EP0690792B1 - Device for precisely positioning a printing head in relation to a substrate - Google Patents

Abstract

PCT No. PCT/DE94/00273 Sec. 371 Date Sep. 20, 1995 Sec. 102(e) Date Sep. 20, 1995 PCT Filed Mar. 11, 1994 PCT Pub. No. WO94/21466 PCT Pub. Date Sep. 29, 1994A recording substrate (21) is brought into a predetermined position on a recording substrate holder (10). One edge of the recording substrate (21) rests against a recording substrate stop (18) provided at one side on the recording substrate holder (10). Extending transversely to the recording substrate stop (18), in or on the recording substrate holder (10), there is a transmitting or receiving means (KS) which can be covered by the recording substrate (21). A receiving or transmitting means (KE) is provided on the printing head (7). In the region of the extent of the transmitting or recording means (KS), at a defined distance from the recording substrate stop (18), a shielding surface (30) is arranged on the recording substrate holder (10). During the movement of the printing head (7) along the transmitting or receiving means (KS), the location of the shielding surface (30) and the location of the recording substrate edge remote from the recording substrate stop (18) are detected.

Description

The invention relates to a device for the exact positioning of a print head relative to a record carrier in a printer.

In a printer, record carriers in the form of single sheets made of paper or plastic are transported in a record carrier feed shaft. The record carriers are fed from the record carrier feed shaft to a record carrier receptacle on which they are printed.

The recording medium holder contains means which bring the recording medium into a desired position on the recording medium holder. The target position can be reached, for example, when an edge of the record carrier lies against a record carrier stop provided at the edge of the record carrier holder. If the target position is defined in two dimensions, a second record carrier stop, which is provided perpendicular to the first record carrier stop at a further lateral boundary of the record carrier holder, can determine the target position of the record carrier in this second position.

If the edges of the record carrier lie against the record carrier stops, the printing process can be carried out, provided that the position of the record carrier holder relative to the print head and the format of the record carrier and the format of the record carrier are known.

Printers usually process recording media in a standard format or the format used in each case must be selected by an operator. Another way of determining the format of the recording medium is to guide a sensor that works on the light reflection principle over the recording medium holder. The different reflection properties of the record carrier and the record carrier holder are used. Unprinted recording media reflect the light far more than the surface of the recording media holder. However, problems arise with this reflection light barrier whenever a recording medium is already printed in some areas before the printing process, i.e. contains, for example, a form that is to be filled in by the current printing process, or if the recording medium is reflective of conventional recording media, for example because of a special coloring of their entire surface or their edges deviates.

The assignment of the record carrier to the printhead is done by reducing the geometric tolerances between the printhead mechanism and the record carrier. This tolerance minimization is complex and expensive.

From JP 3-197162 a device for positioning a print head on the basis of different reflection properties of a paper, a reflection rail and an end mark is known. A photo sensor and a print head are arranged together in a movable carrier.

From JP 3-142272 it is known to place a record carrier on a record carrier holder and to determine the position of the record carrier by sensors operating according to the reflection principle. The sensors are arranged together with a print head in a carrier.

An optical measuring device is known from EP 0 406 236 B1, by means of which the lateral storage of a record carrier can be determined. A transmitting and a receiving element are arranged opposite each other on a displaceable carrier in such a way that a recording medium introduced into their beam path is recognized.

An arrangement for determining the position of a printed sheet is known from IBM Technical Disclosure Bulletin, Vol. 28, No 4, September 1985. The arrangement works according to the transmission principle, with an LED being provided as the transmission means and a series of phototransistors as the reception means. The printed sheet is guided between the sending and receiving means and the position is determined by scanning the phototransistors. The distance between the individual phototransistors is limited by the size of the components to a minimum distance and therefore the position of the printing sheet can only be determined with a relatively coarse resolution.

