Patent Description:
In the field of light detecting devices, when light detection is performed by a light detector, dark current due to thermal electrons tends to increase with an increase in temperature of the light detector. When the dark current increases as described above, the S/N ratio of the light detector decreases, and thus, there is a possibility of deterioration in detection accuracy of the light detecting device such as a decrease in reliability of a detection signal from the light detector, for example. Hence, it is important to cool the light detector to reduce influences of thermal electrons in order to improve the detection accuracy of a light detecting device. For example, Patent Literature <NUM> discloses a liquid-cooling type cooling mechanism capable of cooling a light detector by circulation of a coolant. In this liquid-cooling type cooling mechanism, the light detector can be cooled by exchanging heat between the light detector and the coolant circulating by driving of a pump.

However, in the liquid-cooling type cooling mechanism as described above, pulsation occurs in the flow of the coolant when the pump performs an operation of delivering the coolant, and vibration derived from the pulsation can be transmitted to the light detector, a measurement apparatus using the light detecting device, and the like. In this case, there is a possibility that detection conditions such as a sample position and a light condensing position may change during a detection period in which the light detector performs light detection. As a result, detection accuracy of the light detecting device may deteriorate.

The present disclosure provides a light detecting device and a method for controlling the light detecting device that can suppress deterioration in detection accuracy.

Alight detecting device according to an embodiment of the present disclosure includes: a light detector; a heat exchanger thermally connected to the light detector; a coolant flow channel configured to be connected to the heat exchanger and allow a coolant for cooling the light detector to flow; a pump configured to cause the coolant flow in the coolant flow channel; and a control unit that controls the pump. The control unit performs control such that a first drive power is supplied to the pump during a detection period in which the light detector performs light detection, and a second drive power is supplied to the pump during a standby period in which the light detector stands by without performing light detection, and the first drive power is smaller than the second drive power.

In the light detecting device, the coolant delivered by the pump and reaching the heat exchanger exchanges heat with the light detector via the heat exchanger to cool the light detector. Here, the first drive power supplied to the pump during the detection period is smaller than the second drive power supplied to the pump during the standby period. Therefore, during the detection period, an operation of the pump is reduced when delivering the coolant. Accordingly, vibration caused by pulsation that may occur in the flow of the coolant also decreases. As a result, it is possible to suppress deterioration in detection accuracy of the light detecting device due to transmission of vibration derived from pulsation. Further, a magnitude of the heat capacity of the coolant itself can be used by using the coolant. Therefore, even when the operation of the pump is reduced during the detection period, heat from the heat exchanger can be absorbed using the heat capacity of the coolant itself. Therefore, it is possible to maintain a cooling effect of the light detector by the coolant even during the detection period, and it is possible to suppress deterioration in detection accuracy of the light detecting device due to an increase in temperature of the light detector. Hence, it is possible to suppress deterioration in detection accuracy according to the light detecting device described above.

In the light detecting device described above, the control unit may control to stop supplying the first drive power during the detection period. In this case, since the operation of the pump is stopped during the detection period, the vibration derived from the pulsation described above can be more reliably suppressed. Consequently, it is possible to more reliably suppress deterioration in detection accuracy of the light detecting device due to transmission of the vibration derived from the pulsation.

In the light detecting device described above, the control unit may perform control such that the first drive power is larger than zero and smaller than the second drive power during the detection period. In this case, since the operation of the pump is continued during the detection period, it is possible to suppress a reduction in cooling effect of the light detector by the coolant. That is, an increase in temperature of the light detector during the detection period can be suppressed. Hence, it is possible to suppress the transmission of the vibration derived from the pulsation while suppressing the increase in temperature of the light detector according to the configuration described above. As a result, it is possible to more reliably suppress deterioration in detection accuracy of the light detecting device.

The light detecting device described above may further include an electronic cooler thermally connected to the light detector and the heat exchanger. In this case, since the light detector can be efficiently cooled by the electronic cooler, the increase in temperature of the light detector can be more reliably suppressed. As a result, it is possible to more reliably suppress deterioration in detection accuracy of the light detecting device.

In the light detecting device described above, the control unit may perform control such that a third drive power is supplied to the electronic cooler during the detection period. In this case, the control unit can cool the light detector by controlling the electronic cooler to be driven even during the detection period. On the other hand, although heat is generated by driving the electronic cooler, the heat is transferred to the heat exchanger and then dissipates to the coolant. As described above, since the magnitude of the heat capacity of the coolant itself can be used, the cooling effect of the light detector by the coolant can be maintained. Hence, according to the configuration described above, it is possible to more reliably suppress the increase in temperature of the light detector while suppressing the transmission of the vibration derived from the pulsation by cooling the light detector by the electronic cooler and the coolant. As a result, it is possible to more reliably suppress deterioration in detection accuracy of the light detecting device.

The light detecting device described above may further include at least one of a first sensor configured to detect a temperature of the light detector and a second sensor configured to detect a temperature of the heat exchanger. In this case, it is possible to sense an undesired increase in temperature in the light detecting device by detecting the temperature of at least one of the light detector and the heat exchanger.

The light detecting device described above may further include at least a first sensor that detects a temperature of the light detector, in which the control unit may control supply of the third drive power to the electronic cooler such that the temperature detected by the first sensor is equal to or lower than a first allowable temperature during the detection period. In this case, it is possible to suppress an undesired increase in temperature in the light detecting device by supplying the third drive power according to the temperature of the light detector.

In the light detecting device described above, the control unit may perform control such that the third drive power at a time t1 is larger than the third drive power at a time t2 before the time t1 during the detection period. During the detection period, since the drive power of the pump is small, the temperature of the light detector may gradually increase. In this respect, the cooling effect of the light detector by the electronic cooler can be enhanced by controlling the third drive power to be larger at the time t1 after the time t2. Consequently, it is possible to suppress a situation in which the temperature of the light detector increases. As a result, it is possible to more reliably suppress deterioration in detection accuracy of the light detecting device due to an increase in temperature of the light detector.

The light detecting device described above may further include a fan that blows air toward the coolant flow channel, in which the control unit may perform control such that a fourth drive power is supplied to the fan during the detection period, and a fifth drive power is supplied to the fan during the standby period, and the fourth drive power is smaller or larger than the fifth drive power. In this case, since the coolant is cooled by the fan blowing air to the coolant flow channel, it is possible to enhance the cooling effect of the light detector by the coolant. In such a mechanism including the fan, vibration of the fan itself is transmitted to the light detecting device, and thereby the detection accuracy of the light detecting device may deteriorate. In this respect, it is possible to suppress deterioration in detection accuracy of the light detecting device due to transmission of the vibration of the fan by causing the fourth drive power supplied to the fan during the detection period to be smaller than the fifth drive power supplied to the fan during the standby period. In a case where the fan is sufficiently separated from the light detector, the fourth drive power supplied to the fan during the detection period is caused to be larger than the fifth drive power supplied to the fan during the standby period, and thereby heat dissipation efficiency of the coolant in the coolant flow channel can be enhanced, and deterioration in detection accuracy of the light detecting device due to an increase in temperature of the light detector can be suppressed.

In the light detecting device described above, the coolant flow channel may further include a radiator that releases heat of the coolant, and the fan may blow air toward the radiator. In this case, the coolant is cooled by the radiator and the fan so that the cooling effect of the light detector by the coolant can be further enhanced.

The light detecting device described above may further include at least a second sensor that detects a temperature of the heat exchanger, in which the control unit may perform control such that a sixth drive power is supplied to the pump and the sixth drive power is larger than the first drive power in a case where the temperature detected by the second sensor exceeds a second allowable temperature during the detection period. An increase in temperature of the light detector leads to an increase in dark current value. Accordingly, the heat exchanger is likely to have a high temperature because heat of the light detector is transferred thereto. In this respect, when the temperature of the heat exchanger exceeds the second allowable temperature, the sixth drive power larger than the first drive power is supplied to the pump, and thereby it is possible to suppress an increase in dark current value and a situation in which the heat exchanger has a high temperature. As a result, it is possible to suppress an undesired increase in temperature in the light detecting device.

According to an embodiment of the present disclosure, there is provided a method for controlling a light detecting device including a light detector, a heat exchanger thermally connected to the light detector, a coolant flow channel configured to be connected to the heat exchanger and allow a coolant for cooling the light detector to flow, and a pump configured to cause the coolant to flow in the coolant flow channel. The method for controlling a light detecting device includes: a step of supplying a first drive power to the pump during a detection period in which the light detector performs light detection; and a step of supplying a second drive power to the pump during a standby period in which the light detector stands by without performing light detection. The first drive power is smaller than the second drive power.

In the method for controlling the light detecting device, the first drive power supplied to the pump during the detection period is smaller than the second drive power supplied to the pump during the detection period. Therefore, during the detection period, an operation of the pump is reduced when delivering the coolant. Accordingly, vibration caused by pulsation that may occur in the flow of the coolant also decreases. As a result, it is possible to suppress deterioration in detection accuracy of the light detecting device due to transmission of vibration derived from pulsation. Further, by using the coolant, a magnitude of the heat capacity of the coolant itself can be used. Therefore, even when the operation of the pump is reduced during the detection period, heat from the heat exchanger can be absorbed using the heat capacity of the coolant itself. Therefore, it is possible to maintain a cooling effect of the light detector by the coolant even during the detection period, and it is possible to suppress deterioration in detection accuracy of the light detecting device due to an increase in temperature of the light detector. Hence, it is possible to suppress deterioration in detection accuracy according to the method for controlling a light detecting device described above.

