Information
-
Patent Grant
-
6794669
-
Patent Number
6,794,669
-
Date Filed
Wednesday, July 24, 200222 years ago
-
Date Issued
Tuesday, September 21, 200419 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 250 55919
- 250 5594
- 250 55916
- 356 446
-
International Classifications
-
Abstract
A media sensing apparatus includes a media sensor including a light source for generating a light beam, and a diffuse detector positioned in relation to the light source for detecting diffuse light components reflected from a sheet of print media. A media support is provided having a detection portion. The detection portion is located such that the media sensor faces the detection portion. The detection portion is configured to direct specular light components reflected from the detection portion to the diffuse detector in an absence of the sheet of print media being interposed between the media sensor and the detection portion.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to media sensors, and, more particularly, to a method for detecting an absence of print media.
2. Description of the Related Art
One form of a media sensor includes a single light source, such as a light emitting diode (LED), and a light detector, such as a phototransistor. Typically, the light detector is located on the same side of a print media as the light source. During operation, the LED directs light at a predefined angle onto a material surface of the print media, and the surface characteristics of the print media are examined in terms of the amount of light reflected from the surface that is received by the light detector. The presence of the print media is detected based upon a predetermined amount of light reflected from the media to the light detector.
Some media sensors include a pair of light detectors, one of the light detectors being positioned to sense reflected diffuse light and a second detector positioned to sense reflected specular light. Such a sensor may be used, for example, to detect and discriminate between paper media and transparency media.
Media sensors that are used to detect the type of media in an imaging device, such as an ink jet printer, optically measure the glossiness of the media using a media sensor similar to that described generally above. To measure the glossiness, a collimated beam of light is directed towards the media and a reflectance ratio (R) of the detected reflected specular light intensity and the detected diffusively scattered light intensity is calculated. The media sensor is initially calibrated by measuring a reflectance ratio (R0) on a known gloss media. A normalized reflectance ratio (Rn) is calculated using the formula: Rn=(R/R0). Normalized reflectance ratio Rn then is used to identify the media type of an unknown media by a comparison of the normalized reflectance ratio Rn to a plurality of normalized reflectance ratio Rn ranges, each range being associated with a particular type of media. For example, if the media sensor is calibrated with a perfectly diffuse media, then the normalized reflectance ratio Rn ranges might be as in the following table.
TABLE 1
|
|
Media Determination Based on Normalized Reflectance Ratio Rn
|
Rn Range
Media Type
|
|
Rn < 1.5
Coated Paper
|
1.5 ≦ Rn < 3
Plain Paper
|
3 ≦ Rn < 10
Photo Paper
|
10 ≦ Rn
Transparency
|
|
In one prior system designed to determine the print media type, it is possible to detect an empty paper tray by reflecting both specular and diffuse light components away from the sensor. However, such a design may be unreliable since the amount of detected light will be very small, similar to when a media sensor fails.
What is needed in the art is an improved media sensing apparatus that can detect the absence of print media reliably.
SUMMARY OF THE INVENTION
The present invention relates to an improved media sensing apparatus that can detect the absence of print media.
In one form thereof, the present invention is directed to a media sensing apparatus. The media sensing apparatus includes a media sensor including a light source for generating a light beam, and a diffuse detector positioned in relation to the light source for detecting diffuse light components reflected from a sheet of print media. A media support is provided having a detection portion. The detection portion is located such that the media sensor faces the detection portion. The detection portion is configured to direct specular light components reflected from the detection portion to the diffuse detector in an absence of the sheet of print media being interposed between the media sensor and the detection portion.
An advantage of the present invention is that it can be implemented relatively easily in any imaging device using a simple sensor that senses print media type.
Another advantage of the present invention is that the same sensor used to determine media type can be used to detect the absence of print media.
Another advantage is that the present invention can be implemented with little additional hardware costs in an imaging device having a preexisting sensor that senses the print media type.
