JPH01183642A - Control method for scan timing of light beam - Google Patents

Abstract

PURPOSE:To always obtain minute information at the time of regular reading by obtaining exact pre-reading information by adjusting a scan timing on a phosphor sheet, based on a grid signal obtained by a light beam at the time of regular reading before the time of pre-reading. CONSTITUTION:First of all, a concave lens 30 is separated to a full line position in the C direction from an optical path, and in such a state, a galvanomirror 18 is adjusted. The adjustment determines a read start position E1 of a cumulative phosphor sheet S, and a constant speed in a read section E4. In such a state, a reference grid signal obtained from a light guide 44 is supplied to a synchronization generating circuit 48 and a VCO in the circuit 48 generates a normal synchronizing signal. Subsequently, the lens 30 is inserted into the optical path and pre-reading is executed. Next, to the surface of the sheet S, a light beam La of low energy is radiated, and image information which is recorded in the sheet S is fetched as an accelerated luminous light, converted to an electric signal by a photomultiplier 36 through a light guide 38, led into a control circuit through a log amplifier 39 and an A/D converter 40, and an image reading condition and an image processing condition of gradation processing/frequency processing, etc. are set.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for controlling the scanning timing of a light beam employed in a radiation image information reading device. Reading conditions for reading visible image reproduction from stimulated luminescence light obtained by irradiating a phosphor sheet with a light beam serving as low-energy excitation light prior to reading for visible image reproduction, and/or
Or used in a radiation image information reading device configured to set image processing conditions, then irradiate the sheet with a high-energy light beam, and read image information based on the reading conditions and/or image processing conditions. The present invention relates to a scanning timing control method for a light beam.

[Background of the Invention] Conventionally, a stimulable phosphor sheet on which radiation image information is recorded is mainly scanned by a light beam serving as excitation light that is deflected by a light deflecting means such as a galvanometer mirror, a rotating polygon mirror, or a hologram scanner. , sub-scanning is performed by relatively moving this stimulable phosphor sheet in a direction substantially perpendicular to the main scanning direction, the stimulable phosphor sheet is two-dimensionally scanned, and the stimulable phosphor sheet is scanned in a two-dimensional manner. 2. Description of the Related Art A radiation image information reading device is known that generates emitted light, photoelectrically detects the light carrying radiation image information, and reads the image information as an electrical signal. Note that a stimulable phosphor is a material that, when irradiated with radiation (X-rays, α-rays, β-rays, γ-rays, electron beams, ultraviolet rays, etc.), stores a portion of this radiation energy and later releases 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.

By the way, in such a radiation image information reading device, a radiation image information reading operation (hereinafter referred to as "book reading") is performed to scan a stimulable phosphor sheet with excitation light and reproduce a visible image for observation and interpretation. Prior to this, in order to set the reading conditions and/or image processing conditions for the main reading,
A pre-reading operation is performed in which the sheet is irradiated with excitation light having a beam diameter larger than that in the case of actual reading to read an outline of the radiation image information. In addition, during this pre-reading, it is sufficient to scan roughly in order to read the outline of the radiation image information recorded on the stimulable phosphor sheet, and in order to suppress the loss of image information during pre-reading to the necessary minimum, the excitation light is The beam diameter of the light beam is expanded by, for example, inserting a pre-reading optical system such as a concave lens into the optical path of the light beam, and the excitation energy of the light beam is reduced.

On the other hand, in the radiation image information reading device described above, when reading an image by scanning a light beam, a synchronization signal that synchronizes with the scanning of the light beam is required. That is, when reading an image using a light beam scanning device, image information is read photoelectrically based on a synchronization signal.

To obtain such a synchronization signal, a scanning light beam is split by a half mirror, etc., and the split light beam is guided to an optical grating (hereinafter referred to as grid) having a light and dark pattern for scanning, thereby generating pulsed light. and then PL based on the grid signal obtained from this pulsed light.
A known method is to generate a synchronization signal by multiplying the grid signal by a predetermined value using an L (Phase Locked Loop) circuit.

However, when the diameter of the light beam is expanded by inserting a pre-reading optical system such as the concave lens during pre-reading,
Since the amplitude of the pulsed light obtained by scanning the grid becomes extremely small, the synchronization signal becomes inaccurate, and in the end, the image reading conditions for actual reading cannot be determined based on the pre-read information read using such a synchronization signal. And/or there is a drawback that image processing conditions cannot be set accurately.

