JPH0427843A - Low noise pulse light source using laser diode and voltage detector using the light source - Google Patents

Abstract

PURPOSE:To realize the enhancement of measuring accuracy and the reduction of a measurable lower limit and to obtain large effect in the adaptation to a voltage detector by reducing light intensity noise by stabilizing the light intensity of highly repeated pulse beam. CONSTITUTION:A bias current is preliminarily allowed to flow to a laser diode (LD) 38 and a short pulse electric signal is applied thereto to subject the LD to pulse oscillation and the beam emitted from the other end of the LD is detected by a photodetector 42 such as a photodiode. Since the output of the photodetector is proportional to the light intensity of the beam from the LD, the output is amplified and the bias current of the LD is modulated over a wide frequency region on the basis of the signal from the photodetector by a stabilized current modulating circuit 44. By this method, the LD is automatically controlled so that light intensity becomes constant and the light intensity noise of the LD is also reduced.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a pulsed light source that uses a laser diode to obtain short pulse light (e.g., pulses of 9200 to 2 picoseconds) with a high repetition rate, for example, a repetition frequency of 0.1 to 200 M[(z), and in particular, to The present invention relates to a low-noise pulse light source capable of obtaining optical pulses with extremely stable light intensity and low light intensity noise, and a voltage detection device using this low-noise pulse light source.

[Conventional technology]

The emission wavelength and light intensity of the output light from a laser diode (LD) change as the excitation current and temperature change. Furthermore, the light intensity changes due to longitudinal mode competition and mode hopping. A method to reduce such fluctuations in light intensity is to receive a portion of the laser diode light with a light receiving element such as a photodiode (PD), and obtain an error signal between the detected light intensity level and a preset level. A known method is to feed this back to the excitation current source that drives the laser diode. Such technology is already used in optical pickups of compact disc (CD) players and the like. However, all conventional methods for reducing light intensity fluctuations
It is applied to laser diodes that generate continuous light (continuous wave (CW) light or direct current (DC) light), and noise in the light intensity of pulsed light when generating pulsed light has not yet been discussed. There was also no attempt to stabilize the pulsed light intensity. On the other hand, for example, electro-optical (E-0) sampling (I E
E E J o n al of Quantu
lE 1 electronics, vol, QE-2
2, No. 1, Jan1986 PP69-78
), fluorescence lifetime measurements (Rev, Sci, I n
5trun, 59 (4), April 1
In fields such as response characteristic evaluation of 988 PP663-66'l), photoelectric detectors, optical integrated circuits (OE IC), etc., and time-correlated photon counting methods using photomultiplier tubes, the pulse width of pulsed light is Short pulses of light are required to determine the temporal resolution. From the viewpoint of time resolution, a dye laser that generates pulsed light with a pulse width of picoseconds to femtoseconds is advantageous, but the device becomes large. For this reason, it is simple, simple,
It is conceivable to use an inexpensive and small laser diode as a pulsed light source. Currently, the pulse width of short pulse light that can be generated using a laser diode is about 200 to 2 picoseconds. Also, the wavelength varies depending on the type of laser diode, and is usually 670 nm.
It is about nm to 1.5 μm. Furthermore, if the second harmonic of the pulsed light from a laser diode is generated, pulsed light up to about 340 nn can be obtained. The repetition frequency of such optical pulses varies depending on the purpose, but is generally 0.1 to 200M±. Furthermore, technically it is possible to generate ultra-high repetition pulse light in the GFfz region or pulse light with a repetition rate of several hundred or more.

[Problem to be achieved by the invention]

However, according to experiments conducted by the inventors, it has been found that when such high-repetition optical pulses are used for measurement, fluctuations in the intensity of the optical pulses limit the lower limit of the measurement range. To simplify the explanation, an example will be explained in which the transmittance of the sample 10 to pulsed light is measured using an apparatus as shown in FIG. In the device shown in FIG. 7, a light pulse is generated by a laser diode 12A (see FIG. 8) built into a laser diode (LD) pulse light source 12, and the repetition frequency of the pulse is controlled by an oscillator 14 (for example, Repetition frequency 100M [(z, pulse width 50 picoseconds, wavelength 83
0nl), the LD pulse light source 12 is configured, for example, as shown in FIG. (For example, by applying a negative pulse from a Heulet Paracard 33002A comb generator (registered by WA)), the LD 1
It is designed to drive 2A. The pulsed light generated by the laser diode (LD) 12A"C" is transmitted to the chopper 1 driven by the oscillator 15.
6 (for example, a chopping frequency of 1 kHz), enters the sample 10, and a part of it is absorbed to become output light. The output light is collected by a lens 18 and received by a photodetector 20 made of, for example, a photodiode (PD). The output signal of this photodetector 20 is amplified by a low noise amplifier 22 and synchronously detected by a lock-in amplifier 24. The reference signal of the lock-in amplifier 24 is a chopper signal generated by the oscillator 15. Here, the photodetector 20
The noise generated by the low-noise amplifier 22 is made sufficiently smaller than the noise of the transmitted light itself. The output of the lock-in amplifier 24 is, for example, an output meter 26.
The transmittance is displayed. In addition, in the apparatus shown in FIG. 7, in order to reduce measurement noise and improve measurement accuracy, synchronous detection is performed using the chopper 16 and lock-in amplifier 24, but in simple measurement,
These are unnecessary, and the output of the photodetector 20 may be amplified and directly read out. Furthermore, the low noise amplifier 22 may be omitted and the lock-in amplifier 24 may be used instead. In such an apparatus, if the transmittance of the sample IO to the pulsed light is nonlinear with respect to the incident pulsed light, it is necessary to measure up to a point where the light intensity of the incident pulsed light is sufficiently small. At this time, the noise of the pulsed light of the pulsed light iLD becomes a problem and limits the lower limit of measurement. FIG. 9 shows an example of the noise characteristics of LD pulsed light, which the inventors found through experiments. The horizontal axis is the frequency, and the vertical axis is the effective value of the noise of the light flow (rns
) is expressed in decibels (dB). The OdB point on the vertical axis is the shot noise level (theoretical limit) determined by the square root of the number of photons included in the optical pulse. Therefore,
This figure 9 shows the LD normalized by the shot noise level.
It shows the noise level of pulsed light. The noise caused by the conventional method is shown by the solid line A and the mark X in Figure 9, and the noise when the LD is pulsed is 10 times smaller than the shot noise.
It is found that there is a possibility of reducing this to the shot noise range.The data in FIG. 9 is as shown in FIG.
2A is driven by the drive circuit 30 having the configuration shown in FIG.
2. It was obtained by measuring using a noise component measuring device consisting of a lock-in amplifier 24, an oscillator (OSC) 32 for frequency sweeping, a noise detection circuit 34, and a display 36. The present invention has been made in consideration of the above-mentioned current situation, and provides a laser diode capable of obtaining light pulses in which the light intensity of high repetition pulse light is extremely stable and the light intensity noise is small. Our objective is to provide a low-noise pulsed light source using Another object of the present invention is to provide a device that uses the above-mentioned low-noise pulsed light source to measure voltage with high precision by utilizing the electro-optic effect.

[Means to achieve the task]

The present invention includes a laser diode that repeatedly generates pulsed light, an electric pulse generator that drives the laser diode, a current source that supplies a bias current to the laser diode, and a photodetector that detects a portion of the light emitted from the laser diode. so that the light intensity of the pulsed light is constant and the light intensity noise is reduced according to the output signal of the photodetector,
The above object has been achieved by modulating and controlling the bias current of the current source over a wide frequency band. A laser diode that generates repeated pulsed light, an electric pulse generator that drives the laser diode, a current source that supplies a bias current to the laser diode, and a photodetector that detects a portion of the light emitted from the laser diode. In accordance with the output signal of the photodetector, the amplitude of the pulse signal generated by the electric pulse generator is varied over a wide frequency range so that the light intensity of the pulsed light is constant and the light intensity noise is reduced. This goal has been achieved by controlling modulation across the band. The present invention also includes a laser diode that repeatedly generates pulsed light, an electric pulse generator that drives the laser diode, a current source that flows a bias current to the laser diode, and a photodetector that detects a portion of the light emitted from the laser diode. and modulating the bias current of the current source in a band below a predetermined frequency according to the output signal of the photodetector so that the light intensity of the pulsed light is constant and the light intensity noise is reduced. The above object has been achieved by controlling and modulating the amplitude of the pulse signal generated by the electric pulse generator in a band above a predetermined frequency. Moreover, the above-mentioned problem is achieved by using a step recovery diode as the electric pulse generator. Further, the object has been achieved by incorporating the photodetector and the laser diode as a set in the same package. Furthermore, the above-mentioned problem has been achieved by making the time constant of the feedback system that detects and controls the light longer than the repetition period of the pulsed light. Further, the frequency characteristic of the feedback system has a peak to reduce noise in a specific frequency range, and the frequency of the reference signal of the lock-in amplifier used in the measurement system is set to a frequency within the specific frequency range. Thus, the above-mentioned problem has been achieved. The present invention also provides a type of voltage detection device using an electro-optic material whose refractive index changes depending on the voltage at a predetermined portion of the object to be measured, in which a first electro-optic material that is affected by the voltage at a predetermined portion of the object to be measured is used. a second electro-optic material arranged to compensate for a phase difference due to natural birefringence of the first electro-optic material, and the low-noise pulsed light source according to claim 1.2 or 3. , the second electro-optic material is
is made of the same material as the first electro-optic material, has the same length in the optical axis direction as the first electro-optic material, is aligned along the optical axis, and directs pulsed light from the low-noise pulsed light source along the optical axis. The above object is achieved by making the light incident on the first and second electro-optic materials along the same direction. Further, the second electro-optic material may be arranged such that its optical axis is
The above object has been achieved by arranging the electro-optic material so as to be orthogonal to the optical axis of the electro-optic material. Further, the second electro-optic material may be arranged such that its optical axis is
by arranging the electro-optic material so as to be parallel to the optical axis of the electro-optic material, and providing means for rotating the light beam component by 90 degrees between the second electro-optic material and the first electro-optic material. , the above-mentioned problem has been achieved. Further, in a type of voltage detection device using an electro-optic material whose refractive index changes depending on the voltage at a predetermined portion of the object to be measured,
a first electro-optic material that is affected by the voltage of a predetermined portion of the object to be measured; and a second electro-optic material that is arranged to compensate for a phase difference due to natural birefringence of the first electro-optic material. , a first transparent electrode provided between the first electro-optic material and the second electro-optic material, and a side of the second electro-optic material on which the first transparent ti is provided. 4. The low-noise pulsed light source according to claim 1.2 or 3, wherein the pulsed light is incident along the optical axes of the first and second electro-optic materials. The above-mentioned problem has been achieved by providing the following. Further, the first transparent electrode is held at a ground potential, and the second transparent electrode is held at a ground potential.
