FR2672712A1 - LASER LIGHT ALTERNATIVE DEFLECTOR FOR BAR CODES READER. - Google Patents

Abstract

The Reciprocating Laser Light Deflector for a barcode reader comprises in combination a flexible blade (16) made of a material which exhibits piezoelectric properties and which is provided with at least one specular surface (17), blade (16). ) which is made to vibrate alternately by an electricity generator (14) connected to the blade, and a laser generator (1), so that the blade (16) struck by the light ray on the specular surface ( 17), causes the continuous reflection of the light ray in varying directions, so as to produce a coherent scanning line of light on a reading surface (18) on which the information to be read in the form of bar codes is recorded.

Description

The present invention relates to an alternative laser light deflector

  for barcode readers, during the operation of which a ray of coherent light emitted by a laser generator repeatedly explores, along a line, the surface against which it is projected, surface which carries

  information to be read in the form of bar codes.

  At present, bar code readers emit a laser beam which scans in an alternating and repetitive scan, a reading surface on which the information is recorded and read by reflection on an optical receiver of the laser beam, which beam is reflected when it hits a light surface, and which is absorbed when it hits a dark surface, such as a black line with a sharp outline,

  as in the case of barcode lines.

  In these readers, the alternative scanning of the laser beam on the reading screen o the information to be

  read are recorded is obtained by two methods.

  The first method is to use a small motor whose output shaft, which carries a mirror,

  describes an arc in a reciprocating motion.

  The laser beam projected on the mirror, when the latter moves angularly, is continuously reflected in variable directions, that is to say that it describes on a reading screen, a continuous line in one direction, then in the opposite direction, when the swivel movement

of the mirror is reversed.

  The second method consists in using a small motor whose output shaft rotates according to a

  uniform rotational movement, and rotates a parallel

  the elepiped with polygonal faces and contoured surfaces

  speculars against which the ray emitted by the general

  the laser generator is projected The laser generator and the small

  motor are reciprocally placed one relative

  port to another, so that during the rotation of the parallelepiped, the specular surface struck by the laser beam, with its rotation, causes the variation of the direction of reflection, so that the reflected ray moves on the reading screen by describing a continuous line Then, by changing the surface of the polygon struck by the laser beam, the variation in direction is repeated, to again obtain the displacement of the point of incidence of the light beam on the reading screen along the same line.10 These methods have the disadvantage of requiring the use of small electric motors which are very expensive, fragile and often faulty, which does not contribute to reliable operation over time of the readers of associated bar codes In addition, according to the first method mentioned above, it is necessary to associate with the motor a device for ensuring the reversal of the movement of the motor, and according to the second method mentioned above e must be associated to the motor a small parallelepiped with surfaces to specular contours for reflection of the laser beam to varying directions, which increases the cost of

barcode readers.

  The object of the invention is to design an alternative deflector of laser light capable of eliminating the drawbacks of deflectors currently known,

  such as those described above.

  To this end, the invention provides an alternative deflector of laser light of the aforementioned type, and which is characterized in that it consists of the combination

  of a flexible blade made of a material which has

  piezoelectric properties, the blade comprising at least in one of its parts a specular surface, and is vibrated alternately by an electric generator to which it is connected, and a laser generator, such as the struck blade by the light ray on its specular surface, causes the continuous reflection of the 3 ray in variable directions, producing on the reading surface a line of coherent light scanning. According to one embodiment of the invention, the deflector is provided with two electrically conductive armatures, between which is placed the flexible blade having piezoelectric properties, these

  armatures being connected to the electric generator of ma-

  deny to apply an electrical potential not

  constant and of variable polarity over time.

  According to another embodiment of the invention, the deflector comprises at least one blade

  flexible in a material having piezoelectric properties

  triques, and covering two of its opposite surfaces

  two coatings of electrically conductive material

  tor, connected to the electric generator which delivers a

variable voltage across its terminals.

  According to yet another embodiment of the invention, the deflector comprises a flexible blade made of a material having piezoelectric properties, and carrying a specular surface or an element with a specular surface of flat or machined structure so as to reflect the light ray conveyed by the laser generator. Finally, according to a last embodiment of the invention, the deflector comprises several blades made of a material having piezoelectric properties with parallel surfaces coated with a conductive material, surfaces connected together in a parallel manner, and a flexible blade carrying the specular surface which receives the vibratory movement transmitted by the blades

placed next to it.

  According to an important advantage of the invention, the alternative laser light deflector is devoid of cogs, and it does not use miniaturized motors which

  are expensive and unreliable to operate.