[Object of the Invention] The present invention has been made to overcome the above-mentioned disadvantages, and includes the following steps when determining a reading scan start position on a stimulable phosphor sheet during pre-reading by a radiation image information reading device.
Before pre-reading, which expands the beam diameter of the light beam via a pre-reading optical system and reads the outline of radiation image information, a synchronization signal obtained with the beam diameter in the same state as the main reading state without expanding the beam diameter is used. By storing the generated voltage, that is, the input voltage of the voltage controlled oscillator constituting the PLL circuit, the main reading is performed by supplying the stored voltage to the input voltage of the voltage controlled oscillator during pre-reading. To provide a light beam scanning timing control method that generates a time synchronization signal and an inter-way synchronization signal, thereby making it possible to accurately set image reading conditions and/or image processing conditions during main reading. The purpose is to

[Means for Achieving the Object] In order to achieve the above object, the present invention scans a stimulable phosphor sheet on which radiographic image information is recorded with a light beam as excitation light, while scanning a stimulable phosphor sheet with a synchronizing light beam. A radiation image information reading device that generates a synchronization signal from a signal obtained by scanning a grid consisting of alternating light transmission parts and reflection parts with a beam, and photoelectrically reads the image information based on the synchronization signal. A method for controlling the scanning timing of a light beam employed, wherein an optical system is inserted into the optical path of the light beam to widen the beam diameter of the light beam, and the light beam irradiated through the optical system is used to control the stimulable phosphor. Before the pre-reading step of scanning the sheet and reading the outline of the radiation image information in order to set the image reading conditions and/or image processing conditions for visible image reproduction, the pre-reading optical system is preliminarily not used. The present invention is characterized in that the scanning timing of the light beam is adjusted in advance, and then a pre-reading step is performed according to the adjusted scanning timing.

[Embodiments] Next, preferred embodiments of an apparatus for carrying out the light beam scanning timing control method according to the present invention will be listed.
A detailed description will be given below 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 light beam scanning timing control method according to the present invention. The radiation image information reading device 10 performs laser scanning in which an object to be scanned on which radiation image information is recorded, for example, a stimulable phosphor sheet S transported 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 18.
It basically consists of a galvanometer mirror driving section 20 that drives the image reading section 14, and a signal processing section 22 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). .

Therefore, after the light beam L emitted from the laser light source 24 of the laser scanning section 12 passes through the beam expander 26 and is formed into a beam diameter of a desired thickness, the light beam L is oscillated in the direction of the arrow B to emit light. The beam L is incident on the galvanometer mirror 18, which reflects the beam L, and is reflected and deflected. In addition, in the optical path of the light beam L between the beam expander 26 and the galvanometer mirror 18, a concave lens 30 constituting a look-ahead optical system is located along the arrow C in order to change the beam diameter of the light beam L.
It is arranged so that it can be removed in any direction.

The light beam L reflected and deflected by the vibration operation of the galvanometer mirror 18 passes through a scanning lens 32 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 enters the half mirror 34. This half mirror 34 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 34 is focused on the stimulable phosphor notebook S disposed on the optical path, and scans the stimulable phosphor sheet S in the main scanning direction (arrow direction).

The image reading section I4 includes a transparent light guide 3 that guides stimulated luminescence light generated from the stimulable phosphor sheet S excited by the light beam La to the light receiving surface of the photomultiplier 36.
Contains 8. In this case, the receiving surface of the stimulated luminescent light in the light guide 38 is arranged close to the stimulable phosphor sheet S along its main scanning direction. A high voltage set based on the read-ahead information is applied to a high voltage input voltage (not shown) of the photomultiplier 36, and the electrical signal after photoelectric conversion of the photomultiplier 36 is stored in the signal processing section 22 and stored in a log. A/D converter 40 via amplifier 39
is introduced into the signal input voltage.

On the other hand, the synchronization signal generating section 16 has a transmitting section 42a that transmits the light beam Lb that has passed through the half mirror 34 and a reflecting section 42b that reflects the light beam Lb along the scanning direction (arrow F direction) of the light beam Lb. A cylindrical light guide 44 is arranged along the rear of the grid 42, and a light beam Lb transmitted from the grid 42 is provided at both ends of the light guide 44. , a waveform shaping circuit 47 that shapes the reference grid signal GR output from the light detection sensors 46a and 46b, and a grid signal G that is an output signal from the waveform shaping circuit 47. and a synchronization signal generation circuit 48 that generates a synchronization signal T based on the synchronization signal T. The synchronization signal T from the synchronization signal generation circuit 48 is logically ANDed by the gate circuit 49 with the output signal of the drive unit 20 that drives the galvanometer mirror 18, and then outputted to the A/D converter 40 as the synchronization signal T. is introduced into the synchronization signal input voltage.

