JP2001124996A - Scanned image acquisition device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To acquire a high-accuracy sample image over a long time. SOLUTION: A laser light inputted to an optical detector 10 is outputted as a visual field mask signal and converted by a comparing circuit 12 into digital data, which are supplied to time-measuring circuits 14 to 16. When the time-measuring circuit 13 to 16 receive an enable signal from a CPU 17, the time-measuring circuit 14 measures a laser cutoff time Ta, the time measuring circuit 15 measures a laser passage time Tb, and the time-measuring circuit 16 measures a laser cutoff time Tc, and they supply the results to the CPU 17. The CPU 17 calculates a time ratio (Ta+Tc)/Tb and compares it with a preset value. When the calculated time ratio (Ta+Tc)/Tb is different from the set value, the CPU 17 adjusts the gain of a programmable amplifier 18a and performs control, so that the time ratio (Ta+Tc)/Tb matches with the preset value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning image acquiring apparatus, and more particularly to a scanning image acquiring apparatus using a resonant scanner, capable of acquiring a high-precision sample image for a long time. The present invention relates to a scanned image acquisition device.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram showing a configuration of a laser scanning image acquisition device. In the laser scanning image acquisition device of FIG. 5, a one-dimensional (one line) image is acquired by laser-scanning the specimen 47 with the resonant scanner 44 and displayed on the monitor 55.

A laser beam emitted from a laser light source 41 is expanded by a beam expander 42 so as to have a diameter corresponding to a pupil of an objective lens 46. The laser light expanded by the beam expander 42 is transmitted to the polarization beam splitter 4.
The light is reflected by 3 and guided to the resonant scanner 44.

Although the resonant scanner 44 is self-resonant, the self-resonant frequency and vibration amplitude at this time fluctuate depending on the ambient temperature and how the resonant scanner 44 is mounted. That is, the oscillation cycle of the resonant scanner 44 is not constant. For this reason, a resonance scanner drive circuit 52 that detects fluctuations in the oscillation cycle of the resonant scanner 44 and efficiently vibrates the resonant scanner 44 in accordance with the detected oscillation cycle is required.

The resonant scanner 44 has a built-in speed sensor (not shown) for detecting the vibration speed of the resonant scanner 44. A speed feedback signal detected by the speed sensor is supplied to a resonant scanner drive circuit 52. You.

[0006] The resonant scanner drive circuit 52 includes:
The turning point of the mirror 44a (speed feedback signal = 0) is detected from the supplied speed feedback signal. Further, the resonant scanner drive circuit 52 generates a drive signal based on the detected turning point so that the scanning direction of the resonant scanner 44 is reversed, and causes the resonant scanner 44 (mirror 44a) to vibrate repeatedly with the generated drive signal. . Accordingly, the resonant scanner 44 can be efficiently vibrated in accordance with the change in the self-resonant frequency of the resonant scanner 44.

The laser beam guided to the resonant scanner 44 is reflected by a built-in mirror 44a,
It is led to 5. The laser light guided to the 波長 wavelength plate 45 is inclined by 45 degrees in the polarization direction, and guided to the objective lens 46. The laser beam guided to the objective lens 46
The light is collected and reflected as a point on the top.

[0008] The laser light reflected by the sample 47 passes through the objective lens 46 and is guided to the 波長 wavelength plate 45. 1/4
The laser beam guided to the wave plate 45 changes the polarization direction by 4
It is tilted 5 degrees, guided to the resonant scanner 44, and reflected by the mirror 44a. The laser light reflected by the mirror 44a passes through the polarization beam splitter 43,
The light is condensed at 8, and is incident on a photodetector 49 composed of, for example, a photodiode. The photodetector 49 converts the incident laser light into an electric signal (analog image signal) and converts the analog image signal into an analog / digital (A / D) converter 5.
Supply 0.

The resonant scanner drive circuit 52 includes:
Built-in programmable amplifier 52a, CPU (Cent
The gain of the programmable amplifier 52a is changed according to an instruction from the ral processing unit (51). This allows
The amplitude of the drive signal is changed, and the vibration amplitude of the resonant scanner 44 is controlled.

When the sample scanner 47 is laser-scanned by the resonant scanner 44, the scanning speed becomes extremely slow in the vicinity of the turning point of the laser beam due to the characteristics of the resonant scanner 44. It becomes difficult to secure. Therefore, in this region, the sample image is not usually obtained.

FIG. 6 shows a sample 4 by the resonant scanner 44.
7 shows a laser scanning displacement characteristic when laser scanning is performed on No. 7. The horizontal axis in FIG. 6 indicates time T, and the vertical axis in FIG. 6 indicates scanning displacement M.

