OPTICAL DISTANCE SENSOR

Abstract

[Task] To provide an optical distance measurement sensor that has a large dynamic range and can be used stably even when the ambient temperature changes. [Solution] An optical distance measuring sensor 101 comprises: a charge accumulation unit 42 configured to accumulate charge to generate a pulse current to be supplied to a light-emitting element 45; a setting unit 21 configured to set a target sensitivity of the optical distance measuring sensor; a pulse current controller 20 configured to generate the pulse current synchronously with a repeating signal and to pulse-drive the light-emitting element, the pulse current controller 20 being configured to adjust the pulse current based on the target sensitivity; a light-receiving element 53 configured to receive the reflected light; a first temperature sensor 33; and a non-volatile memory 32 in which characteristic data of the individual light-receiving element are stored.a light receiving element controller 24, configured to set a multiplication factor of the light receiving element based on a temperature measured by the first temperature sensor, the characteristic data and the target sensitivity; and a calculation unit 25, configured to calculate a time from the time light is emitted to an object until the time reflected light is received, based on an output signal repeatedly received from the light receiving element in which the multiplication factor has been set.

Description

[0001] This application claims priority from Japanese patent application No. 2024-120761, which was filed on July 26, 2024. The entire contents of the aforementioned application are hereby incorporated by reference. TECHNICAL AREA

[0002] The present invention relates to an optical distance measuring sensor. STATE OF THE ART

[0003] There is a photoelectric sensor that detects a workpiece by measuring the propagation time of light (for example, patent document 1). In the photoelectric sensor of patent document 1, detection light is repeatedly generated by a light-emitting element. A light-receiving element receives reflected light from the detection light and generates a light-receiving signal indicating the amount of light received. The light-receiving signal is binaryized and fed into a delay line in which a large number of delay circuits are connected in series to delay a logic signal of one bit for a fixed time. A branch point is provided between the delay circuits, and the output of each delay circuit is fed into a large number of storage elements as binary light-receiving signals after distribution.Thus, waveform data indicating temporal changes in the binary light reception signal are generated in the large number of storage elements. Two or more waveform data sets are integrated by adjusting the light emission timing of the light-emitting element, and the presence of a workpiece is determined based on the integrated waveform data. CITATION LIST PATENT LITERATURE

[0004] Patent Document 1: JP 2015-75453 A SUMMARY OF THE INVENTIONAL ENGINEERING TASK

[0005] In the photoelectric sensor of patent document 1, the presence of the workpiece is determined based on the integrated waveform data, but if the reflectance of the workpiece is low, the sensitivity is insufficient, and it is difficult to detect the workpiece stably.

[0006] Furthermore, when the photoelectric sensor is used as a sensor for factory automation (FA), it is essential that the sensor operates stably even at higher ambient temperatures than general electrical equipment. Additionally, a light-receiving element with amplification can be used to improve sensitivity; however, such an element exhibits poor temperature characteristics when the amplification factor is high. Therefore, in cases where stabilizing sensitivity over a wide temperature range is necessary, the amplification factor is suppressed during operation.

[0007] Furthermore, the photoelectric sensor can be used not only to detect workpieces with low reflectance, but also with workpieces that have high reflectance. In such cases, since detection becomes difficult if the sensitivity is set too high, a function is required that can flexibly adjust the sensitivity according to the properties of the object being detected.

[0008] Thus, one objective of the present disclosure is to provide an optical distance measurement sensor that has a large dynamic range and can be used stably even when the ambient temperature changes. SOLUTION TO THE TASK

[0009] An optical distance measuring sensor according to one aspect of the present invention is an optical distance measuring sensor for estimating a distance to an object by measuring the time from the moment light is emitted to the object until the moment reflected light is received, and the sensor comprises: a charge accumulation unit configured to accumulate charge to generate a pulsed current to be supplied to a light-emitting element; an adjustment unit configured to set a target sensitivity of the optical distance measuring sensor; a pulse current controller configured to generate the pulsed current synchronously with a repeating signal and to pulse-drive the light-emitting element, the pulse current controller being configured to adjust the pulsed current based on the target sensitivity; a light-receiving element configured to receive the reflected light;a first temperature sensor; a non-volatile memory in which characteristic data of the individual light-receiving element are stored; a light-receiving element controller configured to set a multiplication factor of the light-receiving element based on a temperature measured by the first temperature sensor, the characteristic data, and the target sensitivity; and a computing unit configured to calculate the time based on an output signal repeatedly received from the light-receiving element in which the multiplication factor has been set.

[0010] As described above, with the configuration in which charge is accumulated in the charge accumulation unit as the energy source for generating the pulsed current, it is possible to generate a high-intensity pulsed current based on the accumulated energy. Furthermore, with the configuration in which the pulsed current is generated synchronously with a repeating signal and the light-emitting element is pulse-controlled, the time width of a projected light pulse can be narrowed, and the peak power can be increased while maintaining the average power, thus increasing sensitivity. Additionally, with the configuration in which the pulsed current is adjusted based on the target sensitivity, not only can a high-intensity projected light pulse be emitted to the object, but also a low-intensity projected light pulse.On the light-receiving side, by configuring the multiplication factor of the light-receiving element based on the temperature measured by the first temperature sensor, the characteristic data of the individual light-receiving element, and the target sensitivity, it is possible to implement control that is optimized for the properties of the light-receiving element and the ambient temperature. Thus, each individual element can be operated with a high multiplication factor with suppressed fluctuation and achieve stable high sensitivity. Furthermore, for example, by setting a blocking bias voltage of the light-receiving element, the light-receiving element can be operated with suppressed fluctuation even at a low multiplication factor.This makes it possible to provide an optical distance measurement sensor that has a large dynamic range and can be used stably even when the ambient temperature changes.

[0011] In the aspect above, pulse current control can adjust the pulse current by setting an amount of charge accumulated by the charge accumulation unit based on the target sensitivity.

[0012] For example, in a case where the light-emitting element is irradiated with a high-intensity projected light pulse, a high current-carrying capacity is required to supply the pulse current. In this respect, since energy can be pre-accumulated in the charge storage unit (a passive element), and the high-intensity pulse current can be generated based on this accumulated energy, it is possible to cause the light-emitting element to emit a high-intensity projected light pulse using a simple circuit. Furthermore, since the intensity of the pulse current can be adjusted by setting the amount of charge pre-accumulated in the charge storage unit, the intensity of the projected light pulse can be easily adjusted.

[0013] In the aspect described above, pulse current control can adjust the amount of charge by controlling a voltage applied to the charge accumulation unit.

[0014] According to this aspect, since the amount of charge is accumulated in the charge accumulation unit proportional to the voltage applied by the control of the pulse current control, the adjustment of the amount of charge can be simplified, and thus the adjustment of the intensity of the projected light pulse can be further simplified.

[0015] In the aspect above, the optical distance measuring sensor may further include a second temperature sensor and a heater configured to maintain an operating temperature of the light-emitting element based on a temperature measured by the second temperature sensor.

[0016] According to this aspect, even at an ambient temperature that is not suitable for the use of the light-emitting element, heat can be supplied to the light-emitting element by heating, and the temperature of the light-emitting element can be set to a temperature suitable for use, thus extending the temperature range in which the optical distance measuring sensor can be used.

