Optical reflective edge or contrast sensor

A precision edge detection system and sensor assembly is provided that uses a reflection technique to provide an energy efficient device that can be achieved using a relatively small form factor. There is provided an optical reflective sensor assembly that includes a light source, an optical element positioned to collimate and focus light from the light source to generate a focused beam, and at least one photodetector positioned adjacent the light source. The at least one photodetector is configured to detect light from the focused beam that has been reflected by an object positioned opposite the light source.

TECHNICAL FIELD

The following relates to devices used to detect the edge of an object or a transition between surfaces of one or more objects, particularly to optical reflective sensor devices and systems, and methods for operating same.

BACKGROUND

Sensors for detecting the edge of an object are used in a variety of applications. For example, the position of an electrostatic chuck in a semiconductor processing system may need to be determined to instruct the processing system as to where the chuck is located in a chamber for positioning a robotic arm. More generally, edge detection sensors can be used to either find the edge of a static object using a moving detection probe, or detect the edge of an object that moves relative to the detection probe. Similarly, the detection probe can move over the object to find the edge or move towards the object to find the edge. In any of these variety of environments and scenarios, there may be ambient light, various objects and surfaces to track or account for, and space constraints that make edge detection difficult.

A common type of existing edge detection sensor is a through-beam sensor. In a through-beam sensor, light travels between a transceiver and a receiver, and when the light beam is blocked the sensor outputs a signal which can be correlated to an edge detection. Another common type of existing edge detection sensor is one that is based on digital images or video technology. In an image- or video-based edge detector, edge detection is performed using software techniques. Such existing sensors have been found to be sensitive to ambient light conditions, can be slow to respond, and can be expensive to purchase or manufacture.

There are applications, such as in semiconductor manufacturing processes that would benefit from a relatively small sensor that is energy efficient and responsive. It is therefore an object of the following to provide precision edge detection and sensing capabilities that addresses at least one of these considerations.

SUMMARY

The following provides a precision optical detection system and sensor assembly that uses a reflection technique to provide an energy efficient device that can be achieved using a relatively small form factor.

In one aspect, there is provided an optical reflective sensor assembly, comprising: a light source; an optical element positioned to collimate and focus light from the light source to generate a focused beam; and at least one photodetector positioned adjacent the light source, the at least one photodetector configured to detect light from the focused beam that has been reflected by an object positioned opposite the light source.

In another aspect, there is provided an optical reflective detection system, comprising: a substrate; at least one optical reflective sensor assembly supported at least in part by the substrate, each sensor assembly comprising: a light source; an optical element positioned to collimate and focus light from the light source to generate a focused beam; and at least one photodetector positioned adjacent the light source, the at least one photodetector configured to detect light from the focused beam that has been reflected by an object positioned opposite the light source; and a controller coupled to the at least one sensor assembly, the controller comprising a processor and memory, the memory storing computer executable instructions for operating the detection system to generate the focused beam and to detect reflected light.

In yet another aspect, there is provided a method for detecting a signature of reflected light, the signature being indicative of a surface or edge of an object, the method comprising: directing light from a light source through an optical element positioned to collimate and focus light from the light source to generate a focused beam; and detecting light from the focused beam that has been reflected by an object positioned opposite the light source, by at least one photodetector positioned adjacent the light source.

In an implementation, the light source can be positioned within an opening in the photodetector, wherein the optical element is positioned at an edge of the opening.

In an implementation, the assembly can further include a light insulating cap surrounding the light source, the light insulating cap supporting the optical element above the light source, and the light insulating cap being positioned adjacent the at least one photodetector.

In an implementation, the light source and the photodetector are coupled to a substrate. In an implementation, the light source and the photodetector are coupled to a controller of an optical detection system.

In an implementation, the at least one photodetector can be configured to detect rays of reflected light indicative of the presence of an edge of the object. The at least one photodetector can also be configured to detect rays of reflected light indicative of at least one surface of the object or multiple objects. The at least one photodetector can also be configured to detect a plurality of types of rays of reflected light, each corresponding to a signature. The assembly can also include a memory storing signatures for at least one type of ray of reflected light.

In an implementation, the sensor assembly can also include a light filter coupled to the photodetector. The sensor assembly can also include at least one lens positioned between the object and the photodetector to interact with the reflected light.

DETAILED DESCRIPTION

The following provides precision edge and contrast detection using an optical system that uses light reflectance. The system described herein can be used in any application or environment in which a spatial characteristic of an object is to be measured and is indicative of the presence or absence of an edge, and/or the presence or absence of contrasting surfaces, materials, objects, components, elevations, etc.

Turning now to the figures,FIG. 1Aillustrates a configuration for an optical reflective edge detection system10, also referred to herein as the “system”10. It can be appreciated that while the system10is exemplified herein as an “edge” detection system10, the system10may also be adapted and used to detect contrasts in materials and surfaces, i.e., where contrasts or “signatures” in the reflected light can be detected and identified. The term “edge” as used here may therefore refer to a physical edge of an object or the edge or boundary of a transition between contiguous materials or surfaces.

