In one type of coordinate measuring machine, the surface of a workpiece is scanned with a probe. After the scan, a three dimensional profile of the workpiece is provided. In one type of scanning probe, the workpiece is directly measured by touching a mechanical contact of the probe to various points along the workpiece surface. In some cases, the mechanical contact is a ball.
In other coordinate measuring machines, an optical probe is utilized which measures the workpiece without making physical contact with the surface. Certain optical probes (e.g., triangulation probes) utilize light to measure workpiece surface points, and some optical probes comprise video cameras which are used to image 2-D sections of the workpiece surface (e.g., stereo vision systems, or structured light systems). In some systems, the coordinates of the geometric elements of the workpiece are determined via image processing software.
Certain “combined” coordinate measuring machines that use both optical and mechanical measuring sensors are also known. One such device is described in U.S. Pat. No. 4,908,951, which is hereby incorporated by reference in its entirety. The described apparatus has two spindles, one that carries the mechanical probe, and one that holds a video camera having a beam path into which a laser probe is simultaneously reflected for making measurements in the Z coordinate, that is, along the optical axis of the video camera.
U.S. Pat. No. 5,825,666, which is hereby incorporated by reference in its entirety, describes an optical coordinate measuring machine wherein an optical touch probe of the device has a first target on the distal end thereof, on the contact element of a standard probe. The standard probe is mounted to a video camera to image the target on the camera. Movement and position of the target in the X and Y coordinates is indicated by the machine's computer image processing system. A second target is mounted to the proximal end of the probe and indicates movement and position in the Z coordinate. The second target may obscure a photo detector, but can be parfocused on the camera by a light beam parallel to the X, Y plane. There can be two second targets illuminated by orthogonal beams parallel to the X, Y plane. Rotation around the Z axis then may be calculated by the computer when star probes are used. Auto changing racks are also disclosed for holding multiple probes, a probe holder, and lenses for selective mounting on the camera.
Measuring probes are frequently interchangeably attached to coordinate measuring machines at an auto exchange joint connection (also referred to as an “autojoint”, in some contexts) included in various “probe heads.” At present, Renishaw™ probe heads are the most commonly used for certain applications in the industry. These probe heads are manufactured by Renishaw Metrology Limited in Gloucestershire, United Kingdom. While Renishaw-type probe head systems are the most commonly used in the industry, certain technologies are not easily incorporated into Renishaw-type systems. Furthermore, attempts to upgrade an existing Renishaw-type probe head system to one with more advanced capabilities can entail significant costs and/or inconvenience. For example, certain technologies adapted to a Renishaw-type probe head system may lack desirable features, lack a desirable level of controllability, and/or lack the capacity for being automatically interchangeable (e.g., interchangeable under machine control without human intervention) with other types of probes that are configured to be interfaced to the Renishaw-type probe head system. One particular issue with regard to using Renishaw-type probe head systems, or similar systems, is that the existing data and control connections between the machines and the probes consist of a limited number of wired connections and no optical fiber connections or optical paths at the auto exchange joint. This effectively forms a “bottleneck” which makes it difficult to add additional technologies and/or features to a probe that is to be mounted and/or exchanged using the probe head system. In particular, existing chromatic range sensors have not been attachable and/or interchangeable using a Renishaw-type probe head system, or the like. The architecture of existing chromatic range sensors is not compatible with data and control connections included in Renishaw-type probe head systems. A chromatic range sensor probe that is automatically attachable and/or interchangeable on a coordinate measuring machine (CMM), for example, using a Renishaw-type probe head system would be desirable.
A related issue with existing chromatic range sensors is that even if the architecture of a chromatic range sensor could be devised such that it might be included in a chromatic range sensor probe system that is automatically attachable and/or interchangeable on a CMM (e.g., using a Renishaw-type probe head system), existing types of chromatic range sensor optical pens are designed for manual replacement and are not automatically interchangeable. Thus, a chromatic range sensor probe system would still be limited in its utility due to an inflexible measurement range and/or direction associated with a particular optical pen used in the probe. This inflexibility would be a significant barrier to the creation and adoption of a chromatic range sensor probe system, which may have a poor cost/benefit ratio if it cannot have its measurement range and/or accuracy altered quickly and reliably as needed for a particular measurement operation.