BRIEF DESCRIPTION OF THE DRAWINGS
The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:
FIG. 1
is a diagrammatic representation of an imaging system embodying the present invention;
FIG. 2
is a side diagrammatic representation of a portion of the ink jet printer of the imaging system of
FIG. 1
;
FIG. 3
is a side diagrammatic representation of a media sensor known in the art;
FIG. 4
is a first embodiment of a media sensing apparatus embodying the present invention;
FIG. 5
is another embodiment of a media sensing apparatus embodying the present invention; and
FIG. 6
is another embodiment of a media sensing apparatus embodying the present invention.
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate preferred embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawings, and particularly to
FIGS. 1 and 2
, there is shown an imaging system
6
embodying the present invention. Imaging system
6
includes a computer
8
and an imaging device in the form of an ink jet printer
10
.
Computer
8
is communicatively coupled to ink jet printer
10
via a communications link
11
. Communications link
11
may be, for example, a direct electrical or optical connection, or a network connection.
Computer
8
is typical of that known in the art, and includes a display, an input device, e.g., a keyboard, a processor, and associated memory. Resident in the memory of computer
8
is printer driver software. The printer driver software places print data and print commands in a format that can be recognized by ink jet printer
10
. The format can be, for example, a data packet including print data and printing commands for a given area, such as a print swath, and including a print header that identifies the swath data.
Ink jet printer
10
includes a printhead carrier system
12
, a feed roller unit
14
, a media sensing apparatus
15
including a media sensor
16
, a controller
18
, a mid-frame
20
and a media source
21
.
Media source
21
is configured and arranged to supply individual sheets of print media
22
to feed roller unit
14
, which in turn further transports the sheets of print media
22
during a printing operation.
Printhead carrier system
12
includes a printhead carrier
24
for carrying a color printhead
26
and a black printhead
28
. A color ink reservoir
30
is provided in fluid communication with color printhead
26
, and a black ink reservoir
32
is provided in fluid communication with black printhead
28
. Printhead carrier system
12
and printheads
26
,
28
may be configured for unidirectional printing or bi-directional printing.
Printhead carrier
24
is guided by a pair of guide rods
34
. The axes
34
a
of guide rods
34
define a bi-directional scanning path for printhead carrier
24
, and thus, for convenience the bi-directional scanning path will be referred to as bi-directional scanning path
34
a
. Printhead carrier
24
is connected to a carrier transport belt
36
that is driven by a carrier motor
40
via driven pulley
42
. Carrier motor
40
has a rotating carrier motor shaft
44
that is attached to carrier pulley
42
. At the directive of controller
18
, printhead carrier
24
is transported in a reciprocating manner along guide rods
34
. Carrier motor
40
can be, for example, a direct current (DC) motor or a stepper motor.
The reciprocation of printhead carrier
24
transports ink jet printheads
26
,
28
across the sheet of print media
22
, such as paper, along bi-directional scanning path
34
a
to define a print zone
50
of printer
10
. This reciprocation occurs in a main scan direction
52
that is parallel with bi-directional scanning path
34
a
, and is also commonly referred to as the horizontal direction. During each scan of printhead carrier
24
, the sheet of print media
22
is held stationary by feed roller unit
14
.
Referring to
FIG. 2
, feed roller unit
14
includes an index roller
56
and corresponding index pinch rollers
58
. Index roller
56
is driven by a drive unit
60
(FIG.
1
). Index pinch rollers
58
apply a biasing force to hold the sheet of print media
22
in contact with respective driven index roller
56
. Drive unit
60
includes a drive source, such as a stepper motor, and an associated drive mechanism, such as a gear train or belt/pulley arrangement. Feed roller unit
14
feeds the sheet of print media
22
in a sheet feed direction
62
(see FIGS.
1
and
2
).
Controller
18
is electrically connected to printheads
26
and
28
via a printhead interface cable
70
. Controller
18
is electrically connected to carrier motor
40
via an interface cable
72
. Controller
18
is electrically connected to drive unit
60
via an interface cable
74
. Controller
18
is electrically connected to media sensor
16
via an interface cable
76
.
