JPH0720300A - Imaging device - Google Patents

Abstract

PURPOSE:To provide a high resolution miniature imaging device. CONSTITUTION:A transparent electrode 51 passing a specific electromagnetic wave 13 and a photoconductive film 52 formed thereon constitutes a light receiving member 31. A scanning means 34 causes a conductive probe 32 to scan on the photoconductive film 52 while touching thereon and a current measuring means 36 measures the current flowing between the transparent electrode 51 and the probe 32. An intensity distribution detecting means 37 determines the intensity distribution of electromagnetic wave on the light receiving member 31 based on the values of current flowing between the transparent electrode 51 and the probe 32 at the position of the probe 32 on the light receiving member 31 and at the measuring position of the current measuring means 36.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus used for an apparatus used for a light focusing test, an X-ray microscope, an X-ray optical apparatus such as an X-ray reduction exposure.

[0002]

2. Description of the Related Art A photoconductive type image pickup tube (vidicon type image pickup tube) utilizing photoelectric conversion is known as a type of image pickup device. This photoconductive type image pickup tube is a film (hereinafter, referred to as a transparent electrode and a photoconductive body formed on the electrode for performing photoelectric conversion).
(Referred to as a photoconductive film). The photoconductive film has almost no conductivity when it is not irradiated with light (electromagnetic wave) (resistivity is 10 ¹² Ωcm or more), but it is conductive so that its resistance decreases when it is irradiated with light. . For such a photoconductive film, various different materials are used depending on the wavelengths of light from infrared light to X-rays. For example, antimony trisulfide,
Materials such as cadmium selenide, silicon, amorphous selenium, and lead oxide are used.

An image pickup process of the photoconductive type image pickup tube will be described below. The transparent electrode is set to a positive potential (several tens V) with respect to the cathode (for example, the filament of the electron gun).
In this state, when the photoconductive film on the side opposite to the transparent electrode is irradiated with an electron beam, the surface of the photoconductive film is negatively charged. When the irradiation surface of the electron beam is lowered to the cathode potential (0 V), electrons cannot enter the photoconductive film any more. This time,
A potential difference of about several tens of V is generated between both surfaces (the surface on the transparent electrode side and the surface on the cathode side) of the photoconductive film. When the photoconductive film is irradiated with light through the transparent electrode, the resistance of each part of the photoconductive film corresponding to the pixel changes according to the intensity of the incident light, and a photocurrent due to photoelectric conversion flows. Regarding one pixel of the photoconductive film, this pixel constitutes an equivalent circuit having a capacitor and a resistor. And when looking at this equivalent circuit,
When the pixel is irradiated with the electron beam, the capacitor is charged, and the potential of the surface of the photoconductive film drops to the potential of the cathode. On the other hand, when the electron beam is not irradiated, the capacitor is discharged. At this time, since the resistance changes depending on the amount of light applied, bright pixels are discharged quickly and the surface potential is increased, and dark pixels are hardly discharged and the potential is slightly increased. When scanning this electron beam and irradiating this pixel with a beam, the surface potential is 0 V.
Go down to. At that time, the electrons flow into the photoconductive film to generate a current. Since this current is proportional to the photocurrent, an output (signal) corresponding to the amount of incident light can be taken out. Since photoelectric conversion does not occur in a portion not irradiated with light, electrons cannot flow into the photoconductive film and are absorbed by the grid in front of it, so that no signal can be obtained. In this way, the presence / absence of light incident can be known by the presence / absence of a current (signal), and the intensity of light (amount of light) can be known by detecting the value of the current. In this way, by irradiating the electron beam, it is possible to obtain an output corresponding to the light amount of the incident light, and thus an image of the light is detected.