According to the present disclosure, there are provided a light detecting device and a method for controlling the light detecting device that can suppress deterioration in detection accuracy.

Hereinafter, a light detecting device and a method for controlling the light detecting device according to an embodiment of the present disclosure will be described in detail with reference to the drawings. In the following description, the same or equivalent elements are denoted by the same reference numerals, and redundant description thereof will be omitted as appropriate.

<FIG> is a schematic configuration diagram illustrating a light detecting device <NUM> according to the embodiment. The light detecting device <NUM> is used, for example, in a detection unit of a measurement apparatus such as a microscope apparatus or an analysis apparatus. The light detecting device <NUM> includes a light detector <NUM> that detects light L (hereinafter, referred to as "measurement light L") that is a measurement target. Further, the light detecting device <NUM> includes, as a cooling mechanism for cooling the light detector <NUM>, an electronic cooler <NUM>, a heat exchanger <NUM>, a first tube <NUM>, a second tube <NUM>, a pump <NUM>, a radiator <NUM>, a fan <NUM>, and a control unit <NUM>.

<FIG> is a cross-sectional view illustrating a configuration in the vicinity of the light detector <NUM>. As illustrated in <FIG>, the light detector <NUM> is accommodated in a case <NUM>. The case <NUM> is, for example, formed in a box shape opening upward and is made of a metal material. A side wall <NUM> of the case <NUM> has an opening 3a formed to enable measurement light L to be introduced into the case <NUM>. The light detector <NUM> detects the light intensity of the measurement light L introduced from the opening 3a and generates an electric signal corresponding to the light intensity. The light detector <NUM> transmits the generated electric signal, for example, to a measurement apparatus such as a microscope apparatus or an analysis apparatus. The light detector <NUM> is, for example, a photomultiplier tube (PMT). The light detector <NUM> may be an optical semiconductor element such as an avalanche photo diode (APD) or silicon photomultipliers (SiPM).

The electronic cooler <NUM> is disposed on the light detector <NUM> in the case <NUM>. The electronic cooler <NUM> is provided to cool the light detector <NUM>. The electronic cooler <NUM> is an active cooling element and is, for example, a Peltier element that performs cooling or heating using a phenomenon (Peltier effect) in which heat moves when electricity flows. The electronic cooler <NUM> is driven to absorb heat at a heat absorption surface <NUM> formed toward the light detector <NUM> and cause heat dissipation at a heat dissipation surface <NUM> formed toward the side opposite to the heat absorption surface <NUM>. The light detector <NUM> can be cooled to a temperature below the freezing point (that is, a temperature lower than that of a coolant R) via the heat absorption surface <NUM> by the heat transfer by the electronic cooler <NUM>. Drive of the electronic cooler <NUM> is controlled by the control unit <NUM> (see <FIG>). The heat absorption surface <NUM> is connected to the light detector <NUM> via a heat transfer portion <NUM>. The heat transfer portion <NUM> is a member having thermal conductivity and enables heat to be transferred from the light detector <NUM> to the heat absorption surface <NUM>.

Hence, the heat absorption surface <NUM> enters into a thermally connected state to the light detector <NUM>. In the present specification, the "thermally connected state" means a state in which two members are directly or indirectly connected to each other and heat can be transferred (heat transfer) between the two members. Hence, the connection between the heat absorption surface <NUM> and the light detector <NUM> may be any connection as long as thermal connection is realized, and physically, the connection may be an indirect connection via another member such as the heat transfer portion <NUM> or a direct connection without another member therebetween. The heat absorption surface <NUM> and the light detector <NUM> may be connected by performing bonding using an adhesive material or a sheet material having a high thermal conductivity from the viewpoint of suppressing thermal resistance.

The heat exchanger <NUM> is disposed on the heat dissipation surface <NUM> of the electronic cooler <NUM>. The heat dissipation surface <NUM> is thermally connected to the heat exchanger <NUM>. Hence, the heat transmitted from the heat absorption surface <NUM> to the heat dissipation surface <NUM> is transferred to the heat exchanger <NUM>. The heat dissipation surface <NUM> and the heat exchanger <NUM> may be connected by performing bonding using an adhesive material or a sheet material having a high thermal conductivity from the viewpoint of suppressing thermal resistance.

The heat exchanger <NUM> is disposed, for example, to block an upper opening portion of the case <NUM>. The heat exchanger <NUM> includes, for example, a flow channel <NUM>, a heat sink <NUM>, and a housing <NUM> that accommodates them. The flow channel <NUM> is a space in the housing <NUM> and is formed to have a U shape in the cross section illustrated in <FIG>. In the housing <NUM>, the first tube <NUM> is connected to a projecting portion constituting an inlet 21a of the flow channel <NUM>. The second tube <NUM> is connected to a projecting portion constituting an outlet 21b of the flow channel <NUM>. The heat sink <NUM> is disposed in the flow channel <NUM>. The coolant R flows from the first tube <NUM> through the inlet 21a into the flow channel <NUM>. The coolant R is a cooling medium (for example, water or the like) for cooling the light detector <NUM>. The coolant R flowing into the flow channel <NUM> passes between comb-shaped fins of the heat sink <NUM> and flows from the outlet 21b into the second tube <NUM>. When the coolant R passes through the heat sink <NUM>, heat exchange is performed between the heat sink <NUM> and the coolant R so that the heat released from the heat dissipation surface <NUM> of the electronic cooler <NUM> is transferred to the coolant R. In this manner, heat exchange is performed between the light detector <NUM> and the coolant R via the electronic cooler <NUM> and the heat sink <NUM>, and thereby the light detector <NUM> is cooled.

As illustrated in <FIG>, the light detecting device <NUM> further includes a first sensor <NUM> and a second sensor <NUM>. The first sensor <NUM> is a temperature sensor that detects a temperature of the light detector <NUM>. The first sensor <NUM> is installed, for example, on the light detector <NUM> in the case <NUM>. More specifically, the first sensor <NUM> is installed in the heat transfer portion <NUM> thermally connected to the light detector <NUM>. The first sensor <NUM> detects a temperature of the light detector <NUM> and outputs a signal H1 (see <FIG>) indicating a detected temperature of the light detector <NUM> to the control unit <NUM>. The second sensor <NUM> is a temperature sensor that detects a temperature of the heat exchanger <NUM>. The second sensor <NUM> is thermally connected to, for example, the heat sink <NUM>. The second sensor <NUM> detects a temperature of the heat exchanger <NUM> and outputs a signal H2 (see <FIG>) indicating a detected temperature of the heat exchanger <NUM> to the control unit <NUM>.

The following description is provided with reference to <FIG> again. The second tube <NUM> connected to the outlet 21b of the heat exchanger <NUM> is connected to an inlet 40a of a flow channel in the radiator <NUM> disposed at a position separated from the heat exchanger <NUM>. A pump <NUM> is provided at a position on the second tube <NUM>. On the other hand, the first tube <NUM> connected to the inlet 21a of the heat exchanger <NUM> is connected to an outlet 40b of the flow channel in the radiator <NUM>. Hence, the coolant R flowing from the outlet 21b of the heat exchanger <NUM> into the second tube <NUM> flows into the inlet 40a of the radiator <NUM> via the pump <NUM>. The coolant R flowing from the outlet 40b of the radiator <NUM> into the first tube <NUM> flows into the heat exchanger <NUM> again from the inlet 21a.

Thus, the flow channel <NUM> (see <FIG>) of the heat exchanger <NUM>, the first tube <NUM>, the radiator <NUM>, and the second tube <NUM> constitute a closed circulation channel RP (coolant flow channel) that enables the coolant R to circulate (flow) between the radiator <NUM> and the heat exchanger <NUM>. The first tube <NUM> and the second tube <NUM> may be, for example, a soft tube made of a material having flexibility such as butyl rubber or a hard tube made of a material that does not have flexibility.

In the circulation channel RP, the pump <NUM> delivers the coolant R in one direction so that the coolant R circulates in a direction of arrows illustrated in <FIG>. A type of pump <NUM> is not particularly limited. As the pump <NUM>, for example, a known pump capable of generating pulsation, such as a diaphragm pump, can be employed. Drive of the pump <NUM> is controlled by the control unit <NUM>. The radiator <NUM> causes heat dissipation of the coolant R through heat exchange between the coolant R flowing in the flow channel of the radiator <NUM> and outside air. In this manner, the radiator <NUM> cools and lowers the temperature of the coolant R through dissipation of heat received by the coolant R in the heat exchanger <NUM>.

