JPH0830677B2 - Optical scanning device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical scanning device that scans a light beam to destructively obtain tomographic information in a light-transmissive sample.

(Prior Art) An X-ray CT apparatus is generally used to non-destructively obtain tomographic information in a sample. An optical CT apparatus has been proposed which obtains tomographic information of a sample by irradiating light in the visible region to the near-infrared region instead of X-rays (for example, see Japanese Patent Laid-Open No. 60-72542).

In the case of X-ray CT, X-rays are emitted in a fan beam shape for the purpose of speeding up and data of all channels of the detector are collected in parallel, but in the case of light, the influence of scattering is large, so
The pen-beam-shaped light is scanned to collect the detector signal for each channel.

The optical scanning device includes a system in which a light beam from a light source 2 is scanned by rotating a mirror 4 of a scanner as shown in FIG. 4, and a mirror 4a as shown in FIG.
There is a method of scanning by moving in parallel. 6 is a sample, 8
8a is an array photodetector.

As shown in FIG. 6, the data detected by the photodetectors 8 and 8a is converted into a voltage by the I / V (current / voltage) conversion circuit 10, integrated by the integration circuit 12, and then converted to A / It is converted into a digital signal by the D converter 14 and sent to a computer for data processing.

(Problems to be Solved by the Invention) Since light is extremely weakened when an opaque sample is measured, transmitted light is extremely weak, and the data obtained in a portion of the sample has a very poor S / N ratio. That is, the greater the absorption by the sample, the worse the S / N ratio.

Therefore, in order to increase the S / N ratio, the light beam may be slowly scanned at a constant speed, that is, when the light source is pulsed light, the same spot may be emitted several times to collect data, but of course the measurement time Becomes longer. Also, although the overall S / N ratio improves, the S / N ratio of the data at the large absorption is worse than that at the place without the sample, although the data at the large absorption is important. The trend still remains.

The present invention makes the scanning of the light beam slow at a place where the light absorption by the sample is large and fast at a place where the light absorption is small by
An object of the present invention is to provide an optical scanning device capable of increasing the S / N ratio of data at a place where light is largely absorbed and shortening the measurement time.

(Means for Solving the Problems) FIG. 1 schematically shows the present invention.

Reference numeral 20 denotes an optical scanning unit that transmits the light beam from the light source at different positions with respect to the sample 6, and 30 is provided at a position facing the optical scanning unit 20, and receives a plurality of light beams emitted from the optical scanning unit 20. , 40 (or 40a) is a comparing means for comparing the light beam intensity in the channel receiving the light beam of the photodetector of the light receiving portion 30 or its integrated value with a comparison value. And a means for controlling the scanning position so as to control the irradiation amount in each channel of the optical scanning portion 20 according to the output of the comparing means.

(Operation) A light beam is emitted from the light source of the light scanning unit 20, is irradiated onto the sample 6 via the mirror 4 of the scanner, and the transmitted light is detected by one channel of the photodetector of the light receiving unit 30. The control unit 40 (or 40a) controls the scanning position so as to control the irradiation amount in each channel of the optical scanning unit 20 according to the intensity of the transmitted light beam from the photodetector.

In order for the control unit 40 (or 40a) to control the irradiation amount in each channel of the optical scanning unit 20, for example, the scanner of the optical scanning unit 20 is operated until the integrated value of the transmitted light beam intensity in the light receiving unit 30 reaches the comparison value Vr. The light beam from the light source is stopped and emitted, or the light scanning is performed by the light beam pulse or the time preset for the detection intensity of the light detector by one light beam pulse or irradiation of the light beam for a fixed time. A technique such as stopping the scanner of the unit 20 can be used.

(Embodiment) FIG. 2 shows an embodiment.

In the light scanning unit 20, the light beam 3 from the light source 2 is reflected by the rotating mirror 4 of the scanner 21 and is irradiated on the sample 6. The light source 2 may be one that emits pulsed light or continuous light, but in the present embodiment, one that emits pulsed light is used. Reference numeral 22 is a pulse generation circuit, which has a built-in clock, for example, and generates a pulse signal at regular time intervals. The pulse signal from the pulse generation circuit 22 is a delay circuit.
It is sent to the light source 2 via 25, and the light source 2 emits the light beam 2 in synchronization with the delayed pulse signal.

