EP0173155B1 - Source d'alimentation pour source lumineuse de capteurs optiques à modulation de fréquence - Google Patents

Source d'alimentation pour source lumineuse de capteurs optiques à modulation de fréquence Download PDF

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Publication number
EP0173155B1
EP0173155B1 EP85110083A EP85110083A EP0173155B1 EP 0173155 B1 EP0173155 B1 EP 0173155B1 EP 85110083 A EP85110083 A EP 85110083A EP 85110083 A EP85110083 A EP 85110083A EP 0173155 B1 EP0173155 B1 EP 0173155B1
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EP
European Patent Office
Prior art keywords
fact
resistor
current supply
signal
supply according
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.)
Expired - Lifetime
Application number
EP85110083A
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German (de)
English (en)
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EP0173155A3 (en
EP0173155A2 (fr
Inventor
Alfred Dr. Reule
Joachim Dipl.-Ing. Schröder
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.)
Carl Zeiss SMT GmbH
Carl Zeiss AG
Original Assignee
Carl Zeiss SMT GmbH
Carl Zeiss AG
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Publication date
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Publication of EP0173155A2 publication Critical patent/EP0173155A2/fr
Publication of EP0173155A3 publication Critical patent/EP0173155A3/de
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Publication of EP0173155B1 publication Critical patent/EP0173155B1/fr
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    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
    • G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
    • G05F1/10—Regulating voltage or current
    • G05F1/625—Regulating voltage or current wherein it is irrelevant whether the variable actually regulated is ac or dc
    • G05F1/63—Regulating voltage or current wherein it is irrelevant whether the variable actually regulated is ac or dc using variable impedances in series with the load as final control devices
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits

Definitions

  • the present invention relates to a power supply for an LED or a semiconductor laser for frequency-analog optical, preferably Foseroptician, sensors for generating a modulation signal with a time-modulated, constant amplitude.
  • Frequency-analog optical sensors are characterized by the fact that they are less disturbed by environmental influences than other optical sensors that measure the intensity or phase of the light.
  • the radiation source is usually modulated with the measuring frequency. This is done most simply and therefore most often by modulating the feed current of the radiation source. Such a modulation is e.g. known from DE-OS 32 02 089 for a fiber optic temperature sensor.
  • the present invention is therefore based on the object of operating an LED or a semiconductor laser in such a way that the disadvantages mentioned are avoided or at least greatly reduced.
  • the object is achieved according to the invention in that a reference receiver is provided, to which part of the radiation from the LED or the semiconductor laser is supplied, and in that a variable resistor is connected in series with the LED or the semiconductor laser, the change in which increases the rise time of the modulation signal is kept constant.
  • rise time is understood to mean the time delay between the modulation signal and the reference signal.
  • rectangular modulation it corresponds to the size usually referred to as the rise time; with sinusoidal modulation it corresponds to the phase shift.
  • variable resistor is a photoresistor illuminated by a light source or a thermistor heated by a heating resistor or a potentiometer actuated by a motor.
  • variable resistor is a thermistor heated by its own current.
  • a circuit with suitable parallel and series resistors ensures that a suitable characteristic curve is created (as shown in FIG. 3a).
  • variable resistor does not change itself - as in the last-mentioned embodiment - a suitable control or regulating arrangement is required for the variation of the resistor.
  • a resistor is connected in series with the LED or the semiconductor laser to generate a control signal and is connected via a RC element for averaging the voltage to a differential amplifier, the second input of which is connected to a setting value transmitter.
  • a resistor in order to generate a control signal for the variable resistor, is connected in series with the LED or the semiconductor laser and is connected via a RC element for averaging the voltage to a network which has a non-linear characteristic.
  • the modulation signal can be both rectangular and e.g. be sinusoidal or triangular.
  • a differential amplifier for generating a control signal for the variable resistor in order to form a differential signal between the preset signal and the reference signal.
  • the output of this differential amplifier is compared in a second differential amplifier with the output of a set value and its difference is fed to an integrator, the output of which is connected to a sample and hold amplifier.
  • the integrator can be switched on on one or on both edges of the modulation signal.
  • the advantage of the present invention is that the ideal modulation signal, which is fundamentally unattainable, is replaced by a modulation signal which not only has a constant amplitude but also a constant rise time. This prevents disturbances and measurement inaccuracies caused by changes in the rise time.
  • 12a denotes an LED, the radiation of which is directed into the optical fiber 13f via the converging lenses 13a and 13b.
  • the radiation reflected on the inclined starting surface of the light guide 13f and on the surface 13e surrounding the starting surface is imaged by the converging lenses 13c and 13d onto the reference receiver 14a, for example a photodiode, and generates an electrical signal there.
  • This is amplified in amplifier 14b and then compared as reference signal 14 in differential amplifier 11a with preset signal 11.
  • the default signal should have the rectangular course shown in the time diagram in FIG. 2a.
  • a sinusoidal or triangular course would also be possible, for example.
  • the reference signal 11 has the course shown in solid lines in FIG. 2b due to the time constants of the radiation source and the time constants of the other components involved. It should be noted that the settling process shown at a frequency of approx. 1 kHz is shorter than 1/100 of the half period.
  • the signal curve shown in solid lines in the time diagram of FIG. 2c is produced. This signal is fed to the integrator 11b, at the output of which the signal curve shown in FIG. 2d arises, which is fed directly - or possibly via an amplifier - to the radiation source 12a.
  • the integrator output thus reaches a higher level and the current through the radiation source 12a is increased so that the reference voltage in FIG. 2b again reaches the same level after the transient response. In this way, a constant amplitude is achieved despite the change in the radiation yield of the radiation source 12a.
  • the regulation takes place so quickly that it regulates itself at the beginning of each modulation half-wave.
  • a variable resistor 12b and a fixed resistor 12d are connected in series with the radiation source 12a.
  • a voltage drop occurs across the resistor 12d which is proportional to the current through the radiation source 12a.
  • This voltage drop is averaged by the RC element 15a over many modulation periods, which is possible since temperature changes or aging processes are slow with respect to the modulation frequency.