The fan <NUM> is disposed to blow air toward the radiator <NUM>. The fan <NUM> cools the coolant R by blowing air toward the flow channel of the radiator <NUM>. Drive of the fan <NUM> is controlled by the control unit <NUM>. The coolant R cooled by the radiator <NUM> and the fan <NUM> again flows into the heat exchanger <NUM> and exchanges heat with the heat exchanger <NUM> (more specifically, the heat sink <NUM>). The pump <NUM>, the radiator <NUM>, and the fan <NUM> are accommodated, for example, in a case <NUM> other than the case <NUM> accommodating the light detector <NUM>. The case <NUM> is connected to the case <NUM> by the first tube <NUM> and the second tube <NUM>. The case <NUM> is disposed at a position separated from the case <NUM>.

As described above, the coolant R continues cooling the light detector <NUM> via the heat exchanger <NUM> while circulating between the heat exchanger <NUM> and the radiator <NUM> in the circulation channel RP. Specifically, the coolant R cools the light detector <NUM> by heat exchange with the heat exchanger <NUM> and causes dissipation of the heat received by the heat exchange in the radiator <NUM>. Thereafter, the cooled coolant R returns to the heat exchanger <NUM> again to cool the light detector <NUM> again.

The control unit <NUM> is, for example, an electronic control unit such as a microcomputer including a memory such as a RAM or a ROM, a processor (arithmetic circuit) such as a CPU, a communication interface, and a storage unit such as a storage element such as an EPROM or a flash memory. The control unit <NUM> functions by executing a program stored in a memory by a processor. The control unit <NUM> is accommodated in the case <NUM> together with, for example, the pump <NUM>, the radiator <NUM>, and the fan <NUM>. The control unit <NUM> is electrically connected to a power source, and power is supplied from the power source to the control unit <NUM>. The control unit <NUM> is electrically connected to the pump <NUM>, the fan <NUM>, and the electronic cooler <NUM>, and the power of the power source is supplied to the pump <NUM>, the fan <NUM>, and the electronic cooler <NUM> via the control unit <NUM>. The power of the power source is not limited to the case of being supplied via the control unit <NUM>. For example, a signal from the control unit <NUM> may be input to the power source, and a drive power based on the signal may be directly supplied from the power source to the pump <NUM>, the fan <NUM>, and the electronic cooler <NUM>. The power source may be a battery mounted in the case <NUM> or may be externally supplied by an AC adapter or the like.

The signal H1 from the first sensor <NUM> and the signal H2 from the second sensor <NUM> are input to the control unit <NUM> (see <FIG>). Further, the control unit <NUM> includes, for example, a signal input unit <NUM> that receives an external signal Os indicating a timing at which the light detector <NUM> performs detection from the outside (for example, a measurement apparatus such as a microscope apparatus or an analysis apparatus) of the light detecting device <NUM> and that outputs a trigger signal TG on the basis of the external signal Os. The external signal Os may be a complementary metal oxide semiconductor (CMOS) signal or a transistor transistor logic (TTL) signal from a logic device such as a microcomputer or a field programmable gate array (FPGA) or may be a serial signal from a personal computer. The signal input unit <NUM> is not limited to the reception of the external signal Os and may be an interface that receives a user's operation input. As the interface, for example, a push button, a switch, a touch panel, or the like can be employed. In this case, the signal input unit <NUM> outputs the trigger signal TG indicating the timing at which the light detector <NUM> performs detection in response to the user's operation input. The control unit <NUM> controls the drive of the pump <NUM>, the fan <NUM>, and the electronic cooler <NUM> on the basis of the trigger signal TG, the signal H1, and the signal H2.

<FIG> is a block configuration diagram illustrating a functional configuration of the control unit <NUM>. <FIG> is a timing chart illustrating an example of each signal processed by the control unit <NUM>. As illustrated in <FIG>, the control unit <NUM> includes, as functional configurations, a pump/fan controller <NUM> (hereinafter, referred to as the "PF controller <NUM>") that controls the drive of the pump <NUM> and the fan <NUM> and an electronic cooler controller <NUM> (hereinafter, referred to as the "EC controller <NUM>") that controls drive of the electronic cooler <NUM>. The trigger signal TG from the signal input unit <NUM> is input to the PF controller <NUM> and the EC controller <NUM>.

As illustrated in <FIG>, the trigger signal TG is a pulse signal including a high-level state (ON state) and a low-level state (OFF state). The trigger signal TG enters into the ON state during a detection period Tk in which the light detector <NUM> performs light detection. The trigger signal TG enters into the OFF state during a standby period Tt in which the light detector <NUM> stands by. The detection period Tk is a period from a time point at which the light detector <NUM> starts the light detection to a time point at which the light detection is ended. The standby period Tt is a period excluding the detection period Tk. The standby period Tt is a period in which the light detector <NUM> stands by without performing the light detection. That is, the standby period Tt is a period before the time point at which the light detector <NUM> starts the light detection, and the standby period Tt is a period after the time point at which the light detector <NUM> ends the light detection.

At the time point at which the light detector <NUM> starts the light detection (that is, a timing of switching from the standby period Tt to the detection period Tk), the trigger signal TG switches from the OFF state to the ON state. Accordingly, at the time point at which the light detector <NUM> ends the light detection (that is, a timing of switching from the detection period Tk to the standby period Tt), the trigger signal TG switches from the ON state to the OFF state. The PF controller <NUM> and the EC controller <NUM> control drive of each control target according to a state of the input trigger signal TG.

The detection period Tk and the standby period Tt can be set at any duration time and timing. For example, the detection period Tk and the standby period Tt may be set to change according to a measurement target and a measurement method. The light detector <NUM> is not limited to continuously performing the light detection in the detection period Tk and the light detector <NUM> may intermittently perform the light detection a plurality of times in the detection period Tk. The control unit <NUM> may not include the signal input unit <NUM>, and the detection period Tk and the standby period Tt may be set in the control unit <NUM> in advance.

The PF controller <NUM> controls the drive of the pump <NUM> by a drive signal SG1 and controls the drive of the fan <NUM> by a drive signal SG2 according to the state of the trigger signal TG. The PF controller <NUM> adjusts a drive power of the pump <NUM> by the drive signal SG1. Here, the "drive power" means a magnitude of power supplied from the power source to the pump <NUM>. Power is represented by a product of voltage and current. Therefore, in the present specification, the "drive power" may be described in place of a "drive voltage" or may be described in place of a "driving current". In general, as the drive power of the pump <NUM> increases, the cooling effect of the light detector <NUM> by the coolant R increases. However, as the drive power of the pump <NUM> increases, an operation of the pump <NUM> when the pump <NUM> delivers the coolant R increases, and accordingly, vibration derived from pulsation that can be generated by the flow of the coolant R also increases. The vibration affects the detection accuracy of the light detecting device <NUM>. On the other hand, as the drive power of the pump <NUM> decreases, the operation of the pump <NUM> when the pump <NUM> delivers the coolant R decreases, and the vibration derived from the pulsation also decreases. In this case, an influence of the vibration derived from the pulsation on the detection accuracy of the light detecting device <NUM> is reduced. However, as the drive power of the pump <NUM> decreases, the cooling effect of the light detector <NUM> by the coolant R decreases.

The drive signal SG1 is, for example, a pulse signal including a high-level state (ON state) and a low-level state (OFF state). More specifically, the drive signal SG1 is, for example, a pulse width modulation (PWM) signal (PWM control). The PWM control is a control method of controlling drive power by setting a constant cycle of ON and OFF of a pulse train from input of a constant voltage and changing an ON-time width (that is, a duty cycle). The drive signal SG1 is not limited to the PWM signal and may be an amplitude modulation (AM) signal. When the drive signal SG1 enters into the ON state, the pump <NUM> enters into an energized state. On the other hand, when the drive signal SG1 enters into the OFF state, the pump <NUM> enters into a non-energized state. The drive power of the pump <NUM> is determined according to a duty cycle of the drive signal SG1. Specifically, as the duty cycle of the drive signal SG1 increases, the drive power of the pump <NUM> increases. On the other hand, as the duty cycle of the drive signal SG1 decreases, the drive power of the pump <NUM> decreases.

For example, when the duty cycle of the drive signal SG1 is <NUM>%, the pump <NUM> always enters into the non-energized state so that the drive power of the pump <NUM> is <NUM>. In this case, the pump <NUM> enters into a stopped state without being driven. In a case where the duty cycle of the drive signal SG1 is <NUM>%, the pump <NUM> always enters into the energized state so that the drive power of the pump <NUM> is equal to power suitable for driving the pump <NUM> at a rated output (that is, rated power). When the duty cycle of the drive signal SG1 is <NUM>%, a time during the energized state and a time during the non-energized state are the same in a unit cycle. In this case, the drive power of the pump <NUM> is equal to half of the rated power. In this manner, the drive power of the pump <NUM> is adjusted by the duty cycle of the drive signal SG1.

