JPH0438325B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention scans a sample to be observed two-dimensionally with a light beam focused into a minute spot, and uses reflected light or transmitted light from the sample. The present invention relates to a scanning microscope imaging device that captures images.

(Prior Art) A scanning microscope device has been put into practical use that images a sample by two-dimensionally scanning the sample to be observed with a light beam focused into a minute spot. In this conventional microscope device, light from a laser light source is deflected at high speed in the main scanning direction by a first deflection mirror consisting of a galvanometer mirror, and is deflected at low speed in the sub-scanning direction by a second deflection mirror before being directed to the objective lens. It is incident. This scanning beam is focused into a minute spot by an objective lens and is incident on the sample. Therefore, the sample is two-dimensionally scanned by a light beam focused into a minute spot, and the reflected light from the sample is received by the objective lens, passes through the second and first deflection mirrors again, and then is converted into a photographic image. incident and converted into an electrical signal. This known scanning microscope device is configured to obtain optical information from a sample as an electrical signal, so it is possible to electrically adjust the image brightness, contrast, etc., and the sample can be observed on a monitor, making it suitable for a wide range of applications. It is equipped with

(Problems to be Solved by the Invention) The above-described scanning microscope device allows light from a sample to pass through a second deflection mirror that performs sub-scanning and a first deflection mirror that performs main scanning, and then enters the photoprinter. Therefore, a stationary spot of light is incident on the photographic image.

On the other hand, it is extremely difficult to deflect a light beam with high precision and high speed. In particular, when beam deflection is performed using a mechanical drive mechanism such as a galvano mirror,
It is impossible to perform high-speed deflection at television rates, while even low-speed deflection has problems such as uneven scanning speed and fluctuations in scanning length. When these uneven scanning speeds and fluctuations in scanning length occur, an inconvenience arises in that the image is distorted. In particular, the first deflection device that performs high-speed deflection in the main scanning direction is likely to cause speed unevenness and fluctuations in the scanning beam.
Particularly noticeable image distortion occurs.

On the other hand, a method can also be considered in which a two-dimensional solid-state imaging device is used as the photoelectric conversion device and the reflected light from the sample is made incident on the two-dimensional solid-state imaging device without passing through the deflection device. However, it is difficult to obtain a two-dimensional solid-state imaging device with high resolution, and the resolution is insufficient for applications such as defect inspection equipment, for example. Moreover, when performing photoelectric conversion using a two-dimensional solid-state imaging device, stray light is likely to enter each light receiving element, resulting in a problem that the S/N ratio decreases.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a scanning microscope imaging device that eliminates the above-mentioned drawbacks and is capable of capturing high-resolution images that are less susceptible to the influence of deflection devices and free from image distortion.

(Means for Solving the Problems) A scanning microscope imaging device according to the present invention includes a light source that generates a light beam, a first deflection device that deflects the light beam generated from the light source at high speed in the main scanning direction, and a beam deflection device that deflects the light beam generated from the light source at high speed in the main scanning direction. a second deflection device having a mirror and deflecting the scanning beam deflected by the first deflection device in a sub-scanning direction orthogonal to the main scanning direction;
An objective lens that scans the sample two-dimensionally by irradiating the scanning beam from the second deflection device as a minute spot onto the sample and receives reflected light from the sample, and a plurality of light receiving elements are arranged in the main scanning direction. a linear image sensor that is arranged one-dimensionally along the objective lens and that receives light emitted from the objective lens and outputs a photoelectric output signal; The present invention is characterized in that an image is formed in the form of a minute spot on the linear image sensor via a device, and the linear image sensor is scanned by light reflected from the sample.