  According to another advantage of the invention, the

  deflector is of simple construction, has a function-

  reliable and the barcode reader with which it is associated has in particular the advantages according to dimensions which can be reduced, simple construction and of reduced cost, less brittleness, increased operational safety,

  and a reading frequency, and therefore a frequency

  of the alternating movement of the projected laser beam

  on the reading surface where the bar code is re-

  product, which can be changed in any way

lesson.

  Other advantages, characteristics and

  tails of the Invention will become apparent from the Description ex-

  plicative which will follow made with reference to the Drawings

  attached, given only by way of example and in the-

which:

  Figure 1 shows in schematic form a general

  laser generator, deflector group and screen or

  reading face of a bar code,

  FIG. 2 schematically represents the invention comprising

  taking an electric accumulator, an alternating current generator, a deflector group, a generator

  laser, a laser power supply, as well as the various

  annuities electrical connections, and Figure 3 is a plan view of the deflector group

  with a flexible central blade carrying a special plate

  ring and two blades with piezoelectric properties

triques.

  In the Drawings, the following elements have been referenced a laser generator 1, a power supply

  2 of the laser generator 1, a support 3 which

  holds the laser generator 1 and its power supply 2, the support 3 supporting electrical terminals 4, 5, 6 and 7 to ensure the electrical connections of the generator

  laser 1, its power supply 2 and the electric accumulator

  plate 10 which supplies a bar code reader which is associated with the deflector The other following elements are also referenced: the terminals 8 and 9 of the accumulator 10, a generator 14 which produces a non-constant electrical signal which is applied to armatures of the deflector, a flexible blade 16 made of a material which has piezoelectric properties, a specular coating 17 adapted to reflect the coherent ray of light emitted by the laser generator 1, a screen 18 or

  surface on which the information to be read is recorded

  Finally, two terminals 19 and 20 are provided which are adapted to hold the laser generator 1 in place,

and a negative terminal 21.

  The alternative deflector consists of the

  two electrically conductive fittings, between them

  which is the flexible blade placed in a material having piezoelectric properties The blade is connected to the

  electric generator 14 which delivers an electrical potential

  not constant at its terminals and of polarity variable over time A potential difference, such as a

  sinusoidal, square, sawtooth or ana-

  logue, is applied in such a way as to produce stresses

  non-constant mechanical conditions on the flexible blade 16, so that it flexes in a variable manner in its

  free part not located between the terminals (not shown

  tees in Figures 1 and 2) which support the deflector group. The deflector group may include one or more

  several blades 16 having piezoelectric properties

  triques, each carrying on two opposite faces, coatings made of an electrically conductive material, which are connected to the electric generator 14 which delivers a non-constant voltage across its terminals These coatings or conductive strips which can partially or entirely coat each strip 16 which , following a request

  electric, vibrates mechanically according to a movement which is due either to its mechanical characteristics, its dimensions

  sions, its weight and its thickness, that is to say the shape, the intensity and the frequency of the applied electrical signal ap-5.

  The movement of a small mirror 17 or of the equivalent specular surface on the blade 16 or on the frame 15 which covers it on one of its lateral surfaces, can therefore be finely adjusted in frequency and amplitude, so that the laser beam emitted by the generator 1 is reflected on the reading screen 18, this ray here describing a line in an alternating rectilinear movement to allow repeated reading

  information recorded in the form of a 15 bar code.

  For this, the laser generator 1, the deflector group 15, 16 and 17, the reading surface 18, and a photo-sensitive receiver of the reader (not shown in the Drawings) will be arranged between them so that, in mode reception, we can apply a cadence

  light pulses of desired length and frequency

  rees. In the example illustrated in Figure 2, the

  negative terminal 8 of the electric accumulator 10 is re-

  linked to ground, while its positive terminal 9 is connected to an on / off switch 11 of the reader The output terminal of this switch 11 is connected, on one side, to the positive terminal 12 of the electric generator 14 at the terminals of which a variable voltage difference is delivered which is applied between the two armatures 15 and, on the other side, to terminal 4 of the support 3 which is connected to the positive terminal of the power supply 2 The positive output terminal 6 of the support 3 is connected to the positive input terminal 7 of the laser generator 1 When the switch 11 is closed, the generator 14 supplies the armatures 15,

  which causes the blade 16 to vibrate.

  7 The power supply 2 controls the laser generator 1 which emits

  a ray of coherent light directly on the small mirror 17 or on the equivalent specular surface with a plane or machined structure depending on the reflection effects which one wishes to obtain, in particular for an ef-

  correction of the scanning speed of the ray la-

  be on screen 18 and, for the reflected ray, to correct

  tion of the duration of the light pulses reflected on the photo-sensitive receiver not shown in the

Drawings.