The system10includes one or more sensor assemblies12used to detect an edge or transition of, or associated with, an object14. In the example shown inFIG. 1A, a single sensor assembly12is shown, however, it will be appreciated that multiple sensor assemblies12may (and preferably would) be used to provide additional accuracy in the system10. The system10and the object14may be located within a chamber with a minimum of ambient light or may be located in another environment with more potential ambient light. The object14may be fixed to another object or supported on a surface of another object such as the above-noted chamber (not shown). In this example, the system10moves relative to the object14to find the edge of the object14. For example, the system10may be controlled to move towards the object14to determine an offset of the object14relative to a datum used to apply a processing step to the object14, locate and pick up the object14, etc.

The sensor assembly12includes a light source assembly16that emits a narrow light beam18, and a photodetector20for detecting reflected or scattered rays. The sensor assembly12(and any other sensor assembly12not shown) can be supported by and attached to a substrate22of the system10. The system10also includes a controller30that is coupled to the light source assembly16and the photodetector20of each sensor assembly12to cause the light source assembly16to generate the narrow beam of light18and to detect edges or transitions/contrasts based on what is detected at the photodetector20.

FIG. 1Billustrates the system10in a second position in which the narrow beam of light18has encountered the edge of the rightmost edge of the object14and creates a number of reflected/scattered rays24that are detected by the photodetector20. The system10can be calibrated to recognize a signature associated with the rays24, e.g., to distinguish from ambient light and/or any reflected or scattered rays caused by the beam of light18hitting an underlying surface or other object within the same environment (not shown). By having a relatively narrow beam18of light, a high precision of accuracy can be possible for the sensor assembly12. Further details of the light source assembly16that generates such a relatively narrow beam18of light is provided below.

FIG. 2Aillustrates a similar configuration for the system10as that shown inFIGS. 1A-1B, with a left-to-right movement of the substrate22over the object14for illustrative purposes. In this example, the object14includes a first surface15aand a contiguous second surface15bprovided by a pair of materials or components of the object14. InFIG. 2A, the beam of light18when interacting with the first surface15agenerates a first type of reflected or scattered ray24athat can be detected and identified by the photodetector20and controller30. This first type of ray24ais correlated to the first surface15ain order to detect when the beam18crosses the transition between the first surface15aand the second surface15b. This example can be applicable to scenarios wherein the object of interest is a portion of the object14that provides the first surface15aand therefore detecting the physical edge of the object14may not provide enough information for the desired objective. It can be appreciated that these principles also apply to objects or surfaces that are at different elevations or otherwise positioned at different distances from the sensor assembly16, whether they are differing materials or not.

Referring now toFIG. 2B, the system10has moved over the object14to a position wherein the beam18detects the second surface15b. In the example shown inFIG. 2B, a second type of reflected or scattered ray24b(denoted using a different type of dashed line inFIG. 2B) is detected by the photodetector20and controller30to indicate positionally where is the second surface15bassociated with the object14.

Further movement of the system10is illustrated inFIG. 2Cwherein the beam18encounters the edge of the object14causing a third type of reflected or scattered ray24cthat is denoted using the same dashed lines as those shown inFIG. 1Bfor illustrative purposes. The system10can detect both edges and contrasts associated with the object14. The system10can be calibrated to distinguish between the different types of rays24that are scattered or reflected by different surfaces and objects within the testing or detection environment in which the system10is being used by storing predetermined signatures. These signatures can be stored by the controller30for use in an application, e.g., during a calibration process as discussed in greater detail below.

FIG. 3Aillustrates another configuration for the system10in which the substrate22and thus the sensor assembly16are positionally static and detect the edge of a moving object14. For example, the configuration shown inFIG. 3Amay be used to control the movement of the object14into a chamber or station within a manufacturing process to align with another object or device (not shown). Also shown inFIG. 3Aby way of example is a light filter26positioned relative to the photodetector20to filter out ambient light. Otherwise, as illustrated inFIG. 3B, the system10may operate similar to what is shown inFIGS. 1 and 2by generating a relatively narrow beam of light18that generates reflected/scattered rays24when the beam18encounters an edge of the object14. As illustrated inFIG. 3B, the filter26can be configured to permit passage of the rays24while filtering other light that could otherwise degrade the precision of the detection capabilities of the system10.

As discussed above, the system10can, and often will, include multiple sensor assemblies12to increase the accuracy and precision of the system10.FIG. 4illustrates schematically a first light source assembly16agenerating a first narrow beam18aand a second light source assembly16bgenerating a second narrow beam18b. The beams18a,18bcan be used to detect multiple edges at the same time as illustrated inFIG. 4, e.g., to enable a two-dimensional positioning within the environment, or can be used to detect different objects14(not shown). The controller30can be configured to control both light source assemblies16a,16b.