[0017] In the aspect above, the heater, the first temperature sensor, the light-emitting element and the light-receiving element can be mounted on the same substrate.

[0018] From this perspective, since heat can be easily transferred through the substrate, both the light-emitting and light-receiving elements can be advantageously heated by the heater. Furthermore, the temperatures of both the light-emitting and light-receiving elements can be satisfactorily measured by the first temperature sensor. That is, since heating and temperature measurement of the light-emitting and light-receiving elements can be performed by a single heater and temperature sensor, the circuit scale can be reduced and manufacturing costs lower compared to a configuration that includes two heaters, one each for the light-emitting and light-receiving elements, and two temperature sensors.

[0019] In the aspect above, the first temperature sensor and the second temperature sensor can be combined.

[0020] In comparison to a configuration that includes two separate temperature sensors, it is possible, according to this aspect, to reduce circuit scale and manufacturing costs by combining the first temperature sensor to set the multiplication factor of the light receiving element and the second temperature sensor to maintain the operating temperature of the light emitting element.

[0021] In the aspect above, the characteristic data can include a breakdown voltage of the light-receiving element, a temperature coefficient of the breakdown voltage, and a temperature at the time the breakdown voltage is obtained.

[0022] As described above, with the configuration in which the breakdown voltage, the temperature coefficient of the breakdown voltage and the temperature at the time of obtaining the breakdown voltage, which are useful for setting the multiplication factor with suppressed fluctuation, are included in the characteristic data, the multiplication factor at temperature can be set simply and appropriately by the temperature and the characteristic data.

[0023] In the aspect above, the light-emitting element can be a laser diode.

[0024] According to this aspect, since the object can be illuminated with light of high intensity and good directionality, the sensitivity can be effectively increased. ADVANTAGEOUS EFFECTS OF THE INVENTION

[0025] Thus, according to the present invention, it is possible to provide an optical distance measuring sensor that has a large dynamic range and can be used stably even when the ambient temperature changes. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a block diagram illustrating the construction of an optical distance measuring sensor 101 according to a first embodiment. Fig. Figure 2 is a block diagram illustrating the construction of a light projection unit 40 in the optical distance measuring sensor 101 according to the first embodiment. Fig. Figure 3 is a block diagram illustrating the construction of a light receiving unit 50 in the optical distance measuring sensor 101 according to the first embodiment. Fig. Figure 4 is a perspective view of the optical distance measuring sensor 101 according to the first embodiment. Fig. Figure 5 is a side view of the optical distance measuring sensor 101 according to the first embodiment. Fig. Figure 6 is a top view of a sensor substrate 12 according to the first embodiment, seen from one side of the object. Fig. Figure 7 is a top view of the sensor substrate 12 according to the first embodiment as seen from an operating unit side. Fig. Figure 8 is a block diagram illustrating the construction of a correction system 301 according to a second embodiment. Fig. Figure 9 is a diagram that shows an example of a temperature change of a breakdown voltage V BR an avalanche photodiode 53 according to the second embodiment. Fig. Figure 10 is a flowchart showing a procedure for obtaining a single parameter performed by the correction system 301 according to the second embodiment. Fig. Figure 11 is a block diagram illustrating the construction of a light projection unit 140 in the optical distance measuring sensor 101 according to a third embodiment. Fig. Figure 12 is a block diagram illustrating a structure of the optical distance measuring sensor 101 according to a fourth embodiment. Fig. Figure 13 is a block diagram illustrating the construction of a light projection unit 240 in the optical distance measuring sensor 101 according to the fourth embodiment. Fig. Figure 14 is a block diagram illustrating the construction of a light projection unit 340 in the optical distance measuring sensor 101 according to a fifth embodiment. DESCRIPTION OF EXECUTION FORMS

[0026] A preferred embodiment of the present invention is described in detail below with reference to the drawings. It should be noted that the embodiment described below is merely a specific example for implementing the present invention and is not intended to limit the design of the present invention. Furthermore, to facilitate understanding of the description, the same components in the drawings are designated with the same reference numerals wherever possible, and duplicate descriptions can be omitted.

[0027] The drawings may depict an x-axis, a y-axis, and a z-axis. The x-axis, y-axis, and z-axis form a right-handed, three-dimensional Cartesian coordinate system. Hereinafter, the direction of an arrow pointing along the x-axis can be referred to as an x-axis + side, and a direction opposite to the arrow can be referred to as an x-axis - side, and the same applies to the other axes. A z-axis + side and a z-axis - side can be referred to as an "object side" and an "operating unit side," respectively. The z-axis direction can be referred to as the "light ray direction." Furthermore, planes orthogonal to the x-axis, y-axis, or z-axis can be referred to as a yz-plane, a zx-plane, and an xy-plane, respectively. First embodiment

[0028] Fig. Figure 1 is a block diagram illustrating the construction of an optical distance measuring sensor 101 according to a first embodiment. Fig. Figure 2 is a block diagram illustrating the construction of a light projection unit 40 in the optical distance measuring sensor 101 according to the first embodiment. Fig. Figure 3 is a block diagram illustrating the construction of a light receiving unit 50 in the optical distance measuring sensor 101 according to the first embodiment.

[0029] As in the Fig. 1 to Fig. As illustrated in Figure 3, the optical distance measuring sensor 101 comprises a controller 20 (an example of a “pulse current controller”), a heating unit 31, a non-volatile memory 32, a temperature sensor 33 (an example of a “first temperature sensor” and a “second temperature sensor”), a communication unit 34, an operating unit 35, a display unit 36, a light projection unit 40 and a light receiving unit 50.

[0030] The controller 20 comprises a setting unit 21, a charge quantity setting unit 22 (an example of a "voltage control"), a pulse control 23, a light receiving element control 24, and a computing unit 25. The controller 20 includes, for example, a central processing unit (CPU) and a field-programmable gate array (FPGA).

[0031] The light projection unit 40 comprises a voltage amplification unit 41, a switching control 43, and a pulsed light generation unit 44. The pulsed light generation unit 44 comprises a charge accumulation unit 42, a laser diode 45 (an example of a "light-emitting element"), and a transistor 46.

[0032] The light receiving unit 50 comprises a blocking voltage control 51, an avalanche photodiode (APD) 53 (an example of a “light receiving element”), a current-to-voltage conversion unit 54, a signal amplification unit 55 and a dark current measuring unit 56.

[0033] Fig. Figure 4 is a perspective view of the optical distance measuring sensor 101 according to the first embodiment. Fig. Figure 5 is a side view of the optical distance measuring sensor 101 according to the first embodiment. Fig. Figure 6 is a top view of a sensor substrate 12 according to the first embodiment, seen from one side of the object. Fig. Figure 7 is a top view of the sensor substrate 12 according to the first embodiment as seen from an operating unit side.

[0034] As in the Fig. 4 to Fig. As illustrated in Figure 7, the optical distance measuring sensor 101 further comprises a sensor housing 11, a sensor substrate 12, a light projection lens 13 and a light receiving lens 14. The sensor housing 11 includes a light projection window 11a, a light receiving window 11b and a connector 11c.