The PF controller <NUM> adjusts the duty cycle of the drive signal SG1 according to the state of the trigger signal TG. Specifically, as illustrated in <FIG>, the PF controller <NUM> controls a duty cycle of the drive signal SG1 during the detection period Tk in which the trigger signal TG enters into the ON state to be smaller than a duty cycle of the drive signal SG1 during the standby period Tt in which the trigger signal TG enters into the OFF state. That is, the PF controller <NUM> controls a drive power <NUM> (first drive power) supplied to the pump <NUM> during the detection period Tk to be smaller than a drive power <NUM> (second drive power) supplied to the pump <NUM> during the standby period Tt. The drive power <NUM> of the pump <NUM> during the standby period Tt is set within a range of a drive power larger than at least <NUM>. The drive power <NUM> of the pump <NUM> during the detection period Tk is set to <NUM> or to be within a range of a drive power larger than <NUM> and smaller than the drive power <NUM> of the pump <NUM> during the standby period Tt. In the embodiment, the PF controller <NUM> sets the duty cycle of the drive signal SG1 during the detection period Tk to <NUM>%. In this case, during the detection period Tk, the drive power <NUM> of the pump <NUM> becomes <NUM>, and the drive of the pump <NUM> is stopped.

On the other hand, the PF controller <NUM> sets the duty cycle of the drive signal SG1 during the standby period Tt to, for example, <NUM>%. In this case, during the standby period Tt, the drive power <NUM> of the pump <NUM> becomes power corresponding to <NUM>% of the duty cycle of the drive signal SG1, and the pump <NUM> enters into a state of being driven to sufficiently exhibit the cooling effect of the light detector <NUM> by the coolant R (normal driving). The PF controller <NUM> drives the pump <NUM> with a predetermined drive power in response to the drive signal SG1. At this time, the pump <NUM> is driven so that the delivery amount of the coolant R becomes a predetermined delivery amount. The "delivery amount of the coolant R" by the pump <NUM> means a volume of the coolant R delivered by the pump <NUM> per unit time in the circulation channel RP. That is, the delivery amount of the coolant R is adjusted by the drive power supplied to the pump <NUM> in order to drive the pump <NUM>. Hence, the "drive power of the pump <NUM>" can be described in place of the "delivery amount of the coolant R by the pump <NUM>".

The PF controller <NUM> controls the drive of the fan <NUM> in response to the drive signal SG2 so that an air blowing amount of the fan <NUM> becomes a predetermined air blowing amount. The "air blowing amount of the fan <NUM>" means a volume of air moved per unit time by the drive of the fan <NUM>. As the air blowing amount of the fan <NUM> is larger, the heat dissipation effect to the coolant R is enhanced so that the cooling effect of the light detector <NUM> by the coolant R is enhanced. However, as the air blowing amount of the fan <NUM> increases, a rotational speed of a drive unit of the fan <NUM> increases, and accordingly mechanical vibration of the fan <NUM> itself increases. The vibration affects the detection accuracy of the light detecting device <NUM>. On the other hand, as the air blowing amount of the fan <NUM> decreases, the rotational speed of the drive unit of the fan <NUM> decreases, and the mechanical vibration of the fan <NUM> itself also decreases. In this case, an influence of the mechanical vibration of the fan <NUM> itself on the detection accuracy of the light detecting device <NUM> is reduced. However, as the air blowing amount of the fan <NUM> decreases, the heat dissipation effect to the coolant R decreases, and thus, the cooling effect of the light detector <NUM> by the coolant R decreases. The air blowing amount of the fan <NUM> is adjusted by the drive power supplied to the fan <NUM> in order to drive the fan <NUM>. Hence, the "air blowing amount of the fan <NUM>" can be described in place of the "drive power of the fan <NUM>". Thus, as the drive power of the fan <NUM> increases, the mechanical vibration of the fan <NUM> increases. On the other hand, as the drive power of the fan <NUM> decreases, the mechanical vibration of the fan <NUM> decreases.

The PF controller <NUM> adjusts the drive power of the fan <NUM> in response to the drive signal SG2. The "drive power of the fan <NUM>" means a magnitude of the power supplied from the power source to the fan <NUM>. This drive power can be described in place of a drive voltage or a drive current. The drive signal SG2 is, for example, a pulse signal including a high-level state (ON state) and a low-level state (OFF state). More specifically, the drive signal SG2 is, for example, a pulse width modulation (PWM) signal (PWM control). The drive signal SG2 is not limited to the PWM signal and may be the amplitude modulation (AM) signal. When the drive signal SG2 enters into the ON state, the fan <NUM> enters into an energized state. On the other hand, when the drive signal SG2 enters into the OFF state, the fan <NUM> enters into a non-energized state. The drive power of the fan <NUM> is determined according to a duty cycle of the drive signal SG2. Specifically, as the duty cycle of the drive signal SG2 increases, the drive power of the fan <NUM> increases. On the other hand, as the duty cycle of the drive signal SG2 decreases, the drive power of the fan <NUM> decreases.

In the embodiment, a waveform of the drive signal SG2 is set to be the same as a waveform of the drive signal SG1 described above. Hence, similarly to the drive signal SG1, the PF controller <NUM> controls a duty cycle of the drive signal SG2 during the detection period Tk to be smaller than a duty cycle of the drive signal SG2 during the standby period Tt. That is, the PF controller <NUM> controls a drive power <NUM> (fourth drive power) supplied to the fan <NUM> during the detection period Tk to be smaller than a drive power <NUM> (fifth drive power) supplied to the fan <NUM> during the standby period Tt. The drive power <NUM> of the fan <NUM> during the standby period Tt is set within a range of a drive power larger than at least <NUM>. The drive power <NUM> of the fan <NUM> during the detection period Tk is set to <NUM> or to be within a range of a drive power larger than <NUM> and smaller than the drive power <NUM> of the fan <NUM> during the standby period Tt. In the embodiment, the PF controller <NUM> sets the duty cycle of the drive signal SG2 during the detection period Tk to <NUM>% and sets the duty cycle of the drive signal SG2 during the standby period Tt to <NUM>%. In this case, during the detection period Tk, the drive power <NUM> of the fan <NUM> becomes <NUM>, and the drive of the pump <NUM> is stopped. On the other hand, during the standby period Tt, the drive power <NUM> of the fan <NUM> becomes power corresponding to the duty cycle of <NUM>% of the drive signal SG1, and the fan <NUM> enters into a state of being driven to sufficiently exhibit the cooling effect of the light detector <NUM> by the coolant R (normal driving).

Hence, in the embodiment, while the pump <NUM> and the fan <NUM> are normally driven during the standby period Tt, the drive of both the pump <NUM> and the fan <NUM> is stopped during the detection period Tk. In this case, during the detection period Tk, the vibration due to the drive of the pump <NUM> and the fan <NUM> can be suppressed to decrease as compared with the standby period Tt, but the cooling effect of the light detector <NUM> by the coolant R also decreases. However, by using the coolant R, a magnitude of the heat capacity of the coolant R itself can be used. Therefore, even when the operation of the pump <NUM> is reduced during the detection period Tk, heat from the heat exchanger <NUM> can be absorbed using the heat capacity of the coolant R itself. More specifically, for example, since the heat capacity of the coolant R is larger than that of air which is a cooling medium in a case of air cooling, a temperature of the coolant R is less likely to increase. Thus, even when the drive of the pump <NUM> and the fan <NUM> is stopped during the detection period Tk, a rapid temperature change of the light detector <NUM> can be suppressed so that an increase in dark current of the light detector <NUM> is suppressed. The dark current is a current that causes a dark signal detected by the light detector <NUM> in a state where the measurement light L is not incident on the light detector <NUM> during an operation of the light detector <NUM>.

A cause of dark current generation can vary depending on a situation, but examples of the cause of dark current related to temperature include thermionic emission. For example, when the light detector <NUM> is the photomultiplier tube, thermal electrons indicate electrons emitted from a photoelectric surface or a dynode regardless of incidence of light. Such a signal derived from the thermal electrons is considered as unnecessary noise (dark) in light detection and causes deterioration in detection accuracy of the light detecting device <NUM>. The generation of thermal electrons increases as the temperature of the light detector <NUM> increases, and the generation of thermal electrons decreases as the temperature of the light detector <NUM> decreases. Hence, when the light detector <NUM> is cooled, the generation of thermal electrons is suppressed, and the generation of dark current is also suppressed. On the other hand, when the temperature of the light detector <NUM> increases, the generation of thermal electrons increases, and the generation of dark current increases. Such a phenomenon is similar in a case where the light detector <NUM> is the optical semiconductor element.

In the detection period Tk, the cooling effect of the light detector <NUM> by the coolant R is maintained, but the cooling effect of the light detector <NUM> by the coolant R is smaller than that in the standby period Tt. Therefore, in the detection period Tk, the temperature of the light detector <NUM> may increase as time elapses. In this respect, the EC controller <NUM> controls the electronic cooler <NUM> to be driven at least in the detection period Tk. For example, the EC controller <NUM> continuously drives the electronic cooler <NUM> at least from the time point at which the light detector <NUM> starts the light detection to the time point at which the light detector <NUM> ends the light detection. Even in the detection period Tk, the light detector <NUM> is continuously cooled by the electronic cooler <NUM> as the driving of the electronic cooler <NUM> is continued. Consequently, it is possible to suppress an increase in temperature of the light detector <NUM> in the detection period Tk. In the embodiment, the EC controller <NUM> can lower the temperature of the light detector <NUM> to a temperature (for example, below the freezing point) lower than the temperature of the coolant R by continuously driving the electronic cooler <NUM> that actively performs cooling in the entire period including the standby period Tt and the detection period Tk. Consequently, the dark current value of the light detector <NUM> can be further reduced. As a result, since the detection accuracy of the light detector <NUM> can be improved, it is possible to suppress deterioration in detection accuracy of the light detecting device <NUM>.