It is an object of the present invention to provide a device for the exact positioning of a print head relative to a record carrier in a printer, which enables the position of the print head and the printable area of the record carrier to be matched exactly with one another, so that the printed characters are highly reliable are mapped to the desired positions.

This object is achieved by the features specified in claim 1. Advantageous refinements and developments of the invention are specified in the subclaims.

The distance from an edge of the recording medium opposite the recording medium stop to the recording medium stop and thus the format of the recording medium is determined not according to the reflection principle but according to the transmission principle. This improves the reliability of the format recognition. The immediate assignment of the Receiving or sending means to the printhead enables the printhead to be positioned within narrow tolerance limits.

According to a development and refinement of the invention, the recording medium receptacle has a shielding surface which is arranged at a defined distance from the recording medium stop and in the region of the extent of the transmission or reception means and is suitable for communication between the reception or transmission means and the transmission or To prevent receiving media. Starting from a rest position, the print head is guided across the recording medium holder transversely to the recording medium stop. In the course of this movement, the transmitting and receiving means assigned to the printhead and the recording medium communicate with one another. For example, one side emits light, while the other side receives this light. A change in the light intensity is detected by the receiving means and communicated to a control unit.

Starting from the rest position, the print head and thus also its transmitting or receiving means reach the area of influence of the shielding surface. At the transition from the shielding surface to the unshielded part of the recording medium holder, a message is given to the control unit accordingly. Since the distance between the recording medium stop and the shielding surface is now known, conclusions can be drawn about the mutual position of the printhead for recording medium recording. In the course of the movement of the print head, the control unit accordingly knows both the exact position of the edge of the recording medium resting on the recording medium stop and the edge of the recording medium opposite the recording medium stop in its exact position. The control unit is therefore able to guide the print head with high reliability to precisely the positions at which characters or the like are to be printed.

According to a further development and refinement of the invention, the transmitting or receiving means assigned to the recording medium receptacle is arranged under the recording medium receptacle. The recording medium receptacle is formed by a flat plate which is transparent to the radiation emanating from the transmitting means, at least in the area of the extension of the transmitting or receiving means. As a result, no openings or depressions need to be made in the recording medium receptacle, which can accommodate the transmitting or receiving means. In the case of a flat plate which has no openings or depressions, deposits of recording medium residues cannot occur in the openings or depressions. Rather, a self-cleaning effect occurs due to the recording media moving over the flat plate. This improves the functional reliability of the device.

According to a further development and refinement of the invention, a guiding means is provided between the recording medium receptacle and the transmitting or receiving means assigned to the recording medium receptacle. This guide means enables the arrangement of the transmitting or receiving means at a distance from the recording medium receptacle and also causes a restriction of the cross section of the beam path between the transmitting and receiving means. The rays of the transmitting means can thus be directed exactly at the receiving means. Particularly good conductivity properties are achieved by integrally connecting the light guide with the recording medium receptacle. The exact alignment of the radiation is also optimized.

According to a further development and refinement, a plurality of light-emitting diodes are assigned to the recording medium receptacle as transmission means, which are lined up as an LED line and arranged on a flat module. The arrangement on the printed circuit board enables cost-effective production through automatic assembly. An orientation of the individual Light-emitting diodes in the direction of the light-guiding means need only be carried out within wide tolerance limits. These tolerance limits can be met without post-processing in the automatic assembly. A light-emitting diode has a radiation angle of ± 20 °, while the light guide only covers a radiation range of ± 10 ° of the light-emitting diodes and forwards them to the surface of the recording medium holder. The light guide shaft therefore ensures that the LED does not impair its function if the LED is inclined by ± 10 °.

By arranging the light-emitting diodes at such a distance from one another that the radiation cones of adjacent light-emitting diodes partially overlap on the surface of the recording medium receptacle, on the one hand a uniform light intensity is achieved on the surface of the recording medium receptacle and on the other hand the failure of a single light-emitting diode can occur due to the immediately adjacent functional ones LEDs are compensated.