  • the DC voltage generated by the RC element 15a - which is proportional to the average current through the radiation source 12a - is fed to a differential amplifier 16b, the second input of which is connected to the setting value transmitter 16a.
  • the value for the rise time that is to be kept constant by the control can be set by an adjustable voltage.
  • a light source 17b e.g. supplies an incandescent lamp which illuminates the photoresistor 12b. Together with the shunt 12c, this forms a purely ohmic variable series resistor for the radiation source 12a.
  • the resistor 12c serves to keep the load on the photoresistor low).
  • the photoresistor 12b is changed by the illumination with the light source 17b so that the change in the radiation source 12a is thus compensated for.
  • all other components in the control loop remain unaffected by the change in radiation source 12a.
  • the transient response becomes faster again, i.e. the rise time is shortened and thus brought to the value before the temperature jump.
  • the setting value transmitter 16a and the differential amplifier 16b produce a linear (but not proportional) relationship between the current through the radiation source 12a and the voltage for the light source 17b, the slope being so due to the degree of amplification of the differential amplifier 16b is set so that the rise time remains constant for different currents. (So it is not a regulation but a controller).
  • the linear relationship is a good and in practice in many cases sufficient approximation to keep the rise time constant.
  • the values R 12b of the variable resistor 12b have to be dependent on the current shown in FIG U 12d for the average voltage drop across the resistor 12d or correspond better to this dependency than is possible with a straight line for the voltage for the light source 17b.
  • the dependency shown in FIG. 3a can be calculated. It is better to carry out an experimental determination that can be made, for example, by inserting diaphragms or neutral glasses into the beam path between radiation source 12a and reference receiver 14a and thereby (with the amplitude control switched on) generating different currents for the radiation source 12a. By observing the reference signal (FIG. 2b), for example with an oscilloscope, the resistor 12b can be changed so that the rise time remains constant.
  • the values U 17b for the correct voltages of the incandescent lamp 17b, with which the exact changes in the resistance 12b are achieved, are also plotted in FIG. 3a.
  • the network shown in FIG. 3b, by which the course is approximated by a polygon of n + 1 straight line sections, is suitable for the best possible implementation of this course if n is the number of parallel branches in the network.
  • the known network of Figure 3b consists of a parallel connection of (adjustable) resistors R o to R n , which with increasing voltage U 12d take effect one after the other.
  • circuit part 7 of FIG. 1 can be replaced by the circuit parts 70 and 71 shown in FIGS. 7a and 7b.
  • the thermistor 73 is used as a variable resistor, which is heated by the heating resistor 72.
  • the rest of the structure and the function are the same as in FIG. 1.
  • a potentiometer controlled by the motor 75 is used as the variable resistor.
  • the tracking amplifier 79, the motor 75 and the potentiometer 77 which is operated with a constant voltage 76, form a known tracking system.
  • the tracking amplifier continuously compares the voltage from the tap of the potentiometer 77 with the output voltage of the differential amplifier 16b and moves the tap by driving the motor 75 so that these voltages are the same.
  • the tap of the resistor 78 is mechanically coupled to the tap of the potentiometer 77. In this way, the part of the resistor 78 which acts as a series resistor for the LED 12a depends on the voltage present at the output of the differential amplifier 16b.
  • the characteristic curve for the variable resistance as a function of the current through the radiation source 12a shown in FIG. 3a can also be realized by a thermistor which is only heated by its own current (which flows through it) will.
  • a particularly simple construction results which is shown in FIG.
  • the characteristic curve of the thermistor 81 has been adapted to the specified course (FIG. 3a) by means of the parallel resistor 82 and the series resistor 83 (whose resistance values are only slightly temperature-dependent).
  • the amplitude control via the reference receiver 14a with its amplifier 14b and the differential amplifier 11a and integrator 11b works as in FIG the description of Fig. 1 indicated.
  • FIG. 4 shows a further exemplary embodiment for keeping the rise time constant, in which the variable resistance - in contrast to FIG. 1 - is part of a control loop.
  • the reference signal 14 is compared with the preset signal 11 in the differential amplifier 41.
  • the two input signals are shown in full in the time diagrams of FIGS. 5a and b. (They correspond to FIGS. 2a and b for the amplitude control).
  • the output of the differential amplifier 41 is passed to a second differential amplifier 43, the second input of which is connected to the setting value transmitter 42.
  • the value for the rise time that is to be kept constant by the control can be set by an adjustable voltage.
  • the output signal of the second differential amplifier 43 is shown in solid lines in FIG. 5c. It is fed to the integrator 44 during the times shown in FIG. 5d, the output signal of which is shown in solid lines in FIG. 5e. This output signal is taken over by the sample and hold amplifier 45 outside the integration times. In the regulated state, a constant DC voltage is present at its output, which - if necessary after further amplification in the amplifier 17a - is fed to the light source 17b, as shown in FIG. 1, which illuminates the photoresistor 12b.
