JPH11264934A - Focus detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a focus detecting device easy to adjust, simple to control, wide in focus detectable range and capable of guiding focus direction without making position recognition impossible. SOLUTION: This device is equipped with a two-split photodetecting element 60 by which a surface to be measured is irradiated with the light from a light source output a signal corresponding to the quantity of the reflected light from the surface, a photodetection optical system which includes an objective 57 for guiding the reflected light to the two-split photodetecting element 60, photodetecting elements 61 and 62 which are arranged opposite at positions distant from the two-split photodetecting element 60 and output a signal corresponding to the quantity of light from the measured surface at a position that can not e detected by the two-split photodetecting element 60, and a signal processing system 63 which decides the position of the said measured surface according to the output signals of the two-split photodetecting element 60 and photodetecting elements 61 and 62.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus detecting device for focusing on an object to be detected in a microscope or an optical measuring device.

[0002]

2. Description of the Related Art There is known a focus detection apparatus which irradiates a surface to be measured with a probe light through an objective lens and detects a focus on the object based on light reflected from the surface to be measured. However, in an ordinary microscope or the like, a plurality of objective lenses having different magnifications are prepared and selectively used among them. Therefore, different NA depending on the magnification of the objective lens
The range in which the focus can be detected differs for each objective lens depending on the (numerical aperture) and the focal length. Specifically, the lower the magnification of the objective lens, the wider the range in which the focus can be detected, and conversely, the higher the magnification, the narrower the range.

However, in the case of a high-magnification objective lens, since the focus detection range is narrow as described above, it is not possible to cope with a step on the surface to be measured, and focus detection becomes impossible or time is required. There is.

In such a case, it is considered that an optical system should be used so as to widen the range in which the focus can be detected by a high-magnification objective lens. The range in which the focus can be detected is too wide, resulting in a decrease in detection accuracy.

As a method for addressing such a problem, a configuration as disclosed in Japanese Patent Application Laid-Open No. 8-43717 has been considered. FIG. 10 shows a focus detection device disclosed in Japanese Patent Application Laid-Open No. 8-43717, in which a laser beam emitted from a laser emitting unit 20 is converted into a parallel light beam via a collimator lens 40 (P is an intermediate image forming position). A half of the light beam is shielded by a shielding plate 41 disposed in the optical path, and the other half is condensed by a condenser lens 42 and then incident on the polarization beam splitter 21.

The light reflected by the polarization beam splitter 21 is transmitted through an imaging lens 22, a half mirror 23, a quarter-wave plate 24 and an objective lens 25, and is irradiated on a surface 26 to be measured. .

[0007] The reflected light from the measured object 26 is transmitted through the objective lens 25 and the quarter-wave plate 24 again, and is then divided by the half mirror 23 into a first optical path and a second optical path. Then, the light passes through the imaging lenses 22 and 32 disposed on the first and second optical paths, and the light passing through the imaging lens 22 passes through the polarization beam splitter 21, and the condensing point Q of the imaging lens 22. Light receiving element 43 arranged at the position
Focus on

The two-division light receiving element 43 has two photoelectric conversion units A and B, and these photoelectric conversion units A and B can output a voltage signal corresponding to the amount of light received. . On the other hand, the light passing through the imaging lens 32 is condensed on a two-part light receiving element 44 similarly arranged at the condensing point R of the imaging lens 32 and having the same configuration as the two-part light receiving element 43. I do.

The output signals from these two light receiving elements 43 and 44 are sent to the signal processing system 30, respectively, where the calculation is executed, so that a displacement signal corresponding to the displacement of the surface 26 to be measured can be obtained. It becomes something.

The signal processing system 30 executes a predetermined operation on each of the input signals, specifically, a difference / sum operation of each of the signals, and performs a displacement signal corresponding to the surface shape of the surface 26 to be measured. Is provided. Then, focusing control for the measured surface 26 is performed based on the displacement signal formed at this time.

