Coding device, light source of a coding device and measuring method

Abstract

Coding device (10), comprising: a light source (11), comprising: a battery (1); an amplifier circuit (3) which amplifies a supply voltage output by the battery (1) and which outputs the amplified voltage; a light-emitting element (4) at one end of which the increased voltage is applied; a driver circuit (5) which is inserted between another end of the light-emitting element (4) and an earth, wherein the driver circuit (5) controls or regulates the current flowing through the light-emitting element (4); a voltage sensing circuit (6) which detects a voltage between the light-emitting element (4) and the driver circuit (5); and a control circuit (2) which controls or regulates the amplifier circuit (3) to amplify the supply voltage when the voltage detected by the voltage sensing circuit (6) is lower than the supply voltage, which stops the amplification carried out by the amplifier circuit (3) when the voltage detected by the voltage sensing circuit (6) is equal to the supply voltage, and which controls or regulates the driver circuit (5) such that, after the amplified voltage supplied to the light-emitting element (4) has reached a certain value, current flows to the light-emitting element (4); a scale (21) which receives light from the light source (11); a light receiver (23) which receives the light from the scale (21) and which outputs a signal corresponding to the received light; and a signal processing device (25) which calculates a positional relationship between the light receiver (23) and the scale (21) according to the signal from the light receiver (23); wherein the amplifier circuit (3) comprises: a first diode (D1), to whose anode the supply voltage is applied; a first capacitor (C1), one end of which is connected to the earth; a second diode (D2) whose anode is connected to a cathode of the first diode (D1), and whose cathode is connected to a high-voltage end of the light-emitting element (4) and to another end of the first capacitor (C1); a second capacitor (C2), one end of which is connected to the control circuit (2), and the other end of which is connected to the cathode of the first diode (D1) and to the anode of the second diode (D2), wherein, when the supply voltage is amplified by the amplifier circuit (3), the control circuit (2) supplies a pulse signal to the second capacitor (C2), wherein the capacitance value of the first capacitor (C1) is preferably higher than the capacitance value of the second capacitor (C2).

Description

CROSS-REFERENCE TO RELATED REGISTRATIONS

[0001] This application claims priority over Japanese application no. 2016-235960, filed on December 5, 2016, the disclosure of which is explicitly included herein by cross-reference in its entirety. BACKGROUND OF THE INVENTION 1. Field of the invention

[0002] This invention relates to a coding device, a light source of a coding device and a measuring method for measuring a positional relationship. 2. Description of the related technology

[0003] An encoding device is installed in devices for measuring displacements, such as a dial gauge for measuring a displacement magnitude. A well-known example of such an encoding device is an optical encoding device, which uses optical interference to measure the displacement magnitude. Furthermore, encoding devices are broadly divided into incremental encoders, which measure a relative displacement magnitude, and absolute encoders, which detect an absolute position. For example, the specifications of US patents 7,608,813 B1 and 8,309,906 B2 propose configurations for an optical absolute encoder.

[0004] In a handheld displacement measuring device, a small, lightweight button cell is used as the power source for the optical encoding unit. With such a displacement measuring device, the battery life can preferably be extended as much as possible.

[0005] An incremental encoder, however, can only measure the magnitude of a relative displacement and therefore must continuously measure the displacement. Consequently, a light source for the optical encoder must be illuminated at all times, which unfortunately results in considerable power consumption. Absolute encoders, on the other hand, can detect an absolute position. Therefore, it is sufficient to illuminate the light source intermittently, only when the position is being detected, and power consumption can be reduced.

[0006] In optical coding devices, a light-emitting element, such as a light-emitting diode (LED), can be used as the light source. The forward voltage required for the LED to emit light is between 1.6 V and 4 V. In contrast, the nominal voltage is usually set by a battery, and in the case of a button cell, the nominal voltage is typically 3 V. However, the battery's output voltage is highest when it is first used and decreases as it is discharged. When the output voltage of such a battery drops to a certain level, it generally exhibits steep discharge characteristics. For example, if a coin-shaped lithium battery is used, its nominal voltage is 3 V, but when the output voltage drops to between 2.5 V and 2.7 V, it then decreases significantly.

[0007] If the supply voltage output by the battery can be detected with satisfactory accuracy, the battery can be used as a power source until the supply voltage drops to 2.7 V. However, since this requires a high-precision voltage detection circuit, the coding device must function until the supply voltage falls below 2.5 V if such a circuit cannot be provided. Due to the forward voltage of the light-emitting diode (LED), a situation may arise where the supply voltage does not reach the LED's forward voltage, making it impossible to drive the LED.

[0008] Therefore, a common approach is to amplify the supply voltage and feed the resulting voltage to the light-emitting diode. For example, it is conceivable to perform the amplification using a DC-DC converter, but a DC-DC converter consumes a comparatively large amount of current and can therefore shorten the battery's lifespan. In other words, from the perspective of minimizing power consumption, the use of a DC-DC converter is not preferable.

[0009] If a boosted voltage is used, a point may occur in a circuit containing the light source where the voltage is higher than the supply voltage, and the boosted voltage may exceed a test voltage of a circuit downstream of the battery, or a backflow of electrical current to the battery may occur. If the battery is a primary battery, a backflow of electrical current to the battery may damage it.

[0010] US 2004 / 0240602A1 describes a device for counting the rotation frequency of a number wheel of a counter for a remote meter reading system, applied to a counter in which the numerical value of a number wheel counter formed with a plurality of number wheels, wherein the device comprises: a light reflection device attached to a part of the outer surface of any number wheel of the number wheel counter, such that a surface of the light reflection device with a high reflection rate faces outwards, and which reflects an incident infrared beam when rotated with the number wheel; a light sensor unit in which two independent holes are formed on one side of a housing made of an opaque material, and an infrared emitter, which receives a drive pulse signal and intermittently emits an infrared beam, is arranged within a first hole, and an infrared beam sensor, which outputs an electrical signal proportional to the amount of light of an infrared beam flowing into a second hole, is arranged within the second hole;a light sensor mounting housing having a structure in which the housing is detachably coupled to the measuring instrument, while the light sensor unit is mounted and secured inside the housing, and in an assembled state of the housing the first hole and the second holes are arranged over a rotational path of the digit wheel to which the light reflector is attached, and at least a part of the housing covering the digit wheel counter and a part on which measuring instrument product information is written is transparent to be read from the outside and has an infrared beam blocking function to block external infrared beams flowing into the interior; a Micom that calculates the consumption quantity of the supply by counting the electrical output signal from the infrared beam sensor to detect the rotational frequency of the digit wheel;and a power supply unit that provides energy required for the light sensor unit and the Micom by using a battery power source, and in particular supplies the infrared emitter with the drive pulse signal;

[0011] US 2003 / 0117088A1 describes an LED lamp device for vehicles, comprising: a light source with a predetermined number of light-emitting diodes connected together or in series; and a power supply with a predetermined voltage to be applied across the predetermined number of light-emitting diodes, the predetermined voltage depending on the predetermined number of light-emitting diodes.

[0012] US 2002 / 0061739A1 describes a wireless mouse unit comprising: a wireless mouse that generates signals for moving a cursor over a display screen; a rechargeable secondary battery cell contained within the wireless mouse; and a receiver for receiving the signals transmitted by the wireless mouse, the receiver being electrically connected to and powered by a computer via a cable, and the receiver including charging ports for recharging the rechargeable secondary battery cell of the wireless mouse.