FIG. 2 is a block diagram showing a schematic configuration of the synchronization signal generation circuit 48 shown in FIG. 1. The synchronizing signal generating circuit 48 is basically configured as a PLL circuit. In Figure 2,
The waveform shaping circuit 4 is connected to one input voltage of the phase comparator 50.
A grid signal G, from 7 is introduced, and the phase comparator 50
The output signal is introduced into the input voltage of the voltage controlled oscillator 54 via a low-pass filter 52 and a switch 53 consisting of contacts 53a to 53C. The output signal of the voltage controlled oscillator 54 is output as a synchronizing signal T, and is also introduced into the other input voltage of the phase comparator 50 via a frequency divider 56. The switch 53 has a configuration of one circuit and two contacts, and the common contact 53a1 of the switch 53, that is, the signal introduced into the input voltage of the voltage controlled oscillator 54 is A.
The signal is introduced via the /D converter 58 into a control circuit 60 including a CPU (not shown) and stored therein. The control circuit 60
The output signal is introduced into the contact 53b of the switch 53 via the D/A converter 62.

FIG. 3 is a block diagram showing a schematic configuration of the drive section 20. As shown in FIG. The drive unit 20 includes a timer 70 that measures the time between predetermined pulses in the grid signal Gc, a control circuit 76 that includes a counter 72 that counts pulses, a microprocessor unit 74 (hereinafter referred to as MPU), and the like. A sawtooth wave generator 78 generates a sawtooth wave signal W for driving the galvanometer mirror 18 in response to a control signal from the galvanometer mirror 18 .

A radiation image information reading device incorporating a device for implementing the light beam scanning timing control method according to the present invention is basically configured as described above, and its operation and effects will be explained next.

FIG. 4 is a flowchart showing the operating procedure of the light beam scanning timing control method according to the embodiment of the present invention, and a diagram illustrating the display of the operating state of the switch 53 shown in FIG. 2. Therefore, the embodiment will be explained based on this flowchart and operation state display.

First, in the first step, the concave lens 30 is removed from the optical path of the light beam L to the position drawn by the solid line in the direction of arrow C (see FIG. 1), and the common contact 53a of the switch 53 in the synchronizing signal generating circuit 48 is removed. and contact 53C (STPI).

Next, in the second step, the galvanometer mirror 18 is adjusted with the concave lens 30 removed, that is, with the beam diameter of the light beam L not expanded.
The scan timing of the light beam is determined (STP2). This adjustment of the galvanometer mirror 18 involves determining the reading start position fE+ (see Figure 1) of the stimulable phosphor sheet S, and adjusting the scanning speed from the reading start position E1 to the reading end position E2 to a predetermined value. The goal is to maintain a constant speed. In this case, since the reading operation of the stimulable phosphor sheet S is not performed, it is not necessary to provide the stimulable phosphor sheet S during this adjustment. The reading start position E1 and scanning speed can be determined by adjusting the repetitive sawtooth signal W (see FIG. 5C) supplied to the galvanometer mirror 18. That is, the amplitude WA of the sawtooth signal W is equal to the entire scanning section E3.
(See Figure 1), the reading start position E1 can be determined by adjusting the DC level W of the sawtooth signal W, and the predetermined scanning speed can be determined by adjusting the slope of the sawtooth signal W. It is easy to understand that it can be determined.

Referring again to FIG. 1, the light beam L emitted from the laser light source 24 is deflected in the direction of arrow B by the galvanometer mirror 18. Among the light beams L thus deflected, the light beam Lb that passes through the scanning lens 32) and the half mirror 34 scans the grid 42 in the direction of the arrow F. In this case, the light beam Lb that has passed through the transmission part 42a of the grid 42 is incident on the light guide 44, and various effects are caused by a diffusion band (not shown) formed on the side of the light guide 44 opposite to the incident side of the light beam Lb. light guide 44.
The light beam Lb that has been repeatedly totally reflected inside is detected by the light detection sensor 4
6a and 46b, the signal is photoelectrically converted, and the reference grid signal GR shown in FIG. 5 is generated and introduced into the waveform shaping circuit 47. In addition, in FIG. 5, the reference grid signal G
The number of pulses of R is depicted as less than the actual number of pulses obtained from grid 42 to facilitate understanding of the invention.