Here, considering the respective magnifications of the imaging lenses 22 and 32 in the first optical path passing through the imaging lens 22 and the second optical path passing through the imaging lens 32, the focal length of the objective lens 25 is set to f0. In this case, since the light flux emitted from the objective lens 25 is a parallel light, if the magnifications in the first and second optical paths are M1 and M2, respectively, it is represented by M1 = f1 / f0 M2 = f2 / f0. Therefore, by setting f1 and f2 to different values, the signal processing system 30 can simultaneously obtain two signals, a displacement signal with a high magnification and a displacement signal with a low magnification.

[0012]

However, in the above-mentioned Japanese Patent Application Laid-Open No. 8-43717, a plurality of light receiving optical systems are provided, and a two-part light receiving element is used for the light detecting means. The center must be aligned with high accuracy, and the work must be performed by a plurality of light receiving optical systems and light detecting means. For this reason, adjustment is very difficult in practice, and a great deal of time is required for the operation, resulting in a significant increase in cost.

Further, it is necessary to simultaneously output a signal on the high-magnification side and a signal on the low-magnification side, and control to simultaneously read the plurality of signals, which makes the control complicated and difficult.
Specifically, after moving to a rough focus position on the low magnification side, at what timing to switch to the high magnification side,
The threshold value must be set and controlled while taking into account the signal shape that changes depending on the reflectance of the sample.

If the range of the focal position is out of the range due to the signal on the low magnification side, the position cannot be recognized.
Usually, it is necessary to return to the origin once and perform the search again, which also causes a great loss of time.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances. It is an object of the present invention to provide an easy-to-adjust and easy-to-control method, a wide range of focus detection, and a case where positioning is impossible. It is an object of the present invention to provide a focus detection device capable of guiding a focus direction without using a focus detection device.

[0016]

According to the first aspect of the present invention,
First light detection means for irradiating the surface to be measured with light from a light source and outputting a signal corresponding to the amount of light reflected from the surface to be measured;
A focus detection system comprising: a light receiving optical system including an objective lens for guiding the reflected light to the light detecting means; and a signal processing system for determining a position of the surface to be measured based on an output signal of the light detecting means. In the apparatus, an optical axis distance from the surface to be measured is disposed at a short position and a long position with respect to the first light detecting means, respectively, and a signal corresponding to the amount of reflected light from the surface to be measured is output. A plurality of second light detecting means are further provided, and the signal processing system makes a determination based on output signals of the first light detecting means and the plurality of second light detecting means.

As a result of such a configuration, even when the deviation from the in-focus position is large and the attendance signal cannot be obtained with the first light detecting means, the measured light is measured by one of the plurality of second light detecting means. Light from the surface is received and a signal is output. At this time, the direction of the defocus at that time is determined by the second light detecting means from which the signal is obtained, depending on whether the optical axis distance to the surface to be measured is shorter or longer than the first light detecting means. Is recognized. Therefore, while the adjustment is easy and the control is simplified, the range in which the focus can be detected can be widened, and the focus can be guided in the focus direction without becoming unrecognizable.

According to a second aspect of the present invention, there is provided a first light detecting means for irradiating light from a light source to a surface to be measured and outputting a signal corresponding to the amount of light reflected from the surface to be measured, A light receiving optical system including an objective lens for guiding the reflected light to the means, and a focus detection device having a signal processing system for determining a position of the surface to be measured based on an output signal of the light detection means, It is installed between the light receiving optical system and the first light detecting means so as to block a part of the reflected light guided to the first light detecting means, and outputs a signal corresponding to the amount of the blocked reflected light. And a signal processing system that makes a determination based on output signals of the first light detecting means and the second light detecting means.

As a result of such a configuration, while the configuration of the second light detecting means is further simplified, the adjustment and the control can be simplified, the range in which the focus can be detected is wide, and the position cannot be recognized. Can be guided in the direction of the focal point without being moved.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the signal processing system includes the first signal processing system.
Based on the output signals of the light detection means and the second light detection means,
It is characterized in that a range in which focus detection is performed is defined. As a result of such a configuration, in addition to the operation of the first or second aspect of the present invention, the focus detection operation can be performed more reliably and more quickly.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) Hereinafter, a focus detection device according to a first embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows the structure, and reference numeral 50 denotes a laser emitting means as a light source. This laser emitting means 5
The laser beam emitted from the collimator lens 51
After the light beam is converted into a parallel light beam, half of the light beam is shielded by a shielding plate 52 disposed in the optical path, and the other half of the light beam is condensed by a condenser lens 53. And is incident on the polarization beam splitter 54.