The above-mentioned problem can be solved by applying a voltage to the transparent electrode so that the emitted light obtained by removing the direct current component from the leakage state of the emitted light from the first electro-optic material is output from the second electro-optic material. has been achieved. Further, the present invention provides a type of voltage detection device using an electro-optic material whose refractive index changes depending on the voltage at a predetermined portion of an object to be measured, wherein the electro-optic material is positioned at a predetermined position within an optical probe. , a reflection means for reflecting a light beam incident along the central axis of the optical probe is provided at the tip of the electro-optic material, and a side of the electro-optic material opposite to the side on which the reflection means is provided is provided. A transparent electrode is provided on the side, and the light beam is pulsed light emitted from a low-noise pulsed light source according to claim 1.2 or 3, thereby achieving the above object. Further, the above object has been achieved by setting the transparent electrode so that its surface is perpendicular to the central axis of the optical probe. Further, in a voltage detection device of a type using an electro-optical material whose refractive index changes when a voltage is applied, claim 1
．． The electro-optic material is provided with two or three low-noise pulsed light sources, and the electro-optic material is positioned to cover a plurality of measurement positions of the object to be measured, and the electro-optic material is arranged to cover the plurality of measurement positions of the object to be measured, and the electro-optic material Pulsed light from the low-noise pulsed light source enters each part of the optical material to scan each part of the electro-optic material, and changes in the polarization state of the light emitted from each part of the electro-optic material The above-mentioned problem has been achieved by detecting voltages at a plurality of measurement positions on the object to be measured. Further, in a type of voltage detection device using an electro-optic material whose refractive index changes when a voltage is applied, the electro-optic material is positioned so as to cover a plurality of positions of the object to be measured whose voltage is to be detected. , each specific portion of the electro-optic material corresponding to a specific position of the object to be measured receives incident light obtained by dividing the light beam from the low-noise pulse light source according to claim 1.2 or 3 into a number of desired patterns. The object is achieved by detecting a change in the polarization state of the light emitted from the specific portion of the electro-optic material by a detector. Furthermore, the above-mentioned object has been achieved by dividing the light beam from the light source into a large number of incident lights in a grid pattern using a microlens array. Further, in a voltage detection device of a type using an electro-optical material whose refractive index changes when a voltage is applied, claim 1
．． two or three low-noise pulsed light sources, the electro-optic material is positioned to cover a plurality of two-dimensional locations of the device under test where voltage is to be detected; A light beam from the low-noise pulsed light source uniformly enters each two-dimensional portion of the electro-optic material corresponding to a position as parallel light, and the plurality of two-dimensional portions of the electro-optic material The above object has been achieved by using a detector to detect a change in the polarization state of the light emitted from the light source. Furthermore, a voltage detection device of a type using an electro-optic material whose refractive index changes when a voltage is applied, comprising the low-noise pulsed light source of claim 1.2 or 3, wherein the electro-optic material is used for voltage detection. The electro-optic material is positioned so as to cover a plurality of two-dimensional positions of the object to be measured, and each two-dimensional portion of the electro-optic material corresponding to the plurality of two-dimensional positions of the object to be measured is provided with the low noise A light beam with a short pulse width from a pulsed light source is uniformly incident as parallel light, and a change in the polarization state of the light emitted from the plurality of two-dimensional parts of the electro-optic material is detected by a detector. and an observation light source that outputs a light beam of a different wavelength from that of the low-noise pulse light source in order to observe the wiring shape of the object to be measured, and a light beam from the observation light source and the low-noise pulse light source. a switching means for switching a light beam from a light source to enter the electro-optical material; and a switching means for switching a light beam from a light source to enter the electro-optic material; and a phase compensation means for adjusting the voltage at the two-dimensional position of the object to be measured based on a change in the polarization state of the emitted light, which is perpendicular to the wiring shape of the object to be measured observed by the detector. and variable delay means for shifting the timing of incidence of the light beam from the low-noise pulsed light source onto the electro-optic material in order to sample and measure the voltage change at the two-dimensional position of the object to be measured. Thus, the above-mentioned problem has been achieved.

[Action and effect]

FIG. 1 shows an example of the basic configuration of a low-noise pulsed light source according to the first invention. First, a bias current is passed through the laser diode (LD>38), and a short pulse electric signal is applied from the electric pulse generator 40 through the capacitor C1 to
oscillates as a pulse. A photodiode (
It is detected by a photodetector 42 such as PD). Since the output of the photodetector 42 is proportional to the intensity of the LD light, it is amplified, and this signal is used to control the LD 38 in the stabilizing current modulation circuit 44.
By modulating the bias current over a wide frequency band,
The intensity of the LD light is controlled to be constant and the light intensity noise is reduced. In this case, the time constant of the feedback system should be made sufficiently longer than the repetition period of the LD pulsed light.In this way, the light intensity of the LD pulsed light will be automatically controlled to be constant, and the LD Optical noise is also reduced as shown by the broken line B and the Δ marks in FIG. 9 above. The stabilizing current modulation circuit 44 is a light intensity signal comparison circuit 44A that compares the output signal from the photodetector 42 with a level signal, and makes DC components such as temperature changes and temporal drift constant in the light intensity. Then, optical intensity noise is extracted from the output signal of the photodetector 42, and AC noise such as ripple that changes rapidly is extracted.
Light intensity noise extraction circuit 44B for stabilizing components
and a current modulation circuit 44C that modulates the current based on the output signals from the light intensity signal comparison port 1144A and the light intensity noise extraction circuit #144B. Note that in the basic configuration shown in FIG.
Although the bias current flowing through the LD pulsed light is modulated and controlled over a wide frequency band, the configuration in which the light intensity of the LD pulsed light is constant is not limited to this, and the electric pulse generator 4o is configured as shown in FIG. As such, the photodetector 42 and the stabilized electric pulse generator 41 are replaced.
The stabilized electric pulse generator 41
Further, by combining the two, for example, in a band below a predetermined frequency, the bias current of the stabilizing current modulation circuit 44 may be modulated and controlled to In this band, the amplitude of the pulse signal generated by the stabilized electric pulse generator 41 may be modulated and controlled. With the above configuration, it is possible to stabilize the light intensity of the high repetition pulse light and reduce the light intensity noise. Therefore, the optical pulses generated by such an LD can be used for various measurements, such as E-0 sampling, fluorescence lifetime measurement, photoelectric detector, response characteristic evaluation of OE IC, etc., and time-correlated photon counting method using a photomultiplier tube. The present invention can be used in fields such as the above, and improves the measurement accuracy of these measurements, reduces the measurable lower limit, etc., and is particularly effective when applied to voltage detection devices. In the invention according to claims 8 to 10, in addition to the first electro-optic material that is affected by the voltage of a predetermined portion of the object to be measured, for example, an integrated circuit, the phase difference due to the natural birefringence of the first electro-optic material is compensated for. A second electro-optic material is provided that is arranged to. In such a configuration, for example, when incident light having a predetermined polarization component enters the second electro-optic material, the second electro-optic material
Within the electro-optic material, its polarization state changes due to the phase difference due to natural birefringence. Then, when this incident light enters the first electro-optic material, the polarization state changes within the first opto-electric material due to the natural birefringence. Due to the phase difference, its polarization state becomes second
The polarization state of the electro-optic material changes in the opposite direction, and the polarization state changes depending on the voltage applied to a predetermined portion of the object to be measured. As a result, changes in the polarization state based on the phase difference due to natural birefringence are canceled out, and the polarization state changes only depending on the voltage at a predetermined portion of the object to be measured. Further, in the invention of claim 11.12, a first transparent electrode is provided between the first electro-optic material and the second electro-optic material,
This first transparent electrode is held at, for example, a ground potential, and a second transparent electrode is provided on the side of the second electro-optic material opposite to the side on which the first transparent electrode is provided. For example, a predetermined variable voltage is applied to the transparent electrode. In such a configuration, the second electro-optic material always ensures the effect of the phase difference due to natural birefringence in the first electro-optic material, and at the same time, by applying a voltage to the second transparent electrode, the second electro-optic material By removing the DC component from the polarization state of the emitted light from the electro-optic material, and by making the voltage of the second transparent electrode variable in accordance with temperature changes, the polarization of the emitted light from which the DC component has been removed can be changed. The state is constantly compensated so that it does not fluctuate due to temperature changes. In the invention of claim 13 and 14, a reflecting means, such as a four-metal metal film, a dielectric multilayer mirror, etc., is provided at the tip of the electro-optic material, and a reflecting means, such as a four-metal metal film or a dielectric multilayer mirror, is provided at the tip of the electro-optic material, while the opposite side of the electro-optic material from the side where the reflecting means is provided is provided. A transparent electrode is provided on the side. If the surface of this transparent electrode is set perpendicular to the central axis of the optical probe, and the transparent electrode is held at, for example, ground potential, the lines of electric force due to the voltage at a predetermined portion of the object to be measured will be generated within the electro-optic material. , parallel to the central axis of the optical probe. Thereby, the refractive index change of the electro-optic material becomes uniform over the entire electro-optic material, and the polarization state of the light beam can be changed in exact correspondence with the voltage of a predetermined object to be measured. In the invention of claim 15, the electro-optic material is positioned so as to cover a plurality of measurement positions of the object to be measured where the voltage is to be detected, and each part of the electro-optic material corresponding to the plurality of measurement positions of the object to be measured is Each of these parts is scanned by injecting light and 1\\. This scanning may be performed by deflecting the light beam using a movable mirror, an acousto-optic deflector, etc., or
Alternatively, the electro-optic material and the object to be measured may be moved, and the voltages at multiple measurement positions of the object to be measured are determined based on changes in the polarization state of the light emitted from each part of the electro-optic material by such scanning. can be detected with good operability. In the invention of claim 16, the electro-optic material is positioned so as to cover a plurality of positions of the object to be measured where the voltage is to be detected;
A microlens array that directs a light beam from a light source to each specific part of the electro-optic material corresponding to a specific position of the object to be measured.
