Adjustable focus imaging device

Details Adjustable focus imaging device Adjustable focus imaging device

2001-08-27

2003-12-16

Porta, David (Department: 2878)

Radiant energy

Photocells; circuits and apparatus

Photocell controls its own optical systems

C250S556000, C235S462220, C396S082000

Reexamination Certificate

active

06664525

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to imaging systems and, more specifically, to an adjustable focus imaging device.
BACKGROUND OF THE INVENTION
Imaging devices are used to produce machine-readable image data (image data) that is representative of an image of an object, e.g., a page of printed text. The process of generating image data is sometimes referred to as capturing or imaging an object. One type of imaging device is a photoelectric imaging device. As used herein, the phrase “photoelectric imaging device” means any device that generates image data representative of an image of an object through use of a photosensor array. Examples of photoelectric imaging devices include devices such as camcorders and digital cameras that instantaneously focus an entire image that is to be captured onto a two-dimensional photosensor array. Another example of a photoelectric imaging device is a line-focus system as described below.
Some line-focus systems image an object by sequentially focusing narrow “scan line” portions of the image of the object onto a linear photosensor array by sweeping a scanning head over the object. The scanning head is an imaging device or has an imaging device located therein. Examples of such devices include computer input devices such as optical scanners, which are commonly referred to simply as “scanners”. Other examples include facsimile machines and digital copy machines.
A line-focus system is also used in some barcode readers. Generally, in line-focus barcode readers, a narrow portion of a barcode is imaged onto a linear photosensor array. Electrical output from the photosensor array may then be analyzed to read the imaged barcode. Examples of imaging devices that are useable in conjunction with barcode readers are disclosed in U.S. Pat. No. 6,118,598 of Gardner, Jr. for METHOD AND APPARATUS FOR SETTING FOCUS IN AN IMAGING DEVICE and in U.S. patent application Ser. No. 09/290,216, of Gardner, Jr. for ALIGNMENT APPARATUS AND METHOD FOR AN IMAGING SYSTEM, which are both hereby specifically incorporated by reference for all that is disclosed therein.
Referring to
FIG. 1
, a schematic view of a conventional line-focus system is provided for illustrative purposes. The line-focus system is provided with a light source
308
, a plurality of light beams
310
,
312
,
314
, a plurality of reflected light beams
320
,
322
,
324
, a lens assembly
330
, a linear photosensor array
340
and a data processing system
370
. A use for such a line-focus system is for reading labels, perhaps a barcode
350
located on an object, such as a media storage device
360
. The distance between the lens assembly
330
and the barcode
350
may be referred to as the object distance Lo. The distance between the linear photosensor array
340
and the lens assembly
330
may be referred to as the image distance Li. In the line-focus system, light beams
310
,
312
,
314
are emitted from the light source
308
and are focused or directed onto the barcode
350
. The light beams
310
,
312
,
314
reflect off of the barcode
350
as reflected light beams
320
,
322
,
324
. Line focus systems are described in U.S. patent application Ser. No. 08/888,339 of Kershner for CATADIOPTRIC LENS FOR A SCANNING DEVICE, which is hereby specifically incorporated by reference for all that is disclosed therein.
The reflected light beams
320
,
322
,
324
converge at the lens assembly
330
. After converging at the lens assembly
330
, the reflected light beams
320
,
322
,
324
are focused onto the linear photosensor array
340
. The linear photosensor array
340
may, for example, be a single dimension array of photoelements, wherein each photodetector element corresponds to a small area location on the barcode
350
. These small area locations on the barcode
350
are commonly referred to as “picture elements” or “pixels.” The reflected light beams
320
,
322
,
324
travel from a corresponding pixel location on the barcode
350
to the linear photosensor array
340
. Each photosensor pixel element in the linear photosensor array
340
(sometimes referred to simply as a “pixel”) produces a data signal that is representative of the light intensity that it experiences. All of the photoelement data signals are received and processed by an appropriate data processing system
370
.
In imaging devices, and particularly in a line-focus type imaging device as described above, it is preferable that the reflected light beams
320
,
322
,
324
from the barcode
350
be accurately aligned with and focused onto the linear photosensor array
340
in order to accurately image an object. In a typical line-focus scanning device, the reflected light beams
320
,
322
,
324
are transmitted by one or more optical components, such as the lens assembly
330
before reaching the linear photosensor array
340
. Even a slight misalignment between any of these optical components and the linear photosensor array
340
will likely result in a corresponding degradation in image quality.
Scanning devices that include light beam alignment features are fully described in U.S. Pat. No. 5,646,394 of Steinle et al. for IMAGING DEVICE WITH BEAM STEERING CAPABILITY, U.S. Pat. No. 6,147,343 of Christensen for PHOTOELECTRIC IMAGING METHOD AND APPARATUS, and U.S. patent application Ser. No. 09/813,205 of Schmidtke et al. for METHOD AND APPARTUS FOR SETTING FOCUS IN AN IMAGING DEVICE, 2001 which are all hereby specifically incorporated by reference for all that is disclosed therein.
Typically, the optical components in an imaging device are mounted within an imaging device housing. The photosensor array is typically mounted to a circuit board, which, in turn, is mounted to the imaging device housing. A lens is also typically mounted within the imaging device housing. The lens serves to focus an image of an object onto the photosensor array. In order for the image to be accurately focused onto the photosensor array, and therefore the imaging device to function properly, the focus of the lens must be located at a precise position within the housing. Additionally the distance between the object and the lens assembly should remain constant. By retaining the object distance, the overall quality of the image remains constant.
After a conventional imaging device is assembled, the image distance Li (
FIG. 1
) is generally adjusted once to focus an object located at the object distance Lo (FIG.
1
). Typically, this is done by adjusting the distance between the lens and the photosensor array, i.e., the image distance Li (
FIG. 1
) of the optical system, until the proper focus is achieved. To accomplish this, imaging devices are commonly provided having a reference surface or surfaces for locating the lens relative to the photosensor array. These reference surfaces typically allow the lens to translate in only one degree of movement, i.e., in directions toward or away from the photosensor array, but prevent the lens from being displaced in other directions.
Imaging devices also typically include a bracket or some other retention device to lock the lens in place against the reference surface or surfaces after the focus of the imaging system has been set. The bracket may, for example, be secured by a screw. Accordingly, the screw may be loosened when it is desired to move the lens in order to focus the system, and then tightened to lock the lens in place when the proper focus has been achieved. This adjustment is for preliminary focusing and calibration of the system at the time of manufacturing and is typically not capable of adjustment while the system is in operation.
FIG. 2
schematically illustrates a focus setting device
400
which may be used to set the focus of an imaging device. The focus setting device
400
may generally include a fixture
410
and a moveable arm
420
. The fixture
410
is adapted to securely hold a sidewall
46
of a device, as shown. A moveable arm
420
may be adapted to move in the directions indicated by the arrows
422
,
424
and may include a transverse portion
426

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