JPH0547040B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an imaging device that eliminates image distortion in the horizontal scanning direction.

(Prior Art) Conventionally, as an imaging device that converts optical image information of a sample into an electrical signal, solid-state imaging uses a two-dimensional array of light-receiving elements and sequentially reads signals from each light-receiving element to form an image signal. Imaging devices using these elements have been put into practical use. This imaging device using a two-dimensional solid-state imaging device projects an image of the sample onto the imaging device by fully irradiating the sample, and has a simple configuration.
It has the advantage of being able to obtain image signals, and has come to be used for various purposes.

Furthermore, a separate imaging device scans the sample surface by two-dimensionally deflecting a light beam converged into a minute spot, and detects the reflected light or transmitted light from the sample with a photodetector such as a photodetector. Optical scanning imaging devices that form information as image signals have been put into practical use. This optical scanning imaging device is configured to scan the sample with a microscopic spot-shaped light beam, so it is possible to prevent the generation of stray light, obtain high-resolution image signals, and adjust the brightness and contrast of the image electrically. It is adjustable and has a wide range of uses.

On the other hand, the conventional imaging device described above is a monochrome imaging device, and has the disadvantage that it cannot detect information regarding the color of the sample. Therefore, there is a strong demand for the development of a mirror imaging device with a simple configuration that can also detect information regarding the color of a sample.

Although the imaging device having the above-mentioned configuration has the advantage of being able to take images with a simple configuration, there are various problems when it is used as a color imaging device. For example, an optical scanning type imaging device has a disadvantage in that it is difficult to scan a sample with light beams of three primary colors in a consistent manner, which tends to cause misalignment between the light beams in the horizontal and vertical directions, that is, color misalignment. For this reason, if there is a vertical misalignment, a registration error will occur.
When unevenness occurs in the horizontal direction and scanning speed, distortion occurs in the image of the three primary colors, resulting in the inconvenience that the color information of the sample cannot be accurately reproduced. Furthermore, in order to scan the sample surface at high speed with a light beam, a highly sensitive photosensitive element must be used as a light receiving element, which has the drawback of making the apparatus larger and more expensive. on the other hand,
In imaging devices that use two-dimensional solid-state image sensors, it is difficult to obtain high-resolution image signals due to the low resolution of the two-dimensional solid-state image sensor, and the drawback is that the resolution is insufficient for applications such as defect inspection equipment, for example. .
In addition, two-dimensional solid-state image sensors have low sensitivity and require a powerful light source, which also has the disadvantage of increasing the size of the device.

In order to eliminate the above-mentioned drawbacks, the present inventor has developed a method that allows the light beams of three primary colors to be scanned on the sample in a consistent manner, and even if the scanning speed of each light beam varies, the image does not distort and has high resolution. The present invention provides a color imaging device that is small and inexpensive and can obtain images of 1000 yen.

This color imaging device includes a plurality of light sources that emit a plurality of light beams of different color components, a first deflection means that deflects the plurality of light beams emitted from these light sources in the main scanning direction, and a first deflection means that deflects the plurality of light beams emitted from the light sources in the main scanning direction. Said first
A common second deflection means commonly deflects in a direction orthogonal to the scanning direction by the deflection means, and the light beams deflected by the first and second deflection means are converged into a minute spot shape and directed onto the sample. A projection objective lens, a color separation optical system that separates the reflected light or transmitted light from the sample into each color component, and a plurality of elements are arranged one-dimensionally in the main scanning direction and are separated into each color component. It is characterized by comprising a plurality of linear image sensors each receiving a luminous flux and outputting a photoelectric output signal in synchronization with each other.

In this color imaging device, each of the three primary color light beams is vibrated at high speed in the X direction of the sample by the first deflection means, and each light beam is transmitted to a common second
The three primary color light beams are made incident on the deflection means and deflected in the Y direction perpendicular to the X direction to combine the three primary color light beams into one light beam. The combined light beam is converged into a minute spot through an objective lens and projected onto the sample, and the sample is scanned in the X and Y directions. Then, the reflected light or transmitted light from the sample is separated into each color component by a color separation optical system, and is made incident on a Niria image sensor arranged for each color component. Each linear image sensor has a configuration in which multiple elements are arranged one-dimensionally in a direction corresponding to the X direction, which is the main scanning direction, and each image sensor sequentially reads out the amount of charge accumulated in each element in synchronization. outputs a photoelectric output signal.