Controller
18
includes a microprocessor having an associated random access memory (RAM) and read only memory (ROM). Controller
18
executes program instructions to effect the printing of an image on the sheet of print media
22
, such as coated paper, plain paper, photo paper and transparency. In addition, controller
18
executes instructions to conduct media sensing, and for detecting the absence of print media, based on information received from media sensor
16
.
Referring to
FIG. 2
, media source
21
is attached, at least in part, to a frame
78
of ink jet printer
10
. Media source
21
includes a media support
80
including a media support surface
82
. A detection portion
84
of media support
80
is adjacent to media support surface
82
. Detection portion
84
may, for example, be molded with media support
80
. Detection portion
84
is a part of media sensing apparatus
15
. Detection portion
84
is located to be proximate to and opposite to media sensor
16
. In the embodiments of the present invention of
FIGS. 2
,
4
and
5
, for example, detection portion
84
defines at least one angled surface that is non-parallel to a plane
86
of media support surface
82
. As print media
22
is loaded in media support
80
, print media
22
is interposed between detection portion
84
of media support
80
and media sensor
16
.
Media sensor
16
is mounted to frame
78
via a pivot arm arrangement
88
that is biased by a spring
90
to pivot about axis
92
in the direction indicated by arrow
94
. In an alternative arrangement, pivot arm arrangement
88
may be biased simply by the forces of gravity. If no stops are provided on pivot arm arrangement
88
, when no sheet of media is present between detection portion
84
of media support
80
and media sensor
16
, media sensor
16
will contact media support surface
82
of media support
80
(see FIG.
4
). Alternatively, however, a guide roller (not shown) may be installed to limit the pivoting of pivot arm arrangement
88
such that media sensor
16
is maintained at a predefined distance from the sensing surface, for example, from the sheet of print media
22
or from detection portion
84
of media support
80
(see FIG.
5
). Such a predefined distance may be, for example, one millimeter.
Referring to
FIG. 3
, media sensor
16
may be, for example, a unitary optical sensor including a light source
100
, a specular detector
102
and a diffuse detector
104
, as is well known in the art. In its simplest form, light source
100
may include, for example, light emitting diode (LED). In a more complex form, light source
100
may further include additional optical components for generating a collimated light beam, such as light beam
110
. Each of specular detector
102
and a diffuse detector
104
can be, for example, a phototransistor.
As shown in
FIG. 3
, specular detector
102
and diffuse detector
104
are located to be on the same side of the sheet of print media
22
. Also, media sensor
16
is configured such that diffuse detector
104
is positioned between light source
100
and specular detector
102
. The operation of such sensors is well known in the art, and thus, will only briefly be discussed herein. For example, light source
100
of media sensor
16
directs light beam
110
at a predefined angle
112
with respect to a normal line
114
onto a material surface
116
of the sheet of print media
22
, and specular light component
118
reflected from material surface
116
at an angle
120
from normal line
114
is received by specular detector
102
, and a diffuse light component
122
of the light, such as that reflected at an angle
124
, for example approximately 1.0 degree from normal line
114
, is received by diffuse detector
104
. From the received amount of reflected light, a reflectance ratio R of the detected reflected specular light intensity and the detected diffusively scattered light intensity can be calculated. A normalized reflectance ratio Rn can be calculated as R divided by R0, wherein R0 is a reflectance ratio of a reference material. A media type can then be determined by comparison of Rn to ranges of predetermined normalized reflectance ratio thresholds corresponding to certain media types (see, for example, Table 1 above).