Furthermore, the scanning microscope imaging device according to the present invention can also take images using transmitted light from the sample, and the transmission type microscope imaging device includes a light source that generates a light beam and a light beam that is generated from the light source as the main source. a first deflection device that deflects at high speed in the scanning direction; and a second deflection device that includes a beam deflection mirror and deflects the scanning beam deflected by the first deflection device in a sub-scanning direction orthogonal to the main scanning direction. A device, a condenser lens that scans the sample two-dimensionally by irradiating the scanning beam from the second deflection device as a minute spot onto the sample, and a plurality of light-receiving elements that scan the sample one-dimensionally along the main scanning direction. a linear image sensor that receives transmitted light from the sample and outputs a photoelectric output signal, and a beam deflection mirror, which is arranged to receive transmitted light from the sample and output a photoelectric output signal; a third deflection device that deflects the beam toward the sensor; and an optical system that images the transmitted light from the sample as a minute spot on the linear image sensor, the linear image sensor being scanned by the transmitted light from the sample. It is characterized by being configured to do so.

(Operation) In the present invention, a light beam emitted from a light source is deflected in a main scanning direction and a sub-scanning direction perpendicular to the main scanning direction, and the deflected scanning beam is projected as a minute spot onto a sample through an objective lens. Therefore,
The sample is scanned two-dimensionally with a tiny spot-shaped light beam. Reflected light or transmitted light from the sample is received by an objective lens, and is transmitted through a second deflection device in the case of a reflection type or a second deflection device in the case of a transmission type.
An image is formed as a minute spot on a linear image sensor via a third deflection device synchronized with the deflection device of FIG. Since the light incident on the linear image sensor does not pass through the first deflection device that performs main scanning, this incident light is directed in the direction corresponding to the main scanning direction, that is, in the direction in which the many light receiving elements that make up the linear image sensor are arranged. Therefore, the linear image sensor is scanned one-dimensionally by the light focused into a minute spot from the sample. Therefore, the sample is scanned by a light beam in the form of a minute spot, and the light from the sample is received as light focused in the form of a minute spot and photoelectrically converted. The device can be configured to capture high-resolution images.

In addition, since the light from the sample passes only through the second deflection device and enters the linear image sensor, the effects of speed unevenness and fluctuations caused by the first deflection device are removed, resulting in clear images with little image distortion. can be imaged. In particular, when the first deflection device performs high-speed deflection in the main scanning direction and the second deflection device performs low-speed deflection in the sub-scanning direction for two-dimensional scanning, the fluctuation of the first deflection device that performs high-speed scanning is reduced. Therefore, image distortion caused by the deflection device can be removed. In addition, since the light from the sample does not pass through the first deflection device, the degree of freedom in selecting the first deflection device is expanded. can be used. Therefore, if an acousto-optic element is used as the first deflection device, main scanning can be performed at television rate, and real-time imaging becomes possible.

(Example) FIG. 1 is a diagram showing the configuration of an example of a scanning microscope imaging device according to the present invention. A light beam emitted from a laser light source 1 is expanded by an expander 2, and then enters an acousto-optic element 3, which is a first deflection device. This acousto-optic element 3 vibrates the light beam at high speed and moves the sample in the X direction (main scanning direction).
Scan at high speed at a scanning frequency of _f1 . Acousto-optic element 3
The light beam deflected by is focused by a focusing lens 4, passes through a relay lens 5, is reflected by a half mirror 6 and a total reflection mirror 7, and then enters a vibrating mirror 8, which is a second deflection device. This vibrating mirror 8 performs sub-scanning by deflecting the light beam at a low speed in the Y direction (sub-scanning direction) perpendicular to the X-direction on the sample. The light beam reflected by the vibrating mirror 8 passes through the objective lens 9
The light is focused into a minute spot and enters the sample 10. As a result, the sample 10 is scanned in the X direction and the Y direction at a predetermined scanning frequency by the tiny spot-shaped light beam. In this example, the configuration is such that optical information about the sample is obtained by detecting reflected light from the sample. The light beam reflected by the sample 10 passes through the objective lens 9 again, is reflected by the vibrating mirror 8 and the total reflection mirror 7, passes through the half mirror 6, and enters the linear image sensor 11 in a state where it is converged into a minute spot. This linear image sensor 11
is arranged at a position conjugate with the relay lens 5 with respect to the sample 10, and directs the reflected light from the sample to 1 in the main scanning direction.
Each light-receiving element is arranged one-dimensionally in the X direction so as to receive light line by line, and each light-receiving element receives the reflected light from the sample 10, performs photoelectric conversion, and generates a signal in each element at a readout frequency _f2 . It is configured to read out the amount of charge. Therefore, the linear image sensor 11
will be scanned at frequency f ₁ by the reflected light from the sample. In this example, the scanning frequency f ₁ of the acousto-optic element 3 and the readout frequency f ₂ of the linear image sensor
Both are set to TV rate. In this way, by making the reflected light from the sample enter the photoelectric conversion device only through the low-speed deflection means without passing through the high-speed deflection device, the degree of freedom in selecting the high-speed deflection means increases, and as in this example, The acousto-optic element 3 can be used as a high-speed deflection means. Since this acousto-optic element does not have a mechanical drive mechanism, the scanning speed in high-speed scanning can be made more uniform, and the durability of the imaging device can also be improved.

