Display device for a coordinate measurement machine

A novel display device for use with a three dimensional coordinate measurement system provides a Display positioned on a multijointed measuring arm allowing an operator to have convenient display of positional data and system menu prompts. The display device further includes LED's indicating system power, transducer position status and error status. An embodiment of the present invention receives signals from a host computer via telemetry allowing the display to be positioned remote from the system.

FIELD OF INVENTION 
This invention relates generally to three dimensional coordinate measuring 
machines (or CMM's). More particularly, this invention relates to a new 
and improved display for a three dimensional CMM which provides improved 
accuracy and ease of use. 
BACKGROUND OF INVENTION 
It is well known in the art to utilize a CMM to measure objects in a space 
in terms of their X, Y, and Z coordinates commonly referring to length, 
width and height. Advancement in the art has led to lightweight portable 
CMM's well suited for general industrial applications. Such a CMM is 
disclosed in U.S. Pat. No. 5,402,582 which is commonly assigned to the 
assignee hereof and incorporated herein by reference. Three dimensional 
objects are described in terms of position and orientation; that is, not 
just where an object is but in what direction it points. The orientation 
of an object in space can be defined by the position of three points on 
the object. Orientation can also be described by the angles of alignment 
of the object in space. The X, Y, and Z coordinates can be most simply 
measured by three linear scales. In other words, if you lay a scale along 
the length, width and height of a space, you can measure the position of a 
point in the space. 
Presently, coordinate measurement machines or CMM's measure objects in a 
space using three linear scales. Coordinate measuring machines of the 
prior art comprise a multijointed (preferably six joints) manually 
positional measuring arm for accurately and easily measuring a volume 
which typically comprises a sphere preferably ranging from six to eight 
feet in diameter (but which may also cover diameters more or less than 
this range). In addition to the measuring arm CMM's of the prior art 
employ a controller (or serial box) which acts as the electronic interface 
between the arm and a host computer which displays menu prompts and 
outputs to an operator. The mechanical measuring arm used in CMM's 
generally comprise a plurality of transfer housings (with each transfer 
housing comprising a joint and defining one degree of rotational freedom) 
and extension members attached to each other with adjacent transfer 
housings being disposed at right angles to define a movable arm preferably 
having five or six degrees of freedom. Each transfer housing includes 
measurement transducers. In addition, each transfer casing includes visual 
and audio endstop indicators to protect against mechanical overload due to 
mechanical stressing. 
The use of a discrete microprocessor-based controller box permits 
preprocessing of specific calculations without host level processing 
requirements. This is accomplished by mounting an intelligent preprocessor 
in the controller box which provides programmable adaptability and 
compatibility with a variety of external hosts (e.g., external computers). 
The serial box also provides intelligent multi-protocol evaluation and 
auto switching by sensing communication requirements from the host. For 
example, a host computer running software from one manufacturer will 
generate call requests of one form which are automatically sensed by the 
controller box. Still other features of the controller box include serial 
port communications for standardized long distance communications in a 
variety of industrial environments and analog-to-digital/digital counter 
boards for simultaneous capture of encoder data from all of the transfer 
housing resulting in highly accurate measurements. 
CMM's of the prior art include transducers (e.g., one transducer for each 
degree of freedom) which gather rotational positioning data and forward 
this basic data to a serial box. The serial box provides certain 
preliminary data manipulations. In a typical configuration the serial box 
is positioned under the host computer somewhat remotely from the probe and 
of the arm. The serial box includes EE-PROMS which contain data handling 
software, a microcomputer processor, a signal processing board and a 
number of indicator lights and audio output, usually in the form of a 
speaker. As mentioned, basic transducer data is sent from the arm to 
serial box where the serial box then processes the raw transducer data on 
an ongoing basis and responds to the queries of the host computer with the 
desired three dimensional positional or orientational information. 
Presently CMM systems require that the operator, while manipulating the 
arm, refer back to the display screen of the host computer and respond to 
alphanumeric messages displayed thereon or respond to audio signals. The 
messages and audio signals are generated by the host computer and 
applications software. In certain cases the components of the CMM system 
(e.g., the arm, serial box and host computer with display) are arranged in 
positions which are often difficult or inconvenient for the operator to 
see or hear. 
Measurement arms for CMM's include a probe handle at the operator end. 
Probe handles of the prior art are held by an operator as either a pencil 
or pistol grip and sometimes possess two switches for the attachment of 
optional electronics and/or a threaded mount for receiving a variety of 
probes. Because the CMM is a manual measurement device, the user must be 
capable of taking a measurement and then confirming to CMM whether the 
measurement is acceptable or not. This is typically accomplished through 
the use of the two switches. One switch is used to trap the 3 dimensional 
data information and the second switch confirms its acceptance and 
transmits it to the host computer. A number of voltage lines and 
analog-to-digital converter lines are routed from the serial box through 
the arm to the probe handle for general attachment to a number of options 
such as a laser scanning device or touch probe. The switches are also used 
to respond to menu prompts, either displayed or audio signals, from the 
host computer. 
