JPH0797185B2 - Galvanometer mirror adjustment method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for adjusting a galvanometer mirror, and more specifically, it scans an object to be scanned with a light beam deflected by the galvanometer mirror or reads an image or the like. The present invention relates to a method for adjusting an offset of a galvanometer mirror incorporated in a light beam scanning device for recording.

BACKGROUND OF THE INVENTION Conventionally, an object to be scanned is main-scanned by a light beam deflected in a one-dimensional direction by a galvanometer mirror, which is an optical deflector, and the object to be scanned is in a direction substantially perpendicular to the main-scanning direction (sub scanning 2. Description of the Related Art A light beam scanning device configured to two-dimensionally scan an object to be scanned by relatively moving in a scanning direction) is widely used as various recording devices and reading devices.

For example, a stimulable phosphor sheet on which radiation image information is stored and recorded is scanned by excitation light such as a laser beam to generate stimulated emission light having the radiation image information, and this stimulated emission light is emitted by a photomultiplier or the like. A radiation image information reading apparatus configured to obtain an image signal by photoelectrically detecting using a detecting means is a good example. Here, the stimulable phosphor means radiation (X-ray, α-ray, β-ray, γ
Line, electron beam, ultraviolet ray, etc.) is a phosphor that accumulates a portion of this radiation energy and then stimulates emission light according to the accumulated energy by irradiating excitation light such as visible light. Further, the stimulable phosphor sheet means a sheet having a layer made of the stimulable phosphor.

Incidentally, in the radiation image information reading apparatus, it is desirable that the reading start position of the scanning line of the light beam for the main scanning of the stimulable phosphor sheet and the main scanning speed (reading speed) are constant. That is, if the reading start position for each scanning line (hereinafter, simply referred to as the reading start position) is constant, the image information from the predetermined position of the stimulable phosphor sheet is always obtained accurately, while the main scanning is performed. If the speed is constant,
This is because the sampling time per pixel of the image information becomes equal and the image information can be read without unevenness. Then, the reading start position and the main scanning speed are
Each changes depending on the position offset of the galvanometer mirror that deflects the light beam and the deflection angular velocity.

However, since the galvanometer mirror has a large number of mechanically movable parts, its position offset and deflection range may mechanically slightly shift due to changes in environmental conditions such as ambient temperature. In this case, even if there is a slight mechanical shift, for example, a slight positional shift of the alignment of the mirror, the reading start position on the stimulable phosphor sheet and the scanning speed of the light beam change considerably.

Therefore, the following adjustment work is performed in order to eliminate the fluctuations in the reading start position and the scanning speed due to the environmental conditions. That is, first, a scanning light beam is split by a half mirror or the like, and the split synchronization light beam is provided with an optical grating (hereinafter referred to as a light-dark pattern in which light-transmitting portions and non-light-transmitting portions are alternately arranged. , Grid) to generate pulsed light by scanning. Then, a synchronizing signal is generated based on the grid signal obtained from this pulsed light, and the synchronizing signal is used to drive the galvanometer mirror to a DC offset and deflection angular velocity of a sawtooth electric signal (hereinafter referred to as a sawtooth signal). The corresponding inclination (the amount of change in current or voltage per unit time, hereinafter simply referred to as the scanning speed) is varied to adjust the position offset and deflection angular velocity of the galvanometer mirror.

When adjusting the DC offset and the deflection angular velocity in this way, a reference signal for determining the reading start position of the stimulable phosphor sheet is required. As a measure for obtaining this reference signal, conventionally, a non-transmissive portion arranged at the end of the grid is formed wide, and the pulsed light generated first after scanning the wide non-transmissive portion with a synchronizing light beam is used. A light detection sensor is arranged near the tip position of the scanning area of the synchronizing light beam corresponding to the measure for using the reference signal or the reading start position of the stimulable phosphor sheet, and the pulsed light obtained from this light detection sensor is used as a reference. Measures such as signaling are adopted.