(Problems to be Solved by the Invention) The color imaging device described above has a configuration in which a linear image sensor receives the light flux of each color component from the sample and outputs a photoelectric output signal in synchronization with each other. A color image signal without image distortion or color shift can be obtained even if unevenness occurs in the scanning speed in the horizontal direction. However, since the refractive index of various lenses including the objective lens for each light beam is different, chromatic aberration occurs, resulting in the drawback that the scan areas of the light beams on the sample do not match each other. As a result, when a color image is reproduced on a television monitor, a color shift occurs in the horizontal direction, making it impossible to obtain a clear, high-resolution color image. If an attempt is made to remove such color shift caused by the chromatic aberration of the objective lens by adjusting the distance from the objective lens to the linear image sensor, the focal state will change and the image will become blurred. Further, the various optical elements that make up the optical system must be mounted with high precision with respect to the optical axis, but if there is an error in the mounting of the optical elements, positional deviations will occur in the horizontal scanning direction as well.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to eliminate the above-mentioned drawbacks, and to provide color imaging capable of reproducing clear, high-resolution images without causing positional deviation in the horizontal scanning direction even if chromatic aberration of the objective lens or installation error of the optical element occurs. It provides equipment.

(Means for Solving the Problems) The imaging device of the present invention includes: a light source that emits a light beam; a first deflection unit that deflects the light beam emitted from the light source in the main scanning direction; a second deflection means having a beam deflection mirror that deflects the light beam deflected by the deflection means in a sub-scanning direction perpendicular to the scanning direction of the first deflection means; and the first and second deflection means. It has an objective lens that converges the deflected light beam into a minute spot and projects it toward the sample, and a plurality of light receiving elements arranged one-dimensionally in the main scanning direction, and the light reflected from the sample is reflected from the sample. The present invention is characterized by comprising a linear image sensor that receives light through two deflection means, and a means for adjusting the readout frequency of the linear image sensor according to the amount of image distortion in the main scanning direction.

Furthermore, the imaging device according to the present invention includes a plurality of light sources that emit a plurality of light beams of different color components, at least one scanning direction deflection element, and a beam combining optical system, and a beam deflection mirror for deflecting the combined light beam in a sub-scanning direction perpendicular to the main-scanning direction. a second deflection means; an objective lens that converges the light beam deflected by the first and second deflection means onto a minute spot and projects it onto the sample; and a light beam reflected by the sample and deflected by the second deflection means. a color separation optical system that separates the reflected light into each color component; and a plurality of light receiving elements arranged one-dimensionally in the main scanning direction, and the color separation optical system separates the reflected light from the sample into the second color component. A plurality of linear image sensors receive light through a deflection means and a color separation optical system and output photoelectric output signals in synchronization with each other, and the readout frequency of the linear image sensor is adjusted according to the amount of image distortion in the main scanning direction. The invention is characterized by comprising means for adjusting.

(Function) In the present invention, the light flux from the sample is received by a linear image sensor in which each light receiving element is arranged in a direction corresponding to the horizontal scanning direction, and the readout frequency of this linear image sensor is adjusted according to the amount of distortion in the horizontal scanning direction. Adjust. As a result, image distortion in the horizontal scanning direction caused by chromatic aberration of the objective lens or distortion of the optical system can be easily removed by simply adjusting the readout frequency of the linear image sensor.

