WO2012013499A1

WO2012013499A1 - Double-sided document scanner, and associated control method

Info

Publication number: WO2012013499A1
Application number: PCT/EP2011/061982
Authority: WO
Inventors: Pierre Sabatier
Original assignee: Sagemcom Documents Sas
Priority date: 2010-07-30
Filing date: 2011-07-13
Publication date: 2012-02-02
Also published as: EP2599294A1; FR2963527B1; CN103053152B; FR2963527A1; CN103053152A

Abstract

The invention relates to a scanner for scanning the front and back of a document (2), comprising: a module (10) located on the front side of the document (2) and comprising means (3) for illuminating the front of document; and a module (11) located on the back side of the document (2) and comprising a means (3) for illuminating the back of the document; wherein the scanner is characterized in that each module (10, 11) is located opposite the other module (10, 11), and in that said scanner further comprises a controller (6) that is connected to the illuminating means (3) of each module (10, 11) and that is capable of controlling the illuminating means (3) of each module (10, 11) such that the illuminating means (3) of the module (10) located on the front side of the document (2) illuminates the front of the document when the illuminating means of the module (11) located on the back side of the document (2) is not illuminating the back of the document, and vice versa. The invention also relates to a method for controlling such a scanner.

Description

Two-sided scanner of a document, and associated control method

GENERAL TECHNICAL FIELD

The invention relates to a scanner for scanning the front and the back of a document, comprising a module located on the side of a recto of the document, comprising a lighting of the front of the document, and a module located on the side of a back of the document. document, with illumination on the back of the document.

The invention also relates to a method for controlling such a scanner.

STATE OF THE ART

Multifunction machines (including photocopying, facsimile, or scan functions for example) including scanners are known.

The scanners of these machines conventionally comprise modules comprising image sensors.

Among these sensors, the image sensors of the known type CIS (Contact Image Sensor) are the most used because they allow a great compactness of the scanners.

As shown in FIG. 1B in elevation, a CIS image sensor 100 of a module is generally in the form of an elongated housing 1000.

As also shown in FIG. 1A in section, the sensor 100 has a lighting 3 in general in the form of an elongate illumination grating also placed in the housing 1000 and comprising light-emitting diodes (or "LEDs"). according to the terminology used by those skilled in the art). The diodes are red, green, and blue. Each line of a document 2 to be scanned is substantially illuminated by the diodes of the three colors as it moves in the scanner, each of the three diodes illuminating the line alternately. The scrolling of the document 2 to be scanned is conventionally performed by scroll rollers 7. The sensor 100 also comprises an optical rod 4, also of elongated shape, placed in the housing 1000, recovering the reflections of the colors on the document 2.

A detector 5, visible in FIG. 1A, in section, receives the reflections of the colors at the output of the optical bar 4, for a posterior processing.

What has just been described is done for the scan of a page of a sheet of the document 2 (for example the front side).

To scan the 2-sided document 2, the scanner generally comprises two modules 10 and 11, as shown in FIG. 1A, and thus a sensor 100 for the front of the document 2, and a sensor 101 for the back of the document. 2.

It is possible that the illumination of one of the sensors 100 or 101 acts or interferes with the operation of the other, for example by transparency for a document 2 formed of a thin paper, namely that the illumination of the front of the document is perceived by the dedicated detector on the back of document 2.

To avoid this problem, a known conventional solution is to shift the two sensors relative to each other, in a direction X scrolling document 2. The two sensors are therefore isolated from one another.

However, the aforementioned conventional solution has at least one disadvantage: the offset of the two sensors in the X direction of movement of the document 2 causes an increase in distance L between the rollers 7.

However, the distance L between the rollers 7 determines the smallest dimension of a document 2 that can be scanned. Indeed, if a document 2 has a dimension of length less than the distance L, it remains motionless inside the scanner once it is in front of the two sensors 100 and 101, because it is then driven by none of the drive rollers 7.

The scanners of the prior art are of a relatively large spatial size, and do not allow to scan documents of small dimensions. PRESENTATION OF THE INVENTION

The invention proposes to overcome at least one of these disadvantages.

For this purpose, according to the invention, a scanner according to claim 1 is proposed.

