Registers – Coded record sensors – Particular sensor structure
Reexamination Certificate
2001-06-18
2003-04-22
Lee, Diane I. (Department: 2876)
Registers
Coded record sensors
Particular sensor structure
Reexamination Certificate
active
06550679
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a mounting system for mounting a structure whose thickness cannot be tightly controlled, and particularly to a mounting system for mounting an image sensor.
2. Background of the Prior Art
A typical image sensor chip
12
of the type mounted in various types of devices, such as medical instruments, video cameras, and bar code readers is shown in FIG.
6
. The image sensor shown includes a bottom planar member
110
carrying a pixel array
112
. Front and rear lead frames
114
initially extend peripherally from the pixel array and are formed to extend downwardly about front and rear edges respectively, of bottom planar member
110
terminating in pins
32
. Image sensor
12
further includes top planar member
118
which rests against pixel array
112
and lead frame
114
. Top planar member
118
is secured against lead frames
114
and against pixel plane
112
by the force of adhesive material interposed between top and bottom planar members
110
and
118
. Adhesive material is disposed mainly about the periphery of pixel array
112
. In addition, image sensor
12
may include a glass layer
120
. In some popular models of image sensors, top planar member
118
is configured in the form of a frame which retains glass layer
120
. Thus, it is seen that image sensor
12
is of a stacked-up configuration. Like most structures whose design is of a generally stacked-up configuration, the thickness, t, of assembly
12
cannot be tightly controlled. In the manufacturing of sensor
12
, the thickness of the various layers will vary from structure to structure. Accordingly, the total thickness, t, will vary from structure to structure. The spacing, s, between top and bottom planar members
110
and
118
of image sensor
12
is particularly difficult to control given that such spacing is a function of the amount of adhesive used, the thickness of pixel array
112
and the thickness and the thickness of lead frames
114
.
Particularly in applications where such an image sensor must be side mounted (not “plugged into” a PCB), as is the case with most bar code reader applications, then the inability
to tightly control image sensor thickness, t, can negatively impact operational characteristics of the device in which the sensor is incorporated in. An explanation of how the inability to tightly control sensor thickness can impact operation of a bar code reader is made with reference to
FIGS. 7 and 8
showing a multilayered image sensor incorporated in a bar code reader according to a prior art mounting scheme. In the mounting scheme shown, a multilayered image sensor
12
is disposed into a holding pocket
16
defined by substantially equally tensioned pairs of rear pins
19
and forward pins
18
. The prior art mounting system may further include a spacer
21
for biasing sensor
12
forwardly against forward pins
18
.
A number of operational problems can arise with this mounting scheme. If the thickness of the image sensor which is manufacturable to a thickness in the tolerance range from T
min
to T
max
tends toward T
min
then pins
18
,
19
may not supply sufficient pressure to image sensor
12
to hold sensor
12
in a secure position. Further, it can be seen that the distance, d, from any fixed point in space, P
s
to any fixed P
p
, on the plane of pixel array
12
will vary depending on the total thickness, t, of sensor
12
which is a thickness having a high degree of variability. This is not preferred since controlling the distance, d, is important to controlling the operation of the reader.
There is a need for an image sensor mounting system for mounting an image sensor in an imaging device which minimizes operational problems resulting from the inability to tightly control an image sensor chip's thickness.
SUMMARY OF THE INVENTION
According to its major and broadly stated the present invention is a mounting system for mounting an image sensor chip in a location in a device apart from a PCB board.
In one embodiment of the invention, a multilayered image sensor is back mounted to a plate, and the plate in turn, is installed in a holding pocket of a device. In that the scheme takes advantage of a high controllability of a mounting plate's thickness, the mounting scheme improves the consistency of holding forces with which several image sensors are secured in like configured imaging devices. In that the scheme provides for back mounting of image sensor on a plate, the mounting system reduces fluctuations in pixel plane to fixed point distances.
The mounting scheme may be enhanced by forming cutout sections in the mounting plate. The cutout sections serve to bench lead frames extending from an image sensor, and thereby service to minimize sliding or twisting of an image sensor mounted on a mounting plate. In another enhancement, an image sensor mounted on a mounting plate is secured to the plate entirely by a compression force supplied by a flex strip, soldered onto an image sensor's lead frames, impinging on the mounting plate. This arrangement serves to further minimize thickness variations resulting from manufacturing tolerances.
In a variation of the invention, the mounting plate is substituted for a by a back plate formed integral with a component frame of a device. The back plate along with the remainder of the frame define an elongated aperture adapted to a receive a lead frame of an image sensor. An image sensor may be mounted to a back plate in essentially the same way that an image sensor is mounted to a mounting plate to the end that an image sensor is tightly secured in a device and further to the end that pixel plane to fixed point distance is tightly controlled.
These and other detail, advantages, and benefits of the present invention will become apparent from the detailed description of the preferred embodiment hereinbelow.
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Hennick Robert J.
Hinkley Robert C.
Lacey Michael P.
McCall Melvin D.
Hand Held Products, Inc.
Lee Diane I.
Wall Marjama & Bilinski LLP
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