JPH0563773B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a non-contact automatic focusing method suitable for focusing on the surface of a transparent body.

<Conventional technology> For objects with various sizes, shapes, and physical properties,
Optically contactless 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 recent speed of technological progress, it has become increasingly necessary to perform optical focus positioning even on transparent objects that are difficult to detect optically. Moreover, since a transparent body does not have an image on its surface, it is impossible to deal with transparent bodies using the image processing techniques described above.

Therefore, the inventor of the present invention conducted extensive research based on the above proposal and developed a method that enables accurate and instantaneous focus positioning even for such transparent objects that are optically difficult to detect.

<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
After being refracted by an objective lens, it is irradiated onto a transparent body, and the measurement light beam reflected on the surface of the transparent body is
After being refracted by the objective lens, the light is received by an optical position detector, and at least the distance between the transparent body and the objective lens is adjusted by a focus positioning mechanism corresponding to the position signal from the optical position detector. By this, the measurement light beam is automatically focused on the surface of the transparent body, and by moving the movable mirror in parallel to the side opposite to the transparent body, the measurement light beam reflected by the fixed mirror is focused on the outer periphery of the objective lens. The measurement light beam is refracted on the transparent body side, and the measurement light beam is irradiated onto the transparent body at a large irradiation angle, and the measurement light beam that is reflected on a surface other than the surface of the transparent body is reflected in a direction that cannot be incident on the objective lens.

<Operation> By moving the movable mirror in parallel toward the opposite side of the transparent body, the reflection point of the measurement light beam on the fixed mirror is changed to the side opposite to the optical axis, and the measurement light beam is separated from the optical axis. When the measurement light beam moves away from the optical axis, the measurement light beam is refracted at the outer peripheral side of the objective lens and is irradiated onto the transparent body at a large irradiation angle with respect to the optical axis. Then, other than the surface of the transparent body (for example, the back of the transparent body, the opaque body bonded to the back side of the transparent body, the opaque body provided inside the transparent body, the opaque body spaced apart on the back side of the transparent body) The measurement light beam reflected by the object lens is reflected in a direction in which it cannot enter the objective lens.

<Embodiments> Preferred embodiments of the present invention will be described below based on the drawings.

First Embodiment FIGS. 1 to 5 are diagrams showing a first embodiment of the present invention.

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 employed. 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 and 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 at 1
7, and is received by the upper photosensor 11a. Then, the position signal is sent to the focus positioning mechanism 3, and the focus positioning mechanism 3 moves the object 4 closer to the optical mechanism 2 side.
As shown in the figure, 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 around the same wavelength (6328 Å) as the polarized He-Ne laser beam, thereby improving noise resistance.

An embodiment of the present invention using the above-mentioned apparatus will be further explained based on 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.

The transparent body (object) 4 has its front surface 4a as its back surface 4.
Reflection is performed at both b and b. In other words, the measurement light beam d irradiated at a certain irradiation angle θ is once divided into a measurement light beam i, which is refracted and transmitted into the transparent body 4, and a measurement light beam e, which is reflected by the surface 4a. On the other hand, the measurement light beam i that has passed through the transparent body 4 is further divided into a measurement light beam j that passes toward the back surface 4b and a measurement light beam k that is reflected by the back surface 4b. Therefore, both the measurement light flux e reflected on the front surface 4a and the measurement light flux k reflected on the back surface 4b are refracted by the objective lens 8 and sensed by the optical position detector 11. See figure]. surface 4
If the measuring luminous flux e from a is stronger, then the surface 4
A is in focus, but depending on the situation on the back side 4b,
The measurement light flux k from the back surface 4b may be stronger, and in that case, the optical position detector 11 and the focus alignment mechanism 3 are controlled by the measurement light flux k reflected from the back surface 4b, and the focus is focused on the back surface 4b. There is a risk that they will match.