  • the reference signal After the temperature jump, the reference signal has the course shown in dashed lines in FIG. 5b. Due to the slower rise of this signal compared to the signal drawn in solid lines, the signal shown in dashed lines in FIG. 5c at the output of the second differential amplifier 43 also decreases more slowly and the output signal of the integrator 44 shown in FIG. 5e increases faster. Since the decrease of the integral is less than the increase within the integration time, the output voltage of the integrator does not reach the initial value again at the end of the integration time, but goes to a higher level. The light source 17b becomes brighter, the photoresistor 12b gets a lower resistance value and the rise time of the radiation source 12a becomes shorter.
  • the circuit part 7 with the light source 17b and the photoresistor 12b can also be shown in FIG. 4 by a combination of heating resistor 72 and thermistor 73, as shown in circuit part 70 of FIG. 7a, or by a potentiometer 78 with motor 75, such as shown in the circuit part 71 of Figure 7b, are replaced. It is possible to combine the various control and regulating arrangements with one another, it being possible for both the generation of the control and regulating signals and the various variable resistors to be combined with one another. It is particularly advantageous to combine the control according to FIG. 1 with the control according to FIG. 4. For this purpose, the output voltage of the amplifier 16b in FIG. 1 is added to the setting value 42 in FIG. 4.
  • the optical fiber of the fiber optic sensor designated 13f, consists of a core and an optical jacket, both of which are designated 61, and the protective coating 61a.
  • the optical fiber 13f is inserted into the holding part 62 without the protective coating 61a and is connected to it by the kit layer 62a.
  • the optical fiber was cut off at an angle of 45 ° to the optical axis and polished together with the surface 62b of the holding part 62 which is also inclined at 45 °.
  • a mirror layer 62c is applied to the surface 62b, with known technology ensuring that the core remained free from the surface 61b of the optical fiber.
  • the optical fiber 13f is imaged, in the direction of the arrow 69 and thus reflected on the receiver 14a. In this way - in contrast to the known arrangements with beam splitters - it is avoided that the coupling-out of the reference light is associated with an energy loss of the radiation coupled into the optical fiber.
  • FIG. 6a The arrangement described with FIG. 6a has the disadvantage that the optical fiber 13f is firmly connected to the holding part 62, so that when the optical fiber is changed, the holding part is also removed and the adjustment to the lenses 13b and 13c is lost. This is avoided in the exemplary embodiments shown in FIGS. 6b and 6c.
  • the optical fiber 13f is secured in the coupling part 63 by the kit layer 63b without a protective jacket 61a.
  • the coupling part 63 is removably seated in the holding part 64, which is firmly connected to the plane plate 65, on the inside of which the mirror layer 65a is applied. After a single adjustment to the lenses 13b and 13c, the holding part 64 can be permanently fixed.
  • FIG. 6c shows an embodiment in which the optical fiber 13f, in turn without a protective cover 61a, is fastened in a coupling part 66 by the kit layer 66a.
  • This coupling part is releasably and centrally pressed onto the holding part 67 with a mechanical device (not shown).
  • An optical fiber 68 with the same core and optical cladding diameters as the optical fiber 13f is cemented into the holding part 67. It has been processed and mirrored together with the optical fiber in the same way as the holding part 62 of FIG. 6a.
  • the detachable connection to the coupling part 66 it can also be permanently fixed after a single adjustment.
  • the light reflected in the direction 69 (FIG. 6a) with the aid of one of the described coupling-out devices is concentrated on the reference receiver 14a by the converging lenses 13c and 13d (FIGS. 1 and 4). In order to reduce the influence of stray light, it may be advantageous to tilt the reference receiver.
  • the spectral distribution of the measuring light must be evaluated by the reference receiver if possible with the same function which is decisive for the effect triggered by the measuring light. This is e.g. in the temperature sensor described in DE-OS 32 02 089 the fluorescence excitation. A precise spectral adjustment of the receiver sensitivity to such a function by means of filters with an unchangeable transmission curve is difficult and would have to be carried out individually with different spectral sensitivity of the receiver. It is therefore expedient to arrange a filter with variable spectral characteristics in the reference beam path. For this purpose, in particular, as shown in FIG. 4, an interference gradient filter 46, which can be displaced perpendicular to the beam path, or, as shown in FIG.
  • an interference filter 13g which can be rotated about an axis perpendicular to the beam path, is suitable.
  • the dependence on the radiation power of the radiation source 12a can be used as the setting criterion. For this, e.g. changed the temperature of the radiation source and selected the filter position with the least dependence on the temperature of the radiation source.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Automation & Control Theory (AREA)
  • Semiconductor Lasers (AREA)
  • Photometry And Measurement Of Optical Pulse Characteristics (AREA)