[0035] The sensor housing 11 is an element that forms a housing for the optical distance measuring sensor 101 and is made of a resin, a metal, or the like. In the Fig. 4 and Fig. 5 is a side surface of the sensor housing 11 on the y-axis + side an opening, but the opening can be closed by a cover.

[0036] The sensor substrate 12, the light projection lens 13, and the light reception lens 14 are provided within the sensor housing 11. Two openings are formed along the x-axis on a side surface of the sensor housing 11 on the object side. One opening on the x-axis - side and one opening on the x-axis + side are provided by the light projection window 11a and the light reception window 11b, respectively.

[0037] The sensor substrate 12 has a plate shape that extends along a plane parallel to the xy-plane. The heating unit 31, the laser diode 45, and the avalanche photodiode 53 are mounted on a substrate surface of the sensor substrate 12 on the object side. The temperature sensor 33 and the charge accumulation unit 42 are mounted on a substrate surface of the sensor substrate 12 on the operating unit side.

[0038] The laser diode 45 emits pulsed laser light in a z-axis + direction. The laser light is emitted through the light projection lens 13 and the light projection window 11a to an object (not illustrated) located on the object side of the optical distance measuring sensor 101.

[0039] The light-receiving lens 14 receives the laser light reflected from the object (hereinafter referred to as reflected light) through the light projection window 11a and condenses the laser light onto the avalanche photodiode 53. A distance from the optical distance measuring sensor 101 to the object is measured based on the time (hereinafter referred to as propagation time) from the time when the laser light is emitted by the laser diode 45 until the time when the reflected light is received by the avalanche photodiode 53.

[0040] As in Fig. 1 and Fig. As illustrated in Figure 2, the non-volatile memory 32 is a readable / writable non-volatile memory device, such as an electrically erasable programmable read-only memory (EEPROM), and stores an operating mode table and a program (code). The non-volatile memory 32 can be another type of non-volatile memory device, such as flash memory.

[0041] The program can be installed externally. It is distributed in a state where it is stored on a storage medium readable by the optical distance sensor 101. The program can also be distributed via the internet, which is connected via a communication interface.

[0042] The target sensitivity of the optical distance measuring sensor 101 is, for example, a sensitivity for detecting the presence of the object. In the present embodiment, the target sensitivity can be set to, for example, five levels. The target sensitivity can be set to four or fewer levels or six or more levels.

[0043] The target sensitivity is also an index of an operating mode of the optical distance measuring sensor 101. In the operating mode table, each of the setting values ​​“LD power” and “APD multiplication factor” is assigned to the target sensitivity.

[0044] The target sensitivity can be set manually or automatically. In manual settings, the user can select one of five target sensitivity levels. Specifically, if the user performs a predefined operation to select the target sensitivity on the operating unit 35, the selected target sensitivity level will be displayed on the display unit 36. The user selects the target sensitivity by operating the operating unit 35 while viewing the display unit 36.

[0045] The setting unit 21 in the control unit 20 sets the target sensitivity of the optical distance measuring sensor 101 based on the operating content of the operating unit 35 and stores target sensitivity information, which specifies the set target sensitivity, in the non-volatile memory 32.

[0046] On the other hand, in a case where the target sensitivity is set automatically, the target sensitivity is set, for example, in a process in which a projected light spot is applied to each of the object to be determined, to determine its presence, and to a background of the object, and a blank button contained in the operating unit 35 is pressed. The setting unit 21 receives measurement results when the projected light spot is applied to the object and the background, based on the operating content of the operating unit 35, and sets an optimal target sensitivity that can distinguish the object and the background based on the measurement results obtained. The setting unit 21 stores the set target sensitivity in the non-volatile memory 32.

[0047] The controller 20 causes the charge quantity control unit 22 to adjust the pulse current supplied to the laser diode 45 based on the target sensitivity. Specifically, the charge quantity control unit 22 adjusts the amount of charge accumulated by the charge accumulation unit 42 in the light projection unit 40 based on the target sensitivity information and the operating mode table. In the present embodiment, the charge quantity control unit 22 controls the voltage applied to the charge accumulation unit 42 based on the target sensitivity information and the operating mode table.

[0048] In particular, the charge quantity setting unit 22 recognizes, based on the operating mode table, that the LD power corresponding to the target sensitivity specified by the target sensitivity information is “low” or “high”.

[0049] The charge quantity control unit 22 adjusts the charge quantity by controlling the voltage applied to the charge accumulation unit 42. In the present embodiment, the charge quantity control unit 22 outputs a pulse wave with the same on-time and a different duty cycle, according to the operating mode, to the light projection unit 40 in a predetermined cycle. Here, the duty cycle is a value obtained by dividing the on-time of the pulse by the predetermined cycle.

[0050] In particular, when the charge quantity control unit 22 detects that the LD power is “low”, the charge quantity control unit 22 outputs a pulse wave with a predetermined duty cycle (which may be referred to below as a first duty cycle) to the light projection unit 40.

[0051] On the other hand, when the charge quantity control unit 22 detects that the LD power is “high”, the charge quantity control unit 22 outputs a pulse wave with a predetermined duty cycle (which may be referred to below as a second duty cycle) that is greater than the first duty cycle to the light projection unit 40.

[0052] The voltage amplification unit 41 (see Fig. 2) in the light projection unit 40 amplifies the pulse wave received from the control unit 20 and outputs the amplified pulse wave to the charge accumulation unit 42.

[0053] In the present embodiment, the voltage amplification unit 41 comprises a low-pass filter and an operational amplifier. The low-pass filter in the voltage amplification unit 41 smooths the pulse wave received by the controller 20.

[0054] Specifically, when the pulse wave with the first duty cycle is received from controller 20, the low-pass filter smooths the pulse wave to generate a first DC voltage. Meanwhile, when the low-pass filter receives the pulse wave with the second duty cycle from controller 20, it smooths the pulse wave to generate a second DC voltage that is higher than the first DC voltage.

[0055] The operational amplifier amplifies the first DC voltage or the second DC voltage received by the low-pass filter non-inversely with a predetermined gain factor and outputs the amplified voltages to the charge accumulation unit 42.

[0056] The charge accumulation unit 42 accumulates charge to generate the pulsed current that is supplied to the laser diode 45. In the present embodiment, the charge accumulation unit 42 comprises, for example, four capacitor elements 42a connected in parallel. The capacitor element 42a is, for example, a ceramic capacitor. The capacitor element 42a can be another type of capacitor, such as a film capacitor or a tantalum electrolytic capacitor. The charge accumulation unit 42 can be configured to include three or fewer, or five or more, capacitor elements 42a connected in parallel.

[0057] The capacitor element 42a comprises one end connected to an output terminal of the operational amplifier of the voltage amplification unit 41 and to an anode 45A of the laser diode 45, and the other end connected to ground. The capacitor element 42a accumulates charge according to the first DC voltage or the second DC voltage applied by the voltage amplification unit 41, respectively.

[0058] The pulse control 23 (see Fig. 1) generates a pulsed current synchronously with a signal that is repeatedly supplied (hereinafter referred to as a repeating signal), and pulse-drives the laser diode 45. In particular, the pulse control 23 causes the charge accumulation unit 42 to discharge the accumulated charge synchronously with the repeating signal and pulse-drive the laser diode 45.