[0013] JP 2013-131 813 A describes the provision of an analog-to-digital conversion device capable of accurately converting an analog input signal into a digital signal over an entire input voltage range. This is achieved by providing an analog-to-digital conversion device comprising: a voltage generation circuit for generating a reference voltage; a comparator for comparing the potential difference of an analog input voltage with the reference voltage; a sample-and-hold circuit for holding the analog input voltage and subtracting a first preset voltage from the analog input voltage to output a first output voltage when the analog input voltage is higher than the reference voltage, and adding a second preset voltage to the analog input voltage to output a second output voltage when the analog input voltage is lower than the reference voltage.and a conversion circuit for outputting a first digital output signal corresponding to the voltage which is the first output voltage plus the first voltage, or a second digital output signal corresponding to the voltage which is the second output voltage minus the second voltage.

[0014] US 2005 / 0 231 127 A1 describes a charge pump circuit that boosts the voltage of a battery to generate a driver voltage for an LED. A constant current circuit generates a constant current flowing through the LED. A monitoring circuit monitors the cathode potential of the LED, i.e., the voltage across the constant current circuit. A control circuit receives a monitoring result from the monitoring circuit and increases the turns ratio of the charge pump circuit when the voltage across the constant current circuit falls below a minimum voltage that ensures a constant current. The control circuit sets an externally requested constant current value in the constant current circuit. When a change from a high current to a low current is requested, the control circuit resets the turns ratio of the charge pump circuit to 1.0.

[0015] CN 1 03 220 865 A describes a button cell-powered LED driver circuit and a Bluetooth device.The coin cell-powered LED driver circuit comprises a coin cell, an MCU (Microprogrammed Control Unit), an amplifier, a sampling unit, a variety of LED lamps with different turn-off voltages, and LED switching units for switching the LED lamps. The amplifier, sampling unit, and MCU form a closed control loop. The MCU controls the LED switching units via a GPIO (General Purpose Input / Output) interface to control the switching on and off of the corresponding LED lamps. The amplifier unit controls the LED lamps to output a suitable turn-off voltage for the LED lamps according to PWM (Pulse Width Modulation) of a sampled result of the amplifier unit's output voltage, thus ensuring that the switched-on LED lamps operate with a constant voltage state. SUMMARY OF THE INVENTION

[0016] This invention was conceived in view of the above circumstances, and this invention prevents a backflow of electric current to a battery and protects a driver circuit of a light-emitting diode, even when a voltage greater than a supply voltage is applied to a light-emitting diode in a light source of an encoding device.

[0017] This problem is solved according to the invention by the features of the independent claims. Particular embodiments of the invention are the subject of the dependent claims.

[0018] A coding device according to one aspect of this invention comprises a light source, a scale which receives light from the light source, a light receiver which receives light from the scale and outputs a signal corresponding to the received light, and a signal processor which calculates a positional relationship between the light receiver and the scale depending on the signal from the light receiver.The light source contains: a battery; an amplifier circuit which amplifies a supply voltage supplied by the battery and outputs the amplified voltage; a light-emitting element to one end of which the amplified voltage is applied; a driver circuit which is arranged between another end of the light-emitting element and ground, wherein the driver circuit controls or regulates the current flowing through the light-emitting element; a voltage sensing circuit which detects a voltage between the light-emitting element and the driver circuit; and a control or regulating circuit.The control circuit causes the amplifier circuit to amplify the supply voltage when the voltage detected by the voltage sensing circuit is lower than the supply voltage; it stops the amplification by the amplifier circuit when the voltage detected by the voltage sensing circuit equals the supply voltage; and it controls or regulates the driver circuit such that, after the amplified voltage applied to the light-emitting element reaches a certain (preset or preset) value, current flows to the light-emitting element. Thus, when the voltage reaches the supply voltage after a voltage drop across the light-emitting element, the amplification of the voltage applied to the light-emitting element ceases.Thus, after a voltage drop in the light-emitting element, the voltage does not exceed the supply voltage, and therefore the driver circuit can be protected from overvoltage, and a backflow of electrical current to the battery can be prevented.

[0019] According to a particular embodiment, the voltage sensing circuit is preferably configured as an analog-to-digital converter (ADC) in which the voltage is applied between the light-emitting element and the driver circuit, the applied voltage is converted into a digital signal, and the converted digital signal is output to the control circuit. Alternatively, the voltage sensing circuit may include such an ADC, and the control circuit may control or regulate the amplification performed by the amplifier circuit depending on the value of the digital signal. By comparing the output signal of the ADC, the control circuit can therefore detect whether the voltage reaches the supply voltage after a voltage drop across the light-emitting element.

[0020] In particular, the voltage sensing circuit is preferably configured as a comparator that compares the supply voltage applied to one input terminal of the light-emitting element with the voltage applied to another input terminal of the driver circuit and outputs a comparison result to the control circuit; or contains such a comparator; and the control circuit preferably controls or regulates the amplification performed by the amplifier circuit depending on the comparison results. Consequently, the output signal of the comparator is converted, and this allows the control circuit to detect that the voltage reaches the supply voltage after a voltage drop in the light-emitting element.

[0021] According to a further aspect of the invention, the amplifier circuit preferably comprises a first diode, to whose anode the supply voltage is applied; a first capacitor, one end of which is connected to ground; a second diode, the anode of which is connected to a cathode of the first diode, and the cathode of which is connected to a high-voltage end of the light-emitting element and to another end of the first capacitor; and a second capacitor, one end of which is connected to the control circuit, and the other end of which is connected to the cathode of the first diode and to the anode of the second diode. When the supply voltage is amplified by the amplifier circuit, the control circuit preferably applies a pulse signal to the second capacitor. This allows the control signal to be applied as a pulse signal, and the voltage applied to the light-emitting element can be amplified stepwise.

[0022] Furthermore, the capacitance value of the first capacitor is preferably higher than the capacitance value of the second capacitor. This allows the voltage applied to the light-emitting element to be increased stepwise with a slope that is smaller than the supply voltage.

[0023] According to a preferred embodiment, the coding device is preferably equipped with a third capacitor, which is arranged between two ends of the battery, and wherein the capacitance of the third capacitor is preferably higher than the capacitance of the first capacitor and the capacitance of the second capacitor. This prevents fluctuations in the supply voltage during the amplification of the voltage applied to the light-emitting element.

[0024] Furthermore, the driver circuit preferably comprises a switch, a current source, and a first transistor arranged in a cascade connection between the battery and ground; and a second transistor, wherein the voltage between the light-emitting element and the driver circuit is applied to one end of the second transistor, another end is connected to ground, and the second transistor forms a current mirror with the first transistor. The opening and closing of the switch is preferably controlled or regulated by the control circuit. This allows the duration of current flow to the light-emitting element to be controlled or regulated in response to a signal sent to the switch by a control signal.

[0025] Furthermore, the coding device preferably includes a third diode, wherein the voltage between the light-emitting element and the driver circuit is applied to an anode of the third diode, and a cathode is connected between the battery and the switch, the power source, and the first transistor. This prevents an overvoltage from being applied to the driver circuit if the voltage becomes excessively high after a voltage drop in the light-emitting element.

