EP0428611A1 - Deflection instrument, controllable reflecting device herefor and use hereof - Google Patents

Deflection instrument, controllable reflecting device herefor and use hereof

Info

Publication number
EP0428611A1
EP0428611A1 EP89909720A EP89909720A EP0428611A1 EP 0428611 A1 EP0428611 A1 EP 0428611A1 EP 89909720 A EP89909720 A EP 89909720A EP 89909720 A EP89909720 A EP 89909720A EP 0428611 A1 EP0428611 A1 EP 0428611A1
Authority
EP
European Patent Office
Prior art keywords
mirror
deflection
elements
controllable
mirrors
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP89909720A
Other languages
German (de)
French (fr)
Inventor
Palle Rasmus Jensen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Laser Scan Vision Aps
Original Assignee
Laser Scan Vision Aps
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from DK455888A external-priority patent/DK455888D0/en
Priority claimed from DK634488A external-priority patent/DK634488D0/en
Priority claimed from DK667588A external-priority patent/DK667588D0/en
Application filed by Laser Scan Vision Aps filed Critical Laser Scan Vision Aps
Publication of EP0428611A1 publication Critical patent/EP0428611A1/en
Priority claimed from US07/895,378 external-priority patent/US5245464A/en
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B7/00—Mountings, adjusting means, or light-tight connections, for optical elements
    • G02B7/18—Mountings, adjusting means, or light-tight connections, for optical elements for prisms; for mirrors
    • G02B7/182—Mountings, adjusting means, or light-tight connections, for optical elements for prisms; for mirrors for mirrors
    • G02B7/1821—Mountings, adjusting means, or light-tight connections, for optical elements for prisms; for mirrors for mirrors for rotating or oscillating mirrors
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
    • G06K7/10—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
    • G06K7/10544—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation by scanning of the records by radiation in the optical part of the electromagnetic spectrum
    • G06K7/10554—Moving beam scanning
    • G06K7/10594—Beam path
    • G06K7/10603—Basic scanning using moving elements
    • G06K7/10633—Basic scanning using moving elements by oscillation
    • G06K7/10643—Activating means
    • G06K7/10653—Activating means using flexible or piezoelectric means