The light reflected by the polarizing beam splitter 54 passes through an imaging lens 55, a quarter-wave plate 56, and an objective lens 57, and irradiates a surface 58 to be measured. The reflected light from the surface to be measured 58 is again transmitted to the objective lens 57, 1/4
After passing through the wavelength plate 56 and the imaging lens 55, the light passes through the polarization beam splitter 54, and the optical path is split into two by the beam splitter 59. The transmitted light is collected on the two-divided light receiving element 60. The two-divided light receiving element 60 includes two photoelectric conversion units C and D, and these photoelectric conversion units C and D output voltage signals corresponding to the amounts of received light. The two-divided light receiving element 60 is disposed at an image forming position by the image forming lens 55 (or a position conjugate with the image forming lens 55).

On the other hand, 90 ° by the beam splitter 59
The bent light is irradiated onto the light receiving element 62 including the photoelectric conversion unit. Further, a light receiving element 61 including a photoelectric conversion unit similar to the light receiving element 62 is formed at a position opposed to the beam splitter 59 therebetween. Each light receiving element 6 at this time
The positional relationship between the optical axes 1 and 62 in the optical axis direction is such that α>γ> β.

Output signals from the three light receiving elements 60, 61, and 62 are sent to a signal processing system 63, and the signal processing system 63 performs an operation to correspond to the displacement of the surface 58 to be measured. A displacement signal can be obtained.

The signal processing system 63 performs a predetermined operation on each of the input signals, specifically, a difference / sum operation of the two signals obtained by the two-division light-receiving element 60, and a light-receiving element 61. , 62, the front pin at the surface 58 to be measured,
An operation for recognizing the position of the rear pin is executed, and the surface to be measured 58
A displacement signal corresponding to the surface shape of the object is calculated, and focusing control for the measured surface 58 is performed based on the calculated displacement signal.

In the above configuration, by moving the surface to be measured in the optical axis direction, the surface to be measured 6 at a position farther from the original position of the surface to be measured 58 shown in FIG.
4 and the surface 65 to be measured at a close position will be considered.

In the case of the measured surface 64 distant, the measured surface 6
The reflected light from 4 follows the path indicated by reference numeral 67 in the figure,
The light is split into two by the beam splitter 59, one of which is transmitted, and is irradiated on the two-divided light receiving element 60. However, since this light beam is spread, the two-part light receiving element 60
, The possibility of receiving light is reduced. On the other hand, the light beam reflected by the beam splitter 59 irradiates the light receiving element 61 and is detected as a signal 70 in FIG.

In the case of the measured surface 65 approached, the reflected light from the measured surface 65 follows the path indicated by reference numeral 66 in the drawing, is split into two by the beam splitter 59, and one of the two is transmitted, and The light is applied to the splitting element 60. However, as described above, since this light beam spreads, the possibility that the light beam can be received by the two-part light receiving element 60 is low. on the other hand,
The light reflected by the beam splitter 59 is received by the light receiving element 62.
And is detected as a signal 71 in FIG.

As described above, by changing the distance between the position of the surface to be measured and the objective lens 57, the signals 68 and 69 are generated by the two-part light receiving element 60 as shown in FIG.
And a signal 71 by the light receiving element 62.
Can be obtained respectively.

The actually obtained signal is processed by the signal processing system 63 as shown in FIG. That is, a focus detection signal 72 calculated based on the signal obtained by the two-divided light receiving element 60 and a signal 73 that allows recognition of the actual position of the measured surface relative to the measured surface 58. On the -V side,
The signal 74 is processed to be on the + V side.

According to the focus detection signal shown in FIG. 4 obtained by the signal processing system 63, the surface to be measured is moved in the optical axis direction, or the beam splitter 59, the two-part light receiving element 60, and the light receiving elements 61 and 62 are used. Is moved in the direction of the optical axis, and the signal 73 or 74 is obtained to recognize the actual position of the surface to be measured so that the signal 72 is obtained. Within 0
This is to detect points.