A variety of probes may be threaded to a probe handle assembly such as a 
hard 1/4 inch diameter ball probe or a point probe is shown. The probes 
are typically threadably mounted to mount which in turn, is threadably 
mounted to a probe housing and may also include a plurality of flat 
surfaces for facilitating engagement and disengagement of the probes using 
a wrench. 
The front panel of a serial box of the prior art has eight lights including 
power indicator light and error condition light and six other lights 
corresponding to each of the six transducers located in each transfer 
housing. Upon powering up, the power light will indicate power to the arm. 
The six transducer lights indicate the status of each of the six 
transducers. 
The status lights may indicate, for example, if any of the transducers 
approach its rotational endstop from within 2 degrees, the light, and an 
audible beep, for that particular transducer indicates to the user that 
the user is too close to the end stop; and that the orientation of the arm 
should be readjusted for the current measurement. The serial box will 
continue to measure but will not permit the trapping of the data until 
such endstop condition is removed. A typical situation where this endstop 
feature is necessary is the loss of a degree of freedom by the rotation of 
a particular transducer to its endstop limit and, hence, the applications 
of forces on the arm causing unmeasured deflections and inaccuracies in 
the measurement. 
At any time during the measurement process, a variety of communication and 
calculation errors may occur. These are communicated to the user by a 
flashing of the error light and then a combination of lights of the six 
transducers indicating by code the particular error condition. Some serial 
box front panels utilize an alphanumeric LCD panel giving alphanumeric 
error and endstop warnings. 
SUMMARY OF THE INVENTION 
The above discussed and other drawbacks and deficiencies of the prior art 
are overcome or alleviated by the present invention. In accordance with 
the present invention a novel display device for use with a three 
dimensional coordinate measuring machine (CMM). The display device is 
positionable near the probe handle end of the arm of a CMM to display 
transmission from the microprocessor in a convenient visual and audio 
format for an operator. An embodiment of the present invention includes a 
liquid crystal display (LCD), a speaker and a plurality of light emitting 
diodes (LED's). The LCD displays coordinate information relative to the 
measuring probe within a defined workspace and further provides 
alphanumeric information in the form of system driven menu prompts. The 
display provides information to an operator pertaining to the arm 
transducer status, error signals and power status. The speaker provides 
audio information indicating system conditions, errors or operator 
prompts. The display device of the present invention also includes a 
headphone jack for permitting the use of headphones in situations where 
the speaker is less than optimal. 
The display device is mountable at various positions along the arm of a CMM 
and comprises a wrist component mount which permits rotation of the 
display for operator viewing. In an embodiment the display device 
comprises a magnetic base to provide rotational positioning within the 
mount. In another embodiment the host computer transmits information to 
the display device via telemetry which allows the display device to be 
positioned remote from the arm. 
The display device of the present invention displays system driven menu 
prompts which an operator responds to using the trap and accept buttons of 
the prior art. An embodiment of the present invention includes an option 
port for receiving a menu selection device, mouse, or keyboard for 
interacting with the microprocessor. 
The above discussed and other features and advantages of the present 
invention will be appreciated and understood by those skilled in the art 
from the following detailed description and drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1 a multi jointed manually operated arm for use with a 
coordinate measuring machine (CMM) is shown generally as 1. In general 
terms, arm I is comprised of a base 2 connected to a first set of transfer 
housings 3, 4, a first extension member 5 rigidly attached to the first 
set of transfer housings and a second set of transfer housings 6, 7 and a 
third set of transfer housings 9, 10 disposed between a second extension 8 
with transfer housing 9 attached to transfer housing 7. The sets of 
transfer housings are generally pairs of rotatable joints positioned 
transverse to one another and, as in the prior art, have position sensing 
transducers disposed therein (not shown). Mounted at the end of arm I and 
extending from transfer housing 10 is probe handle assembly 11 including 
data switch buttons 17, 18. As in the prior art arm 1 electrically 
communicates with serial box 12 via cable 13 which communicates with 
electronically with host computer 14 having display 15 via cable 16. 
In accordance with the present invention, the embodiment of FIG. 1 shows, 
by way of example, display device 50 disposed on arm 1 near probe handle 
assembly 11 in the vicinity of an operator (not shown) manipulating the 
arm. In fact, display 50 may be positioned at any one of several points 
along arm 1 convenient to the operator and as described herein below. 