Definitions

  • the invention relates to a light deflection instru- ment of the kind disclosed in claim 1.
  • the reflecting device comprises a mirror mounted on two or more arms of piezoelectric material, possibly flexible piezoelectric material, which upon application of an electrical voltage be ⁇ tween the upper side and the lower side of the crys- tal material causes the arms to bend slightly.
  • the crystal materials are connected in pairs to the applied voltage in counter-phase, the mirror will tilt, and thus it is possible to electrically con ⁇ trol the tilting of the mirror both with regard to the extent of the tilt and its direction. If four crystals in cruciform configuration are used, the mirror can be controlled so that an incident beam of light can be reflected as desired.
  • the deflec ⁇ tion of the mirror is, however, quite small, in that the maximum deflection of the crystal is in the order of 0.05 mm to each side, and the ' practi ⁇ cal use of such devices is therefore strongly lim ⁇ ited.
  • a number of crystal elements can be mechanically coupled in series, which is. known for example from USA patent publication no. 4,660,941.
  • a de ⁇ flection device which has a flexible and bendable coupling part disposed between the crystal and the mirror, so that the stiff deflection of the crystal elements can be transferred to the mirror by a kind of hinge effect. This results, however, in a certain attenuation, so that for many applica ⁇ tions the speed of the deflections is inadequate. Similarly, the amplitude of the deflection is lim- ited to the amplitude of the crystal.
  • the object of the invention is therefore to increase the deflection of the mirror as much as possible, and hereby extend the possibilities of application for such devices.
  • the deflection instrument according to the invention By configuring the deflection instrument according to the invention as disclosed and characterized in claim 2, the possibility is provided of generating almost any oscillation pattern for the mirror or the mirrors, and one can hereby make a beam of light which is directed onto the mirror or the mirrors, after reflection from said mirror or mirrors, de ⁇ scribe almost any desired path.
  • the deflection instrument according to the inven ⁇ tion can be configured as disclosed and character ⁇ ized in claim 3, in that this hereby enables the construction of a very compact instrument which is easy to "pump” with oscillation energy, while at the same time control the direction of the mirror's mechanical oscillations.
  • the deflection instrument according to the inven- tion can also be configured as disclosed and char ⁇ acterized in claim 4.
  • This manner of applying en ⁇ ergy to the oscillating system is particularly suitable if several mirrors are to oscillate in step with one another as disclosed and character- ized in claim 5, but moreover has the advantage that it does not demand operational voltages as great as those necessary for the crystal elements.
  • the reflected light can be made to spread itself over a very much greater area, which is particularly advantageous if the instrument is used for the generation of laser -sweep patterns, e.g. for the reading of line codes for example on goods at a cash terminal, in that with this configuration a high sweep-rate as well as a large deflection can be achieved, and at the same time herewith control over the shape of the pattern.
  • the invention also relates to a controllable re ⁇ flecting device as disclosed in the preamble to claim 7, which can be used in deflection instru- ments as described above.
  • a controllable re ⁇ flecting device as disclosed in the preamble to claim 7, which can be used in deflection instru- ments as described above.
  • the invention also relates to a controllable re ⁇ flecting device as disclosed in the preamble to claim 8, which can be used in deflection instru ⁇ ments as described above.
  • the con- trollable reflecting device as characterized in claim 8, the possibility is provided of achieving a very precise tilting or deflection of the mirror without any significant harmonics.
  • the characteristics of* the mechanical oscillation sys- tem can be varied by the use of balls of different sizes, by the use of different binding materials etc.
  • controllable reflecting device As disclosed and charac ⁇ terized in claim 9, the possibility is provided of achieving a very large deflection, in that it be ⁇ comes possible to dispose the balls closely to each other and close to the centre of the mirror, so that a maximum mirror deflection is achieved for a given deflection of the crystal elements.
  • controllable reflecting device By configuring the controllable reflecting device according to the invention as disclosed and charac- terized in claim 10, the possibility is provided of producing it as a very small and slim construction, for example so that the whole of the reflecting de ⁇ vice can be disposed in a tube with an opening for the light.
  • controllable reflecting device By configuring the controllable reflecting device according to the invention as disclosed and charac ⁇ terized in claim 1 1 , dif ferent resonance frequen ⁇ cies can be generated in different directions in a simple manner, so that the reflected light can be made to describe a path with a desired form or di ⁇ rection.
  • the invention has been developed mainly for use in sensing devices such as those in cash terminal in ⁇ stallations, stock control installations or other installations which use optically readable line codes, and as disclosed in claim 12. If several synchronously oscillating mirrors are used in the device, one mirror can be used for emitting the laser-sweep pattern, and the others can be used for detecting the reflected light.
  • Fig. 1 shows the principle of the electrically controllable reflecting device according to a first embodiment of the invention
  • Fig. 2 shows on a larger scale a section along the line 11-11 in fig. 1 ,
  • Fig. 3 shows a section in fig. 2 on an even larger scale.
  • Fig. 4 shows the principle of the controllable reflecting device according to a second embodiment of the invention, and shown in the same manner as fig. 2,
  • Fig. 5 shows an electrical block diagram which illustrates the control of a deflection instrument with a controllable reflection device according to the invention.
  • Fig. 6 shows an electrical block diagram which shows the control of a deflection instru- ment with a controllable reflection device according to a specially preferred embodi ⁇ ment of the invention
  • Fig. 7 shows a third embodiment of a controllable reflection device
  • Fig. 8 shows a fourth embodiment of a controllable reflection device
  • Fig. 9 shows a fifth and particularly advantageous embodiment of a controllable reflection de ⁇ vice according to the invention
  • Fig. 10 shows the embodiment in fig. 7 seen in per- spective
  • Fig. 11 shows a sixth embodiment of a controllable reflection device according to the inven ⁇ tion
  • Fig. 12 shows the same as in fig. 11, but in per ⁇ spective.
  • Fig. 13 shows the same as in fig. 11, but seen from below.
  • Fig. 14 shows the same as in fig. 11, but with an alternative method of securing the plastic or rubber cylinder,
  • Fig. 15 shows a seventh embodiment of a controllable reflection device according to the inven ⁇ tion, and with electromechanical drive sys ⁇ tem,
  • Fig. 16 shows an eighth embodiment of the inven ⁇ tion, but in which many mirrors oscillate synchronousl .
  • Fig. 17 shows an embodiment of an electromechanical drive system for the embodiment in fig. 16,
  • Fig. 18 shows an alternative embodiment of an elec ⁇ tromechanical drive system for the embodi ⁇ ment shown in fig. 16,
  • Fig. 19 shows a first example of the pattern of the beam path with the embodiment shown in fig. 6,
  • Fig. 20 shows a second example of the pattern of the beam path
  • Fig. 21 shows a third example of the pattern of the beam path
  • Fig. 22 shows, partly in section, a complete de- felection instrument according to the in ⁇ vention for the scanning of a line-code label.