In this manner, the focus detectable range which can be obtained only by the signal output from the two-divided light receiving element 60 can be set wide. In particular, a high-magnification objective lens having a narrow focus detectable range can be used. Since the range can be set sufficiently wide even in the case of use, it is possible to accurately focus even on a surface to be measured having a large step or inclination, which is usually weak.

Further, since the direction of the deviation from the in-focus position can be recognized based on the state of the output signals from the light receiving elements 61 and 62, the position can not be recognized.
The focusing operation can be performed quickly.

Further, since the light receiving elements 61 and 62 merely measure the amount of light, there is no need for strict position adjustment, which facilitates assembly and is advantageous in terms of cost. Further, by setting the positions of the light receiving elements 61 and 62 so as to change the distances β and α in FIG. 1, the signals 73 and 74 obtained by the signal processing system 63 also change. Can also respond.

(Second Embodiment) Hereinafter, a focus detection device according to a second embodiment of the present invention will be described with reference to the drawings.

FIG. 5 shows the structure, which is basically the same as that shown in FIG. 1 above, and the same parts are denoted by the same reference numerals and description thereof is omitted. In this figure, the polarization beam splitter 54 shown in FIG.
The polarization beam splitter 59 and the light receiving elements 61 and 62 disposed between the light receiving element 60 and the light receiving element 60 are simplified. It is arranged so that.

With this configuration, when the measured surface 64 is located farther from the objective lens 57 than the original measured surface 58 as shown in FIG. Following such a path, the light is irradiated on the light receiving element 75 and detected as a signal 78 in FIG.

On the other hand, when the measured surface 65 is located closer to the objective lens 57 than the original measured surface 58, the reflected light follows the path indicated by reference numeral 76 in FIG.
The light is emitted only to the divided light receiving element 60. However, as the distance between the surface 58 to be measured and the objective lens 57 increases, the component of the signal 78 disappears like the signal 69 in FIG.

The signal obtained in FIG.
To obtain a signal as shown in FIG. That is, 2
The focus detection signal 72 is calculated based on the signals 68 and 69 obtained by the divided light receiving element 60, and the signal 78 obtained by the light receiving element 75 is processed to the -V side in accordance with the signal 72, and the focus detection signal is processed. 79 are obtained.

According to the focus detection signal 72 or 79 shown in FIG. 8 obtained by the signal processing system 63 in this way, the surface to be measured is moved in the optical axis direction, or the focus including the two-part light receiving element 60 and the light receiving element 75 is used. The unit side of the detection device is moved in the direction of the optical axis, and when the surface to be measured is located farther from the objective lens 57 than the original position range, the signal 79 is obtained by recognizing the signal 79, and the signal 72 is recognized. The above-mentioned movement is executed until it becomes possible to detect the zero point in the signal 72.

When the surface to be measured is located closer to the objective lens 57 than the original position range, there is no signal to be obtained. It waits until it is obtained, and at the time when it is obtained, the zero point is detected in the signal 72.

By adopting such a configuration and operation, it is possible to greatly simplify the configuration of the apparatus while obtaining the same operation and effects as those of the first embodiment, thereby improving the assemblability. In addition, since the number of man-hours required for adjustment is small, it is more advantageous in terms of cost.

(Third Embodiment) Next, a third embodiment of the present invention will be described.
An embodiment will be described with reference to the drawings. In addition.
The configuration itself of the device is the same as that shown in FIG. 1 or FIG. 5, and illustration and description thereof are omitted.

The principle of the operation performed in the signal processing system 63 will be described with reference to FIG. That is, in the signal processing system 63, as shown in FIG. 9, a signal 80 of a constant voltage is set in consideration of a margin such as voltage noise, and the signal 80 is set within a range of a width X defined by an intersection of the signal 80 and the signals 70 and 71. Only the focus detection operation is performed. Here, the signals 70 and 71 also have an intersection with the signal 80 on the focusing side. However, at the intersection on the focusing side, the signals 68 and 69 also exist at the same time. The intersection width X is detected based on the presence or absence of.