However, if you choose such a strategy,
The deviation of the initial offset of the galvanometer mirror described above is considerably large, and therefore, the scanning area of the synchronizing light beam may deviate from the wide non-transmissive portion on the grid or the light detection sensor arranged corresponding to the reading start position. Occurs.
In this case, the reference signal for adjusting the DC offset and the scanning speed is no longer generated, so that the galvanometer mirror cannot be automatically adjusted.

[Object of the Invention] The present invention has been made in order to overcome the above-described inconvenience, and is to form a plurality of phase modulation portions of a light-dark pattern on the grid and scan the grid with a light beam for synchronization. By adjusting the DC offset of the sawtooth wave signal that drives the galvanometer mirror so that the number of pulses related to the phase modulation portion becomes a preset predetermined number of pulses obtained by the galvanometer mirror. It is an object of the present invention to provide a method for adjusting a galvanometer mirror that makes it possible to automatically adjust an initial position offset.

[Means for Achieving the Object] In order to achieve the above object, the present invention performs main scanning on an object to be scanned by a light beam deflected in a one-dimensional direction by a galvanometer mirror, and also performs main scanning on the object to be scanned. When the object to be scanned is two-dimensionally scanned by moving relatively in the direction substantially orthogonal to the direction to record or read character information, image information, etc., a plurality of bright and dark patterns are provided in the main scanning direction by the synchronizing light beam. Is a method of adjusting a galvanometer mirror used in a light beam scanning device for obtaining a synchronizing signal by photoelectrically detecting a light beam that has passed through the grid in which the grid is formed. Forming N modulation units (N is a natural number of 2 or more),
When scanning a grid having a plurality of phase modulators with a synchronizing light beam, the galvanometer mirror offset is set so that the number of detected phase modulators per scan is M (M is a natural number that satisfies M ≦ N). It is characterized by adjusting.

[Embodiment] Next, the galvanometer mirror adjusting method according to the present invention will be described in detail below with reference to preferred embodiments of an apparatus for performing the same, with reference to the accompanying drawings.

In FIG. 1, reference numeral 10 indicates a schematic configuration of a radiation image information reading apparatus incorporating an apparatus for carrying out the galvanometer mirror adjusting method according to the present invention. Laser scanning for scanning the radiation image information reading device 10 with the radiation image information recorded on the scanned object, for example, the stimulable phosphor sheet S conveyed in the sub-scanning direction (direction of arrow A) by the light beam La. The unit 12, an image reading unit 14 for photoelectrically converting light having image information obtained by scanning with the light beam La, a scanning position of the light beam Lb, and a synchronization signal generation unit 16 for generating a synchronization signal. , A galvanometer mirror driving unit 18 for driving the galvanometer mirror 17, and a signal processing unit 20 for converting a signal from the image reading unit 14 into digital image information based on a synchronization signal and storing the digital image information in an image memory (not shown). Is composed of.

Therefore, the light beam L emitted from the laser light source 22 of the laser scanning unit 12 passes through the beam expander 24 to be formed into a beam having a desired thickness, and then oscillates in the direction of arrow B to move the light beam. It is incident on the galvanometer mirror 17 that reflects L and is reflected and deflected.

The light beam L reflected and deflected by the oscillating motion of the galvanometer mirror 17 passes through the scanning lens 26 such as an fθ lens disposed in the optical path, and then is disposed on the optical path so as to extend in the main scanning direction. Incident on the half mirror 28. The half mirror 28 reflects the amount of light beam necessary for scanning among the incident light beams L as a light beam La for scanning, and transmits the remaining light beam as a light beam Lb for synchronization. The light beam La reflected by the half mirror 28 is focused on the stimulable phosphor sheet S disposed on the optical path and scans the stimulable phosphor sheet S in the main scanning direction (direction of arrow C).