[0004]

The conventional photoconductive type image pickup tube irradiates the photoconductive film with the beam emitted from the electron gun. However, since the size of a normal electron gun is relatively large, this photoconductive film is used. The conductive type image pickup tube had a length of about 100 to 200 mm. However, when such an image pickup tube is used as an image pickup means in an observation device such as a microscope, it is advantageous to reduce the size because the degree of freedom in arrangement of the device is increased.
It is possible to reduce the weight and size of the device incorporated as the imaging means. Therefore, there has been a demand for a downsized image pickup means without impairing the resolution. Further, it is preferable that the image pickup means has as high a resolution (spatial resolution) as possible. In the photoconductive type image pickup tube, the photoconductive film is scanned by the electron beam,
Since the image of the received light is obtained based on the irradiation position of the beam and the current value detected at this position, the resolution depends on the beam diameter of the electron beam. In the conventional photoconductive type image pickup tube, since the beam diameter of the electron gun is on the order of several tens of microns, the resolution of the image pickup tube is also on the order of several tens of microns. To improve the resolution, the beam diameter may be reduced, but for that purpose, it is necessary to improve the electron gun by improving the performance of the electromagnetic lens that narrows the beam. However, such an improvement inevitably leads to an increase in the size of the electron gun portion, which causes a problem in that the size of the image pickup means itself also increases. The present invention has been made in view of such a problem, and an object thereof is to provide a compact and high-resolution image pickup apparatus.

[0005]

To achieve the above object, in the present invention, a light receiving member having a transparent electrode for transmitting a predetermined electromagnetic wave and a photoconductive film formed on the electrode, and a conductive probe. Scanning means for scanning the photoconductive film of the light receiving member in contact with the photoconductive film of the light receiving member, current measuring means for measuring a current flowing between the transparent electrode and the probe, Based on the position of the probe on the light receiving member and the value of the current flowing between the transparent electrode and the probe at the position measured by the current measuring means, the intensity of the electromagnetic wave applied to the light receiving member. The image pickup device is constituted by the intensity distribution detecting means for obtaining the distribution (claim 1). Further, the probe is installed on a flexible body having conductivity so that the contact pressure between the probe and the photoconductive film at the time of scanning of the probe can be maintained at a predetermined value. An irradiation means for irradiating light, a light receiving means for receiving the light reflected by the flexible body, and a moving means for moving the flexible body toward the light receiving member are provided (claim 2).

[0006]

In the present invention, when reading an image of light (electromagnetic wave), a sharp probe having conductivity is brought into contact with the photoconductive film for scanning instead of scanning the photoconductive film with an electron beam.
Then, the current (or voltage) flowing between the probe and the film is measured, and the measured value and the intensity distribution of the light (electromagnetic wave) emitted from the measurement position are obtained and used as the light image (image). . According to the invention, the spatial resolution depends on the tip radius of the probe. Atomic force microscope (AFM
), The tip radius of the probe can be set to 0.01 to 0.1 μm. Therefore, the image pickup apparatus of the present invention can obtain a spatial resolution on the order of submicrons, and the resolution is improved as compared with the conventional case. FIG. 2 is a schematic configuration diagram illustrating the imaging principle of the present invention. The operation of the present invention will be described below with reference to FIG.

Light receiving member (hereinafter referred to as target) 20
Reference numeral 1 denotes a face plate 202 having a sufficient transmittance for light to be observed, a transparent electrode 203 formed on one surface of the plate, and a film (photoconductor formed on the electrode ( Photoconductive film) 204.
The structure of the target is the same as that of a conventional vidicon. Before imaging, the power source 206 first applies a positive voltage to the transparent electrode 203. When applying the voltage,
The probe 205 is set to have a negative potential with respect to the transparent electrode 203 using the power supply 206, and scanning is performed while the probe 205 is in contact with the surface of the photoconductive film 204. As a result, electrons are injected into the surface of the photoconductive film 204, and a potential difference is generated between both surfaces (the surface on the transparent electrode side and the surface on the probe side) of the conductive film 204. At this time, when light (electromagnetic wave) 207 is irradiated from the face plate 202 side, an internal photoelectric effect is generated in the photoconductive film 204, light is absorbed, and movable electrons and holes are formed. The electrons move in the photoconductive film 204 and enter the transparent electrode 203. On the other hand, the holes move to the side opposite to the transparent electrode 203 and move to the photoconductive film 204.
Combines with surface electrons. As a result, the charges on the surface of the photoconductive film 204 on the face plate 202 side are discharged. When the light 207 further enters, the amount of discharge increases and the potential rises.