A holographic lens or a spatial light modulator is used to divide the light into a large number of light beams into a desired pattern. The refractive index of each part of the electro-optic material changes depending on the voltage at each position of the object to be measured, which corresponds to each part. The light beams have their respective polarization states changed according to the refractive index changes of each specific part of the electro-optic material, are outputted as output light from the electro-optic material, and are incident on a detector, such as a two-dimensional photodetector array or a streak camera. do. Thereby, the voltage at a specific position of the object to be measured, for example, a specific two-dimensional position, can be simultaneously detected by the detector. In the invention of claim 18, the electro-optic material is positioned so as to cover a plurality of two-dimensional positions of the object to be measured whose voltage is to be detected, and the electro-optic material corresponds to the plurality of two-dimensional positions of the object to be measured. A light beam from a light source is uniformly incident on each two-dimensional portion of the area. The refractive index of each two-dimensional part of the electro-optic material changes depending on the voltage at each two-dimensional position of the object to be measured corresponding to each two-dimensional part. The polarization state of each incident light beam changes in accordance with the change in the refractive index of each two-dimensional portion of the electro-optic material, and is outputted from the electro-optic material as emitted light, and is sent to a detector,
For example, it is incident on a two-dimensional photodetector array or a streak camera. This allows the detector to simultaneously detect voltages at two-dimensional positions of the object to be measured. In the nineteenth aspect of the invention, the voltage distribution at the two-dimensional position of the object to be measured is displayed by superimposing it on the wiring shape of the object to be measured. First, in order to observe the wiring shape of the object to be measured, the switching means switches the light beam from the observation light source to enter the electro-optic material, and the phase compensation means adjusts the phase of the emitted light for observation. do. When such switching and adjustment are performed, the light beam from the observation light source enters the electro-optic material as parallel light, passes through the electro-optic material, and enters the surface of the object to be measured. It is assumed that a dielectric multilayer II mirror is provided on the bottom surface of the electro-optic material, which transmits the light beam from the observation light source but reflects the light beam from the voltage detection light source. A portion of the light beam from the observation light source that is incident on the surface of the object to be measured is reflected by the wiring shape on the surface of the object to be measured, and is outputted as light from the electro-optic material. The emitted light output from the electro-optic material is applied to a two-dimensional detector via a phase compensation means, and is detected by the detector as visible image data of the wiring shape of the object to be measured. After detecting the visible image data of the wiring shape in this way, the switching means switches the light beam from the pulsed light source to enter the electro-optic material in order to detect the voltage at the two-dimensional position of the object to be measured. , the phase of the emitted light is adjusted for voltage detection by the phase compensation means. At this time, the operation of the object to be measured needs to be synchronized with the pulsed light. When such switching and adjustment are performed, the voltage at the two-dimensional position of the object to be measured at one sampling timing is detected in the detector in the same manner as in the invention of claim 18. The visible image data of the wiring shape of the object to be measured detected in is displayed on a display or the like, and the voltage distribution of the object to be measured at one sampling timing is displayed by superimposing this data. Next, the light beam from the pulsed light source is slightly delayed by the variable delay means to skip the previous sampling timing, and the voltage at the two-dimensional position of the object to be measured is detected at a slightly shifted timing and displayed by the display means. This makes it possible to visually observe temporal changes in the voltage distribution at the two-dimensional position of the object to be measured, superimposed on the wiring shape of the object to be measured, on the display screen.

【Example】

Embodiments of the present invention will be described in detail below with reference to the drawings. The first embodiment of the present invention embodies the basic configuration shown in FIG. 1, and as shown in FIG. A photodiode (PIN-PD) 43 and the PIN-PD
a first amplifier 46 that inverts and amplifies the photocurrent signal received by the PD 43 and changes the DC level of the output signal;
The stabilizing current modulation circuit 44 includes a second amplifier 48 that operates as an inverting current amplifier that inverts and amplifies the output of the first amplifier 46. A capacitor C2 is inserted into the feedback loop of the first amplifier 46, so that the time constant of the first amplifier 46 is longer than the repetition period of the pulsed light. Further, a diode D is provided in the feedback loop of the second amplifier 48 to set the minimum value of the bias current to zero and prevent a reverse bias current from flowing. Since the other points are the same as the basic configuration shown in FIG. 1, detailed explanation will be omitted. The operation of the first embodiment will be explained below. For example, when the pulsed light intensity of LD38 increases, the PIN
-The photocurrent of PD 43 increases, and the potential at point a increases. Then, the output voltage of the first amplifier 46 decreases, and as a result, the output current of the second amplifier 48 (the direction of the arrow in the figure is positive), that is, the bias tK decreases. Therefore, L.D.
The intensity of the output light at 38 is decreased and controlled to be constant. A specific example of the configuration of the first embodiment is shown in FIG. In this specific example, the amplifiers 46, 48 are comprised of individual transistors, capacitors, resistors, and the like. Further, one set of LD 38 and PIN-PD 43 is housed in the same package 50 to achieve miniaturization. Next, a second embodiment of the present invention will be described in detail with reference to FIG. In this second embodiment, the direct current (DC) bias current flowing from the current source 52 to the LD 38 is constant, and the photodetector 42
A stabilized electric pulse generator 4 whose amplitude can be controlled over a wide frequency band by amplifying the signal received by the amplifier 54
1 to modulate the amplitude of the pulse voltage applied to the LD 38. The stabilizing electric pulse generator 41 is a light intensity signal comparison port that compares the signal from the amplifier 54 with a level signal and makes constant DC components such as temperature change and temporal drift in the intensity of the LD pulsed light. 141A and a light intensity noise extraction circuit 4 that stabilizes AC components such as ripples that change rapidly.
1B, and an amplitude modulation port #141C that modulates the amplitude of the output pulse voltage based on a signal whose DC component is made constant by these circuits and whose noise is extracted. That is, when the intensity of the LD pulse light is strong, the amplitude of the pulse voltage is controlled to be reduced. In this way, the intensity of the LD pulsed light becomes constant and noise is also reduced. In the first and second embodiments, either the DC bias current or the amplitude of the pulse voltage is modulated, but both may be modulated simultaneously (third embodiment). In the case of the third embodiment, it is effective to separate the modulation bands of the two modulation methods.
kHz frequency is controlled by DC bias current, 1
The frequency higher than kt[z can be controlled by the amplitude of the pulse voltage. Next, a fourth embodiment of the present invention will be described in detail. In this fourth embodiment, the feedback system (photodetection-amplification-control) explained in the first and second embodiments is given a frequency characteristic, and the normalized noise obtained by this is shown in FIG. , the lock-in amplifier of the measurement system is synchronized at a frequency with little noise. Specifically, FIG. 6 shows a configuration example applied to non-contact E-0 sampling. In this configuration example, the LD
The laser beam (optical pulse for sampling) generated at
is guided to an optical probe 58 placed above the. This optical probe 58 includes, for example, a lens 58A and a half mirror 5.
It is composed of 8B and electro-optic crystal 58C, and the IC
Utilizing the change in the refractive index of the electro-optic crystal 58C due to the electric field generated on its surface by the current flowing through the electro-optic crystal 58C,
The optical pulse for sampling is modulated. The optical pulse modulated by the change in refractive index is detected by a photodetector 60 and outputted via a lock-in amplifier 62. The lock-in amplifier 62 and the IC drive circuit 8 @ 64, which performs on/off control of the electric circuit at the lock-in frequency, are controlled by the output of an oscillator 66 for controlling the on/off of electric pulses, and the IC drive circuit A synchronizing signal is output from 64 to the electric pulse generator 40. In this way, low-noise detection is possible. or,
Although reducing noise in a wide frequency range is generally an afterthought, reducing noise at a specific frequency can reduce the noise of the entire measurement system. In the above embodiments, the present invention was applied to E-0 sampling, but the scope of application of the present invention is not limited to this, and includes fluorescence lifetime measurement for measuring laser-excited fluorescence,
It is clear that the present invention can be similarly applied to evaluation of response characteristics of photoelectric detectors, OE ICs, etc., time-correlated photon counting methods using photomultiplier tubes, and the like. Next, an embodiment of a voltage detection device using the low-noise pulsed light source will be described with reference to the drawings. FIG. 11 is a partial block diagram showing an embodiment of a voltage detection device of the type that detects the voltage of the object to be measured by utilizing the change in the polarization state of the light beam depending on the voltage of a predetermined portion of the object to be measured. FIG. In FIG. 11, the voltage detection device 70 includes an optical probe 72
, a low-noise pulse light source 73 similar to that shown in FIGS. 1 to 4, and an optical fiber that guides the light beam output from the low-noise pulse light source 73 to the optical globe 72 via a condenser lens 74. 75, an optical fiber 77A that guides the reference light from the optical probe 72 to the photoelectric conversion element 77 via the collimator 76, and an optical fiber that guides the emitted light from the optical probe 72 to the photoelectric conversion element 80 via the collimator 79. 80A and a comparison circuit #181 for comparing the photoelectrically converted electrical signals from the photoelectric conversion elements 77 and 80. In the optical probe 72, two electro-optic materials 72A and 72B made of, for example, optically-axial crystal lithium tantalate (LiTaO3) are arranged. The electro-optic materials 72A and 72B are made of the same material (optically-axial crystal) and have equal lengths in the optical axis direction; The optical axes of the material 72B are arranged to be orthogonal to each other. A conductive electrode 82 is provided on the outer periphery of the electro-optic material 72A and a part of the outer periphery of the electro-optic material 72B.
