WO2015178918A1

WO2015178918A1 - Calibration strip

Info

Publication number: WO2015178918A1
Application number: PCT/US2014/039194
Authority: WO
Inventors: Edward Anthony HILL; Ryan M. Smith; Dean Richtsmeier
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2014-05-22
Filing date: 2014-05-22
Publication date: 2015-11-26

Abstract

A scanner is disclosed. The scanner has a calibration strip comprising a generally rectangular glass plate, a reflection layer and an adhesive layer. The glass plate has a thickness of 0.4 mm or less. The reflection layer is coupled to one surface of the glass plate. The adhesive layer is coupled to the other surface of the reflection layer.

Description

Calibration Strip

BACKGROUND

[0001] Scanners are used to create digital copies of documents or images. Tiiere are many types of scanners , for example sheet-feed scanners, flatbed scamiers, stand alone scanners and scanners integrated into multifunctional printers (MFPs). Almost all scanners calibrate the scan sensor using a calibration strip to improve the image quality of the scan.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] FIG. 1 is a cutaway isometric view of an example seamier.

[0003] FIG. 2 is a cutaway side view of the example scanner from figure 1.

[0004] FIG. 3 is a close-up side view of the example scanner from figure 2.

[0005] FIG. 4 is an isometric view of an example cover glass.

[0006] FIG. 5 is a flow chart for an example method of fabricating a calibration strip.

DETAILED DESCRIPTION

[0007] Sheet-feed scanners and flatbed scanners are two of the many different types of scanners. A sheet-feed seamier uses an automatic document feeder (ADF) to feed documents past a scan sensor located in a fixed position. The scan sensor captures an image of the side of the document facing the scan sensor . Typically the scan sensor has a direct view of the document (i.e. there is nothing between the document and the scan sensor). In this application, a scan sensor that views the user objects to be scanned directly will be known as a direct view scan sensor. A user object is any object a uses wishes to scan, for example a document, a small object, a book or the like.

[0008] A flatbed seamier has a transparent scan platen typically fabricated from glass. Objects to be scanned are placed on the top surface of the platen. The flatbed scanner has a scan sensor that travels underneath the platen during the scan. The scan sensor captures images, of the objects on the platen through the transparent platen during a scan. In this application, a scan sensor that views the user objects to he scanned through a scan platen will be known as a flatbed scan sensor.

[0009] There are a nimiher of different types of scan sensors. Some types of scan sensors have a large depth of field and a large depth of uniform illumination, for example a reduction optics scan sensor. These types of scanners can accurately capture images with small amounts of height variation, for example a wrinkled page or small 3-D objects. These types of sensors are typically used in flatbed scanners.

[0010] Other types of scan sensors have a limited depth of field and a limited depth of iUumination, for example a contact image sensor. These types of sensors can only accurately capture images of objects in a single image plain, for example a fiat sheet of paper. These types of sensors are typically used in sheet-feed scanners. These types of sensors are also typic ally cheaper than sensors with a large depth of field and a large depth of uniform illumination.

[0011] Some scanners can scan only one side of a page (single sided scanners) and other scanners can scan both sides of a page (duplex scanners). Single sided scanners typically have only one scan sensor. Single sided scanners can be sheet-feed scanners or flatbed scanners.

[0012] Some duplex scanners only have one scan sensor. These types of duplex scanners rely on an automatic document feeder (ADF) that moves the page past the scan sensor with a first side of the page facing the scan sensor. The ADF then moves the page past the scan sensor a second time with the other side of the page facing the scan sensor. Newer duplex scanners have two scan sensors. In such scanners, as the paper is moved past the scan sensors by the ADF, one of the scan sensors scans the first side of the page and the other scan sensor scans the other side of the page.

[0013] When the duplex scanner is only a sheet-feed scanner, both scan sensors are typically fixed in place. Some duplex scanners also have a flatbed scanning area. Typically the flatbed scanning area is a transparent platen where the user can place items to he scanned. One of the two scan sensors moves underneath the platen to scan items placed on the platen. The other scan sensor is typically fixed in place.