FIG. 2 is a plan view showing the relationship between the beam spot projected onto the linear image sensor 11 and each light receiving element constituting the linear image sensor. The reflected light from the sample 10 is projected in the form of a minute spot on the linear image sensor 11, but in this example, the diameter of the projected beam spot 12 is set to be slightly larger than the light receiving surface of each of the elements 11a to 11n. Configure. The projected beam spot 12 is deflected in the X direction, which is the arrangement direction of the elements 11a to 11n, so that the reflected light from the sample 10 is one-dimensionally received by each element 11a to 11n and converted into a photoelectric output signal. be done. With this configuration, there is always a one-to-one correspondence between the pixels of the sample 10 and each light-receiving element constituting the linear image sensor 11, so there is no unevenness in the scanning speed of the acousto-optic element 3 in the main scanning direction. Even if this occurs, the amount of light received by each element always changes only slightly, and unlike conventional imaging devices, it is possible to effectively prevent image distortion due to uneven scanning speed. In addition, as in this example, the reflected light from the sample 10 is transmitted to the image sensor 1.
If the configuration is such that the spot diameter is larger than the light-receiving surface of each element of 1, the incident light will be stable against the occurrence of a position error in the position of the incident light on the image sensor 11 and external vibrations. Especially when shooting with zoom, the spot diameter of the light beam tends to fluctuate, so
This is effective for photographing devices equipped with a zoom imaging function.

FIG. 3 is a graph showing the relationship between the readout frequency of the linear image sensor 11 and the amount of charge accumulated in each element. Since the linear image sensor 11 has a charge storage ability, the amount of charge is generated according to the amount of received light until the amount of charge reaches saturation, and the amount of generated charge can be accumulated sequentially. Figure 3A
is a configuration in which the readout frequency f ₂ of the linear image sensor is equal to the scanning frequency f ₁ in the main scanning direction of the light beam, that is, the amount of charge accumulated in the element is read out each time the sample is scanned once with the light beam. Figure B shows the amount of accumulated charge when f ₂ = f ₁ /2, that is, when the sample is scanned twice with the light beam and then the amount of charge accumulated in the element is read out. Figure C shows the amount of accumulated charge when f ₂ = f ₁ /3, that is, when the sample is scanned three times with a light beam and then the amount of charge accumulated in the element is read out. It shows the amount.

In the present invention, since a confocal type microscope device is configured, a high-resolution sample image can be taken. On the other hand, as described above, if the reflected light from the sample scans the linear image sensor multiple times using the charge accumulation effect of the linear image sensor, and then the accumulated charges are read out, the image signal S /N ratio can be further improved. That is, since the laser light includes brightness fluctuations, when the linear image sensor is scanned once, the brightness fluctuations of the laser light appear as noise on the image signal. On the other hand, if the laser beam is scanned multiple times, the brightness fluctuations of the laser beam itself are averaged, and the S/N ratio of the image signal can be improved.

