JPH0711583B2 - Optical object recognition device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical object recognition device that recognizes an object by detecting interruption of a light beam from a light emitter by a thin object such as a wafer with a light receiver.

(Prior Art) Conventionally, in a semiconductor exposure apparatus or the like, when one of a plurality of wafers stored in a cassette is taken out and set on an exposure stage, the wafer to be taken out of the cassette is detected. An optical object recognition device is used.

FIG. 6 shows the outline of a conventional optical object recognizing device, in which a light receiver 2 is arranged opposite to a light emitter 1 at a predetermined interval, and a light beam 3 emitted from the light emitter 1 is received by the light receiver 2. When a small object 4 impinges on the light beam 3 in a direction orthogonal to the optical axis of a wafer or the like,
Is detected so that the object 4 is recognized.

By the way, a semiconductor laser or a laser is often used as the light source of the light emitter 1 in such a conventional optical object recognition device because the diameter of the light beam 3 can be made small.

(Problems to be Solved by the Invention) However, in such conventional object recognition by a laser beam, when recognizing an object smaller than the diameter of the laser beam, a high resolution change of the received light amount cannot be obtained. ,
There was a problem that it was not possible to recognize minute objects with high accuracy.

For example, it is known that the emission surface of semiconductor lasers is elliptical.For such laser beams, the wafer to be detected is 0.6 m in the direction orthogonal to the optical axis.
Since it is a thin object such as about m, the object becomes smaller than the diameter of the laser beam, and even if the object crosses the laser beam, the laser beam to the photoreceiver cannot be completely blocked. For example, the amount of received light changes as shown in FIG. 7 with respect to the displacement in the direction orthogonal to, and the position of the object cannot be accurately determined from the change in the amount of received light.

On the other hand, it may be possible to use LEDs as the light source of the light emitter, but since the distribution of the LED emission brightness is a radial distribution with maximum brightness in the optical axis direction, it is difficult to reduce the parallelization of the light beam. Particularly, when the distance between the light emitter and the light receiver is long, the light beam is diffused, and it is difficult to recognize an object such as a minute wafer in the direction orthogonal to the optical axis and accurately determine its position.

(Means for Solving the Problems) The present invention has been made in view of the above-mentioned conventional problems. When the object such as a minute wafer crosses the light beam in a direction orthogonal to the optical axis, An object of the present invention is to provide an optical object recognition device capable of reliably recognizing a minute object with high resolution from a change in light amount.

In order to achieve this object, in the present invention, the light emitting device,
A projection plate that converts a light beam from a light source such as a laser or an LED into a slit-shaped or spot-shaped projected image following the light source, and forms the projected image by focusing the light beam of the projected image at or near the object detection position. A first imaging lens is provided, while the light receiving device is provided with a second imaging lens for re-imaging the projection image formed at or near the object detection position on the light receiving element. Is.

(Operation) According to such a configuration of the present invention, a light flux from a light source such as a laser or an LED is converted into a projection image by a slit opening or a pinhole of the projection plate, and the first imaging lens is used to detect an object detection position or It is imaged as a slit image or a pinhole image in the space near it.

The slit image or pinhole image from the light emitter formed at or near the object detection position can be formed as a sufficiently small aerial image for a minute object in the direction orthogonal to the optical axis of the wafer or the like. Therefore, when the object crosses the optical axis in a direction orthogonal to each other, the recombined image of the light receiving element by the second coupling lens of the light receiver is completely blocked, and a sharp change in the amount of received light with high resolution can be obtained. .

(Embodiment) FIG. 1 is an explanatory diagram showing the basic configuration of the present invention.

In FIG. 1, reference numeral 5 denotes a light emitter, and the light emitted by the light emitter 5 is condensed at an image point 6 which is at the detection position of the minute object 8 or in the vicinity thereof, as will be described later. Then, for example, a slit image from the light emitter 5 is formed in the space of the image point 6. A light receiver 7 is arranged opposite to the light emitter 5 at a predetermined distance, and the light receiver 7 re-images the slit image formed at the image point 6 on the light receiving surface of the light receiving element having the built-in slit image.

FIG. 2 is an explanatory view showing a concrete embodiment of the light emitter 5 and the light receiver 7 of FIG.