When the sample 47 is laser-scanned by the resonant scanner 44, the sample 47 is scanned like a motion (simple vibration) in which the sine wave shown in FIG. 6 is projected on the vertical axis. The resonant scanner 44
As described above, when the analog image signal output from the photodetector 49 is sampled at equal time intervals by the analog / digital (A / D) converter 50 because of the non-uniform vibration, the laser scanning is turned back. The scanning displacement M gradually decreases as approaching the point. As a result, the accuracy of the linearity of the sample image decreases as the turning point of the laser scanning approaches.

This means that if the sampling time T ₁ near the center of the laser scanning in FIG. 6 is the same as the sampling time T ₂ near the turning point of the laser scanning, the scanning displacement M ₂ near the turning point of the laser scanning becomes It can also be seen from the fact that the value is smaller than the scanning displacement M ₁ near the center of the laser scanning.

Referring back to FIG. 5, the pixel clock circuit 53 will be described. The pixel clock circuit 53 generates a pixel clock signal for correcting the above-described fluctuation of the scanning displacement M according to a clock generation command signal supplied from the resonant scanner drive circuit 52. The pixel clock circuit 53 has a built-in correction ROM (Read Only Memory) 53a, and the correction ROM 53a previously stores data for equalizing and correcting pixel positions in laser scanning.

The resonant scanner drive circuit 52 includes:
When the speed feedback signal supplied from the resonant scanner 44 becomes 0 (the turning point of the mirror 44a), a clock generation command signal is generated, and the generated clock generation command signal is supplied to the pixel clock circuit 53.

When the clock generation command signal is supplied, the pixel clock circuit 53 reads out correction data stored in advance in the correction ROM 53a, equalizes pixel positions in laser scanning, and generates a pixel clock signal sequence to be corrected. , And supplies the generated pixel clock signal to an analog / digital (A / D) converter 50.

The analog / digital converter 50 samples the analog image signal supplied from the photodetector 49 according to the supplied pixel clock signal. The analog / digital converter 50 converts the sampled analog image signal into digital image data, and supplies the digital image data to the line memory 54 for storage. The digital image data for one line stored in the line memory 54 is read out and displayed on the monitor 55.

[0018]

However, in the above-described conventional laser scanning image acquisition apparatus, since the resonant scanner is controlled to vibrate based on the signal output from the speed sensor, the influence of the ambient temperature and the like is not provided. If an error occurs in the output signal of the speed sensor, the control will be shifted from the resonance point of the resonant scanner, the vibration amplitude of the resonant scanner will fluctuate, and it is possible to acquire a highly accurate sample image for a long time. There was a problem that could not be done.

Further, as described above, near the turning point of the laser scanning, the sample is irradiated with the laser beam even though the sample image is not obtained, but extra damage is given to the sample. There was a problem that.

Therefore, an object of the present invention is to provide a scanning image acquisition apparatus using a resonant scanner, which can acquire a highly accurate sample image over a long period of time and can reduce damage to the sample by laser light. It is another object of the present invention to provide a scanning image acquisition device as described above.

[0021]

In order to achieve the above-mentioned object, one aspect of the present invention is to provide a laser passage portion for passing a laser beam and masks provided at both ends of the laser passage portion for blocking the laser beam. A field mask having a portion is disposed between the resonant scanner and the sample at a position conjugate with the sample.

Thus, the laser beam to the sample can be cut off near the turning point of the laser scanning.
As a result, it is possible to reduce damage to the sample which was given by the laser light in the region where the sample image is not obtained.

[0023] To achieve the above object, the present invention provides:
In a scanning image acquisition device that irradiates a sample with laser light and generates an image from the reflected light, a light separating unit (for example, a polarized beam A splitter 3), a scanning unit (for example, a resonant scanner 4) for scanning the sample with the laser beam, and a laser beam that is arranged between the scanning unit and the sample at a position conjugate with the sample. A field mask (for example, a field mask 6) having a laser passage portion for passing light through and mask portions provided at both ends of the laser passage portion to block the laser light, and reflected light returning from the specimen or the field mask. Using a photodetector (for example, photodetector 10) for detecting the laser beam and an electric signal output from the photodetector, the laser beam passing through the field mask is used. The transit time between the field mask by measuring means for measuring said laser breaking time which the laser beam is interrupted (e.g., the time measuring circuit 14 to 16), characterized in that it comprises a.

According to the present invention, since the laser beam to the sample can be cut off near the turning point of the laser scanning, the damage to the sample caused by the laser beam can be reduced.