Turning now toFIG. 5, the configuration for the system10shown therein illustrates the potential compact arrangement that can be achieved by using a reflective-type sensor assembly12. In this example, so long as reflected or scattered rays can reach the photodetector20when the beam18reflects off a surface or hits an edge, the system10can be positioned relatively close to the object14. It can be appreciated that the relative sizes and proportions for the components shown inFIG. 5are illustrative only and can be adapted to ensure that at least some of the reflected/scattered rays24reach the photodetector.

Detail concerning one example configuration for the sensor assembly12is shown inFIG. 6. In this example configuration, the light source assembly16includes a light source40positioned within a light insulating cap42or other walled structure having an open end to permit light generated by the light source40to pass therethrough. The light source40can be, for example, a light emitting diode (LED), a vertical-cavity surface-emitting laser (VCSEL), a superluminescent diode (SLED), or other similar type of light-emitting device. The light insulating cap42supports a lens44or other optical element that collimates the light emitted by the light source40to generate the relatively narrow beam18. It can be appreciated that the size and position of the light insulating cap42can be chosen to provide a suitable distance between the lens44and the light source40and to center the lens44relative to the light source. The lens44can be, for example, a micro aspheric, rod gradient or convex type lens to provide light collimation and focusing as illustrated herein. Optionally, the sensor assembly12can further include a lens50positioned between the object14and the photodetector20to disperse the rays24to improve the detection of the rays24by the photodetector20. This can increase the detection efficiency and insulate the sensor assembly12from the ambient light.

FIG. 7illustrates a configuration that is similar to that shown inFIG. 6, with multiple photodetectors20a,20bpositioned about the light source assembly16. While only a single lens50is shown for interacting with the reflected rays24, it can be appreciated that a second lens (not shown) could also be positioned relative to the photodetector20ashown to the left of the light source assembly16in the diagram. It can be appreciated that the elevation view inFIG. 7shows a pair of photodetectors20, however, additional photodetectors20can be placed about the light insulating cap42as illustrated inFIG. 9. In the example shown inFIG. 9, first, second, third, and fourth photodetectors20a,20b,20c, and20dare positioned about the light insulating cap42and light source40, however more or fewer discrete elements can be used.

FIG. 8illustrates yet another configuration for the sensor assembly12in which a photodetector200includes a hole, depression, aperture, or cavity, referred to herein as an opening52to reflect that the cavity or depression can be either complete (as in a hole or aperture) or partial (as in a depression, cavity, notch, slot, etc.). As can be appreciated fromFIG. 8andFIG. 10, in this configuration the substrate22supports a single photodetector200with the opening52formed therein (e.g., by drilling a hole through the photodetector200). The opening52provides a region or area into which the light source40can be placed. The lens44can also be positioned at the upper edge of the opening52as illustrated inFIG. 8with the side walls of the opening52providing a functional equivalent to the light insulating cap42to prevent the photodetector200from detecting the beam18prior to being reflected by the object14. As withFIG. 7, it can be appreciated that while only a single lens50is shown for interacting with the reflected rays24, a second lens (not shown) could also be positioned relative to the photodetector20ashown to the left of the light source assembly16in the diagram.

It can also be appreciated that any of the configurations shown inFIGS. 6-8can be used in any of the scenarios shown inFIGS. 1-5, e.g., with a moving or static system10, a moving or static object14, multiple sensor assemblies12, with various distances between the system10and the object14, etc.

Referring now toFIG. 11, a flow chart illustrating computer executable instructions that can be implemented to enable the controller30to operate the system are shown. In step100the one or more sensor assemblies12are installed or otherwise provided within the environment, application, or apparatus in which they are to be used. For example, the system10may be part of a larger device onto which a desired number of sensor assemblies12are installed. At step102the system10is calibrated to determine the positions of the sensor assemblies12, e.g., to establish a baseline or datum for any particular edge or contrast detection spatially within the environment. At step104, the system10can be calibrated to determine a signature for each surface or edge to be detected. For example, in the configuration and scenario shown inFIG. 2, three different reflection/scatter signatures may be determined, each indicative of the presence of a particular surface, edge, object, component of an object, etc.

It can be appreciated that steps100-104may be associated with a set-up or calibration process and may only be required once or periodically for a given system10. At step106, the controller30operates the light source40and photodetector(s)20to search for an edge or transition/contrast over a surface of an object14. This step may also include operation of a servo-motor or signaling of an instruction to have the substrate22or the object14moved relative to each other to enable the detection operation. At step108the controller30determines whether the edge or transition or contrast has been found. If not, the controller30may continue to await a detection event by repeating step106. If an edge or transition or contrast is found or detected at108, the controller30can generate a response output or instruction at step100. The response output or instruction can be internal to the system10(i.e. to have the system10react in a predetermined manner according to the detection) or external to the system10, e.g. to provide an output, response, instruction, alert, etc. to another system.

The steps or operations in the flow charts and diagrams described herein are just for example. There may be many variations to these steps or operations without departing from the principles discussed above. For instance, the steps may be performed in a differing order, or steps may be added, deleted, or modified.