Control device, detection device, method for controlling an avalanche diode, program, and storage medium

Abstract

To stably operate an AD with high SNR and a high multiplication factor.SOLUTION: A control device 10 includes a control unit 100. The control unit 100 controls a reverse bias voltage applied to an avalanche diode (AD) 222. The control unit 100 controls the reverse bias voltage based on a level of a signal generated from the AD 222 when the AD 222 is not receiving electromagnetic waves.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a control device, a detection device, a method for controlling an avalanche diode, a program, and a storage medium. [Background technology]

[0002] In order to detect the distance to an object, a detection device using TOF (Time Of Flight) is sometimes used. Patent Document 1 describes an example of such a detection device. This detection device includes a transmitter and a receiver. The transmitter transmits light. The light transmitted from the transmitter is reflected by the object. The light reflected from the object is received by the receiver. The detection device can calculate the distance to the object based on the time it takes for the light transmitted from the transmitter to be received by the receiver.

[0003] An avalanche diode (AD) can be used for the receiver used in TOF. The AD can multiply the photocurrent by a reverse bias voltage. The higher the photocurrent multiplication factor, the higher the level of the photocurrent signal generated by the AD, but on the other hand, the higher the multiplication factor, the higher the noise level generated by the AD. In particular, Patent Document 2 describes that the shot noise increases as the multiplication factor increases. Furthermore, Patent Document 2 describes operating the AD at an optimal multiplication factor, that is, a multiplication factor that maximizes the SNR (Signal-to-Noise Ratio). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2011-095208 A [Patent Document 2] JP 2006-203050 A Summary of the Invention [Problem to be solved by the invention]

[0005] As described above, in order to operate an AD with a high SNR and a high gain, it is necessary to operate the AD at an optimal gain. However, the optimal gain of an AD varies depending on the external environment, for example, temperature. Therefore, if an AD is always operated with a constant reverse bias voltage, the noise level may exceed a certain level (tolerance value) due to fluctuations in the external environment.

[0006] One example of a problem to be solved by the present invention is to stably operate an AD with a high SNR and a high gain. [Means for solving the problem]

[0007] The first invention is A transmitter for transmitting electromagnetic waves; an avalanche diode that receives the electromagnetic waves reflected by an object; a control unit for controlling a reverse bias voltage applied to the avalanche diode; The control unit is a control device that controls the reverse bias voltage based on the level of a signal generated from the avalanche diode when the avalanche diode is not receiving the electromagnetic wave.

[0008] The second invention is A transmitter for transmitting electromagnetic waves; a receiver having an avalanche diode for receiving the electromagnetic waves transmitted from the transmitter and reflected from an object; A control unit that controls a reverse bias voltage applied to the avalanche diode; Equipped with The control unit is a detection device that controls the reverse bias voltage based on the level of a signal generated from the avalanche diode when the avalanche diode is not receiving an electromagnetic wave.

[0009] The third invention is An irradiation unit that irradiates electromagnetic waves; a receiver capable of receiving the electromagnetic wave reflected by an object; A control unit for controlling the receiver; Equipped with The control unit is a control device that controls the receiver based on a reception signal of the receiver when the receiver is not receiving the electromagnetic waves.

[0010] The fourth invention is 1. A method for controlling an avalanche diode, comprising the steps of: The method includes applying a reverse bias voltage to an avalanche diode and controlling the reverse bias voltage based on a level of a signal generated by the avalanche diode when the avalanche diode is not receiving electromagnetic waves.

[0011] The fifth invention is A program for causing a computer to execute the method according to the fourth invention.

[0012] The sixth invention is A storage medium storing a program according to a fifth aspect of the present invention. [Brief description of the drawings]

[0013] The above objects, as well as other objects, features and advantages, will become more apparent from the following preferred embodiments and the accompanying drawings.