According to another aspect of the present invention, the reflected light from the field mask is used to measure the laser transit time when the laser light has passed through the field mask and the laser cutoff time when the laser light has been blocked by the field mask. The vibration amplitude of the resonant scanner is controlled so that the time ratio between the laser transit time and the laser cutoff time becomes constant.

Thus, even when the vibration amplitude of the resonant scanner fluctuates due to the influence of the ambient temperature or the like, the control is performed by directly using the scanning laser beam, so that the error of the speed sensor is not affected. And the vibration amplitude of the resonant scanner can be kept constant. As a result, a highly accurate sample image can be acquired over a long period of time.

[0027] To achieve the above object, the present invention provides:
In a scanning image acquisition device that irradiates a sample with laser light and generates an image from the reflected light, a light separating unit (for example, a polarized beam) that separates the irradiation light for irradiating the sample and the reflected light returning from the sample A splitter 3), a scanning unit (for example, a resonant scanner 4) for scanning the sample with the laser beam, and a laser beam that is arranged between the scanning unit and the sample at a position conjugate with the sample. A field mask (for example, a field mask 6) having a laser passage portion through which light passes and mask portions provided at both ends of the laser passage portion to block the laser light, and reflected light returning from the specimen or the field mask. Using a photodetector (for example, photodetector 10) for detecting the laser beam and an electric signal output from the photodetector, the laser beam passing through the visual field mask. Measuring means (for example, time measuring circuits 14 to 16) for measuring the laser transit time and the laser interception time when the laser light is intercepted by the visual field mask, and the time ratio between the laser transit time and the laser interception time is A time ratio control unit (for example, CPU 17) for controlling the scanning unit so as to be constant.

According to the present invention, when the oscillation amplitude of the resonant scanner fluctuates due to the influence of the ambient temperature or the like, the laser transit time and the laser interception time change respectively, but the time ratio between the laser transit time and the laser interception time is changed. Does not change, the vibration amplitude of the resonant scanner can be kept constant by controlling the vibration amplitude so that the time ratio between the laser transit time and the laser cutoff time is constant. As a result, a highly accurate sample image can be acquired over a long period of time.

[0029]

Embodiments of the present invention will be described below with reference to the drawings. However, such embodiments do not limit the technical scope of the present invention.

FIG. 1 is a block diagram showing the configuration of an embodiment of a laser scanning image acquiring apparatus to which the present invention is applied. The laser scanning image acquisition device of FIG. 1 is different from the laser scanning image acquisition device of FIG. 5 in that a field mask 6, a comparison circuit 12, a counter clock generation circuit 13, time measurement circuits 14 to 16,
And a configuration in which a CPU 17 is added, and controls so as to keep the vibration amplitude of the resonance scanner 4 constant.

FIG. 1 shows a laser light source 1, a beam expander 2, a polarization beam splitter 3, a raisont scanner 4, a mirror 4a, a quarter-wave plate 5, an objective lens 7, a sample 8, a condenser lens 9, and a photodetector. 10, analog / digital (A /
D) Converter 11, resonant scanner drive circuit 1
8, the functions of the programmable amplifier 18a, the pixel clock circuit 19, the correction ROM 19a, the line memory 20, and the monitor 21 are respectively the laser light source 41, the beam expander 42, the polarization beam splitter 43, the Raisont scanner 44, and the mirror of FIG. 44a, quarter wave plate 4
5, objective lens 46, specimen 47, condenser lens 48, photodetector 49, analog / digital (A / D) converter 50,
Resonant scanner drive circuit 52, programmable amplifier 52a, pixel clock circuit 53, correction ROM 5
3a, the line memory 54, and the monitor 55 are the same as those in FIG.

Next, the structure of the field mask 6 will be described with reference to FIG.
This will be described with reference to FIG. FIG. 2A shows a top view of the field mask 6, and FIG. 2B shows a perspective view of the field mask 6. The field mask 6 shown in FIG. 2 is arranged between the quarter-wave plate 5 and the objective lens 7 on a primary image plane conjugate with the focal plane of the sample 8. As shown in FIG. 2B, the field mask 6 is formed of a thin rectangular metal plate (for example, aluminum or the like), and the region 6b has a structure in which the metal plate is removed. The region 6b from which the metal plate has been extracted is a region through which laser light passes, and this region 6b is referred to as a laser passage portion 6b. At both ends of the laser passage section 6b, a mask section 6a, which is an area for blocking laser light, is provided.

The resonant scanner 4 performs laser scanning along a laser scanning line 31 as shown in FIG. In the section a and the section c of the laser scanning line 31, since the laser beam is blocked by the mask section 6a, the image of the specimen 8 is not obtained. On the other hand, the laser scanning line 3
In the section b of 1, an image of the specimen 8 is acquired because the laser light passes through it. The dimension of the field mask 6 in the longitudinal direction is set in advance so that the turning points 31a and 31b of the laser scanning exist on the mask section 6a.