[0026] A light source for a coding device according to another aspect of this invention is a light source of a coding device comprising a scale which receives light, a light receiver which receives light from the scale and outputs a signal corresponding to the received light, and a signal processor which calculates a positional relationship between the light receiver and the scale using the signal from the light receiver, wherein the coding device emits the light at the scale of the coding device.The light source contains: a battery; an amplifier circuit which amplifies a supply voltage supplied by the battery and outputs the amplified voltage; a light-emitting element, to one end of which the amplified voltage is applied; a driver circuit which is arranged between another end of the light-emitting element and an earth, wherein the driver circuit controls or regulates the current flowing through the light-emitting element; a voltage sensing circuit which detects a voltage between the light-emitting element and the driver circuit; and a control or regulating circuit.The control circuit causes the amplifier circuit to amplify the supply voltage when the voltage detected by the voltage sensing circuit is lower than the supply voltage; it stops the amplification by the amplifier circuit when the voltage detected by the voltage sensing circuit equals the supply voltage; and it controls or regulates the driver circuit such that, after the amplified voltage applied to the light-emitting element reaches a certain (preset or preset) value, current flows to the light-emitting element. Thus, when the voltage reaches the supply voltage after a voltage drop across the light-emitting element, the amplification of the voltage applied to the light-emitting element ceases.Thus, after a voltage drop in the light-emitting element, the voltage does not exceed the supply voltage, and therefore the driver circuit can be protected from overvoltage, and a backflow of electrical current to the battery can be prevented.

[0027] According to a particular embodiment, the voltage sensing circuit is preferably configured as an analog-to-digital converter (ADC), wherein the voltage is applied between the light-emitting element and the driver circuit, the applied voltage is converted into a digital signal, and the converted digital signal is output to the control circuit; or the voltage sensing circuit includes such an analog-to-digital converter; and the control circuit controls or regulates the amplification performed by the amplifier circuit depending on a value of the digital signal. By comparing an output signal of the analog-to-digital converter, the control circuit can therefore detect whether the voltage reaches the supply voltage after a voltage drop in the light-emitting element.

[0028] In particular, the voltage sensing circuit is preferably configured as a comparator that compares the supply voltage applied to one input terminal of the light-emitting element with the voltage applied to another input terminal of the driver circuit and outputs a comparison result to the control circuit; or contains such a comparator; and the control circuit preferably controls or regulates the amplification performed by the amplifier circuit depending on the comparison results. Consequently, the output signal of the comparator is converted, and this allows the control circuit to detect that the voltage reaches the supply voltage after a voltage drop in the light-emitting element.

[0029] According to a further aspect of the invention, the amplifier circuit preferably comprises a first diode, to whose anode the supply voltage is applied; a first capacitor, one end of which is connected to ground; a second diode, the anode of which is connected to a cathode of the first diode, and the cathode of which is connected to a high-voltage end of the light-emitting element and to another end of the first capacitor; and a second capacitor, one end of which is connected to the control circuit, and the other end of which is connected to the cathode of the first diode and to the anode of the second diode. When the supply voltage is amplified by the amplifier circuit, the control circuit preferably applies a pulse signal to the second capacitor. This allows the control signal to be applied as a pulse signal, and the voltage applied to the light-emitting element can be amplified stepwise.

[0030] Furthermore, the capacitance value of the first capacitor is preferably higher than the capacitance value of the second capacitor. This allows the voltage applied to the light-emitting element to be increased stepwise with a slope that is smaller than the supply voltage.

[0031] According to a preferred embodiment, the coding device is preferably equipped with a third capacitor, which is arranged between two ends of the battery, and wherein the capacitance of the third capacitor is preferably higher than the capacitance of the first capacitor and the capacitance of the second capacitor. This prevents fluctuations in the supply voltage during the amplification of the voltage applied to the light-emitting element.

[0032] Furthermore, the driver circuit particularly includes a switch, a current source, and a first transistor, which are arranged in a cascade connection between the battery and ground; and a second transistor, wherein the voltage between the light-emitting element and the driver circuit is applied to one end of the second transistor, another end is connected to ground, and the second transistor forms a current mirror with the first transistor. The opening and closing of the switch is preferably controlled or regulated by the control circuit. This allows the time during which current flows to the light-emitting element, in response to a signal sent to the switch, to be controlled or regulated by a control signal.

[0033] Furthermore, the light source preferably includes a third diode, wherein the voltage between the light-emitting element and the driver circuit is applied to an anode of the third diode, and a cathode is connected between the battery and the switch, the power source, and the first transistor. This prevents an overvoltage from being applied to the driver circuit if the voltage becomes excessively high after a voltage drop in the light-emitting element.

[0034] According to another aspect of this invention, a measuring method for measuring a positional relationship, in particular using a light source and / or an encoding device according to any aspect of the invention above or of a particular embodiment thereof, is provided, comprising the following steps: (a) emitting light by means of a light source by means of a battery, an amplifier circuit which amplifies a supply voltage supplied by the battery and outputs the amplified voltage, a light-emitting element to which the amplified voltage is applied at one end, and a driver circuit which is arranged between another end of the light-emitting element and ground, wherein the driver circuit controls or regulates the current flowing through the light-emitting element; (b) detecting a voltage between the light-emitting element and the driver circuit by means of a voltage detection circuit;(c) Controlling or regulating the amplifier circuit by means of a control circuit to amplify the supply voltage when the voltage detected by the voltage sensing circuit is below the supply voltage, which stops the amplification performed by the amplifier circuit when the voltage detected by the voltage sensing circuit is equal to the supply voltage, and which controls or regulates the driver circuit such that, after the amplified voltage applied to the light-emitting element has reached a certain value, current flows to the light-emitting element; (d) illuminating a scale with light from the light source; (e) receiving the light from the scale at a light receiver and outputting a signal corresponding to the received light by the latter; and (f) calculating or determining a positional relationship between the light receiver and the scale as a function of the signal from the light receiver.

[0035] According to the above, the backflow of electric current to a battery can be prevented, and a driver circuit of a light-emitting diode can be protected even if a voltage greater than a supply voltage is applied to the light-emitting diode in a light source of an encoding device.

[0036] This invention is explained by the following detailed description and the accompanying drawings. The accompanying drawings are included only to facilitate understanding and do not limit the scope of this invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] This invention is described in more detail below with reference to the several drawings provided, by means of non-limiting examples of exemplary embodiments of this invention, where the same reference numerals denote similar parts across the different views of the drawings. It should be noted that while embodiments are described separately, individual features thereof can be combined to form additional embodiments. Fig. Figure 1 is a front view which schematically represents a configuration of a dial gauge which includes an optical coding device according to a first embodiment; Fig. 2 is a development plan which schematically represents a configuration of the optical coding device according to the first embodiment; Fig. Figure 3 shows a configuration of a sample absolute scale and signal acquisition device; Fig. Figure 4 schematically shows a configuration of a light source according to the first embodiment; Fig. Figure 5 schematically shows an exemplary configuration of the light source according to the first embodiment; Fig. Figure 6 shows another exemplary configuration of the light source according to the first embodiment; Fig. 7 is a timing diagram which represents operations of the light source according to the first embodiment; and Fig. Figure 8 schematically shows a configuration of a light source according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0038] The details shown here are exemplary and serve solely to illustrate the embodiments of this invention. They are presented to provide what is considered the most useful and easily understandable description of the fundamentals and conceptual aspects of this invention. In this respect, no attempt is made to show structural details of this invention in more detail than is necessary for a basic understanding of it, since the description, in conjunction with the drawings, makes it clear to those skilled in the art how the forms of this invention can be implemented in practice.