By performing such processing in the signal processing system 63, in addition to the operation and effect described in the first and second embodiments, the detection signal cannot be sensed by defining the range. Since there is no need to search for a signal, it is possible to execute focus detection reliably and quickly.

[0047]

According to the first aspect of the present invention, even if the deviation from the in-focus position is large and the attending signal cannot be obtained with the first light detecting means, any one of the plurality of second light detecting means can be used. As a result, light from the surface to be measured is received, and a signal is output. At this time, the direction of the defocus at that time is determined by the second light detecting means from which the signal is obtained, depending on whether the optical axis distance to the surface to be measured is shorter or longer than the first light detecting means. Is recognized. Therefore, while the adjustment is easy and the control is simplified, the range in which the focus can be detected can be widened, and the focus can be guided in the focus direction without becoming unrecognizable.

According to the second aspect of the present invention, while the structure of the second light detecting means is further simplified, the adjustment and the control can be simplified, the range in which the focus can be detected is wide, and the position cannot be recognized. It can be guided in the focus direction without being affected. According to the third aspect of the invention, in addition to the effects of the first or second aspect of the invention, it is possible to execute the focus detection operation reliably and more quickly.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a focus detection device according to a first embodiment of the present invention.

FIG. 2 is a view showing a change of a light beam when a surface to be measured is moved in an optical axis direction by the apparatus of FIG.

FIG. 3 is a diagram showing a signal detected from each light receiving element according to the embodiment.

FIG. 4 is a view showing a control signal obtained from a detection signal according to the embodiment.

FIG. 5 is a diagram showing a configuration of a focus detection device according to a second embodiment of the present invention.

FIG. 6 is a diagram showing a change in a light beam when the surface to be measured is moved in the optical axis direction by the apparatus in FIG.

FIG. 7 is a diagram showing a signal detected from each light receiving element according to the embodiment.

FIG. 8 is a diagram showing a control signal obtained from a detection signal according to the embodiment.

FIG. 9 is a diagram illustrating an operation of a signal processing system according to a third embodiment of the present invention.

FIG. 10 is a diagram illustrating a configuration of a conventional focus detection device.

[Explanation of symbols]

 Reference Signs List 50 laser emitting means 51 collimator lens 52 shielding plate 53 condensing lens 54 polarizing beam splitter 55 imaging lens 56 quarter-wave plate 57 objective lens 58 measured surface 59 beam splitter 60 Split light receiving element 61 ... Light receiving element 62 ... Light receiving element 63 ... Signal processing system 75 ... Light receiving element

Claims (3)

[Claims] 1. A first light detecting means for irradiating light from a light source onto a surface to be measured and outputting a signal corresponding to the amount of reflected light from the surface to be measured, and applying the reflected light to the light detecting means. A focus detection device having a light receiving optical system including an objective lens for guiding, and a signal processing system for determining a position of the surface to be measured based on an output signal of the light detection means; A plurality of second light detecting means, each having an optical axis distance disposed at a short position and a long position with respect to the first light detecting means and outputting a signal corresponding to the amount of reflected light from the measured surface, The focus detection device further comprises: the signal processing system makes a determination based on output signals of the first light detection means and the plurality of second light detection means. 2. A first light detecting means for irradiating light from a light source onto a surface to be measured and outputting a signal corresponding to the amount of reflected light from the surface to be measured, and applying the reflected light to the light detecting means. A focus detection device comprising: a light receiving optical system including an objective lens for guiding the light; and a signal processing system for determining a position of the surface to be measured based on an output signal of the light detecting means. A second light detection unit that is provided between the first light detection unit and shields a part of the reflected light guided to the first light detection unit, and outputs a signal corresponding to the amount of the shielded reflected light; A focus detection device, further comprising: a signal processing system, wherein the signal processing system makes a determination based on output signals of the first light detection means and the second light detection means. 3. The signal processing system according to claim 1, wherein a range in which focus detection is performed is defined based on output signals of the first light detecting means and the second light detecting means. Focus detection device.