No. 1982-251917, 2, Name of the Invention, Light Beam Scanning Device 3, Person Making the Amendment, Relationship with the Case, Patent Application Person Address: 210 Nakanuma, Minamiashigara City, Kanagawa Prefecture Name: Fuji Photo Film Co., Ltd. 4 Agent: 5-2-1 Roppongi, Minato-ku, Tokyo @

Claims (1)

[Scope of Claims] 1) Scanning means that scans a light beam over a subject according to a scanning means control signal, and a scanning means that is disposed within the scanning range of this light beam and that detects this light beam and outputs a pulse. a photodetector; a start point detection means for detecting the start point of each scan of the scanning means and outputting a signal corresponding to the start point; means for calculating the time between pulses; and control means for checking the initial level of the scanning means control signal in accordance with the calculated time to control the position of the starting point of scanning of the light beam. Features a light beam scanning device. 2) The means for calculating the time between the signal corresponding to the starting point and the output pulse of the photodetector receives a pulse from an oscillator that outputs pulses with a constant period, and calculates the time between the signal corresponding to the starting point and the photodetector. 2. The light beam according to claim 1, further comprising a counter that receives the output pulses of the device and counts the number of pulses of the constant period inputted between these signals and the pulses. scanning device. 3) The control means comprises a comparison circuit that compares the output of the counter with a predetermined force per unit number, and means for adjusting the initial level of the scanning means control signal in accordance with the output of the comparison circuit. The second claim characterized in
The optical beam scanning device described in 2. 4) The light according to claim 3, wherein the means for adjusting the initial level adjusts the initial level so as to reduce the difference between the output of the counter and the predetermined count number. Beam scanning device.