[0039] Embodiments of this invention are described below with reference to the drawings. Identical reference numerals are assigned to identical elements in each of the multiple drawings, and repetitive descriptions are omitted where necessary. First embodiment

[0040] An optical coding device according to a first special embodiment is described. Fig. Figure 1 is a front view schematically depicting a configuration of a dial gauge 101, which includes the optical coding device according to the first embodiment. The dial gauge 101 comprises a main body 102, a display 103, an actuating button 104, a shaft 105, a spindle 106, a probe 107 and / or an output 108.

[0041] The main body 102 has, in particular, a substantially rounded column shape, in which the height in the vertical direction of the drawing planes of the Fig. 1 smaller than the width in the horizontal direction of the drawing plane Fig. 1 is. The display 103, which for example shows a measured value, is arranged on a surface of the main body 102.

[0042] The shaft 105 has an essentially cylindrical shape, which is essentially in the vertical direction of the drawing plane. Fig. 1 runs, and is arranged so that it protrudes from an outer section or edge of the main body 102.

[0043] The spindle 106 is, in particular, a substantially cylindrical element, is inserted through the shaft 105 and is held in such a way that it is able to slide along the length of the shaft 105. The probe head 107, which comes into contact with a measuring object, is attached to a tip of the spindle 106 projecting from the shaft 105.

[0044] A displacement detector (not shown in the figures), which detects the displacement of the spindle 106, is arranged inside the main body 102. To detect the displacement, the displacement detector includes an optical encoding device 10 (described below), and using the optical encoding device 10, the displacement of the spindle 106 is detected in a defined cycle and output to the display 103. The display 103 is configured to show measurement results output by the displacement detector.

[0045] The actuating button 104 is used, or can be used, to reset the measurement result displayed on the display 103, to switch a display range, or the like. In this example, three actuating buttons 104 are provided, but the number of actuating buttons 104 is not limited to this.

[0046] Output 108 is configured to allow the connection of an external device and can, for example, output measurement results to the outside.

[0047] The optical coding device 10 according to the first embodiment is described below. In this embodiment, the optical coding device is configured in particular as an optical absolute encoder which uses a dual-modulation scale track pattern (hereinafter referred to as DMST pattern). Fig. Figure 2 is a development plan showing a schematic configuration of the optical coding device 10 according to the first embodiment. As in Fig. As shown in Figure 2, the optical coding device 10 includes a lighting device 20, a scale 21 and a signal detector 23.

[0048] The illumination device 20 and the signal detector 23 are arranged such that they have fixed relative positions. The signal detector 23 and the illumination device 20 are configured such that they are subject to a relative displacement, relative to the scale 21, along a measuring direction (e.g., the X-axis direction). Fig. 2), which is in particular a longitudinal direction of the scale 21, are able to. The scale 21 is equipped with an absolute scale pattern 22, which is used for position detection. When the illumination device 20 emits light at the absolute scale pattern 22, interference light (or an interference pattern which has a light modulation) is generated. By detecting a change in the measuring direction of the interference light, the signal detector 23, in particular its processing circuit 25, can detect a positional relationship between the scale 21 and the signal detector 23.

[0049] The lighting device 20 is configured as a component that illuminates the scale 21 with a visible and / or invisible wavelength. The lighting device 20 includes, for example, a light source 11, a lens 13, and / or a light source grating 14. The light source 11 is configured to emit light of a visible and / or invisible wavelength. The light source 11 is connected to a signal processing circuit 25 described below and, in particular, behaves as a light source that emits light intermittently in a defined cycle. Light 30 emitted by the light source 11 is either partially or completely converted by the lens 13 into parallel light beams, such that a sufficient beam area is available to illuminate a specific (predetermined or predeterminable) area of ​​the scale 21.The light source grating 14 converts the parallel light rays from the lens 13 into a uniform illuminance in the measuring direction, whereupon the parallel light rays reach the scale 21. If the illumination distribution of the parallel light rays from the lens 13 is sufficiently uniform, a lighting device without the light source grating 14 can be used.

[0050] Scale 21 includes, in particular, the absolute scale pattern 22. The absolute scale pattern 22 is formed by an incremental track pattern TINC, an absolute track pattern TABS1, and / or an absolute track pattern TABS2. The DMST pattern mentioned above can be used as the absolute track pattern TABS1 and as the absolute track pattern TABS2.

[0051] The plane of scale 21, on which in particular the absolute scale pattern 22 is formed, is the plane parallel to the X-direction (measuring direction) and Y-direction (perpendicular to the X-direction). Fig. 2 is the measuring direction designated with the reference symbol MA. Furthermore, in Fig. 2 the direction perpendicular to the plane of the scale 21 on which the absolute scale pattern 22 is formed, i.e. to the XY plane, is called the Z direction.

[0052] The signal detector 23 includes, in particular, a detector track 24 and the signal processing circuit 25. The signal detector 23 can, for example, be configured as a single CMOS circuit. The detector track 24 includes one or more, for example, three detector tracks DINC, DABS1, and DABS2. The detector tracks DINC, DABS1, and DABS2 are arranged such that they receive patterned light from the incremental track pattern TINC, the absolute track pattern TABS1, and / or the absolute track pattern TABS2, respectively. The signal processing circuit 25 is configured as a circuit that processes a signal indicating the detection results of the detector track 24.

[0053] As mentioned above, the light emitted by the light source 11 is converted into parallel light rays by the lens 13. Fig. Figure 1 schematically represents one or more, e.g., three, beam paths 31, 32, and 33 of the light 30. Beam path 31 is, in particular, a representative central beam path containing light that illuminates the incremental track pattern TINC. Beam paths 32 and 33 are representative beam paths containing light that illuminates the absolute track patterns TABS2 and TABS1, respectively.

[0054] When the light source grating 14 is used, it has a grating structure containing openings where the light is arranged around the representative beam path 31 at intervals corresponding to the incremental track pattern TINC or at intervals largely corresponding to the wavelength. The parallel light rays from the lens 13 pass through the grating structure of the light source grating 14 and strike the incremental track pattern TINC according to the principle known as the self-imaging illumination principle.

[0055] When the incremental track pattern TINC is illuminated, a spatially modulated light pattern (for example, light in an interference fring for the multitude of diffracted light) is output to the detector track DINC of signal detector 23. If the track has a track wavelength of approximately 8 µm or less, the incremental track pattern TINC is configured so that the multitude of diffracted light (for example, ±1-dimensional diffracted light) produces an interference fring on the detector track DINC. If the track has a track wavelength of approximately 8 to 40 µm, the incremental track pattern TINC is configured so that the different diffracted beams interact and produce a self-image (for example, a Talbot image or a Fresnel image) on the plane of the detector track DINC.

[0056] The absolute track patterns TABS2 and TABS1 are configured to generate an image (for example, a blurred or a clear image) that is projected onto the detector tracks DABS2 and DABS1, respectively. When the absolute track pattern TABS1 is illuminated, a spatially modulated light pattern (for example, patterned light corresponding to the absolute track pattern TABS1) is output to the detector track DABS1 of signal detector 23. When the absolute track pattern TABS2 is illuminated, a spatially modulated light pattern (for example, patterned light corresponding to the absolute track pattern TABS2) is output to the detector track DABS2 of signal detector 23.