In the absence of the present invention, as in the prior art arrangement of
FIG. 3
, it is difficult to accurately detect the absence of print media
22
in a media tray, since the surface characteristics of the media support surface of the media tray can closely approximate the reflectivity of a certain type of media. For example, if the media support surface is glossy, it is possible that a normalized reflectance ratio Rn of 11.0 could be determined, thereby indicating that a sheet of transparency was located in the media tray when in fact the media tray is empty. As a further example, if the media support surface has a matte finish, it is possible that a normalized reflectance ratio Rn of 1.2 could be determined, thereby indicating that a sheet of coated paper was located in the media tray when in fact the media tray is empty. In either of the examples above, a false indication of print media being present is ascertained.
To solve this problem, referring for example to the embodiments of the present invention of
FIGS. 4 and 5
, a detection portion
84
of media support
80
is located adjacent to media support surface
82
and opposite to media sensor
16
. Detection portion
84
is configured to cause specular light components to be directed to diffuse detector
104
in the absence of print media
22
being interposed between media sensor
16
and detection portion
84
, and at least some of the diffuse light components will be received by specular detector
102
. In contrast, when a sheet of print media
22
is present between media sensor
16
and detection portion
84
, specular light components reflected from the sheet of print media
22
are directed to specular detector
102
and at least some of the diffuse light components reflected from the sheet of print media
22
are directed to diffuse detector
104
, in the manner similar to that described above with respect to FIG.
3
. With the configuration of the present invention, a normalized reflectance ratio Rn is calculated by controller
18
, and the normalized reflectance ratio Rn, which is based on the reflectivity characteristics of detection portion
84
, will be lower than the most diffuse media type that is to be detected, such as for example, coated paper. Such a normalized reflectance ratio may be, for example, in the range of about 0.01 to about 1.0, and more preferably, in a range of 0.01 to 0.5 when media sensor
16
is normalized to a perfectly diffuse reference media. Thus, the lower threshold for coated paper will be selected to be higher than the normalized reflectance ratio range attributable to detection portion
84
, and yet will be low enough to correctly classify the coated paper, such as that shown in the example of Table 2 below.
TABLE 2
|
|
Media Determination Based on Normalized Reflectance Ratio Rn
|
Rn Range
Media Type
|
|
0 < Rn < 1.0
Media Absent
|
1.0 ≦ Rn < 1.5
Coated Paper
|
1.5 ≦ Rn < 3
Plain Paper
|
3 ≦ Rn ≦ 10
Photo Paper
|
10 ≦ Rn
Transparency
|
|
Notwithstanding the values for normalized reflectance ratio Rn in Table 2, with the present invention it is possible to attain an actual Media Absent normalized reflectance ratio Rn range of, for example, 0.01 to 0.2 when surface
130
is high glossy.
In the embodiment of
FIG. 4
, media sensor
16
is positioned proximate to and facing detection portion
84
of media support
80
. Pivot arm arrangement
88
is biased by spring
90
to pivot about axis
92
in the direction indicated by arrow
94
such that, when no sheet of media is present between detection portion
84
of media support
80
and media sensor
16
, media sensor
16
will contact media support surface
82
of media support
80
.
Detection portion
84
includes an angled surface
130
that extends in a direction non-parallel to plane
86
of media support
80
at an angle
132
. Angled surface
130
may have, for example, a high gloss finish, similar to the surface characteristics of a transparency. The size and extent of angled surface
130
is greatly exaggerated in
FIG. 4
so that the details of the angular relationship of the various components can be seen more clearly. As is apparent in
FIG. 4
, plane
86
extends across detection portion
84
. Angle
132
is selected such that angled surface
130
defines a normal line
134
perpendicular to angled surface
130
that bisects the region between light source
100
and diffuse detector
104
. Light beam
110
contacts angled surface
130
at an angle of incidence
136
measured from normal line
134
, and specular light components
138
are reflected at an angle
140
measured from normal line
134
and directed to diffuse detector
104
. Angle
140
is substantially equal to angle
136
.
From
FIG. 4
, it can be seen that the direction of light beam
110
is at an angle
141
with respect to plane
86
of media support surface
82
. Accordingly, angle
132
can be calculated based on the equation: Angle
132
=90−((Σ angles
136
,
140
,
141
)+angle
141
)/2. If, for example, the sum of angles
136
,
140
and
141
is equal to 90 degrees, and angle
141
is 25 degrees, than angle
132
is 32.5 degrees.