Figur 1

eine Aufzeichnungsträgeraufnahmeebene mit Druckkopfschlitten in Draufsicht,

Figur 2

eine schematische, perspektivische Darstellung einer Vorrichtung zur exakten Positionierung eines Druckkopfs zu einem Aufzeichnungsträger,

Figur 3

eine schematische Darstellung der Vorrichtung zur exakten Positionierung eines Druckkopfs zu einem Aufzeichnungsträger in Frontansicht, und

Figur 4

ein Blockschaltbild einer Ansteuerung des Druckkopfs.

Figur 5

eine Seitenansicht der Aufzeichnungsträgeraufnahmeebene mit schematischer Darstellung einer Vorrichtung zum Erkennen des Vorhandenseins des Aufzeichnungsträgers.

An example of the invention is explained below with reference to the drawing. Show

Figure 1

a recording medium receiving plane with print head carriage in plan view,

Figure 2

1 shows a schematic, perspective illustration of a device for the exact positioning of a print head relative to a recording medium,

Figure 3

a schematic representation of the device for exact positioning of a print head to a record carrier in front view, and

Figure 4

a block diagram of a control of the print head.

Figure 5

a side view of the recording medium receiving plane with a schematic representation of a device for detecting the presence of the recording medium.

Figure 1 shows a receipt 10 of a receipt printer in plan view. The document receptacle 10 is formed by a flat plate. The document holder 10 consists of a crystal-clear thermoset (Makrolon). The rectangular plate has on two sides at right angles to each other and at right angles to the document receiving plane 10 projecting stops 17, 18 over the plate.

A document 21 (see FIG. 3) transported along a document feed shaft 15 in a document feed direction 14 to the document receptacle 10 is positioned at the rear document stop 17, runs at right angles to the document feed direction 14 and aligned on the lateral document stop 18, which runs parallel to the document feed direction 14, by an alignment unit, not shown. The aligned document 21 can be printed with the aid of a print head 7 (see FIG. 3) that can be moved in a direction X and a direction Y and carried by a carriage 9. The carriage 9 contains a heat sink 8 on its upper side, which dissipates the power loss of the dot-matrix print head 7.

Among the flat plate of the specimen holder 10 are three transmitting LED (L ight E mitting D iodines) arranged 3 1, 2,. A first transmission LED 1 is located close to the lateral document stop 18. A second transmitting LED 2 is arranged at a distance from both the rear document stop 17 and the lateral document stop 18. A third transmission LED 3 is arranged near the rear document stop 17. A document 21 fed to the document receptacle 10 in the document feed direction 14 initially covers the second transmission LED 2, whereupon the aligning device detects the document 21 and pushes it to the rear and to the side document stop 17, 18 until the first Send LED 1 and the third send LED 3 are covered by document 21.

As shown in FIG. 5, each transmit LED 1, 2, 3 interacts with a receive LED 4, 5, 6. The first transmit LED 1 is assigned the first receive LED 6, the second transmit LED 2 the second receive LED 5 and the third transmit LED 3 the third receive LED 4.

The arrangement and functioning of the paired transmit and receive LEDs 1, 2, 3, 4, 5, 6 will now be explained using the example of the first transmit LED 1 and the first receive LED 6. The first transmission LED 1 is fastened on a plastic molded part 22 in a defined position. The plastic molded part 22 has two hook-shaped ends which protrude laterally from the first transmission LED 1. These ends can be locked in on the underside of the flat plate of the document receptacle 10 locking hooks 23, 24. In the locked state, the line of symmetry of the first transmitting LED 1, which is identical to the axis of the main emission direction 25 of this transmitting LED 1, is at an angle α to the document receiving plane 10. Above the flat plate of the document receiving 10 is the first receiving LED 6 arranged. The first receive LED 6, like the first transmit LED 1, is fixed on a molded plastic part 22. This plastic molded part 22 can be positively locked in a document receiving cover 11 in a defined position. In the locked state, the line of symmetry of the first receive LED 6, which is identical to the axis of the main receive direction 26 of the receive LED 6, is at an angle β to the flat plate of the document receptacle 10. The inclined position of the transmit and receive LEDs 1- 6 causes, as explained in more detail below, an increased reflection on the document 21 and a virtual thickening of the document 21.