[0057] The spatially modulated light pattern shifts along with the scale 21. To obtain a desired detection signal with the detector track(s) (in particular each of the detector tracks) DINC, DABS1, and DABS2, one or more, in particular a plurality, of light detector areas are arranged, for example, such that the spatially modulated light pattern can be spatially filtered and detected. The many detector areas can be configured by arranging the plurality of light detectors in the measurement direction, or can be generated by causing light to pass through a spatial filter mask, which has a plurality of openings in the measurement direction, and strike a light detector that has a large surface area.

[0058] The in Fig. The configuration of the track pattern shown in Figure 2 is purely exemplary, and as long as the pattern can be detected by the detector track, other configurations and arrangements can of course be used.

[0059] A more detailed description of the absolute scale pattern 22 and the signal detector 23 follows. Fig. Figure 3 shows the configurations of the absolute scale pattern 22 and the signal detector 23. For the sake of simplicity, in Fig. 3 the signal detector 23 and the absolute scale pattern 22 are shown side by side, with the XY plane being viewed along the Z direction.

[0060] In Fig. 3 is the spatial wavelength of the absolute track pattern TABS1 L1, and the spatial wavelength of the absolute track pattern TABS2 is L2. The absolute track patterns TABS1 and TABS2 are equipped with a pattern that is transparent to (reflects) a light pattern that is spatially modulated with respect to intensity. This pattern is configured such that its width in the Y-direction (cross-sectional dimension) changes as a function of its position along the measurement direction (MA) X-direction.

[0061] Each of the detector tracks DINC, DABS1, and DABS2 has one or more, in particular a plurality, of light detectors, which are arranged, for example, to form a quadrature detector. In this example, each of the detector tracks has four adjacent detector elements, which are arranged at equal intervals, such that a spatial filter is generated which detects a plurality (e.g., four) spatial phases (in particular, 0°, 90°, 180°, and 270°) of the received spatially modulated light pattern. A plurality of groups of (e.g., four) adjacent detector elements, which are arranged in this way, are provided, and, as in Fig. As shown in Figure 3, signals from the multitude of groups, each assigned a spatial phase, are summed. The summed signals are indicated using four symbols: A(0°), B(90°), A-(180°), and B-(270°). Specifically, the four quadrature signals corresponding to detector track DINC are designated as signals Ainc, Binc-A-inc, and B-inc. Similarly, the four quadrature signals of detector track DABS1 are designated as signals Aabs1, Babs1, A-abs1, and B-abs1, and the four quadrature signals of detector track DABS2 are designated as signals Aabs2, Babs2, A-abs2, and B-abs2.

[0062] The quadrature signals are processed to determine a spatial phase position of each track within a current local wavelength of the corresponding scale track. If at least one of the absolute track patterns TABS1 and TABS2 is a DMST pattern containing a characteristic curve that conveys a spatially modulated light pattern containing an intensity modulation component, signals are generated that correspond to the four spatial phases (i.e., 0°, 90°, 180°, and 270°) of the intensity modulation component.

[0063] For example, by performing signal processing similar to that specified in US patent US 8 309 906 B2, which is included here by cross-reference, on the quadrature signals derived from the absolute track pattern TABS1 (wavelength L1) and the absolute track pattern TABS2 (wavelength L2), a position signal of the composite wavelength can be obtained which oscillates periodically through a composite wavelength S. S=L1×L2 / |L1−L2|

[0064] Similarly to the specification of US patent US 8,309,906 B2, a broad-range position signal can be obtained, exhibiting a fluctuation with a longer periodicity than, or smoother than, the composite wavelength S. By combining this broad-range position signal with the composite wavelength signal, an absolute position can be measured precisely.

[0065] In one example, the overall width of the absolute scale pattern 22 may be set to approximately 3.0 mm or less. The wavelength L2 of the absolute track pattern TABS2 may be set to L2 = 720 µm, and the wavelength L1 of the absolute track pattern TABS1 may be set to L1 = 700 µm. The wavelength of the incremental track pattern TINC may be set to 20 µm. According to the specification of US Patent US 8,309,906 B2, a composite wavelength of approximately 25.2 mm can thus be produced. The configurations and dimensions given in the foregoing case are purely exemplary, and this invention is not limited to them.

[0066] The following is a description of the light source 11 according to a first special embodiment. Fig. Figure 4 schematically shows a configuration of the light source 11 according to the first embodiment. As in Fig. As shown in Figure 4, the light source 11 according to the first embodiment includes a battery 1, a control circuit 2, an amplifier circuit 3, a light-emitting diode 4, a driver circuit 5 and / or a voltage sensing circuit 6.

[0067] Battery 1 is specifically a primary battery, for which, for example, a button cell with a nominal voltage of 3 V can be used. In this example, "a button cell" refers to a primary battery with a disc-like shape and can, for example, refer to a graphite fluoride lithium battery, a manganese dioxide lithium battery, a copper oxide lithium battery, an alkaline battery, a mercury battery, a zinc air battery, a silver oxide battery, and the like.

[0068] Control circuit 2 controls or regulates the operations of amplifier circuit 3 and / or driver circuit 5 based on a voltage sensing result obtained by voltage sensing circuit 6. In this example, control circuit 2 controls or regulates amplifier circuit 3 with a control signal S1 and controls or regulates driver circuit 5 with a control signal S2.

[0069] The amplifier circuit 3 amplifies a voltage VB, which is applied to an anode of the light-emitting diode 4, to a specific (predetermined or predeterminable) voltage.

[0070] The light-emitting diode 4 has an anode connected to an output of the amplifier circuit 3 and a cathode connected to the driver circuit 5. In this example, a light-emitting diode is used as the light-emitting element, but the invention is not limited to this example. More precisely, other types of elements, such as a semiconductor laser, a self-scanning light-emitting device (SLED), and / or an organic light-emitting diode (OLED), can likewise be used as or be included as the light-emitting element.

[0071] The driver circuit 5 controls the light-emitting diode 4, in particular by controlling or regulating the current flowing to the light-emitting diode 4.

[0072] The voltage sensing circuit 6 specifically detects a voltage VC at the cathode of the light-emitting diode 4. In other words, the voltage sensing circuit 6 detects the voltage VC that is supplied from the cathode of the light-emitting diode 4 to the driver circuit 5, or detects the voltage VC at a node between the cathode of the light-emitting diode 4 and the driver circuit 5. The voltage sensing circuit 6 then outputs the detection results of the detected voltage VC as a detection signal DET to the control circuit 2.

[0073] The following is a description of the specific configuration of the voltage sensing circuit 6. Fig. Figure 5 shows an exemplary configuration of the light source 11 according to the first embodiment. As in Fig. As shown in Figure 5, the voltage sensing circuit 6 is configured as an analog-to-digital converter (ADC), which is an analog-to-digital conversion device that receives electrical energy from the battery 1. In this case, the ADC 7 converts the voltage VC (analog input signal) into the sensing signal DET (digital signal) and outputs the signal to the control circuit 2. By comparing the value of the sensing signal DET, the control circuit 2 can determine whether the voltage VC has reached a supply voltage VDD.