  • Fig. 23 shows an instrument according to an embodi ⁇ ment with a number of controllable reflec ⁇ tion devices which are illuminated from the same light source, and
  • Fig. 24 shows a detail from fig.23 on a larger scale.
  • a small surface mirror 2 is mounted on four arms 3, said arms being piezoelectric crystal elements, so-called bimorph actuators which, for example, are of the type 4322 020 08250 manufactured by Philips.
  • the size of such actuators is in the order of 1.6 x 0.6 x 12 mm.
  • the mirror 2 and the crystals 3 constitute an electrically controllable reflec ⁇ tion device 1.
  • the crystal will bend. If, as shown in fig. 1, the elements are se ⁇ cured in a stationary part 4, the free ends will be raised or lowered, depending on the polarity and strength of the potential difference.
  • the mirror 2 in the shown embodiment is square, but naturally this can be of any desired shape. Its size is in the order of 3 x 3 mm and it is as thin as is practically possible, i.e. of a thickness of less than 0.5 mm.
  • a bearing element in the form of a ball 5 is secured on each element, said ball hav ⁇ ing a diameter in the order of or less than 0.5 mm, so that the four balls form a square with as small a side length as practically possible, e.g. 1 x 1 mm or less.
  • the balls 5 are glued to the elements 3, e.g. with epoxy adhesive or the like, and the mirror is coupled to all of the balls 5 by means of a flex ⁇ ible binding agent 7, e.g. silicone rubber or the like.
  • the bearing elements 5 do not need to be balls, in that elements of other shapes can be used, e.g.
  • a second embodiment of the re- flection device in which the mirror 2 is secured to the elements 3 by means of a rubber part 8 which, for example, as shown can be a cylindrical tube piece with a central opening 12 which is substantially co ⁇ incident with the gap 9 between the arms 3.
  • the rub- ber part is preferably produced of natural rubber or similar material, and is glued to the crystal elements 3 and the underside of the mirror 2.
  • both of the signals 31 and 32 are saw-tooth shaped signal voltages modulated with a low-frequency, sinusoidal voltage of, for example, 1/8 of the frequency of the saw-tooth voltages. These voltages are not necessar ⁇ ily synchronized.
  • the saw-tooth voltages have a fre ⁇ quency which lies in the same order as the resonant frequency of the mirror system 1, i.e.
  • the resonant frequency of the mirror system plus rubber part plus possible additional coupling means for the crystal actuators so that the applied control voltages 31 and 32 will make the mirror 2 tilt at its own reson- ant frequency, and thus the mirror deflection will be many times greater than the degree of deflection which can be achieved with the embodiment shown in fig. 5.
  • a controllable reflecting device 1 in which the cyl ⁇ indrical rubber part 8 is secured by means of a number of support elements 10, which are secured to the crystal elements 3 with a drop of glue 13.
  • the four crystal elements in fig. 7 can be of different lengths. Several resonant frequencies are herewith obtained in the mechanical oscillation system, and thus great deflection at various frequencies and in different directions can be achieved.
  • crys ⁇ tal elements 3 are arranged in parallel and oppo ⁇ site one another, thus providing the possibility of making the controllable reflection device very slim and compact, so that, for example, it can be built into a cylinder or the like.
  • the crystals can, for example, be mounted secured between two print plates held together, and the print plates can be double layer plates and configured in such a manner that the pattern on the two layers is identical but merely turned differently.
  • the support elements 10 in figs. 7-9 are stiff pins, e.g. metal pins, which are glued firmly to the crys ⁇ tal elements 3 with a drop of glue 13.
  • the support elements 10 engage with the rubber part 8, e.g. by being pressed or moulded into the rubber part, or the rubber part can be provided with openings 14 for this purpose.
  • the mirror 2 is shown with stippled lines.
  • the crystal elements 3 can be allowed to os ⁇ cillate in phase by pairs. If leaf springs 11 are used, as shown, these can be moulded into the rub ⁇ ber part 8 and glued to the crystal elements. The leaf springs allow oscillations in the two mechan ⁇ ical systems independently of each other and at right angles to each other. As shown, the moulded in leaf springs can be deformed at the moulded-in end in order to improve the adhesion.
  • the coupling together can also be carried out by means of four pins as shown in fig. 14, these being inserted ra ⁇ dially into the lower part of the rubber cylinder and secured to the crystal elements via the leaf springs 11.
  • a mechanical oscillating system comprises a large number of mirrors 2, each mounted on a rubber part 8 which are all secured (glued) to a common support element 23.
  • the sup ⁇ port element 23 is vibrated in the surface plane, by forced harmonic oscillation the mirrors are made to oscillate in a synchronized manner, so that to ⁇ gether the mirrors function as one large mirror which vibrates just as rapidly and with the same amplitude as the small mirror systems.
  • the sup ⁇ port element 23 is influenced by two different res- onance frequencies, as indicated by the influencing signals 24, 25, special patterns of movement can be achieved.
  • the individual mirrors are arranged so closely together that the effective reflecting sur ⁇ face is made as large as possible, but far enough away from one another to ensure that there is no contact between them during the vibrations.
  • one of the mirrors for example one of the central mir- rors, can be used to emit the desired laser-sweep pattern which illuminates the line code, and all or some of the remaining mirrors can be used to scan the reflected light.
  • Fig. 18 is a sketch showing an alternative way of suspending the common support element by one cen ⁇ trally-placed spring wire 35, thus enabling the vibration of the support element 23 in its own plane to be overlaid by another vibration having its fulcrum in the securing point of the wire, which as shown can be arranged centrally in the support element. It is thus possible at one and the same time to obtain both rapid vibrations and - -- slow vibration, independently of each other, and this is achieved by influencing the electromagnetic drive systems 36 partly with a rapid drive signal 39 and partly with a slow drive signal 38.
  • fig. 20 is shown an example where a resonant fre- quency of 2000 Hz is also used, but where use is made of a set of deflection voltages which are not periodic.
  • the area is hereby completely covered with light, in that the pattern is not repeated but constantly displaced, so that the whole area ap- pears illuminated', the reason being that the laser beam is deflected so quickly that one is unable to perceive that only one scanning of the area is in ⁇ volved.
  • a screen 46 is secured in a piv- otable holder 45 in such a way that the screen can be disposed, for example, over a conveyor on which goods 52 with line-code label 41 are conveyed.
  • a deflection instru ⁇ ment 47 with a laser so that, for example, the pat ⁇ tern which is shown in fig. 19 is emitted towards a mirror 49 rotated by a motor 48.
  • the laser-beam pattern is thrown out onto a rotating or a number of stationary mirrors 51 , so that the goods are illuminated from different sides, thus enabling the line-code label 41 to be scanned, even though it is not facing directly upwards.
  • one or more photo ⁇ cells 50 can be placed at or on the rotating mirror 49.
  • the scanning pattern is hereby brought to cover all directions within the area swept with light.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Optics & Photonics (AREA)
  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Artificial Intelligence (AREA)
  • Computer Vision & Pattern Recognition (AREA)
  • Theoretical Computer Science (AREA)
  • Mechanical Light Control Or Optical Switches (AREA)