The invention is advantageously completed by the features of claims 2 to 4, taken alone or in any of their technically possible combination.

The invention also relates to a method for controlling such a scanner.

The invention has many advantages.

A distance I between the drive rollers is reduced compared to the distance L of the prior art. The distance I is of the order of 30 mm, the scanner according to the invention for scanning small documents, for example subway tickets.

The scanners of the invention are space-saving compared to the prior art.

Of course, the scanner allows a two-sided scan of the document to be scanned, without the illumination of one of the sensors acting or interfering with the operation of the other, even by transparency for rather fine papers. The illumination of the front of the document is not perceived by the detector dedicated to the back of the document to be scanned, and vice versa.

The invention makes it possible not to have to mount any optical insulation between the two modules.

PRESENTATION OF FIGURES

Other features, objects and advantages of the invention will emerge from the description which follows, which is purely illustrative and nonlimiting, and which should be read with reference to the appended drawings in which:

- Figures 1A and 1B, already commented, schematically show sensors known from the prior art;

- Figures 2 and 3 show schematically scanners according to the invention; FIGS. 4, 5 and 6 schematically represent control chronograms according to the invention, during the scan of a line of a document to be scanned.

In all the figures, similar elements bear identical reference numerals.

DETAILED DESCRIPTION

Figures 2 and 3 show schematically examples of scanners according to the invention.

A scanner conventionally comprises rollers 7 for driving a document 2 to be scanned, the document 2 comprising a front and a back. The rollers 7 are rotatably mounted about an axis.

We want to scan the front and back of document 2.

The scanner thus comprises a module 10 located on the side of a front of the document 2 and a module 1 1 located on the side of a back of the document 2.

The modules 10 and 11 may be separate elements or be monobloc, provided of course to be able to scroll the document 2 in an X scroll direction.

In order to reduce a distance I between the axes of rotation of the rollers 7, each module 10 or 1 1 is located substantially facing the other, that is to say with a covering area Δ with respect to the X direction as shown in Figure 2.

Preferably, the module 10 and the module 1 1 are centered one and the other with respect to a Y axis perpendicular to the X direction, as shown in Figure 3. The recovery is total.

In all cases, the distance I is less than the distance L between the rolls of the scanners of the prior art. The distance I is of the order of 15 mm.

Conventionally, each module 10 or 1 1 comprises an optical detector 5. Each optical detector is comprised of silicon chips implementing either CMOS (Complementary Metal-oxide Semiconductor) technology or CCD (charge-coupled device) technology. The detector has the same length as a width of the document to be scanned (scale 1: 1). The resolution is often expressed in dots per inch ("dots per inch" or dpi in English), and can typically range from 200 dpi to 1200 dpi. For example, at 200 dpi, the pixel size is about 127 μιη.

Each module 10 or 1 1 comprises a lighting 3 of the document 2 to be scanned. The lighting 3 of the module 10 is adapted to illuminate the front of the document 2, the lighting 3 of the module 1 1 being adapted to illuminate the back of the document 2.

In order to prevent the illumination of one of the modules 10 or 11 acting or interfering with the operation of the other module, even by transparency for a document made of thin paper, the scanner also comprises a control 6 connected to the lighting 3 of each module 10 or 1 1.

The control 6 is adapted to control the lighting 3 of each module 10 or 1 1, so that the front only is illuminated, or the back only is illuminated. In other words, the control 6 is adapted to control the illumination 3 of each module 10 or 1 1 so that the illumination 3 of the module 10 located on the side of the front of the document 2 illuminates the front of the document when the lighting 3 of the module 1 1 located on the back side of the document 2 does not illuminate the back of the document.

Conversely, the control 6 is adapted to control the lighting 3 of each module 10 or 1 1 so that the lighting 3 of the module 1 1 located on the back side of the document 2 illuminates the back of the document when the lighting of the module 1 1 located on the side of the front of the document 2 does not illuminate the front of the document.

The control 6 includes all the means known to those skilled in the art to allow control of the lighting 3 of the modules 10 and 11, for example a microprocessor and a memory.