When the radiation generated by the first transmitter LED 1 passes through the flat plate, a refraction occurs which defines the axis of the main emission direction 25 from the angle α breaks the angle β. The axes of the main receiving direction and the main emission direction are then aligned in the area above the flat plate of the document holder 10. The angle α is, for example, 64 degrees and the angle β is 45 degrees. The distance between the lower edge of the first reception LED 6 and the surface of the document receptacle 10 must be at least as large as the maximum thickness of the documents 21 to be processed.

The other reception LEDs 4, 5 are also fixed in the document receiving cover 11. Together with the document receiving cover 11, these can be pivoted away from the surface of the document holder 10 in the pivoting direction 13 about an axis of rotation 12 running parallel to the rear document stop 17. In the pivoted-down state of the document receiving cover 11, the document holder 10 can be cleaned or damaged documents can be removed. When the document receiving cover 11 is pivoted back into the desired position, its end opposite the axis of rotation 12 engages in a latching part 27 protruding from the document feed shaft 15. For this purpose, the document receiving cover 11 has a tab 16 in the area mentioned, in the opening 28 of which a nose 29 of the latching part 27 penetrates.

After completion of the alignment process, the document 21 has reached its target position on the document holder 10. To print the document, the print head 7 can be guided in a direction X and a direction Y by means of a slide drive AN (see FIG. 4) over the document holder 10. The direction Y coincides with the document feed direction 14, while the direction X is perpendicular to these two directions 14, Y. In order to ensure exact printing of the document 21 at the locations provided for this purpose, a device for the exact positioning of the print head 7 is provided. This device is able to recognize different formats of documents 21 and the position of the document receptacle 10 relative to the print head 7.

The ability to recognize the geometric position of the document receptacle 10 relative to the print head 7 is advantageous in so far as complicated adjustment of the printhead 7 for receiving the document 10 can be dispensed with. The geometric position of the document receptacle 10 relative to the print head 7 must therefore be known because two mutually perpendicular edges of the document 21 rest against the lateral or rear document stop 17, 18 and the position of the document 21 relative to the print head 7 thus depends on the position of the document receptacle 10 .

Since documents 21 of different widths and thus of different formats are to be printed on without having to preselect a format, the start of document 21 in the X direction is recorded. In the X direction, the document 21 begins at the detected point and ends at the lateral document stop 18. The dimension of the document 21 in the Y direction is predetermined in this example and therefore does not need to be recorded in this exemplary embodiment. A detection of this document dimension would also be detectable with another device of the type described below.

As shown in FIG. 2, the document receptacle 10 contains, in addition to the document stops 17, 18 protruding upward above the plate, a light shaft 19 which is made in one piece with the flat plate of the document receptacle 10 and which is made in a rectangular body. The rectangular body consequently exists just like the document receptacle 10 made of translucent Makrolon. The rectangular body extends in the direction X on the underside of the flat plate in the area of the rear slip stop 17. The light shaft 19 is located inside this rectangular body.

The light shaft 19 is a longitudinal groove which extends from the long side of the rectangular body facing away from the flat plate of the document receptacle 10 in the direction of the flat plate. The longitudinal groove has a trapezoidal shaft cross section, which tapers in the direction of the flat plate of the document holder 10. The groove base 32 lying in the area of the flat plate runs parallel to the longitudinal direction flat plate. The groove bottom 32, however, inclines in a direction perpendicular to the longitudinal direction, so that the first trapezoidal leg, as seen from the paper feed direction 14, is longer than the second trapezoidal leg of the light well 19. The groove bottom 32 is thus directed obliquely to the flat plate of the document receptacle 10. Light guided in the light shaft 19 and directed towards the flat plate is refracted by an angle λ through the prism formed by the groove bottom 32 in cooperation with the flat plate. this angle λ is 26 °. The surfaces of the light well and the flat plate are polished to optimize light conduction and refraction.