In order to use this reference grid signal GR as a timing signal, it is converted into a grid signal Gc (see FIG. 5C) whose waveform has steep rising and falling parts by a waveform shaping circuit 47 that includes a comparator and performs a comparison operation. It is introduced into the control circuit 76 and the synchronization signal generation circuit 48 in the drive section 20 .

Therefore, the sawtooth wave signal W for driving the galvanometer mirror 18 is adjusted in the control circuit 76 (see FIG. 3) based on the grid signal Gc.

In this case, the slope of the sawtooth signal W is determined at a predetermined pulse interval using a timer 70 and a counter 72, for example, at a pulse NA.
The interval between pulse NB and pulse NB (see Fig. 5C) is set as a constant time T.
. It can be adjusted by matching the DC level WB
is a predetermined pulse, for example, a pulse Nc, after a predetermined time T1 has elapsed from the generation of the scan start clock CS (see FIG. 5C).
You just need to adjust it so that it occurs. As described above, the main scanning speed and reading start position E1 are determined. In this case, the scanning section E is a pulse N. From pulse N.

A gate signal G (see FIG. 5C) is generated from the control circuit 76 corresponding to this scanning period E, and the gate signal G is applied to one input voltage of the gate circuit 49. be introduced. In addition, in the H arrow view of the stimulable phosphor sheet S arranged for ease of understanding in FIG. 5a (see FIG. 1 for the direction of H), the scanning direction is the arrow direction. In the flowchart shown in FIG. 4, the adjustment of the galvanometer mirror 18 to determine the scanning timing of the light beam, which is the second step, is completed.

Next, in the third step, the human input signal of the voltage controlled oscillator 54 in the synchronizing signal generating circuit 48 is stored in a memory (not shown) of the control circuit 60 (SrF2). In this case, as described above, the grid signal G is generated by the synchronization signal generation circuit 48.
The synchronizing signal TR, which is the output signal of the synchronizing signal generating circuit 48, is output by multiplying the grid signal G6 by a predetermined value (see FIG. 5C). Here, since the voltage controlled oscillator 54 constituting the synchronizing signal generating circuit 48 generates a predetermined multiplied synchronizing signal TR based on the voltage input thereto, this input voltage is proportional to the output frequency. Therefore, the input voltage of the voltage controlled oscillator 54 when this normal reference grid signal GR (see FIG. 5) is output, that is,
The input voltage value when the concave lens 30 is removed from the optical path is stored in the memory in the control circuit 60 via the A/D converter 58 (
(not shown).

Next, in the fourth step, pre-reading is performed (SrF4).

In this case, in order to set the reading conditions and/or image processing conditions during the main reading of the stimulable phosphor sheet S, the stimulable phosphor sheet S is irradiated with excitation light having a larger beam diameter than in the main reading. All you have to do is read the outline of the radiation image information. In other words, at the time of look-ahead, the light beam L
In order to enlarge the beam diameter of a, the concave lens 30 is inserted into the optical path of the light beam L in the direction opposite to the direction of arrow C and read. In this case, the reference grid signal GR generated by the photodetectors 46a and 46b becomes a small amplitude signal as shown in FIG. 5g, and it is difficult to generate the grid signal CG from this small amplitude signal. That will happen. Therefore, at the time of pre-reading, the switch 53 disposed at the input end of the voltage controlled oscillator 54 in the synchronizing signal generating circuit 48 is switched to the contact 53b side, and in the third step, the control circuit 6
The input voltage of the voltage controlled oscillator 54 in a normal case stored as 0 is supplied to the voltage controlled oscillator 54 via the D/A converter 62. Therefore, the synchronizing signal T,2 has the same pulse train interval as that shown in FIG. 5f (see FIG. 5hl).
occurs. Therefore, the synchronizing signal T to be supplied to the A/D converter 40 is as shown in FIG.
R2 is the gate signal G.

(see FIG. 5e).

On the other hand, the surface of the stimulable phosphor sheet S is irradiated with a low-energy light beam La emitted from the laser light source 24 in the main scanning direction, and the image information of the subject recorded on the stimulable phosphor sheet S is is extracted as stimulated luminescence light. This stimulated luminescent light enters a photomultiplier 36 via a light guide 38 disposed in the main scanning direction of the stimulable phosphor sheet S, and is converted into an electrical signal. Then, the electric signal from the photomultiplier 36 is added to the signal voltage of the A/D converter 40 via the Roku amplifier 39,
This signal is converted to 7/D for each pulse of the synchronization signal Ts. This A/D-converted pre-read information is introduced into a control circuit (not shown), and the image signal is used to determine the image reading conditions such as high voltage that should be set in the photomultiplier 36 during main reading and/or the setting of the A/D converter 40. Image processing conditions such as gradation processing/frequency processing to be set in a signal processor (not shown) connected to the next stage are set. With the above, the pre-reading work in the fourth step is completed, and the main reading is performed in the next fifth step.