The pulse signal from the pulse generation circuit 22 is also sent to the AND circuit 42 of the control unit 40 and the counter 32 of the light receiving unit 30 which will be described later.

Reference numeral 23 is a counter for counting the pulse signals passed through the AND circuit 42, and 24 is a D / A converter for converting the output value of the counter 23 into an analog signal. The scanner 21 rotates the rotary mirror 4 so as to maintain a proportional relationship between the input voltage from the D / A converter 24 and the swing angle (rotation angle) of the rotary mirror.

In the light receiving section 30, the photodetectors 8 are array-type photodetectors arranged at equal intervals on an arc centered on the rotation axis of the scanner 21 (on the surface of the rotary mirror 4). Photo detector 8
The detection signal of is converted into a voltage by the I / V conversion circuit 10,
It is integrated by the integrating circuit 12.

Reference numeral 31 is a variable gain amplifier, and 32 is a counter that counts the pulse signal from the pulse generation circuit 22 and is reset by the A / D conversion end signal from the A / D converter 14. The amplifier 31 inputs the count value N of the counter 32,
An operation of multiplying the integrated value Vd of the integrating circuit 12 by 1 / N is performed.

The A / D converter 14 is an A / D converter from a comparison circuit 41 of the control unit 40 described later.
The conversion command signal converts the signal from the amplifier 31 into a digital signal and sends it to a computer for data processing. After that, the A / D conversion end signal is sent to the counter 32 and the integration circuit 1
Send 2 as a reset signal.

In the control unit 40, a comparison circuit 41 that compares the integrated value Vd of the integration circuit 12 with the comparison voltage Vr _1, and an output signal of the comparison circuit 41 and a pulse signal from the pulse generation circuit 22 are input.
And a circuit 42.

In the comparison circuit 41, the integrated value Vd from the integration circuit 12 is the comparison voltage.
When Vr ₁ or more, the signal level output to the AND circuit 42 becomes high, and the A / D conversion command signal is output to the A / D converter 14.

In the AND circuit 42, when a high level signal is input from the comparison circuit 41, the pulse signal from the pulse generation circuit 22 is sent to the counter 23.

 Next, the operation of this embodiment will be described.

By the first pulse signal from the pulse generation circuit 22, one pulse light is emitted from the optical scanning unit 20 toward one channel of the photodetector 8. The light transmitted through the sample 6 and detected by the photodetector 8 is converted into a voltage, integrated, and sent to the comparison circuit 41 and the amplifier 31.

Signal Vd from the integrating circuit 12 by one light beam pulse
Is higher than the comparison voltage Vr ₁ , the comparison circuit 41 outputs an A / D conversion command signal, and the amplifier 31 sets N = 1 and the signal Vd is A / D.
It is digitally converted by the D converter 14 and sent to the computer. On the other hand, a high level signal is output from the comparison circuit 41 to the AND circuit 42, and the next pulse signal output from the pulse generation circuit 22 counts up the counter 23 via the AND circuit 42, and then the D / A converter 24 The scanner 21 rotates the rotary mirror 4 by a predetermined amount so that the angle corresponds to the count value. Further, the integrating circuit 12 and the counter 32 are reset after waiting for the end of conversion of the A / D converter 14 to prepare for detection of the next channel. Then, the next light beam 3 is emitted from the light source 2 through the delay circuit 25.

When the output Vd of the integrating circuit 12 by one light beam is less than Vr ₁ , the comparison circuit 41 does not output a high level signal, so the conversion operation of the A / D converter 14 is not performed and the counter 23 also counts. Not up. Therefore the scanner
21 is a pulse generation circuit with the rotating mirror 4 stopped.
Outputs the next pulse signal, and the light source 2 emits the next light beam 3. Thus, the output from the integrator circuit 12
The rotating mirror 4 of the scanner 21 is stopped and the light beam 3 is emitted toward the same channel of the photodetector 8 until Vd becomes equal to or higher than Vr ₁ , and the detection signal passes through the I / V conversion circuit 10 and the integration circuit 12 The number of pulse generations from the pulse generation circuit 22 is counted by the counter 32.