[0014] [Figure 1] FIG. 2 is a diagram illustrating a control device according to an embodiment. [Diagram 2] 1 is a graph showing an example of the multiplication factor of an AD and the dark current of an AD. [Diagram 3] 11 is a graph showing an example of dark current noise of an AD and a received signal level of an AD. [Figure 4] FIG. 13 is a diagram for explaining an example of the operation of an AD. [Diagram 5] FIG. 13 is a diagram for explaining an example of the operation of an AD. [Figure 6]FIG. 13 is a diagram for explaining an example of the operation of an AD. [Figure 7] FIG. 2 is a diagram illustrating a control device according to the first embodiment. [Figure 8] FIG. 11 is a diagram illustrating a control device according to a second embodiment. [Figure 9] FIG. 11 is a diagram showing a detection device according to a third embodiment. [Figure 10] FIG. 13 is a diagram showing a detection device according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same components are given the same reference numerals and the description will be omitted as appropriate.

[0016] FIG. 1 is a diagram showing a control device 10 according to an embodiment.

[0017] The control device 10 will be outlined with reference to FIG. 1. The control device 10 includes a control unit 100. The control unit 100 controls a reverse bias voltage applied to an avalanche diode (AD) 222. The control unit 100 controls the reverse bias voltage based on the level of a signal generated from the AD222 when the AD222 is not receiving an electromagnetic wave (specifically, an electromagnetic wave transmitted from a transmitter (e.g., a transmitter 210 described later with reference to FIG. 9 or 10) and reflected by an object (e.g., an object O described later with reference to FIG. 9 or 10)). The level of this signal may be, for example, a maximum value in a predetermined period in which the AD222 is not receiving an electromagnetic wave, or may be an RMS (root mean square) in a predetermined period in which the AD222 is not receiving an electromagnetic wave.

[0018] According to the above-mentioned configuration, the AD222 can be stably operated with a high SNR (Signal-to-Noise Ratio) and a high multiplication factor. Specifically, a high reverse bias voltage is necessary to obtain a high multiplication factor for the AD. On the other hand, as the reverse bias voltage increases, the level of noise generated from the AD, particularly the level of dark current noise, increases. Therefore, in order to obtain a high SNR and a high multiplication factor, it is necessary to operate the AD with an optimal reverse bias voltage that can suppress the noise level below a certain level while obtaining a high multiplication factor. However, the optimal reverse bias voltage varies depending on the external environment, for example, temperature. Therefore, if the AD is always operated with a constant reverse bias voltage, the noise level may exceed a certain level (tolerance value) due to fluctuations in the external environment. In contrast, in the above-mentioned configuration, the control unit 100 controls the reverse bias voltage based on the level of the signal generated from the AD222 when the AD222 is not receiving an electromagnetic wave. With such a configuration, it is possible to apply an optimal reverse bias voltage to the AD222 according to fluctuations in the external environment. Therefore, the AD222 can be stably operated with a high SNR and a high multiplication factor.

[0019] Next, the control device 10 will be described in detail with reference to FIG.

[0020] The AD222 can receive electromagnetic waves. In one example, the electromagnetic waves are light (e.g., ultraviolet, visible, or infrared) and in another example, radio waves. In particular, if the AD222 receives light, the AD222 can be, for example, an avalanche photodiode (APD).

[0021] The control device 10 includes a control unit 100. The control unit 100 applies a reverse bias voltage to the AD222. Furthermore, the control unit 100 detects the level of a signal generated from the AD222 when the AD222 is not receiving an electromagnetic wave. This signal can be called noise (i.e., a signal that cannot contribute to the detection of an electromagnetic wave), and includes, for example, dark current noise, as described later with reference to FIG. 3. The level of this noise has a tendency to increase with an increase in the reverse bias voltage. In the example shown in FIG. 1, the control unit 100 compares the level of the noise with a target level, and controls the reverse bias voltage so that the level of the noise matches the target level. In this way, the AD222 can be stably operated with a high SNR and a high multiplication factor. The information on the target level is used to control the reverse bias voltage. The information on the target level is stored in a memory or the like (not shown), and the control unit 10 acquires the information on the target level by appropriately accessing the memory or the like.