Thus, the detector 5 of the module 10 (front side) can not detect an illumination of the back side, and conversely the detector 5 of the module 1 1 (back side) can not detect an illumination of the front side. Only the reflection on the document 2 of the illumination from the illumination 3 of the module 10 will be detected by the detector 5 of the module 10; and only the reflection on the Document 2 of the illumination from the illumination 3 of the module 1 1 will be detected by the detector 5 of the module 1 1.

Preferably, each module 10 or 1 1 respectively comprises a 100 or 101 optical sensor comprising a housing 1000 of elongated shape, each sensor 100 or 101 being located opposite the other sensor, by centering the housings 1000 on the axis Y. The elongate shape of the housing 1000 of the sensor 100 or 101 typically allows scanning up to a width of an A4 sheet. The housing 1000 can thus be typically of a length of the order of 25 cm, for example. The housing may have a width of about 20 mm for example.

The control 6 can be external (as shown schematically in FIGS. 2 and 3) or internal to the housing 1000.

The lighting 3 of the module 10 or 1 1 comprises a light source (not shown) located on a lateral side of the housing 1000 of the sensor. In order to diffuse the light from the source towards the front or the back of the document 2, the lighting 3 comprises a light guide 30, diffusing the light over the entire length of the module.

In Figure 2, the guides 30 of each module 10 or 1 1 are located opposite each other, and the detectors 5 are also located opposite each other.

In addition, scanner detectors require a blank reference to scan document 2.

Conventionally, the blank reference is positioned in front of the detectors 5 in the Ref position, in FIG. 2, for example by using the space freed by the partial overlap Δ of the modules.

Advantageously according to the invention, the light guide 30 of each module 10 or 1 1 is white.

As shown in Figure 3, the detector 5 of each module 10 or 1 1 is located opposite the guide 30 of the other module. In this way, the light guide 30 of each illumination 3 is able to serve as a blank reference for the detector 5 of the module 10 or 1 1 which is situated in front of it.

Preferably, the optical sensor 100 or 101 is of the CIS type. As such, the CIS sensor comprises a lighting 3 with a red color diode (hereinafter R), a green color diode (hereinafter V), and a blue diode (hereinafter B), the three diodes thus forming the light source. The R, G, B diodes can be turned on or off individually by control 6.

The diodes R, V, B are located on a lateral side of the sensor housing, and the illumination 3 thus comprises a light guide 30 for diffusing the illumination over the entire length of the sensor CIS.

The detector 5 is connected to an optical rod 4, or "rod lens" according to the terminology generally used by those skilled in the art, over the entire length of the sensor 100 or 101. It is recalled that the preferred technology is CMOS technology, which has the advantage of being readily available commercially, and therefore of having a lower cost than competing CCD technology.

FIGS. 4, 5 and 6 diagrammatically represent control chronograms of the modules according to the invention, during the scan of a line of a document 2 to be scanned. The modules include non-limiting CIS sensors.

FIG. 4 thus shows that a control method of a scanner according to the invention comprises a step in which the control 6 controls the illumination 3 of each module 10 or 1 1, so that the sensors alternately illuminate the only one side or the back of document 2 only.

Thus, the line A shows that the detectors 5 of the sensors 100 and 101 are activated by the control 6 so that they are able to detect an optical reflection successively for the illuminations with the three colors R, V and B. The detectors 5 convert the received light in electrical information. An integration time is defined in FIG. 4, line A, by the time between two integration tops, during which simultaneously each detector erases the content of the pixels and transfers the information integrated in the previous cycle to be ready for a new one. cycle. Thus, the control 6 controls the detectors 5 at time t ₀ so that they are able to detect an optical reflection for an illumination at the color R during a phase AR starting at time to.

Line C shows that the command 6 controls at time t ₀ the diode R of the sensor 1 00 corresponding to the front of the document 2 so that the diode R illuminates the front of the document for a duration τ, between t ₀ and ti. The detector 5 of the sensor 1 00 can then detect the optical reflection R on the document 2 (see line A).

After the duration τ, the command 6 controls the diode R of the sensor 1 00 so that it no longer lights up the front of the document 2.