The light guided in the light shaft 19 is generated with the aid of an LED line KS. The individual LEDs KS1 ... 13 of the LED line KS are arranged on a flat module 33 which extends parallel to the document receptacle 10. The light emitted by this LED line KS is guided in the light shaft 19 to the surface of the document receptacle 10 and detected there by a light-sensitive receiving diode KE. In the area in which a document 21 lies on the document receptacle 10, light is prevented from escaping at the concealed locations of the document receptacle 10 and thus communication between the LED line KS and the receiving diode KE is prevented.

Such a light emission is prevented at another point. In the area of the side of the document receptacle 10 opposite the lateral document stop 18, the surface of the flat plate in the mouth region of the light well 19 is blackened, for example by applying paint. The distance between the mutually facing edges of this blackening 30 and the lateral document stop 18 is fixed by a fixed dimension, so that the position of the lateral document stop 18 is also known if the position of the blackening 30 is known.

As can be seen from FIG. 3, the receiving diode KE is assigned to the movable carriage of the print head 7. The receiving diode KE is fastened in a diode carrier 34. The diode carrier 34 completely surrounds the receiving diode KE and has a slit diaphragm 20 through which light coming from the LED line KS can penetrate to the receiving diode KE. The distance between the slit diaphragm 20, which is approximately 0.5 mm wide, from the print head 7 is determined by a precisely fitting fastening of the diode carrier 34 to the carriage 9. The diode carrier 34 is attached to the carriage 9 by means of dowel pins 31 and a screw connection, not shown. An exact assignment of the print head 7 to the receiving diode KE can also take place in that the diode carrier 34 is also used as a carrier for the print head 7.

FIG. 3 also shows a section of the diode row KS. The individual LEDs KS1..6..13 are arranged next to each other at a uniform distance (7.62 mm), for example by automatic assembly. Each of the LEDs KS1 ... K13 emits light in a vertical direction from the flat module 33 upwards into the light shaft 19. The radiation angle γ is approximately ± 20 °. The distance between the LEDs KS1..6..13 and from the LEDs to the surface of the document holder 10 is selected such that the light cones of adjacent LEDs KS1..6..13 on the surface of the document holder 10 overlap by half. The relevant beam angle δ for this light cone coverage is ± 8 °. This type of arrangement of the LEDs KS1..6..13 results in a uniform irradiance at the receiving diode KE, which is essential for reliable function.

The light shaft 19 only detects a section of ± 10 ° of the light cone emitted by the LEDs KS1..6..13 of ± 20 °. This means that the installation angles of the KS1..6..13 LEDs are insignificant for the function of the device when fitted up to ± 10 °. By covering the light cones of adjacent LEDs KS1..6..13, the failure of individual LEDs KS1..6..13 can be compensated if the immediately adjacent ones LEDs KS1..6..13 of the failed LEDs KS1..6..13 are intact.

Figure 4 shows a block diagram of a control of the print head. A control unit ST controls the motorized carriage drive AN, which moves the print head 7. The carriage drive AN reports the current position data of the print head 7 to the control unit ST. The control unit ST is connected to the receiving diode KE and the LED line KS. The reception diode KE gives a pulse to the control unit ST when a strong light / dark change occurs, for example when the blackening 30 passes. The control unit ST is therefore able to exactly detect the position of the blackening 30 and the position of the side of the document 21 facing away from the lateral document stop 18.