[0074] The specific configuration of the voltage detection circuit 6 is described below. Fig. Figure 6 shows another exemplary configuration of the light source 11 according to the first embodiment. As in Fig. As shown in Figure 6, the voltage sensing circuit 6 can alternatively be configured as a comparator 8, which compares the supply voltage VDD and the voltage VC. In this example, the supply voltage VDD is applied to a non-inverting input terminal of the comparator 8, and the voltage VC is applied to an inverting input terminal. When the voltage VC reaches the supply voltage VDD, a voltage level of the sensing signal DET output by the comparator transitions from HIGH to LOW. Consequently, the control circuit 2 can determine whether the voltage VC has reached the supply voltage VDD by comparing the voltage of the sensing signal DET.

[0075] As described above, for example, with a button cell, while the nominal voltage is typically 3 V and the actual output voltage is 1.5 to 2.7 V, the forward voltage of the light-emitting diode is approximately 1.6 to 4 V. Given this, in this configuration, the supply voltage VDD is amplified by the amplifier circuit 3, and the forward voltage of the light-emitting diode 4 is ensured. However, if the voltage after amplification is too high, a voltage exceeding the test voltage can be applied to the circuit elements that make up the light source 11 (e.g., the driver circuit 5), which can lead to a fault in the circuit. Furthermore, a voltage greater than the output voltage of battery 1 can be generated in the light source 11, which can cause a backflow of electrical current to battery 1 (the primary battery).

[0076] Consequently, in this configuration, the supply voltage VDD is used as a reference voltage, which is compared to the voltage VC in the voltage sensing circuit 6. Therefore, when the voltage sensing circuit 6 detects that the voltage VC has reached the supply voltage VDD, any increase in the voltage VC can be limited by the control circuit 2 stopping the voltage amplification performed by the amplifier circuit 3. This prevents a voltage exceeding the test voltage from being applied to the driver circuit 5. Furthermore, no voltage greater than the supply voltage VDD is applied to the driver circuit 5, thus preventing a backflow of electrical current to the battery 1 and avoiding damage to the battery 1.

[0077] Amplifier circuit 3 is described in more detail below. As in the Fig. 5 and Fig. As shown in Figure 6, the amplifier circuit 3 includes in particular an inverter INV, a diode D1 (also referred to as a first diode) and a diode D2 (also referred to as a second diode), as well as a capacitor C1 (also referred to as a first capacitor) and a capacitor C2 (also referred to as a second capacitor).

[0078] An anode of diode D1 is connected to a high-voltage terminal of battery 1, and the supply voltage VDD is applied to it. A cathode of diode D1 is connected to an anode of diode D2. The inverter INV outputs a signal that is the inverse of the control signal S1 output by control circuit 2. Capacitor C2 is connected between the output of inverter INV and the cathode of diode D1 and the anode of diode D2. A cathode of diode D2 is connected to an anode of light-emitting diode 4. Additionally, capacitor C1 is connected between the cathode of diode D2 and ground.

[0079] To achieve precise amplification, the capacitance of capacitor C2 is preferably lower than that of capacitor C1 at amplifier voltage 3. For example, the capacitance of capacitor C2 is preferably approximately 1 / 10 of the capacitance of capacitor C1. In this case, for example, the capacitance of capacitor C1 is assumed to be approximately 1.0 µF, and the capacitance of capacitor C2 is assumed to be approximately 0.1 µF.

[0080] The driver circuit 5 is described in more detail below. Fig. 5 and Fig. Figure 6 shows circuit diagrams that schematically represent exemplary configurations of the driver circuit 5. The driver circuit 5 includes, in particular, a switch SW, a current source CS, and NMOS transistors MN1 and MN2.

[0081] The switch SW, the current source CS, and / or the NMOS transistor MN1 are arranged in a cascade circuit between the supply voltage VDD and ground. Specifically, the supply voltage VDD is applied to one end of the switch SW. The current source CS is inserted between the other end of the switch SW and a drain electrode of the NMOS transistor MN1. A source electrode of the NMOS transistor MN1 is connected to ground. The opening and closing of the switch SW is controlled by the control signal S2 from the control circuit 2.

[0082] A drain electrode of the NMOS transistor MN2 is connected to the cathode of the light-emitting diode 4. A source electrode of the NMOS transistor MN2 is connected to ground.

[0083] In this configuration, the NMOS transistors MN1 and MN2 form a current mirror. Specifically, a gate of NMOS transistor MN1 and a gate of NMOS transistor MN2 are connected to the drain electrode of NMOS transistor MN1. Consequently, the current flowing to NMOS transistor MN1 is mirrored in a specific (predefined or predeterminable) ratio, and the mirrored current flows to NMOS transistor MN2. If NMOS transistors MN1 and MN2 are transistors with identical specifications, the current flowing to NMOS transistor MN2 will be equal to the current flowing to NMOS transistor MN1.

[0084] In this example, the voltage sensing circuit 6 detects the voltage between the light-emitting diode 4 and the drain electrode of the NMOS transistor MN2.

[0085] The following describes the operations of light source 11. Fig. Figure 7 is a timing diagram illustrating the operations of the light source 11 according to the first embodiment. Initially, the control signal S2 is LOW, and the switch SW is open. Therefore, no current I flows to the light-emitting diode 4, and the light-emitting diode 4 does not emit light. In this state, the control circuit 2 outputs a pulse signal as the control signal S1. At this point, each time the inverter INV is sent HIGH to capacitor C2, capacitor C2 is charged, and the charge on capacitor C1 increases accordingly. The control signal S1 is specifically a pulse signal, and therefore, each time a pulse is sent to capacitor C2, the charge on capacitor C1 increases incrementally. Consequently, the voltage VB across the anode of the light-emitting diode 4 also increases accordingly.

[0086] Here, an example is described where the supply voltage VDD is 2.5 V, and the amplifier circuit 3 can amplify the supply voltage to approximately twice that value. If the voltage drop across diodes D1 and D2 is estimated at 0.4 V, the voltage VB can be amplified to up to 2 x VDD - 0.4 = 4.6 V. If the voltage drop across the light-emitting diode 4 is assumed to be between 1.6 and 4.0 V, the voltage VC in this example is likely to be in the range of 0.6 to 3 V, as described above. That is, due to the value of the voltage VB and the voltage drop across the light-emitting diode 4, the voltage VC can exceed the supply voltage VDD (2.5 V), or a situation can arise where the voltage is amplified to the test voltage of the driver circuit 5.

[0087] In this configuration, the voltage sensing circuit 6 monitors or checks the cathode voltage VC of the light-emitting diode 4 during the operations described above. Specifically, the voltage sensing circuit 6 detects whether the cathode voltage VC of the light-emitting diode 4 exceeds the supply voltage VDD. When the voltage VC has substantially reached the supply voltage VDD, the voltage sensing circuit 6 informs the control circuit 2 using the sensing signal DET. In response to the sensing signal DET, the control circuit 2 stops the output of the control signal S1 and halts the amplification of the voltage VB at the moment the voltage VC reaches the supply voltage VDD.

[0088] At this point, the voltage VB becomes considerably higher than the supply voltage VDD, and the control circuit 2 changes the level of the control signal S2 from LOW to HIGH and closes the switch SW. This causes current to flow to the light-emitting diode 4, and the light-emitting diode 4 emits light. As current flows to the light-emitting diode 4, the amplified amount of charge that has been charged onto the capacitor C1 decreases, and therefore the voltage VB across the anode of the light-emitting diode 4 drops.

[0089] After a certain (predetermined or predeterminable) time interval, the control circuit 2 changes the level of the control signal S2 from HIGH to LOW and opens the switch SW. Consequently, the current flowing to the light-emitting diode 4 is interrupted, and the light-emitting diode 4 no longer emits light.