The EC controller <NUM> controls drive of the electronic cooler <NUM> in response to a drive signal SG3. Accordingly, the EC controller <NUM> controls the cooling capacity at the heat absorption surface <NUM> of the electronic cooler <NUM> in response to the drive signal SG3. The cooling capacity of the electronic cooler <NUM> is adjusted by a drive power (drive current) supplied to the electronic cooler <NUM> to drive the electronic cooler <NUM>. Hence, the "cooling capacity of the electronic cooler <NUM>" can be described in place of the "drive power of the electronic cooler <NUM>".

The EC controller <NUM> adjusts the drive power of the electronic cooler <NUM> in response to the drive signal SG3. The "drive power of the electronic cooler <NUM>" means a magnitude of the power supplied from the power source to the electronic cooler <NUM>. This drive power can be described in place of a drive voltage or a drive current. The drive signal SG3 is, for example, a pulse signal including a high-level state (ON state) and a low-level state (OFF state). More specifically, the drive signal SG3 is, for example, a pulse width modulation (PWM) signal (PWM control). The drive signal SG3 is not limited to the PWM signal and may be the amplitude modulation (AM) signal. When the drive signal SG3 enters into the ON state, the electronic cooler <NUM> enters into an energized state. On the other hand, when the drive signal SG3 enters into the OFF state, the electronic cooler <NUM> enters into a non-energized state. The drive power of the electronic cooler <NUM> is determined according to a duty cycle of the drive signal SG3. Specifically, as the duty cycle of the drive signal SG3 increases, the drive power of the electronic cooler <NUM> increases. On the other hand, as the duty cycle of the drive signal SG3 decreases, the drive power of the electronic cooler <NUM> decreases.

The EC controller <NUM> sets the duty cycle of the drive signal SG3 to be always larger than <NUM>%. That is, the EC controller <NUM> performs control such that power (that is, power in a range of a drive power larger than zero) suitable for driving the electronic cooler <NUM> is continuously supplied as a drive power <NUM> to the electronic cooler <NUM>. Therefore, the electronic cooler <NUM> is continuously driven in the entire period including the standby period Tt and the detection period Tk. Hence, the cooling of the light detector <NUM> by the electronic cooler <NUM> is continued also in the detection period Tk. Here, since the drive of both the pump <NUM> and the fan <NUM> is stopped in the detection period Tk, there is a possibility that the temperature of the light detector <NUM> may increase, as time elapses, and exceed a temperature HL (first allowable temperature) in a case where the duty cycle of the drive signal SG3 is made constant (that is, in a case where the drive power of the electronic cooler <NUM> is made constant). The temperature HL means an upper limit value of a temperature range in which a dark current generated in the light detector <NUM> can be tolerated. Since a magnitude of the dark current depends on a temperature of the light detector <NUM>, an allowable temperature range of the light detector <NUM> can be determined based on an allowable range of dark current values. The electronic cooler <NUM> is not limited to being constantly driven and may be intermittently driven as long as an allowable temperature range of the light detector <NUM> can be maintained.

The dark current value varies depending on the type of light detector <NUM> and also varies depending on an individual difference of the light detector <NUM>. The dark current value may be a fixed value obtained with reference to the specifications of the light detector <NUM> or may be an actually measured value obtained by measurement of the light detector <NUM>. When the dark current value is obtained by measurement, a current value output from the light detector <NUM> in a background measurement (that is, measurement in a state where the measurement light L is not incident on the light detector <NUM>) is defined as the dark current value. The dark current value may be calculated before the light detection by the light detector <NUM> or may be periodically calculated at regular intervals. When the dark current value is calculated every certain period, the same dark current value may be used during the certain period.

If the temperature of the light detector <NUM> becomes so high as to exceed the temperature HL, the dark current excessively increases, and there is a possibility that the detection accuracy of the light detecting device <NUM> may be significantly affected. In this respect, the EC controller <NUM> monitors the temperature of the light detector <NUM> in response to the signal H1 from the first sensor <NUM> and performs feedback control on the duty cycle of the drive signal SG3 so that the temperature of the light detector <NUM> becomes equal to or lower than the temperature HL. The feedback control is, for example, proportional integral differential (PID) control. The feedback control may be performed by ON/OFF control.

The EC controller <NUM> controls the drive power <NUM> at a time t1 to be larger than drive power <NUM> at a time t2 before the time t1 in the detection period Tk by the feedback control of the drive signal SG3. In the embodiment, the EC controller <NUM> performs control such that a pulse width of the drive signal SG3 at the time t1 is larger than a pulse width of the drive signal SG3 at the time t2 before the time t1. In this case, in the detection period Tk, the drive power <NUM> of the electronic cooler <NUM> increases as time elapses, and the cooling effect of the light detector <NUM> by the electronic cooler <NUM> is enhanced as time elapses. By performing the feedback control of the electronic cooler <NUM>, the EC controller <NUM> can maintain the temperature of the light detector <NUM> constant within a range of the temperature HL or less as illustrated by the signal H1 in <FIG>. As in the embodiment, the drive power <NUM> at the time t1 may not be controlled to be larger than the drive power <NUM> at the time t2 before the time t1 by the pulse width of the drive signal SG3. For example, by continuously changing the drive signal SG3 linearly or curvilinearly, the drive power <NUM> at the time t1 may be controlled to be larger than the drive power <NUM> at the time t2 before the time t1.

In the standby period Tt, all of the pump <NUM>, the fan <NUM>, and the electronic cooler <NUM> are driven. On the other hand, in the detection period Tk, the drive of the electronic cooler <NUM> is continued, but the drive of both the pump <NUM> and the fan <NUM> is stopped. That is, the electronic cooler <NUM> is driven in a state where heat dissipation to the coolant R is not sufficiently performed. However, as described above, since the magnitude of the heat capacity of the coolant R itself can be used, heat exchange is continued between the coolant R and the heat exchanger <NUM>, and heat dissipation of the heat sink <NUM> is continued. Therefore, in the detection period Tk, the temperature of the heat exchanger <NUM> does not increase rapidly even if the drive of the electronic cooler <NUM> continues. However, as illustrated by the signal H2 in <FIG>, in the detection period Tk, the temperature of the heat exchanger <NUM> increases as time elapses, and there is a possibility that the temperature may eventually become very high.

In this respect, from the viewpoint of ensuring safety, the PF controller <NUM> monitors the temperature of the heat exchanger <NUM> in response to the signal H2 from the second sensor <NUM> at least in the detection period Tk (in the embodiment, the entire period including the standby period Tt and the detection period Tk) and drives the pump <NUM> and the fan <NUM> when the temperature of the heat exchanger <NUM> exceeds a temperature HE (second allowable temperature). Consequently, the PF controller <NUM> performs heat dissipation of the coolant R by the pump <NUM> and the fan <NUM> and restarts the heat dissipation of the heat exchanger <NUM> by the coolant R. The temperature HE here means an upper limit value of a temperature range of the heat exchanger <NUM> that can be tolerated from the viewpoint of ensuring safety. The allowable temperature range of the heat exchanger <NUM> from the viewpoint of ensuring safety is a temperature range in which a user can safely handle the light detecting device <NUM>.

The PF controller <NUM> determines whether or not the temperature of the heat exchanger <NUM> exceeds the temperature HE throughout the standby period Tt and the detection period Tk. When determining that the temperature of the heat exchanger <NUM> does not exceed the temperature HE in the detection period Tk, the PF controller <NUM> causes the pump <NUM> and the fan <NUM> to enter into a stopped state. On the other hand, when determining that the temperature of the heat exchanger <NUM> exceeds the temperature HE, the PF controller <NUM> drives the pump <NUM> and the fan <NUM>. The EC controller <NUM> may also determine whether or not the temperature of the heat exchanger <NUM> exceeds the temperature HE through the standby period Tt and the detection period Tk. In this case, the EC controller <NUM> may continue driving the electronic cooler <NUM> when determining that the temperature of the heat exchanger <NUM> does not exceed the temperature HE in the detection period Tk. On the other hand, when the EC controller <NUM> determines that the temperature of the heat exchanger <NUM> exceeds the temperature HE, the EC controller may stop driving the electronic cooler <NUM> or reduce the drive power <NUM> to suppress heat transfer from the electronic cooler <NUM> to the heat exchanger <NUM>.

Specifically, the PF controller <NUM> changes the drive power of the pump <NUM> from the drive power <NUM> to a drive power <NUM> (sixth drive power) larger than the drive power <NUM>. The drive power <NUM> may be, for example, the same as the drive power <NUM> in the standby period Tt. The PF controller <NUM> changes the drive power of the fan <NUM> from the drive power <NUM> to drive power larger than the drive power <NUM>, for example, the drive power <NUM> of the fan <NUM> in the standby period Tt. As described above, when it is determined that the temperature of the heat exchanger <NUM> exceeds the temperature HE, the PF controller <NUM> switches the pump <NUM> and the fan <NUM> from the stopped state to the normal driving state, thereby performing heat dissipation of the heat exchanger <NUM> so that the temperature of the heat exchanger <NUM> does not exceed the temperature HE. The detection period Tk may be adjusted such that the time point at which the light detector <NUM> ends the light detection is a time point immediately before the temperature of the heat exchanger <NUM> exceeds the temperature HE. In this case, the light detector <NUM> can perform the light detection while the pump <NUM> and the fan <NUM> are maintained in the stopped state.

subsequently, a control method of the control unit <NUM> will be described with further reference to <FIG> is a flowchart illustrating a control flow of the control unit <NUM>.

