JPH01144011A - Method for adjusting galvanometer mirror - Google Patents

Abstract

PURPOSE:To automatically adjust the offset of an initial position occurring in a galvanometer mirror by adjusting the mirror in such a manner that the number of pulses applied on a modulating grid part attains a preset number. CONSTITUTION:The offset of the galvanometer mirror 17 is so adjusted that the detection number of the phase modulating parts per scanning attains M- pieces (M is a natural number satisfying M<=N) at the time of forming N-pieces (N is >=2 natural number) of the phase modulating parts of bright and dark patterns on the grid 36 and scanning the grid 36 having N-pieces of the phase modulating part by light beams La, Lb for synchronization. The reading start position or recording start position of the object to be scanned is exactly obtd. by using the galvanometer mirror 17 adjusted in such a manner. The always precise reconstructed image is thus obtd.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a method for adjusting a galvanometer mirror, and more specifically, scanning an object to be scanned with a light beam deflected by a galvanometer mirror to read an image, etc. Alternatively, the present invention relates to a method for adjusting the offset of a galvanometer mirror incorporated in a light beam scanning device that performs recording.

[Background of the Invention] Conventionally, an object to be scanned is main-scanned by a light beam deflected in one dimension by a galvanometer mirror, which is an optical deflector, and the object to be scanned is scanned in a direction substantially orthogonal to the main scanning direction (sub-scanning direction). 2. Description of the Related Art Light beam scanning devices configured to two-dimensionally scan a scanned object by moving relatively in a scanning direction) are widely used as various recording devices and reading devices.

For example, a stimulable phosphor sheet on which radiographic image information has been accumulated and recorded is scanned with excitation light such as a laser beam to generate stimulated luminescent light having radiographic image information, and this stimulated luminescent light is transferred to a photomultiplier or the like. A good example is a radiation image information reading device configured to obtain an image signal by photoelectrically detecting it using a detection means. Note that a stimulable phosphor is a material that, when irradiated with radiation (X-rays, α-rays, β-rays, T-rays, electron beams, ultraviolet rays, etc.), stores a portion of this radiation energy and later emits visible light, etc. It refers to a phosphor that generates stimulated luminescence according to the energy accumulated by irradiation with excitation light, and a stimulable phosphor sheet refers to a sheet having a layer made of the stimulable phosphor.

Incidentally, in the radiation image information reading device, it is desirable that the reading start position and main scanning speed (reading speed) for each scanning line of the light beam that main scans the stimulable phosphor sheet be constant.

That is, if the reading start position (hereinafter simply referred to as the reading start position) for each scanning line is constant, image information from a predetermined position of the stimulable phosphor sheet can always be accurately obtained;
On the other hand, if the main scanning speed is constant, the sampling time per pixel of image information becomes equal, and the image information can be read evenly. The reading start position and main scanning speed change depending on the position offset and deflection angular velocity of the galvanometer mirror that deflects the light beam, respectively.

However, since the galvanometer mirror has many mechanically movable parts, its position offset and deflection range may be mechanically slightly shifted due to fluctuations in environmental conditions such as ambient temperature. In this case, even a slight mechanical shift, such as a slight shift in mirror alignment, will significantly change the reading start position on the stimulable phosphor sheet and the scanning speed of the light beam.

Therefore, in order to eliminate fluctuations in the reading start position and scanning speed due to environmental conditions, the following adjustment work is performed. That is, first, a scanning light beam is divided by a half mirror or the like, and the divided synchronization light beam is formed into an optical grating (hereinafter referred to as "optical grating") having a light and dark pattern in which light transmitting parts and non-transmitting parts are arranged alternately. , grid) and scan it to generate pulsed light.

Next, a synchronization signal is generated based on the grid signal obtained from this pulsed light, and this synchronization signal is used to determine the DC offset and deflection angular velocity of the sawtooth wave electric signal (hereinafter referred to as the sawtooth wave signal) that drives the galvanometer mirror. The corresponding slope (amount of change in current or voltage per unit time, hereinafter simply referred to as scanning speed) is varied to adjust the position offset and deflection angular velocity of the galvanometer mirror.

When adjusting the DC offset and deflection angular velocity in this manner, a reference signal is required to determine the reading start position of the stimulable phosphor sheet.