[0090] In the above description, the control circuit 2 switches the level of the control signal S2 as required and / or controls the light-emitting diode 4 while maintaining the voltage VB within a certain (predetermined or predeterminable) range, and thereby the control circuit 2 can cause the light-emitting diode 4 to emit light in a substantially stable manner.

[0091] By repeatedly outputting the pulsed control signal S1, pausing, and switching to the control signal S2, the control circuit 2 can then cause the light-emitting diode 4 to emit light intermittently.

[0092] The preceding description makes it clear that this configuration prevents the voltage VC from exceeding the supply voltage VDD. Consequently, it prevents a voltage exceeding the test voltage from being applied to the driver circuit and prevents backflow of electrical current to battery 1.

[0093] Furthermore, as mentioned above, the voltage sensing circuit 6 can be configured using a standard ADC or comparator and can therefore be implemented on the same chip as other circuits, such as the driver circuit 5. Thus, the voltage sensing circuit 6 can be provided without the need to manufacture a special chip or similar component and can be implemented at a low cost. Since the voltage sensing circuit 6 can be placed on the same chip as other circuits, the size of the coding device can also be reduced, which is advantageous. Second embodiment

[0094] The following is a description of a light source 12 according to a second special embodiment. Fig.Figure 8 schematically shows a configuration of the light source 12 according to the second embodiment. In particular, the light source 12 has a configuration in which a capacitor C3 (also referred to as a third capacitor) and a diode D3 (also referred to as a third diode) are added to the light source 11 according to the first embodiment.

[0095] Capacitor C3 is connected to the high-voltage terminal of battery 1, and one end is connected to ground. In this example, the capacitance of capacitor C3 is preferably chosen to be higher than the capacitances of capacitors C1 and C2. For example, the capacitance of capacitor C1 can be approximately 1.0 µF, the capacitance of capacitor C2 can be approximately 0.1 µF, and the capacitance of capacitor C3 can be approximately 10 µF.

[0096] Increasing the capacitance of capacitor C3 in this way prevents fluctuations in the supply voltage VDD during the amplification process. This helps to stabilize the operation of the light source 12, which is beneficial.

[0097] Specifically, one anode of diode D3 is connected to the cathode of light-emitting diode 4. In other words, the anode of diode D3 can be connected to the drain electrode of the NMOS transistor MN2 of driver circuit 5, or it can be connected to a junction between the cathode of light-emitting diode 4 and the drain electrode of the NMOS transistor MN2 of driver circuit 5. One cathode of diode D3 is connected to a junction between battery 1 (supply voltage VDD) and switch SW of driver circuit 5.

[0098] If the voltage VC rises for any reason, this embodiment prevents the increase by supplying current that flows through diode D3. Since the voltage sensing circuit 6 monitors the voltage VC in the light source 12, diode D3 is provided to support this operation. Even when current flows to diode D3, the voltage sensing circuit 6 continues to monitor the voltage VC. Consequently, a voltage greater than the supply voltage VDD can be prevented from being applied to battery 1 via diode D3. Thus, the reverse flow of electrical current to battery 1 (the primary battery) can be prevented, and battery 1 can be protected. Other embodiments

[0099] Furthermore, this invention is not limited to the embodiments described above and can be modified as needed without deviating from the scope of this invention. For example, the driver circuit 5 and the voltage sensing circuit 6 can have other suitable configurations.

[0100] In the above embodiments, the driver circuit is configured using NMOS transistors, but it can optionally be configured using a PMOS transistor instead. Furthermore, the transistors used are not limited to MOS transistors, and another type of transistor can be used instead.

[0101] As described above, an encoding device is provided, which includes a light source. An amplifier circuit amplifies a supply voltage provided by a battery and outputs the amplified voltage. This voltage is applied to one end of a light-emitting diode. A driver circuit is inserted between the other end of the light-emitting diode and ground, controlling or regulating the current flowing through the light-emitting diode. A voltage sensing circuit detects a voltage between the light-emitting diode and the driver circuit.A control circuit causes the amplifier circuit to amplify the supply voltage when the voltage is lower than the supply voltage, stops the amplification performed by the amplifier circuit when the voltage equals the supply voltage, and controls or regulates the driver circuit so that current flows to the light-emitting diode after the voltage has reached a certain (predetermined or predeterminable) value.

[0102] It should be noted that the preceding examples are given purely for illustrative purposes and are in no way intended to limit this invention. While this invention has been described with reference to exemplary embodiments, it is understood that the words used here are to be understood as descriptive and illustrative, not as limiting. Modifications within the scope of the appended claims, as currently stated and as amended, are possible without altering the scope and concept of this invention in any aspect.Although this invention has been described here with reference to specific structures, materials and embodiments, this invention is not intended to be limited to the details disclosed herein; rather, this invention extends to all functionally equivalent structures, methods and applications as they fall within the scope of the attached claims.

[0103] This invention is not limited to the embodiments described above, and various changes and modifications may be possible without deviating from the scope of this invention.