Abstract

Le lecteur de codes linéaires décrit comprend un instrument de déflexion comportant un laser (47), à partir duquel un faisceau lumineux est émis depuis un dispositif réflecteur commandable électriquement selon une configuration de balayage laser en direction d'un miroir rotatif (49), et, par l'intermédiaire de miroirs fixes supplémentaires (51), le faisceau lumineux est projeté vers le bas en direction d'un produit (52) comportant une étiquette à code linéaire (41) destinée à être lue. La lumière réfléchie par l'étiquette à code linéaire est balayée au moyen d'une cellule photoélectrique (50). Le dispositif réflecteur commandable équipant l'instrument de déflexion (47) est alimenté en signaux électriques ou en tensions compris dans une fréquence ou modulés par une fréquence égalant ou avoisinant la fréquence de résonance ou les harmoniques desdits signaux ou desdites tensions pour le système d'oscillation mécanique dont le miroir fait partie.The described linear code reader comprises a deflection instrument comprising a laser (47), from which a light beam is emitted from an electrically controllable reflector device in a laser scanning pattern towards a rotating mirror (49), and , via additional fixed mirrors (51), the light beam is projected downwards in the direction of a product (52) carrying a linear code label (41) intended to be read. Light reflected from the linear code tag is scanned by a photocell (50). The controllable reflector device fitted to the deflection instrument (47) is supplied with electrical signals or voltages comprised in a frequency or modulated by a frequency equaling or approaching the resonance frequency or the harmonics of said signals or of said voltages for the system of mechanical oscillation of which the mirror is a part.