As illustrated in <FIG>, first, in the standby period Tt, the PF controller <NUM> and the EC controller <NUM> drive the pump <NUM>, the fan <NUM>, and the electronic cooler <NUM> (Step S1). Specifically, the PF controller <NUM> drives the pump <NUM> with the drive power <NUM> based on the drive signal SG1 and drives the fan <NUM> with the drive power <NUM> based on the drive signal SG2. Further, the EC controller <NUM> drives the electronic cooler <NUM> with the drive power <NUM> based on the drive signal SG3. In the standby period Tt, the pump <NUM>, the fan <NUM>, and the electronic cooler <NUM> are all normally driven so that the cooling effect of the light detector <NUM> by the coolant R is sufficiently exerted.

Next, the PF controller <NUM> and the EC controller <NUM> determine whether or not the trigger signal TG in the ON state is input (Step S2). Specifically, the PF controller <NUM> and the EC controller <NUM> determine whether or not the light detector <NUM> has started light detection (that is, whether or not the process has been executed from the standby period Tt to the detection period Tk) by determining whether or not the trigger signal TG has been switched from the OFF state to the ON state. When the PF controller <NUM> and the EC controller <NUM> determine that the trigger signal TG in the ON state is not input (No in Step S2), the controllers continuously drive the pump <NUM>, the fan <NUM>, and the electronic cooler <NUM>. On the other hand, when the PF controller <NUM> and the EC controller <NUM> determine that the trigger signal TG in the ON state is input (Yes in Step S2), the controllers stop driving the pump <NUM> and the fan <NUM> (Step S3). Even at that time, the EC controller <NUM> continues driving the electronic cooler <NUM>. The PF controller <NUM> stops driving the pump <NUM> and the fan <NUM> by setting the duty cycles of the drive signals SG1 and SG2 to <NUM>% at the timing of shifting from the standby period Tt to the detection period Tk. Hence, in the detection period Tk, the drive of the pump <NUM> and the fan <NUM> is stopped.

Next, the PF controller <NUM> acquires the signal H1 and performs PID control on drive of the electronic cooler <NUM> based on the signal H1 (Step S4). Specifically, the EC controller <NUM> monitors the temperature of the light detector <NUM> in response to the signal H1 from the first sensor <NUM> and performs feedback control on the duty cycle of the drive signal SG3 so that the temperature of the light detector <NUM> becomes equal to or lower than the temperature HL.

Next, the PF controller <NUM> determines whether or not the signal H2 indicates a temperature equal to or lower than a predetermined temperature (Step S5). Specifically, the PF controller <NUM> determines whether the signal H2 indicates that the temperature of the heat exchanger <NUM> does not exceed the temperature HE as a result of the PID control of the electronic cooler <NUM> in Step S4. In a case where the PF controller <NUM> determines that the signal H2 does not indicate a temperature equal to or lower than the predetermined temperature (No in Step S5), the process proceeds to Step <NUM>, and in a case where the PF controller <NUM> determines that the signal H2 indicates a temperature equal to or lower than the predetermined temperature (Yes in Step S5), the process proceeds to Step S6. Next, the PF controller <NUM> and the EC controller <NUM> determine whether or not the trigger signal TG in the OFF state is input (Step S6). Specifically, the PF controller <NUM> and the EC controller <NUM> determine whether or not the light detector <NUM> ends the light detection (that is, whether or not the process has been executed from the detection period Tk to the standby period Tt) by determining whether or not the trigger signal TG has been switched from the ON state to the OFF state. When the PF controller <NUM> and the EC controller <NUM> determine that the trigger signal TG in the OFF state is not input (No in Step S6), the controllers continuously acquire the signal H1. Accordingly, the EC controller <NUM> performs PID control on drive of the electronic cooler <NUM> based on the signal H1 (Step S4). On the other hand, when the PF controller <NUM> and the EC controller <NUM> determine that the trigger signal TG in the OFF state is input (Yes in Step S6), the controllers restart the drive of the pump <NUM> and the fan <NUM> (Step S7). At that time, the EC controller <NUM> continues driving the electronic cooler <NUM>.

Functions and effects obtained by the light detecting device <NUM> and the method for controlling the light detecting device <NUM> according to the embodiments described above will be described. In the embodiments, the coolant R delivered by the pump <NUM> and reaching the heat exchanger <NUM> exchanges heat with the light detector <NUM> via the heat exchanger <NUM> to cool the light detector <NUM>. Here, during the detection period Tk, the drive power <NUM> of the pump <NUM> is set to <NUM>. Therefore, during the detection period Tk, the operation of the pump <NUM> at the time of delivering the coolant R is stopped. Accordingly, vibration caused by the pulsation that may occur in the flow of the coolant R is also stopped. Further, since the drive power <NUM> of the fan <NUM> is also set to <NUM> during the detection period Tk, the mechanical vibration of the fan <NUM> itself is also stopped. That is, the vibration transmitted to the light detector <NUM> during the detection period Tk is smaller than the vibration transmitted to the light detector <NUM> during the standby period Tt. As an example illustrating the influence of vibration, a vibration value VL in <FIG> indicates a vibration value transmitted to the light detector <NUM>. As illustrated by the vibration value VL in <FIG>, it can be found that the vibration value VL is substantially zero during the detection period Tk. Consequently, it is possible to suppress deterioration in detection accuracy of the light detecting device <NUM> due to transmission of vibration.

Further, as described above, the magnitude of the heat capacity of the coolant R itself can be used by using the coolant R. Therefore, even if the drive power <NUM> of the pump <NUM> and the drive power <NUM> of the fan <NUM> are set to <NUM> during the detection period Tk, the heat from the heat exchanger <NUM> can be absorbed using the heat capacity of the coolant R itself. Therefore, it is possible to maintain the cooling effect of the light detector <NUM> by the coolant R even during the detection period Tk, and it is possible to suppress deterioration in detection accuracy of the light detecting device <NUM> due to an increase in temperature of the light detector <NUM>.

As in the embodiment, the light detecting device <NUM> may include the electronic cooler <NUM>. In this case, since the light detector <NUM> can be efficiently cooled by the electronic cooler <NUM>, the increase in temperature of the light detector <NUM> can be more reliably suppressed. Further, since the temperature of the light detector <NUM> can be lowered to a temperature lower than the temperature of the coolant R by the electronic cooler <NUM> that actively performs cooling, the dark current value of the light detector <NUM> can be further reduced. As a result, since the detection accuracy of the light detector <NUM> can be improved, it is possible to suppress deterioration in detection accuracy of the light detecting device <NUM>.

As in the embodiment, the EC controller <NUM> may continuously drive the electronic cooler <NUM> during the detection period Tk. In this case, during the detection period Tk, the light detector <NUM> can be continuously cooled by driving the electronic cooler <NUM>. On the other hand, the heat transferred to the heat exchanger <NUM> by the driving of the electronic cooler <NUM> dissipates to the coolant R. However, as described above, since the magnitude of the heat capacity of the coolant R itself can be used, the cooling effect of the light detector <NUM> by the coolant R can be maintained. Hence, according to the configuration described above, it is possible to more reliably suppress the increase in temperature of the light detector <NUM> while suppressing the transmission of the vibration derived from the pulsation by cooling the light detector <NUM> by the electronic cooler <NUM> and the coolant R. As a result, it is possible to more reliably suppress deterioration in detection accuracy of the light detecting device <NUM>.

As in the embodiment, the EC controller <NUM> may set the drive power <NUM> of the electronic cooler <NUM> so that the temperature of the light detector <NUM> becomes equal to or lower than the temperature HL during the detection period Tk. In this case, it is possible to suppress an undesired increase in temperature in the light detecting device <NUM> by detecting the temperature of the light detector <NUM> and accordingly supplying the drive power <NUM>.

As in the embodiment, the EC controller <NUM> may perform control such that the drive power <NUM> at the time t1 is larger than the drive power <NUM> at the time t2 before the time t1 during the detection period Tk. During the detection period Tk, when the drive power <NUM> of the pump <NUM> and the drive power <NUM> of the fan <NUM> are set to <NUM>, the temperature of the light detector <NUM> may gradually increase. In this respect, the cooling effect of the light detector <NUM> by the electronic cooler <NUM> at the time t1 after the time t2 can be enhanced as time elapses by controlling the third drive power signal to be large at the time t2 before the time t1. Consequently, it is possible to suppress a situation in which the temperature of the light detector <NUM> increases. As a result, it is possible to more reliably suppress deterioration in detection accuracy of the light detecting device <NUM> due to an increase in temperature of the light detector <NUM>.