In this state, when the probe 205, which is set to have a negative potential with respect to the transparent electrode 203 by the power source 206, is brought into contact with the surface of the photoconductive film 204 to scan again, it corresponds to a discharged pixel. In the part of the photoconductive film 204, electrons are injected into the photoconductive film 204 through the probe 205. As a result, a current flows into the capacitor composed of the transparent electrode 203 and the probe 205. Further, the voltage detected at the signal output terminal 209 drops due to this current. The value of the current measured by the current measuring unit 208 or the amount of voltage drop measured at the signal output terminal 209 is proportional to the amount of charge injected into the surface of the photoconductive film 204. That is, the current value or the amount of drop increases as the amount of electric charges discharged by light irradiation increases, and decreases as the amount of discharged electric charges decreases. Therefore, by measuring at least one of the current value and the voltage drop amount (hereinafter, both are referred to as “measured value”), the intensity of the X-ray incident near the contact position can be known. Therefore, while the light 207 is being irradiated, the probe 205 is brought into contact with the photoconductive film 204 for scanning, and the contact point between the probe 205 and the photoconductive film 204 and the measurement value measured at this contact point The intensity distribution of the incident light 207 can be obtained by corresponding to This intensity distribution corresponds to information (image) included in the light 207 that has entered the target 201.

As the structure and material of the target used in the present invention, those used in a photoconductive type image pickup tube such as a vidicon can be used. It can be appropriately set according to the wavelength of the light (electromagnetic wave) used. Note that the photoconductive film 204
The positive charges accumulated in the liquid crystal tend to spread due to diffusion, but there is no particular problem when scanning the microelectrodes at a speed of video rate (1/30 sec / screen).

[0010]

1 is a schematic view showing the structure of an X-ray microscope which is an embodiment of the present invention. This X-ray microscope includes an X-ray source 11, a sample holder 12 for holding a sample (not shown), and an X
Illumination zone plate 14 for condensing X-rays 13 emitted from a radiation source 11 on the sample, pinholes 15 arranged between the illumination zone plate 14 and the sample holder 12, an imaging means 30, and the sample. The imaging means 30 for the X-ray 13
And an image forming zone plate 16 for condensing (forming an image). Further, a vacuum container for maintaining the optical path of the X-rays 13 at a predetermined degree of vacuum and an exhaust means (both not shown) are provided.

The image pickup means 30 includes a target 31 and a probe 3.
2, a flexible cantilever 33 having a probe 32 at its tip, an actuator 34, a voltage applying means 35,
A current measuring unit 36, a control unit 37, and a CRT 38 are provided. In this embodiment, since the image included in the X-ray is captured, the structure of the target 31 corresponds to the X-ray.

The target 31 is composed of a Be (beryllium) plate 51 having a thickness of 0.3 mm and a photoconductive film 52 made of PbO (lead oxide) deposited on the Be plate 51. The photoconductive film 52 may have a thickness of 0.1 to 1 μm.
In place of PbO, antimony trisulfide, cadmium selenide, silicon, amorphous selenium, etc. may be used. The Be plate 51 is a metal that transmits X-rays and has two functions of a face plate and a transparent electrode in the target 31. In addition to Be, Al or the like can be used.
The target 31 is installed such that the Be plate 51 is located on the incident side of the X-ray 13.