(Embodiment) FIG. 1 is a diagram showing the configuration of an embodiment of a color imaging device according to the present invention. A green light source 1, a red light source 2, and a blue light source 3 are arranged to emit light beams of the three primary colors of green, red, and blue, respectively. In this example, the green light source 1 is an Ar laser that emits light with a wavelength of 488 nm, the red light source 2 is a He-Ne laser that emits light with a wavelength of 633 nm, and the blue light source 3 is a He-Ne laser that emits light with a wavelength of 633 nm.
A He-Cd laser that emits light at a wavelength of 442 nm is used. It is assumed that all the light beams emitted from each of the light sources 1 to 3 are linearly polarized. A light beam emitted from a green light source 1 is expanded into a parallel beam by an expander 4, reflected by a right-angle prism 5, and then incident on a first acousto-optic element 6, which is a first polarizing element.
This first acousto-optic element 6 vibrates a green light beam at high speed in the main scanning direction, and the green light beam vibrates at high speed and scans the sample surface in the X direction (perpendicular to the plane of the paper) at a scanning frequency f ₁ . do. The light beam deflected by the acousto-optic device 6 passes through relay lenses 7 and 8, passes through a first deflection prism 9 and a quarter-wave plate 10, which act as beam splitters, respectively, and then passes through a first Gikkreuzk prism 11. incident on .
This first dichroic prism 11 reflects only red light and transmits light in other wavelength ranges. The green light beam that has passed through the first dichroic prism 11 passes through a second dichroic prism 12 that reflects only blue light, and enters a vibrating mirror 13 that is a second deflection element. This vibrating mirror 13 is commonly used for red light beam, green light beam, and blue light beam, and directs each light beam in the Y direction (direction of the paper) perpendicular to the X direction of the sample.
to be deflected. The green light beam reflected by the vibrating mirror 13 passes through relay lenses 14 and 15, and is converged into a minute spot by the objective lens 16.
7. As a result, the sample 17 is scanned in the X and Y directions at a predetermined scanning frequency by the green light beam in the form of a minute spot. In this example, optical information about the sample is obtained by detecting reflected light from the sample 17. The reflected light from the sample 17 is again focused by the objective lens 16, passes through the relay lenses 15 and 14, enters the vibrating mirror 13 again, is reflected by the vibrating mirror 13, and is reflected by the second and first dichroic prisms 12 and 11 and further 1/
The light passes through the four-wavelength plate 10 and enters the first polarizing prism 9. The light flux incident on the polarizing prism 9 is 1/
Since it passes through the 4-wavelength plate 10 twice, its polarization plane is rotated by 90°, and is reflected by the polarization plane 9a.
The light enters the linear image sensor 18 in the form of a minute spot of light. This linear image sensor 18 is placed at the imaging position of the relay lens 14, and each element is aligned in the X direction of the sample (perpendicular to the plane of the paper) so as to receive the reflected light from the sample 17 line by line in the main scanning direction. They are arranged one-dimensionally in corresponding directions, each element receives reflected light from the sample 17, performs photoelectric conversion, and reads out the charges accumulated in each element at a readout frequency _f2 . Since the linear image sensor has a charge accumulation effect, there is always a one-to-one correspondence between the sample 17, the pixel, and each light receiving element constituting the linear image sensor 18, and the scanning in the main scanning direction by the acousto-optic element 6 Even if the speed is uneven, the amount of light received changes only slightly, and unlike conventional imaging devices that perform photoelectric conversion, image distortion does not occur.

Next, scanning with red light will be explained. The light beam generated from the red light source 2 passes through an expander 19 and a rectangular prism 20, and then is converted to the same frequency as the first acousto-optic element 6 by the second acousto-optic element 21.
The sample 17 is vibrated at high speed in the X direction at _f1 , and the sample 17 is scanned at high speed in the X direction at a scanning frequency _f1 . The red light beam deflected by the second acousto-optic element 21 passes through the relay lenses 22 and 23, passes through the second polarizing prism 24, and passes through the first correction vibrating mirror 25.
incident on . This first correction vibrating mirror is 25
Red light beam objective lens 16 and relay lens 1
This is for correcting displacement in the Y direction due to chromatic aberrations of Nos. 4 and 15. In this example, correction is made when the green, red, and blue light beams are shifted such that the blue light beam is expanded in the Y direction and the red light beam is contracted, with the green light beam as the center. The red and blue light beams are corrected to match the green light beam in the Y direction. Therefore, this first correction vibrating mirror 25 deflects the red light beam in the same direction as the deflection direction of the common vibrating mirror 13 by an amount corresponding to the amount of deviation of the red light beam from the green light beam on the sample 17. Vibrate to deflect. In addition, this correction vibration mirror 25
When observing the reflected light from the sample 16, the second deflecting prism 24 and the first It is placed between the dichroic mirror 11 and the dichroic mirror 11. The light beam reflected by the first correction vibrating mirror 25 passes through the quarter-wave plate 26 and enters the first dichroic prism 11. Since this first dichroic prism 11 reflects only red light, the incident red light beam is reflected and enters a common optical path, passes through the second dichroic prism 12, and enters the vibrating mirror 13. . Then, it is deflected in the Y direction by the vibrating mirror 13 in the same way as the green light beam, passes through relay lenses 14 and 15, is focused into a minute spot by the objective lens 16, and enters the sample 17. As a result, the portion of the sample 17 scanned by the green light beam is simultaneously scanned by the red light beam. The reflected light from the sample 17 is again focused by the objective lens 16, passed through relay lenses 15 and 14, reflected by the vibrating mirror 13, and further transmitted through the second dichroic prism 12 and reflected by the first dichroic prism 11. reflect. Then again 1/
The polarization plane changes by 90° after passing through the 4-wave plate 26, and the first
The light is reflected by the correction vibrating mirror 25 , further reflected by the polarization plane 24 a of the second polarization prism 24 , and enters the half mirror 27 . The transmitted light is converged into a minute spot and enters the second linear image sensor 28, and the reflected light enters the focus detection device 29 and is used for detecting the focus of the objective lens 16. The second linear image sensor 28 is disposed at the imaging position of the relay lens 14 similarly to the first linear image sensor 18, and is configured to receive reflected light from the sample 17 line by line in the main scanning direction. The elements are arranged one-dimensionally in a direction corresponding to the X direction of sample 17 (direction perpendicular to the plane of the paper).
It is assumed that the reflected light from 7 is received by each light receiving element, photoelectric conversion is performed, and the charges accumulated in each element are read out at a readout frequency _f2 .