Conventionally, as a measure to obtain this reference signal, a non-transparent part disposed at the end of the grid is formed wide, and the first pulsed light generated after scanning this wide non-transparent part with a synchronization light beam is used. As a reference signal, a photodetection sensor is arranged near the tip of the scanning area of the synchronizing light beam corresponding to the reading start position of the stimulable phosphor sheet, and the pulsed light obtained from this photodetection sensor is used as a reference. Measures such as signaling are being adopted.

However, if such a strategy is chosen,
If the initial offset of the galvanometer mirror described above is considerably large, and therefore the scanning area of the synchronizing light beam deviates from the wide non-transparent part on the grid or the photodetection sensor disposed corresponding to the reading start position lid. occurs.

In this case, there is a disadvantage that automatic adjustment of the galvanometer mirror is no longer possible because a reference signal for adjusting the DC offset and scanning speed is no longer generated.

[Object of the Invention] The present invention has been made to overcome the above-mentioned disadvantages, and includes forming a plurality of phase modulation portions of light and dark patterns on the grid, and scanning the grid with a synchronizing light beam. 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 part becomes a preset predetermined number of pulses among the 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-mentioned object, the present invention mainly scans an object to be scanned with a light beam deflected in a one-dimensional direction by a galvanometer mirror, and also main-scans the object to be scanned. When recording or reading character information, image information, etc. by scanning a scanned object two-dimensionally by moving relatively in a direction substantially perpendicular to the direction, multiple bright and dark patterns are created in the main scanning direction by a synchronizing light beam. A method for adjusting a galvanometer mirror employed in a light beam scanning device that scans a grid formed with a light beam and photoelectrically detects a light beam passing through the grid to obtain a synchronization signal, the method comprising: When forming N phase modulation sections (N is a natural number of 2 or more) and scanning a grid having the N phase modulation sections with a synchronization light beam, the number of phase modulation sections detected per one scan is M. (M is a natural number satisfying M≦N).

[Embodiments] Next, preferred embodiments of an apparatus for carrying out the galvanometer mirror adjustment method according to the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 1, reference numeral 10 indicates a schematic configuration of a radiation image information reading device incorporating a device for implementing the galvanometer mirror adjustment method according to the present invention. The radiation image information reading device 1O performs laser scanning in which a scanned object on which radiation image information is recorded, for example, a stimulable phosphor sheet S that is conveyed in the sub-scanning direction (in the direction of the arrow) is scanned with a light beam La. 12, and an image reading section 1 that photoelectrically converts light having image information obtained by scanning with the light beam La.
4, a synchronization signal generator 16 that detects the scanning position of the light beam Lb and generates a synchronization signal, and a galvanometer mirror 1
7, and a signal processing section 20 that converts the signal from the image reading section 14 into digital image information based on a synchronization signal and stores it in an image memory (not shown). configured.

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

The light beam L reflected and deflected by the rocking operation of the galvanometer mirror 17 passes through a scanning lens 26 such as an fθ lens arranged in the optical path, and then is arranged on the optical path extending in the main scanning direction. The light is incident on the half mirror 28. This half mirror 28 reflects an amount of light beam necessary for scanning out of the incident light beam L as a scanning light beam La, and transmits the remaining light beam as a synchronization light beam Lb. 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 (arrow C direction). .

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

On the other hand, the synchronization signal generating section 16 has a light and dark pattern 37 consisting of a transmitting section 36a that transmits the light beam Lb that has passed through the half mirror 28, a wide transmitting section 36C described later, and a non-transmissive section 36b that reflects the light beam Lb. grids 36 arranged alternately along the scanning direction of the light beam Lb (direction of arrow F), cylindrical light guides 38 arranged along the rear of the grids 36, and the light guides 38. A waveform shaping circuit 42 that shapes the waveforms of optical sensors 40a, 40b provided at both ends of the grid 36 to detect the light beam Lb transmitted from the grid 36, and a reference grid signal G output from the optical sensors 4Qa, 40b; The synchronization signal generation circuit 44 generates a synchronization clock TR based on the grid clock Gc, which is the output signal after waveform shaping from the circuit 42.