The probe 32 and the cantilever 33 are integrally formed as shown in FIG. And these probe 3
2 and the lever 33 include a core body 401 made of SiN (silicon nitride), a film 403 made of a NiCr alloy having a thickness of 1 nm formed on the surface of the core body 401, and a NiCr alloy film 40.
3 and Au film 402 having a thickness of 390 nm. The core body 401 was manufactured by using the lithography technique as in the case of the cantilever and the probe used in the atomic force microscope (AFM). In addition to SiN, SiO2 is used for the core 401.
₂ (silicon dioxide) can also be used. The NiCr alloy film 403 is provided in order to improve the adhesiveness between the core body 401 and the Au film 402, and may be omitted if a conductive substance having good adhesiveness to the core body is used. Both the NiCr alloy film 403 and the Au film 402 were formed by vapor deposition. The cantilever 33 was manufactured to have a length of 300 μm and a spring constant of 0.1 N / m. In addition, the probe 3
No. 2 was manufactured so that its tip radius was 0.01 to 0.1 μm. The cantilever 33 is attached to the actuator 34.

The voltage applying means 35 comprises a probe 32 and a Be plate 51.
A predetermined voltage is applied between and. If the value of the current flowing between the probe 32 and the Be plate 51 is large, the probe 32 may be damaged, generate heat, etc., and the signal detection accuracy may decrease. To prevent this, the value of the current flowing between the probe 32 and the Be plate 51 may be reduced. In this embodiment, the voltage applied by the voltage applying means 35 is adjusted so that the value of the flowing current is within the range of nA to μA.

The current measuring means 36 comprises a Be plate 51 and a probe 32.
Measure the current flowing between and. The amount of voltage drop may be measured instead of measuring the current. In that case, the intensity of the X-ray is obtained by measuring the amount of voltage drop from the value of the voltage applied by the voltage applying means 35 before the irradiation of the light (X-ray). The actuator 34 moves the cantilever 33 in the XYZ directions. The actuator 34 of this embodiment has a structure called a tube scanner type as shown in FIG.
In this actuator 34, electrodes 301a, 301b for piezoelectric elements for X-direction scanning and electrodes 302a, 302b for piezoelectric elements for Y-direction scanning are provided on the outer peripheral surface of a cylindrical piezoelectric ceramic 300, respectively, in the X-direction.
It is provided so as to face each other in the Y direction. The electrodes 301a, 301 are formed on the inner peripheral surface of the piezoelectric ceramics 300.
A common electrode 303 is provided for b, 302a, 302b. When scanning in the X and Y directions, potentials having the same size but different signs are applied between the electrodes in the respective directions. When moving in the Z direction, either positive or negative voltage is set, and this voltage is equally applied between each electrode on the outer peripheral surfaces of all X and Y and the common electrode 303, so that the element is moved. Expands and contracts in the Z direction. In this embodiment,
By the actuator 34, the photoconductive film 52 and the probe 32
The probe 32 is moved with respect to the photoconductive film 52 (target 31) while being in contact with. This actuator 3
4, the probe 32 can be scanned in an arbitrary range in the area where the target 31 is irradiated with the X-ray 13. The moving speed and the scanning range for scanning the probe 32 can be set by changing the frequency and amplitude of the scanning signal (triangular wave) sent from the control means 37 to the actuator 34.

The control means 37 drives and controls the actuator 34 in a predetermined direction, and the position of the probe 32 on the target 31 (photoconductive film 52) and the measurement result by the current measuring means 36 at this position. The intensity distribution of the X-ray 13 with which the target 31 is irradiated is determined in accordance with C
The RT 38 displays the obtained intensity distribution on the screen as an image (sample image) included in the X-ray 13.