Next, scanning with blue light will be explained. The blue light beam emitted from the blue light source 3 is transmitted to the expander 30.
After passing through the right angle prism 31, the third acousto-optic element 32 vibrates at high speed in the main scanning direction at a scanning frequency of f ₁ , passes through the relay lenses 33 and 34, passes through the third polarizing prism 35, and generates a second correction vibration. The light enters the mirror 36. This second correction vibration mirror 3
6 deflects the blue light beam in the Y direction so as to reduce the deflection amount of the common vibrating mirror 13 by an amount corresponding to the shift amount in the Y direction of the blue light beam with respect to the green light beam on the sample 17. The blue light beam reflected by the second vibrating mirror 36 for correction is 1/
The light passes through the four-wavelength plate 37, is reflected by the second dichroic prism 12, enters a common optical path, and enters the common vibrating mirror 13. The vibrating mirror 13 deflects the light beam in the Y direction in the same manner as the green and red light beams. Further, the light passes through relay lenses 14 and 15 and is converged into a minute spot by an objective lens 16, and enters a sample 17. As a result, the red, green, and blue light beams are combined to form one scanning light beam, and the sample 17 is scanned in the X and Y directions by this scanning light beam. The blue reflected light from the sample 17 is again focused by the objective lens 16, passes through the relay lens 15 and the imaging lens 14, and enters the common vibrating mirror 13. Then, it is reflected by this vibrating mirror 13,
It is reflected by the second dichroic prism 12, deviates from the common optical path, and is transmitted by the 1/4 wavelength plate 37, the deflection plane changes by 90°, and the second correction vibrating mirror 3
6 and the polarizing prism 35, and enters the third linear image sensor 38 which receives the reflected blue light in a state where it is converged into a minute spot. This third linear image sensor 38 is also arranged in the imaging device of the relay lens 14, and like the first and second linear image sensors 18 and 28, the sample 17
Each element is arranged one-dimensionally in a direction corresponding to the X direction of the sample 17 so as to receive the blue reflected light from the main scanning direction line by line, and the charge accumulated in each element is read out at a frequency f ₂ Configure it so that it can be read. Since the configuration is such that the vibrating mirror 13 is shared for the light beams of each color component, there is no deviation of the light beams in the vertical direction, and the occurrence of registration errors can be effectively prevented.

FIG. 2 is a plan view showing the relationship between the beam spot projected onto the linear image sensor and each element constituting the linear image sensor. In the present invention, three linear image sensors 18, 28 and 3 are used.
8 have the same configuration, the first linear image sensor 18 that receives green light will be explained. The reflected light from the sample 17 is projected onto the linear image sensor 18 in the form of a minute spot, but in this example, the diameter of the projected beam spot 60 is set to be slightly larger than the light receiving surface of each of the elements 18a to 18n. Configure. Since the projected beam spot 60 is sequentially deflected in the X direction, which is the arrangement direction of the elements 18a to 18n, the reflected light from the sample 17 is one-dimensionally received by each of the elements 18a to 18n, and is reflected from the sample 17. A charge corresponding to the amount of reflected light is accumulated in each element and converted into a photoelectric output signal. If the configuration is such that the reflected light from the sample 17 is incident as a spot diameter larger than the light-receiving surface of each element of the image sensor 18 as in this example, the position error of the incident light with respect to the image sensor 18 or disturbance vibration may occur. becomes stable. In particular, when projecting with a zoom, the spot diameter of the light beam is likely to change, so this is effective for an imaging device equipped with a zoom photographing function.