Claims

[1] Coding device (10), comprising: a light source (11), comprising: a battery (1); an amplifier circuit (3) which amplifies a supply voltage output by the battery (1) and which outputs the amplified voltage; a light-emitting element (4) at one end of which the increased voltage is applied; a driver circuit (5) which is inserted between another end of the light-emitting element (4) and an earth, wherein the driver circuit (5) controls or regulates the current flowing through the light-emitting element (4); a voltage sensing circuit (6) which detects a voltage between the light-emitting element (4) and the driver circuit (5); and a control circuit (2) which controls or regulates the amplifier circuit (3) to amplify the supply voltage when the voltage detected by the voltage sensing circuit (6) is lower than the supply voltage, which stops the amplification carried out by the amplifier circuit (3) when the voltage detected by the voltage sensing circuit (6) is equal to the supply voltage, and which controls or regulates the driver circuit (5) so that, after the amplified voltage supplied to the light-emitting element (4) has reached a certain value, current flows to the light-emitting element (4); a scale (21) which receives light from the light source (11); a light receiver (23) which receives the light from the scale (21) and which outputs a signal corresponding to the received light; and a signal processing device (25) which calculates a positional relationship between the light receiver (23) and the scale (21) according to the signal from the light receiver (23); wherein the amplifier circuit (3) comprises: a first diode (D1), to whose anode the supply voltage is applied; a first capacitor (C1), one end of which is connected to the earth; a second diode (D2) whose anode is connected to a cathode of the first diode (D1), and whose cathode is connected to a high-voltage end of the light-emitting element (4) and to another end of the first capacitor (C1); a second capacitor (C2), one end of which is connected to the control circuit (2), and the other end of which is connected to the cathode of the first diode (D1) and to the anode of the second diode (D2), wherein, when the supply voltage is amplified by the amplifier circuit (3), the control circuit (2) supplies a pulse signal to the second capacitor (C2), wherein the capacitance value of the first capacitor (C1) is preferably higher than the capacitance value of the second capacitor (C2). [2] Coding device according to claim 1, wherein: the voltage sensing circuit (6) includes an analog / digital converter to which the voltage between the light-emitting element (4) and the driver circuit (5) is supplied, the input voltage is converted into a digital signal, the converted digital signal is output to the control circuit (2), and the control circuit (2) controls or regulates the amplification carried out by the amplifier circuit (3) according to a value of the digital signal. [3] Coding device according to claim 1, wherein: the voltage detection circuit (6) comprises a comparison device which, between the light-emitting element (4) and the driver circuit (5), compares the supply voltage applied to one input terminal with the voltage applied to another input terminal and which outputs a comparison result to the control circuit (2), and the control circuit (2) controls or regulates the amplification carried out by the amplifier circuit (3) according to the comparison results. [4] Coding device according to one of the preceding claims, further comprising a third capacitor which is inserted between two ends of the battery (1), wherein the capacitance value of the third capacitor is higher than the capacitance value of the first capacitor (C1) and the capacitance value of the second capacitor (C2). [5] Coding device according to any of the preceding claims, wherein the driver circuit (5) comprises: a switch (SW), a power source (CS) and a first transistor (MN1), which are arranged in a cascade connection between the battery (1) and earth; and a second transistor (MN2), wherein the voltage between the light-emitting element (4) and the driver circuit (5) is applied to one end of the second transistor (MN2), another end is connected to ground, and the second transistor (MN2) forms a current mirror with the first transistor (MN1), wherein the control circuit (2) controls or regulates the opening and closing of the switch (SW); wherein the coding device preferably further comprises a third diode (D3), wherein the voltage between the light-emitting element (4) and the driver circuit (5) is applied to an anode of the third diode (D3) and a cathode is connected between the battery and the switch (SW), the power source (CS) and the first transistor (MN1). [6] Light source (11) for a coding device comprising a scale (21) receiving light, a light receiver (23) receiving the light from the scale (21) and outputting a signal corresponding to the received light, and a signal processing device (25) calculating a positional relationship between the light receiver (23) and the scale (21) according to the signal from the light receiver (23), wherein the coding device emits the light at the scale (21) of the coding device, wherein the light source (11) comprises: a battery (1); an amplifier circuit (3) which amplifies a supply voltage output by the battery (1) and which outputs the amplified voltage; a light-emitting element (4) at one end of which the increased voltage is applied; a driver circuit (5) which is inserted between another end of the light-emitting element (4) and an earth, wherein the driver circuit (5) controls or regulates the current flowing through the light-emitting element (4); a voltage sensing circuit (6) which detects a voltage between the light-emitting element (4) and the driver circuit (5); and a control circuit (2) which controls or regulates the amplifier circuit (3) to amplify the supply voltage when the voltage detected by the voltage sensing circuit (6) is lower than the supply voltage, which stops the amplification performed by the amplifier circuit (3) when the voltage detected by the voltage sensing circuit (6) equals the supply voltage, and which controls or regulates the driver circuit (5) such that, after the amplified voltage supplied to the light-emitting element (4) has reached a certain value, current flows to the light-emitting element (4); wherein the amplifier circuit (3) comprises: a first diode (D1), to whose anode the supply voltage is applied; a first capacitor (C1), one end of which is connected to the earth; a second diode (D2) whose anode is connected to a cathode of the first diode (D1), and whose cathode is connected to a high-voltage end of the light-emitting element (4) and to another end of the first capacitor (C1); a second capacitor (C2), one end of which is connected to the control circuit (2), and the other end of which is connected to the cathode of the first diode (D1) and to the anode of the second diode (D2), wherein, when the supply voltage is amplified by the amplifier circuit (3), the control circuit (2) supplies a pulse signal to the second capacitor (C2), wherein the capacitance value of the first capacitor (C1) is preferably higher than the capacitance value of the second capacitor (C2). [7] Light source for the coding device according to claim 6, wherein the voltage sensing circuit (6) includes an analog / digital converter to which the voltage between the light-emitting element (4) and the driver circuit (5) is supplied, the input voltage is converted into a digital signal, and the converted digital signal is output to the control circuit (2), and the control circuit (2) controls or regulates the amplification carried out by the amplifier circuit (3) according to a value of the digital signal. [8] Light source for the coding device according to claim 6 or 7, wherein the voltage detection circuit (6) includes a comparator which, between the light-emitting element (4) and the driver circuit (5), compares the supply voltage applied to one input terminal with the voltage applied to another input terminal and outputs a comparison result to the control circuit (2), and the control circuit (2) controls or regulates the amplification carried out by the amplifier circuit (3) according to the comparison results. [9] Light source for the coding device according to any one of the preceding claims 6 to 8, wherein the light source further preferably comprises a third capacitor (C3) which is inserted between two ends of the battery (1), wherein the capacitance value of the third capacitor is higher than the capacitance value of the first capacitor (C1) and the capacitance value of the second capacitor (C2). [10] Light source for the coding device according to any one of the preceding claims 6 to 9, wherein the driver circuit (5) comprises: a switch (SW), a power source (CS) and a first transistor (MN1), which are arranged in a cascade connection between the battery (1) and earth; and a second transistor (MN2), wherein the voltage between the light-emitting element (4) and the driver circuit (5) is applied to one end of the second transistor (MN2), another end is connected to ground, and the second transistor (MN2) forms a current mirror with the first transistor (MN1), wherein the control circuit (2) controls or regulates the opening and closing of the switch (SW); wherein the light source preferably further comprises a third diode (D3), wherein the voltage between the light-emitting element (4) and the driver circuit (5) is applied to an anode of the third diode (D3) and a cathode is connected between the battery and the switch (SW), the power source (CS) and the first transistor (MN1). [11] Measurement method for measuring a positional relationship, comprising the following steps: Emitting light by means of a light source (11) through a battery (1), an amplifier circuit (3) which amplifies a supply voltage output by the battery (1) and which outputs the amplified voltage, a light-emitting element (4) to which the amplified voltage is applied, and a driver circuit (5) which is inserted between another end of the light-emitting element (4) and an earth, wherein the driver circuit (5) controls or regulates the current flowing through the light-emitting element (4); Detection of a voltage between the light-emitting element (4) and the driver circuit (5) by means of a voltage detection circuit (6); Controlling or regulating the amplifier circuit (3) by means of a control circuit (2) to amplify the supply voltage when the voltage detected by the voltage sensing circuit (6) is lower than the supply voltage, which stops the amplification carried out by the amplifier circuit (3) when the voltage detected by the voltage sensing circuit (6) is equal to the supply voltage, and which controls or regulates the driver circuit (5) so that, after the amplified voltage supplied to the light-emitting element (4) has reached a certain value, current flows to the light-emitting element (4); Illuminating a scale (21) with light from the light source (11); Receiving the light from the scale (21) at a light receiver (23) and outputting a signal corresponding to the received light by the latter; and Calculating a positional relationship between the light receiver (23) and the scale (21) according to the signal from the light receiver (23); wherein the amplifier circuit (3) comprises: a first diode (D1), to whose anode the supply voltage is applied; a first capacitor (C1), one end of which is connected to the earth; a second diode (D2) whose anode is connected to a cathode of the first diode (D1), and whose cathode is connected to a high-voltage end of the light-emitting element (4) and to another end of the first capacitor (C1); a second capacitor (C2), one end of which is connected to the control circuit (2), and the other end of which is connected to the cathode of the first diode (D1) and to the anode of the second diode (D2), wherein, when the supply voltage is amplified by the amplifier circuit (3), the control circuit (2) supplies a pulse signal to the second capacitor (C2), wherein the capacitance value of the first capacitor (C1) is preferably higher than the capacitance value of the second capacitor (C2).

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