In this case, as described above, it is necessary for the scanning light beam La to start actual reading (hereinafter referred to as effective scanning) from a predetermined position in the main scanning direction on the stimulable phosphor sheet S, and each It is necessary to control the starting point of effective scanning to the same position for each scanning line. Therefore, in this apparatus, the light and dark pattern 37 of the grid 36 has a characteristic configuration shown in FIG. 2a to perform starting point control. That is, the light and dark pattern 37 of the grid 36 is basically formed by alternating at a constant pitch a standard-width transmissive part 36a that transmits the synchronizing light beam Lb and a non-transmissive part 36b that blocks the synchronizing light beam Lb. However, the configuration is such that wide transmission portions 36c are formed at predetermined intervals with a pitch different from those of these portions, that is, phase-modulated wide transmission portions 36c.

In this embodiment, the number N of the wide transparent portions 36c is four. The number N of the wide transparent parts 36C is
As will be described later, at least two are required to carry out the present invention, and it is more preferable to form three or more for the reasons described later.

On the other hand, the synchronization clock T from the synchronization signal generation circuit 44
R is introduced into the synchronization signal input terminal of the A/D converter 34. In this case, the synchronization signal generation circuit 44 is configured as a frequency synthesizer, for example, and generates a synchronization clock T corresponding to a so-called pixel clock, which is obtained by multiplying the grid clock G by a predetermined multiple.

FIG. 3 is a block diagram showing a schematic configuration of the drive section 18. The drive unit 18 uses the synchronization clock T generated by the synchronization signal generation circuit 44 to generate a phase-modulated pulse P related to the wide transmission part 36C included in the grid clock G.
1 and outputs a corresponding pulse G (hereinafter referred to as a modulation detection pulse) to the modulation unit, and a modulation detection unit 50 that detects a swinging operation offset of the galvanometer mirror 17 based on the modulation detection pulse GH. Offset detection section 52
, a speed detection unit 54 that detects the scanning speed of the galvanometer mirror 17 based on the time for generating a predetermined number of pulses of the grid clock Gc, and the offset detection unit 52
and predetermined offset data D from the output signal of the speed detection section 54. PF and predetermined speed data I) sp to the D/A converters 56 and 58, respectively;
an integrator 62 that is a sawtooth wave generator that integrates the output signal of the converter 58 to generate a sawtooth wave signal; and a summing amplifier 69 that adds the output signal of the integrator 62 and the output signal of the D/A converter 56. It includes a galvanometer driver 70 that converts the output signal of the summing amplifier 69 into a predetermined drive current for driving the galvanometer mirror 17.

A radiation image information reading device incorporating a device for carrying out the galvanometer mirror adjustment method according to the present invention is basically constructed as described above, and its operation and effects will be explained next.

In this device, as described above, the galvanometer mirror 1
7 (see FIG. 1) and the scanning speed V from the reading start position E1 to the reading end position E2 are determined. In this case, the reading start position E1 and scanning speed V can be determined by adjusting the repetitive sawtooth signal W (see FIG. 2) supplied to the galvanometer mirror 17. That is, considering that the amplitude WA of the sawtooth wave signal W corresponds to the entire scanning interval Ec (see FIG. 1), the reading start position E can be determined by adjusting the DC offset (Wa) of the sawtooth wave signal W.

can be determined, and the slope of the sawtooth signal W, that is, the scanning period T. It will be easily understood that the predetermined reading speed V can be determined by adjusting the amplitude change WA within (hereinafter simply referred to as amplitude WA).

Therefore, first, in the control section 60,
It is assumed that initial values of Wa and amplitude W are appropriately set, and a sawtooth wave signal W according to the set values is supplied from the galvanometer driver 70 to the galvanometer mirror 17.

Referring again to FIG. 1, the light beam L emitted from the laser light source 22 is supplied with the sawtooth signal W, but is deflected in the direction of the arrow B by the luvanometer mirror 17. Among the light beams L thus deflected, the light beam Lb that has passed through the scanning lens 26 and the half mirror 28 scans the grid 36 in the direction of the arrow F. In this case, the light beam Lb that has passed through the standard width transmission section 36a and the wide transmission section 36c of the grid 36 enters the light guide 38, and the light beam Lb is diffused on the opposite side of the light guide 38 to the incident side of the light beam Lb. The light beam Lb, which is diffused in various different directions by a band (not shown) and is repeatedly totally reflected within the light guide 38, reaches the optical sensors 40a and 40b, where it is photoelectrically converted, and a wide light beam related to the wide transmission section 36C. Reference grid signal Ga containing pulses
is generated. Since this reference grid signal GR is an analog signal, in order to use it as a timing signal, a waveform shaping circuit 42 that includes a comparator and performs a comparison operation generates a grid clock GG (see FIG. 2C) with steep rising and falling portions of the waveform. ) is converted into the drive unit 18
and is introduced into the synchronization signal generation circuit 44.