As described above, by disposing the field mask 6 on the primary imaging plane conjugate with the focal plane of the specimen 8, the specimen 8
In the vicinity of the turning points 31a and 31b of the laser scanning where no image is obtained, the laser beam can be cut off unlike the related art. As a result, it is possible to reduce damage to the specimen 8 which has conventionally been caused by the laser light.

Next, control for keeping the vibration amplitude of the resonant scanner 4 constant using the above-described visual field mask 6 will be described with reference to the flowchart of FIG. The control for keeping the vibration amplitude constant is such that even when the vibration amplitude of the resonant scanner 4 fluctuates due to the influence of the ambient temperature or the like, the time when the laser light is cut off by the mask section 6a and the laser light passes through the laser passage section 6b. This is to take advantage of the fact that the time ratio with respect to the set time does not change.

As shown in FIG. 3A, when laser scanning is performed on the visual field mask 6 along the laser scanning line 31 (step S1), sections a and c of the laser scanning line 31 are obtained.
, The laser beam is cut off, and the laser scanning line 31
In the section b, the laser beam passes, and the reflected light is incident on the photodetector 10 (step S2).

The photodetector 10 detects the incident laser light,
For example, it is converted into an analog visual field mask signal as shown in FIG. Here, FIG. 3B shows an output signal of the photodetector 10 when laser scanning is performed along the laser scanning line 31 on the visual field mask 6 shown in FIG. The horizontal axis of (B) represents time T, and FIG.
The vertical axis of (B) indicates the voltage V.

The field mask signal shown in FIG. 3B has a relatively high voltage value because the laser beam is cut off (the laser beam is reflected) in the sections a and c of the laser scanning line 31. In the section b of the laser scanning line 31, the laser light passes (the laser light is not reflected), and thus has a relatively low voltage value.

The photodetector 10 supplies the generated analog field mask signal to the comparison circuit (comparator circuit) 12 (step S3). The comparison circuit 12 converts the supplied analog visual field mask signal into, for example, a digital visual field mask signal as shown in FIG. here,
FIG. 3C shows an output signal of the comparison circuit 12 when the field mask signal of FIG. 3B is input to the comparison circuit 12, and the horizontal axis of FIG. , FIG.
The vertical axis of (C) indicates the voltage V.

The voltage value of the visual field mask signal in FIG.
During the laser cutoff times Ta and Tc when the laser light is cut off by the mask portion 6a, the signal becomes H (High), and during the laser transit time Tb when the laser light passes through the laser passage portion 6b, L (high).
(Low).

The comparison circuit 12 supplies the generated digital visual field mask signal to the time measurement circuit 14, the time measurement circuit 15, and the time measurement circuit 16 (step S4). The time measurement circuit 14 calculates the laser cutoff time Ta by using the time measurement circuit 1.
5 is a circuit for measuring the laser transit time Tb, and the time measuring circuit 16 is a circuit for measuring the laser cutoff time Tc, each of which is constituted by a counter circuit.

The counter clock generation circuit 13 generates a counter clock signal having a pixel frequency or higher, and supplies the generated counter clock signal to the time measurement circuits 14 to 16.

The CPU 17 supplies an enable signal to each of the time measuring circuits 14 to 16 at a predetermined timing. When each of the time measurement circuits 14 to 16 receives the enable signal at a predetermined timing, the time measurement circuit 14 starts counting the counter clock signal supplied from the counter clock generation circuit 13, and the time measurement circuit 14 sets the laser cutoff time Ta to the time. The measuring circuit 15 calculates the laser transit time Tb.
And the time measurement circuit 16 measures the laser cutoff time Tc.

The measured laser cutoff time Ta, laser transit time Tb and laser cutoff time Tc are supplied to the CPU 17 (step S5). The CPU 17 calculates a time ratio (Ta + Tc) / Tb between the laser cutoff time (Ta + Tc) and the laser cutoff time Tb, based on the supplied laser cutoff time Ta, the laser cutoff time Tb, and the laser cutoff time Tc (step S6). Then, a comparison is made with a set value stored in advance (step S7).

When the calculated time ratio (Ta + Tc) / Tb is the same value as the set value, the CPU 17 is built in the resonant scanner drive circuit 18 because the vibration amplitude of the resonant scanner 4 is kept constant. Control is continued without changing the gain of the programmable amplifier 18a (step S8).