Display 50 comprises many of the features of the serial box and host of 
prior art CMM systems as described herein above and details of display 50 
are more readily described with reference to FIG. 2. By way of example 
display 50 includes text screen 51 comprised of an LCD as is known for 
visually displaying dimensional data and prompts to an operator. Display 
50 further comprises LED's 52-57 which correspond to the six transducers 
in transfer housings 3, 4, 6, 7, 9, 10 to indicate the status of each of 
the transducers. In addition display 50 comprises warning LED 58 which, 
for example, lights when a transfer housing is approaching a stop during 
movement of arm 1 and also includes power indicating LED 59 which 
indicates that power is being transmitted to the arm. Display 50 further 
includes audio speaker 61 and head phone jack 61 for transmitting audio 
signals from the serial box 12 and host computer 14 to an operator. Head 
phone jack 61 enables an operator to hear and respond to audio signals 
from the host computer while operating in a noisy environment. In the 
embodiment shown in FIG. 1 electronic communication is transmitted from 
host computer 14 and serial box 12 to arm 1 via cables 13, 16 and within 
arm 1 to display 50 via internal cables as is known. 
Referring to FIG. 2 display 50 is disposed on base mount 62 by screws 63. 
Base mount 62 is disposed on wrist component 64 and axial secured and 
secured in a limited rotational path by a ball and detent arrangement (not 
shown) as is known. Wrist component 64, and therefore display 50, are 
removably secured to extension 8 by twist and lock grooves 65 engaged with 
matching splines (not shown) on the extension as is known. With display 50 
mounted as described an operator manipulating arm 1 via handle assembly 11 
can rotate display 50 in the directions represented by arrow 66 to provide 
a convenient perspective to the display. 
An alternative embodiment of the present invention is described with 
reference to FIG. 3 wherein telemetric display 67 includes magnet base 68 
mounted to the backside thereof. Telemetric display 67 functions similar 
to that described herein above but transmits and receives electronic 
communications between serial box 12 and host computer 14 via telemetry as 
is known. Magnetic base 68 allows display 67 to mounted to any suitable 
surface convenient to an operator. For instance display 67 can be 
temporarily mounted to a ferrous workpiece or other convenient ferrous 
surface to provide close inspection to the operator. In another 
embodiment, base mount 62 comprises a ferrous surface allowing for the 
removable mounting of display 67. The advantage of this embodiment is that 
display 67 may be rotated in the direction indicated by arrow 69 to 
accommodated certain uses or manipulations of arm 1 to provide a 
convenient perspective to an operator or removed and applied to a wall or 
workpiece as described above. In yet another embodiment telemetric display 
67 comprises a base mounting adaptable for a hook and loop type temporary 
fastening system as is known. In another embodiment display 67 comprises a 
spring clip type fastener as is known for temporary installation on a 
variety of surfaces. 
In operation, the present invention permits the physical positioning of the 
display convenient to an operator in situations where the display and 
serial box of the prior art may be less than optimal. Upon start up of the 
CMM system an operator is given convenient access to both visual and audio 
information about the system such as power to the arm 1 via LED 59 and the 
status of the transducers via LED's 52-57. During manipulation of arm 1 to 
inspect a workpiece the operator receives prompts from serial box 12 and 
host 14 in the form of audio signals via speaker 60 and alphanumeric 
characters displayed on screen 51. The operator may respond to the prompts 
by pressing buttons 17, 18. In an alternative embodiment an operator 
display screen 51 comprises a touch screen as is known to allow the 
operator to respond to a simple set of menu selections transmitted from 
the host computer by touching the surface of the screen. In the embodiment 
shown in FIG. 2 display 50 includes an option port 70 receiving, for 
example, menu selection tool 71. Alternatively option port 70 may receive 
a communication link from a key board or other input or output device. 
During use of a CMM incorporating a display in accordance with the present 
invention the serial box 12 first undergoes self checking procedures and 
supplies power of arm1 as in the prior art. The microprocessor resident in 
serial box 12 sends a signal to display 50 lighting LED 59 indicating to 
the operator that the arm has power and lighting LED's 52-57 indicating 
that the transducers have not been calibrated as in the prior art. Error 
LED 58 would also be illuminated. The operator, through manipulation of 
arm 1, causes the arm to pass through the preselect reference locations 
and as each transducer is referenced the corresponding LED is extinguished 
until all LED's 52-57 are extinguished as well as error LED 58. The 
display 50 of the present invention with its position [roximal the 
operator gives instant and convenient indication. Once all the transducers 
have been referenced the system establishes electronic communication with 
the host and awaits further communication from the operator. Typically the 
operator depresses button 17 or 18 to initiate the measurement process. 
Once the measurement process has begun dimensional coordinates of the 
probe end are displayed on text screen 51. The LCD of text screen 51 is 
capable of displaying measurement coordinates in the coordinate system of 
the workpiece through feedback from the application software of the host 
computer. The operator is able to visually receive the coordinates of the 
probe on text screen 51 as arm 1 is manipulated about the workpiece within 
the working volume of the CMM. 
While preferred embodiments have been shown and described, various 
modifications and substitutions may be made thereto without departing from 
the spirit and scope of the invention. Accordingly, it is to be understood 
that the present invention has been described by way of illustration and 
not limitation.