After a document 21 is placed on the document holder 10 and aligned with the document stops 17, 18, the control unit ST activates the motorized slide drive AN. At the time of activation, the carriage 9 is in a basic position. This basic position can be seen in FIG. 1. In this basic position, the receiving diode KE and the print head 7 are not above the document receptacle 10. The carriage 9 is first moved in the direction X along the rear document stop 17 via the light exit area of the light shaft 19. The distance between the light exit surface of the light shaft 19 (and thus approximately the distance between the surface of the document receptacle 10) and the receiving diode KE is approximately 3 mm.

First, the receiving diode KE moves over the blackening 30. During the transition from the blackening 30 to the polished light exit area of the light shaft 19, a strong change in light intensity occurs. The receiving diode KE transmits a corresponding signal to the control unit ST. At the time of this signal, the print head 7 is in a normalization position with respect to the document holder 10. The distance between the print head 7 and the lateral document stop 18, and thus the distance between the print head 7 and the document edge resting on the lateral document stop 18, is thus known. The mechanical and optical parameters of the structure result in a maximum theoretical measurement error for the covering edge of 0.2 mm.

The receiving diode KE is moved further in the X direction. The receiving diode KE receives the light which has been refracted in its main receiving direction. The wrap angle λ is 26 ° with respect to an axis perpendicular to the document holder 10.

die virtuelle Belegdicke 0,1113 mm. Eine Verdickung des Belegs 21 führt zu einer verringerten Durchlässigkeit des Belegs 21 für die von der LED-Zeile KS emmitierte Strahlung. Bei Belegen 21 mit faseriger Struktur wird der Effekt der virtuellen Verdickung des Belegs 21 verstärkt, weil sich eine erhöhte Anzahl von Fasern im Strahlengang befindet.Due to the wrap of the transmitted light at the wrap angle λ to the document receiving plane, the emitted radiation strikes the document 21 at an oblique angle. In the case of a film-like document 21, this causes an increased radiation reflection compared to a perpendicular incident of the radiation. Even with a relatively radiolucent document 21, such as thin paper, due to the wrap angle λ, a smaller proportion of radiation reaches the receiving diode KE. In addition, the path of radiation through the documentary material is extended. The document 21 is virtually thicker. For example, if the document thickness is 0.1 mm and the wrap angle λ is 26 degrees for document receipt 10, then according to the relationship $$\text{Document thickness ·}\frac{\text{1}}{\text{sinλ}}\text{= virtual document thickness}$$

the virtual document thickness 0.1113 mm. A thickening of the document 21 leads to a reduced permeability of the document 21 for the radiation emitted by the LED line KS. In the case of documents 21 with a fibrous structure, the effect of the virtual thickening of the document 21 is increased because there is an increased number of fibers in the beam path.

When the receiving diode KE reaches the edge of the document facing away from the lateral document stop 18, a strong light / dark change occurs at the receiving diode KE, just as it passes through the blackening 30. The receiving diode KE in turn reports this to the control unit ST, as a result of which the format and the start of the document 21 become known. As a result, the document 21 can be printed with high accuracy at the locations provided for this purpose.

Reference list

1,2,3

= Transmit LED

4,5,6

= Receive LED

7

= Printhead

8th

= Heat sink

9

= Sledge

10th

= Receipt of document

11

= Receipt coverage

12th

= Axis of rotation

13

= Swivel direction

14

= Document feed direction

15

= Document feeder shaft

16

= Tab

17th

= rear document stop

18th

= document slip on the side

19th

= Light well

20th

= Slit diaphragm

21

= Receipt

22

= Molded part

23, 24

= Locking hook

25th

= Main emission direction

26

= Main reception direction

27

= Locking part

28

= Recess

29

= Nose

30th

= Blackening

31

= Dowel pins

32

= Groove bottom / refractive agent

33

= Printed circuit board

34

= Diode carrier

AT

= Slide drive

KE

= Receiving diode

KS

= LED line

KS1 ... 13

= LED

ST

= Control unit

X, Y

= Direction of movement of the print head carriage

α

= Send LED angle

β

= Receive LED angle

δ

= relevant beam angle

γ

= Beam angle

λ

= Wrap angle

Claims (11)