On the other hand, the calculated time ratio (Ta + Tc) /
If Tb is different from the set value, the CPU 17 adjusts the gain of the programmable amplifier 18a built in the resonant scanner drive circuit 18 and adjusts the time ratio (Ta + T
c) Control is performed so that / Tb matches the set value (step S9).

As described above, even when the vibration amplitude of the resonant scanner 4 fluctuates, the time ratio (Ta + T
Since c) / Tb does not change, the time ratio (Ta + T
c) By controlling the vibration amplitude of the resonant scanner 4 so that / Tb becomes a constant value, even if the resonance frequency of the resonant scanner 4 changes due to the influence of the ambient temperature or the like, the vibration amplitude of the resonant scanner 4 can be reduced. Can be kept constant. As a result, a highly accurate sample image can be obtained over a long period of time.

In this embodiment, the time ratio (Ta + Tc) / Tb is controlled to be constant.
If the oscillation cycle of the resonant scanner 4 does not fluctuate due to the influence of the ambient temperature or the like, the control may be performed so that either the laser cutoff time Ta or the laser transit time Tb is constant.

In this embodiment, the control for keeping the vibration amplitude constant is performed by using a resonant scanner.
Although the present invention is applied to a two-dimensional laser scanning image acquiring apparatus, it is needless to say that the present invention can also be applied to other two-dimensional laser scanning image acquiring apparatuses to which a galvano scanner or the like is added.

[0050]

As described above, according to the present invention, a field mask is arranged between a resonant scanner and a sample at a position conjugate to the sample, and the field mask is determined by the laser transit time of the laser beam and the field mask. Since the control is performed such that the time ratio with the laser cutoff time when the laser light is cut off is constant, the vibration amplitude of the resonant scanner can be controlled to be constant. As a result, a highly accurate sample image can be acquired over a long period of time.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a laser scanning image acquisition apparatus to which the present invention has been applied.

FIG. 2 is a diagram for explaining a structure of a field mask 6 of FIG.

FIG. 3 is a diagram for explaining the relationship between a field mask 6 and a field mask signal in FIG. 1;

FIG. 4 is a flowchart for explaining control for making the vibration amplitude of the resonant scanner 4 of FIG. 1 constant.

FIG. 5 is a block diagram showing a configuration of a conventional laser scanning image acquisition device.

FIG. 6 is a diagram showing laser scanning displacement characteristics by the resonant scanner 44 of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser light source 2 Beam expander 3 Polarization beam splitter 4 Resonant scanner 4a Mirror 5 1/4 wavelength plate 6 Field mask 6a Mask part 6b Laser passing part 7 Objective lens 8 Sample 9 Condensing lens 10 Photodetector 11 Analog / digital ( A / D converter 12 Comparison circuit 13 Counter clock generation circuit 14 Time measurement circuit 15 Time measurement circuit 16 Time measurement circuit 17 CPU 18 Resonant scanner drive circuit 18a Programmable amplifier 19 Pixel clock circuit 19a Correction ROM 20 Line memory 21 Monitor 31 Laser Scan line

Claims (6)

[Claims] 1. A scanning image acquisition apparatus for irradiating a sample with laser light and generating an image from the reflected light, wherein a light separating unit separates irradiation light for irradiating the sample from reflected light returning from the sample. Scanning means for scanning the sample with the laser light; a laser passing unit disposed between the scanning means and the sample at a position conjugate to the sample; A field mask having mask portions provided at both ends of the portion for blocking the laser beam; light detection means for detecting reflected light returning from the specimen or the field mask; and electricity output from the light detection means Measuring means for measuring, using a signal, a laser transit time during which the laser light has passed through the visual field mask and a laser cutoff time during which the laser light has been interrupted by the visual field mask; Scanning image acquisition apparatus according to claim Rukoto. 2. The scanning device according to claim 1, further comprising a time ratio control unit that controls the scanning unit so that a time ratio between the laser transit time and the laser cutoff time is constant. Image acquisition device. 3. The apparatus according to claim 1, further comprising a time control unit that controls the scanning unit so that the laser transit time or the laser cutoff time is constant. 4. The image processing apparatus according to claim 1, further comprising: an image generation unit configured to generate an image from the electric signal output from the light detection unit; and a display unit configured to display the image generated by the image generation unit. 4. The scanning image acquisition device according to 2 or 3. 5. The field mask is formed of a rectangular metal plate having a predetermined thickness, and its longitudinal dimension is set such that a turning point of the laser beam is located on the mask portion. 5. The scanning image acquisition device according to claim 1, wherein: 6. The scanning image acquiring apparatus according to claim 1, wherein said measuring means comprises a counter circuit.