[0014] Scanners typically calibrate their scan sensor using a calibration strip. A calibration strip is typically a uniformly colored white strip viewable by the scan sensor. The scan sensor captures an image of the calibration strip and uses die image of the calibration strip to compensate for variations in the sensor^'s response. If the calibration strip becomes damaged or dirty, the images of the damaged or dirty area may cause the calibration routine to fail and can cause streaks or defects when scanning user objects.

[0015] Because of this problem, the calibration strip is typically covered by a protecting layer of some type. For scanners that use a flatbed scan sensor, the calibration strip is typically located on the top surface of the transparent scan platen. The flatbed scan sensor captures an image of the bottom surface of the calibration strip through the glass platen during calibration. The glass platen protects the bottom surface of the calibration strip from damage and/or dirt.

[0016] For scanners that use a direct view scan sensor, the calibration strip is typically located underneath the direct view scan sensor. During a user scan, the document passes between the direct view scan sensor and the calibration strip. During a calibration scan, no documents are fed through the ADF and the direct view scan sensor captures an image of the calibration strip .

[0017] In some cases the calibration strip for the direct view scan sensor is covered/protected by a glass plate on top of the calibration strip. During a calibration scan the direct view scan sensor captures an image of the top surface of the calibration strip through the glass layer. This works well with scan sensors that have a large depth of field and a large depth of uniform illumination. However the thickness of the glass plate causes calibration problems when used with scan sensors that have a limited depth of field and a narrow area of uniform illumination. When using a direct view scan sensor with a limited depth of field and a narrow area of uniform illumination, a thin layer of flexible material, for example Mylar, is typically located on top of the calibration strip as protection. Unfortunately, the Mylar can be damaged as the docmiient is moved past the Mylar cover. [0018] In one example, a scanner with a direct view scan sensor with a limited depth of field and a narrow area of uniform illumination has a calibration strip c overed by a thin cover glass. The cover glass is 0.4 nan or less in thickness. The surface of the glass is significantly harder than the surface of a flexible material and is therefore less susceptible to damage from pages being fed through the ADF. hi one example the top surface of the calibration strip is attached to the bottom surface of the glass cover and the bottom surface of the calibration strip is attached to an ADF ramp.

[0019] Figure 1 is a cutaway isometric view of an example duplex scanner.

Scanner 100 comprises a scanner base 102. a top bezel 104. a flatbed scan platen 106, a flatbed scan sensor 108, an automatic document feeder (ADF) exit ramp 120, a flatbed calibration strip 126, an ADF step glass 1 14 and an ADF calibration strip 122. Scanner base 102 is generally a hollow rectangular box that supports the flatbed scan platen 106 and the ADF step glass 114 around their edges. Top bezel 104 which fits on top of the flatbed scan platen 106 and the ADF step glass 114, attaches to the scanner base 102 thereby holding the flatbed scan platen 106 and the ADF step glass 114 in place. In this example, the ADF exit ramp 120 is formed as part of the top bezel 104, and fits between the scan platen 106 and the ADF step glass 114.

[0020] The flatbed scan platen 106 is fabricated from a transparent material, for example glass. The top surface of the flatbed scan platen forms a flatbed scan area. The ADF step glass 114 is also formed from a transparent material, typically glass. The ADF step glass 114 forms an ADF scan area for the flatbed scan sensor.

[0021] In this example, the ADF calibration strip i 22 is positioned on top of the

ADF exit ramp 120. The flatbed calibration strip 126 is located on the top surface of the scan platen 106, underneath the ADF exit ramp 120. Scanner base 102 also supports a drive system (not shown for clarity) that moves the flatbed scan sensor 108 along the underside of the ADF step glass 114 and the flatbed scan platen 106. The flatbed scan sensor i 08 is shown located at the ADF scan position. An ADF is positioned on the top side of scanner base 102 above the ADF step glass 114.

[0022] The ADF comprises an ADF feed guide 112 and an ADF scan sensor 110.