The image pickup means 30 of this embodiment is provided with a probe displacement measuring system for measuring the degree of bending of the cantilever 33 (displacement of the probe 32), and the probe 32 is kept at a constant pressure (0.1 μm).
(About N) so that the surface of the photoconductive film 52 can be contacted. The contact pressure between the probe and the photoconductive film is preferably 0.1 μN or less so that the photoconductive film 52 is not damaged by the scanning of the probe 32. The probe displacement measuring system includes a reflecting surface 33 provided near the probe 32 in the cantilever 33.
A laser light source (not shown) for irradiating a with a laser beam as the measuring light 61, a light detecting means 62 for detecting the measuring light 61 reflected by the reflecting surface a33, and the light detecting means 6
The deflection amount (displacement amount) of the cantilever 33 is detected from the output of No. 2, and the actuator 34 is controlled via the control unit 37 so that the deflection amount becomes a predetermined amount (the output of the light detection unit 62 becomes a certain value). Is constituted by Z-direction control means 63 having a feedback amplifier for driving the Z-direction in the Z-direction. A two-divided photodetector was used as the light detection means 62. In this displacement measuring system, the measuring light 6
1 irradiates the reflecting surface 33a of the probe 32 with the reflected light
The displacement of the probe 32 can be detected from the differential output received by the split photodetector (light detection means) 62.
The amount of displacement detected here corresponds to the contact pressure between the probe 32 and the photoconductive film 52. Therefore, if feedback control is performed so that the displacement becomes constant, the contact pressure becomes constant, and the probe 32 and the light The contact state with the conductive film 52 can be stabilized. It is desirable that the displacement measuring system has a resolution of about sub-nanometer. As such a measuring system, in addition to the configuration in which the reflecting surface 33a of the cantilever 33 used in the present embodiment is irradiated with the measuring light 62, the light irradiating the reflecting surface 33a and the reflected light are made to interfere with each other and the probe tip is used. A structure for measuring the displacement of 32, or a probe of STM (scanning tunneling microscope) is arranged on the back surface of the lever 33, and the probe of this STM and the lever 33 are arranged.
It is possible to use a configuration or the like in which the displacement is measured by measuring the tunnel current flowing between and. In this probe displacement measuring system, the probe 32 is constantly applied with a constant force during scanning.
It need not be provided if it can be kept in contact with the surface. However, the provision of this displacement measurement system has an advantage that it is possible to prevent the photoconductive film 52 and the probe 32 from colliding and being damaged when they are brought into contact with each other.

The imaging process by the X-ray microscope of this embodiment will be described below. First, a sample (not shown) to be observed is stored in the sample holder 12. Next, the inside of the vacuum container (not shown) is evacuated using the evacuation means so that the optical path of the X-rays 13 has a predetermined degree of vacuum. In the image pickup means 30,
The cantilever 33 is moved in the Z direction by driving the actuator 34, and the probe 32 is moved to the photoconductive film 5 of the target 31.
2 Contact the surface. At that time, it is detected that the probe 32 is in contact with the photoconductive film 52 using the probe displacement measuring system,
The probe 32 was further moved to the target 31 side by about 5 μm from the contacted position so that a force of about 0.1 μN was applied between the probe 32 and the photoconductive film 52. After that, the probe 32 is applied to the Be plate 51 by using the voltage applying means 35 to several tens of mV
A voltage that reduces the voltage by several volts is applied, and the actuator 34 is driven by the control means 37 to scan the probe 32 on the surface of the photoconductive film 52. Thereby, the photoconductive film 5
A predetermined potential difference is generated between both surfaces of No. 2 (the surface on the Be plate 51 side and the surface on the probe 32 side). Then, in this state, the X-ray 13 is emitted from the X-ray source 11.