Therefore, in such a case, by moving the movable mirror 6 in parallel to the side A opposite to the transparent body, the measurement light beam c reflected by the fixed mirror 7 is refracted on the outer peripheral side of the objective lens 8, and the measurement light beam d is It is sufficient to irradiate the transparent body 4 with a large irradiation angle θ1. Then, the reflection angles of both the measurement light beams e and k reflected on the front surface 4a and the back surface 4b become large,
The measurement light beam k reflected from the back surface 4b is reflected in a direction in which it cannot enter the objective lens 8.
Therefore, only the measurement light beam e reflected by the surface 4a is refracted by the objective lens 8, and it becomes possible to operate the focus positioning mechanism 3 by this measurement light beam e. Incidentally, since the measurement light flux e from the surface 4a is reflected light from the surface 4a of the transparent body 4, the amount of light is small, but if it is electrically amplified by the optical position detector 11, there will be no problem.

In other words, in this embodiment, the measurement light flux k that is reflected off a surface other than the surface 4a of the transparent body 4 that is actually desired to be focused is
This is to adjust the irradiation angle θ of the measurement light beam so as to reflect it in a direction where it cannot enter the objective lens 8, and it is also applied when an opaque body or the like is attached or separated from the back surface 4b of the transparent body 4. can.

Second Embodiment FIGS. 6 and 7 are diagrams showing a second embodiment of the present invention. In this embodiment, a case where an opaque body 18 exists inside a transparent body 4 will be described.
In this case, the measurement light flux l reflected by the opaque body 18
is stronger than the measurement light beam e reflected by the surface 4a, so the optical position detector 11 and the focus positioning mechanism 3 always focus on the surface of the opaque body 18 (see FIG. 6). . Then, the surface 4 of the transparent body 4 where you want to actually focus
I can no longer focus on a. Even in such a case, by moving the movable mirror 6 in parallel to the side A away from the object and setting the measurement light beam d at a large irradiation angle θ1, reflection of the measurement light beam d on the opaque body 18 can be avoided. [See Figure 7]. Therefore,
It becomes possible to operate the focus positioning mechanism 3 only by the measurement light beam e reflected on the surface 4a of the transparent body 4, and to focus on the surface 4a of the transparent body 4. As an example of application of this embodiment, it is most suitable, for example, when an electronic circuit (semiconductor, etc.) is enclosed within a transparent substrate. Furthermore, not only when the opaque body 18 exists inside the transparent body 4, but also when the opaque body 18 or the like is bonded to or placed apart from the back surface 4b of the transparent body 4 as described above, the opaque body 18 can be measured. If interference (irradiation) with the light beam d is avoided, it is possible to focus only on the surface 4a of the transparent body 4, as in the present embodiment.

<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 opposite side of the transparent object, the irradiation angle of the measurement light beam is increased, so that the measurement light beam reflected off the surface of the transparent object is reflected in a direction that cannot be incident on the objective lens, and This has the effect of allowing you to focus only on the surface.

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 the first embodiment of the present invention, FIG. 2 is a schematic explanatory diagram corresponding to FIG. 1 showing a state in which the object is shifted toward the optical mechanism, 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;
5 and 5 are enlarged explanatory views showing a first embodiment of the present invention, and FIGS. 6 and 7 are enlarged explanatory views showing a second embodiment of the invention, respectively. 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, p1...focal point,
θ, θ1...Irradiation angle, a-l...Measurement light 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. After being refracted, it is irradiated towards a transparent body, and the measurement light beam reflected on the surface of the transparent body is refracted by an objective lens and then received by an optical position detector, and the position from the optical position detector is determined. The focus positioning mechanism corresponding to the signal automatically focuses the measurement light beam onto the surface of the transparent body by adjusting at least the distance between the transparent body and the objective lens, the movable By moving the mirror in parallel toward the opposite side of the transparent object, the measurement light beam reflected by the fixed mirror is refracted at the outer circumferential side of the objective lens, and the measurement light beam is irradiated onto the transparent object at a large irradiation angle. A non-contact automatic focus positioning method characterized by reflecting a measurement light beam reflected off a surface other than the surface in a direction where it cannot enter an objective lens.