Next, the galvanometer mirror 17 is adjusted. In addition, when adjusting the galvanometer mirror 17,
Offset adjustment and amplitude adjustment related to scanning speed are not independent of each other; adjusting one will cause the other to fluctuate by a predetermined amount, so offset adjustment and amplitude adjustment can be done by repeating the adjustment several times. Adjust so that it falls within the specified setting range.

Therefore, first, offset adjustment will be explained. In this case, as described above, the grid clock Gc from the waveform shaping circuit 42 is introduced into the modulation detection section 50, and the grid clock Gc is introduced from the synchronization signal generation circuit 44.
Synchronous clock 'ri' which is multiplied by a predetermined value (see Figure 2 C)
will be introduced. As can be understood from FIG. 2C, the grid clock G0 includes a standard pulse P corresponding to the transparent portion 36a and the wide transparent portion 36C of the grid 36, and a wide pulse P1. Therefore, the configuration of the modulation detection unit 50 that detects only the wide pulse P from the grid clock G is such that the number of clock pulses PC of the synchronized clock TII generated during the generation period of the standard pulse P and the wide pulse P is a predetermined number. Only the pulses with the above number are called wide pulses P.

It may consist of a counter and a timer that are selected at the same time. The modulation detection pulse G)I detected by the modulation detection section 50 in this manner is shown in FIG. 2e.

In FIG. 2e, all four pulses PH present in the modulation detection pulse GH are depicted, but now, for example,
Assume that the scanning range of the light beam Lb on the grid 36 is shifted to the right as shown by the deflection angle θ1 in FIG. 3 due to the offset shift of the galvanometer mirror 17, and only the fourth pulse PII4 can be detected. A method for adjusting the offset of the galvanometer mirror 17 in this case will be described.

First, when scanning the entire main scan length, the modulation detection pulse G□
Since it is known in advance that the total number N of pulses PH related to 4 is 4, the offset value is gradually reduced and the number of pulses PH is counted each time, and the offset is reduced until the number of pulses PH becomes 4. Next, a specified number M corresponding to a certain scanning mode (this embodiment Then, conversely, gradually increase the offset so that pulses P and I are detected by the number of pulses P and I, where M is 4 or less.
For example, if the specified number M is determined to be M=3 and the offset value is increased until the number of pulses PR becomes the specified number M=3, then the number of pulses PH is determined for the specified number M=3. The offset value is further increased so that M-1=2, and the offset value X□1 immediately after the number of pulses PR becomes M-1=2 is determined. This offset value xm-1 is D/
Setting value D07 for A converter 56. It is.

Next, the offset is further increased so that the number of pulses PH becomes M
Find the offset value X5-2 such that -2=1. From the above results, the offset value xm to be set for the galvanometer mirror 17 is X, = 3/2 X5-1-1/2
Let X be -2 (see the number line shown in Figure 2f). As can be easily understood from FIG. 2f, the offset value xm is set to a value corresponding to approximately the center of the adjacent pulses P, to avoid erroneous detection of the pulses P and l.

By the way, when the specified number M is 2 or more, the offset value may be adjusted by the above procedure, but when the specified number M is 1, the above method cannot be adopted, so the following method is used. That is, when the prescribed number M is set to M=1, first, the pulses P, ! Find the offset value X2 where 2 becomes 2, and then find the offset value X where the number of pulses PI becomes 1 by increasing the offset.As a result, the offset value It is easily understood that X3 should be used.

Note that the offset adjustment method described above is based on the light beam L.
This is an adjustment method when the scanning range of b 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 modulation detection pulse GH
What is necessary is to change the offset so that it is adjusted in the direction of increasing it in the process until finding the total number of pulses Po related to .