Claims (9)

  1. Alimentation électrique pour une diode électroluminescente (DEL) ou un laser à semi-conducteur pour capteurs optiques analogiques de fréquence, de préférence à fibres optiques, servant à la génération d'un signal de modulation à amplitude constante modulée dans le temps, caractérisée en ce qu'un récepteur de référence (14a) est prévu, auquel est envoyée une partie du rayonnement de la DEL (12a) ou du laser à semi-conducteur, et qu'une résistance variable (12b, 73, 78, 81) est branchée en série avec la DEL (12a) ou le laser à semi-conducteur, résistance par la variation de laquelle le temps de montée du signal de modulation est maintenu constant.
  2. Alimentation électrique selon la revendication 1, caractérisée en ce que la résistance variable est une photorésistance (12b) éclairée par une source lumineuse (170), une thermistance (73) chauffée par une résistance chauffante (72) ou un potentiomètre (78) manoeuvré par un moteur (75).
  3. Alimentation électrique selon la revendication 1, caractérisée en ce que la résistance variable est une thermistance (81) échauffée par son propre courant.
  4. Alimentation électrique selon la revendication 2, caractérisée en ce que, pour la génération d'un signal de commande de la résistance variable (12b, 73, 78), une résistance (12d) est branchée en série avec la DEL (12a) ou le laser à semi-conducteur et est reliée à travers un élément RC (15a) pour l'établissement d'une tension moyenne à un amplificateur différentiel (16b) dont la seconde entrée est connectée à un générateur (16a) de valeur de réglage pour le temps de montée.
  5. Alimentation électrique selon la revendication 2, caractérisée en ce que, pour la génération d'un signal de commande de la résistance variable (12b, 73, 78), une résistance (12d) est branchée en série avec la DEL (12a) ou le laser à semi-conducteur et est reliée à travers un élément RC (15a) pour l'établissement d'une tension moyenne à un réseau (30).
  6. Alimentation électrique selon la revendication 2, caractérisée en ce que, pour la génération d'un signal de régulation de la résistance variable (12b, 73, 78), un amplificateur différentiel (41) est prévu pour la formation d'un signal de différence entre un signal appliqué (11) et un signal de référence (14), qu'un deuxième amplificateur différentiel (43) pour la formation d'un signal de différence supplémentaire est prévu entre la sortie du premier amplificateur différentiel (41) et la sortie d'un générateur (42) de valeur de réglage pour le temps de montée et que la sortie du deuxième amplificateur différentiel (43) est connectée à un intégrateur (44) dont la sortie est reliée à un amplificateur (45) d'échantillonnage et de maintien.
  7. Alimentation électrique selon la revendication 6, caractérisée en ce que l'intégrateur (44) est enclenché sur l'un ou sur les deux flancs du signal de modulation.
  8. Alimentation électrique selon une des revendications 1 à 7, caractérisée en ce que la face d'entrée (61b, 68b) de la fibre conductrice de lumière (13f) est biseautée et disposée à fleur dans la surface (62b, 65a, 67b) d'une pièce de support (62, 64, 67) et que cette surface (62b, 65a, 67b) et la face d'entrée (61b, 68b) de la fibre conductrice de lumière (13f) sont recouvertes par une couche réfléchissante (62c, 65a, 67c) de manière que seul le coeur de la fibre conductrice de lumière (13f) soit laissé libre.
  9. Alimentation électrique selon une des revendications 1 à 8, caractérisée en ce qu'un dispositif optique (13g, 46) pour changer la répartition spectrale du rayonnement de référence est placé devant le récepteur de référence (14a).
EP85110083A 1984-08-31 1985-08-12 Source d'alimentation pour source lumineuse de capteurs optiques à modulation de fréquence Expired - Lifetime EP0173155B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19843431996 DE3431996A1 (de) 1984-08-31 1984-08-31 Stromversorgung fuer strahlungsquellen von frequenz-analogen optischen sensoren
DE3431996 1984-08-31

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EP0173155A2 EP0173155A2 (fr) 1986-03-05
EP0173155A3 EP0173155A3 (en) 1988-01-07
EP0173155B1 true EP0173155B1 (fr) 1992-02-05

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US (1) US4707838A (fr)
EP (1) EP0173155B1 (fr)
DE (2) DE3431996A1 (fr)

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Publication number Priority date Publication date Assignee Title
CN103872567A (zh) * 2014-03-24 2014-06-18 哈尔滨工业大学 腔外激光频率变换系统及变换方法
CN103872567B (zh) * 2014-03-24 2016-08-17 哈尔滨工业大学 腔外激光频率变换系统及变换方法

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US4707838A (en) 1987-11-17
DE3585347D1 (de) 1992-03-19
EP0173155A3 (en) 1988-01-07
DE3431996A1 (de) 1986-03-13
EP0173155A2 (fr) 1986-03-05

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