As can be observed from the configuration of
FIG. 4
, specular light components
138
will be directed to diffuse detector
104
, and a small amount of diffuse light components, such as diffuse light components
142
, will be received by specular detector
102
. However, controller
18
processes the signals received from diffuse detector
104
and the signals received from specular detector
102
using the same reflectance ratio equation that is used in media type determination. More particularly, the reflectance ratio R is the ratio of the signal provided by specular detector
102
divided by the signal provided by diffuse detector
104
. This reflectance ratio R can then be normalized with reference to a calibrating reflectance ratio R0, such that the normalized reflectance ratio Rn is equal to R divided by R0. Thus, when controller
18
calculates the normalized reflectance ratio Rn in the absence of print media, an extremely low Rn value will be calculated. For example, when controller
18
calculates a reflectance ratio of signals corresponding to diffuse light components
142
and signals corresponding to specular light components
138
from detection portion
84
as detected by specular detector
102
and diffuse detector
104
, respectively, of media sensor
16
, in the absence of a sheet of print media
22
, a low normalized reflectance ratio in a range, for example, of 0.01 to 0.5 can be determined.
As shown in the embodiment of
FIG. 4
, detection portion
84
includes a plurality of angled surfaces, i.e., a plurality of facets, each extending at an angle in a direction non-parallel to plane
86
of media support
80
at angle
132
. The size of the plurality of angled surfaces, such as angled surface
130
, is greatly exaggerated in
FIG. 4
so that the details of the angular relationship of the various components can be seen more clearly. The plurality of angled surfaces may be populated across detection portion
84
at, for example, at a rate of about 25 to about 50 angled surfaces per inch (about 10 to about 20 angled surface per centimeter). By providing a plurality of angled surfaces like that of angled surface
130
, the exact positioning of media sensor
16
with respect to detection portion
84
is less critical, since shifting media sensor
16
along plane
86
will simply move the location of impingement of light beam
110
with detection portion
84
from one angled surface to another without affecting the operation of media sensor apparatus
15
. Also, when an angled surface
130
is smaller than the beam width of light beam
110
, then the light will be simultaneously reflected from multiple facets, i.e., multiple angled surfaces
130
, of detection portion
84
. The actual number of angled surfaces per unit distance can be selected based on machining tolerances to provide as many facets as possible, while preserving a sharp cut off at the distal ends, i.e., the points
144
of the angled surfaces, such as angled surface
130
. It is contemplated that alternatively angled surfaces
130
may be located such that the points
144
are positioned at or below media support surface
82
.
The embodiment of
FIG. 5
differs from that of
FIG. 4
in that a gap
146
is formed between media sensor
16
and media support surface
82
so as to space media sensor
16
from media support surface
82
, even in the absence of a sheet of print media between media sensor
16
and media support surface
82
. The operation of the embodiment of
FIG. 5
remains substantially the same as that of the embodiment of
FIG. 4
, since the geometry of light reflections remain the same.
FIG. 6
shows another media sensor apparatus
148
embodying the present invention having a media support
150
that can replace the media support
80
of
FIGS. 1
,
2
,
4
and
5
. Media support
150
has a media support surface
152
that extends along a plane
154
. Media support
150
further includes a first recessed portion
156
, a second recessed portion
158
and a detection portion
160
. Detection portion
160
is positioned between first recessed portion
156
and second recessed portion
158
. First recessed portion
156
defines a first recessed surface
162
, and second recessed portion
158
defines a second recessed surface
164
.
Media sensor
16
is positioned proximate to and facing detection portion
160
of media support
150
, and pivot arm arrangement
88
is biased by spring
90
to pivot about axis
92
in the direction indicated by arrow
94
such that, when no sheet of media is present between detection portion
160
of media support
150
and media sensor
16
, media sensor
16
will contact recessed surfaces
162
and
164
of media support
150
. Recessed surfaces
162
and
164
provide support for media sensor
16
below plane
154
of media support
150
.