Description

DEFLECTION INSTRUMENT, CONTROLLABLE REFLECTING DEVICE HEREFOR AND USE HEREOF.
The invention relates to a light deflection instru- ment of the kind disclosed in claim 1.
Electrically-controllable reflecting devices of the kind disclosed in the preamble to claim 1 are known, for example from Japanese patent publication no. 52- 40215, wherein the reflecting device comprises a mirror mounted on two or more arms of piezoelectric material, possibly flexible piezoelectric material, which upon application of an electrical voltage be¬ tween the upper side and the lower side of the crys- tal material causes the arms to bend slightly.. If the crystal materials are connected in pairs to the applied voltage in counter-phase, the mirror will tilt, and thus it is possible to electrically con¬ trol the tilting of the mirror both with regard to the extent of the tilt and its direction. If four crystals in cruciform configuration are used, the mirror can be controlled so that an incident beam of light can be reflected as desired. The deflec¬ tion of the mirror is, however, quite small, in that the maximum deflection of the crystal is in the order of 0.05 mm to each side, and the'practi¬ cal use of such devices is therefore strongly lim¬ ited. In order to increase the deflection of the mirror, and to make it possible to use a thicker and herewith a more solid but also heavier mirror, a number of crystal elements can be mechanically coupled in series, which is. known for example from USA patent publication no. 4,660,941. However, this results in a mechanically complicated construction. and while the possibility is no doubt provided of greater mirror deflection, the deflection on the other hand is considerably slower, which for some applications is totally unacceptable.
From USA patent publication no. 3,981,566, a de¬ flection device is known which has a flexible and bendable coupling part disposed between the crystal and the mirror, so that the stiff deflection of the crystal elements can be transferred to the mirror by a kind of hinge effect. This results, however, in a certain attenuation, so that for many applica¬ tions the speed of the deflections is inadequate. Similarly, the amplitude of the deflection is lim- ited to the amplitude of the crystal.
The whole of the known technique in this field has limitations with regard to the magnitude of the tilting of the mirror, even though attempts are made, as disclosed in USA patent no. 3,981,566, to allow the deflections of the crystal elements to be transferred to the mirror as closely as at all possible to its centre.
The object of the invention is therefore to increase the deflection of the mirror as much as possible, and hereby extend the possibilities of application for such devices.
This is achieved by configuring the instrument ac¬ cording to the invention as disclosed and charact¬ erized in claim 1 , in that sufficient energy is con¬ stantly applied to the mechanical oscillation system for the resonant oscillations to be maintained at one or more of the system's resonant frequencies; - This results in the deflection of the mirror or the mirrors being multiplied many times, depending on the efficiency of the oscillation system. By constructing the mechanical oscillation system in different ways and with the use of different mat¬ erials, it can be configured so that it assumes one or more resonance frequencies of the desired ex¬ tent and amplitude, depending on the application for which the instrument is to be used.
By configuring the deflection instrument according to the invention as disclosed and characterized in claim 2, the possibility is provided of generating almost any oscillation pattern for the mirror or the mirrors, and one can hereby make a beam of light which is directed onto the mirror or the mirrors, after reflection from said mirror or mirrors, de¬ scribe almost any desired path.
The deflection instrument according to the inven¬ tion can be configured as disclosed and character¬ ized in claim 3, in that this hereby enables the construction of a very compact instrument which is easy to "pump" with oscillation energy, while at the same time control the direction of the mirror's mechanical oscillations.
The deflection instrument according to the inven- tion can also be configured as disclosed and char¬ acterized in claim 4. This manner of applying en¬ ergy to the oscillating system is particularly suitable if several mirrors are to oscillate in step with one another as disclosed and character- ized in claim 5, but moreover has the advantage that it does not demand operational voltages as great as those necessary for the crystal elements.
By configuring the deflection instrument as dis¬ closed and characterized in claim 6, the reflected light can be made to spread itself over a very much greater area, which is particularly advantageous if the instrument is used for the generation of laser -sweep patterns, e.g. for the reading of line codes for example on goods at a cash terminal, in that with this configuration a high sweep-rate as well as a large deflection can be achieved, and at the same time herewith control over the shape of the pattern.
The invention also relates to a controllable re¬ flecting device as disclosed in the preamble to claim 7, which can be used in deflection instru- ments as described above. By configuring the re¬ flecting device as disclosed and characterized in claim 7, the possibility is provided of maximizing the deflection and of a relatively simple assembly process for the mirror, which is normally glued directly to a rubber or plastic mounting. The pos¬ sibility is also provided of achieving more uni¬ form products, and by the selection of the type of plastic or rubber one can change the characterist¬ ics of the mirror system with regard to resonant frequencies and quality. By configuring or dispos¬ ing the plastic or rubber cylinder asymmetrically or as a rectangular cylinder instead of a circular cylinder, one can generate various resonant fre¬ quencies in different directions. The invention also relates to a controllable re¬ flecting device as disclosed in the preamble to claim 8, which can be used in deflection instru¬ ments as described above. By configuring the con- trollable reflecting device as characterized in claim 8, the possibility is provided of achieving a very precise tilting or deflection of the mirror without any significant harmonics. Moreover, the characteristics of* the mechanical oscillation sys- tem can be varied by the use of balls of different sizes, by the use of different binding materials etc.
By configuring the controllable reflecting device according to the invention as disclosed and charac¬ terized in claim 9, the possibility is provided of achieving a very large deflection, in that it be¬ comes possible to dispose the balls closely to each other and close to the centre of the mirror, so that a maximum mirror deflection is achieved for a given deflection of the crystal elements.
By configuring the controllable reflecting device according to the invention as disclosed and charac- terized in claim 10, the possibility is provided of producing it as a very small and slim construction, for example so that the whole of the reflecting de¬ vice can be disposed in a tube with an opening for the light.
By configuring the controllable reflecting device according to the invention as disclosed and charac¬ terized in claim 1 1 , dif ferent resonance frequen¬ cies can be generated in different directions in a simple manner, so that the reflected light can be made to describe a path with a desired form or di¬ rection.
The invention has been developed mainly for use in sensing devices such as those in cash terminal in¬ stallations, stock control installations or other installations which use optically readable line codes, and as disclosed in claim 12. If several synchronously oscillating mirrors are used in the device, one mirror can be used for emitting the laser-sweep pattern, and the others can be used for detecting the reflected light. One hereby achieves quick reading of a line-code label, particularly if itisnotpositioned in a certain way, which for example is the case with line-code labels on foodstuffs on a conveyor belt at a cash terminal.
The invention will now be described in more detail with reference to the drawing, in that
Fig. 1 shows the principle of the electrically controllable reflecting device according to a first embodiment of the invention,
Fig. 2 shows on a larger scale a section along the line 11-11 in fig. 1 ,
Fig. 3 shows a section in fig. 2 on an even larger scale.
Fig. 4 shows the principle of the controllable reflecting device according to a second embodiment of the invention, and shown in the same manner as fig. 2,