[0022] The control unit 100 may control the reverse bias voltage based on the relationship between the dark current noise and the received signal level. Specifically, as described later with reference to Fig. 3, the control unit 100 can control the reverse bias voltage based on the ratio of the received signal level to the dark current noise, more specifically, so that the SNR is maximized.

[0023] The control device 10 (control unit 100) can be, for example, a circuit. Furthermore, a computer may cause the control device 10 (control unit 100) to apply a reverse bias voltage and control the reverse bias voltage. In one example, a program can cause a computer to execute the above-mentioned method. The program can be stored in a storage medium.

[0024] FIG. 2 is a graph showing an example of the multiplication factor of the AD and the dark current of the AD.

[0025] As shown in FIG. 2, both the multiplication factor and the dark current increase with an increase in the reverse bias voltage. Here, in the region where the reverse bias voltage is up to about 135V, the rate of change of the amplification factor with respect to the reverse bias voltage is relatively gentle (not more than a first predetermined value). Also, in the region where the reverse bias voltage is 140V or more, the rate of change of the amplification factor with respect to the reverse bias voltage is relatively steep (not less than a second predetermined value). On the other hand, the dark current increases rapidly when the reverse bias voltage exceeds about 140V. On the other hand, around the reverse bias voltage of 140V, there is a region where the multiplication factor exceeds 100 but the dark current is kept low. Therefore, in order to obtain a high multiplication factor for the AD while keeping the level of dark current noise low, it is desirable to operate the AD within the above-mentioned region (i.e., the region between the region where the rate of change of the amplification factor of the avalanche diode with respect to an increase in the bias voltage is not more than a first predetermined value and the region where the rate of change is not less than a second predetermined value).

[0026] FIG. 3 is a graph showing an example of the dark current noise of the AD and the reception signal level of the AD. The signal level on the vertical axis of FIG. 3 indicates the RMS of the dark current noise and the average level of the reception signal. In the example shown in FIG. 3, the dark current noise was measured without irradiating the AD with an electromagnetic wave (light), and the reception signal level was measured when the AD was irradiated with an electromagnetic wave (light). That is, the signal level of the dark current noise in FIG. 3 indicates the level of the output signal from the AD when the AD is not irradiated with an electromagnetic wave (light). Also, the reception signal level in FIG. 3 indicates the level of the output signal from the AD when the AD is receiving a predetermined electromagnetic wave. Note that the predetermined electromagnetic wave here is, for example, an electromagnetic wave irradiated from an irradiating unit and reflected by a reference reflector (not shown), and has an appropriate light amount (a light amount that can obtain an output signal that is not saturated with the AD and is not buried in noise). The reference reflector may be provided inside a housing that is the exterior of the device, or one provided outside may be used.

[0027] As shown in Fig. 3, the level of the received signal increases rapidly as the reverse bias voltage increases from 130 V to 140 V. On the other hand, the level of the dark current noise increases rapidly near the reverse bias voltage of 140 V.

[0028] In the example shown in FIG. 3, as described above, the dark current noise is measured without irradiating the AD with light, and the received signal level is measured when the AD is irradiated with light. In other words, the ratio of the received signal level to the dark current noise corresponds to the multiplication factor of the AD. Therefore, the optimal multiplication factor of the AD can be said to be the multiplication factor when the ratio of the received signal level to the dark current noise is maximized, and in the example shown in FIG. 3 in particular, it can be estimated as the multiplication factor at any voltage between 135V and 140V of the reverse bias voltage. In this way, as described above, the control unit 100 (FIG. 1) can control the reverse bias voltage based on the relationship between the dark current noise and the received signal level.