FIG. 3 is a graph showing the relationship between the readout frequency of the linear image sensor and the amount of charge accumulated in each element. In the embodiment described above, the scanning frequency f ₁ of the acousto-optic elements 6, 21, and 32 and the readout frequency f ₂ of the linear image sensors 18, 28, and 38 were in a 1:1 relationship, but the linear image sensor has a charge storage capacity. , there is no need for synchronization, and the scanning frequency f ₁ by the acousto-optic element can be set to be higher than the readout frequency f ₂ . This example shows an example that utilizes this charge accumulation effect. Figure 3A shows the case where the readout frequency _f2 of the linear image sensor is equal to the scanning frequency _f1 in the main scanning direction of the light beam, that is, the charge accumulated in each element each time the sample is scanned once with the light beam. Figure B shows the amount of accumulated charge when the amount is read out.
C shows the amount of accumulated charge when f ₁ = 2f ₂ , that is, when the sample is scanned twice with a light beam and then _the amount of charge accumulated in the element is read out.
=3f ₂ , that is, the amount of accumulated charge is shown in a case where the sample is scanned three times with a light beam and then the amount of charge accumulated in the element is read out.

In this way, by configuring the image sensors 18, 28, and 38 to receive the reflected light from the sample 17 multiple times, the main scanning frequency f ₁ of the light beam can be increased.
Compared to the case where the readout frequency f ₂ of the image sensor and the readout frequency f 2 of the image sensor are set equal, the influence of the noise of the light source is averaged out, so that the S/N ratio of the photoelectric output signal can be substantially improved. Of course, in this case, the readout frequency _f2 of the image sensor is always constant, and a signal at a predetermined television rate can be obtained.

In FIG. 3, the readout frequency of the image sensor is changed, but it goes without saying that the same effect can be obtained even if the readout frequency of the image sensor is kept constant and the scanning frequency of the acousto-optic element is changed.

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 microscope imaging device according to the present invention. FIG. In conventional optical 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, resulting in the loss of optical information between the scanning lines. An inconvenience was occurring. On the other hand, if the scanning frequency f ₁ of the light beam in the main scanning direction is set to be approximately an integral multiple of the readout frequency f ₂ of the image sensors 18, 28, and 38, the main scanning speed can be increased and the scanning line density can be increased. However, it is possible to obtain a photoelectric output signal of approximately the same magnitude. 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 light beam scanning speed, and the optical information of the sample can be reproduced more accurately. In particular, when inspecting pattern defects on photomasks and reticle patterns using conventional optical scanning microscopes, minute defects often exist between scanning lines and 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, correction of color shift in the horizontal scanning direction due to chromatic aberration of the objective lens will be explained. 5A to 5D are for explaining color shift correction using the chromatic aberration of the objective lens. FIG. A line diagram showing the image projected on the image sensor and the monitor, C is a waveform diagram showing the readout clock signal to be supplied to each linear image sensor, and D is a diagram showing each linear image sensor and the monitor after correction. FIG. 2 is a diagram showing an image projected onto the image; If the objective lens 16 has chromatic aberration, the refractive index of the objective lens 16 for each light beam will be different, resulting in different magnifications. As a result, the scanning length of each light beam on the sample 17 in the horizontal scanning direction and the projection area of the image projected onto each linear image sensor 18, 28, and 38 are different from each other. This example shows an example in which chromatic aberration occurs, in which the red light beam is reduced and the blue light beam is expanded, centering on the scanning length of the green light beam. Fifth
Figure B shows the image of the object (indicated by arrows) projected onto each of the linear image sensors 18, 28, and 38 when such chromatic aberration occurs. A reduced image is projected onto the third linear image sensor 28, and an enlarged image is projected onto the third linear image sensor 38. As a result, if the linear image sensors 18, 28, and 38 are read out synchronously, a color shift occurs on the monitor 39 in the horizontal scanning direction. As explained at the beginning of the specification, this kind of color shift due to chromatic aberration can be solved by adjusting the position of the linear image sensor in the optical axis direction and changing the magnification of the projected images, but the focal point This causes a problem in that the image on the linear image sensor becomes blurred due to the state being out of alignment. Therefore, in the present invention, each linear image sensor 1
8, 28, and 38 are maintained in focus, and the readout frequency of each linear image sensor is adjusted according to the amount of chromatic aberration to match the magnification of each color component image on the monitor. FIG. 5C shows the readout clock signal waveform to be supplied to each linear image sensor to eliminate the chromatic aberration shown in FIGS. 5A and 5B. If the image projected on the linear image sensor is reduced due to chromatic aberration, the readout clock frequency may be adjusted to be lower, and if the image is enlarged, the readout clock frequency may be adjusted to be higher. . In this example, the first linear image sensor 18 receives the green light beam with the smallest amount of chromatic aberration.
The frequency of the readout clock signal of the second linear image sensor 28 is adjusted to be lower according to the amount of chromatic aberration based on the readout clock signal supplied to the third linear image sensor 38. Adjust to raise the frequency. FIG. 5D shows each linear image sensor 18, 2 when the readout clock signal of the linear image sensor 18 and 38 is adjusted according to the amount of chromatic aberration.
8 and 38 and the image reproduced on the monitor 39 are shown. If the configuration is such that each linear image sensor is kept in focus and the readout frequency is adjusted according to the amount of chromatic aberration, it is possible to maintain the resolution of the reproduced image and also reduce the color in the horizontal scanning direction due to the chromatic aberration of the objective lens. Misalignment can be easily removed.