When the count value of the counter 32 reaches N, it means that N light beam pulses have been emitted to the same channel of the photodetector 8, so the amplifier 31 sets the integrated value Vd to N.
A division operation is performed.

When the output Vd from the integration circuit 12 becomes Vr ₁ or more, the A / D converter 14 receives the A / D conversion command signal from the comparison circuit 41 and receives the amplifier 3
The output of 1 is converted into a digital signal and sent to a computer. When the comparison circuit 41 outputs the A / D conversion command signal, the comparison circuit 41 outputs a high level signal to the AND circuit 42, and the next pulse signal passes through the AND circuit 42 and the counter 23
, And the scanner 21 rotates the rotating mirror 4 by a predetermined amount via the D / A converter 24. In addition, the integration circuit 12 and the counter 32
Is reset after waiting for the end of conversion by the A / D converter 14 to prepare for detection of the next channel.

In the present embodiment, the broken line from the integrating circuit 12 to the A / D converter 14 and the broken line from the counter 32 to the computer represent an example for causing the computer to calculate 1 / N without using the variable gain amplifier 31. ing. In that case, the number of pulses N also has to be transferred to the computer.
The amount of data transfer increases and the transfer time increases. Which method should be selected may be determined in relation to the processing speed and storage capacity of the computer used.

Further, N is expected to be very large depending on the amount of light absorbed, so it is desirable to set the upper limit of N. Therefore, when the counter 32 reaches the upper limit of N, the A / D conversion command is forcibly sent to the A / D converter 14, and
A high level signal is sent to the D circuit 42.

Further, if the comparison voltage Vr ₁ is set so that the S / N ratio is effectively improved in the vicinity of the absorption amount of the sample to be measured and the pulse number N is set, it is unnecessary for the channel passing through the portion where the sample is not present. It does not emit a light beam, thus reducing the measurement time.

 FIG. 3 shows another embodiment.

In this embodiment, one light beam 3 is emitted to one channel of the photodetector 8, and the number of pulses of the light beam 3 emitted from that channel is calculated from the intensity of the light beam 6 transmitted through the sample 6 at that time. This is set.

The optical scanning unit 20 and the light receiving unit 30 are the same as those in FIG. However, in FIG. 3, the counter 32 is included on the control unit 40a side. Description of the same parts as those in FIG. 2 will be omitted.

Reference numeral 40a is a control unit, and its configuration is different from that of the control unit 40 shown in FIG.

In the control unit 40a, the integrated value Vd from the integrating circuit 12 is input to the amplifiers 50-1 to 50-3. Amplifier 50-1 to 50
The gains of -3 are K _{1 to} K ₃ , respectively, and K ₁ > K ₂ > K ₃ > 1.
Is. 51-1 to 51-4 are comparison circuits.
Amplifiers 50-1 to 50-at one of the input terminals of -1 to 51-3
3 output signals are respectively input, and the integrated value Vd of the integration circuit 12 is input as it is to one input terminal of the comparison circuit 51-4. The common comparison voltage Vr ₂ is input to the other input terminals of the comparison circuits 51-1 to 51-4.

The output signals D _{0 to} D ₃ of the comparison circuits 51-1 to 51-4 are input to the PROM 52 which is a pulse number setting unit. In the comparison circuits 51-1 to 51-4, the signals D _{0 to} D ₃ are “1” (High) and less than Vr ₂ when one of the input signals is equal to or higher than the comparison signal Vr ₂ which is the other input signal. If there is, it becomes “0” (Low). "1" and "0" may be reversed. Data is stored in the PROM 52 so that the corresponding pulse number Nm is selected according to the combination of the input signals D _{0 to} D ₃ . The selected pulse number Nm is output as a binary number E _{0 to} En (n is an integer).