[0029] Each of Figures 4, 5, and 6 is a diagram for explaining an example of the operation of an AD. Figure 4 shows the operation of an AD at reverse bias voltages of 100V, 110V, 120V, and 130V. Figure 5 shows the operation of an AD at reverse bias voltages of 135V and 137V. Figure 6 shows the operation of an AD at a reverse bias voltage of 138V. In each of the graphs, the horizontal axis indicates time, and the vertical axis indicates the intensity of the signal output from the AD. In each example, the signal strength of approximately 2.5×10 -8 Electromagnetic waves are irradiated to the AD in seconds.

[0030] In the example shown in FIG. 4, the reverse bias voltage is approximately 2.5×10 -8 Even though the AD is irradiated with electromagnetic waves in seconds, the signal barely fluctuates. In other words, the reverse bias voltage in the example shown in Figure 4 is not high enough to obtain the multiplication factor required for the AD to detect the electromagnetic waves.

[0031] In the example shown in FIG. 5, the reverse bias voltage is approximately 2.5×10 -8 The signal fluctuates greatly every 100 s, and in other regions the signal is almost constant. In other words, the reverse bias voltage in the example shown in Figure 5 is at an appropriate level to obtain the multiplication factor required for the AD to detect electromagnetic waves, while suppressing the noise level generated by the AD below a certain level. In particular, the signal fluctuates significantly every 100 s, and in other regions the signal is almost constant. -8 The amplitude of the signal in seconds is approximately 2.5 × 10 at a reverse bias voltage of 135 V. -8 The amplitude of the signal at 137 V is larger than that at 135 V. Therefore, the AD can be operated more suitably with a reverse bias voltage of 137 V than with a reverse bias voltage of 135 V.

[0032] In the example shown in Figure 6, the -8 Although the signal fluctuates significantly from 1000 to 2000 s, the signal also fluctuates to a certain extent in other regions. In other words, the reverse bias voltage in the example shown in Figure 6 is high enough to obtain the multiplication factor required for the AD to detect electromagnetic waves, but is not high enough to suppress the level of noise generated by the AD to a certain level (tolerance).

[0033] In view of the above, in the examples shown in FIGS. 4, 5, and 6, it can be said that the optimal reverse bias voltage for AD is 137 V or in the vicinity thereof.

[0034] Furthermore, when comparing Figs. 5 and 6, when the AD is not irradiated with electromagnetic waves (e.g., -2.5 × 10 -8 sec to 2.5 x 10 -8 It can be said that the level of the signal (range of up to 100 ms) becomes high when the reverse bias voltage exceeds the optimum reverse bias voltage. Therefore, as explained with reference to Fig. 1, by controlling the reverse bias voltage based on the level of the signal generated by the AD222 when the AD222 is not receiving electromagnetic waves, it is possible to stably operate the AD222 with a high SNR and a high gain.

[0035] As described above, according to this embodiment, the AD222 can be operated stably with a high SNR and a high gain. EXAMPLES

[0036] Example 1 Fig. 7 is a diagram showing the control device 10 according to the first embodiment, and corresponds to Fig. 1 of the embodiment. The control device 10 according to the present embodiment is similar to the control device 10 according to the embodiment, except for the following points.

[0037] The control device 10 includes a calculation unit 110. The calculation unit 110 calculates the level of a signal generated (output) from the AD 222. In one example, the calculation unit 110 can calculate the level of the signal generated from the AD 222 by calculating the RMS of the signal generated from the AD 222.

[0038] The calculation unit 110 calculates the above level by excluding signals having a reference amplitude or more. By selecting an appropriate reference amplitude, it is possible to calculate the level of a signal generated from the AD222 when the AD222 is not receiving electromagnetic waves by excluding signals generated from the AD222 when the AD222 is receiving electromagnetic waves. For example, in the examples shown in Figs. 4, 5, and 6, the reference amplitude can be set to, for example, 0.04. In this case, the signal generated from the AD222 when the AD222 is receiving electromagnetic waves (approximately 2.5 x 10 -8 By excluding the signal at time s), it is possible to calculate the level of the signal generated by AD222 when AD222 is not receiving electromagnetic waves.