A reflecting mirror 83 made of metal WiM or a dielectric multilayer film is attached to the tip of the electro-optic material f472B. The optical probe 72 further includes a collimator 84, condensing lenses 85 and 86, and a polarizer 8 for extracting only a light beam having a predetermined polarization component from the light beam from the collimator 84.
7, a polarizer 87 splits a light beam having a predetermined polarization component into a reference light and an incident light, and an electro-optic material 72
Eight beam splitters are provided for inputting the emitted light from A to the analyzer 88. The reference light and output light are
Optical fibers 77 via condensing lenses 85 and 86, respectively.
A, it is designed to be output to 80A. Also, the conductive diameter 82 is held at ground potential. As a result, no electric field exists within the electro-optic material 72A, so that the refractive index of the electro-optic material 72A does not change depending on the voltage at a predetermined portion of the object to be measured. Therefore, the polarization state of the light beam traveling through the electro-optic material 72A changes only by the phase difference due to the natural birefringence of the electro-optic material 72A. On the other hand, the electro-optic material 72B has the potential induced in the reflecting mirror 83 by the voltage at a predetermined portion of the object to be measured, and the conductive electrode 8.
The refractive index changes depending on the potential difference with the ground potential of No. 2. Therefore, the open state of the light beam traveling through the electro-optic material 72B changes depending on the voltage at a predetermined portion of the object to be measured, and also changes depending on the phase difference due to natural birefringence. Note that the optical axis of the electro-optic material 72A and the electro-optic material 72
Since the optical axes of B and B are perpendicular to each other as described above, the change in the polarization state of the light beam in the electro-optic material 72A due to natural birefringence and the natural birefringence in the polarization state of the light beam in the electro-optic material 72B. Changes based on are opposite to each other. In the voltage detection device 70 having such a configuration, the optical beam of a predetermined polarized light component output from the polarizer 87 enters the electro-optic material 72A as incident light via the beam splitter 89. The polarization state of the incident light that has entered the electro-optic material 72A changes due to the phase difference due to the natural birefringence of the electro-optic material 72A, and then enters the electro-optic material 72B from the electro-optic material 72A. By the way, since the lengths of the electro-optic material 72A and the electro-optic material 72B in the optical axis direction are equal to each other as described above, the polarization state of the incident light incident on the electro-optic material 72B is the natural birefringence of the electro-optic material 72B. The polarization state changes due to the refractive index change based on the potential of the reflecting mirror 83. Therefore, at the time when the incident light reaches the reflecting mirror 83, the polarization state of the incident light has changed in accordance with the change in the refractive index of the electro-optic material 72B based on the voltage at a predetermined portion of the object to be measured. The effect of phase difference due to refraction is removed. Also, when the incident light is reflected by the reflecting mirror 83 and returns to the electro-optic material 72B and the electro-optic material 72A as output light, the change in the polarization state due to the phase difference due to natural birefringence is canceled out, and the output light is The polarization state of the emitted light further changes in response to the change in the refractive index of the electro-optic material 72B based on the voltage of the object to be measured. Therefore, the polarization state of the output light that enters the analyzer 88 has changed from the polarization state of the input light that is split by the beam splitter 89, and this change is not affected by the phase difference due to the natural birefringence of the electro-optic material. It doesn't contain anything. In the voltage detection device 70 having such a configuration, the tip of the optical probe 72 is brought close to an object to be measured, such as an integrated circuit (not shown), during detection. As a result, the optical probe 7
The refractive index of the tip @ portion of the electro-optic material H72B of No. 2 changes. More specifically, in an optically axial crystal or the like, the difference between the refractive index of ordinary light and the refractive index of extraordinary light in a plane perpendicular to the optical axis changes. The light beam output from the low-noise pulse light source 73 passes through the condenser lens 74 and the optical fiber 75 to the light beam 72.
The light beam enters the collimator 84, and is further converted into a light beam with a predetermined polarization component intensity 2 by the polarizer 87.
2A and 72B. The intensity of the reference light and incident light split by eight beam splitters is I/2.
becomes. Since the refractive index of the tip 83 of the electro-optic material 72B changes depending on the voltage of the object to be measured as described above, the polarization state of the incident light incident on the electro-optic material 72B depends on the change in the refractive index at the tip. When the length of the tip of the electro-optic material 72B is 1, the polarization of the incident light is The state changes in proportion to the refractive index difference between the ordinary light and the extraordinary light due to the voltage and the length 2. The emitted light returned to the beam splitter 89 enters the analyzer 88. The intensity of the emitted light is set to I/4 by the beam splitter 89. For example, if the analyzer 88 is configured to pass only a light beam with a polarization component orthogonal to the polarization component of the polarizer 87. , the output light with an intensity of I/4 that changes its polarization state and enters the analyzer 88 is determined by the analyzer 88 to have an intensity of (I
/4) 5in2C(π/2)·V/Vo) and is applied to the photoelectric conversion element 80. Here, V is the voltage of the object to be measured, and VO is the half-wavelength voltage. In comparison FI@81, the intensity I/2 of the reference light photoelectrically converted in the photoelectric conversion element 77 and the intensity (I/4) of the output light photoelectrically converted in the photoelectric conversion element 80.
5in2 ((π/2) V/Vo) is compared. Intensity of emitted light (I/4) ・sin' ((π/2)
V/Vo) changes due to a change in the refractive index of the tip 83 of the electro-optic material 72B as the voltage changes, and therefore, based on this, the voltage of a predetermined portion of the object to be measured, for example, an integrated circuit, can be detected. In this way, the voltage detection device 70 shown in FIG. 11 detects the object to be measured based on the change in the refractive index of the tip of the electro-optic material 72B, which changes when the tip of the optical probe 72 approaches the object to be measured. Since the voltage of a predetermined part is detected, the optical globe 72 is used to detect the voltage of a minute part of an integrated circuit, which cannot be brought into contact with the ground, and which may affect the voltage to be measured by contacting the optical globe 72. It can be detected without causing any damage. In addition, a low-noise pulse light source 73 including a laser diode that outputs light pulses with a very short pulse width is used as a light source to sample the high-speed voltage changes of the object to be measured in a very short time width. It also becomes possible to detect changes with high precision. By the way, the optical probe 7 of the voltage detection device 70 in FIG.
Many of the electro-optic materials used in 2 have natural birefringence.4 For example, in the optically-axial crystal lithium tantalate (LiTaO3), the refractive index no for ordinary light and the refractive index ne for extraordinary light are A phase difference occurs due to natural birefringence that is proportional to the difference between the two. This phase difference due to natural birefringence occurs even when no voltage is applied to the optically axial crystal, and the polarization state changes due to this phase difference. Therefore, when attempting to accurately extract the voltage of the object to be measured by extracting only the change in the polarization state due to the change in the refractive index when a voltage is applied, it is necessary to cancel out the phase difference due to natural birefringence. Further, in order to detect the voltage at a predetermined portion of the object to be measured with high sensitivity, it is necessary to remove the DC component from the light emitted from the analyzer 88. More specifically, when the voltage to be measured at a given portion is a rapidly changing voltage superimposed on a DC voltage, we want to detect only the rapidly changing voltage component, so we remove changes in the polarization state that depend on the DC voltage. There is a need. For this reason, a phase compensator is provided between the beam splitter 89 and the electro-optic material, and by adjusting this phase compensator, changes in the polarization state of the output light output from the electro-optic material can be changed to the electro-optic material. There are devices that allow the phase compensator to be set only by the applied voltage, but even if the phase compensator is manually adjusted to a predetermined adjustment value at the start of voltage detection, subsequent temperature changes may cause the phase compensator to be set at the start of voltage detection. The problem is that the adjusted value is no longer appropriate, and accurate detection results cannot be obtained over the entire period of voltage detection. In the above embodiment, in addition to the electro-optic material 72B that is affected by the voltage of a predetermined portion of the object to be measured, an electro-optic material 72A made of the same material and having the same length in the optical axis direction is used. These electro-optic materials f172A,
The analyzer 8
The polarization state of the outgoing light incident on the electro-optic material 72B can be changed relative to the polarization state of the incoming light by an amount that depends only on the voltage applied to the electro-optic material 72B. Moreover, this does not require any complicated operation of adjusting the phase compensator at the start of voltage detection, and even if the temperature of the environment changes, the electro-optic material 72A and the electro-optic material fI
Since the phase difference due to natural birefringence with respect to 72B changes in exactly the same way, changes in the polarization state due to the phase difference due to natural birefringence can always be canceled out. In the above embodiment, compensation for the phase difference due to the natural birefringence of the electro-optic material is achieved by arranging the first and second electro-optic materials so that the optical axis is orthogonal to each other. For example, instead of making the optical axes of the electro-optic material 72C and the electro-optic material 72B orthogonal to each other as in the optical probe 90 of the second embodiment of the voltage detection device shown in FIG. It may be provided. Note that a conductive electrode 8 is provided on the outer circumference of the electro-optic material 72C1λ/2 plate 91 and a part of the outer circumference of the electro-optic material 72B.