Next, resolution will be explained. FIG. 4A is a diagram schematically showing the scanning state on a sample by the conventional optical scanning microscope imaging device, and FIG. 4B is a diagram schematically showing the scanning state on the sample by the microscopic imaging device according to the present invention. FIG. In conventional scanning microscope devices, when using a light source with low output, the scanning speed must be slowed down and the scanning line density must be set low, which causes the inconvenience of missing optical information between the scanning lines. It was happening. On the other hand, the scanning frequency f ₁ in the main scanning direction of the light beam is set to the image sensor 1.
By setting the reading frequency _f2 to be approximately an integral multiple of the reading frequency f2 of 1, it is possible to obtain a photoelectric output signal of approximately the same magnitude even if the main scanning speed is increased and the scanning line density is increased. As a result, the scanning line density can be set equivalently high without deteriorating the S/N ratio of the photoelectric output signal or slowing down the scanning speed of the light beam, and the optical information of the sample can be reproduced more accurately.
In particular, when pattern defects of photomasks or reticle patterns are inspected using a conventional optical scanning microscope, minute defects often exist between scanning lines and defects are often overlooked. Being able to set the scanning line density to an equivalently high value is extremely effective for pattern defect inspection equipment.

Next, prevention of shading will be explained. Normally, when a deflected light beam is incident on an objective lens, it is subjected to a shading effect by the lens as shown in Figure 5, and the amount of transmitted light of the light beam incident on the periphery of the objective lens is reduced by that of the light beam incident on the center. It will be less than the amount of light. As a result,
This creates an inconvenience in that the central part of the image is reproduced brightly and the peripheral part becomes dark. In such cases, conventional imaging devices that generate photoelectric output signals using photomultiply
If an attempt is made to correct this by changing the scanning speed of the deflection means, distortion will occur in the image. Furthermore, even if electrical correction is attempted, it is extremely difficult to make an unambiguous correction because the scanning speed of the deflection means is uneven. In contrast, in the present invention, the image of the sample and each element constituting the linear image sensor are 1:1
Therefore, the scanning speed by the deflection means is changed so that the scanning speed becomes faster when the light beam enters the center of the objective lens.
If the scanning speed is set to be slow when entering the peripheral area, it is possible to correct the shading caused by the lens, and electrically, if the photoelectric output signal is amplified by taking into consideration the shading characteristics caused by the objective lens, it can be further improved. It can be corrected accurately.

FIG. 6 is a diagram showing the configuration of a modified example of the imaging device according to the present invention. Note that the same components as those used in FIG. 1 will be described with the same reference numerals. In this example, other relay lenses 20 and 21 are arranged between the vibrating mirror 8 and the objective lens 9, and a raster image formed by the acousto-optic element 3 and the vibrating mirror 8 is projected onto the sample 10 by the objective lens 9. do.
With this configuration, the objective lens 9 allows the sample 1 to be
It is possible to project an undistorted raster image onto 0 and obtain an undistorted image signal.

FIG. 7 is a diagram showing the configuration of another modification of the photographing device according to the present invention. In this example, the sample is observed using transmitted light from the sample. Components that are the same as those used in FIG. 1 will be described with the same reference numerals. A light beam emitted from a laser light source 1 is expanded by an expander 2, and is made incident on a first vibrating mirror 30 through an acousto-optic element 3, which is a first deflection device that performs main scanning, and a relay lens 4. This first vibrating mirror 30 rotates in the directions of arrows a and b to perform sub-scanning. Acts as a second deflection device. The light beam reflected by the first vibrating mirror 30 is converged into a minute spot by a condenser lens 31, enters the sample 10, and scans the sample 10 in the X direction and the Y direction. The light beam transmitted through the sample is focused by the objective lens 9 and enters the second vibrating mirror 32. The second vibrating mirror 32 is assumed to vibrate in synchronization with the first vibrating mirror 30, and when the first vibrating mirror 30 rotates in the direction of arrow b, it rotates in the direction of d, and in the direction of arrow a. When rotating, it rotates in the c direction. The light beam reflected by the second vibrating mirror 32 passes through the imaging lens 33 and is projected onto the linear image sensor 11 as a minute spot, thereby forming a confocal microscope.