[0039] The control unit 100 controls the reverse bias voltage based on the calculation result of the calculation unit 110. By such an operation, the control unit 100 can control the reverse bias voltage based on the level of the signal generated from the AD222 when the AD222 is not receiving an electromagnetic wave.

[0040] The control unit 100 can control the reverse bias voltage so that the calculation result of the calculation unit 110 becomes a predetermined value when the AD222 is not receiving an electromagnetic wave (specifically, an electromagnetic wave transmitted from a transmitter (e.g., a transmitter 210 described later using FIG. 9 or 10) and reflected by an object (e.g., an object O described later using FIG. 9 or 10)). In one example, this predetermined value can be set to the level of a signal generated from the AD222 when a reverse bias voltage in the region described using FIG. 2 (i.e., a region between a region where the rate of change of the amplification degree of the avalanche diode with respect to an increase in bias voltage is equal to or less than a first predetermined value and a region where the rate of change is equal to or more than a second predetermined value) is applied.

[0041] In this embodiment as well, the AD222 can be operated stably with a high SNR and a high gain.

[0042] Example 2 Fig. 8 is a diagram showing a control device 10 according to a second embodiment, and corresponds to Fig. 1 of the embodiment. The control device 10 according to this embodiment is similar to the control device 10 according to the embodiment, except for the following points.

[0043] The control device 10 includes a calculation unit 110 and a switch 120. The calculation unit 110 calculates the level of a signal generated from the AD222. In one example, the calculation unit 110 can calculate the level of a signal generated from the AD222 by calculating the RMS of the signal generated from the AD222. The switch 120 switches on / off the transmission of the signal to the calculation unit 110. The control unit 100 controls the reverse bias voltage based on the calculation result of the calculation unit 110.

[0044] The switch 120 is capable of switching the above-mentioned transmission on or off depending on the timing at which the AD222 receives electromagnetic waves. Specifically, the switch 120 turns off the above-mentioned transmission when the AD222 receives electromagnetic waves, and turns on the above-mentioned transmission when the AD222 does not receive electromagnetic waves. Such an operation of the switch 120 enables the calculation unit 110 to exclude a signal generated from the AD222 when the AD222 receives electromagnetic waves, and to calculate the level of a signal generated from the AD222 when the AD222 does not receive electromagnetic waves.

[0045] In addition, when the timing at which the electromagnetic wave reaches the AD 222 is known in advance, the switch 120 can switch the above-mentioned transmission on or off based on that timing. In particular, as will be described later with reference to FIG. 10, when the AD 222 receives the electromagnetic wave transmitted from the transmitter 210 and reflected from the object O, the switch 120 can switch the above-mentioned transmission on or off based on the timing at which the electromagnetic wave is transmitted from the transmitter 210.

[0046] The control unit 100 controls the reverse bias voltage based on the calculation result of the calculation unit 110. By such an operation, the control unit 100 can control the reverse bias voltage based on the level of the signal generated from the AD222 when the AD222 is not receiving an electromagnetic wave.

[0047] In this embodiment as well, the AD222 can be operated stably with a high SNR and a high gain.

[0048] Example 3 FIG. 9 is a diagram showing a detection device 20 according to the third embodiment.

[0049] An overview of the detection device 20 will be described with reference to FIG. 9. The detection device 20 includes a control device 10, a transmitter 210, a receiver 220, and a calculation unit 230. The control device 10 shown in FIG. 9 is similar to the control device 10 shown in FIG. 7. The transmitter 210 can transmit electromagnetic waves. The receiver 220 has an AD222. The AD222 shown in FIG. 9 is similar to the AD222 shown in FIG. 7. In particular, in the example shown in FIG. 9, the AD222 receives electromagnetic waves transmitted from the transmitter 210 and reflected from the object O. The calculation unit 230 calculates the distance from the detection device 20 to the object O based on the time from when the electromagnetic waves are transmitted from the transmitter 210 to when the receiver 220 (AD222) receives the electromagnetic waves.