As in the embodiment, the fan <NUM> may blow air toward the radiator <NUM>. In this case, heat dissipation of the coolant R is performed by the radiator <NUM> and the fan <NUM> so that the cooling effect of the light detector <NUM> by the coolant R can be further enhanced.

As in the embodiment, the PF controller <NUM> may restart driving the pump <NUM> and the fan <NUM> when the temperature of the heat exchanger <NUM> exceeds the temperature HE during the detection period Tk. The heat exchanger <NUM> is particularly likely to have a high temperature because the heat of the light detector <NUM> dissipates. In this respect, when the temperature of the heat exchanger <NUM> becomes so high as to exceed the temperature HE, it is possible to suppress a situation in which the heat exchanger <NUM> becomes too high in temperature by restarting the driving of the pump <NUM> and the fan <NUM>. As a result, it is possible to improve safety when the light detecting device <NUM> is used.

In the embodiment, the PF controller <NUM> drives the pump <NUM> and the fan <NUM> when the temperature of the heat exchanger <NUM> exceeds the temperature HE. However, the PF controller <NUM> may drive the pump <NUM> and the fan <NUM> when the temperature of the light detector <NUM> exceeds the temperature HE. In this case, when the temperature of the light detector <NUM> becomes high, the coolant R can cool the light detector <NUM> by driving the pump <NUM> and the fan <NUM>.

The light detecting device and the method for controlling the light detecting device of the present disclosure are not limited to the above-described embodiments. In the light detecting device and the method for controlling the light detecting device of the present disclosure, specific aspects may be appropriately changed without departing from the gist of CLAIMS.

<FIG> is a timing chart illustrating a first modification example of each signal processed by the control unit <NUM>. In the embodiment described above, a case where the drive of the pump <NUM> and the fan <NUM> is stopped during the detection period Tk has been described. However, in the modification example, a case where the drive of the pump <NUM> and the fan <NUM> is continued during a detection period TkA will be described.

In the modification example, as illustrated in <FIG>, when the PF controller <NUM> adjusts a duty cycle (that is, the drive power of the pump <NUM>) of a drive signal SG1A for controlling the drive of the pump <NUM>, the PF controller <NUM> controls the duty cycle of the drive signal SG1A during the detection period TkA to be larger than <NUM>% and smaller than the duty cycle of the drive signal SG1A during a standby period TtA. That is, the PF controller <NUM> controls the drive power <NUM> (first drive power) of the pump <NUM> during the detection period TkA to be within a range of the drive power larger than <NUM> and smaller than the drive power <NUM> (second drive power) of the pump <NUM> during the standby period TtA. For example, the PF controller <NUM> may set the duty cycle of the drive signal SG1A during the detection period TkA to be within a range of the duty cycle larger than <NUM>% and equal to or smaller than <NUM>% of the duty cycle of the drive signal SG1A during the standby period TtA.

In the example illustrated in <FIG>, the PF controller <NUM> sets the duty cycle of the drive signal SG1A during the standby period TtA to <NUM>% and sets the duty cycle of the drive signal SG1A during the detection period TkA to <NUM>%. In this case, during the detection period TkA, the pump <NUM> is driven with the drive power <NUM> corresponding to <NUM>% of the duty cycle of the drive signal SG1A. As described above, the drive power <NUM> of the pump <NUM> during the detection period TkA is significantly reduced as compared with the drive power <NUM> of the pump <NUM> during the standby period TtA.

Similarly, when the PF controller <NUM> adjusts the duty cycle (that is, the drive power of the fan <NUM>) of a drive signal SG2A for controlling the drive of the fan <NUM>, the PF controller <NUM> controls the duty cycle of the drive signal SG2A during the detection period TkA to be within a range of the duty cycle larger than <NUM>% and smaller than the duty cycle of the drive signal SG2A during a standby period TtA. For example, the PF controller <NUM> may set the duty cycle of the drive signal SG2A during the detection period TkA to be within a range of the duty cycle larger than <NUM>% and equal to or smaller than <NUM>% of the duty cycle of the drive signal SG2A during the standby period TtA.

When the PF controller <NUM> adjusts the duty cycle (that is, the drive power of the fan <NUM>) of the drive signal SG2A for controlling the drive of the fan <NUM>, the PF controller <NUM> controls the duty cycle of the drive signal SG2A during the detection period TkA to be within a range of the duty cycle larger than <NUM>% and smaller than the duty cycle of the drive signal SG2A during a standby period TtA. That is, the PF controller <NUM> controls the drive power <NUM> (fourth drive power) of the fan <NUM> during the detection period TkA to be in a range of the drive power larger than <NUM> and smaller than the drive power <NUM> (fifth drive power) of the fan <NUM> during the standby period TtA. As illustrated in the example of <FIG>, similarly to the drive signal SG1A, the PF controller <NUM> performs control such that the duty cycle of the drive signal SG2A during the standby period TtA to <NUM>% and sets the duty cycle of the drive signal SG2A during the detection period TkA to <NUM>%. In this case, during the detection period TkA, the fan <NUM> is driven with the drive power <NUM> corresponding to <NUM>% of the duty cycle of the drive signal SG2A. As described above, the drive power <NUM> of the fan <NUM> during the detection period TkA is more significantly reduced than the drive power <NUM> of the fan <NUM> during the standby period TtA.

Hence, during the detection period TkA, both the pump <NUM> and the fan <NUM> continue to be driven with a drive power smaller than the drive power during the standby period TtA. As described above, when the drive of the pump <NUM> and the fan <NUM> is continued during the detection period TkA, the heat dissipation effect with respect to the coolant R is enhanced as compared with the case where the drive of the pump <NUM> and the fan <NUM> is stopped as in the embodiment described above, and thus, the cooling effect of the light detector <NUM> by the coolant R is enhanced. Therefore, the temperature of the light detector <NUM> is less likely to increase during the detection period TkA. Accordingly, when the duty cycle (that is, the drive power of the electronic cooler <NUM>) of a drive signal SG3A for driving the electronic cooler <NUM> is controlled, an increase width of the duty cycle of the drive signal SG3A during the detection period TkA decreases more than an increase width (see <FIG>) of the duty cycle of the drive signal SG3 during the detection period Tk according to the embodiment described above.

That is, during the detection period TkA, the temperature of the light detector <NUM> can be maintained constant in a range of the temperature HL or less as illustrated in a signal H1A of <FIG> without a rapidly increase in drive power of the electronic cooler <NUM>. Further, as illustrated by a signal H2A in <FIG>, during the detection period TkA, the temperature of the heat exchanger <NUM> increases more slowly. That is, during the detection period TkA, as compared with an increase in temperature of the heat exchanger <NUM> during the detection period Tk according to the embodiment described above (see the signal H2 in <FIG>), it takes a longer time until the temperature of the heat exchanger <NUM> reaches a certain temperature. As described above, since the temperatures of the light detector <NUM> and the heat exchanger <NUM> hardly increase during the detection period TkA, it is possible to secure a longer time until the light detector <NUM> and the heat exchanger <NUM> reach the respective temperatures HL and HE. As a result, a longer detection period TkA can be secured than the detection period Tk according to the embodiment described above.

In the modification example, since the pump <NUM> and the fan <NUM> continue to be driven during the detection period TkA, it is possible to suppress a situation in which the heat dissipation effect with respect to the coolant R decreases. That is, it is possible to suppress a situation in which the cooling effect of the light detector <NUM> by the coolant R is reduced. As a result, it is possible to more reliably suppress the increase in temperature of the light detector <NUM> and accordingly the increase in dark current, and thus it is possible to more reliably suppress deterioration in detection accuracy of the light detecting device <NUM> due to the increase in dark current. Further, since the pump <NUM> and the fan <NUM> during the detection period TkA are driven with the drive power significantly reduced as compared with that during the standby period TtA, the vibration caused by the drive of the pump <NUM> and the fan <NUM> is also significantly reduced accordingly. As illustrated by a vibration value VLA in <FIG>, it can be found that the vibration value VLA is significantly smaller during the detection period TkA than during the standby period TtA. Hence, the influence of the vibration caused by the drive of the pump <NUM> and the fan <NUM> on the detection accuracy of the light detecting device <NUM> can be reduced. That is, it is possible to suppress deterioration in detection accuracy of the light detecting device <NUM> due to transmission of the vibration. Further, in the modification example, as described above, the temperatures of the light detector <NUM> and the heat exchanger <NUM> are less likely to increase so that a long detection period TkA can be secured. That is, the light detection of the light detector <NUM> can be performed over a longer period.

<FIG> is a timing chart illustrating a second modification example of each signal processed by the control unit <NUM>. In the embodiment described above, a case where the drive of the pump <NUM> and the fan <NUM> is controlled by the PWM control, and the drive of the pump <NUM> and the fan <NUM> is stopped during the detection period Tk has been described. However, in the modification example, a case where the drive of the pump <NUM> and the fan <NUM> is controlled by constant voltage control (linear control), and the pump <NUM> and the fan <NUM> are stopped during a detection period TkB will be described.