[0059] In the present embodiment, the repeating signal is, for example, a cyclic signal. The cyclic signal is a signal with a cycle of several microseconds and is generated within the optical distance measuring sensor 101. The cyclic signal can also be generated outside the optical distance measuring sensor 101. It should be noted that the repeating signal can be a signal that is repeatedly applied at random times.

[0060] The pulse control 23 outputs a control signal synchronously with the cyclic signal to the switching control 43 in the light projection unit 40.

[0061] The switching control 43 (see Fig. 2) acts as a driver of transistor 46. In particular, the switching control 43 drives transistor 46 in the pulse light generation unit 44 based on the control signal received from the pulse control 23.

[0062] In particular, when the control signal with a predetermined on-voltage or more is received by the pulse control 23, the switching control 43 outputs a signal to the transistor 46 to switch on the transistor 46 (hereinafter referred to as an on-signal).

[0063] In particular, the switching control 43 includes, for example, a bipolar transistor. The bipolar transistor comprises a collector to which a supply voltage is applied, a base that receives the control signal from the pulse control 23, and an emitter that is connected to ground via a resistor.

[0064] When the control signal with the predetermined on-voltage or higher is applied to the base, the bipolar transistor switches from an off state to an on state, and a current flows from the collector to the emitter. The current flows through the resistive element, thereby increasing the emitter voltage. The increased emitter voltage becomes an on-signal that switches on transistor 46 in the pulsed light generation unit 44.

[0065] Transistor 46, for example, is a field-effect transistor. Transistor 46 comprises a drain connected to a cathode 45K of the laser diode 45, a gate connected to the switching control 43 via a resistor, and a source connected to ground via a resistor.

[0066] When the on signal from the switching control 43 is input into the gate of the transistor 46, the transistor 46 switches from the off state to the on state, and thus a discharge circuit is closed from one end of the capacitor element 42a in the charge accumulation unit 42 to the other end of the capacitor element 42a through the laser diode 45, the transistor 46 and the ground.

[0067] Thus, the charge accumulated in the charge accumulation unit 42 is discharged, a pulsed discharge current flows through the laser diode 45, and the laser diode 45 emits pulsed light.

[0068] As in Fig. 5 to Fig. As illustrated in Figure 7, the charge accumulation unit 42 is arranged near the laser diode 45. In the present embodiment, four capacitor elements 42a are provided in the charge accumulation unit 42 on a surface of the sensor substrate 12 on the operating unit side.

[0069] The laser diode 45 is provided on a surface of the sensor substrate 12 on the object side. An anode connection 45A and a cathode connection 45K are provided on a surface on the back of the surface on the object side, i.e., a surface on the operating unit side.

[0070] On the surface on the operating unit side, the four capacitor elements 42a are provided in the charge accumulation unit 42 near the connection of the anode 45A and the connection of the cathode 45K.

[0071] In particular, the distance between the capacitor element 42a in the charge accumulation unit 42 and the terminal of the anode 45A or the terminal of the cathode 45K is shorter than the distance between the laser diode 45 and the avalanche photodiode 53.

[0072] As described above, with the configuration in which the charge accumulation unit 42 is provided near the laser diode 45, it is possible to react quickly to the transition of the transistor 46 to the on state, and thus it is possible to emit a pulsed laser light (hereinafter referred to as a projected light pulse) with a narrow time width and a large peak intensity from the laser diode 45.

[0073] As in Fig. 1 and Fig. 4 to Fig. As illustrated in Figure 7, the heating unit 31 maintains the operating temperature of the laser diode 45 based on the temperature measured by the temperature sensor 33. Specifically, the heating unit 31 controls and maintains the ambient temperature of the laser diode 45 so that it falls within an operating temperature range defined as the specification of the laser diode 45.

[0074] In the present embodiment, the heating unit 31 comprises seven resistance elements (an example of "first heater" and "second heater") connected in series, and a switch. In particular, the seven resistance elements and the switch are connected in series between a power supply voltage supply terminal and ground.

[0075] Three of the seven resistor elements are located on the y-axis + side of the laser diode 45 on the surface of the sensor substrate 12 on the object side. The other four of the seven resistor elements are located on the y-axis - side of the laser diode 45 on the surface of the sensor substrate 12 on the object side.

[0076] The temperature sensor 33 is positioned near the avalanche photodiode 53. In the present embodiment, the avalanche photodiode 53 and the temperature sensor 33 are located on the surface of the sensor substrate 12 on the object side and on the surface of the sensor substrate 12 on the operating unit side, respectively. When viewed from a top view, the temperature sensor 33 is positioned to overlap the avalanche photodiode 53.

[0077] In other words, the temperature sensor 33 is provided in a position facing the avalanche photodiode 53, with the sensor substrate 12 inserted between them on the surface of the sensor substrate 12 on the operating unit side.

[0078] The temperature sensor 33 measures the temperature, for example at predetermined intervals, and outputs temperature information indicating the measurement results to the controller 20.

[0079] The controller 20 monitors the temperature, which is indicated by the temperature information received from the temperature sensor 33, and switches on the switch in the heating unit 31 when the temperature reaches a predetermined value (for example, -10 °C) or less. Thus, a current flows through the seven resistance elements in the heating unit 31, the seven resistance elements generate heat, and the temperature of the laser diode 45 increases, thereby maintaining the ambient temperature of the laser diode 45 within its operating temperature range.

[0080] As in Fig. As shown in Figure 3, when the avalanche photodiode 53 in the light receiving unit 50 is irradiated with light in a reverse bias state, the avalanche photodiode 53 can detect the light with high sensitivity through a self-multiplication effect.

[0081] If the reverse bias applied to the avalanche photodiode 53 is increased, the avalanche photodiode 53 can be operated with a high multiplication factor (hereinafter referred to as gain).

[0082] The relationship between the reverse bias and the gain is not linear, and the gain increases exponentially as the reverse bias approaches the breakdown voltage of the avalanche photodiode 53.

[0083] Furthermore, when the avalanche photodiode 53 is used with high gain, the gain change due to temperature is large. This means that the temperature characteristics of the gain are poor.

[0084] The breakdown voltage and the temperature characteristics of the avalanche photodiode 53 vary for each individual unit. Therefore, it is difficult to operate the avalanche photodiode 53 with a consistently high gain across a wide temperature range simply by applying a constant reverse bias voltage to the avalanche photodiode 53.

[0085] As in Fig. 1 and Fig. Figure 3 illustrates that in the present embodiment, the non-volatile memory 32 stores characteristic data of the individual avalanche photodiode 53.

[0086] The characteristic data includes a breakdown voltage V BR the avalanche photodiode 53, a temperature coefficient γ of the breakdown voltage and a temperature T ref the avalanche photodiode 53, when a certain breakdown voltage V BR is obtained. The temperature T refis a temperature that serves as a reference when a correction is performed during operation of the optical distance measuring sensor 101.

[0087] In the present embodiment, the breakdown voltage V BR A reverse bias voltage is applied to cause a dark current of a predetermined value to flow through the avalanche photodiode 53. In particular, the predetermined value is, for example, 100 microamperes. Details of the temperature coefficient γ are described below.