Line B shows that the command 6 controls at time t2 the diode

R sensor 1 01 corresponding to the back of the document 2 so that the diode R illuminates the back of the document for a time τ, between t2 and t3. The detector 5 of the sensor 1 01 can then detect the optical reflection R.

After the duration τ, the command 6 controls the diode R of the sensor 1 01 so that it no longer lights up the front of the document 2.

And so on until a time ¾ '.

The control 6 controls the detectors 5 at time to 'so that they are able to detect an optical reflection for an illumination at the color V during a phase Av starting at time t ₀ '.

The lines D and E show that the control 6 controls the time to 'the diodes V of the sensor 1 00 and 101 so that the diodes V alternately illuminate the front and the back of the document, each during a slot of a duration τ, included for example between t ₀ 'and t- for the diode V of the sensor 100, and for example between t ₂ ' and t ₃ 'for the diode V of the sensor 1 01. The detectors 5 of the sensor 1 00 and the sensor 1 01 can then detect alternately the optical reflection R on the document 2.

The control 6 controls the detectors 5 at time t ₀ "so that they are able to detect an optical reflection for illumination at the color B during a phase AB starting at the time to".

The operation of the control 6 and the detectors 5 during the AB phase is the same as that of the AR and Av phases already described, and is not repeated here for the sake of clarity and brevity. As shown by the lines B and C, for example, the illumination slots of the diodes of the sensors 1 00 and 1 01 are separated by a duration T. Thus, t i and t _{2 are} separated by a duration T, of safety, to avoid any interference between the illuminations. T is of the order of a few tens of με for example.

The set of AR, AV and AB phases represents an RGB cycle of integration of a line of the document during its displacement. The duration of an RGB cycle is of the order of 1, 5 milliseconds. The scanner typically performs one cycle per line of the document to be scanned. During the phase Av, the information relating to the phase AR is transmitted to the command 6 for processing, and during the phase AB, the information relating to the phase Av is transmitted to the command 6 for processing, and so on for the whole of the cycle and on all lines of the document.

FIG. 5 schematically shows a variant according to which the illumination time by each diode is continuous during an integration time by each detector during a phase. Thus, instead of having alternating illumination slots of the sensor 1 00 or 1 01 as in FIG. 4, each diode can illuminate continuously the front or the back during each phase A _R , A _v or A _B.

The time of the continuous slot of FIG. 5 can thus correspond substantially to the sum of the elementary slots of duration τ of FIG.

The total illumination time represents between 10% and 50% of an integration time of each detector 5 during a phase. The integration time of the detector 5 during a phase is of the order of 500 με, the duration τ of each elementary slot of FIG. 4 is thus 50 με, to form a lighting time of the front or back of the order of 200 με for example.

The configuration of Figure 4 is preferred at high speeds of scrolling document 2 in the scanner. The information concerning each line and detected by the detector is thus better distributed along the displacement (up to 1 μιη during a phase A _R , A _v or A _B ). FIG. 6 shows that the control 6 controls the detector 5 of each sensor 1 00 or 1 01, so that each detector 5 of a sensor is only able to detect an optical reflection on the document when the diodes of said module illuminate the sensor. front or back of the document, the detector 5 of the other module 1 1 being disabled. This ensures that there will be even less interference between the sensors.

Thus, each AR, AV OR AB phase of FIGS. 4 and 5 is divided into two sub-phases: a first sub-phase on the one hand and a second sub-phase on the other hand. During each of the sub-phases, only the detector of the sensor illuminating the front or the back is active, the other detector of the sensor being deactivated as the illumination of the same sensor.

Thus during the first sub-phase of the AR phase, between an initial time t ₀ and a time M, only the sensor 5 of the sensor 1 00 illuminating the front is active. The detector 5 of the sensor 1 01 is deactivated, as is the illumination of the sensor 1 01.

During the second sub-phase, between the time ÎM and a time to 'of beginning of the next Av phase, only the sensor 5 of the sensor 1 01 illuminating the back is active. The detector 5 of the sensor 1 00 is deactivated, as is the illumination of the sensor 1 00.

Apart from the control of the detectors specified above, the operation of the control 6 and the diodes of FIG. 6 corresponds to the operation already described with reference to FIGS. 4 and 5, and is not repeated here for the sake of clarity and simplicity. concision.