The image reading unit 14 includes a light guide 30 that collects stimulated emission light generated from the stimulable phosphor sheet S that is excited by the light beam La, and a photomultiplier that photoelectrically converts the collected stimulated emission light. And pliers 32. In this case, the light guide 30
The light-receiving surface of the stimulated emission light in is located near the stimulable phosphor sheet S along the main scanning direction. The electric signal after photoelectric conversion of the photomultiplier 32 is an A / D converter 34 in the signal processing unit 20 via a log amplifier 33.
It is introduced to the signal input terminal of.

On the other hand, the synchronization signal generator 16 includes a transmissive part 36a that transmits the light beam Lb that has passed through the half mirror 28, a wide transmissive part 36c that will be described later, and a non-transmissive part 3 that reflects the light beam Lb.
A grid in which bright and dark patterns 37 composed of 6b are alternately arranged in the scanning direction of the light beam Lb (direction of arrow F).
36, a cylindrical light guide 38 arranged along the rear of the grid 36, and an optical sensor 40 provided at both ends of the light guide 38 for detecting the light beam Lb transmitted from the grid 36.
a, 40b and the optical sensor 40a, a waveform shaping circuit 42 for shaping the waveform of the reference grid signal G _R output from 40b, based on the grid clock G _G is an output signal of the waveform-shaped from the waveform shaping circuit 42 generating a synchronous clock T _R consists synchronizing signal generating circuit 44.

In this case, as described above, the scanning light beam La needs to start substantial reading (hereinafter referred to as effective scanning) from a predetermined position in the main scanning direction on the stimulable phosphor sheet S. The starting point of effective scanning needs to be controlled to the same position for each scanning line. Therefore, in this apparatus, the light-dark pattern 37 of the grid 36 has a characteristic configuration shown in FIG. That is,
The bright and dark pattern 37 of the grid 36 is basically a standard width transmission part 36a that transmits the synchronizing light beam Lb and the synchronizing light beam Lb.
The non-transmissive portions 36b that block b are alternately formed at a constant pitch, but the pitch is different from these portions at predetermined intervals, that is, a phase-modulated wide transparent portion 36c is formed. There is. In addition, in this embodiment, the number N of the wide transparent portions 36c is four. As will be described later, the number N of the wide transparent portions 36c is at least two in order to carry out the present invention, and is 3 for the reason described later.
It is more preferable to form more than one.

On the other hand, the synchronous clock T _R from the synchronizing signal generating circuit 44 is introduced to the synchronization signal input terminal of the A / D converter 34. In this case, the synchronizing signal generating circuit 44 is configured, for example, as a frequency synthesizer, a grid clock G _G by a predetermined multiple multiplication to generate a synchronous clock T _R corresponding so-called the pixel clock.

FIG. 3 is a block diagram showing a schematic configuration of the drive unit 18. The drive unit 18 detects the phase-modulated pulse P _m related to the wide transmission unit 36c included in the grid clock G _G using the synchronization clock T _R generated by the synchronization signal generation circuit 44, and corresponds to the modulation unit. A modulation detection unit 50 that outputs a pulse G _H (hereinafter referred to as a modulation detection pulse), and the modulation detection pulse G _H
An offset detecting unit 52 for detecting a swinging motion offset of the galvanometer mirror 17 based on the grid clock G _G
The speed detection unit 54 for detecting the scanning speed of the galvanometer mirror 17 based on the time of generating the predetermined number of pulses, the predetermined offset data D _OFF and the predetermined offset data from the output signals of the offset detection unit 52 and the speed detection unit 54. Speed data D _SP to D / A
A control unit 60 that supplies the converters 56 and 58 respectively, an integrator 62 that is a sawtooth wave generator that generates a sawtooth wave signal by integrating the output signal of the D / A converter 58, and an output signal of the integrator 62. And a summing amplifier 69 for summing the output signals of the D / A converter 56 and a galva driver 70 for converting the output signal of the summing amplifier 69 into a predetermined drive current for driving the galvanometer mirror 17.

The radiation image information reading apparatus incorporating the apparatus for carrying out the galvanometer mirror adjusting method according to the present invention is basically constructed as described above. Next, its operation and effect will be explained.