In FIG. 2, the light emitting device 5 has a light emitting element 9 such as an LED or a semiconductor laser, and the light from the light emitting element 9 is condensed by the condenser lens 10 and irradiated on the projection plate 11. Projection board
In this embodiment, 11 has a slit opening 11a having a long side in a direction orthogonal to the paper surface, and the condenser lens 1
The projection slit image defined by the slit opening 11a is created by illuminating the light from the light emitting element 9 condensed at 0.

An aperture stop 12 is provided following the projection plate 11, and the aperture stop 12
The slit light flux from the projection plate 11 regulated by the above is incident on the first imaging lens 13. The first image forming lens 13 forms an image of the projection slit image from the projection plate 11 obtained through the aperture stop 12 in the space of the image point 6 determined by the focal length f.

On the other hand, the light receiving device 7 is provided with a second imaging lens 14 for re-imaging the projection slit image formed at the image point 6 by the first imaging lens 13 of the light emitting device 5 on the light receiving surface of the light receiving element 16. Between the second imaging lens 14 and the light receiving element 16, reflection is provided to prevent the reflected light generated when the minute object 8 is located at or near the image point 6 from entering the light receiving element 16. Light blocking slit
15 are arranged.

Next, the operation of the embodiment shown in FIG. 2 will be described.

First, in the light emitter 5, the light from the light emitting element 9 such as an LED or a semiconductor laser is condensed by the condenser lens 10 to illuminate the slit opening 11a of the projection plate 11. With the slit opening 11 of the projection plate 11
The projected slit image obtained as the transmitted light flux of a is the aperture stop 1
After the light flux is regulated by 2, the light enters the first image forming lens 13 and forms a projection slit image at the image point 6 by the first image forming lens 13. The size of the projection slit image formed on the image point 6 is determined by the arrangement position of the first image forming lens 13 and the focal length f of the lens, and at the sufficiently small slit image, that is, the image point 6. In addition, it is possible to form a projection slit image having a long side in the direction orthogonal to the paper surface and having a minute size of, for example, about 2 μ in the direction orthogonal to the optical axis.

Therefore, when a minute object 8 such as a minute wafer crosses the image point 6 where the projection slit image is formed or the vicinity thereof in the direction orthogonal to the optical axis, as shown by an arrow A, the image point 6
Since the slit image in is as small as about 2μ,
Even if the minute object 8 has a minute thickness of about 0.6 mm, such as a wafer, the image point 6 or its vicinity is indicated by an arrow A.
, The projection slit image formed at the image point 6 is completely blocked from entering the light receiver 7, and the second image forming lens 14
The re-imaging of the projected slit image on the light receiving element 16 due to is blocked.

That is, the light receiving element with respect to the displacement of the minute object 8 in the direction of arrow A
Assuming that the size of the light receiving output of 16 in the direction orthogonal to the optical axis of the minute object 8 is B, as shown in FIG. 3, there is a sharp change in the amount of light when the minute object 8 enters and leaves the image point 6. Obtained,
The passage or position of the minute object 8 can be determined with high resolution from the received light output of the light emitting element 16 that has received this change in the amount of light.

Next, the operation of the aperture stop 12 provided in the light emitter 5 will be described.

Now, as shown in FIG. 4, when detecting a minute object 8 that is not so long in the optical axis direction, as shown in FIG.
Even if the light flux from the projection plate 11 is not regulated by, the sharp change in the light amount as shown in FIG. 3 can be obtained with respect to the displacement of the minute object 8.

On the other hand, as shown in FIG.
In the case of detecting, when the light flux is not regulated by the aperture stop 12, the light flux for forming the projection slit image on the image point 6 by the first imaging lens 13 is as shown by the broken line 18. . When an object 17 long in the optical axis direction crosses in the direction of the arrow A in the image formation state on the image point 6 indicated by the broken line 18, as shown in the figure, the object 17 approaches the image point 6 and the length in the optical axis direction causes The light flux passing through the image point 6 to the light receiver is blocked at the end of the object 17, and the light flux to the light receiver is gradually blocked as indicated by the shaded area 19. For this reason, a steep change in the amount of light as shown in FIG. 3 cannot be obtained.