The X-ray 13 emitted from the X-ray source 11 is condensed by the illumination zone plate 14, passes through the pinhole 15 and is monochromatic, and illuminates the sample held in the sample holder 12. The X-rays 13 that diverge after passing through the sample are collected by the imaging zone plate 16 and are collected by the target 31.
It is incident on the (Be plate 51). The incident X-ray 13 includes image information reflecting the structure of the sample as the X-ray intensity distribution. X-ray 13 target 31 (Be plate 51)
The actuator 3 is controlled by the control means 37 in a state where the actuator 3 is illuminated.
Drive 4 Since the cantilever 33 moves in a predetermined direction by driving the actuator 34, the probe 32 provided at the tip of the lever 33 scans the surface of the photoconductive film 52. The scanning area of the probe 32 is previously controlled by the control means 3.
7, the actuator 34 moves the cantilever 33 based on this setting so that the probe 32 scans within a predetermined area. Although not shown in FIG. 1, the actuator 34 output from the control means 37
It is assumed that the drive signal of (4) is D / A converted, amplified, and then input to the actuator 34. Current measuring means 36
Measures the current value flowing between the probe 32 and the Be plate 51 at the scanning position (contact position) on the photoconductive film 52 by the probe 32, and outputs the result to the control means 37. It is assumed that the signal indicating the current value is amplified by a preamplifier (not shown) and then A / D by an A / D converter (not shown) before being input to the control means 37. The control means 37
The current value input from the current measuring means 36 and the probe 3 in the target 31 (photoconductive film 52) where this value was measured
X-rays 13 irradiated on the target 31 from the position 2
Intensity distribution is obtained, and the result is output to the CRT 38.
The CRT 38 displays the intensity distribution of the X-ray 13 sent from the control means 37 on the screen in gray scale as an image of the sample contained in the X-ray 13.

During scanning of the probe at the time of imaging, the probe displacement measuring system controls the deflection amount of the cantilever 33 to be constant, so that the probe 32 always has a constant contact pressure. You may make it contact with. However, since the laser light is emitted to the reflecting surface 33a of the cantilever 33 as the measurement light 61, it is necessary to take care so that the laser light does not affect the measurement of the intensity distribution of the X-ray 13 with which the target 31 is irradiated. .

The image pickup means 30 in this embodiment has a maximum length of about 25 mm, which is smaller than the average length (100 to 200 mm) of the conventional vidicon. Therefore, the X-ray microscope itself incorporating the image pickup means 30 could be downsized. Further, a spatial resolution on the order of submicrons was obtained, and an image could be observed without impairing the resolution determined by the wavelength of X-rays.

[0022]

As described above, according to the image pickup apparatus of the present invention, it is possible to obtain a higher spatial resolution than that of a photoconductive type image pickup tube using an electron beam. In addition, the device can be downsized. Therefore, as compared with the conventional photoconductive type image pickup tube, it is possible to provide an image pickup device which has a high resolution and is miniaturized.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an X-ray microscope showing an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a configuration of an image pickup means used in this embodiment.

FIG. 3 is a schematic perspective view showing the configuration of the actuator of this embodiment.

FIG. 4 is a schematic sectional view showing the structure of a cantilever.

[Explanation of symbols for main parts]

 13 X-ray (electromagnetic wave) 30 Imaging means 31 Target 32 Probe 33 Cantilever 34 Actuator 35 Voltage applying means 36 Current measuring means 37 Control means (intensity distribution detecting means) 38 CRT 51 Berium plate 52 Photoconductive film 61 Measuring light 62 Optical detection Means 63 Z-direction control means 201 Photoconductive target 202 Face plate 203 Transparent electrode 204 Photoconductive film 205 Probe 206 Power source 207 Light (electromagnetic wave) 208 Current measuring means 209 Signal output terminal

Claims (2)

[Claims] 1. A light receiving member having a transparent electrode that transmits a predetermined electromagnetic wave and a photoconductive film formed on the electrode, a conductive probe, and the probe as a photoconductive film of the light receiving member. Scanning means for scanning the photoconductive film in a contact state,
Current measuring means for measuring a current flowing between the transparent electrode and the probe, and the position of the probe on the light receiving member and the transparent electrode and the probe at the position measured by the current measuring means. An image pickup device, comprising: an intensity distribution detecting unit that obtains an intensity distribution of the electromagnetic wave with which the light receiving member is irradiated, based on a value of a current flowing therebetween. 2. The imaging device according to claim 1, wherein the probe is provided with a conductive flexible body, an irradiation unit that irradiates the flexible body with light, and light reflected by the flexible body. An image pickup apparatus comprising: a light receiving unit that receives light and a moving unit that moves the flexible body toward the light receiving member.