After adjusting the offset in this way, next, scan speed V
Adjust. The scanning speed V is adjusted, for example, by adjusting the D/A converter 58 so that a predetermined number of pulses P of the grid clock Gc are generated for a predetermined time after the first pulse PHI of the modulation detection pulse GH is generated. What is necessary is to adjust the amplitude value [)sp that should be set to . When the amplitude is adjusted in this way, the offset also changes, so the offset adjustment and the speed adjustment described above are repeated until both are within a predetermined set value.

After the sawtooth signal W is appropriately adjusted as described above, the stimulable phosphor sheet S is set and image reading is started. In this case, the surface of the stimulable phosphor sheet S is irradiated with a 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 It is extracted as emitted light.

This stimulated luminescent light enters a photomultiplier 32 via a light guide 30 disposed in the main scanning direction of the stimulable phosphor sheet S, and is converted into an electrical signal. Then, the electrical signal from the photomultiplier 32 is applied to the signal input terminal of the A/D converter 34 via the log amplifier 33, and this signal is A/D converted for each pulse of the synchronized clock T. . The image signal obtained in this way is subjected to signal processing such as gradation processing and frequency processing by a signal processor (not shown), and then is displayed on an image recording carrier such as film or on a display device such as CRT. reproduced as a statue.

Although the above embodiment has been described with respect to a device that performs reading using a light beam scanning device, it is of course applicable to a device that records an image on an image recording carrier such as a film by scanning a light beam.

[Effects of the Invention] As described above, according to the present invention, by scanning a grid in which a plurality of phase modulation portions are formed with a synchronizing light beam, the pulse applied to the modulation grid portion among the obtained pulses is The number is adjusted to a predetermined number. Therefore, the position offset of the galvanometer mirror can be adjusted accurately. Therefore, by using the galvanometer mirror adjusted in this way, the reading start position or recording start position of the object to be scanned can be accurately obtained, and as a result,
Accurate reproduced images can always be obtained.

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to these embodiments.
Of course, various improvements and changes in design are possible without departing from the gist of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a radiation image information reading device implementing the galvanometer mirror adjustment method according to the present invention, and FIG. 2 is a schematic diagram of the radiation image information reading device and galvanometer mirror drive section shown in FIGS. 1 and 3. 3 is a detailed block diagram of the galvanometer mirror drive section in the radiation image information reading device shown in FIG. 1. FIG. 10... Radiation image information reading device 12... Laser scanning section I4... Image reading section 16... Synchronization signal generation section 17... Galvanometer mirror 18... Drive section 20... Signal processing section 22... Laser light source 24... Beam expander 26... Scanning lens 28... Half mirror 30... Light guide 32... Photo multiplier 34... A/D converter 36...・Grid 3
6a...Transparent part 36b...Non-transparent part 3
6c...Wide transparent part 38...Light guide 40
a, 40b... Optical sensor 42... Waveform shaping circuit 44... Synchronization signal generation circuit 54... Speed detection section 56.58... D/A converter 60... Control circuit 62... Integrator,
La5Lb--Light beam S...Stormable phosphor sheet G,...Grid clock G,...Reference grid signal TR, Ts...Synchronization clock

Claims (2)

[Claims] (1) A light beam deflected in a one-dimensional direction by a galvanometer mirror is used to main scan an object to be scanned, and the object to be scanned is moved relatively in a direction substantially perpendicular to the main scanning direction to move the object to be scanned in two directions. When recording or reading character information, image information, etc. by scanning dimensionally, a synchronizing light beam scans a grid in which multiple bright and dark patterns are formed in the main scanning direction, and the light beam that passes through the grid is used as a photoelectric sensor. A method for adjusting a galvanometer mirror employed in a light beam scanning device that obtains a synchronization signal by detecting When scanning a grid having phase modulation sections with a synchronization light beam, the galvanometer mirror is offset so that the number of phase modulation sections detected per one scan is M (M is a natural number satisfying M≦N). A method for adjusting a galvanometer mirror. (2) In the method according to claim 1, the number N of phase modulation parts of the bright and dark pattern is 3 or more, and the number of detected modulations is M-1 after the adjustment in claim 1. When the offset value x_m_-_1 of the sawtooth wave signal is measured, and then the offset value x_m_-_2 of the sawtooth wave signal where the number of modulation detections is M-2 is measured, the offset value x of the sawtooth wave signal applied to the galvanometer mirror is
_m is x_m=3/2x_m_-_1-1/2x_m_
- A method of adjusting a galvanometer mirror using a value of _2 as a medium value.