FIG. 6 is a block diagram showing the configuration of an example of the drive circuit. A synchronizing circuit 40 for generating vertical and water synchronizing signals V and H is connected to a clock generating circuit 41 to supply a horizontal synchronizing signal H. This clock generating circuit 41 uses the horizontal synchronizing signal H to
and three types of clock signals C ₀ , C ₁ and
Generate C ₂ . As shown in FIG. 5C, a reference clock signal C 0 is supplied to the first linear image sensor 18 that receives green component light, and a clock signal C ₀ that is a reference signal is supplied to the second linear image sensor 28 at a frequency lower than C ₀ . The third linear image sensor 38 is supplied with a clock signal C ₁ having _a higher frequency than C ₀ . In addition, the synchronous circuit 40
includes first, second and third acousto-optic elements 6, 21
and an acousto-optic element drive circuit 42 that controls the drive of the vibrating mirror 13 to supply the horizontal synchronizing signal H, and a vibrating mirror drive circuit 43 that controls the drive of the vibrating mirror 13 to supply the vertical synchronizing signal V. , further connects the processor circuit 44 and outputs the vertical synchronization signal V.
and horizontal synchronization signal H. The first, second and third linear image sensors 18, 28 and 38
Since the amount of charge corresponding to the amount of reflected light from the sample 17 is accumulated in each element, these amounts of charge are read out based on the clock pulses C ₀ , C ₁ and C ₂ , and are stored in each of the linear image sensors 18 , 28 and 28 . 38
The image signals are amplified through amplifiers 45, 46 and 47 connected to the image signals, and a vertical synchronizing signal V and a horizontal synchronizing signal H supplied from the processor circuit 44 are applied to form each color image signal. Then, each color image signal is supplied to a color monitor 48 and recorded thereon, or recorded on a VTR 49. With this configuration, color shift in the horizontal scanning direction due to chromatic aberration can be easily removed by simply correcting the readout clock signals of the two linear image sensors 28 and 38. In this example, the linear image sensor 1
Although the readout frequencies of 8, 28, and 38 do not match the scanning frequencies of acousto-optic elements 6, 21, and 32, since the linear image sensor has a charge storage ability, the scanning frequency f ₁ of the acousto-optic elements and Even if a deviation occurs between the readout frequencies of each linear image sensor, problems such as image distortion and color shift will not occur. Furthermore, when the objective lens 16 is replaced, the clock signal can be changed according to the chromatic aberration characteristics of the objective lens, so the clock frequency for each objective lens can be stored in advance in the ROM and used when replacing the objective lens. The data can be automatically read out.

FIG. 7 is a block diagram showing the configuration of a modified example of the drive circuit. In this example, a clock generation circuit 41 generates a reference clock _C0 for reading, and supplies it to each linear image sensor 18, 28, and 38 to read out the charges accumulated in each linear image sensor synchronously. The respective read signals are transmitted to each amplifier 45, 46 and 4 by a write clock signal supplied from the write control circuit 53.
Line memories 50 and 5 provided after 7, respectively.
1 and 52, respectively. Then, the readout control circuit 54 generates three types of readout clock signals: a readout clock signal with a reference frequency and two types of readout clock signals whose frequencies have been corrected to eliminate the amount of deviation due to chromatic aberration, and converts the reference readout clock signal into a line. The corrected clock signal is supplied to the memory 50 and sent to the frame memory 51.
and 52, respectively. Then, the signals of each color component once stored in the frame memories 50, 51, and 52 are read out at different frequencies to correct color shift due to chromatic aberration. In this way, even with a configuration in which a line memory is provided at the rear stage of each linear image sensor and the line memory readout frequency is corrected, color shift in the horizontal scanning direction due to chromatic aberration can be easily removed.