2 is provided. The conductive type @82 is held at ground potential and there is no electric field within the electro-optic material 72C. FIG. 13 is a sectional view showing a main part of a third practical example of the voltage detection device according to the present invention. In the voltage detection device 92 of FIG. 13, the same low-noise pulse light source 73 as described above is used, and the lengths in the optical axis direction are equal to each other in the optical probe 93, as in the voltage detection device 70 of FIG. Two electro-optic materials 72A and 72B are provided with their optical axes perpendicular to each other, and a transparent electrode 94 is provided between the two electro-optic materials 72A and 72B. A transparent electrode 95 is provided on the opposite side to the side where the transparent electrode 95 is provided. The transparent electrodes 94, 95 are configured to transmit light incident on the electro-optic materials 72A, 72B and light emitted from the electro-optic materials 72A, 72B, and in use, the transparent electrodes 94 are held at a ground potential. , a variable voltage VB is applied to the transparent electrode 95. That is, the refractive index of the electro-optic material 72B changes depending on the potential difference between the voltage of the object to be measured and the ground potential of the transparent electrode 94, and the refractive index of the electro-optic material 72A changes depending on the difference between the variable voltage V applied to the transparent electrode 95 and the ground potential of the transparent electrode 94. The refractive index changes depending on the potential difference. Note that the transparent electrode 94 is arranged parallel to the reflecting mirror 83, and the lines of electric force from the object to be measured via the reflecting mirror 83 become parallel to the central axis of the electro-optic material 72B within the electro-optic material 72B. That's what I do. This makes the refractive index change uniform at all positions within the electro-optic material 72B. Similarly, the transparent electrode 95 and the transparent electrode 94
Since the lines of electric force within the electro-optic material 72A are parallel to the central axis of the electro-optic material 72A, the refractive index change is uniform at all positions within the electro-optic material 72A. I consider it a thing. In the voltage detection device 92 having such a configuration, the length of the electro-optic material 72A is made the same as the length of the electro-optic material 72B, similarly to the voltage detection device 70 of FIG.
Since the optical axes of the electro-optic material 2B and the electro-optic material 72A are orthogonal to each other, the phase difference due to natural birefringence can always be canceled out even if the environmental temperature changes. Further, by applying a predetermined voltage to the transparent electrode 95 for 7 days and causing a predetermined change in the refractive index in the electro-optic material 72A, the operating point is changed to the 14th point.
The DC component can be removed from the polarization state of the light emitted from the electro-optic material 72B by shifting the operating point P1 to P2 shown in the figure. Furthermore, when the temperature changes, the output light intensity at the operating point P2 changes accordingly, but by automatically changing the voltage VB to follow the temperature change and slightly moving the operating point P2, it is possible to prevent This compensates for fluctuations in the intensity of the emitted light. That is, by automatically changing the voltage according to temperature changes and changing the refractive index of the electro-optic material 72A, the output light intensity is prevented from changing due to temperature. According to this embodiment, the electro-optic material 72A can always cancel the phase difference due to natural birefringence, and at the same time, by applying the variable voltage vB to the transparent T&95, the DC component can be removed from the output intensity. By setting the operating point, it is possible to constantly compensate for the intensity of the emitted light from which the DC component has been removed from fluctuating due to temperature changes. Next, a fourth embodiment of the voltage detection device will be described with reference to FIG. 15. In the voltage detection device 96 of this embodiment, like the voltage detection device described above, an electro-optic material 97A having a tip 97B in the shape of a truncated cone is provided in the optical probe 97, for example, an optical-axial crystal of lithium tantalate (LTa03). ), lithium niobate (Li Nb Os ), etc., and a metal thin film reflecting mirror is provided at the tip 97B of the electro-optic material 97A to reflect the incident light IB having a predetermined polarization component as the output light RB. 98 are provided. Note that this metal thin film reflecting mirror 98 is adapted to reflect the incident light IB as described above and to induce a voltage in a predetermined portion of the object to be measured. Further, in this voltage detection device 96, the surface is a light globe 97.
A transparent electrode 99 perpendicular to the central axis yaA-A is provided above the electro-optic material 97A. It is assumed that an antireflection film is deposited on the transparent electrode 99. This transparent pole 99 allows the incident light IB and the reflected light RB to pass therethrough without having any effect on them, and also allows the electro-optic material 9 to pass through the incident light IB and the reflected light RB by applying a voltage to a predetermined portion of the object 6.
The refractive index change within 7A can be made uniform. In this embodiment, the low-noise pulsed light source 73 is used except that the optical probe 97 includes a single electro-optic material 9'7A, a reflecting mirror 98, and a transparent electrode 99.
, and other configurations are the same as those of the embodiment shown in FIG. 11, so illustration and explanation will be omitted. In the voltage detection device 96 having such a configuration, the optical probe 9
7 approaches the object to be measured 100, a voltage is induced in a predetermined portion of the object to be measured in the metal thin film reflecting mirror 98. That is, the metal thin film reflecting mirror 98 receives the voltage of the portion INAR of the object to be measured 100 immediately below it and the voltage of the portion INA.
A potential due to the voltage of the portion 0TAR outside R is induced. For example, when the nine transparent electrodes are held at a ground potential, electric lines of force ELNI are generated in the electro-optic material 97A based on the potential difference between the potential of the metal thin film reflector 98 and the ground potential of the transparent electrode 99.
is born. By the way, the electric line of force ELNI generated in the electro-optic material 97A is caused by the surface of the transparent T & 99 being the optical probe 1.
Since the transparent electrode 99 and the metal thin film reflector 98 are positioned parallel to each other,
It is parallel to the central axis AA of the electro-optic material 97A. As a result, the refractive index change of the electro-optic material 97A due to the electric line of force ELNI becomes uniform throughout, so that the polarization of the light beams, that is, the incident light IB and the reflected light RB, within the electro-optic material 97A becomes uniform. The component changes in accordance with the voltage of a predetermined portion of the object to be measured, and the voltage of the predetermined portion of the object to be measured 1o○ can be accurately detected. Note that in the optical probe 97 of the voltage detection device, a metal thin film reflecting mirror 98 is provided at the tip 97B of the electro-optic material 97A, but this may be a dielectric multilayer film. Next, a fifth embodiment of the voltage detection device will be described based on FIG. 16. In this voltage detection device 101, the electro-optic material 102 is
It is fixed close to or in contact with an object to be measured, such as an IC (integrated circuit) 56. This electro-optic material 102 has a columnar or plate-like shape, and its cross section is sufficiently larger than that of the electro-optic material housed in the optical probe of a conventional voltage detection device.
It is cut out to a size that covers multiple measurement positions of the IC 56. Note that a reflective mirror 103 made of metal or a dielectric multilayer film is formed on the bottom surface of the electro-optic material 102. If a metal reflecting mirror is formed, it is necessary to measure without contacting the IC 56 or to measure through an insulator placed on the surface of the IC 56. The voltage detection device 101 also includes a low-noise pulsed light source 73, a polarizer 104 for extracting a predetermined polarized light component from the light beam from the low-noise pulsed light source 73, and a polarizer 104 for extracting a predetermined polarized light component from the light beam from the low-noise pulsed light source 73. two movable mirrors 105.106 for guiding the light beam and a movable mirror 105.10
A beam splitter 107 makes the light beam guided by the electro-optic material 102 enter the electro-optic material 102 as incident light, and a beam splitter 107 splits the light emitted from the electro-optic material 102. It includes an analyzer 109 that extracts a predetermined polarized light component from emitted light, and a detector 110 into which the emitted light from the analyzer 109 enters. The results detected by the detector 110 are sent to the computer 111, where they are processed, stored in a memory (not shown), and displayed on the display 112 at the end of the voltage detection process. It has become so. By the way, in this voltage detection device 101, the electro-optic material f1
102 is cut out to a size that includes multiple measurement positions of the IC 56 as described above, and in order to sequentially detect the voltages of the multiple measurement positions of the IC 56, the incident light is The light is scanned in the axial direction and the Y-axis direction, and is sufficiently focused to enter the electro-optic material 102. A movable mirror 105 is provided for scanning in the X-axis direction, and a movable mirror 106 is provided for scanning in the Y-axis direction. That is, movable mirror 105.10
6 is a drive circuit 11 controlled by the computer 111 when the computer 111 determines that the detection of voltage at one measurement position of the IC 56 has been completed;
3 to sequentially scan the light beam in the X-axis direction and the Y-axis direction. In the voltage detection device 101 having such a configuration, a light beam from the low-noise pulsed light source 73 is extracted with a predetermined polarization component by a polarizer 104, guided by movable mirrors 105 and 106, and then passed through a beam splitter 107 to be sufficiently polarized. The light enters the electro-optic material 102 in a narrowed state. It is assumed that the movable mirrors 105 and 106 are initially set so that the incident light enters the position (X+, Y+) shown in FIG. 17, for example. Position of electro-optic material 102 (×1, V+
), the refractive index changes by a predetermined amount in response to the voltage of the object under test, so the incident light that enters the position (x1, V+) changes its polarization according to the change in the refractive index. The light changes depending on the state of the light, is reflected by the reflecting mirror 103, is outputted as light from the electro-optic material 102, and is applied to the detector 110 via the beam splitter 107 and the analyzer 109. Detector 11
0, the voltage at the measurement position of the IC 56 directly below the position (X+, V+) of the electro-optic material 102 is detected and sent to the computer 111. The computer 111 performs predetermined data processing on the voltage at the measurement position of the IC 56 directly below the detected position (×1, Vl) and stores it in a memory (not shown). In order to detect the potential at the measurement position of the IC 56 directly below the next scanning position, the drive circuit 113 is controlled to drive the movable mirror 105. As a result, the movable mirror 105 moves in the X-axis direction so that the incident light is incident on the next scanning position of the electro-optic material 102, and the same voltage detection process as described above is performed. In this way, the movable mirror 105 moves sequentially in the X-axis direction, and the incident light is directed to the position (xn
, y+), and the position (xn, y+
), the computer 111 detects the voltage at the measurement position of the IC 56 directly below the portion y.