1. Device for the exact positioning of a printing head (7) in relation to a recording substrate (21) in a printer,

   - the recording substrate (21) being able to be deposited on a recording substrate holder (10) and being able to be aligned on at least one recording substrate stop (18) bounding the recording substrate holder (10) on one side,

   - the printing head (7) being able to be moved in at least one direction (X) transverse to the recording substrate stop (18) over the recording substrate holder (10),

   - at least one receiving or transmitting means (KE) which can be moved together with the printing head (7) being coupled in a defined position with the printing head (7),

   - at least one transmitting or receiving means (KS) which extends in the movement direction (X) of the printing head (7) being arranged in or on the recording substrate holder (10) in such a way that the transmitting or receiving means (KS) can be covered over at least partially by the recording substrate (21), as a result of which a communication between the receiving or transmitting means (KE) and the transmitting or receiving means (KS) may be interrupted in the deposit region of the recording substrate (21).
2. Device according to Claim 1, in which the recording substrate holder (10) has a shielding surface (13) which is arranged at a defined distance from the recording substrate stop (18) and in the region of the extent of the transmitting or recording means (KS), and which is suitable for interrupting communication between the receiving or transmitting means (KE) and the transmitting or receiving means (KS).
3. Device according to one of Claims 1 or 2, in which

   - the transmitting or receiving means (KS) assigned to the recording substrate holder (10) is arranged underneath the recording substrate holder (10), and

   - the recording substrate holder (10) is formed by a flat plate which is transparent, at least in the region of the extent of the transmitting or receiving means (KS).
4. Device according to one of Claims 1 to 3, in which the transmitting means (KS) assigned to the recording substrate holder (10) comprises a plurality of light-emitting diodes (KS1..13) which are lined up as an LED row and are arranged on a flat subassembly (33).
5. Device according to Claim 4, in which, between the recording substrate holder (10) and the LED row (KS), a light conducting means (19) is provided.
6. Device according to Claim 5, in which the light conducting means (19) is formed by a shaft which is connected in one piece to the recording substrate holder (10).
7. Device according to Claim 6, in which the light-emitting diodes (KS1..13) are arranged at such a distance from one another that the radiation cones of adjacent light-emitting diodes (KS1..13) partially overlap at the surface of the recording substrate holder (10).
8. Device according to one of the preceding claims, in which the receiving or transmitting means (KE) which can be moved together with the printing head (7) is assigned a slit diaphragm (20).
9. Device according to one of the preceding claims, in which, in the region of the surface of the recording substrate holder (10), there is provided a refraction means (23) which deflects the beam path between receiving and transmitting means (KE, KS) by an angle (λ).
10. Device according to one of Claims 3 to 9, in which, to align the recording substrate (21), at least one further transmitting means (1,2,3) and one further receiving means (4,5,6) are provided, the further transmitting means (1,2,3) being arranged on one side of a recording substrate holder (10) and the further receiving means (4,5,6) being arranged on the other side of the recording substrate holder (10) in such a way that the main reception direction of the receiving means (4,5,6) is located in the region of influence of a main emission direction of the transmitting means (1,2,3), and the recording substrate (21) can be brought between the transmitting means (1,2,3) and the receiving means (4,5,6), the axis of the main emission direction of the transmitting means (1,2,3) being at an oblique angle (α) to the recording substrate holder (10).
11. Device according to Claim 10, in which

    - the transmitting means (1,2,3) is fastened below the recording substrate holder (10) to the flat plate,

    - the receiving means (4,5,6) is fastened in a cover (11) over the recording substrate holder (10), and

    - the cover (11) can be pivoted about a pivot (12) into a locking position in which the axes of the main emission direction of the transmitting means (1,2,3) and of the main reception direction of the receiving means (4,5,6) align.

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