Claims

1. Scanner for scanning the front and back of a document (2), comprising

- a module (10) located on the side of a front of the document (2), having a lighting (3) of the front of the document and an optical detector (5);

- a module (1 1) located on the side of a back of the document (2), having a lighting (3) of the back of the document and an optical detector (5);

each module (10, 1 1) is located substantially opposite the other module (10, 1 1), and

the scanner being characterized in that it comprises

- a control (6) connected to the lighting (3) and to the detector (5) of each module (10, 1 1) and able to control the lighting (3) and the detector of each module (10, 1 1 ), so that,

in the module (10) located on the side of the front of the document (2), the illumination (3) illuminates the front of the document and the detector (5) is able to detect an optical reflection on the front of the document (2) when in the module (1 1) located on the back side of the document (2), the illumination (3) does not illuminate the back of the document and the detector (5) is deactivated, and vice versa so that, in the module (1 1) located on the back side of the document (2), the illumination (3) illuminates the back of the document and the detector (5) is able to detect an optical reflection on the back of the document (2) when, in the module (10) on the front side of the document (2), the illumination (3) does not illuminate the front of the document (2) and the detector (5) is deactivated.

2. The scanner according to claim 1, wherein each module (10, 1 1) comprises an optical sensor (100, 101) comprising a housing (1000) of elongated shape, each sensor (100, 101) being located opposite the other sensor (100, 101).

3. Scanner according to claim 2, wherein each module (10, 1 1) comprises an optical detector (5) and the lighting (3) of each module (10, 1 1) comprises a guide (30) of light, the guide (30) of light being white, and wherein the detector (5) of the module (10) on the side of the front of the document (2) is located opposite the light guide (30) of the lighting (3) of the module (1 1) located on the side on the back side of the document (2), and vice versa in which the detector (5) of the module (1 1) situated on the back side of the document (2) is situated opposite the light guide (30) of the illumination (3). ) of the module (10) located on the side of the front of the document (2), so that the guide (30) of light of each lighting (3) is able to serve as a blank reference for the detector (5) of the module ( 10, 1 1) which is located in front of him.

4. Scanner according to one of claims 1 to 3, wherein each module comprises an optical sensor (100, 101) CIS type comprising a lighting (3) with a red color diode, a green color diode, and a Blue diode.

5. A method of controlling a scanner for scanning the front and back of a document (2), the scanner comprising

- a module (10) located on the side of a front of the document (2), having a lighting (3) of the front of the document (2) and an optical detector (5);

a module (1 1) located on the side of a back of the document (2) facing the other module, comprising illumination (3) of the back of the document (2) and an optical detector (5), and

a control (6) connected to the lighting (3) and to the detector (5) of each module (10, 1 1),

the method being characterized in that

the control (6) controls the illumination (3) and the detector (5) of each module (10, 1 1), so that in the module (10) located on the front side of the document (2), the illumination (3) illuminates the front of the document and the detector (5) is able to detect an optical reflection on the front of the document (2), when, in the module (1 1) located on the back side of the document (2) , the illumination (3) does not illuminate the back of the document and the detector (5) is deactivated, and vice versa so that, in the module (1 1) located on the back side of the document (2), the illumination (3) illuminates the back of the document and the detector (5) is able to detect an optical reflection on the back of the document (2), when, in the module (10) on the front side of the document (2), the illumination does not illuminate the front of the document and the detector (5) is deactivated.

6. The method of claim 5, wherein the illumination (3) of each module (10, 1 1) having a guide (30) of light, the guide (30) of light being white, and the detector (5) of each module (10, 1 1) being located opposite the light guide (30) of the other module (10, 1 1), the control (6) controls each detector (5) so that a reference of white is taken on the light guide (30) which is located opposite it.

7. Method according to one of claims 5 or 6, wherein the control (6) controls the lighting (3) of each module (10, 1 1), so that the document (2) is illuminated, on the recto or verso of the document, during a lighting time representing between 10% and 50% of an integration time of each detector (5).

The method of claim 7, wherein the illumination time is continuous or discontinuous during the integration time.