The present invention is not limited to the embodiments described above, but can be modified and modified in many ways. For example, in the above-described embodiments, an example in which the present invention is used as a microscope imaging device has been described, but the invention can also be applied to imaging devices other than a microscope, such as an imaging device that captures a life-sized image, an enlarged image, a reduced image, and the like.

(Effects of the Invention) As explained above, according to the present invention, reflected light or transmitted light from a sample is not allowed to pass through the first deflection means, but is incident on the linear image sensor only through the second deflection means. Because of this configuration, the influence of scanning speed unevenness, scanning length fluctuation, etc. caused by the first deflecting means can be removed, and the occurrence of image distortion can be reduced. This is particularly effective when high-speed scanning is performed using the first deflection means, since uneven scanning speed is likely to occur. Furthermore, since the degree of freedom in selecting the first deflection means increases, it is possible to use a high-speed deflection device that does not have a mechanical drive mechanism, such as an acousto-optic device, and as a result, it is possible to perform high-speed scanning with high precision, and Since main scanning at TV rate is possible, real-time imaging is also possible.

Further, by setting the readout frequency f ₂ of the linear image sensor to an integral multiple of the scanning frequency f ₁ of the first deflection device, an image signal with a higher S/N ratio can be obtained.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the configuration of an example of a microscope imaging device according to the present invention, Fig. 2 is a plan view showing the relationship between the beam spot projected on the linear image sensor and the light receiving element, and Fig. 3 is the linear image sensor. A graph showing the relationship between the readout frequency and the amount of accumulated charge,
FIG. 4A is a diagram schematically showing the state of the scanning line on the sample of a conventional optical scanning microscope imaging device, and FIG. 4B is a diagram schematically showing the state of the scanning line on the sample of the microscope imaging device according to the present invention. FIG. 5 is a graph showing the shedding effect of the objective lens, and FIGS. 6 and 7 are diagrams showing the configuration of a modified example of the microscope imaging device according to the present invention. 1... Laser light source, 2... Expander, 3...
...Acousto-optic element, 4...Focusing lens, 5, 20,
21...Relay lens, 6...Half mirror, 7
... Total reflection mirror, 8 ... Oscillating mirror, 9 ... Objective lens, 10 ... Sample, 11 ... Linear image sensor, 12 ... Beam spot, 30 ... First
vibrating mirror, 31... condenser lens, 32
...Second vibrating mirror, 33...Imaging lens.

Claims (1)

[Claims] 1. A light source that generates a light beam, and a first light source that deflects the light beam generated from the light source in the main scanning direction at high speed.
a second deflection device having a beam deflection mirror and deflecting the scanning beam deflected by the first deflection device in a sub-scanning direction perpendicular to the main scanning direction; The scanning beam from the device is irradiated onto the sample as a minute spot to separate the sample into two parts.
An objective lens that scans dimensionally and receives reflected light from the sample, and a plurality of light receiving elements are arranged one-dimensionally along the main scanning direction, and receive the light emitted from the objective lens to generate a photoelectric output signal. a linear image sensor that outputs a linear image sensor, the reflected light from the sample received by the objective lens is imaged in the form of a minute spot on the linear image sensor via the second deflection device, and the linear image sensor is A scanning microscope imaging device characterized in that it is configured to scan using reflected light from a sample. 2. A light source that generates a light beam, and a first light source that deflects the light beam generated from this light source in the main scanning direction at high speed.
a second deflection device having a beam deflection mirror and deflecting the scanning beam deflected by the first deflection device in a sub-scanning direction perpendicular to the main scanning direction; The scanning beam from the device is irradiated onto the sample as a minute spot to separate the sample into two parts.
A condenser lens that scans dimensionally, a linear image sensor in which a plurality of light receiving elements are arranged one-dimensionally along the main scanning direction and that receives transmitted light from the sample and outputs a photoelectric output signal, and a beam deflector. a third deflection device having a mirror and deflecting the transmitted light from the sample toward the linear image sensor in synchronization with the second deflection device; 1. A scanning microscope imaging device comprising: an optical system that forms an image as a spot, and configured to scan the linear image sensor using transmitted light from the sample.