Therefore, when detecting the object 17 that is long in the optical axis direction, the aperture stop 12 is narrowed down as shown in the drawing, so that the first imaging lens
Reduce the opening diameter NA of 13. In this way, when the aperture stop 12 is narrowed down and the aperture diameter NA of the first imaging lens 13 is reduced, a projection slit image formed by focusing the light flux as shown by the solid line 20 is formed at the image point 6, The light flux from the image point 6 is also sufficiently narrowed depending on the aperture stop 12, and even if an object 17 which is long in the optical axis direction approaches the image point 6 as shown by the arrow A, the gradual amount of light as shown by the shaded portion 19 A sharp change in light quantity as shown in FIG. 3 can be obtained by blocking the light flux when the object 17 approaches the image point 6 or its vicinity without causing any change.

Therefore, when a long object is detected as the detection object instead of the short object in the optical axis direction, as shown in FIG. It is desirable to adjust the aperture.

Further, when a semiconductor laser, for example, is used as the light emitting element 9 serving as the light source of the light emitting device 5, the light emitting surface of the semiconductor laser has an elliptical shape, and the elliptical shape of the light emitting surface is long due to the influence of ambient temperature and the like. It fluctuates greatly in the axial direction. Therefore, by setting the long side of the opening slit portion 11a of the projection plate 11 so as to be in the minor axis direction of the elliptic emission surface of the semiconductor laser, even if the elliptical emission surface of the semiconductor laser changes, the shape of this emission surface It is possible to create a stable projected slit image without being affected by changes.

In the above embodiment, the slit opening 11a is provided in the projection plate 11 to form a projected slit image on the image point 6, but the projection plate 11 is provided with a pinhole. A spot image formed by a pinhole may be formed on the image point 6.

As described above, according to the present invention, the laser or LE
Light from a light source such as D illuminates a projection plate provided with slit-shaped or spot-shaped openings to create a projected image, and the projected slit image from the projection plate is placed at or near the object detection position by the first lens. On the other hand, the light receiver is provided with a second imaging lens for re-imaging the projected image by the light emitter formed at or near the object detection position on the light receiving element. Even if a minute object is perpendicular to the axis, the minute object crosses the image formation space of the projected image by the light emitter or its vicinity, so that the projected image is prevented from entering the light receiver. In short, it is possible to obtain a sharp light amount change with respect to the displacement of a minute object, and accurately recognize the object position from the light receiving output with high resolution obtained by the abrupt light amount change even for thin objects such as wafers, Not to mention the position of the object You can determine the size of your body at the same time.

As an effect peculiar to the embodiment, even if the object is minute in the direction perpendicular to the optical axis and is long in the optical axis direction at the same time, the light flux from the projection plate to the condenser lens is regulated by the aperture stop provided in the light emitter. By doing so, an object long in the optical axis direction can be accurately detected with a sharp change in the light amount without being affected by the size of the object in the optical axis direction.

[Brief description of drawings]

FIG. 1 is an explanatory view showing the basic structure of the present invention, FIG. 2 is an explanatory view showing a concrete embodiment of the present invention, and FIG. 3 is a displacement of the minute object obtained by the present invention across the optical axis. FIG. 4 is an explanatory view showing the function of the aperture stop, FIG. 6 is an explanatory view showing a conventional example, and FIG. 7 is a characteristic showing a light amount change in the conventional example. It is a figure. 5: Light emitting device 6: Image point (imaging position) 7: Light receiving device 8: Small object 9: Light emitting element 10: Condenser lens 11: Projection plate 12: Aperture stop 13: First imaging lens 14: Second Imaging lens 15: Reflected light shielding slit 16: Light receiving element 17: Object long in the optical axis direction

Claims (1)

[Claims] 1. A light-emitting device and a light-receiving device are arranged to face each other with a predetermined distance, and an object having a minute dimension in a direction orthogonal to an optical axis of light emitted from the light-emitting device is disposed between the light-emitting device and the light-receiving device. In the optical object recognition device which is arranged and recognizes the object by detecting the blocking of the light from the light emitter by the object by the light receiver, the light emitter has a slit-shaped or spot-shaped light beam from the light source. A projection plate for converting the projection image and a first image forming means for condensing the light flux of the projection image obtained from the projection plate to form the projection image in a space at or near the object detection position are provided. An optical object recognizing device, characterized in that the light receiver is provided with a second image forming means for re-forming a projected image formed in a space at or near the object detection position on a light receiving element.