In order to scan in the X-axis direction in 2, the drive circuit 11
3 to drive the movable mirrors 105 and 106. As a result, the movable mirror 106 is set so that the incident light enters the next scanning position y2 in the YIFllI line direction, and by sequentially moving the movable mirror 105 from position x1 to position xn, the electro-optic material 102 is Position (X+, V2)
From position (Xn, y2), voltage detection processing similar to that described above is performed. In this way, the movable mirror 106 is set so that the incident light enters the scanning position Vm in the Y-axis direction, and the movable mirror 106
5 from position WX+ to position
By detecting the voltage at each position up to ym), voltage detection at a plurality of measurement positions of the IC 56 is completed. Incidentally, when the voltage detection is completed, the voltage detection results at each measurement position stored in the memory of the computer 111 are displayed on the display 112. As described above, in the voltage detection device 101 of the embodiment, with the electro-optic material 102 fixed, a focused light beam is sequentially scanned and incident on the electro-optic material 102, thereby measuring a plurality of measurement positions of the IC 56. Voltage can be detected. Note that an acousto-optic deflector may be used instead of the movable mirrors 105 and 106. The acousto-optic deflector is driven by a drive circuit controlled by the computer 111, and directs the light beam from the polarizer 104 to the X-axis. direction and the Y-axis direction. As a result, in exactly the same manner as the voltage detection device 101 shown in FIG.
It is possible to detect voltages at multiple measurement positions of an object to be measured such as No. 6. Further, the voltage detection device 101 scans by deflecting the light beam from the low-noise pulse light source 73, which moves the electro-optic material 102 and the object to be measured in the X-axis direction and the Y-axis direction. By electro-optic material 10
2 may be scanned. In this case, the light beams from the light source 73 and the polarizer 104 are
The electro-optic material 10 is transferred from the beam splitter 107 via a movable mirror 105, 106 or an acousto-optic deflector.
2, the light is directly incident without being polarized. Note that the light beam incident on the electro-optic material 102 is in a sufficiently focused state. On the other hand, a motor table that moves the electro-optic material 102 and the object to be measured in the X-axis direction and the Y-axis direction is driven via a drive circuit controlled by the computer 111. Note that in the above description, both the electro-optic material 102 and the object to be measured are moved, but only the object to be measured may be moved. Next, a sixth embodiment of the voltage detection device will be described with reference to FIG. In the voltage detection device 114 shown in FIG. 18, the electro-optic material 102 is cut to a size that covers a plurality of two-dimensional positions of the IC 56, etc., which is the object to be measured, as in the embodiment shown in FIG. 16. has been done. A reflective mirror 103 made of metal or a dielectric multilayer film is formed on the bottom surface of the electro-optic material 102 . Also, voltage detection device? 1fl14 is a low noise pulse light source 73
a polarizer 104 for extracting a predetermined polarization component from the light beam BM from the polarizer 104, and a micro-polarizer for dividing the light beam having the predetermined polarization component extracted by the polarizer 104 into a large number of light beams B M i j in a grid pattern. Lens array 115
A large number of light beams B M i j in a lattice pattern divided by the microlens array 115 are incident on the electro-optic material 102 as incident light, and the electro-optic material 1
A beam splitter 107 that splits a large number of emitted lights 5Gi- in a lattice pattern reflected by a reflecting mirror 103 formed on the bottom surface of the electro-optic material 102 and outputted from the electro-optic material 102 for voltage detection; Light S
It includes 10 analyzers that allow only light beams of predetermined polarization components to pass among G i j , and a detector 116 into which the emitted light that has passed through the analyzer 109 enters. The microlens array 115 is configured by stacking a plurality of first rod lenses 115A aligned in a specific direction and a plurality of second rod lenses 115B aligned in a direction orthogonal to the first rod lenses. As a result, the light beam is divided into a grid pattern. The detector 116 is composed of a two-dimensional photodetector such as a CCD camera, a photodiode array, or a vidicon camera, or a high-speed response detector such as a streak camera. In the voltage detection device 114 having such a configuration, the electro-optic material 102 has a cross section cut out to a size that covers a plurality of two-dimensional positions of the IC 56, so that voltages at a plurality of two-dimensional positions of the IC 56 can be detected. Therefore, the refractive index of the local portion of the electro-optic material f1102 corresponding to these two-dimensional positions changes. Therefore, a large number of light beams B in a lattice pattern having predetermined polarization components are divided by the microlens array 115.
As M r- travels through the grid section in the electro-optic material 102, these multiple light beams B M ij travel through the grid section in the electro-optic material 102 due to the voltages at the grid positions of the IC 56 directly below the grid section. The polarization state changes due to the change in the refractive index of the shaped portion, and the light is output from the electro-optic material 102 as light. These emitted lights are further applied to an analyzer 109 via a beam splitter 107. Analyzer 109
For example, if the configuration is such that only a light beam with a polarization component perpendicular to the polarization component of the polarizer 104 is passed through, each output light S G i j whose polarization state changes and enters the analyzer 109 is as follows. The analyzer 109 determines the intensity of si
n'C(π/2) -V; -/■o] will be applied to the detector 116 in proportion to. Here Vij is IC
The voltage at 56 two-dimensional grid positions (i, j), VO, is a half-wave voltage. In this way, the intensity of each emitted light changes depending on the change in the refractive index of the local portion of the electro-optic material 102 due to the change in voltage at each grid position of the IC 56. Of all the two-dimensional positions of the object to be measured, only the voltages at the two-dimensional grid positions can be detected simultaneously. In this embodiment, a microlens array 115 is used to create a large number of light beams B M i in a two-dimensional grid pattern.
j, and these light beams are incident on the electro-optic material 102 to detect the voltage at a two-dimensional grid position of the object to be measured. One may wish to detect voltage. In such a case, for example, the microlens array 11
A plate-shaped mask is installed at the rear of 5, and by using this mask only a desired light beam is extracted and made to enter the electro-optic material 102, it is possible to detect the voltage at any two-dimensional position of the object to be measured. can. Further, instead of the microlens array 115, a holographic lens recorded with a hologram so that a radiation beam is focused on a specific two-dimensional portion of the electro-optic material 102 may be used. Also, a spatial light modulator may be used instead of the microlens array. Next, a seventh example of the voltage detection device will be explained with reference to FIG. In the voltage detection device 117 of FIG. 19, the electro-optic material 102 similar to the embodiments of FIGS. 16 and 18 is
56 or the like, or is fixed in contact with the IC 56. This electro-optic material 102 is cut out to a size that covers a plurality of two-dimensional positions of the object to be measured. Further, on the bottom surface of the electro-optic material 102, a reflecting mirror 103 made of metal or a dielectric multilayer film is formed. Further, the voltage detection device 117 includes a low-noise pulse light source 73 that outputs a light beam with a very short pulse width, a variable delay means 118 that variably delays the light beam from the low-noise pulse light source 73, and a variable delay means. 11 expansion optical systems that expand the light beam delayed by the expansion optical system 118 into a two-dimensional spread and make it parallel light; and a polarizer 104 that extracts a predetermined polarization component from the light beam that has been made parallel light by the expansion optical system 119. A parallel light beam having a predetermined polarization component extracted by a polarizer 104 is made incident on the electro-optic material 102, and is reflected by a reflecting mirror 103 formed on the bottom surface of the electro-optic material 102. The light output from the imaging optical system 1 is split for voltage detection.
20, and a phase compensator 121 that adjusts the phase of the light emitted from the imaging optical system 12.
5. An analyzer 109 that allows only a light beam of a predetermined polarization component to pass through the output light whose phase has been adjusted by the phase compensator 121, and a detector 116 that receives the output light that has passed through the analyzer 109. There is. The parallel light incident on the electro-optic material 102 is transmitted through the magnifying optical system 1
19, it has a two-dimensional spread, and is made to be incident on the electro-optical material fl102 at -m with a predetermined spread. Furthermore, since the cross section of the electro-optic material 102 is cut out to a size that covers a plurality of two-dimensional positions of the object to be measured, the collimated light that has uniformly entered the electro-optic material 102 is transmitted to the IC 56 that is the object to be measured. The polarization state changes due to a change in the refractive index of a two-dimensional portion of the electro-optic material 102 corresponding to these two-dimensional positions due to voltages at a plurality of two-dimensional positions,
The electro-optic material 102 outputs the emitted light. That is, the light emitted from the electro-optic material 102 has the same spread as parallel light, and changes in the polarization state of each part reflect the voltage at each two-dimensional position of the object to be measured. The phase compensator 121 adjusts the phase of the emitted light and the analyzer 1
The polarized light component of the emitted light extracted by the polarizer 10
4, the polarization component of the emitted light extracted by the analyzer 109 is set to be the same as the polarization component of the parallel light extracted by the polarizer 104. Or they can be orthogonal. The detector 116 is a two-dimensional detector such as a CCD camera, a photodiode array, or a vidicon camera, and detects the intensity of the light emitted from the analyzer 109 to detect the electro-optic material 10.