[0050] Similar to the example shown in FIG. 7, the control unit 100 controls the reverse bias voltage applied to the avalanche diode (AD) 222. Furthermore, the control unit 100 controls the reverse bias voltage based on the level of a signal generated from the AD 222 when the AD 222 is not receiving an electromagnetic wave. Here, the control unit 100 may control the reverse bias voltage based on the level of a signal generated from the AD 222 during a period when the transmitter 210 is not transmitting (emitting) an electromagnetic wave to the object O. With this configuration, it is possible to detect the level of a signal generated from the AD 222 when the AD 222 is not receiving an electromagnetic wave. Therefore, similar to the example shown in FIG. 7, the AD 222 can be stably operated with a high SNR and a high gain.

[0051] Next, the detection device 20 will be described in detail with reference to FIG.

[0052] The transmitter 210 can transmit electromagnetic waves. In one example, the transmitter 210 can transmit light (e.g., ultraviolet light, visible light, or infrared light), and in another example, can transmit radio waves. When the transmitter 210 can transmit light, the detection device 20 can function as a LIDAR (LIght Detecion And Ranging). When the transmitter 210 can transmit light, the transmitter 210 can be, for example, a laser diode (LD). When the transmitter 210 can transmit radio waves, the detection device 20 can function as a RADAR (RAdio Detecion And Ranging).

[0053] The electromagnetic waves transmitted from the transmitter 210 are reflected by the object O. The electromagnetic waves reflected from the object O are received by the receiver 220, specifically, the AD 222.

[0054] The calculation unit 230 can measure the distance to the object O based on the TOF (Time Of Flight). Specifically, the calculation unit 230 can calculate the distance from the detection device 20 to the object O based on the time from when the electromagnetic wave is transmitted from the transmitter 210 to when the receiver 220 (AD 222) receives the electromagnetic wave.

[0055] In the same manner as in the example shown in FIG. 7, the calculation unit 110 calculates the level of the signal generated from the AD222. In particular, the calculation unit 110 calculates the level by excluding signals having a reference amplitude or more. That is, the calculation unit 110 can calculate the level of the signal generated from the AD222 when the AD222 is not receiving an electromagnetic wave by selecting an appropriate reference amplitude and excluding the signal generated from the AD222 when the AD222 is receiving an electromagnetic wave. The control unit 100 controls the reverse bias voltage based on the calculation result of the calculation unit 110. By such an operation, the control unit 100 can control the reverse bias voltage based on the level of the signal generated from the AD222 when the AD222 is not receiving an electromagnetic wave.

[0056] Example 4 Fig. 10 is a diagram showing a detection device 20 according to a fourth embodiment, and corresponds to Fig. 9 of the third embodiment. The detection device 20 according to this embodiment is similar to the detection device 20 according to the third embodiment, except for the following points.

[0057] The detection device 20 includes a control unit 240. The control unit 240 controls the transmitter 210, and in particular controls the timing of transmission of electromagnetic waves by the transmitter 210.

[0058] The control device 10 shown in Fig. 10 is similar to the control device 10 shown in Fig. 8, and includes a switch 120. The switch 120 switches on or off the transmission of a signal generated by the AD 222 to the control unit 100. The on or off of the transmission of the switch 120 is controlled by the control unit 240.

