RU2475363C2 - Laser crystal-based-line printer of labels and packages - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to packing equipment, machine building and instrument making, particularly, to direct-action printers, and aims at increasing printer rate and decreasing its sizes. Proposed laser matrix printers uses the line of, at least, five laser emitters for scanning the image pattern over its height, discrete single-emitter diode lasers, and integral optical system. Data line printing is performed by burning off of label or package surface layer points of image pattern perplexing in colour or shade relative to underlayer or substrate.

EFFECT: higher security against counterfeit, decreased sizes and simplified design.

5 dwg

Description

The invention relates to equipment for packaging, machine-building, instrument-making technologies, to printers of direct action on the material. The printer is an autonomous unit and is intended for use as part of technological lines. The function of the device is to put brief information on the manufactured products. This is in demand in the production of food, beverages, pharmaceuticals to indicate the date of manufacture, in some cases - time or shift and expiration date.

The principle of operation is the burning or evaporation of the upper layer of the label or packaging with focused rays of a line of diode laser chips. For good readability of the applied text, the top layer or paint of the material of the package or label should be of a dark tone and / or of a material that absorbs infrared light, the base should be a contrast tone or color. Many manufacturers are already using such labels and packaging, others can optionally order them when developing a new packaging design. In addition to improving the appearance, this protects the product from counterfeiting.

The use of parallel methods allows you to multiply the installation power by the number of parallel working modules, which ultimately allows you to increase the speed of the device as a whole. In relation to the claimed printer, this solves another important problem - excluded the moving elements of the sweep of the beam and minimized dimensions.

The closest analogue is the device described in [1]. The work is based on the method proposed in article [2] for parallelizing data streams recorded on optical media to increase the speed of writing and reading data. Were made: a device for soldering and a printer for polymer foil, in which the print head consisted of two strips with a width of emitters of 100 microns and a pitch between emitters of 200 microns.

In [1], [2] and [3], serious problems of the electric and thermal influence of neighboring emitters on each other, if they are contained in one crystal, are highlighted.

In addition, it is impossible to obtain a uniform homogeneous strip of light due to the spread in the parameters of the emitters. The focused image of the strip has the “smile” effect, which consists in the downward deflection of the middle part.

Laser strips are designed for use in the form of strips, as well as in the form of stacked vertical arrays of strips for pumping the working fluid of solid-state lasers (DPSS Laser). Available with a number of emitters 19 ... 60 and others. With a strip width of ~ 10 mm and a length of 1 mm. The power of one emitter is only ~ 1 Watt. When comparing different technologies, the highest burning ability is characteristic for a wavelength of 808 nm.

In the experimental part of the work, strips having 60 emitters and a pulse power (QCW) of 100 W were tested.

It is almost impossible to lead and solder the wire to the emitter electrode 0.16 mm wide. To simplify the installation technology, the line of emitters was geometrically divided into groups of 5 ... 8 pieces to obtain 7 lines of the raster required for marking purposes. On top of each of 7 arrays of 5 ... 8 emitter electrodes, a common electrode with a current-carrying wire was soldered.

A simpler way was to split the strip into pieces of 5 ... 8 emitters, and then solder them onto a common base with an interval of ~ 1 mm for better electrical and thermal isolation and cooling.

Both methods did not give positive results when labeling labels. This is due to the fact that it is impossible to focus laser radiation emanating from a group of several emitters into one approximately circular point, and the power of one emitter of 1.6 watts is not enough to burn out a point that is visible to the eye without a magnifying glass on moving material.

Laser diodes in housings are a good solution to simplify installation and subsequent repair, in addition, a feedback photodiode is also integrated in them, which makes it possible to equalize the power of the array of diodes and compensate for the decrease in luminous flux by the end of its service life. However, it was not possible to use case diodes, since emitters have linear dimensions of the order of 100 μm, and the distance between them due to the cases cannot be less than 5 mm. The character raster will not work.

Using an array of laser diodes and their corresponding microlenses as in [3] is technologically and economically inefficient.

It can be stated that if you need a raster with a low power and the number of lines of image decomposition of 19 or more, you need to use laser strips in uncut form with individual control of each emitter. But in our case, with the number of lines 5 ... 8, it is advisable to use single-emitter high-power single-shell laser diode crystals (Unmounted Laser Die), Fig. 2.

CO2 laser markers have a power of 10 ... 20 watts. In the case of using solid-state lasers, the energy effect on a substance is 2-3 times higher compared to gas lasers, due to the fact that the oscillation frequency with a wavelength of 808 nm is 13 times greater than 10.6 μm and carries more energy. Therefore, the power of a solid-state laser of 10 W will be enough.