In this device, as described above, the galvanometer mirror 17
The reading start position E ₁ (see FIG. 1) and the scanning speed V from the reading start position E ₁ to the reading end position E ₂ are determined. In this case, the reading start position E ₁ and the scanning speed V can be determined by adjusting the sawtooth wave signal W (see FIG. 2B) repeatedly supplied to the galvanometer mirror 17. That is, the amplitude W _A of the sawtooth wave signal W is
Considering that it corresponds to E ₃ (see FIG. 1), the reading start position E ₁ can be determined by adjusting the DC offset W _B of the sawtooth wave signal W, and the inclination of the sawtooth wave signal W, that is, the scanning period T It will be easily appreciated that the predetermined reading speed V can be determined by adjusting the amplitude change W _A within ₀ (hereinafter, simply referred to as the amplitude W _A ).

Therefore, first, in the control unit 60, the DC offset W _B
And the initial value of the amplitude W _A is appropriately set, and the sawtooth wave signal W related to the set value is supplied from the galvanic driver 70 to the galvanometer mirror 17.

Referring again to FIG. 1, the light beam L emitted from the laser light source 22 is deflected in the direction of arrow B by the galvanometer mirror 17 supplied with the sawtooth wave signal W. Of the light beam L thus deflected, the light beam Lb which has passed through the scanning lens 26 and the half mirror 28 scans on the grid 36 in the arrow F direction. In this case, the transparent part 36 of the standard width of the grid 36
The light beam Lb that has passed through a and the wide transmission part 36c is a light guide.
Light that is incident on the light guide 38, is diffused in various different directions by a diffusion zone (not shown) formed on the opposite side of the light guide Lb from the incident side of the light beam Lb, and is repeatedly totally reflected in the light guide 38. The beam Lb reaches the optical sensors 40a and 40b and is photoelectrically converted,
The reference grid signal G _R including the wide light pulse related to the wide transmission part 36c is generated. Since this reference grid signal G _R is an analog signal, it should be used as a timing signal.
A waveform shaping circuit 42 including a comparator and performing a comparison operation is converted into a steep grid clock G _G (see FIG. 2C) of the rising and falling portions of the waveform to drive the driving unit 18.
And is introduced into the synchronization signal generation circuit 44.

Next, the galvanometer mirror 17 is adjusted. When adjusting the galvanometer mirror 17,
The adjustment of the offset and the adjustment of the amplitude related to the scanning speed are not independent of each other, and if one is adjusted, the other changes by a predetermined amount.Therefore, the adjustment of the offset and the adjustment of the amplitude are repeated several times. Adjust so that it falls within the specified setting range.

Therefore, first, the adjustment of the offset will be described. In this case, as described above, the modulation detector 50 includes a waveform shaping circuit.
Grid the clock G _G is introduced from 42, the grid clock G _G from the synchronizing signal generating circuit 44 is given the multiplied synchronized clock T _R (see FIG. 2 d) is introduced.
As can be seen from FIG. 2c, the grid clock G _G has the standard pulse P _s and the wide pulse P _m corresponding to the transparent portion 36a and the wide transparent portion 36c of the grid 36. Therefore, the configuration of the modulation detection unit 50 that detects only the wide pulse P _m from the grid clock G _G is the clock pulse P _c of the synchronous clock T _R generated during the generation period of the standard pulse P _s and the wide pulse P _m.
A wide pulse only when the number of pulses is a predetermined number or more
It may be composed of a counter and a timer selected as P _m . The modulation detection pulse G _H thus detected by the modulation detector 50 is shown in FIG. 2e.

In FIG. 2e, the number of the pulses P _H existing in the modulation detection pulse G _H is all four, but now, for example, the grid is changed by the offset shift of the galvanometer mirror 17.
It is assumed that the scanning range of the light beam Lb on 36 is shifted to the right as shown in FIG. 3 and the deflection angle θ ₁ and only the fourth pulse PH ₄ can be detected. A method of adjusting the offset of the mirror 17 will be described.