The E _{0 to} En output from the PROM 52 are input to the latch circuit 54. In the latch circuit 54, the count number N from the counter 32 is 1
It is designed to receive a signal to load only when.
That is, only when the count number N is 1, the inputs E _{0 to} En are sent as they are as the outputs E ₀ ′ to En ′ to the comparison circuit 53, and when the count number N is other than 1, even if the inputs Eo to En change, the output is made.
E ₀ '-En' do not change.

Reference numeral 53 denotes a comparison circuit, which outputs the output values E ₀ ′ to E of the latch circuit 54.
The n'and the output values G _{0 to} Gn 'of the counter 32 are compared. The counter 32 counts the number of pulses from the pulse generation circuit 22. The comparison circuit 53 detects when both input signals match, that is,
AND circuit 42 when E ₀ ′ = G ₀ , E ₁ ′ = G ₁ , ... En ′ = Gn
To the A / D converter 14 of the light receiving section.

The AND circuit 42 is the same as that shown in FIG. 2, and when the high level signal is sent from the comparison circuit 53, the pulse signal of the pulse generation circuit 22 of the optical scanning section is sent to the counter 23.

 Next, the operation of this embodiment will be described.

When the first pulse signal is generated from the pulse generation circuit 22, the counter 32 starts counting and the light source 2 emits one light beam pulse 3 via the delay circuit 25. When the light beam pulse 3 enters the one channel of the photodetector 8 through the sample 6, the integrating circuit 12 outputs the signal Vd. The signal Vd is amplified by amplifiers 50-1 to 50-3 with respective gains K _{1 to} K ₃ and sent to the comparison circuits 51-1 to 51-3. The signal Vd is sent to the comparison circuit 51-4 as it is. Being
Each of the signals is compared with the comparison voltage Vr ₂ and signals D _{0 to} D ₃ corresponding to the magnitude of the signal Vd are output to the PROM 52. The binary number E _{0 to} En of the pulse number Nm selected by the signal is the latch circuit 54.
Is input to Here, the count number N of the counter 32 is 1
Therefore, E _{0 to} En input to the latch circuit 54 are directly input to the comparison circuit 53 as E ₀ ′ to En ′. with this,
The number of pulses corresponding to the signal Vd is set in the comparison circuit 53.

A light beam pulse 3 is sequentially generated from the light source 2 by the pulse signal from the pulse generation circuit 22, and the number of pulse generation is counted by the counter 32.

The light beam pulse 3 is emitted until the count value N matches Nm set in the comparison circuit 53. The signals detected by the channel of the photodetector 8 are integrated and added by the integrating circuit 12 via the I / V converting circuit 10. Integral value Vd of integrating circuit 12
The output E _{0 to} En of the PROM 52 also changes, but the value of the counter 32 is other than 1, so that the outputs E ₀ ′ to En ′ of the latch circuit 54, that is, Nm are latched. Is not changed. On the other hand, Vd is divided by N by the variable gain amplifier 31, and when the count value N of the counter 32 matches Nm, the comparison circuit 53 outputs an A / D conversion command signal, and the output signal of the amplifier 31 is A. The digital signal is converted by the / D converter 14 and sent to a computer for data processing.

On the other hand, the comparison circuit 53 also outputs a high level signal to the AND circuit 42, the pulse signal passed through the AND circuit 42 causes the counter 23 of the optical scanning unit 20 to count up, and the scanner 21 through the D / A converter 24. Rotates the rotating mirror 4 so as to form an angle corresponding to the count value. Further, after the conversion is completed from the A / D converter 14, a reset signal is output to reset the integrating circuit 12 and the counter 32 to prepare for the detection of the next channel.

Hereinafter, the rotary mirror 4 rotated by the scanner 21
Thus, the measurement is similarly performed on the channel of the photodetector 8 on which the light beam 3 is incident.