The ADF may also comprise a housing, an input tray, and output tray and a paper transport system containing motors, belts, paper picking mechanisms and the like, bet these items are not shown for clarity, in some examples the ADF is. integrated as part of the scanner, in other examples the ADF may be removably detachable and may be optional, ^'equipment, for the scanner, for example an accessory. An ADF that is removably detachable is one that is configured such that an end user can install and remove the ADF from the scanner, typically without, tools.

[0023] The ADF scan sensor 1 10 is fixed in place in the ADF and is positioned above ihe ADF calibration strip 122. ADF exit ramp 120 is positioned between the ADF step glass 114 and the scan platen 106 and is part of the top bezel 104. ADF exit ramp 114 helps guide pages through the ADF paper path and into an output tray (not shown for clarity). A page 1 16 is shown in the ADF paper path. The paper feeding direction during a scan is shown by arrows 124. The ADF paper path goes from an input tray, around ADF feed guide 112, underneath the ADF scan sensor 110, up the ADF exit ramp 1.20 and into an output tray .

[0024] During an ADF scan the flatbed scan sensor 108 is positioned undernea th the ADF step glass 1 14 (as shown). As the page moves through the ADF paper path the flatbed scan sensor 108 remains stationary and captures an image of the downward facing side of the page as it passes above the flatbed scan sensor 108. The duplex scan sensor 1 10 is fixed in place. The paper path travels between the duplex scan sensor and the ADF exit ramp 120. The duplex scan sensor 1 10 captures an image of the upward facing side of the page as it passes underneath the duplex scan sensor 1 10.

[0025] During a flatbed scan, the page would be placed onto the flatbed scan platen 106 and the flatbed scan sensor 108 would move along the length of the flatbed scan platen capturing an image of the downward facing side of the page. The duplex scan sensor 1 10 is not used during a flatbed scan.

[0026] Most scanners calibrate the scan sensors before scanning. Some scanners only do a calibration at power-on, some scanners calibrate before each multi-page scan job, and some scanners calibrate before each scan. For scanners that have a scan head fixed in place, the calibration position is the same as the scan position. For scanners that have a scan head that moves during a scan, the calibration position is typically different than the scan position. Figure 2 is a cutaway side view of the example duplex scanner from figure 1.

[0027] In figure 2 the flatbed scan sensor 108 is shown located at the ADF scan position. An ADF is positioned on the top side of scanner base 102 above the ADF step glass 114. When there are no pages located in the ADF paper path (as shown), the ADF scan sensor 110 can scan the ADF calibration strip 122.

[0028] To calibrate the scanner, both the ADF scan sensor 110 and the flatbed scan sensor 108 may be calibrated. Calibrating a scan sensor typically involves scanning a calibration strip that runs along the length of the scan sensor. The calibration strip is typically a white strip that has a known reflectance and color. The calibration strip may be scanned twice, once with no light illuminating the calibration strip 122 (typically called a dark scan) and once with light iihiinmating the calibration strip 122. The data fr om the two scans is typically used to adjust a gain and offset for each pixel in the scan sensor.

[0029] When calibrating the ADF scan sensor, a scan with the ADF scan sensor is done without feeding a page through the ADF. Because the ADF scan sensor is fixed in position above the calibration strip, the ADF scan sensor can "see" the calibration strip when there are no pages in the ADF paper path.

[0030] When calibrating the flatbed scan sensor, the flatbed scan sensor is moved to a flatbed calibration position underneath the flatbed calibration strip 126. hi some examples the flatbed scan sensor may move during a calibration scan. This causes the flatbed scan sensor to sweep across a section of the calibration str ip, minimizing the effect of dust located on the calibration strip, In other examples, the flatbed scan sensor may remain fixed in position dining a calibration scan. Once the scan sensors are calibrated, the flatbed scan sensor is moved to the ADF scan location (shown in figure 2) and a page is fed through the ADF as the two scan sensors capture an image of the top and bottom of the page.

[0031] In one example the ADF scan sensor uses a contact image sensor (CIS).