[0059] The control unit 240 controls the on / off of the above-mentioned transmission by the switch 120 based on the timing of transmission of the electromagnetic wave by the transmitter 210. When the distance from the detection device 20 to the object O is determined in advance within a certain range, the time from when the electromagnetic wave is transmitted from the transmitter 210 to when the receiver 220 (AD222) receives the electromagnetic wave is also determined within a certain range. Therefore, by switching the above-mentioned transmission on / off based on the timing of transmission of the electromagnetic wave by the transmitter 210, the control unit 100 can control the reverse bias voltage based on the level of the signal generated from the AD222 when the AD222 is not receiving the electromagnetic wave.

[0060] Although the embodiment and examples have been described above with reference to the drawings, these are merely examples of the present invention, and various configurations other than those described above can also be adopted.

[0061] This application claims priority based on Japanese Patent Application No. 2017-185127, filed September 26, 2017, the disclosure of which is incorporated herein in its entirety.

Claims

1. A transmitter for transmitting electromagnetic waves; an avalanche diode that receives the electromagnetic waves transmitted from the transmitter and reflected by an object; a calculation unit that calculates a level of a signal generated from the avalanche diode during a period in which the amplitude of the signal is less than a predetermined amplitude; A control unit that controls a reverse bias voltage applied to the avalanche diode; Equipped with the control unit controls the reverse bias voltage based on a ratio of a received signal level when the avalanche diode receives a predetermined electromagnetic wave to a level of the signal; 2. A control device according to claim 1, wherein the predetermined electromagnetic wave is an electromagnetic wave irradiated from the transmitter and reflected by a reference reflector.

2. 2. The control device according to claim 1, The control device is characterized in that the control unit controls the reverse bias voltage so that a ratio of a received signal level when the avalanche diode is receiving the specified electromagnetic wave to a level of the signal is maximized.

3. 3. The control device according to claim 1, The control device, wherein the predetermined electromagnetic wave has a light amount that allows the avalanche diode to obtain an output that is not saturated and is not buried in noise.

4. The control device according to any one of claims 1 to 3, The control device, wherein the level of the signal is a maximum value during the period.

5. The control device according to any one of claims 1 to 3, The level of the signal is the root mean square over the period.

6. A transmitter for transmitting electromagnetic waves; an avalanche diode that receives the electromagnetic waves transmitted from the transmitter and reflected by an object; a first calculation unit that calculates a level of a signal generated from the avalanche diode during a period in which the amplitude of the signal is less than a predetermined amplitude; A control unit that controls a reverse bias voltage applied to the avalanche diode; a second calculation unit that calculates a distance to a target object based on a time taken for the electromagnetic wave transmitted from the transmitter to be received by the avalanche diode; Equipped with the control unit controls the reverse bias voltage based on a ratio of a received signal level when the avalanche diode receives a predetermined electromagnetic wave to a level of the signal; A detection device, wherein the predetermined electromagnetic wave is an electromagnetic wave irradiated from the transmitter and reflected by a reference reflector.

7. A transmitter for transmitting electromagnetic waves; a receiver for receiving the electromagnetic wave transmitted from the transmitter and reflected by an object; a calculation unit that calculates a level of a signal generated by the receiver during a period in which the amplitude of the signal is less than a predetermined amplitude; A control unit for controlling the receiver; Equipped with the control unit controls the receiver based on a ratio of a received signal level when the receiver receives a predetermined electromagnetic wave to a level of the signal; 2. A control device according to claim 1, wherein the predetermined electromagnetic wave is an electromagnetic wave irradiated from the transmitter and reflected by a reference reflector.

8. 1. A method for controlling an avalanche diode that receives electromagnetic waves transmitted from a transmitter and reflected from an object, comprising: Calculating the level of a signal generated by the avalanche diode during a period in which the amplitude of the signal is less than a predetermined amplitude; controlling a reverse bias voltage applied to the avalanche diode based on a ratio of a received signal level when the avalanche diode receives the electromagnetic wave irradiated from the transmitter and reflected by a reference reflector to a level of the signal; method.

9. A program for causing a computer to execute the method according to claim 8.

10. A storage medium storing the program according to claim 9.

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