[0088] A correction printout to provide a blocking bias V R To adjust the gain of the avalanche photodiode 53 to G, for example, f G (T, V BR , T ref , γ) expressed. Here, T is the temperature of the avalanche photodiode 53.

[0089] In the operating mode table, the target sensitivity specified by the target sensitivity information is assigned to the APD multiplication factor of "low" or "high".

[0090] In the present embodiment, the non-volatile memory 32 stores a low-gain correction expression, which is used when the APD multiplication factor is set to "low", and a high-gain correction expression, which is used when the APD multiplication factor is set to "high".

[0091] The low-gain correction expression is represented by f GL (T, V BR , T ref , γ) expressed and represents a blocking bias V R Ready to adjust the gain of the avalanche photodiode 53 to GL.

[0092] The high-gain correction expression is represented by f GH (T, V BR , T ref, γ) expressed and represents a blocking bias V R Ready to adjust the gain of the avalanche photodiode 53 to GH greater than GL.

[0093] The light receiving element control 24 adjusts the gain of the avalanche photodiode 53 based on the temperature T measured by the temperature sensor 33, the characteristic data and the target sensitivity.

[0094] In particular, the light receiving element control 24 calculates the blocking bias voltage V R regularly or irregularly and causes the blocking voltage control 51 in the light receiving unit 50 to increase the blocking bias voltage V R to produce.

[0095] In particular, the light receiving element control 24 recognizes, based on the operating mode table, that the APD multiplication factor corresponding to the target sensitivity specified by the target sensitivity information is “low” or “high”.

[0096] The light receiving element control 24 detects the temperature T through the temperature information output by the temperature sensor 33.

[0097] When the light receiver control 24 detects that the APD multiplication factor is "low", the light receiver control 24 receives the correction expression with low gain, the breakdown voltage V BR , the temperature T ref and the temperature coefficient γ of the non-volatile memory 32 and calculates the blocking bias V R by entering T, V BR , T ref and γ in the low-gain correction expression f GL (T, V BR , T ref , γ).

[0098] On the other hand, when the light receiving element control 24 detects that the APD multiplication factor is "high", the correction expression with high gain, the breakdown voltage V, is received. BR , the temperature Tref and the temperature coefficient γ of the non-volatile memory 32 and calculates the blocking bias V R by entering T, V BR , T ref and γ in the correction expression with high gain f GH (T, V BR , T ref , γ).

[0099] The light receiving element control 24 controls the blocking voltage control 51 in the light receiving unit 50 to apply the calculated blocking bias voltage V R to produce.

[0100] The reverse voltage control 51 includes, for example, a booster circuit. The reverse voltage control 51 generates the reverse bias voltage V. R according to the control by the light receiving element control 24 and sets the blocking bias V R to the cathode of the avalanche photodiode 53.

[0101] When the avalanche photodiode 53 is in a state in which the reverse bias voltage V RWhen the device is connected and receives reflected light from the object, a current flows from the cathode to the anode.

[0102] The current-to-voltage conversion unit 54 converts the current flowing through the avalanche photodiode 53 into a voltage and outputs the voltage to the signal amplification unit 55.

[0103] In the present embodiment, the current-to-voltage conversion unit 54 comprises, for example, a transimpedance amplifier and a capacitor element. The transimpedance amplifier comprises an input terminal connected to the anode of the avalanche photodiode 53 via the capacitor element, and an output terminal connected to the signal amplification unit 55.

[0104] An alternating current component of the current flowing through the avalanche photodiode 53 is fed into an input terminal of the transimpedance amplifier. A signal with a voltage corresponding to the current (hereinafter referred to as an output signal) is output from an output terminal of the transimpedance amplifier.

[0105] The signal amplification unit 55 amplifies an output signal from the current-to-voltage conversion unit 54 and outputs the amplified signal to the control unit 20.

[0106] The calculation unit 25 in the control unit 20 calculates the propagation time based on the output signal that is repeatedly received from the avalanche photodiode 53.

[0107] In the present embodiment, the computation unit 25 receives time series data based on the output signal received by the light receiving unit 50, for example each time the pulse control 23 outputs the control signal.

[0108] In particular, the processing unit 25 binaryizes the voltage of the output signal based, for example, on the relationship between the voltage of the output signal and a predetermined threshold value. A start time for the time series data is, for example, the time at which the control signal is output by the pulse controller 23.

[0109] The processing unit 25 integrates several parts of the time series data and obtains the integrated time series data (hereinafter referred to as integrated time series data). The integrated time series data includes a peak based on the reflected light received by the light receiving unit 52.

[0110] The calculation unit 25 receives a time at which the avalanche photodiode 53 receives the reflected light (hereinafter also referred to as a light reception time) by a predetermined detection threshold.

[0111] For example, the calculation unit 25 receives a time at which a peak, based on the reflected light in the integrated time series data, exceeds the detection threshold as the light reception time.

[0112] The calculation unit 25 estimates a value obtained by multiplying the propagation time from the start time of the time series data to the light reception time by the speed of light and dividing the product by 2 as the distance to the object.

[0113] It is preferred that the pulse current supplied to the laser diode 45 is designed such that the S / N ratio of the output signal obtained from the reflected light is high, while the laser diode 45 meets the standard of laser class 1.

[0114] The standard for laser class 1 includes a specification for average optical power. Specifically, it specifies that the average optical power should not exceed 0.39 mW.

[0115] The above specification is expressed by the following expression (1), where Po (mW), Pw (ns), and T (ns) are the optical power value, pulse width, and pulse cycle of the projected light pulse emitted by the laser diode 45, respectively. Po×Pw / T<0.39 mW

[0116] To increase the S / N ratio, it is necessary to increase Po and decrease Pw, but if the pulse current is generated based on a clock signal, the minimum Pw is half a clock cycle.

[0117] To achieve a high clock frequency while reducing costs, the clock frequency is generally 450 MHz or lower. This means the minimum Pw is (1 / 450 MHz) / 2 ≒ 1.1 ns.

[0118] The following expression (2) is obtained, where expression (1) is modified to Po / T < 0.39 / Pw (mW / ns) and 1.1 ns is substituted for Pw. Po / T<0.35(mW / ns)

[0119] That is, it is desirable to determine Po and T such that Po / T is as large as possible while satisfying expression (2).

[0120] In particular, Pw, Po and T can be, for example, 2.7 ns, 500 mw and 4000 ns respectively.

[0121] At this point, Po / T = 0.125 and expression (2) is satisfied. Furthermore, Po × Pw / T = 0.34 mW and expression (1) are also satisfied.

[0122] Similarly, Pw, Po and T can be 1.2 ns, 500 mw and 2000 ns respectively.

[0123] At this point, Po / T = 0.25 and expression (2) is satisfied. Furthermore, Po × Pw / T = 0.30 mW and expression (1) are also satisfied.

[0124] In a case where Po is made adjustable, T can be designed to change in conjunction with Po. For example, in a case where Pw, Po, and T It can be set to 2.7 ns, 500 mw or 4000 ns; if Po is set to 250 mW, T can be changed to 2000 ns.