Contact image sensors have a limited depth of field. CIS sensors also have a limited depth of illiinihiatioii due to the directional nature of the light source used in most CIS sensors. In addition the intensity of the light used to illuminate the area being scanned dr ops off as the cube (x³) of the distance between the light and the area being scanned. Tliere fore when the calibration distance is different than the scan distance, the quality of the calibration may degrade. The larger the difference in distances, the less accurate the calibration becomes.

[0032] In some examples the flatbed scan sensor may also use a CIS. In other examples the flatbed scan sensor may use a folded optical system, or other types of optical systems. Folded optical systems typically have a much larger depth of field as compared to a CIS. In addition folded optical systems typically use a broadband light source that produces a gr eater depth of illumination. Because of these differences, a folded optical system is typically less sensitive to differences between the calibration distance and the scan distance.

[0033] Figure 3 is a close-up view of the example ADF ramp from figure 2. In this example ADF ramp 120 is fabricated as part of top bezel 104. In. other examples ADF ramp may be a separate part. In this example. ADF ramp 120 is fabricated from a plastic material, but in other examples it may be iabiicated from a different material, for example metal. In this example ADF ramp 120 fits between the ADF step glass 114 and scan platen 106. In tin^'s example. ADF calibration strip 122 is mounted on top of ADF ramp 120 adjacent to the ADF step glass 114. In other examples, ADF calibration strip may be mounted in a different location, for example on the top surface of the ADF step glass 114.

[0034] In this example, ADF calibration strip 122 comprises a cover glass 330. a reflecting layer 332 and an adhesive layer 334. Cover glass 330 is a generally rectangular glass plate with a thickness d2. In one example, thickness d2 is 0.4 mm or less. In some examples, reflecting layer 322 may be a layer of paint bonded or silkscreened onto the surface of cover glass 330. In other examples, reflecting layer 322 may be a thin sheet of plastic or the like. Reflecting layer 322 has a brightness (L*) when measured through the cover glass 330. In one example the brightness of the reflecting surface is L* = 90 or greater. In this example, adhesive layer is a thin layer of 3M's ® 467MP or 9492MP. In other examples, adhesive layer may be a strip of double-sided tape. The three layers of the ADF calibration strip 122 have a total thickness d3. In some examples the thickness d3 is 0.4 ami or less.

[0035] The top sur face of cover glass 330 is below die top surface of ADF step glass 114 by distance dl. hi some examples distance dl is between 0,20 and 0.60 mm, for example 0.40 mm. A page 116 is shown in the paper path of the ADF. The scanning direction in the paper path is shown by arrow 124. The leading edge 340 of the page is just past the edge of the ADF step glass 114. Because the top surface of cover glass 320 is below the top surface of the ADF step glass 114, the leading edge 340 of page 116 cannot catch on the edge of cover glass 330. As the leading edge of the page contacts the ADF ramp 120. the page is guided up the ramp and into an output hay (not shown for clarity).

[0036] Figure 4 is an isometric view of an example cover glass 330. Cover glass

330 is a generally rectangular glass plate with a thickness d2. a width W and a length L. A generally rectangular glass plate is a piece of glass that has a thickness that is no larger than l/8^th of either the width or length of the plate. In this example the generally rectangular glass plate has a thickness of 0.4 mm, a length of 240 nun and a width of 9 mm.

[0037] Figure 5 is a flow chart for an example method of fabricating a calibration strip. At 550 a generally rectangular glass plate is provided. At 5520 a reflection layer is attached to one side of the glass plate. The reflecting layer may be a layer of paint bonded or silkscreeiied onto the surface of the glass plate. In other examples, the reflecting layer may be a thin sheet of plastic or the like. The reflecting layer has a brightness (L*) when measured through the glass plate. In one example the brightness of the reflecting surface is L* = 90 or gr eater.

[0038] At 554 a layer of adhesive is attached to the reflecting layer. In one example, the adhesive layer is a thin layer of 3M's ® 467MP or 9492MP. In other examples, the adhesive layer may be a strip of double-sided tape. The total thickness of the glass plate, the reflection layer and the adhesive layer, is 0.4 mm or less. [0039] A duplex flatbed scanner was used in the examples above. Other types of scaruiers may also have one or more of the calibration strips as described above, for example a duplex sheet-feed scanner, a single-sided sheet -feed scanner or the like. The scanners described above may also be integrated into a multifunction peripheral (MFP). A multifunction peripheral (MFP) is a device that typically contains a printer and an imaging system, typically a scanner. The MFP can be used as a printer, a scanner, a copier, a facsimile machine (FAX) or the like. MFPs are also called all-in-one devices (AiO), multifunction devices, mimiiuiiction printers or the like.