First, when the entire main scanning length is scanned, it is known in advance that the total number N of the pulses P _H related to the modulation detection pulse G _H is 4, so the offset value is gradually reduced and the pulse is increased each time.
The number of P counts the number of _H pulse P _H to reduce the offset until four. Next, by inputting the size of the stimulable phosphor sheet S into the control unit 60 from an input means (not shown) in advance, the control unit 60 automatically determines a predetermined number M (corresponding to this embodiment) corresponding to a certain scanning mode. Then, M is 4 or less), and the offset is increased gradually so that the pulse P _H is detected.

The prescribed number M is the offset value x _m that is finally set.
Based on (described later), the number of detections of the pulse P _H when the light beam Lb is scanned once in the direction of arrow F on the grid 36, that is, the number of detections of the phase modulation unit, in other words, the wide transmission unit.
This is equal to the number of detections of 36c (see FIG. 2a). Now the prescribed number M
However, for example, it is assumed that M = 3 is determined. Therefore, after increasing the offset value until the number of pulses P _H is changed from four to the specified number M = 3 (three pulses P _H2 , P _H3 , and P _H4 shown in FIG. _2e ), the specified number is increased. M = 3 the number of pulses P _H is further increased offset value such that M-1 = 2 with respect to the pulse P offset value immediately after the number becomes M-1 = 2 for _H x _m-1 Ask for. This offset value x _m-1 is D / A
It is the set value D _off for the converter 56. Next, the offset is further increased to obtain an offset value x _{m-2 at} which the number of pulses P _H becomes M-2 = 1. From the above results, the offset value x _m to be set in the galvanometer mirror 17 is X _m = x _m-1
-(X _m-2 -x _m-1 ) / 2 = 3 / 2x _m-1 -1 / 2x _m-2 (see the number line shown in FIG. 2f). As can be easily understood from FIG. 2f, the offset value x _m is set to a value corresponding to the substantially central portion of the adjacent pulse P _H to avoid erroneous detection of the pulse P _H.

By the way, when the prescribed number M is 2 or more, the offset value may be adjusted by the above procedure, but when the prescribed number M is 1, the above method cannot be adopted, and therefore the method described below is used. That is, if the prescribed number M is set to M = 1, firstly, after the offset number of pulses P _H of 3, it obtains the offset value x ₃ pulse P _H is 2, then
The offset value is gradually increased to obtain an offset value x _{2 at} which the number of pulses P _H is 1. As a result, the offset value x ₁ is
It will be easily understood that 3 / 2x ₂ −1 / 2x ₃ should be used.

The method of adjusting the offset described above is based on the light beam Lb
Is the adjustment method when the scanning range of is shifted to the right of the grid 36, even if the scanning range is shifted to the left, the first step, that is, the pulse related to the modulation detection pulse G _H It may be changed to adjust to a method of increasing the offset in the process of finding the total number of P _H.

After adjusting the offset in this way, next, the scanning speed V
Adjust. The scanning speed V is adjusted by, for example, D / so that a predetermined number of pulses P _S of the grid clock G _G are generated after a first pulse P _H1 of the modulation detection pulse G _H is generated for a predetermined time. Amplitude value to be set in A converter 58 D _SP
Should be adjusted. When the amplitude is adjusted in this way, the offset also changes, so the above-described offset adjustment and the speed adjustment are repeated until both are within a preset set value.

After the sawtooth wave signal W is properly adjusted as described above, the stimulable phosphor sheet S is set and the image reading is started. In this case, the surface of the stimulable phosphor sheet S is irradiated with the light beam La emitted from the laser light source 22 in the main scanning direction, and the image information of the subject recorded on the stimulable phosphor sheet S is stimulated. It is taken out as emitted light. This stimulated emission light is incident on the photomultiplier 32 via the light guide 30 arranged in the main scanning direction of the stimulable phosphor sheet S, and is converted into an electric signal. And photomultiplier
The electrical signal from 32 is passed through the log amp 33 to the A / D converter 34
Signal is applied to the signal input terminal of the above, and this signal is A / D converted for each pulse of the synchronous clock T _S. The image signal thus obtained is subjected to signal processing such as gradation processing and frequency processing by a signal processor (not shown) and then visible on an image record carrier such as a film or a display such as a CRT. Reproduced as an image.