Next, a method for removing distortion when image distortion occurs in the horizontal scanning direction due to errors or distortions in the optical system will be described. Even if the color shift caused by the chromatic aberration of the objective lens is removed, if there is distortion in the optical system, that is, if there are installation errors in the various optical elements such as mirrors and lenses that make up the optical system, the image will be distorted in the horizontal scanning direction. This may cause inconvenience. According to the present invention, even if image distortion in the horizontal scanning direction occurs due to such an optical system, the image distortion in the horizontal scanning direction can be effectively removed by appropriately adjusting the readout frequency of the linear image sensor. 8th
Figure A shows an example where barrel-shaped distortion occurs on the monitor. This barrel-shaped image distortion occurs because the central portion in the vertical scanning direction is expanded in the horizontal scanning direction and both ends are reduced. In this case, as shown in FIG. 8B, a clock signal whose readout frequency is adjusted to be low is supplied to the linear image sensor in the portions corresponding to both ends in the vertical scanning direction, and as the clock signal increases toward the center. This can be easily removed by supplying a clock signal adjusted to have a high readout frequency to the linear image sensor. in this case,
The synchronization circuit 40 supplies both the horizontal synchronization signal H and the vertical synchronization signal V to the clock generation circuit 41, and the clock generation circuit 41 generates a frequency-adjusted read clock signal while making them correspond to the vertical synchronization signal V.

FIG. 9 shows an example in which image distortion occurs with different magnifications on both sides of the optical axis in the horizontal scanning direction. If a mounting error occurs in the mirror in the optical system, image distortion will occur such that the magnification is different on both sides of the optical axis. In this example, the magnification on the left side of the optical axis on the screen is high, and the magnification on the right side is low. In this case, as shown in FIG. A clock signal whose frequency is adjusted is supplied to adjust the readout frequency of the linear image sensor to be different on the left and right sides with respect to the optical axis. By removing the distortion caused by the difference in magnification in the horizontal scanning direction, the dimensional accuracy in the horizontal scanning direction on the monitor can be improved. This is effective when determining from a generated image.

FIG. 10 shows an example of removing image distortion in which the amount of displacement in the horizontal scanning direction changes nonlinearly with the distance from the optical axis. Even when nonlinear image distortion occurs depending on the distance from the optical axis as shown in Figure 10A, the readout frequency of the light receiving element of the linear image sensor is adjusted to the amount of distortion in the horizontal scanning direction as shown in Figure 10B. Nonlinear distortion can be easily removed by configuring to adjust accordingly.

The present invention is not limited to the embodiments described above, but can be modified and changed in many ways. For example, in the above-mentioned embodiments, the embodiment is applied to a color imaging device, but the present invention can also be applied to a monochrome imaging device using a single light beam.

Further, in the above-described embodiments, the configuration is such that the image is taken using the reflected light from the sample, but it is also possible to use the configuration that the image is taken using the transmitted light from the sample.

Further, as a means for deflecting the light beam, any deflecting means such as a polygon mirror can be used.

Further, in the above-described embodiment, an acousto-optic element is arranged for each of the three primary color light beams, but each primary color light beam may be made incident on a single acousto-optic element to vibrate at high speed. In this case, the optimal angle of incidence on the acousto-optic element differs depending on the wavelength of the light, so each light beam is made incident on a single acousto-optic element by changing the angle of incidence within the same plane and deflected in the X direction. .
It is also possible to make the three primary color light beams incident on a single acousto-optic element along different planes. In this way, when using a single acousto-optic element,
An optical system is required to direct the light beams emitted from the acousto-optic elements in different directions into a common vibrating mirror, but since acousto-optic elements are expensive, the advantage of reducing the cost of the entire device can be achieved. .

(Effects of the Invention) The effects of the present invention explained above are summarized as follows.

(1) The readout frequency of the linear image sensor or memory is changed according to the amount of positional deviation in the horizontal scanning direction caused by the chromatic aberration of the objective lens or the distortion of the optical system. Just by making adjustments, it is possible to eliminate positional deviations in the horizontal scanning direction and image distortion, and reproduce clear, high-resolution images.