Fig. 5 shows an electrical block diagram which illustrates the control of a deflection instrument with a controllable reflection device according to the invention.
Fig. 6 shows an electrical block diagram which shows the control of a deflection instru- ment with a controllable reflection device according to a specially preferred embodi¬ ment of the invention,
Fig. 7 shows a third embodiment of a controllable reflection device,
Fig. 8 shows a fourth embodiment of a controllable reflection device,
Fig. 9 shows a fifth and particularly advantageous embodiment of a controllable reflection de¬ vice according to the invention,
Fig. 10 shows the embodiment in fig. 7 seen in per- spective,
Fig. 11 shows a sixth embodiment of a controllable reflection device according to the inven¬ tion,
Fig. 12 shows the same as in fig. 11, but in per¬ spective.
Fig. 13 shows the same as in fig. 11, but seen from below. Fig. 14 shows the same as in fig. 11, but with an alternative method of securing the plastic or rubber cylinder,
Fig. 15 shows a seventh embodiment of a controllable reflection device according to the inven¬ tion, and with electromechanical drive sys¬ tem,
Fig. 16 shows an eighth embodiment of the inven¬ tion, but in which many mirrors oscillate synchronousl ,
Fig. 17 shows an embodiment of an electromechanical drive system for the embodiment in fig. 16,
Fig. 18 shows an alternative embodiment of an elec¬ tromechanical drive system for the embodi¬ ment shown in fig. 16,
Fig. 19 shows a first example of the pattern of the beam path with the embodiment shown in fig. 6,
Fig. 20 shows a second example of the pattern of the beam path,
Fig. 21 shows a third example of the pattern of the beam path,
Fig. 22 shows, partly in section, a complete de- felection instrument according to the in¬ vention for the scanning of a line-code label. Fig. 23 shows an instrument according to an embodi¬ ment with a number of controllable reflec¬ tion devices which are illuminated from the same light source, and
Fig. 24 shows a detail from fig.23 on a larger scale.
In figs. 1-3 of the drawing it will be seen that a small surface mirror 2 is mounted on four arms 3, said arms being piezoelectric crystal elements, so-called bimorph actuators which, for example, are of the type 4322 020 08250 manufactured by Philips. The size of such actuators is in the order of 1.6 x 0.6 x 12 mm. Together, the mirror 2 and the crystals 3 constitute an electrically controllable reflec¬ tion device 1. When a potential difference is ap¬ plied between the upper and the lower sides of the crystals through the leads 3', the crystal will bend. If, as shown in fig. 1, the elements are se¬ cured in a stationary part 4, the free ends will be raised or lowered, depending on the polarity and strength of the potential difference.
The crystal elements are arranged together in a staggered cross, in that opposite elements are com¬ pletely offset from each other, but where all of the elements are arranged so that they form a right- angled cross. Between the free ends there are gaps 9 in the order of 0.1-0.5 mm.
The mirror 2 in the shown embodiment is square, but naturally this can be of any desired shape. Its size is in the order of 3 x 3 mm and it is as thin as is practically possible, i.e. of a thickness of less than 0.5 mm.
As closely as possible to the centre-facing corner of the elements 3, a bearing element in the form of a ball 5 is secured on each element, said ball hav¬ ing a diameter in the order of or less than 0.5 mm, so that the four balls form a square with as small a side length as practically possible, e.g. 1 x 1 mm or less. The balls 5 are glued to the elements 3, e.g. with epoxy adhesive or the like, and the mirror is coupled to all of the balls 5 by means of a flex¬ ible binding agent 7, e.g. silicone rubber or the like. The bearing elements 5 do not need to be balls, in that elements of other shapes can be used, e.g. cylindrical or box-shaped, though preferably with double curvature surface at the coupling to the mirror. The bearing elements can be shaped or fashioned so that the binding agent adheres better hereto, and the mirror can herewith be given greater effects. The bearing elements can be balls of steel or glass, plastic etc., and can be configured with a special surface structure which increases the ad¬ hesion. The bearing elements must be large enough to lift the mirror completely free of the elements 3 at maximum deflection, i.e. a diameter of less than 0.5 mm is normally sufficient.
In fig. 4 is seen a second embodiment of the re- flection device in which the mirror 2 is secured to the elements 3 by means of a rubber part 8 which, for example, as shown can be a cylindrical tube piece with a central opening 12 which is substantially co¬ incident with the gap 9 between the arms 3. The rub- ber part is preferably produced of natural rubber or similar material, and is glued to the crystal elements 3 and the underside of the mirror 2.
In fig. 5 will be seen a block diagram of a deflec¬ tion instrument according to the invention with a controllable reflection device 1. The light from a laser 19 is reflected from the mirror towards a wall or screen (not shown) . Oppositely-lying elements in the reflection device 1 are electrically coupled in pairs and in counter-phase, so that those elements which lie in staggered extension of each other move in opposite directions in response to the same ap¬ plied signal, i.e. the one element bends upwards and the oppositely-lying element bends downwards. The mirror will thus tilt around an axis through the balls or the rubber part, which is shown schematic¬ ally by the stippled line in the segment figure in fig. 1. In this manner, by applying suitable x-y signals to the two sets of elements, the mirror can be tilted in any desired direction, depending on the phase and the strength of the applied signals. The elements are driven by supplying them with a driving voltage from the drive circuit 20, which is supplied with a DC voltage in the order of +200 VDC. The control signals are applied to the input elec¬ trodes 22, and the one x-signal and the one y-sig- nal are inverted by the inversion circuits 30 which, for example, are each built up with their own op- erational amplifiers as shown.
In fig. 6 is shown a specially preferred embodiment in which the reflection device is driven by two push-pull drive stages 29, one for the x-signals and one for the y-signals. The two push-pull stages 29 are supplied, for example, with control signals 31 and 32 as shown. In the embodiment shown, both of the signals 31 and 32 are saw-tooth shaped signal voltages modulated with a low-frequency, sinusoidal voltage of, for example, 1/8 of the frequency of the saw-tooth voltages. These voltages are not necessar¬ ily synchronized. The saw-tooth voltages have a fre¬ quency which lies in the same order as the resonant frequency of the mirror system 1, i.e. the resonant frequency of the mirror system plus rubber part plus possible additional coupling means for the crystal actuators, so that the applied control voltages 31 and 32 will make the mirror 2 tilt at its own reson- ant frequency, and thus the mirror deflection will be many times greater than the degree of deflection which can be achieved with the embodiment shown in fig. 5.
In figs. 7 and 10 is seen another embodiment of a controllable reflecting device 1 in which the cyl¬ indrical rubber part 8 is secured by means of a number of support elements 10, which are secured to the crystal elements 3 with a drop of glue 13. The four crystal elements in fig. 7 can be of different lengths. Several resonant frequencies are herewith obtained in the mechanical oscillation system, and thus great deflection at various frequencies and in different directions can be achieved.
In fig. 8 it will be seen that the flexible rubber part 8 can be configured or arranged in an unsym- metrical manner, so that various resonant frequen¬ cies in different directions can be obtained. As shown, the rubber part can, for example, be in the form of a rectangular cylinder instead of a circu¬ lar cylinder as shown in fig. 7.
In fig. 9 is shown an embodiment in which the crys¬ tal elements 3 are arranged in parallel and oppo¬ site one another, thus providing the possibility of making the controllable reflection device very slim and compact, so that, for example, it can be built into a cylinder or the like. The crystals can, for example, be mounted secured between two print plates held together, and the print plates can be double layer plates and configured in such a manner that the pattern on the two layers is identical but merely turned differently.