Detection portion
160
includes an angled surface
166
that extends in a direction non-parallel to plane
154
of media support
150
at an angle
168
. As is apparent in
FIG. 6
, plane
154
extends across detection portion
160
. Angle
168
is selected such that angled surface
166
defines a normal line
170
that bisects the region between light source
100
and diffuse detector
104
. Light beam
110
contacts angled surface
130
at an angle of incidence
172
measured from normal line
170
, and specular light components
174
are reflected at an angle
176
measured from normal line
170
and directed to diffuse detector
104
. Angle
176
is substantially equal to angle
172
. In the detection portion configuration of
FIG. 6
, a distal point
178
of angled surface
166
of detection portion
160
is at, or alternatively below, plane
154
of media support
150
. Thus, in this arrangement, the sheet of print media
22
will not be elevated above plane
154
of media support
150
when the sheet of print media
22
is present between media sensor
16
and detection portion
160
of media support
150
.
As can be observed from
FIG. 6
, in the absence of the sheet of print media
22
, specular light components
174
will be directed to diffuse detector
104
, and small amount of diffuse light components, such as diffuse light components
180
, will be received by specular detector
102
. As such, when controller
18
calculates the normalized reflectance ratio Rn in the absence of print media, as described above, an extremely low Rn value will be calculated, since controller
18
considers the signals received from diffuse detector
104
to be representative of the detected diffuse light components for purposes of the calculation. For example, when controller
18
calculates a reflectance ratio of signals corresponding to diffuse light components
180
and specular light components
174
as detected by specular detector
102
and diffuse detector
104
, respectively, of media sensor
16
, in the absence of a sheet of print media
22
, a normalized reflectance ratio lower than that of coated media, in a range of 0.01 to 0.5, can be determined.
While this invention has been described with respect to preferred embodiments, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.
Claims
- 1. A media sensing apparatus, comprising:a media sensor including a light source for generating a light beam, and a diffuse detector positioned in relation to said light source for detecting diffuse light components reflected from a sheet of print media; and a media support having a detection portion, said media sensor being variably spaced from said media support, said detection portion being located such that said media sensor faces said detection portion, said detection portion being configured to direct specular light components reflected from said detection portion to said diffuse detector in an absence of said sheet of print media being interposed between said media sensor and said detection portion.
- 2. The media sensing apparatus of claim 1, said media sensing apparatus being incorporated into an imaging device.
- 3. The media sensing apparatus of claim 1, wherein said detection portion comprises an angled surface that extends at an angle non-parallel to a plane of said media support.
- 4. The media sensing apparatus of claim 3, wherein said plane extends along a surface of said media support and across said detection portion.
- 5. The media sensing apparatus of claim 3, wherein said light beam contacts said angled surface at a first angle measured from a normal line of said angled surface and said specular light components are reflected at a second angle measured from said normal line, said second angle being substantially equal to said first angle.
- 6. The media sensing apparatus of claim 1, wherein said detection portion comprises a plurality of angled surfaces, wherein at least a portion of said plurality of angled surfaces extend at an angle non-parallel to a plane of a surface of said media support.
- 7. The media sensing apparatus of claim 1, wherein said media support includes a first recessed portion and a second recessed portion, said detection portion being positioned between said first recessed portion and said second recessed portion.
- 8. A media sensing apparatus, comprising:a media sensor including a light source for generating a light beam, and a diffuse detector positioned in relation to said light source for detecting diffuse light components reflected from a sheet of print media; and a media support having a detection portion, said media sensor being variably spaced from said media support, said detection portion being located such that said media sensor faces said detection portion, said detection portion being configured to direct specular light components reflected from said detection portion to said diffuse detector in an absence of said sheet of print media being interposed between said media sensor and said detection portion, said media support including a first recessed portion and a second recessed portion, said detection portion being positioned between said first recessed portion and said second recessed portion, wherein said media sensor is configured to contact at least one of a first recessed surface defined by said first recessed portion and a second recessed surface defined by said second recessed portion in the absence of said sheet of print media.