[0125] This configuration allows for an increased number of measurements per unit of time, thus resulting in a noise reduction effect through integration. This enables the demonstration of the maximum signal-to-noise ratio while maintaining the laser class 1 standard. Second embodiment

[0126] Next, the optical distance measuring sensor 101 according to a second embodiment is described. In the second and subsequent embodiments, the description of items common to the first embodiment is omitted, and only differences are described. In particular, the same operations and effects of the same components are not mentioned separately for each embodiment.

[0127] The optical distance measuring sensor 101 according to the second embodiment differs from the optical distance measuring sensor 101 according to the first embodiment in that the characteristic data of the avalanche photodiode 53 are obtained by the control of the equipment 201.

[0128] Fig. Figure 8 is a block diagram illustrating the construction of a correction system 301 according to the second embodiment. As shown in Fig. As illustrated in Figure 8, the correction system 301 comprises the optical distance measuring sensor 101 and the equipment 201.

[0129] The communication unit 34 in the optical distance measuring sensor 101 is, for example, an IO-Link PHY and is a communication element that communicates with the equipment 201. The equipment 201 and the controller 20 can communicate with each other via the IO-Link PHY 34.

[0130] The communication unit 34 is connected to the equipment 201, for example via a connector 11c, during a shipping inspection after the product assembly of the optical distance measuring sensor 101. The equipment 201 controls the optical distance measuring sensor 101 via the IO-Link PHY 34.

[0131] In the present embodiment, the equipment 201 controls the controller 20 in the optical distance measuring sensor 101 to measure the dark current of the avalanche photodiode 53 while the temperature of the avalanche photodiode 53 is changed, and obtains the breakdown voltage V BR , the temperature T ref and the temperature coefficient γ.

[0132] The dark current measuring unit 56 in the light receiving unit 50 measures the dark current of the avalanche photodiode 53. In particular, the dark current measuring unit 56 measures the dark current when the reverse bias voltage is applied to the avalanche photodiode 53 in a state in which no light enters a light receiving surface of the avalanche photodiode 53.

[0133] In the present embodiment, the avalanche photodiode 53 is physically covered with a light-shielding element at the time of the dark current measurement. The dark current measuring unit 56 comprises, for example, a resistor element, a low-pass filter, and an operational amplifier.

[0134] The resistive element in the dark current measuring unit 56 comprises one end that is connected to the anode of the avalanche photodiode 53, and the other end that is connected to ground.

[0135] The dark current flowing through the avalanche photodiode 53 flows through the resistor element to ground. A voltage corresponding to this dark current (hereinafter referred to as the measurement voltage) is generated at one end of the resistor element. It should be noted that a capacitor element can be connected in parallel with the resistor element. This allows the measurement voltage to be stabilized.

[0136] The operational amplifier amplifies the measurement voltage received from one end of the resistive element non-inversely through the low-pass filter with a predetermined gain factor and outputs the amplified measurement voltage to the control 20.

[0137] Fig. Figure 9 is a diagram that shows an example of a temperature change of a breakdown voltage V BR The avalanche photodiode 53 according to the second embodiment is shown. The vertical axis represents the breakdown voltage V. BR The horizontal axis represents the temperature T of the avalanche photodiode 53.

[0138] As in Fig. 3, Fig. 6, Fig. 8 and Fig. As illustrated in Figure 9, the equipment 201 controls the controller 20 to determine the characteristic data based on the dark current value measured by the dark current measuring unit 56 and to write the determined characteristic data to the non-volatile memory 32. The characteristic data are determined based on the dark current values ​​at several ambient temperatures of the avalanche photodiode 53. Method for obtaining a single parameter

[0139] Next, a method for obtaining the single parameter of the avalanche photodiode 53 in the second embodiment is described in detail. Fig. Figure 10 is a flowchart showing the procedure for obtaining a single parameter as performed by the correction system 301 according to the second embodiment. As shown in Fig. As illustrated in Figure 10, the procedure for obtaining the individual parameter comprises steps S102 to S112, and each step is performed by the equipment 201 contained in the correction system 301.

[0140] First, the equipment 201 controls the controller 20 to cause the heating unit 31 to generate heat. The heating unit 31 changes the ambient temperature of the avalanche photodiode 53 (step S102).

[0141] In particular, the heat generated by the heating unit 31 is conducted through the sensor substrate 12 to the avalanche photodiode 53. This increases both the temperature of the avalanche photodiode 53 and the temperature around it.

[0142] Next, equipment 201 determines whether a predetermined condition for terminating the process to obtain the single parameter is met (step S104). Details of the predetermined condition are described below.

[0143] If the equipment 201 determines that the predetermined condition is not met (NO in step S104), then the equipment 201 controls the controller 20 to adjust the blocking bias applied to the avalanche photodiode 53, while the measuring voltage is monitored by the dark current measuring unit 56 (step S106).

[0144] In particular, the equipment 201 adjusts the reverse bias applied to the avalanche photodiode 53 so that the dark current flows through the avalanche photodiode 53 with the predetermined value.

[0145] Next, the equipment 201 controls the controller 20 to initiate a storage process for storing the blocking bias, that is, the breakdown voltage V. BR , when the dark current with the predetermined value flows through the avalanche photodiode 53, and the temperature information output by the temperature sensor 33, to be carried out (step S108).

[0146] Next, the equipment 201 determines whether a predetermined condition for terminating the process to obtain the individual parameter is met (step S104). The predetermined condition is, for example, that the storage process has been performed a predetermined number of times (two or more times) and that the breakdown voltage V is high enough. BR was measured within a necessary temperature range.

[0147] The storage process is performed several times while the heating of the avalanche photodiode 53 continues, and thus the breakdown voltages V are increased. BR stored at several of the temperatures T.

[0148] If the equipment 201 determines that the predetermined condition is met (YES in step S104), then the equipment 201 estimates the temperature coefficient γ based on the stored breakdown voltages V BR at the multiple temperatures T (step S110).

[0149] In particular, the breakdown voltage V increases BR , when the temperature T increases (see Fig. 9). The breakdown voltage V BR is essentially proportional to the temperature T.

[0150] The equipment 201 obtains a straight line SL by approximating a relationship between the temperature T and the breakdown voltage V. BR through a linear expression. Then the equipment 201 estimates a slope of the straight line SL as the temperature coefficient γ.

[0151] The equipment 201 controls the controller 20 to determine the estimated temperature coefficient γ and the breakdown voltage V. BR at temperature T ref and the temperature T ref to write the characteristic data of the individual avalanche photodiode 53 to the non-volatile memory 32 (step S112). Third embodiment

[0152] Next, the optical distance measuring sensor 101 according to a third embodiment is described. The optical distance measuring sensor 101 according to the third embodiment differs from the optical distance measuring sensor 101 according to the first embodiment in that the magnitude of the pulse current is set by adjusting an electrostatic capacitance in the charge quantity setting unit 22.

[0153] Fig. Figure 11 is a block diagram illustrating the construction of a light projection unit 140 in the optical distance measuring sensor 101 according to the third embodiment. Compared to the one in Fig. 2 illustrated light projection unit 40, as in Fig. As illustrated in Figure 11, the light projection unit 140 comprises a constant voltage supply unit 241 and a pulsed light generation unit 144 instead of the voltage amplification unit 41 and the pulsed light generation unit 44.

[0154] Compared to the one in Fig. The pulse light generation unit 144, as illustrated in Figure 2, further comprises a switching unit 47.