The support elements 10 in figs. 7-9 are stiff pins, e.g. metal pins, which are glued firmly to the crys¬ tal elements 3 with a drop of glue 13. The support elements 10 engage with the rubber part 8, e.g. by being pressed or moulded into the rubber part, or the rubber part can be provided with openings 14 for this purpose. In figs. 7-10 the mirror 2 is shown with stippled lines.
In figs. 11-14 is shown an embodiment of the inven¬ tion in which the crystal elements 3 are all paral¬ lel and disposed around the rubber part 8, on which the mirror 2 is glued. The crystal elements are (not shown) secured against a core with a rectang¬ ular or quadratic cross-section. On each crystal element there is mounted (glued) a support element
10 or 11 in the form of a pin 10 or a spring portion
11 which engages with the rubber. With this e bodi- ment, the crystal elements 3 can be allowed to os¬ cillate in phase by pairs. If leaf springs 11 are used, as shown, these can be moulded into the rub¬ ber part 8 and glued to the crystal elements. The leaf springs allow oscillations in the two mechan¬ ical systems independently of each other and at right angles to each other. As shown, the moulded in leaf springs can be deformed at the moulded-in end in order to improve the adhesion. The coupling together can also be carried out by means of four pins as shown in fig. 14, these being inserted ra¬ dially into the lower part of the rubber cylinder and secured to the crystal elements via the leaf springs 11.
In all of the embodiments described in the above, the oscillatory energy for the mechanical oscilla¬ tion system is supplied from electrically-control¬ lable crystal elements. It is also possible to sup- ply the energy in other ways, e.g. by means of an electromechanical system coupled to the rubber part.
Fig. 15 shows a section of an embodiment of the in¬ vention in which the mechanical oscillation system is mounted on a guide pin 16 which, for example, is introduced into the opening in a rubber cylinder 8 on which a mirror 2 is glued. In the rubber part 8 there is secured an annular disk 17 which is influ¬ enced by a number of electromagnets 15, e.g. by employing permanent magnets 18 on the disk 17. If four magnets 18 and four electromagnets 15 are used, all turned oppositely pairwise, the rubber cylinder 8 with the mirror 2 can be brought into resonant oscillation in any desired direction by controlling the current to the electromagnets 15.
In fig. 16 is seen the principle of an embodiment of the invention in which a mechanical oscillating system comprises a large number of mirrors 2, each mounted on a rubber part 8 which are all secured (glued) to a common support element 23. If the sup¬ port element 23 is vibrated in the surface plane, by forced harmonic oscillation the mirrors are made to oscillate in a synchronized manner, so that to¬ gether the mirrors function as one large mirror which vibrates just as rapidly and with the same amplitude as the small mirror systems. If the sup¬ port element 23 is influenced by two different res- onance frequencies, as indicated by the influencing signals 24, 25, special patterns of movement can be achieved. The individual mirrors are arranged so closely together that the effective reflecting sur¬ face is made as large as possible, but far enough away from one another to ensure that there is no contact between them during the vibrations. When such a deflection instrument is used, e.g. in con¬ nection with the scanning of line-code labels, one of the mirrors, for example one of the central mir- rors, can be used to emit the desired laser-sweep pattern which illuminates the line code, and all or some of the remaining mirrors can be used to scan the reflected light.
Fig. 17 is a sketch showing an example of how the vibrations in the common support element 23 in fig. 16 can be brought into oscillations with an elec¬ tromagnetic traction coil system disposed closely under the support element 23. For example, the com- mon support element 23 can be suspended in four spring wires 34, preferably at right angles to the surface. The electromagnetic drive system 33 will thus force the support element 23 to vibrate at right angles to the spring wires 34.
Fig. 18 is a sketch showing an alternative way of suspending the common support element by one cen¬ trally-placed spring wire 35, thus enabling the vibration of the support element 23 in its own plane to be overlaid by another vibration having its fulcrum in the securing point of the wire, which as shown can be arranged centrally in the support element. It is thus possible at one and the same time to obtain both rapid vibrations and - -- slow vibration, independently of each other, and this is achieved by influencing the electromagnetic drive systems 36 partly with a rapid drive signal 39 and partly with a slow drive signal 38.
In figs. 19-21 are shown examples of the light pat¬ terns which arise on a plane arranged at a distance in front of the reflected beams of light from a con¬ trollable reflection device according to the inven- tion, see for example the plane 37 placed in front of the reflection system 1 in fig. 6. If, for ex¬ ample, this plane is a conveyor 40 at a cash term¬ inal or the like, on which a product with a line code label 41 is passing, it will be seen that the line code is scanned by the laser beam several times.
In fig. 19 is shown the use of a resonant frequency of 2000 Hz with 8 complete sweeps per rotatation, which occur with a frequency of 250 Hz, so that 250 complete patterns per second are generated.
In fig. 20 is shown an example where a resonant fre- quency of 2000 Hz is also used, but where use is made of a set of deflection voltages which are not periodic. The area is hereby completely covered with light, in that the pattern is not repeated but constantly displaced, so that the whole area ap- pears illuminated', the reason being that the laser beam is deflected so quickly that one is unable to perceive that only one scanning of the area is in¬ volved.
In fig. 21 is shown an example where resonant fre¬ quencies are effected in the x-direction with 2000 Hz and deflections in the y-direction with 400 Hz. The picture shown is thus repeated 400 times per second.
In fig. 22 is seen a practical example of how the invention is used in connection with the scanning of line-code label. A screen 46 is secured in a piv- otable holder 45 in such a way that the screen can be disposed, for example, over a conveyor on which goods 52 with line-code label 41 are conveyed.
Inside the screen 46 is placed a deflection instru¬ ment 47 with a laser, so that, for example, the pat¬ tern which is shown in fig. 19 is emitted towards a mirror 49 rotated by a motor 48. From the mirror 49, the laser-beam pattern is thrown out onto a rotating or a number of stationary mirrors 51 , so that the goods are illuminated from different sides, thus enabling the line-code label 41 to be scanned, even though it is not facing directly upwards. For the detection of the reflected light, one or more photo¬ cells 50 can be placed at or on the rotating mirror 49. The scanning pattern is hereby brought to cover all directions within the area swept with light.
In figs. 23 and 24 is shown another embodiment of the reflecting device according to the invention, in that a number of reflection devices 1 ' are ar- ranged in series with one laser 19, and where each reflection device 1 ' is controlled by each its con¬ trol and driving circuit 28, which are all control¬ led by one common control circuit 27, e.g. a pro¬ grammable computer. The reflection device is seen in greater detail in fig. 24, and in this construc¬ tion there is used a mirror 2' which is partly re¬ flecting and partly translucent, so that the light from the laser 19 can reach all of the mirrors 2' . For practical reasons, it is necessary with this embodiment for the gap 9' between the elements 3 to be made so broad that the light beam can pass under all conditions. With such a device, a so-called rolling display can be generated, so that a series of characters can be written on a suitable screen placed in front of the device, all controlled by the electronic control circuit 27. With this appli¬ cation, use will be made mainly of reflection dev¬ ices with balls between the crystal elements and the mirror, and of the kind which has been described in connection with figs. 1-3, in that with this con¬ struction a well-defined deflection is achieved without harmonics.
In the application, there is essentially only dis- cussed transmission of light, i.e. the illumination of a surface with a laser-beam pattern. If this light pattern is used to illuminate line-code labels on goods, the scanning of the information contained in the line-codes is effected in a commonly-known manner, i.e. by an optical scanning of the light reflected from the illuminated line-code label, and the transfer of the optically-scanned signals to electronic circuits of a known kind.