Claims

[0040] CLAIMS What is claimed is:

1. A scanner, comprising:

a calibration strip, the calibration stop comprising:

a generally rectangular glass piate having a first surface and a second surface opposite the first surface, the glass plate having a thickness 0.4 mm or less;

a reflection layer having a first surface and a second surface, opposite the first surface, the first surface coupled to the second surface of the glass plate, where the first surface of the reflection layer is to calibrate a scan sensor;

a layer of adhesive attached to the second surface of the reflection layer.

2. The scanner of claim 1 , further comprising;

an automatic document feeder (ADF) exit ramp having a top surface, the calibration strip coupled to the top smiace of the exit ramp with the layer of adhesive.

3. The scanner of claim 2, further comprising;

an automatic document feeder (ADF) step glass having a top surface, the ADF step glass positioned adjacent to the calibration strip located on the top smiace of the ADF ramp;

a distance D between the top surface of the ADF step glass and the first surface of the glass plate, where distance D is between 0.20 tnm and 0.60 mm.

4. The scanner of claim 2, wherein the ADF exit ramp is fabricated from plastic .

5. The scanner of claim 1, wherein a total thickness of die calibration strip, including the gla ss piate, the reflection layer and the adhesive layer, is 0.4 mm or less.

6. The scanner of claim 1 , comprising a scan sensor wherein the scan sensor is a contact image sensor (CIS).

7. The scanner of claim 1 , wherem tlie reflecting layer is fabricated from either a molded plastic strip, a stamped plastic sheet or paint.

8. The scanner of claim 1 , wherein the seamier is part of a multifunction peripheral (MFP).

9. The scanner of claim 1, further comprising:

an ADF. the scan sensor fixed in position in the ADF, the ADF coupled to the seamier such that the scan sensor is located above, and can view, the first surface of the reflection layer;

a flatbed scan sensor movabfy positioned along a bottom surface of a scan platen.

10. The scanner of claim 9, wherein the ADF is removably detachable from the seamier.

11. A scanner, comprising:

a calibration strip, the calibration strip comprising:

a generally rectangular glass plate having a first surface and a second surface opposite the first surface;

a reflection layer having a first surface and a second surface, opposite the first surface,, the first surface coupled to the second surface of the glass plate, where the first surface of the reflection layer is to calibrate a scan sensor;

a layer of adhesive attached to the second surface of the reflection layer; wherein a total thickness of the calibration strip, including the glass plate, the reflection layer and the adhesive layer, is 0.4 mm or less;

an automatic document feeder (ADF) exit ramp having a top surface, the calibration strip coupled to the top surfac e of the exit ramp with the layer of adhesive.

12. The scanner of claim 11 , further comprising: an automatic document feeder (ADF) step glass having a top surface, the ADF step glass positioned adjacent to the calibration strip located on the top surface of the ADF ramp;

a distance D between the top surface of the ADF step glass and the first surface of the glass plate, where distance D is between 0.20 and 0.60 mm.

13. The scanner of claim 1 1 , wherein the scan sensor uses a contact image sensor (CIS).

14. The scanner of claim 11, wherein the scanner is part of a multifunction peripheral (MFP).

15. A method of manufacturing a calibration ship, comprising;

providing a generally rectangular glass plate having a first surface and a second surface opposite the first surface;

attaching a first surface of a reflection layer to the second surface of the glass pla te, where the first smiace of the reilection layer is to calibrate a scan sensor;

attaching a layer of adhesive to a second surface of the reflection layer, where the second surface of the reflection layer is opposite the first surface of the reflection layer; wherein a total thickness of the glass plate, the reflection layer and the adhesive layer, is 0.4 mm or less.