[0155] As in Fig. 1 and Fig. As illustrated in Figure 11, the charge quantity setting unit 22 in the controller 20 sets the electrostatic capacitance of the charge accumulation unit 42 based on the target sensitivity information and the operating mode table. The constant voltage supply unit 241 in the light projection unit 140 provides a substantially constant voltage from an output terminal.

[0156] The switching unit 47 in the pulsed light generation unit 144 comprises the same number of switches 47a as the number of capacitor elements 42a contained in the charge accumulation unit 42. In the present embodiment, the switches 47a comprise four switches 47a.

[0157] The four switches 47a are each provided corresponding to the four capacitor elements 42a. Each of the switches 47a comprises a first end that is connected to an output terminal of the constant voltage supply unit 241, and a second end that is connected to ground via the corresponding capacitor element 42a.

[0158] The switching unit 47 is not limited to a configuration comprising the same number of switches 47a as the number of capacitor elements 42a contained in the charge accumulation unit 42, and can be configured to include a smaller number of switches 47a than the number of capacitor elements 42a. In this case, some of the multiple capacitor elements 42a are connected to the output of the constant voltage supply unit 241 through the corresponding switches 47a, and the others are directly connected to the output of the constant voltage supply unit 241.

[0159] The anode 45A of the laser diode 45 is connected to the output terminal of the constant voltage supply unit 241. The charge quantity adjustment unit 22 sets the electrostatic capacitance of the charge accumulation unit 42 by controlling the opening and closing of the four switches 47a based on the target sensitivity information and the operating mode table.

[0160] In the present embodiment, the charge quantity control unit 22 can open and close each of the four switches 47a by outputting a logic signal to the switching unit 47. When the charge quantity control unit 22 detects that the LD power is "low," it closes some of the switches 47a and opens the others. Hereinafter, the number of switches 47a that are closed when the LD power is "low" can be referred to as the first number.

[0161] On the other hand, when the charge quantity setting unit 22 detects that the LD power is "high", the charge quantity setting unit 22 closes all four switches 47a. It should be noted that when the charge quantity setting unit 22 detects that the LD power is "high", the charge quantity setting unit 22 does not necessarily have to close all switches 47a, as long as the charge quantity setting unit 22 is configured to close a larger number (which may be referred to below as a second number) of switches 47a than the first number.

[0162] Thus, when the LD power is "low," the electrostatic capacitance of the charge accumulation unit 42 is the sum of the electrostatic capacitances of the first number of capacitor elements 42a (which can be referred to below as a first electrostatic capacitance). Conversely, when the LD power is "high," the electrostatic capacitance of the charge accumulation unit 42 is the sum of the electrostatic capacitances of the second number of capacitor elements 42a (which can be referred to below as a second electrostatic capacitance).

[0163] Then, when the LD power is “low” or “high”, the charge accumulation unit 42 is charged with a charge corresponding to the first electrostatic capacitance or the second electrostatic capacitance, respectively.

[0164] Since the second electrostatic capacitance is greater than the first electrostatic capacitance, the magnitude of the pulse current supplied to the laser diode 45 when the LD power is “high” is greater than the magnitude of the pulse current supplied to the laser diode 45 when the LD power is “low”. Fourth embodiment

[0165] The optical distance measuring sensor 101 according to a fourth embodiment is described. The optical distance measuring sensor 101 according to the fourth embodiment differs from the optical distance measuring sensor 101 according to the first embodiment in that the magnitude of the pulse current flowing through the laser diode 45 is adjusted by the voltage applied to the gate of the transistor 46.

[0166] Fig. Figure 12 is a block diagram illustrating the setup of the optical distance measuring sensor 101 according to the fourth embodiment. Compared to the one in Fig. Figure 1 illustrates the optical distance measuring sensor 101, as shown in Figure 1. Fig. As illustrated in Figure 12, the optical distance measuring sensor 101 according to the fourth embodiment comprises a controller 220 and a light projection unit 240 instead of the controller 20 and the light projection unit 40. Compared to the one in Fig. In the illustrated control unit 20, the control unit 220 includes a pulse control 223 instead of the charge quantity setting unit 22 and the pulse control 23.

[0167] Fig. Figure 13 is a block diagram illustrating the construction of a light projection unit 240 in the optical distance measuring sensor 101 according to the fourth embodiment. Compared to the one in Fig. 2 illustrated light projection unit 40, as in Fig. As illustrated in Figure 13, the light projection unit 240 comprises a constant voltage supply unit 241 and a switching control 243 instead of the voltage amplification unit 41 and the switching control 43.

[0168] As in Fig. 12 and Fig. As illustrated in Figure 13, one end and the other end of the capacitor element 42a are connected to the output terminal of the constant voltage supply unit 241 and to ground, respectively.

[0169] The switching controller 243 includes, for example, an AC signal source that generates an AC signal. The AC signal source operates under the control of the switching controller 243 and delivers the generated AC signal to the gate of transistor 46. The generation cycle of the pulse current is set by adjusting the cycle time of the AC signal. The magnitude of the pulse current is set by adjusting the amplitude of the AC signal.

[0170] The pulse control 223 generates a pulse current synchronously with the repeating signal, pulses the laser diode 45 and adjusts the pulse current based on the target sensitivity.

[0171] In the present embodiment, the pulse control 223 sets the magnitude of the pulse current flowing between the drain and the source of the transistor 46 by controlling the switching control 243 based on the target sensitivity information and the operating mode table.

[0172] In particular, the pulse control 223 recognizes, based on the operating mode table, that the LD power corresponding to the target sensitivity specified by the target sensitivity information is “low” or “high”.

[0173] When the pulse controller 223 detects that the LD power is “low”, the pulse controller 223 controls the switching controller 243 to set the amplitude of the AC signal supplied to the gate of transistor 46 to an initial value.

[0174] On the other hand, when the pulse control 223 detects that the LD power is “high”, the pulse control 223 controls the switching control 243 to adjust the amplitude of the AC signal supplied to the gate of transistor 46 to a second value that is greater than the first value.

[0175] The pulse control 223 sets the cycle of the alternating current signal supplied to the gate of transistor 46, for example to be synchronous with the cyclic signal generated within the optical distance measuring sensor 101.

[0176] Thus, it is possible to make the size of the pulse current flowing through the laser diode 45 when the LD power is “high” larger than the size of the pulse current flowing through the laser diode 45 when the LD power is “low”. Fifth embodiment

[0177] The optical distance measuring sensor 101 according to a fifth embodiment is described. The optical distance measuring sensor 101 according to the fifth embodiment differs from the optical distance measuring sensor 101 according to the fourth embodiment in that a current mirror circuit is used to adjust the magnitude of the pulse current flowing through the laser diode 45.

[0178] Fig. Figure 14 is a block diagram illustrating the construction of a light projection unit 340 in the optical distance measuring sensor 101 according to the fifth embodiment. Compared to the one in Fig. Figure 13 illustrated the 240 light projection unit, as shown in Fig. As illustrated in Figure 14, the light projection unit 340 comprises a pulsed light generation unit 344 and a switching control 343 instead of the pulsed light generation unit 44 and the switching control 243.