Claims

C L A I S
1. Deflection instrument for light comprising at least one mirror (1, 1') or a reflecting surface supported by and coupled flexibly to a number of movable elements (3, 23), which are controllable or can be manoeuvred under the application of electri¬ cal signals or voltages (24, 25, 31, 32, 36, 38), and is arranged in such a manner that the mirror or the mirrors can be tilted away from the posi¬ tion of rest in any desired direction as a function of the electrical signals or voltages, said mirror or mirrors being arranged to reflect incident light, c h a r a c t e r i z e d in that the electrical signals or voltages have a frequency or are modu¬ lated with a frequency of or in the vicinity of the resonant frequency or harmonics hereof, by a mechan¬ ical oscillation system comprising the mirror (1, 1 ' ) or the mirrors, the supporting and movable el- ements (3, 23) and possible coupling means (5, 6, 7, 8, 10, 11) between them.
2. Deflection instrument according to claim 1 , c h a r a c t e r i z e d in that the movable el- ements are not all supplied with electrical signals or voltages of the same frequency.
3. Deflection instrument according to claim 1 or 2, c h a r a c t e r i z e d in that the movable elements are piezo-electric crystal elements (3) , so-called bimorph actuators.
4. Deflection instrument according to claim 1 or 2, c h a r a c t e r i z e d in that the movable elements are electromagnetic elements (15, 18, 33, 36) , or elements coupled to electromagnetic ele¬ ments.
5. Deflection instrument according to claim 1, c h a r a c t e r i z e d in that it comprises a number of mirrors (1) disposed on or connected to a common supporting element (23) , said supporting element being supp.lied with oscillatory energy and forming part of the mechanical oscillation system.
6. Deflection instrument according to claim 1 or 5, c h a r a c t e r i z e d in that in the light path in front of the instrument (47) there is dis- posed at least one rotating mirror (49) and pos¬ sibly one or a number of stationary mirrors (51).
7. Controllable reflecting device for deflection instrument for the deflection of light, and where at least one mirror (1, 1') or a reflecting sur¬ face is supported by and flexibly coupled to a num¬ ber of movable elements (3) which are controllable or can be manoeuvred under the application of el¬ ectrical signals or voltages, so that the mirror or mirrors can be tilted away from their position of rest, c h a r a c t e r i z e d in that the flexible coupling consists of a flexible rubber or plastic part (8) which supports the mirror and is secured or coupled to the movable elements, said rubber or plastic part being configured as a cyl¬ indrical tube section with a though-going hole (12) .
8. Controllable reflecting device for deflection instrument for the deflection of light, and where at least one mirror (1, 1') or a reflecting surface is supported by and flexibly coupled to a number of movable elements (3) which are controllable or can be manoeuvred under the application of electrical signals or voltages, so that the mirror or mirrors can be tilted away from their position of rest, c h a r a c t e r i z e d in that the flexible coupling consists of one or a number of balls (5) secured to each of the movable elements (3), and flexibly coupled to the mirror by means of a bind¬ ing agent (7) .
9. Controllable reflecting device according to claim 7 or 8, c h a r a c t e r i z e d in that the movable elements (3) are elongated, substantially rectangular, piezo-electric crystal elements with a short side facing towards the mirror and offset for substantially half of their breadth in relation to the central area of the mirror. (fig. 1).
10. Controllable reflecting device according to claim 7 or 8, c h a r a c t e r i z e d in that four elongated, substantially rectangular piezo-el- ectric crystal elements are used, these being ar¬ ranged in pairs in parallel and with coincident longitudinal axes (fig. 9) .
11. Controllable reflecting device according to any of the claims 7-10, c h a r a c t e r i z e d in that the piezo-electric crystal elements are not all of the same length (fig. 7) .
12. The use of the deflection instrument or control- lable reflecting device according to any of the foregoing claims, and where the mirror or mirrors are illuminated from at least one preferably mono¬ chromatic light source, e.g. a laser, for the il¬ lumination of optical line codes (41) in connection with the reading of the information contained herein.
EP89909720A 1988-08-12 1989-08-10 Deflection instrument, controllable reflecting device herefor and use hereof Withdrawn EP0428611A1 (en)

Applications Claiming Priority (7)

Application Number Priority Date Filing Date Title
DK4558/88 1988-08-12
DK455888A DK455888D0 (en) 1988-08-12 1988-08-12 ELECTRICALLY CONTROLLABLE MIRROR AND DEVICE WITH SUCH A DEVICE
DK634488A DK634488D0 (en) 1988-11-14 1988-11-14 LASER SCANNER
DK6344/88 1988-11-14
DK667588A DK667588D0 (en) 1988-11-30 1988-11-30 LASER SCANNER II
DK6675/88 1988-11-30
US07/895,378 US5245464A (en) 1988-08-12 1992-06-08 Deflecting instrument, controllable reflecting device herefor and use hereof

Publications (1)

Publication Number Publication Date
EP0428611A1 true EP0428611A1 (en) 1991-05-29

Family

ID=27439715

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EP89909720A Withdrawn EP0428611A1 (en) 1988-08-12 1989-08-10 Deflection instrument, controllable reflecting device herefor and use hereof

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EP (1) EP0428611A1 (en)
JP (1) JPH04505969A (en)
AU (1) AU4182989A (en)
WO (1) WO1990001715A1 (en)

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US5280165A (en) * 1989-10-30 1994-01-18 Symbol Technolgoies, Inc. Scan pattern generators for bar code symbol readers
IT1242638B (en) * 1990-11-15 1994-05-16 Hal 9000 Informatica Srl ALTERNATIVE LASER LIGHT DEFLECTOR
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US5475207A (en) 1992-07-14 1995-12-12 Spectra-Physics Scanning Systems, Inc. Multiple plane scanning system for data reading applications
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Also Published As

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WO1990001715A1 (en) 1990-02-22
JPH04505969A (en) 1992-10-15
AU4182989A (en) 1990-03-05

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