  The alternative deflector group, object of the invention, can be practically produced in several ways, knowing that the mechanical reaction of a material which has piezoelectric properties is used,

  that two of its parallel surfaces are under stress

  electric quote, following which its surfaces

  fall to cause reflection of the light ray

who hits them.

  According to an advantageous embodiment of the invention, as shown in FIG. 3, o a flexible and elastic blade 30, of any material, comprises a specular planar coating 31 with two strips 22 and 23 of a material having properties

  piezoelectric, and surfaces 24 and 25 in one material

  electrically conductive line deposited or adhering to the parallel surfaces of the strips 22 and 23 Two supports 26

  and 27, preferably made of an insulating material, with a plug

  lon 28 insulator which clamps the blade 30 between the strips 22 and 23 towards one end thereof Terminals 32 and 33 are connected to the conductive surfaces 24 and 25 between which a potential difference is applied

  variable, in particular a sinusoidal potential

  capable of causing uniform bending of the blades 22 and 23 which is transmitted to the blade 30 without causing

  sudden variations and stresses in the material.

  The two strips 22 and 23 each have lateral surfaces

  lines coated with a conductive layer 24 and 25, acting

  as the armatures of a capacitor, are placed between them and are clamped only at one end by the supports 26 and 27, while the remaining part of a more or less large part of the elastic strip 30, in

  charging and discharging, transmits the stresses

  electrical connections to bands 22 and 23 which are free to oscillate. A small mirror 31 is placed on the blade 30, a mirror which is subjected to vibrations, to cause the variation of the direction of reflection of the laser beam which is projected onto the mirror by the laser generator 1 Le

  reflected ray moves on the following reading surface

  vant a line traversed in an alternating movement allowing the repeated reading of the information on this surface, which are represented in the form of a bar code.

  The small mirror 17, 31 or a specu-

  equivalent area, is additionally dimensioned so that the coherent ray of light has a sufficient amplitude, to obtain the scanning of the entire length of the surface 18 on which the bar code is reported, so that the variations of tangential speed of the point of reflection on the small mirror 17 can be compensated at the T level of a program which

  controls the reading of the reflected pulses.

  Of course, the deflector group is not limited to the embodiment shown in Figure 3, but it includes equivalent technical means

  consisting in providing a specular surface on a flexible element which is made to vibrate using materials

  materials having piezoelectric properties, by applying to the surfaces the same non-constant potential difference so that the beam of laser light, projected on the specular surface, is reflected according to

  variable directions, repeatedly describing

  tive a line on a reading surface, so that it can generate a succession of reflected light pulses to detect the presence of dark lines

  of the bar code which absorb the incident ray.

Claims (6)

  1 Alternative light deflector for reading   barcode scanner in which, during operation   operation, the ray of coherent light emitted by a giant   laser nerator repetitively explores a line of the surface between which it is projected and which carries information to be read in the form of bar codes, characterized by the combination of a flexible blade made of a material which has piezo properties -electric, the blade comprising at least in one of its parts a specular surface, and is vibrated alternately by an electric generator to which it is connected, and a laser generator, such as the blade struck by the light ray on its specular surface, causes   the continuous reflection of the ray in directions will   riable, producing a line of light scanning   consistent on the reading surface.   2 Deflector according to Claim 1, charac-   terized in that it is combined with a laser generator (1), provided with two electrically conductive armatures (15), between which is placed a flexible blade (16) made of a material having piezoelectric properties, these armatures being connected to the electric generator (14) which delivers a non-constant electric potential to the   armatures and polarity variable over time.   3 Deflector according to Claim 1, charac-   terized in that it comprises at least one elastic blade   (16) of a material having piezoelectric properties   triques, covering on opposite surfaces   elements made of an electrically conductive material, connected to the electric generator (14) which delivers at its terminals a non-constant voltage.   4 Deflector according to Claim 1, charac-   terized in that it comprises an elastic blade (16) made of a material having piezoelectric properties, and carrying a specular surface or element (17) having there such a surface with a planar or machined structure   adapted to reflect the light ray conveyed by the laser generator (1) and which strikes this surface or element (17). 5 5 Deflector according to Claim 1, charac-   terized in that it comprises several blades (22,23) in one   material with piezoelectric characteristics   triques with parallel surfaces coated with a material   conductive line (24,25), surfaces which are connected together in parallel, and an elastic blade (30) which carries   the specular surface and which receives the vibra-   roof of blades (22,23) placed next to them.   6 Deflector according to any one of the preceding claims, characterized in that it comprises   takes a support (26,28) adapted to support the deflection   one end, while the other end mite is free to vibrate.