The voltage at the two-dimensional position of the object to be measured is simultaneously detected from the two changes in the refractive index. When the low-noise pulsed light source 73 and the two-dimensional detector 116 are used in combination, the voltage at each two-dimensional position of the object to be measured must change periodically in synchronization with the optical pulse. That is, the light beam from the low-noise pulsed light source 73 is split into two by the beam splitter 122, one of which is incident on the variable delay means 118 for sampling measurement, and the other is incident on the detector 123 for photoelectric conversion. The photoelectrically converted signal is sent to the drive circuit 12 via the trigger circuit 124.
5, the object to be measured is operated periodically in synchronization with the optical pulse. The voltage that repeatedly changes in this way is detected by sampling. This sampling is performed by gradually delaying the light beam from the low noise pulsed light source 73 by a variable delay means 118, which is controlled by the computer 111. That is,
After the detector 116 detects the voltage at each two-dimensional position of the IC 56 at a certain timing, the computer 111 processes the voltage at each two-dimensional position at this time, stores it in a memory (not shown), and drives it. The circuit 1.26 is controlled and the variable delay means 115 is driven by one driving cycle FI@126 to delay the light beam from the low-noise pulse light source 73 and slightly delay the sampling timing. This makes it possible to detect temporal changes in voltage at each two-dimensional position of the object to be measured. In the voltage detection device 117 having such a configuration, the phase compensator 121 is adjusted and the analyzer 109! :l: Therefore, the polarization component of the output light to be extracted is made orthogonal to the polarization component of the parallel light extracted by the polarizer 104. This results in
When the polarization state of the emitted light from the electro-optic material 102 is the same as the parallel light incident on the electro-optic material 102 (when no voltage is applied to the electro-optic material 102), the emitted light is prevented from passing through the analyzer 109. Make it. After setting the phase compensator 121 in this way, voltage measurement at the two-dimensional position of the object to be measured is started. The electro-optical material f1102 has a cross section that corresponds to the object to be measured (IC5
6), so that the voltage at each two-dimensional position of the object to be measured causes a local portion of the electro-optic material 102 corresponding to these two-dimensional positions to be cut out. The refractive index of changes. Therefore, the polarization state of parallel light that is not uniformly incident on the electro-optic material 102 changes due to the change in the refractive index of the two-dimensional portion of the electro-optic material 102 corresponding to each two-dimensional position of the object to be measured, and The light is output from the material 102 as emitted light. These emitted lights further enter the phase compensator 121 via the beam splitter 107 and the imaging optical system 120, and the phase is adjusted by the phase compensator 121 and enters the analyzer 109. Since the photon 109 is adjusted to pass only the light beam with a polarization component perpendicular to the polarization component of the polarizer 104,
The intensity of each output light that entered the analyzer 109 is
9, sin' ((π/2) ・Vt-/Vo
:] and is applied to the detector 116. Here, V i J is the voltage at each two-dimensional position (i, j) of the object to be measured, and VO is the half-wavelength voltage. In this way, each emitted light changes depending on the refractive index change of the local part of the electro-optic material 102 due to the voltage change at each two-dimensional position of the object to be measured. The voltage at the two-dimensional position of the object to be measured can be detected simultaneously. When the detector 116 does not detect the voltage at the two-dimensional position of the object to be measured at a certain timing, the result is stored in the memory of the computer 111, and in order to detect the voltage at the next timing, the computer 111 controls the drive circuit 126 to drive the variable delay means 118, delays the light beam from the low-noise pulse light source 73 by a predetermined amount, slightly delays the sampling timing, and repeats the same voltage detection process. Then, the temporal change in voltage at the two-dimensional position of the object to be measured is sampled and measured. The sampling measurement results are stored in the memory of the computer 111, so when the sampling measurement within a predetermined period of time is completed, the computer 111 displays the display 1.
These voltage detection results are displayed on 12, and all processing is completed. In the above-mentioned embodiment, only the voltage at the two-dimensional position of the object to be measured is detected and displayed on the display 112, but it is useful for the user to simultaneously check the wiring shape of the object to be measured, such as an S product circuit. There are cases where it is desired to observe and display the voltage at each two-dimensional position by superimposing it on the observed wiring shape. FIG. 20 shows the eighth voltage detection device that can display the voltage at a two-dimensional position by superimposing it on the wiring shape of the object to be measured.
It is a block diagram showing an example. Note that in FIG. 20, the same parts as in FIG. 19 are denoted by the same reference numerals, and explanations thereof will be omitted. In the voltage detection device 130 shown in FIG. 20, an observation light source 131 that outputs pulsed light or DC light is provided separately from the low-noise pulsed light source 73 in order to observe the wiring shape of an object to be measured such as an IC 56. The wavelength of the light beam output from the observation light source 131 is the same as that of the low-noise pulse light source 73.
The wavelength of the light beam from the low-noise pulsed light source 73 is different from that of the light beam output from the electro-optic material 102.
The light beam from the light source 11 is transmitted through the dielectric multilayer mirror 103A formed on the bottom surface of the dielectric multilayer mirror 103A and is incident on the surface of the object to be measured. The light beam from the observation light source 131 and the light beam from the low-noise pulse light source 73 are switched by a switching means 133 under the control of the computer 111. When observing the shape, a light beam from the observation light source 131 is selected and made to enter the object to be measured via the electro-optic material 102, while when detecting the voltage at the two-dimensional position of the object. The light beam from the low-noise pulsed light source 73 is selected and made to enter the electro-optic material f1102. Further, the phase compensator 121 is adjusted by the computer 111, and when observing the wiring shape of the object to be measured, the analyzer 109 passes the emitted light having the same polarization component as the polarization component of the polarizer 104. When detecting the voltage at the two-dimensional position of the object to be measured, it is adjusted so that the emitted light having a polarization component orthogonal to the polarization component of the analyzer 109 or polarizer 104 passes through. It has become. In the voltage detection device 130 having such a configuration, the computer 111 first observes the wiring shape of the object to be measured.
The switching means 133 is controlled so that the light beam from the observation light source 131 is incident on the surface of the object to be measured as parallel light, and the analyzer 109 passes the emitted light having the same polarization component as the polarization component of the polarizer 104. Adjust the phase compensator 121. As a result, the light beam from the observation light source 131 enters the electro-optic material 102 as parallel light via the variable delay means 118, the magnifying optical system 119, the polarizer 104, and the beam splitter 107, and further enters the dielectric multilayer mirror 103A. and enters the surface of the IC 56, which is the object to be measured. A portion of the parallel light incident on the surface of the object to be measured is reflected by the wiring shape and material on the surface of the object to be measured, returns to the dielectric multilayer mirror 103A, the electro-optic material 102, and passes through the beam splitter 107 and the imaging optical system. 120, and enters the analyzer 109 as output light via the phase compensator 121. By the way, the phase compensator 121
Since the analyzer 109 is adjusted to pass the emitted light having the same polarization component as the polarization component of the polarizer 104,
The output light that entered the analyzer 109 is the mother analyzer 109.
The emitted light that passes through the detector 116 and is applied to a two-dimensional detector 116 such as a COD camera has visible image information of the wiring shape on the surface of the object to be measured. Now, by photoelectrically converting this, visible image data of the wiring shape can be obtained. This visible image data is sent to computer 111 and stored in computer 111's memory (not shown). After obtaining visible image data of the wiring shape of the object to be measured in this manner, the computer 111 initializes the variable delay means 118 and controls the switching means 133 so that the light beam from the low-noise pulse light source 73 is The electro-optic material 102 is made to enter parallel light, and the analyzer 109 is made to enter the polarizer 1.
The phase compensator 121 is adjusted so as to pass the emitted light of the polarization component orthogonal to the polarization component of 04, and the voltage at the two-dimensional position of the object to be measured is simultaneously detected. At this time, the light beam from the low-noise pulsed light source 73 enters the electro-optic material 102 as parallel light, and then is reflected by the dielectric multilayer mirror 103A, and the polarization state changes as the refractive index of the electro-optic material 102 changes. The emitted light enters the phase compensator 121 and the analyzer 109 as emitted light. The analyzer 109 allows only the emitted light of a predetermined polarized component to pass through and enter the two-dimensional pressure detector 116 . The detector 116 samples and simultaneously detects the voltage at the two-dimensional position of the object to be measured at the timing set by the variable delay means 118. The voltage detection result at one timing is displayed on the computer 11.
1 and stored in memory. Thereafter, the voltage detection results at the two-dimensional position of the object to be measured, which are sampled at one timing, are displayed on the display 112 by superimposing them on the visible image data of the wiring shape of the object to be measured that has been previously stored in the memory.
to be displayed.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of the basic configuration of a low-noise pulsed light source using a laser diode (LD) according to the present invention. FIG. 2 is a circuit diagram showing the configuration of a first embodiment of the present invention. 2. FIG. 3 is a circuit diagram showing an example of a specific configuration of the first embodiment. FIG. 4 is a block diagram showing the configuration of a second embodiment of the present invention. A diagram for explaining the principle of the fourth embodiment, FIG. 6 is a block diagram showing the configuration of an example of an E-0 sampling device using the fourth embodiment, and FIG. 7 is a diagram showing the problems of the prior art. FIG. 8 is a block diagram showing the configuration of an example of a transmittance measuring device for explaining the above. FIG. 9 is a block diagram showing an example of the configuration of the LD pulse light source used in the device of FIG. The figure shows an LD in a conventional example and an embodiment of the present invention.
A diagram showing a comparison of the frequency characteristics of the noise level of pulsed light; FIG. 10 is a block diagram showing an example of the noise component measuring device used to obtain the data in FIG. 9; FIG.