- 9. The media sensing apparatus of claim 7, wherein each of said first recessed portion and said second recessed portion define a respective recessed surface located below a plane of a media support surface of said media support.
- 10. The media sensing apparatus of claim 1, wherein said media sensor is configured to be spaced from said media support even in the absence of said sheet of print media.
- 11. A media sensing apparatus, comprising:a media sensor including a light source for generating a light beam, and a diffuse detector positioned in relation to said light source for detecting diffuse light components reflected from a sheet of print media; a media support having a detection portion, said detection portion being located such that said media sensor faces said detection portion, said detection portion being configured to direct specular light components reflected from said detection portion to said diffuse detector in an absence of said sheet of print media being interposed between said media sensor and said detection portion; a specular detector located in said media sensor and positioned in relation to said light source for detecting specular light components reflected from said sheet of print media, said detection portion being configured to cause at least some diffuse light components reflected from said detection portion to be received by said specular detector in the absence of said sheet of print media; and a controller for calculating a normalized reflectance ratio of said specular light components detected by said diffuse detector and said diffuse light components detected by said specular detector, wherein in the absence of said sheet of print media, said normalized reflectance ratio is lower than that of coated paper.
- 12. The media sensing apparatus of claim 11, said media sensor being normalized to a perfectly diffuse media, wherein in the absence of said sheet of print media, said normalized reflectance ratio is in a range of 0.01 to 0.5.
- 13. A media sensing apparatus, comprising:a media sensor including a light source for generating a light beam, and a diffuse detector positioned in relation to said light source for detecting diffuse light components reflected from a sheet of print media; and a media support having a detection portion, said media sensor being variably spaced from said media support, said detection portion being located such that said media sensor faces said detection portion, said detection portion being configured to direct specular light components reflected from said detection portion to said diffuse detector in an absence of said sheet of print media being interposed between said media sensor and said detection portion, and said detection portion comprising a plurality of angled surfaces, wherein at least a portion of said plurality of angled surfaces extend at an angle non-parallel to a plane of a surface of said media support, wherein said plurality of angled surfaces are populated at a rate in a range of about 10 to about 20 angled surfaces per centimeter.
- 14. A media sensing apparatus, comprising:a media sensor including a light source for generating a light beam, and a diffuse detector positioned in relation to said light source for detecting diffuse light components reflected from a sheet of print media; and a media support having a detection portion, said media sensor being variably spaced from said media support, said detection portion being located such that said media sensor faces said detection portion, said detection portion being configured to direct specular light components reflected from said detection portion to said diffuse detector in an absence of said sheet of print media being interposed between said media sensor and said detection portion, wherein said media sensor is configured to contact said media support in the absence of said sheet of print media.
- 15. A media sensing apparatus, comprising:a media sensor including a light source for generating a light beam, and a diffuse detector positioned in relation to said light source for detecting diffuse light components reflected from a sheet of print media; a media support having a detection portion, said detection portion being located such that said media sensor faces said detection portion, said detection portion being configured to direct specular light components reflected from said detection portion to said diffuse detector in an absence of said sheet of print media being interposed between said media sensor and said detection portion; a specular detector located in said media sensor and positioned in relation to said light source for detecting specular light components reflected from said sheet of print media, said detection portion being configured to cause at least some diffuse light components reflected from said detection portion to be received by said specular detector in the absence of said sheet of print media; and a controller for calculating a normalized reflectance ratio of said specular light components detected by said diffuse detector and said diffuse light components detected by said specular detector in order to determine said absence of said sheet of print media.
US Referenced Citations (36)
Foreign Referenced Citations (1)
Number |
Date |
Country |
07-304214 |
Nov 1995 |
JP |