From the requirements of good readability of the text, it was determined that a raster of at least 5 lines is suitable for displaying digital data, 7 lines are quite sufficient for displaying alphanumeric information (Fig. 3).

In the inventive printer, for vertical scanning the image of the displayed symbol, it was proposed to use a ruler of 7 active elements, and horizontal - to move the item past the print head when moving along the conveyor or carousel of the labeling machine.

Chips similar in parameters to JDL-BAE-200-808-TM-8-4.0 manufactured by JENOPTIK Lasers & Material Processing were selected as laser crystals. Their parameters are as follows:

Name: High Power Single Emitter Diode Lasers (High Power Single Emitter Diode Lasers) Number of Emitters: one Emitter Width 200 nm Crystal width 0.6 mm Crystal length 4 mm Crystal thickness 0.12 mm Radiation wavelength 808 nm Optical power output 8 watts Operating modes continuous, switched (CW, Switched) Power modulation one hundred% Beam divergence along the short axis 30 deg Beam divergence along the long axis 10 deg Efficiency 1.1 W / A Threshold current 1.2 A Working current and voltage 8.5 A 1.8 V

You can also use industrial laser modules C-mount, B-mount 3 ... 5 W as donors of laser crystals. Up to 10 watts per pulse can be supplied to a 3 W crystal in continuous mode. The total power of 7 crystals will be 70 watts per pulse, and with a font height of 2 ... 5 mm this is enough to get a clearly drawn column of 7 points.

Figure 1 shows a strip of laser emitters (Laser Bar).

Figure 2 shows a laser crystal (Unmounted Die).

Figure 3 shows an example of the font executed by the claimed printer.

Figure 4 shows the main assembly — a substrate with crystals.

Figure 5 shows a line of mounted laser crystals.

The schematic arrangement of the elements of the print head is shown in Fig. 4, 5 (dimensions are indicated in millimeters).

According to the technology requirements, the substrate (1) is made of beryllium oxide (BeO) or an alloy of copper with tungsten (CuW). This provides the same temperature coefficient of expansion of the substrate and crystals. The substrate is coated with gold, the crystals also have gold electrodes.

Seven main crystals (2) are soldered to the substrate with a special solder (for example, AuSn) so that the cut of the radiating surface is on the cut of the substrate. The main seven rays have a wavelength of 808 nm and are almost invisible to the eyes, so two more low-power laser crystals (3) are mounted at the edges of the main ones, emitting red light to focus all the rays and indicate the size and boundaries of the printed line on the label.

Gold or gold-plated current-conducting wires are soldered to the upper electrodes of the crystals. They are attached to the bar (4). The wires of the main emitters are shown in blue in the figures, the auxiliary ones in red, the common ground wire in black. It is soldered to the substrate.

The substrate is mounted on a copper plate (not shown) having thermal contact with a Peltier thermoelectric element (TEC). The Peltier element is powered by a temperature controller. A radiator with a fan is attached to the “hot” side of the element, for example, for a computer processor with a dissipated thermal power of 90 ... 100 W. The Peltier element can be excluded if the printer is not intended to be used in workshops with high (about 40 ° C) ambient temperature. The operating temperature of semiconductor lasers in the range of 20 ... 25 ° C and a current value less than the nominal one increases the laser service life of 10,000 ... 50,000 hours.

Rays emanating from laser crystals have an elliptical cross section. The scattering angle is larger along the short side, the long axis of the ellipse is perpendicular to the substrate. Correction of the shape may require the use of a cylindrical lens (5).

The rays should be of elliptical section, but with a vertically arranged long axis, as shown in the figure after a cylindrical lens. Then, when an object moves past the print head for a time equal to the pulse duration, the ellipse will stretch in the horizontal direction and the final point on the object will take a round shape. The course of the rays is shown schematically for the edges and the middle.

Next, the rays are processed by a simple collimating device. The requirements for the collimator are low, since it is not necessary to focus the rays at very small points, otherwise the text will be difficult to read. It is desirable that the lenses, especially the cylindrical one (if any), be coated with an antireflective coating. The reflected rays should not fall back into the laser crystals, this can damage them.

Control system

Similar to that described in [4]. The article describes the use of a line of LEDs for text output and indicates the possibility of using laser modules with appropriate amplifiers.

Based on the information line entered from the console by the operator in the form of an alphanumeric string of text, Atmel ATtiny or ATmega single-chip controller selects bytes from the character generator stored in non-volatile memory whose individual bits correspond to points in the character column. The controller outputs control powerful high-speed switches that supply current to the lasers. The controller also generates pulses with an adjustable duration of up to 300 μs, depending on the speed of the objects and other parameters.

