Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
2001-06-25
2004-06-08
Pyo, Kevin (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C356S369000, C360S290000
Reexamination Certificate
active
06747267
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to systems for measuring static attitude (orientation angle) of portions of head suspension assemblies.
BACKGROUND OF THE INVENTION
Head suspension assemblies (“HSAs”) position a read/write head over the spinning surface of a data storage device (e.g. a magnetic hard disk). HSAs are some of the smallest and most delicate components of a rigid disk drive. An HSA includes a suspension assembly, an elongated spring structure, with a head assembly positioned at a distal end. Suspension assemblies act in a similar fashion to the needle arm in a record player, positioning the head assembly nanometers from the surface of a spinning disk in the disk drive. Typical suspension assemblies measure less than 20 mm long and are 0.03 to 0.1 mm thick. Suspension assemblies generally include an elongated load beam with a flexure located at a distal end and a base plate or other mounting structure located at a proximal end.
The flexure comprises a head bonding platform suspended by spring arms. The head assembly is mounted to this head bonding platform. The head assembly includes an air bearing slider and a read/write magnetic transducer formed on the slider. The slider is aerodynamically shaped to use the air stream generated by the spinning disk to produce a lift force. During operation of the disk drive, the spring arms provide gimballing motion to maintain the head assembly at a desired orientation with respect to the surface of the disk. The suspension assembly must balance the different lift forces on the outside and the inside air-bearing surfaces of the slider (the outside circumference of a round disk has a faster linear velocity than the inside, and therefore produces more lift), static forces (e.g. weight and pressure applied on the slider by the suspension assembly), and dynamic forces (e.g. momentum). The flexure and the whole HSA are manufactured within precise tolerances.
In a magnetic disk drive, the density and accuracy of the data stored on the disk depend on the distance (referred to as “Z-height”) and orientation (referred to as “static attitude”) of the head assembly with respect to the surface of the disk. The size of the magnetic field “spot” written and read by the transducer is directly proportional to the square power of the Z-height distance between the transducer and the disk. Small changes in distance and/or attitude can cause the head assembly to “crash”, that is, to hit the surface of the spinning disk. A crash can destroy both the transducer and the data on the surface of the disk. Tight manufacturing tolerances are a factor in determining disk drive reliability.
HSA manufacturers must repeatedly measure and control the Z-height and static attitude of different elements of the HSA at various points during the manufacturing process. The reference point for both the Z-height and the static attitude measurements is a manufacturing datum plane. The manufacturing datum plane is a horizontal plane representing a suspension mounting surface of an actuator. During manufacturing, the manufacturing datum plane is placed generally parallel to and below the suspension assembly.
A static attitude measurement includes a pitch axis angle measurement and a roll axis angle measurement measured in relation to the datum plane. The pitch and the roll axes are parallel to the horizontal plane and are mutually perpendicular, intersecting at a point on the head bonding platform. The roll axis is usually aligned with the longitudinal axis of the suspension assembly.
Static attitude can be measured using autocollimation systems. Autocollimation systems are measuring instruments that generate a collimated light beam (a light beam having parallel rays of light) having a relatively large diameter. The collimated light beam is directed to and reflected off of the surface of the part being measured. The reflected light beam strikes a linear array of light sensors. The sensors collect data on the reflected light beam which is fed into a computer to calculate the pitch and roll angles of the part. Autocollimation systems offer accurate and fast angle measurements.
In many instances, both the Z-height and the static attitude are measured by the same instrument in order to save time and space in the manufacturing process, as well as reduce errors in the measurement procedure. A single light source, such as a laser, produces a beam of light which is then split by a beam splitter into a first beam used to measure the Z-height and a second beam used to measure the static attitude. The second beam is directed by additional optics toward the head suspension target. This beam is then reflected back off the target and back to a detector.
As shown in
FIG. 1
, a prior art static attitude measurement system
20
, such as a WYKO™ SAT probe produced by Veeco Instruments Inc., Plainview, N.Y., includes a light source
30
to produce a light beam
32
. Light beam
32
is typically linearly polarized at an angle, which is a combination of two components, one at a first polarization state (as represented by a solid line) and one at a second polarization state (as represented by a dashed line). System
20
also includes a beam splitter
40
that splits beam
32
, passing a first beam
33
and reflecting a second beam
34
. Due to the angle of incidence of beam
32
on beam splitter
40
and other reasons, the first beam
33
almost exclusively contains light in the second state of polarization, which is directed toward optics (not shown) and used for measuring Z-height of a suspension
64
. The second beam
34
, however, is a mixed beam and primarily includes light in the first state of polarization, but also some light in the second state of polarization. This second beam
34
is directed toward a second beam splitter
42
. A beam reducer (not shown) may optionally be located between the first and second beam splitters
40
,
42
, in order to reduce the diameter of the beam
34
.
The second beam splitter
42
splits the beam
34
by passing a beam
35
and directing a beam
36
orthogonally toward the suspension
64
to measure the attitude on a surface
62
of the suspension
64
. Beam
36
is reflected off of the surface
62
and travels back in the opposite direction of the incoming beam. Beam
36
passes through some collection optics
44
, such as a pair of lenses, when traveling toward and away from the suspension
64
.
When returning beam
36
encounters the second beam splitter
42
, a portion
38
of the beam
36
passes through and a portion is reflected back toward the first beam splitter
40
. The passed portion
38
then encounters a series of optics
72
,
74
,
76
that filter out unwanted light, before the beam
38
strikes a detector
70
. In particular, optics
76
, such as a polarized filter, stops the second state polarized light portion in beam
38
, but passes the primary portion in the first state of polarization. The information collected by the detector
70
is then used by a computer or other instrument to calculate the static attitude of the suspension
64
.
Although the provided system is effective in producing static attitude measurements, there are some side effects to the optics that create problems with the system. As stated above, when the returning beam
36
encounters the second beam splitter
42
, a portion of the beam is reflected back toward the first beam splitter
40
. Because beam
36
primarily includes light at the first polarization state, the majority of this reflected, secondary beam is also at the first polarization state. If this secondary beam is strong enough, due to the surface
62
being highly reflective or other reasons, this beam may be reflected back toward the light source
30
by the first beam splitter
40
. This beam then reflects off the light source
30
, shown as phantom beam
52
, which then is split at beam splitter
40
into beam
54
, which is then split and directed by second beam splitter
42
toward the suspension
64
as beam
56
. Beam
56
is then reflected off the surface
62
in a manner sim
Faegre & Benson LLP
Hutchinson Technology Incorporated
Pyo Kevin
LandOfFree
Static attitude measurement system for head suspension... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Static attitude measurement system for head suspension..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Static attitude measurement system for head suspension... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3311321