JP2014095670A - Optical sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical sensor suppressed in an increase in configuration.SOLUTION: An optical sensor having a photoelectric conversion element (10) for storing photo-electrically converted charges is configured to output a detection signal corresponding to charge amounts photo-electrically converted in a first predetermined time. The optical sensor includes: a power storage unit (20) for storing the photo-electrically converted charges; and a control part (30) for controlling the power storage unit. The power storage unit includes: an electronic element (21) for storing charges; and a switch (22), and the electronic element and the switch are serially connected between the photoelectric conversion element and a ground. The control part includes: a non-volatile memory (31) in which a relation between a switch which is put in an ON state and a capacitance to be determined by the electronic element and the photo-electric conversion element serially connected to the switch put in the ON state is recorded; and a signal generation part (32) for outputting an ON signal on the basis of the relation between the switch put in the ON state and the capacitance recorded in the non-volatile memory.

Description

  The present invention relates to an optical sensor having a photoelectric conversion element that stores a photoelectrically converted charge.

  Conventionally, as shown in Patent Document 1, for example, a light receiving element that generates a photocurrent according to the amount of light, a preprocessing circuit that generates a plurality of signals proportional to the photocurrent, and the generated signal are adapted to the control There has been proposed an optical sensor including a plurality of processing circuits that convert to a possible signal form and output. In this optical sensor, a detection signal adaptable to the control content is output in each of the plurality of processing circuits.

Japanese Patent Laid-Open No. 10-30960

  As described above, the optical sensor described in Patent Document 1 outputs a plurality of detection signals that can be adapted to the control content by variously processing the output signal of one light receiving element. In contrast, an optical sensor that outputs a plurality of detection signals having different detection sensitivities by amplifying the output signal of one light receiving element (photoelectric conversion element) in various ways is also conceivable. As the configuration, for example, an optical sensor having a photoelectric conversion element, a unit that amplifies an output signal of the photoelectric conversion element, and a control unit that controls the unit can be considered. This unit has an amplifier and a switch. When this switch is ON / OFF controlled by the control unit, one of a plurality of detection signals having different detection sensitivities is output. Thereby, the detection sensitivity is variable. By the way, the amplifier is composed of a plurality of electronic elements. Therefore, there is a concern that the physique of the optical sensor increases.

  In view of the above problems, an object of the present invention is to provide an optical sensor in which an increase in physique is suppressed.

  In order to achieve the above-described object, the present invention has a photoelectric conversion element (10) that photoelectrically converts received light and stores the photoelectrically converted charges, and has a charge amount photoelectrically converted in a first predetermined time. An optical sensor that outputs a corresponding detection signal, and includes a power storage unit (20) for storing the charge converted by the photoelectric conversion element, and a control unit (30) for controlling the power storage unit, The power storage unit includes an electronic element (21) that stores electric charge and a switch (22), and the electronic element and the switch are connected in series between a ground-side terminal of the photoelectric conversion element and the ground. Includes a non-volatile memory (31) in which a relationship between the switch to be turned on, the capacitance determined by the photoelectric conversion element and the electronic element connected in series with the switch in the on state, and non-volatile In memory Based on the relationship between the switch and the capacitance of the recording has been turned ON, the switch, and having a signal generator for outputting an ON signal to the switch to the ON state (32).

  The larger the capacitance determined by the electronic element (21) (hereinafter referred to as the selection element (21a)) connected in series with the switch (22) in the ON state and the photoelectric conversion element (10), the larger the photosensor. The change rate of the voltage of the detection signal output from (100) (hereinafter referred to as the detection voltage) becomes slow. Therefore, the detection sensitivity becomes insensitive. On the contrary, the smaller the capacitance, the faster the change rate of the detection voltage. Therefore, the detection sensitivity becomes sensitive.

  On the other hand, in the present invention, the capacitance is determined by determining the selection element (21a) by ON / OFF control of the switch (22) by the control unit (30). Therefore, the change speed of the detection voltage can be made variable, and the detection sensitivity can be made variable.

  As described above, in the present invention, the electronic element (21) is used to make the detection sensitivity variable. According to this, in order to make the detection sensitivity variable, an increase in the size of the optical sensor (100) is suppressed as compared with a configuration using an amplifier composed of a plurality of electronic elements.

  The control unit (30) includes a nonvolatile memory (31) in which a relationship between the switch (22) to be turned on and the capacitance (hereinafter simply referred to as data) is recorded, and a nonvolatile memory (31 And a signal generator (32) for outputting an ON signal based on the data recorded in (1). Therefore, the selection element (21a) can be determined and the detection sensitivity can be made variable by determining the data of the nonvolatile memory (31) according to the use of the user.

  It is preferable to have a plurality of power storage units, and the plurality of power storage units are connected in parallel between the photoelectric conversion element and the ground. According to this, the capacitance determined by the selection element (21a) and the photoelectric conversion element (10) can be varied in various ways as compared with the configuration in which the power storage unit (20) is single. Therefore, the change speed of the detection voltage can be varied and the detection sensitivity can be varied.

It is a circuit diagram of the photosensor concerning a 1st embodiment. It is a timing chart for demonstrating operation | movement of the optical sensor shown in FIG. It is a circuit diagram for demonstrating operation | movement of the optical sensor shown in FIG. It is a circuit diagram for demonstrating operation | movement of the optical sensor shown in FIG. It is a circuit diagram which shows the modification of an optical sensor. It is a circuit diagram which shows the modification of an optical sensor. It is a circuit diagram which shows the modification of an optical sensor. It is a circuit diagram which shows the modification of an optical sensor. It is a circuit diagram which shows the modification of an optical sensor.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
The optical sensor according to this embodiment will be described with reference to FIGS. As shown in FIG. 1, the optical sensor 100 includes a photoelectric conversion element 10, a power storage unit 20, and a control unit 30. The optical sensor 100 according to the present embodiment includes a reset switch 40 and an amplifier 50 in addition to the elements 10 to 30 described above. The characteristic points of the optical sensor 100 are the power storage unit 20 and the control unit 30.

  As shown in FIG. 1, the photoelectric conversion element 10 and the reset switch 40 are connected in series in order from the power source to the ground, to the first wiring 71 that electrically connects the power source and the ground. A connection point 60 between the photoelectric conversion element 10 and the reset switch 40 in the first wiring 71 is electrically connected to the amplifier 50 through the second wiring 72. In addition, the power storage unit 20 is connected to a third wiring 73 that connects the second wiring 72 and the ground, and the power storage unit 20 is driven and controlled by the control unit 30. When the power storage unit 20 is driven and controlled, the capacity for storing the charge photoelectrically converted by the photoelectric conversion element 10 is variable, and the detection signal amplified by the amplifier 50 is variable. As a result, the detection sensitivity of the optical sensor 100 is variable. Hereinafter, the optical sensor 100 will be described in detail.

  The photoelectric conversion element 10 photoelectrically converts received light and stores the photoelectrically converted charges. In the present embodiment, a photodiode is employed as the photoelectric conversion element 10. The amount of charge that is photoelectrically converted (hereinafter simply referred to as charge) is proportional to the intensity of light received by the photoelectric conversion element 10, and at least a part of the charge is stored in the photoelectric conversion element 10. In the present embodiment, a part of the charge is stored in the photoelectric conversion element 10 and the remaining charge is stored in the power storage unit 20 described later.

  On the first wiring 71, the photoelectric conversion element 10 has a cathode side terminal (hereinafter referred to as a cathode terminal 10 a) connected to a power source, and an anode side terminal (hereinafter referred to as an anode terminal 10 b) connected to a connection point 60. It is connected to the ground via the reset switch 40. As a result, when the reset switch 40 is turned off, electric charge is stored in the photoelectric conversion element 10, the voltage on the anode terminal 10 b side, that is, the voltage at the connection point 60 fluctuates, and the voltage of the detection signal input to the amplifier 50. (Hereinafter referred to as a detection voltage) fluctuates. As described above, the amount of charge is proportional to the intensity of light received by the photoelectric conversion element 10. Therefore, a detection signal corresponding to the intensity of light received by the photoelectric conversion element 10 is output to the outside via the amplifier 50. When the reset switch 40 is turned on, the photoelectric conversion element 10 is reversely connected, and the voltage across the photoelectric conversion element 10 becomes constant. As a result, the charge stored in the photoelectric conversion element 10 flows to the ground, and the amount of stored power becomes zero.

  The power storage unit 20 is for storing electric charges. The power storage unit 20 includes an electronic element 21 and a switch 22. The electronic element 21 stores electric charges. In the present embodiment, a capacitor is employed as the electronic element 21. In the present embodiment, the switch 22 is turned on when a Hi signal is input to its own control electrode, and is turned off when a Lo signal having a lower voltage level than the Hi signal is input to the control electrode. An N-channel MOSFET is employed.

  As described above, the power storage unit 20 is connected to the third wiring 73 that connects the second wiring 72 and the ground, and the second wiring 72 is connected to the first wiring 71 at the connection point 60. With this connection configuration, the power storage unit 20 is electrically connected to the photoelectric conversion element 10 provided in the first wiring 71.

  Further, the electronic element 21 and the switch 22 included in the power storage unit 20 are connected in series between the second wiring 72 and the ground. In the present embodiment, the switch 22 and the electronic element 21 are connected in series in order from the second wiring 72 to the ground. With this connection configuration, when the switch 22 is in the OFF state, the electrical connection between the electronic element 21 and the second wiring 72 is cut off, and when the switch 22 is in the ON state, the electrical connection between the electronic element 21 and the second wiring 72 is performed. Connections are made. Therefore, when the switch 22 is in the ON state, the electronic element 21 and the photoelectric conversion element 10 are connected, and a part of the electric charge is stored in the electronic element 21. On the contrary, when the switch 22 is in the OFF state, the connection between the electronic element 21 and the photoelectric conversion element 10 is cut off, and the electric charge is not stored in the electronic element 21.

  As shown in FIG. 1, the optical sensor 100 according to the present embodiment has two third wirings 73, and the power storage unit 20 is provided in each third wiring 73. Thus, the two power storage units 20 are connected in parallel between the second wiring 72 and the ground. Incidentally, the electrostatic capacity of the electronic element 21 included in each of the two power storage units 20 is the same.

  The control unit 30 is for controlling the switch 22. The control unit 30 includes a nonvolatile memory 31 and a signal generation unit 32. The nonvolatile memory 31 includes a switch 22 that is turned on, and a relationship between the electronic element 21 connected in series with the switch 22 that is turned on and the capacitance determined by the photoelectric conversion element 10 (hereinafter simply referred to as data). ) Is recorded. In the present embodiment, a ROM is adopted as the nonvolatile memory 31. The signal generation unit 32 outputs a signal to the switch 22 stored in the data based on the data recorded in the nonvolatile memory 31. In the present embodiment, a CPU is employed as the signal generation unit 32.

  As described above, the two power storage units 20 are provided in the third wiring 73. In the present embodiment, the switch 22 included in one of the two power storage units 20 corresponds to the switch 22 stored in the data. Hereinafter, the switch 22 stored in this data is referred to as a selection switch 22a, and the electronic element 21 connected in series with the selection switch 22a is referred to as a selection element 21a. The switch 22 included in the other of the two power storage units 20 is referred to as a non-select switch 22b, and the electronic element 21 connected in series with the non-select switch 22b is referred to as a non-select element 21b.

  The signal generation unit 32 outputs a selection signal to the control electrode of the selection switch 22a and outputs a non-selection signal to the control electrode of the non-selection switch 22b. As shown in FIG. 2, the selection signal is a Hi signal, and the non-selection signal is a pulse signal consisting of a Hi signal and a Lo signal. When the Hi signal included in these two signals is input to the switches 22a and 22b, the switches 22a and 22b are turned on. When the Lo signal is input, the non-select switch 22b is turned off. The Hi signal included in the selection signal corresponds to the ON signal described in the claims.

  The signal generation unit 32 according to the present embodiment outputs a control signal to the reset switch 40. This control signal is a pulse signal composed of a Hi signal and a Lo signal, as shown in FIG. The pulse period is T, the pulse width is τ, and the pulse interval (adjacent pulse interval) is T-τ (hereinafter referred to as s). As shown in FIG. 2, the selection signal is composed of only the Hi signal, and the non-selection signal and the control signal are the same signal. Incidentally, the pulse interval s corresponds to the second predetermined time described in the claims, and the pulse width τ corresponds to the third predetermined time described in the claims.

  The reset switch 40 is for discharging charges stored in the photoelectric conversion element 10 and the electronic element 21 to the ground. In this embodiment, an N-channel MOSFET is employed as the reset switch 40, which is turned on when a Hi signal is input to its own control electrode, and is turned off when a Lo signal is input to the control electrode. Yes.

  As shown in FIG. 1, the reset switch 40 is provided on the first wiring 71 between the connection point 60 and the ground. The reset switch 40 is electrically connected to the power storage unit 20 via the second wiring 72 connected to the connection point 60.

  The reset switch 40 is turned on when the Hi signal included in the control signal is input from the signal generation unit 32, and the connection point 60 and the ground are electrically connected via the reset switch 40. Then, the anode terminal 10b and the terminal on the second wiring 72 side of the electronic element 21 are connected to the ground, and the charges stored in the photoelectric conversion element 10 and the electronic element 21 are discharged. On the contrary, the reset switch 40 is turned off when the Lo signal included in the control signal is input from the signal generation unit 32, and the connection between the connection point 60 and the ground is disconnected by the reset switch 40. Therefore, the anode terminal 10b and the terminal on the second wiring 72 side of the electronic element 21 are disconnected from the ground, and charges are stored in the photoelectric conversion element 10 and the electronic element 21, respectively.

  The amplifier 50 amplifies a detection voltage depending on the photoelectrically converted charge. As shown in FIG. 1, the amplifier 50 has a non-inverting input terminal, an inverting input terminal, and an output terminal. A second wiring 72 is connected to the non-inverting input terminal, and the inverting input terminal has a resistor 51. Via the output terminal. Incidentally, the amplification factor of the detection voltage amplified by the amplifier 50 is determined by the resistance value of the resistor 51.

  Next, the behavior of the optical sensor 100 in the present embodiment will be described with reference to FIGS. As described above, the selection signal is composed of the Hi signal, and the non-selection signal and the control signal are each composed of the same pulse signal. Further, N-channel MOSFETs are employed as the switch 20 and the reset switch 40. Accordingly, each of the switches 20 and 40 is in an ON state while a pulse as a Hi signal is input (pulse width τ), and is in an OFF state while no pulse is input (pulse interval s).

  As shown in FIG. 2, during the pulse interval s, each of the non-selection signal and the control signal is a Lo signal, and the selection signal is a Hi signal. Therefore, each of the switches 22b and 40 is turned off, and the selection switch 22a is turned on. As a result, the photoelectric conversion element 10 is connected to the selection element 21a, and a part of the electric charge photoelectrically converted by the photoelectric conversion element 10 is stored in the selection element 21a as shown by a broken line in FIG. As a result, as indicated by the solid line in FIG. 2, the detection voltage of the detection signal increases.

  Further, as shown in FIG. 2, during the pulse width τ, the non-selection signal and the control signal are Hi signals, and the selection signal is the Hi signal. Therefore, each of the switches 22b and 40 is turned on, and the selection switch 22a is turned on. As a result, the anode terminal 10b of the photoelectric conversion element 10 and the terminals on the second wiring 72 side of each of the electronic elements 21a and 21b are connected to the ground, and as shown by the broken line in FIG. 4, the photoelectric conversion element 10 and the electronic element 21a. , 21b are discharged. As a result, as shown by the solid line in FIG. 2, the detection voltage of the detection signal decreases.

Incidentally, the light sensor 100, as shown in FIG. 2, from the falling edge of the pulse contained in the non-selection signal and the control signal, after sampling time t _s is shorter than the pulse interval s, via an amplifier 50 To detect the detection signal output externally. This sampling timing has the same period as the pulse period T. Sampling time t _s is equivalent to a first predetermined time described in the appended claims.

Here, the sampling time t _s, charge, the photoelectric conversion element 10, and, because they are accumulated in the respective selection device 21a, the selecting device 21a and the photoelectric conversion element 10, the capacitance is determined to be the power storage capacity of the charge Is done. The higher the capacitance is large, the change rate of the detected voltage becomes slower, the detection voltage detected at the sampling time t _s is reduced. That is, the detection sensitivity becomes insensitive. On the contrary, the more the capacitance is small, the change rate of the detected voltage becomes faster, the detection voltage detected at the sampling time t _s is increased. That is, the detection sensitivity becomes sensitive.

As described above, the capacitance is determined by the selection element 21a and the photoelectric conversion element 10. Therefore, when the number of selection elements 21a is changed, the change rate of the detected voltage varies, the detection voltage detected at the sampling time t _s is changed. That is, the detection sensitivity changes.

In the present embodiment, the electronic element 21 included in one of the two power storage units 20 is the selection element 21a. The detection voltage of the detection signal in this case is indicated by a solid line in FIG. On the other hand, the detection voltage when the electronic element 21 included in each of the two power storage units 20 is the selection element 21a is indicated by a broken line in FIG. According to this, the detection voltage indicated by the broken line, than the detection voltage shown by the solid line, slow rate of change value of the detection voltage is small at the sampling time t _s. Further, the detection voltage when the electronic element 21 included in each of the two power storage units 20 is the non-selection element 21b is indicated by a one-dot chain line in FIG. According to this, the detection voltage indicated by a dashed line, than the detection voltage shown by the solid line, fast change rate, the value of the detected voltage is increased at the sampling time t _s. As specifically described above, when the number of the selection elements 21a is changed, the detection sensitivity is changed.

  Next, functions and effects of the optical sensor 100 according to the present embodiment will be described. As described above, the electronic element 21 is used to make the detection sensitivity variable. Therefore, in order to make the detection sensitivity variable, an increase in the size of the optical sensor 100 is suppressed compared to a configuration using an amplifier composed of a plurality of electronic elements.

  The control unit 30 outputs a selection signal based on the nonvolatile memory 31 in which the relationship (data) between the selection switch 22a and the capacitance is recorded, and on the data recorded in the nonvolatile memory 31. A generation unit 32 is included. Therefore, the selection element 21a can be determined and the detection sensitivity can be made variable by determining the data in the nonvolatile memory 31 according to the user's application.

  The optical sensor 100 has two third wirings 73, and the power storage unit 20 is provided in each of the third wirings 73. According to this, the capacitance determined by the selection element 21a and the photoelectric conversion element 10 can be varied in various ways as compared with a configuration in which the power storage unit 20 is single. Therefore, the change speed of the detection voltage can be varied and the detection sensitivity can be varied.

  The reset switch 40 is connected between a connection point 60 that is an intersection of the wirings 71 and 72 and the ground. The electronic element 21 and the switch 22 are connected in series between the second wiring 72 and the ground. According to this, when each of the switches 40 and 22 is turned on, the charges stored in the photoelectric conversion element 10 and the electronic element 21 flow to the ground, and the respective storage amounts are set to the initial state of 0. Can do.

The reset switch 40 is turned off at the pulse interval s and turned on at the pulse width τ, and the selection switch 22a is always turned on. According to this, the change speed of the detection voltage in each pulse interval s can be made uniform. Thus, at each sampling time t _s, it the amount of charge accumulated in each photoelectric conversion element 10 and the selection element 21a is kept constant, the detection sensitivity at each sampling time t _s can be made constant.

  The signal generation unit 32 outputs a control signal. Thereby, each of the control signal, the selection signal, and the non-selection signal is output from the signal generation unit 32. Therefore, compared with the configuration in which each signal is output from a different signal source, the timing at which each signal is input to each of the switches 40, 22a, and 22b is suppressed. Therefore, the change in detection sensitivity due to excess or deficiency in the amount of power storage is suppressed.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

  In this embodiment, the example which employ | adopted the photodiode for the photoelectric conversion element 10 was shown. However, the photoelectric conversion element 10 is not limited to the above example, and for example, a phototransistor can be adopted as shown in FIG.

  In the present embodiment, an example is shown in which the electronic element 21 included in one of the two power storage units 20 is the selection element 21a. However, a configuration in which the electronic elements 21 included in all the power storage units 20 are non-selective elements 21b may be employed. In this case, all charges are stored in the photoelectric conversion element 10. Furthermore, a configuration in which the electronic elements 21 included in all the power storage units 20 are the selection elements 21a may be employed.

  In this embodiment, the example which employ | adopted the capacitor | condenser as the electronic element 21 was shown. However, the electronic element 21 is not limited to the above example, and, for example, as shown in FIG. In this case, the charge is stored in the parasitic capacitance of the transistor.

  In this embodiment, an example in which N-channel MOSFETs are employed as the switches 22 and 40 has been described. However, the switches 22 and 40 are not limited to the above example, and, for example, P-channel MOSFETs may be employed. In this case, each of the switches 22 and 40 is turned on when the Lo signal is inputted, and is turned off when the Hi signal is inputted. For this reason, the signal levels of the selection signal, the non-selection signal, and the control signal shown in this embodiment are inverted.

  In the present embodiment, the switch 22 and the electronic element 21 are shown as an example of a configuration in which the second wiring 72 is connected in series from the second wiring 72 to the ground. However, as shown in FIG. 7, a configuration in which the electronic element 21 and the switch 22 are connected in series in order from the second wiring 72 to the ground may be employed.

  In this embodiment, the example in which the number of the electrical storage units 20 is two was shown. However, a configuration in which the number of power storage units 20 is one as shown in FIG. 8 and a configuration in which the number of power storage units 20 is three or more as shown in FIG. 9 can also be adopted.

  In the present embodiment, an example in which a ROM is employed as the nonvolatile memory 31 has been described. However, the nonvolatile memory 31 is not limited to the above example, and for example, a hard disk can be adopted.

  In this embodiment, the example in which the electrostatic capacitances of the electronic elements 21 included in the two power storage units 20 are the same is shown. However, it is also possible to adopt a configuration in which the capacitance of the electronic element 21 included in each of the plurality of power storage units is different.

  In the present embodiment, an example in which the non-selection signal is a pulse signal composed of a Hi signal and a Lo signal is shown. However, it is also possible to adopt a signal configuration in which the non-selection signal consists only of the Lo signal.

  In this embodiment, the example of the structure which the signal generation part 32 outputs a control signal to the reset switch 40 was shown. However, a configuration in which an external device different from the signal generation unit 32 outputs a control signal to the reset switch 40 may be employed.

DESCRIPTION OF SYMBOLS 10 ... Photoelectric conversion element 20 ... Power storage unit 21 ... Electronic element 22 ... Switch 30 ... Control part 31 ... Nonvolatile memory 32 ... Signal generation part 100 ... Optical sensor

Claims (7)

An optical sensor having a photoelectric conversion element (10) that photoelectrically converts received light and stores the photoelectrically converted charge, and outputs a detection signal corresponding to the amount of charge photoelectrically converted in a first predetermined time,
A power storage unit (20) for storing the charge converted by the photoelectric conversion element, and a control unit (30) for controlling the power storage unit,
The power storage unit includes an electronic element (21) for storing charges and a switch (22),
The electronic element and the switch are connected in series between the ground side terminal of the photoelectric conversion element and the ground,
The control unit is a non-volatile memory in which a relationship between the switch to be turned on, and the capacitance determined by the photoelectric conversion element and the electronic element connected in series to the switch in the on state is recorded. (31) and signal generation for outputting an ON signal for turning on the switch to the switch based on the relationship between the switch and the electrostatic capacity recorded in the non-volatile memory. An optical sensor comprising a portion (32). Having a plurality of power storage units,
The optical sensor according to claim 1, wherein the plurality of power storage units are connected in parallel between the photoelectric conversion element and a ground. A reset switch (40) for discharging the electric charge stored in each of the photoelectric conversion element and the electronic element;
3. The optical sensor according to claim 1, wherein the reset switch is connected between a connection point (60) between the photoelectric conversion element and the power storage unit and a ground. The reset switch is turned on for the third predetermined time by a control signal whose adjacent pulse interval is a second predetermined time that is equal to or longer than the first predetermined time and whose pulse width is a third predetermined time. And
The signal generation unit outputs the ON signal based on a relationship between the switch and the capacitance to be turned ON recorded in the nonvolatile memory while the reset switch is OFF.
4. The optical sensor according to claim 3, wherein, while the reset switch is in an ON state, the ON signal is output to at least a switch that is turned on and stored in the nonvolatile memory.   The optical sensor according to claim 4, wherein the signal generation unit outputs the control signal.   The optical sensor according to claim 1, wherein the electronic element is a transistor.   The optical sensor according to claim 1, wherein the electronic element is a capacitor.

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