In the modification example, the PF controller <NUM> controls the supply of the drive power so that a voltage supplied to the pump <NUM> becomes constant. Similarly, the PF controller <NUM> controls the supply of the drive power so that the voltage supplied to the fan <NUM> becomes constant. The PF controller <NUM> adjusts a drive voltage of the pump <NUM> in response to a drive signal SG1B. The PF controller <NUM> controls the drive signal SG1B to maintain a drive voltage <NUM> (second drive power) of the pump <NUM> to be constant (for example, <NUM> V) during a standby period TtB and maintain a drive voltage <NUM> (first drive power) of the pump <NUM> at <NUM> during the detection period TkB. The PF controller <NUM> adjusts the drive voltage of the fan <NUM> in response to the drive signal SG2B. Similarly to the drive signal SG1B, the PF controller <NUM> controls a drive signal SG2B to maintain a drive voltage <NUM> (fifth drive power) of the fan <NUM> to be constant (for example, <NUM> V) during the standby period TtB and maintain a drive voltage <NUM> (fourth drive power) of the fan <NUM> at <NUM> during the detection period TkB.

Hence, in the modification example, similarly to the embodiment described above, the drive of both the pump <NUM> and the fan <NUM> is stopped during the detection period TkB. Further, in the modification example, similarly to the embodiment described above, the EC controller <NUM> performs control to drive the electronic cooler <NUM> by the PWM control during the detection period TkB. Accordingly, the EC controller <NUM> performs the feedback control on the duty cycle of a drive signal SG3B so that the temperature of the light detector <NUM> becomes equal to or lower than the temperature HL. As a result, during the detection period TkB, the drive power of the electronic cooler <NUM> is controlled to increase as time elapses. The EC controller <NUM> can maintain the temperature of the light detector <NUM> constant within a range of the temperature HL or less as illustrated by a signal H1B in <FIG> by performing the feedback control on the electronic cooler <NUM>. On the other hand, as illustrated by a signal H2B in <FIG>, during the detection period TkB, the temperature of the heat exchanger <NUM> increases in a range in which the temperature does not exceed the temperature HE as time elapses.

Also in the modification example, since the drive of the pump <NUM> and the fan <NUM> is stopped during the detection period TkB, it can be found that a vibration value VLB is substantially <NUM> during the detection period TkB as illustrated by the vibration value VLB of <FIG>. Hence, also in the modification example, similarly to the embodiment described above, it is possible to suppress deterioration in detection accuracy of the light detecting device <NUM> due to transmission of vibration.

<FIG> is a timing chart illustrating a third modification example of each signal processed by the control unit <NUM>. In the embodiment described above, a case where the drive of the pump <NUM> and the fan <NUM> is controlled by the PWM control, and the drive of the pump <NUM> and the fan <NUM> is stopped during the detection period Tk has been described. However, in the modification example, a case where the drive of the pump <NUM> and the fan <NUM> is controlled by the constant voltage control (linear control), and the drive of the pump <NUM> and the fan <NUM> is continued during a detection period TkC will be described.

In the modification example, the PF controller <NUM> controls the supply of the drive power so that a voltage supplied to the pump <NUM> becomes constant. Similarly, the PF controller <NUM> controls the supply of the drive power so that the voltage supplied to the fan <NUM> becomes constant. The PF controller <NUM> adjusts a drive voltage of the pump <NUM> in response to a drive signal SG1C. The PF controller <NUM> controls the drive signal SG1C to maintain the drive voltage <NUM> (second drive power) of the pump <NUM> constant (for example, <NUM> V) during a standby period TtC and maintain the drive voltage <NUM> (first drive power) of the pump <NUM> during the detection period TkC at a voltage (for example, <NUM> V) larger than <NUM> and smaller than the constant voltage. The PF controller <NUM> adjusts the drive voltage of the fan <NUM> in response to the drive signal SG2C. Similarly to the drive signal SG1C, the PF controller <NUM> controls the drive signal SG2C to maintain the drive voltage <NUM> (fifth drive power) of the fan <NUM> at a constant voltage (for example, <NUM> V) during the standby period TtC and maintain the drive voltage <NUM> (fourth drive power) of the fan <NUM> during the detection period TkC at a voltage (for example, <NUM> V) larger than <NUM> and smaller than the constant voltage.

Hence, in the modification example, during the detection period TkC, the drive voltages of the pump <NUM> and the fan <NUM> are significantly reduced as compared with the standby period TtC. Accordingly, similarly to the first modification example described above, since the temperature of the light detector <NUM> is less likely to increase during the detection period TkC, an increase width of a duty cycle of a drive signal SG3C during the detection period TkC is smaller than an increase width (see <FIG>) of the duty cycle of the drive signal SG3 during the detection period Tk according to the embodiment described above. That is, during the detection period TkC, even when a drive voltage <NUM> (third drive power) of the electronic cooler <NUM> is not rapidly increased, the temperature of the light detector <NUM> can be maintained constant within a range of the temperature HL or less as illustrated by a signal H1C of <FIG>.

Further, as illustrated by a signal H2C in <FIG>, during the detection period TkC, the temperature of the heat exchanger <NUM> increases more slowly. That is, during the detection period TkC, as compared with an increase in temperature of the heat exchanger <NUM> during the detection period Tk according to the embodiment described above (see the signal H2 in <FIG>), it takes a longer time until the temperature of the heat exchanger <NUM> reaches a certain temperature. As described above, since the temperatures of the light detector <NUM> and the heat exchanger <NUM> hardly increase during the detection period TkC, it is possible to secure a longer time until the light detector <NUM> and the heat exchanger <NUM> reach the respective temperatures HL and HE. As a result, a longer detection period TkC can be secured than the detection period Tk according to the embodiment described above.

In the modification example, since the pump <NUM> and the fan <NUM> continue to be driven during the detection period TkC, it is possible to obtain the same effect as that of the first modification example described above. That is, it is possible to more reliably suppress the increase in temperature of the light detector <NUM> and accordingly the increase in dark current, and thus it is possible to more reliably suppress deterioration in detection accuracy of the light detecting device <NUM> due to the increase in dark current. Further, since the pump <NUM> and the fan <NUM> during the detection period TkC are driven with the drive voltage significantly reduced as compared with that during the standby period TtC, the vibration caused by the drive of the pump <NUM> and the fan <NUM> is also significantly reduced accordingly. As illustrated by a vibration value VLC in <FIG>, it can be found that the vibration value VLC is significantly smaller during the detection period TkC than during the standby period TtC. Consequently, the influence of the vibration caused by the drive of the pump <NUM> and the fan <NUM> on the detection accuracy of the light detecting device <NUM> can be reduced. That is, it is possible to suppress deterioration in detection accuracy of the light detecting device <NUM> due to transmission of the vibration. Further, in the modification example, as described above, the temperatures of the light detector <NUM> and the heat exchanger <NUM> increase more slowly so that a long detection period TkC can be secured. That is, the light detection of the light detector <NUM> can be performed over a longer period.

<FIG> is a timing chart illustrating a fourth modification example of each signal processed by the control unit <NUM> of the light detecting device <NUM>. In the embodiment described above, the case where the drive of the electronic cooler <NUM> is controlled by the PWM control has been described. On the other hand, as in the modification example, the drive of the electronic cooler <NUM> may be controlled by constant current control (linear control) (drive signal SG3D).

The light detecting device and the method for controlling the light detecting device of the present disclosure are not limited to the embodiments and the modification examples described above and can be modified in various other manners. For example, the embodiments and the modification examples described above may be combined with each other according to a necessary purpose and effect. In the embodiments and the modification examples described above, the case where the waveform of the drive signal for controlling the drive of the pump and the waveform of the drive signal for controlling the drive of the fan are the same has been described. However, the waveforms of these drive signals may be different from each other.

In the embodiments, the second modification example, and the fourth modification example described above, there is no need to stop driving of both the pump and the fan during the detection period, only the drive of the pump may be stopped, and the drive of the fan may be continued. In the first modification example and the third modification example described above, there is no need to significantly reduce the drive power of both the pump and the fan during the detection period, and only the drive power of the pump may be significantly reduced without reducing the drive power of the fan. In this case, the fan may be normally driven. Since the fan is disposed at a position separated from the light detector, the vibration of the fan is hardly transmitted to the light detector even when the fan is normally driven, and the influence of the vibration of the fan on the detection accuracy of the light detecting device may be small. Therefore, in the embodiment and the modification examples described above, the case where the drive power supplied to the fan during the detection period is smaller than the drive power supplied to the fan during the standby period has been described. However, when the fan is disposed to be sufficiently separated from the light detector, the drive power supplied to the fan during the detection period may be set to be larger than the drive power supplied to the fan during the standby period. As a result, the heat dissipation efficiency of the coolant in the coolant flow channel can be enhanced, and deterioration in detection accuracy of the light detecting device due to an increase in temperature of the light detector can be suppressed.

Claim 1:
A light detecting device comprising:
a light detector;
a heat exchanger thermally connected to the light detector;
a coolant flow channel configured to be connected to the heat exchanger and allow a coolant for cooling the light detector to flow;
a pump configured to cause the coolant to flow in the coolant flow channel; and
a control unit configured to control the pump, wherein
the control unit performs control such that
a first drive power is supplied to the pump during a detection period in which the light detector performs light detection, and
a second drive power is supplied to the pump during a standby period in which the light detector stands by without performing light detection, and
the first drive power is smaller than the second drive power.