[0179] Compared to the one in Fig. In Figure 13, the pulsed light generation unit 44 includes a transistor 346 instead of transistor 46. The switching control 343 includes a transistor 343a and a constant current source 343b.

[0180] Transistor 343a and transistor 346 are NPN bipolar transistors. A collector, a base, and an emitter of transistor 346 are connected to the cathode 45K of laser diode 45, a base of transistor 343a, and ground, respectively.

[0181] The transistor 343a is diode-connected and comprises a collector and a base connected to the constant current source 343b, and an emitter connected to ground.

[0182] Since a voltage between the base and the emitter of transistor 346 is essentially equal to a voltage between the base and the emitter of transistor 343a, a current (hereinafter referred to as an output current) flowing between the collector and the emitter of transistor 346 is essentially equal to a current (hereinafter referred to as a reference current) flowing between the collector and the emitter of transistor 343a.

[0183] As in Fig. 12 and Fig. As illustrated in Figure 14, the pulse control 223 in the present embodiment sets the pulse current flowing between the collector and the emitter of the transistor 346 by controlling the constant current source 343b based on the target sensitivity information and the operating mode table.

[0184] In particular, the pulse control 223 recognizes, based on the operating mode table, that the LD power corresponding to the target sensitivity specified by the target sensitivity information is “low” or “high”.

[0185] When the pulse controller 223 detects that the LD power is “low”, the pulse controller 223 controls the constant current source 343b to adjust the magnitude of the reference current to the first value.

[0186] On the other hand, when the pulse control 223 detects that the LD power is “high”, the pulse control 223 controls the switching control 243 to adjust the magnitude of the reference current to the second value, which is greater than the first value.

[0187] The pulse control 223 causes the constant current source 343b to output a pulsed reference current, for example synchronously with a cyclic signal generated within the optical distance measuring sensor 101.

[0188] Thus, it is possible to make the size of the pulse current flowing through the laser diode 45 when the LD power is “high” larger than the size of the pulse current flowing through the laser diode 45 when the LD power is “low”.

[0189] In the first to fifth embodiments, the configuration in which the laser diode 45 is used as the light-emitting element was described, but the present disclosure is not limited thereto. The configuration can be such that, for example, a light-emitting diode is used as the light-emitting element.

[0190] In the first to fifth embodiments, the configuration in which the avalanche photodiode 53 is used as the light-receiving element was described, but the present embodiment is not limited to this. Other types of light-receiving elements can be used as long as the light-receiving elements have a self-amplifying function.

[0191] In the first embodiment and the third to fifth embodiments, the configuration described includes the communication unit 34 and the dark current measuring unit 56, but the present embodiment is not limited to this. The optical distance sensor 101 can be configured not to include the communication unit 34 and / or the dark current measuring unit 56. Even with such a configuration, the object of the present invention can be achieved.

[0192] In the first to fifth embodiments, the configuration was described in which the temperature sensor 33 serves three purposes: setting the multiplication factor of the avalanche photodiode 53, determining the characteristic data, and maintaining the operating temperature of the laser diode 45. However, the present embodiment is not limited to this configuration. The configuration can be such that the optical distance sensor 101 further comprises another temperature sensor (an example of a "second temperature sensor"), and this other temperature sensor serves either to determine the characteristic data or to maintain the operating temperature of the laser diode 45.

[0193] In the first to fifth embodiments, the configuration was described in which the heating unit 31 serves two purposes, namely maintaining the operating temperature of the laser diode 45 and changing the ambient temperature of the avalanche photodiode 53, but the present embodiment is not limited to this. The configuration can be such that the optical distance measuring sensor 101 further comprises another heating unit (an example of a "second heater") and the heating unit 31 (an example of a "first heater") and the other heating unit serve the purpose of maintaining the operating temperature of the laser diode 45 and the purpose of changing the ambient temperature of the avalanche photodiode 53, respectively.

[0194] The embodiment described above is provided to facilitate understanding of the present invention and is not intended to limit its design. Each element included in the embodiment, as well as the arrangement, material, condition, shape, size, and the like of each element, are not limited to those mentioned by way of example and can be appropriately modified. Furthermore, the configurations described in various embodiments can be partially substituted or combined. Supplementary Note 1

[0195] Optical distance measuring sensor (101) for estimating a distance to an object by measuring a time from the time at which light is emitted to the object until the time at which reflected light is received, the sensor comprising: a charge accumulation unit (42) configured to accumulate charge to generate a pulsed current to be supplied to a light-emitting element (45); a setting unit (21) configured to set a target sensitivity of the optical distance measuring sensor; a pulse current controller (20) configured to generate the pulse current synchronously with a repeating signal and to pulse-drive the light-emitting element, wherein the pulse current controller (20) is configured to adjust the pulse current based on the target sensitivity; a light receiving element (53) configured to receive the reflected light; a first temperature sensor (33); a non-volatile memory (32) in which characteristic data of the individual light-receiving element are stored; a light receiving element controller (24) configured to set a multiplication factor of the light receiving element based on a temperature measured by the first temperature sensor, the characteristic data, and the target sensitivity; and a calculation unit (25) configured to calculate time based on an output signal repeatedly received from the light receiving element in which the multiplication factor has been set. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2024-120761

[0001] JP 2015-75453 A

[0004]

Claims

[1] Optical distance measuring sensor for estimating a distance to an object by measuring a time from the time when light is emitted towards the object until the time when reflected light is received, the sensor comprising: a charge accumulation unit configured to accumulate charge to generate a pulsed current to be supplied to a light-emitting element; a setting unit that is configured to adjust the target sensitivity of the optical distance measuring sensor; a pulse current controller configured to generate the pulse current synchronously with a repeating signal and to pulse-drive the light-emitting element, wherein the pulse current controller is configured to adjust the pulse current based on the target sensitivity; a light receiving element configured to receive the reflected light; a first temperature sensor; a non-volatile memory in which characteristic data of the individual light-receiving element are stored; a light receiving element controller configured to set a multiplication factor of the light receiving element based on a temperature measured by the first temperature sensor, the characteristic data, and the target sensitivity; and a computing unit configured to calculate time based on an output signal repeatedly received from the light receiving element in which the multiplication factor has been set. [2] Optical distance measuring sensor according to claim 1, wherein the pulse current control adjusts the pulse current by setting an amount of charge accumulated by the charge accumulation unit based on the target sensitivity. [3] Optical distance measuring sensor according to claim 2, wherein the pulse current control adjusts the charge quantity by controlling a voltage applied to the charge accumulation unit. [4] Optical distance measuring sensor according to claim 1, further comprising: a second temperature sensor; and a heater configured to maintain an operating temperature of the light-emitting element based on a temperature measured by the second temperature sensor. [5] Optical distance measuring sensor according to claim 4, wherein the heater, the first temperature sensor, the light-emitting element and the light-receiving element are mounted on the same substrate. [6] Optical distance measuring sensor according to claim 4, wherein the first temperature sensor and the second temperature sensor are combined. [7] Optical distance measuring sensor according to claim 1, wherein the characteristic data include a breakdown voltage of the light receiving element, a temperature coefficient of the breakdown voltage and a temperature at the time of obtaining the breakdown voltage. [8] Optical distance measuring sensor according to claim 1, wherein the light-emitting element is a laser diode.

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