A sectional view including a partial block diagram showing the first embodiment of the voltage detection device according to the present invention, FIG. 12 and FIG.
and a sectional view showing the third embodiment; FIG. 14 is a line section for explaining the voltage dependence of the emitted light intensity; FIG. 15 is a front view showing the main parts of the fourth embodiment of the voltage detection device. , FIG. 16 is a block diagram showing the fifth embodiment of the voltage detection device, FIG. 17 is a diagram for explaining the operation method in the same embodiment, and FIG. 18 is a block diagram showing the sixth embodiment of the voltage detection device. The perspective view of the embodiment, FIGS. 19 and 20, show the seventh and eighth voltage detection devices.
It is a block diagram showing an example. DESCRIPTION OF SYMBOLS 10... Sample, 38... Laser diode (LD), 40... Electric pulse generator, 41... Stabilized electric pulse generator, 42... Photodetector- 43... Vinphoto Diode (PIN-PD), 4
4... Stabilized current modulation circuit, 46.48.54... Amplifier, 50... Package, 52... Current source, 56.100... DUT, 62... Lock-in amplifier , 70.92.96.101.114. 117.130... Voltage detection device, 72.90.93.97... Optical probe, 72A, 7
2B, 96A, 102... Electro-optic material, 73...
Low noise pulse light source, 82... Conductive electrode, 83.98.103.103A... Reflector, 91...
・λ/2 plate, 94.95.99... Transparent electrode, 97A... Tip, 105.106... Movable mirror 110.116... Detector, 5... Microlens array 8. ...Variable delay means, 1.. Phase compensator, 1.. Observation light source.

Claims (19)

[Claims] (1) A laser diode that repeatedly generates pulsed light, an electric pulse generator that drives the laser diode, a current source that supplies a bias current to the laser diode, and a photodetector that detects a portion of the light emitted from the laser diode. The bias current of the current source is modulated and controlled over a wide frequency band according to the output signal of the photodetector so that the light intensity of the pulsed light is constant and the light intensity noise is reduced. A low-noise pulsed light source using a laser diode. (2) a laser diode that repeatedly generates pulsed light; an electric pulse generator that drives the laser diode; a current source that supplies a bias current to the laser diode; and a photodetector that detects a portion of the light emitted from the laser diode. In accordance with the output signal of the photodetector, the amplitude of the pulse signal generated by the electric pulse generator is widened so that the light intensity of the pulsed light is constant and the light intensity noise is reduced. A low-noise pulsed light source using a laser diode that is characterized by modulation control over a frequency band. (3) a laser diode that repeatedly generates pulsed light; an electric pulse generator that drives the laser diode; a current source that supplies a bias current to the laser diode; and a photodetector that detects a portion of the light emitted from the laser diode. In accordance with the output signal of the photodetector, the bias current of the current source is adjusted in a band below a predetermined frequency so that the light intensity of the pulsed light is constant and the light intensity noise is reduced. A low-noise pulsed light source using a laser diode, characterized in that modulation is controlled, and in a band above a predetermined frequency, the amplitude of a pulse signal generated by the electric pulse generator is modulated and controlled. (4) A low-noise pulse light source using a laser diode according to any one of claims 1 to 3, wherein the electric pulse generator uses a step recovery diode. (5) In any one of claims 1 to 3, the photodetector is assembled into a set with a laser diode in the same package. Noise pulse light source. (6) A low-noise device using a laser diode according to any one of claims 1 to 3, characterized in that the time constant of the feedback system for detecting and controlling light is longer than the repetition period of the pulsed light. Pulsed light source. (7) In claim 6, the frequency characteristic of the feedback system has a peak to reduce noise in a specific frequency range, and the frequency of the reference signal of the lock-in amplifier used in the measurement system is a frequency within the specific frequency range. A low-noise pulsed light source using a laser diode, which is characterized by having the following characteristics. (8) In a type of voltage detection device using an electro-optic material whose refractive index changes depending on the voltage at a predetermined portion of the object to be measured, a first electro-optic material that is affected by the voltage at a predetermined portion of the object to be measured; a second electro-optic material arranged to compensate for a phase difference due to natural birefringence of the first electro-optic material; and a low-noise pulsed light source according to claim 1, 2 or 3.
The second electro-optic material is formed of the same material as the first electro-optic material, has the same length in the optical axis direction as the first electro-optic material, and is aligned along the optical axis. ,
A voltage detection device characterized in that pulsed light from the low-noise pulsed light source is made incident on the first and second electro-optic materials along the optical axis. (9) In claim 8, the second electro-optic material:
A voltage detection device characterized in that the optical axis thereof is arranged to be perpendicular to the optical axis of the first electro-optic material. (10) In claim 8, the second electro-optic material is arranged such that its optical axis is parallel to the optical axis of the first electro-optic material, and the second electro-optic material and the A voltage detection device characterized in that means for rotating the polarization component of light by 90° is provided between the first electro-optic material and the first electro-optic material. (11) In a type of voltage detection device using an electro-optic material whose refractive index changes depending on the voltage at a predetermined portion of the object to be measured, a first electro-optic material that is affected by the voltage at a predetermined portion of the object to be measured; a second electro-optic material arranged to compensate for a phase difference due to natural birefringence of the first electro-optic material; and between the first electro-optic material and the second electro-optic material. a first transparent electrode provided;
a second transparent electrode provided on the side opposite to the side on which the first transparent electrode is provided of the electro-optic material; and a pulse along the optical axis of the first and second electro-optic materials. The low-noise pulsed light source according to claim 1, 2 or 3, which inputs light;
A voltage detection device comprising: (12) In claim 11, the first transparent electrode is held at ground potential, and the second transparent electrode is provided with a DC component removed from the polarization state of the light emitted from the first electro-optic material. A voltage detection device characterized in that a voltage is applied so that emitted light is output from the second electro-optic material. (13) In a type of voltage detection device using an electro-optic material whose refractive index changes depending on the voltage at a predetermined portion of the object to be measured, the electro-optic material is positioned at a predetermined position within the optical probe, and the electro-optic material is positioned at a predetermined position within the optical probe. A reflecting means for reflecting a light beam incident along the central axis of the optical probe is provided at the tip of the optical material, and a reflecting means is provided on the opposite side of the electro-optic material from the side where the reflecting means is provided. A voltage detection device comprising a transparent electrode, and wherein the light beam is pulsed light emitted from the low-noise pulsed light source according to claim 1, 2, or 3. (14) The voltage detection device according to claim 13, wherein the transparent electrode is set so that its surface is perpendicular to the central axis of the optical probe. (15) A voltage detection device of a type using an electro-optic material whose refractive index changes when a voltage is applied, comprising the low-noise pulsed light source of claim 1, 2 or 3, wherein the electro-optic material is The electro-optical material is positioned so as to cover a plurality of measurement positions of the object to be measured, and pulsed light from the low-noise pulsed light source is incident on each part of the electro-optic material corresponding to the plurality of measurement positions of the object to be measured. Each of the portions of the electro-optic material is scanned, and voltages at a plurality of measurement positions of the object to be measured are detected based on changes in the polarization state of the light emitted from each portion of the electro-optic material. A voltage detection device characterized by: (16) In a type of voltage detection device using an electro-optic material whose refractive index changes when a voltage is applied, the electro-optic material is arranged so as to cover a plurality of positions of the object to be measured whose voltage is to be detected. The light beam from the low-noise pulsed light source according to claim 1, 2 or 3 is divided into a large number of desired patterns on each specific portion of the electro-optic material which is positioned at A voltage detection device characterized in that each incident light is incident thereon, and a change in the polarization state of the light emitted from the specific portion of the electro-optic material is detected by a detector. (17) In claim 16, the light beam from the light source is
1. A voltage detection device characterized by being split into a large number of incident lights in a grid pattern by a microlens array. (18) A voltage detection device using an electro-optic material whose refractive index changes when a voltage is applied, comprising the low-noise pulsed light source of claim 1, 2 or 3, wherein the electro-optic material is used for detecting voltage. The electro-optic material is positioned so as to cover a plurality of two-dimensional positions of the object to be measured, and each two-dimensional portion of the electro-optic material corresponding to the plurality of two-dimensional positions of the object to be measured is provided with the low noise A light beam from a pulsed light source is uniformly incident as parallel light, and a change in the polarization state of the light emitted from the plurality of two-dimensional parts of the electro-optic material is detected by a detector. A voltage detection device characterized by: (19) A voltage detection device using an electro-optic material whose refractive index changes when a voltage is applied, comprising the low-noise pulse light source of claim 1, 2 or 3, wherein the electro-optic material is used for detecting voltage. The electro-optic material is positioned so as to cover a plurality of two-dimensional positions of the object to be measured, and each two-dimensional portion of the electro-optic material corresponding to the plurality of two-dimensional positions of the object to be measured is provided with the low noise A light beam with a short pulse width from a pulsed light source is uniformly incident as parallel light, and a change in the polarization state of the light emitted from the plurality of two-dimensional parts of the electro-optic material is detected by a detector. and an observation light source that outputs a light beam of a different wavelength from that of the low-noise pulse light source in order to observe the wiring shape of the object to be measured, and a light beam from the observation light source and the low-noise pulse light source. a switching means for switching a light beam from a light source to enter the electro-optical material; and a switching means for switching a light beam from a light source to enter the electro-optic material; and a phase compensation means for adjusting the voltage at the two-dimensional position of the object to be measured based on a change in the polarization state of the emitted light, which is perpendicular to the wiring shape of the object to be measured observed by the detector. and variable delay means for shifting the timing of incidence of the light beam from the low-noise pulsed light source onto the electro-optic material in order to sample and measure the voltage change at the two-dimensional position of the object to be measured. A voltage detection device characterized by: