JPH0563772B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a non-contact automatic focus positioning method suitable for focus positioning when a transparent body is involved.

<Conventional technology> For objects with various sizes, shapes, and physical properties,
Optically non-contact focusing is a technically difficult problem. However, because there are so many uses for this non-contact focusing technology, it is still a subject that many scholars are researching.

As a conventional focus positioning technique, there is an image processing technique using a computer.
There are many problems such as the large size of the device and the slow focus positioning speed due to image scanning, so it cannot be said to be very practical.

Therefore, in order to meet the above-mentioned demands, the present inventor has conducted intensive research over many years and has developed a non-contact automatic positioning device (patent application filed in 1983-
214773).

<Problems to be solved by the invention> However, with the speed of technological progress, it is increasingly necessary to optically align the focus using a transparent body that is difficult to detect optically. It's here.

Therefore, the present inventor has conducted extensive research based on the previous proposal, and has developed a method that allows accurate and instantaneous focus positioning even when such a transparent object that is optically difficult to detect is interposed.

<Means for Solving the Problems> In order to achieve the above object, the non-contact automatic focusing method according to the present invention uses polarized He as a measurement light beam emitted parallel to the optical axis of an optical mechanism.
-The Ne laser beam is reflected by a movable mirror that can be moved in parallel while maintaining an inclination angle of 45 degrees with respect to the optical axis, and the measurement light beam reflected by the movable mirror is reflected at an inclination angle of 45 degrees with respect to the optical axis. The measurement light beam reflected by the fixed mirror is reflected by the fixed mirror arranged at
It is refracted by an objective lens, then irradiated onto an opaque body through a transparent body, and the measurement light beam reflected on the surface of the opaque body is refracted by the objective lens and then received by an optical position detector. The measurement light beam is automatically focused onto the surface of the opaque body by adjusting at least the distance between the opaque body and the objective lens using a focus positioning mechanism corresponding to the position signal from the optical position detector. By moving the movable mirror in parallel toward the opaque body, the measurement light beam reflected by the fixed mirror is refracted toward the center of the objective lens, and the measurement light beam approaches the optical axis. Even at a small irradiation angle, the intervening transparent and opaque bodies are irradiated.

<Operation> By moving the movable mirror in parallel toward the opaque body, the reflection point of the measurement light beam on the fixed mirror is changed toward the optical axis side, and the measurement light beam approaches the optical axis. When the measurement light beam approaches the optical axis, the measurement light beam is refracted at the center of the objective lens, and is irradiated onto the intervening transparent and opaque bodies even at a small irradiation angle with respect to the optical axis. Then, since the measurement light flux is close to the optical axis, the measurement light flux is always irradiated onto the opaque body, even though there is a transparent body, unless the opaque body is extremely small. When the measurement light beam is irradiated onto an opaque object, the measurement light beam reflected from the surface of the opaque object is stronger than the measurement light beam reflected from the surface of the transparent object, so the focus must always be on the surface of the opaque object. becomes.

Embodiments Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

First, the basic structure of an apparatus for carrying out the present invention will be explained based on FIGS. 1 to 3.
Reference numeral 1 indicates a laser mechanism, 2 an optical mechanism (encircled by a two-dot chain line in the figure), 3 a focus positioning mechanism, and 4 an object.

The laser mechanism 1 emits polarized light He as the measurement light flux a.
-Ne laser beam, that is, a polarized He--Ne laser beam, is emitted parallel to the optical axis 5 of optical mechanism 2, which will be described later.

The optical mechanism 2 includes a movable mirror 6, a fixed mirror 7,
Objective lens 8, imaging lens 9, magnifying lens 10,
An optical position detector 11 is provided. The movable mirror 6 receives the measurement light beam a emitted from the laser mechanism 1.
can be reflected in a perpendicular direction while moving parallel to the optical axis 5. The fixed mirror 7 is a half mirror that reflects the measurement light beam b reflected by the movable mirror 6 at right angles again to form a measurement light beam c parallel to the optical axis 5. The reflection point 12 on the fixed mirror 7 changes depending on the parallel movement position of the movable mirror 6, and the measurement light beam c reflected from the fixed mirror 7 changes depending on the position of the reflection point 12 on the fixed mirror 7. can approach and move away from the optical axis 5.

Next, the measurement light beam c reflected by the fixed mirror 7
is refracted by the objective lens 8 and then irradiated onto the object 4, becoming a measuring light beam d whose focal point p1 coincides with the surface 4a. The irradiation angle θ of the measurement light beam d onto the object 4 is determined according to the distance of the measurement light beam c from the optical axis 5. In other words, when the measurement light beam c reflected by the fixed mirror 7 is away from the optical axis 5, the measurement light beam c is refracted at the outer peripheral side of the objective lens 8, so that it is irradiated onto the object 4 even at a large irradiation angle θ. be done. On the other hand, when the measurement light beam c is close to the optical axis 5, the measurement light beam c is refracted toward the center of the objective lens 8, so that it is irradiated onto the object 4 even at a small irradiation angle θ.

The measurement light beam e reflected at the same reflection angle as the irradiation angle θ on the surface 4a of the object 4 is refracted by the objective lens 8 to become a measurement light beam f parallel to the optical axis 5. This measurement light flux f is further refracted by the imaging lens 9 to become a measurement light flux g, and the optical axis 5
It is guided to the magnifying lens 10 via the upper reimaging point p2. Then, the measurement light flux g is this magnifying lens 10
The light beam is refracted at , becomes a measurement light beam h, and is received by the two-split photosensors 11a and 11b of the optical position detector 11.

As this optical position detector 11, a semiconductor optical position detector (PSD) was adopted. This semiconductor optical position detector (PSD) can obtain a position signal that includes position information of incident light without scanning the image, and has higher resolution than solid-state imaging devices such as CCD and MOS. A high sampling grade can be obtained. The optical position detector 11 is electrically connected to the focus alignment mechanism 3, and the optical position detector 11 receives a position signal indicating which photosensor 11a or 11b receives the measurement luminous flux h. It is designed to be sent to the focus positioning mechanism 3. Photo sensor 1
1a transmits a signal for reducing the distance between the object 4 and the objective lens 8 to the focus positioning mechanism 3, and the photosensor 11b transmits a position signal for increasing the distance.

As the focus positioning mechanism 3, a ``servo mechanism'' with an extremely fast operating speed, in which a motor is driven by a servo circuit, is adopted. This focus positioning mechanism 3 is connected to the object 4,
The distance between the object 4 and the objective lens 8 is adjusted according to the position signal from the optical position detector 11, and the distance between the object 4 and the objective lens 8 is adjusted.
The focal point p1 of the measurement light beam d is made to coincide with the surface 4a. In addition, this focus positioning mechanism 3
The objective lens 8 (or the entire optical mechanism 2) can be moved, or both the object 4 and the objective lens 8 (or the entire optical mechanism 2) can be moved.

A focused state [see Fig. 1] A state in which the focal point p1 of the measurement light beam d matches the surface 4a of the object 4 is a focused state, and in this state, the object 4 The measurement luminous flux h reflected from the photosensors 11a, 1
The light is received at a neutral position p3 (that is, a balanced position) of 1b, and the focus positioning mechanism 3 is not activated.

A state in which the object is approaching the optical mechanism (see Figure 2). When the object 4 has moved toward the optical mechanism 2 and is out of focus, the measurement light beam d refracted by the objective lens 8 becomes It is reflected at a reflection point 14 below the optical axis 5 on the surface 4a of the object 4, passes through the objective lens 8 and the imaging lens 9, and then returns to the previous re-imaging point p2.
It passes through the re-imaging point 15 which is further ahead than the magnifying lens 1.
0 passing through the outer peripheral side of the lower photo sensor 11
The light is received at b. Then, the position signal is sent to the focus alignment mechanism 3, which moves the object 4 away from the optical mechanism 2, and when the measurement light beam h reaches the neutral position p3 of the photosensors 11a, 11b, the focus alignment mechanism 3 moves the object 4 away from the optical mechanism 2. 3 stops. Therefore, as shown in FIG. 1, the focal point p1 of the measurement light beam d is focused on the surface 4a of the object 4.

A state in which the object is moving away from the optical mechanism (see Figure 3).Contrary to the above, when the object 4 is moving away from the optical mechanism 2 and the surface 4a is deviated from the focal point p1, the objective lens 8 The measurement light beam d refracted by the object 4 is reflected at a reflection point 16 above the optical axis 5 on the surface 4a of the object 4, and is directly transferred to the objective lens 8, the imaging lens 9, the magnifying lens 10, and then re-imaging the near side. The light passes through point 17 and is received by the upper photosensor 11a. Then, the position signal is sent to the focus alignment mechanism 3, and the focus alignment mechanism 3 moves the object 4 closer to the optical mechanism 2,
As shown in FIG. 1, the focal position of the measurement light beam d can be adjusted.

In this way, the object 4 is at the focal point p of the objective lens 8.
Even if it deviates from 1, it can be automatically corrected and adjusted, and the focal point p1 of the measurement light beam d can be perfectly aligned with the surface 4a of the object 4. Furthermore, even if the object 4 is tilted with respect to the optical axis 5, the optical position detector 11 and the focus positioning mechanism 3 can be operated by the diffusely reflected light from the surface 4a of the object 4. There is no problem because it can be done. In addition, in the above basic structure, the fixed mirror 7
Although a half mirror is used as the mirror, a dichroic mirror, laser mirror, or other mirror may also be used. In addition, although a semiconductor optical position detector (PSD) was adopted as the optical position detector 11, other optical position detectors, such as a photodiode (PD)
Similar effects can be expected even if other methods are adopted. Although a servo mechanism is used as the focus positioning mechanism 3, the same effect can be obtained with other mechanisms as long as they have the same operating speed as the servo mechanism. Furthermore, it is also possible to arrange a polarizing filter immediately in front of the optical position detector 11 to block incident light having the same wavelength (6328 Å) as the polarized He--Ne laser beam, thereby improving noise resistance.

The present invention using the above-mentioned apparatus will be further explained with reference to FIGS. 4 and 5. In addition, the same reference numerals are given to the parts common to the above-mentioned basic structure and the explanation, and only the objective lens 8 of the optical mechanism 2 and the vicinity of the object 4 are illustrated, and the illustration of the other parts is omitted. A case will be described in which there is a small opaque body (object 4) 20 inside the transparent body 19 and it is desired to focus on the surface of the small opaque body 20. Since the opaque body 20 is small, the irradiation angle θ
If the value is large, the measuring light beam d from the objective lens 8 will not hit, and the optical position detector 11 and the focus positioning mechanism 3 will be activated by the measuring light beam e reflected by the surface 19a of the transparent body 19, and the intervening transparent body 19 surface 1
9a becomes in focus, and the opaque body 20 cannot be focused (see FIG. 4).

Therefore, by moving the movable mirror 6 parallel to the object side B, the measurement light beam d is irradiated even at a small irradiation angle θ1 that approaches the optical axis 5 [5th
See figure]. Then, since the measurement light flux d is irradiated close to the optical axis 5, the measurement light flux d will hit the opaque body 20 unless the opaque body 20 is very small. Once the measurement light flux d hits the opaque body 20, the measurement light flux i reflected from the opaque body 20 is stronger than the measurement light flux e reflected from the surface 19a of the transparent body 19 (see FIG. 6). The optical position detector 11 and the focus positioning mechanism 3 are activated by the measurement light beam i reflected from the opaque body 20, and focus on the surface of the opaque body 20 (see FIG. 7). Furthermore, even if the thickness of the transparent body 19 is large, the focal position can be adjusted without any problem. Therefore, when focusing on the electronic circuit (semiconductor, etc.) encapsulated in a transparent substrate, when using this non-contact automatic focus positioning device in a microscope, it is necessary to use the slide glass and cover glass. This is suitable when focusing on the specimen itself as an object held between the two. Furthermore,
Not only when the opaque body 20 is present inside the transparent body 19, but also when the back surface 19 of the transparent body 19 is present as described above.
Even when an opaque body 20 or the like is arranged on the b side, the focus can be set toward the opaque body 20.

<Effects> The non-contact automatic focus positioning method according to the present invention has the contents as described above, and has the following features:
By moving the movable mirror in parallel toward the opaque object, the irradiation angle of the measurement light beam is reduced, so even if the focus needs to be adjusted to the opaque object through a transparent object, the focus can be aligned to the opaque object itself. be able to.

Since a polarized He-Ne laser beam is used as the measurement light beam, the light beam is narrower than other laser beams, and the focal spot is very small and does not spread out, so the position detection with the optical position detector is improved accordingly. This can be done with high precision (high resolution). This polarized light He−
Although the diameter of the condensing spot of the Ne laser beam depends on the magnification of the objective lens, it is very small, approximately 1 μ to 100 μ (that is, the focus positioning accuracy is high).

Further, according to the embodiment of the present invention, since the displacement of the measurement light beam is magnified by the magnifying lens,
Since even small displacements are accurately magnified without being overlooked, and the position is then detected by an optical position detector, highly accurate position detection can be achieved. Therefore, even in a situation where the distance between the objective lens and the object is large and the focus accuracy tends to decrease, highly accurate focus positioning can be achieved (that is, the focus positioning accuracy is high).

The semiconductor optical position detector (PSD) as an optical position detector only outputs the position of the center of gravity of the spot of the detected measurement light beam, so it is not affected by changes in the brightness distribution, and the brightness distribution on the surface of the object Focus positioning accuracy is not affected by (contrast) (that is, noise resistance and measurement reliability are high).

A semiconductor optical position detector (PSD) is used as the optical position detector, and a servo mechanism is used as the focus positioning mechanism, so the distance between the optical mechanism and the object can be adjusted with a quick movement of 10 mmsec on average. (that is, the focus positioning speed is fast).

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing the basic structure of an apparatus implementing an embodiment of the present invention, FIG. 2 is a schematic explanatory diagram corresponding to FIG. Figure 3 is a schematic explanatory diagram equivalent to Figure 1 showing a state in which the object is shifted toward the opposite side of the optical mechanism, Figure 4 is an enlarged explanatory diagram of a state where the irradiation angle is large, and Figure 5 shows a state where the irradiation angle is small. FIG. 6 is an enlarged view corresponding to FIG. 4, FIG. 6 is an enlarged view showing the arrowed part in FIG. 5, and FIG. 7 is an enlarged view equivalent to FIG. be. DESCRIPTION OF SYMBOLS 1... Laser mechanism, 2... Optical mechanism, 3... Focus alignment mechanism, 4... Target, 5... Optical axis, 6... Movable mirror, 7... Fixed mirror, 8... Objective lens, 9... Imaging lens, 11... Optical position detector, 20... Opaque body (object), p1... Focus, θ, θ1... Irradiation angle, a
~i...Measurement luminous flux.

Claims (1)

[Claims] 1. A polarized He-Ne laser beam as a measurement light beam emitted parallel to the optical axis of an optical mechanism is applied to a movable mirror that can be moved in parallel while maintaining an inclination angle of 45 degrees with respect to the optical axis. The measuring beam reflected by the movable mirror is reflected by a fixed mirror arranged at an angle of 45 degrees with respect to the optical axis, and the measuring beam reflected by the fixed mirror is reflected by an objective lens. The measurement light beam is refracted and then irradiated onto an opaque body through a transparent body, and the measurement light beam reflected on the surface of the opaque body is refracted by an objective lens and then received by an optical position detector. By adjusting at least the distance between the opaque body and the objective lens using a focus positioning mechanism corresponding to the position signal from the optical position detector, the measurement light beam is automatically focused on the surface of the opaque body. By moving the movable mirror in parallel toward the opaque body, the measurement light beam reflected by the fixed mirror is refracted toward the center of the objective lens, and the measurement light beam approaches the optical axis at a small irradiation angle. A non-contact automatic focus positioning method characterized by irradiating an intervening transparent body and an opaque body.