In FIG. 3, the broken line from the integrating circuit 12 to the A / D converter 14 and the broken line from the counter 32 to the computer show the path when the variable gain amplifier 31 is not used as in FIG.

If a PROM having a large number of inputs D ₀ , D ₂ , ... And outputs E ₀ , E ₁ , ... Is used as the PROM 52 in the control unit 40a, a large number of comparison circuits 51-1, 51-2 ,. Connect them with gain K ₀ , K ₁ , ......
Can be set to a large number, and the number of pulse number settings can be increased.

Further, in the comparison circuits 51-1 to 51-4, the comparison voltage Vr ₂ is made constant and the gains of the amplifiers 50-1 to 50-3 are changed, but the amplifiers 50-1 to 50-3 are omitted, Comparison circuit
Comparing the comparison voltage Vr ₂ of 51-1 to 51-4 with the comparison circuit 51-1 to 51-
The magnitude of the signal Vd may be detected differently for each four.

Using the embodiment of FIG. 3, the light beam 3 from the sample 6
The pulse number Nm can be set according to the magnitude of the absorption amount of, and it becomes possible to obtain the data of an appropriate pulse number for a wide range of absorption.

In the optical scanning unit 20 of the embodiment shown in FIGS. 2 and 3, the light source 2
The light beam from is emitted as a pulse so that the rotating mirror 4 is rotated discontinuously by the scanner 21,
Pulse generation circuit for emitting light beam 3 and scanner 21 operation
The pulse signal from 22 is used for synchronization.

Alternatively, the light beam 3 from the light source 2 may be continuous light. In that case, it is not necessary to consider the operation of the scanner 21 and the synchronization with the light source 2. When continuous light is used, scanning may be controlled by irradiation time instead of controlling the scanning speed of the optical scanning unit by the number of pulses. When the irradiation time is used, it is preferable to set a unit time and control the irradiation time to be an integral multiple of the unit time.

The embodiment is an example in which the present invention is applied to an optical scanning device in which a mirror 4 rotates to scan a light beam as shown in FIG. 4, but as shown in FIG. The present invention can also be applied to an optical scanning device of a type in which a beam is moved in parallel to scan a light beam. In that case, in the embodiment shown in FIG. 2 or 3, the scanner 21 of the optical scanning unit 20 may be replaced with a mechanism for moving the mirror 4a in parallel.

(Effects of the Invention) In the optical scanning device of the present invention, since the irradiation amount in each channel of the optical scanning unit is controlled by the intensity of the light beam transmitted through the sample, the light absorption is large and the S / N ratio is poor. More data can be collected to improve the S / N ratio, and conversely S / N can be obtained even with small data that has small light absorption.
When the N ratio is sufficiently good, the measurement time can be shortened without unnecessary measurement.

[Brief description of drawings]

FIG. 1 is a block diagram showing the present invention, FIGS. 2 and 3 are block diagrams showing an embodiment, and FIGS. 4 and 5 are optical scanning methods of an optical scanning device to which the present invention is applied. FIG. 6 is a block diagram showing a light receiving portion in a conventional optical scanning device. 2 ... Light source, 4 ... Rotating mirror, 8 ... Photodetector, 20 ...
… Optical scanning unit, 21… Scanner, 22… Pulse generation circuit,
30: Light receiving part, 32: Counter, 40, 40a: Control part, 41
…… Comparison circuit, 42 …… AND circuit, 52 …… PROM, 53 …… Comparison circuit, 54 …… Latch circuit.

Claims (1)

[Claims] 1. An optical scanning unit that transmits a light beam from a light source at different positions with respect to a sample, and a plurality of light scanning units that are provided at positions facing the optical scanning unit and that receive the light beam emitted from the optical scanning unit. In a light scanning device having a light receiving section having a photodetector consisting of channels, comparing means for comparing the light beam intensity in the channel receiving the light beam of the photodetector of the light receiving section or its integrated value with a comparison value. And an optical scanning device provided with a control unit for controlling the scanning position so as to control the irradiation amount in each channel of the optical scanning unit according to the output of the comparison unit.