Although the above embodiment has been described with respect to a device for reading with a light beam scanning device, it is needless to say that it can be applied to a device for performing image recording on an image record carrier such as a film by light beam scanning.

[Effects of the Invention] As described above, according to the present invention, the number of pulses applied to the modulation grid portion among the pulses obtained by scanning the grid formed with a plurality of phase modulation portions with the light beam for synchronization. Is adjusted to a predetermined number set in advance. Therefore, the position offset of the galvanometer mirror can be adjusted accurately. Therefore, the reading start position or the recording start position of the object to be scanned can be accurately obtained by using the galvanometer mirror thus adjusted, and as a result, a finely reproduced image can always be obtained.

Although the present invention has been described with reference to the preferred embodiment, the present invention is not limited to this embodiment,
It goes without saying that various improvements and design changes can be made without departing from the scope of the present invention.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a radiation image information reading apparatus for carrying out a method for adjusting a galvanometer mirror according to the present invention, and FIG. 2 is a diagram showing the radiation image information reading apparatus and the galvanometer mirror driving section shown in FIGS. 1 and 3. 3 is a detailed block diagram of a galvanometer mirror drive unit in the radiation image information reading apparatus shown in FIG. 1. 10 …… Radiation image information reading device 12 …… Laser scanning unit, 14 …… Image reading unit 16 …… Synchronization signal generation unit 17 …… Galvanometer mirror 18 …… Driving unit, 20 …… Signal processing unit 22 …… Laser light source 24 …… Beam expander 26 …… Scan lens, 28 …… Half mirror 30 …… Light guide 32 …… Photomultiplier 34 …… A / D converter, 36 …… Grid 36a …… Transmissive section, 36b …… Non-transmissive part 36c …… Wide transmissive part, 38 …… Optical guide 40a, 40b …… Optical sensor, 42 …… Waveform shaping circuit 44 …… Synchronizing signal generation circuit, 54 …… Speed detection part 56,58 …… D / A converter 60 …… Control circuit, 62 …… Integrator L, La, Lb …… Light beam S …… Storable phosphor sheet _GG …… Grid clock G _R …… Reference grid signal T _R , T _S …… Synchronous clock

Claims (2)

[Claims] 1. An object to be scanned is main-scanned by a light beam deflected in a one-dimensional direction by a galvanometer mirror, and the object is relatively moved in a direction substantially orthogonal to the main-scanning direction. When two-dimensionally scanning and recording or reading character information, image information, etc., a synchronizing light beam scans a grid on which a plurality of bright and dark patterns are formed in the main scanning direction, and the light beam passing through the grid is scanned. A method of adjusting a galvanometer mirror used in a light beam scanning device for photoelectrically detecting to obtain a synchronization signal, comprising forming N (N is a natural number of 2 or more) phase modulators of a light-dark pattern on the grid, When the grid having the N phase modulators is scanned by the synchronization light beam, the number of detected phase modulators per scan becomes M (M is a natural number satisfying M ≦ N). Method of adjusting the galvanometer mirror and adjusting the offset Urn galvanometer mirror. 2. The method according to claim 1, wherein the number N of phase modulation portions of the light-dark pattern is 3 or more, and the number of modulation detections after the adjustment in the first aspect is M.
When the offset value x _m-1 of the sawtooth signal that becomes -1 is measured, and then the offset value x _m-2 of the sawtooth signal that becomes M-2 in the number of modulation detections is measured, the saw applied to the galvanometer mirror The offset value x _m of the wave signal is x _m = 3 /
How to adjust the galvanometer mirror with the value of 2x _m-1 −1 / 2x _m-2 as the middle value.