(2) When applied to a color imaging device, the readout frequency of each linear image sensor that receives the light beam of each color component from the sample is corrected according to the amount of chromatic aberration of the objective lens, so chromatic aberration of the objective lens can be easily corrected. This enables the reproduction of clear, high-resolution color images with no color shift.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an embodiment in which the imaging device according to the present invention is applied to a color imaging device, FIG. 2 is a plan view showing the relationship between a beam spot projected on a linear image sensor and an element, and FIG. Figure 3 A-C
is a graph showing the relationship between the readout frequency of the linear image sensor and the amount of accumulated charge, Figures 4A and B are diagrams showing the state of the scanning line on the sample, and Figures 5A to D are graphs showing the correction of color shift due to chromatic aberration. Diagram to explain,
FIG. 6 is a block diagram showing the configuration of an example of the drive circuit, FIG. 7 is a block diagram showing the configuration of a modified example of the drive circuit, FIG. 8 is a diagram for explaining the removal of barrel distortion, and FIG. The figure is a line diagram to explain the removal of distortion due to the difference in magnification between the left and right sides centered on the optical axis in the horizontal scanning direction. It is a line diagram for explanation. 1... Red light source, 2... Green light source, 3... Blue light source, 4, 19, 30... Expander, 5, 2
0, 25, 31, 36...Right angle prism, 6, 2
1, 32... Acousto-optic element, 7, 8, 14, 1
5, 22, 24, 33, 34...Relay lens,
9, 24, 35...Polarizing prism, 10, 26,
37...1/4 wavelength plate, 11, 12...Dichroic prism, 13...Vibrating mirror, 16...Objective lens, 17...Sample, 18, 28, 38...
Linear image sensor, 27...Half mirror,
29...Focus detection device, 40...Synchronization circuit, 41
... Clock generation circuit, 42 ... Acousto-optic element drive circuit, 43 ... Vibrating mirror drive circuit, 44 ...
Processor circuit, 45, 46, 47...amplifier,
48...Color monitor, 49...VTR, 50,
51, 52...Frame memory, 53...Write control circuit, 54...Read control circuit, 60...Beam spot.

Claims (1)

[Claims] 1. A light source that emits a light beam, a first deflection device that deflects the light beam emitted from the light source in the main scanning direction, and a light beam deflected by the first deflection device. a second deflection means having a beam deflection mirror that deflects the light beam in a sub-scanning direction perpendicular to the scanning direction of the first deflection means, and converges the light beams deflected by the first and second deflection means onto a minute spot. an objective lens that projects the image toward the sample, and a plurality of light receiving elements arranged one-dimensionally in the main scanning direction, and receives reflected light from the sample via the second deflection means. An imaging device comprising: a sensor; and means for adjusting the readout frequency of the linear image sensor according to the amount of distortion of an image in the main scanning direction. 2. A light source that emits a light beam, a first deflection means that deflects the light beam emitted from the light source in the main scanning direction, and a beam deflection mirror, and the light deflected by the first deflection means. a second deflection means for deflecting the beam in a sub-scanning direction perpendicular to the scanning direction of the first deflection means; and a second deflection means for deflecting the beam in a sub-scanning direction perpendicular to the scanning direction of the first deflection means; a linear image sensor that has a plurality of light receiving elements arranged one-dimensionally in the main scanning direction and receives reflected light from the sample via the second deflection means; An imaging device comprising: a memory device that stores an output signal from the linear image sensor; and means for adjusting a read frequency of the memory device according to an amount of distortion of an image in the main scanning direction. 3 having a plurality of light sources emitting a plurality of light beams of different color components, at least one scanning direction deflection element and a beam combining optical system, receiving the light beams of the different color components and deflecting them in the main scanning direction; a first deflection means for emitting the combined light beam, a second deflection means having a beam deflection mirror and deflecting the combined light beam in a sub-scanning direction perpendicular to the main scanning direction; an objective lens that converges the light beams deflected by the first and second deflection means onto a minute spot and projects them onto the sample; a color separation optical system that separates the colors into two; and a plurality of light receiving elements arranged one-dimensionally in the main scanning direction, each color component light reflected by the sample is transmitted to the second deflection means and the color separation optical system. A plurality of linear image sensors that receive light through a plurality of linear image sensors and output photoelectric output signals in synchronization with each other, and a means for adjusting the readout frequency of the linear image sensors according to the amount of image distortion in the main scanning direction. An imaging device characterized by: 4 having a plurality of light sources emitting a plurality of light beams of different color components, at least one scanning direction deflection element and a beam combining optical system, receiving the light beams of the different color components and deflecting them in the main scanning direction; a first deflection means for emitting the combined light beam, a second deflection means having a beam deflection mirror and deflecting the combined light beam in a sub-scanning direction perpendicular to the main scanning direction; an objective lens that converges the light beams deflected by the first and second deflection means onto a minute spot and projects them onto the sample; a color separation optical system that separates the colors into two; and a plurality of light receiving elements arranged one-dimensionally in the main scanning direction, each color component light reflected by the sample is transmitted to the second deflection means and the color separation optical system. a plurality of linear image sensors that receive light through the sensor and output photoelectric output signals in synchronization with each other; a memory device that stores the output signals from the linear image sensors; and a memory device that stores the output signals from the linear image sensors; An imaging device comprising: means for adjusting according to the amount of distortion.