Pulse operation is necessary to overcome the threshold at which material is burned. The radiation power levels below the threshold do not produce useful work, but only lead to side heating of the material and laser diodes. Power above the upper threshold and pulse duration longer than the norm lead to carbonization of the label or burning through it.

The simplified algorithm of the system is as follows.

When the product moves along the conveyor or carousel and reaches the product sensor, the latter is triggered and sends a signal to the controller input.

A signal from an encoder characterizing the location of the product to be printed is supplied to another input of the controller.

When using an encoder with 1024 pulses per revolution of the shaft and a roller diameter of 50 mm, which has mechanical contact with the conveyor or carousel, 1 pulse corresponds to the movement of the object by 0.15 mm. With a letter or number width of 1.5 mm, it will be printed in 10 pulses from the encoder.

The controller counts a predetermined number of N pulses of the encoder and starts printing, for each pulse issuing one column from the character generator of the symbol. The number N corresponds to the offset from the installation location of the product sensor to the place on the product where the text should begin. It is set from the remote control by the operator in millimeters and is converted by the controller into the number of encoder pulses.

This device is relatively high-tech and non-contact. Therefore, the author applied an encoder of his own design, also a non-contact principle of action, with the function of a product sensor.

Non-Contact Laser Product Sensor / Linear Encoder

The operation of the device is based on the use of a specialized microcircuit from the family used in computer optical and laser mice.

Consider, for example, OM02 (Optical Mouse Sensor).

The microcircuit contains a video matrix with a low resolution (usually 16 × 16), 256 levels of gray color and the number of frames per second up to 2000 on the crystal. The linear resolution on each axis is <0.07 mm, maximum speed> 400 mm / s (> 24 m / min). The analysis block for moving the captured image along the X and Y coordinates calculates and gives out quadrature signals (with a phase shift of 90 °) along both axes. One of the axes (Y) in this case is not used, and according to two signals of the X axis you can always determine the characteristics:

- the presence of the product by its movements, the product appeared in the field of view - movement signals are generated, the printer starts printing, counting N (see above), this replaces the product sensor;

- the amount of movement in units of 0.1 ... 0.15 mm depends on the optics, as soon as the object moves to this step, the encoder generates a pulse front (decay), this replaces the classic encoder;

- direction of movement, if the front of phase A first appears, and then phase B appears, then this means that the object moves from left to right, and vice versa. Depending on this, the text is printed in the forward or inverse direction.

The algorithm of the device includes a learning mode.

When training the printer, the operator passes the product past the printer at low speed (turns on the low speed drive or manually). As soon as the red dots of the targeted lasers are within the tolerance limits of the text area on the object, presses the button on the remote control. In this case, the controller itself determines the number N, stores it in a memory cell. Subsequently, the printer operates automatically and autonomously.

As additional functions are provided:

- counting the number of products during the time since the start of the shift;

- reading dates from a GPS or Glonass signal;

- sending SMS with the current output and binding to the coordinates of each production line.

The printer can be made both stationary and manual.

In addition, the printer can be equipped with digital and analog inputs for connecting scales, meters, etc. and print measured information on the fly.

According to the invention, discrete single-emitter crystals of diode lasers and a single optical system are used, and a line of information is printed by burning out points of the surface layer of the label corresponding to the mark of the symbol or packaging, contrasting in tone or color to the underlying layer or base. The number of active elements in the ruler doubles, and it becomes able to print 2 lines of text in parallel. Instead of the traditional bundle “Product Sensor - Encoder”, a combined device based on a microchip similar to that used as a displacement sensor in computer mice (using an LED or laser diode) was used, replacing both the encoder and the product sensor.

List of links

1. High-power diode-laser-bars with 19 up to 48 individually addressable emitters M. Roehner, N. Boenig, K. Boucke and R. Poprawe Fraunhofer Institute of Laser Technology, Steinbachstraβe 15, 52074 Aachen, Germany.

2. D.B. Carlin, "Individually addressed arrays of diode lasers," in Diode laser arrays, B.D. and S.D.R., eds., Cambridge studies in modern optics (l4), ch. 3, Cambridge University Press, 1994. ISBN 0-521-41975-1.

3. Emitter Array with individually addressable laser diodes John Gary Sousa, Josh P. Foster, Thomas C. Dearman US Patent No: US 6348358 B1.

4. “Running line with a mechanical scan” A.P. Besplemennov, Journal of Radio, No. 2, 2009, p. 51, 52.

Claims (1)

A laser matrix printer with a direct effect on a material using a line of more than five laser emitters to scan the raster along the height of the printed symbol, characterized in that discrete single-emitter crystals of diode lasers and a single optical system are used, and a line of information is printed by burning out surface points corresponding to the character design a layer of label or package contrasting in tone or color to the underlying layer or base.

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