In this case, the switch 53 is switched to the contact 53c side, and the concave lens 30 is removed from the optical path of the light beam L in the direction of arrow C. So, start reading this book. In this case, the galvanometer mirror 18 is adjusted in the second step, that is, the reading start position E1 and the main scanning speed are adjusted in accordance with the amount of accumulated radiation. Since the photomultiplier 36 is set for sensitivity, images can be read under optimal conditions. Note that the image reading operation during this main reading is similar to the reading operation during the pre-reading, so it will not be described in detail.

The image signal obtained by the main reading is subjected to signal processing such as gradation processing and frequency processing by a signal processor (not shown) according to the image processing conditions set based on the above-mentioned pre-reading information, and then transferred to an image recording carrier such as film. Or CRT
The image is reproduced as a visible image on a display such as the following.

[Effects of the Invention] As described above, according to the present invention, before the pre-reading, the grid signal on the stimulable phosphor sheet is The scanning timing of the light beam is adjusted. For this reason,
Pixel shift during pre-reading can be eliminated and accurate pre-reading information can be obtained. Therefore, by determining image reading conditions and/or image processing conditions during main reading based on this pre-reading information, and then performing main reading, a precisely reproduced image 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 that implements the light beam scanning timing control method according to the present invention, and FIG. 2 shows a synchronization signal generation circuit in the radiation image information reading device shown in FIG. 3 is a block diagram of the galvanometer mirror driving section in the radiation image information reading device shown in FIG. 1; FIG. 4 is a flowchart showing the operating procedure of the radiation image information reading device shown in FIG. 1; FIGS. 5a to 5l are explanatory diagrams of signals input and output to each component block of the radiation image information reading apparatus shown in FIG. 1. 10... Radiographic image information reading device 12... Laser scanning unit 14... Image reading unit 1
6... Synchronization signal generation section 18... Galvanometer mirror 20... Drive section 22... Signal processing section 3
2...Scanning lens 34...Half mirror 3
6... Photo multiplier 38... Light guide 40... A/D converter 42... Grid 42a... Transmissive section 42
b...Reflector 44...Light guide 47...
・Waveform shaping circuit 49...Gate circuit 50...
Phase comparator 52...Low pass filter 53...Switch 54...Voltage controlled oscillator 56...Frequency divider 58...A/D converter 60...Control circuit 62...D/A Converter 76...control circuit LSLaSLb...light beam S...stimulable phosphor sheet Go...grid signal Gs...gate signal G,
...Reference grid signal TR, Ts...Synchronization signal W...Sawtooth signal Patent applicant: Fuji Photo Film Co., Ltd. Patent attorney: Takehiro Chiba

Claims (2)

[Claims] (1) A stimulable phosphor sheet on which radiographic image information is recorded is scanned by a light beam serving as excitation light, while a synchronization light beam is used to scan a grid made up of alternating light transmitting and reflective parts. A method for controlling the scan timing of a light beam employed in a radiation image information reading device that generates a synchronization signal from a signal obtained from the synchronization signal and photoelectrically reads the image information based on the synchronization signal, the method comprising: An optical system that widens the beam diameter of the light beam is inserted in the optical path, and the stimulable phosphor sheet is scanned by the light beam irradiated through the optical system to obtain image reading conditions and/or images for visible image reproduction. Before the pre-reading step of reading the outline of radiation image information in order to set processing conditions, the scanning timing of the light beam is adjusted in advance without using the pre-reading optical system, and then the scanning timing of the light beam after the adjustment is adjusted. 1. A method for controlling scan timing of a light beam, characterized in that a pre-reading step is performed depending on the scan timing. (2) In the method according to claim 1, the synchronization signal is generated using a PLL circuit, and the input voltage of the voltage-controlled oscillator constituting the PLL circuit is controlled when the look-ahead optical system is not used. During the storage and look-ahead step, the stored voltage is applied as an input voltage to the voltage controlled oscillator, and the light beam on the stimulable phosphor sheet is controlled based on the synchronization signal output from the voltage controlled oscillator. A method for controlling scan timing of a light beam, the method comprising adjusting scan timing.