JP2005049229A - Object detection sensor, object detection method, and card reader using them - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a good detection results with high sensitivity with simple constitution. <P>SOLUTION: The detection process circuit 14 for obtaining various information about an object to be detected by properly processing the DC conversion signal DC converted from the sinusoidal detection output from the detection coil 12 is constituted such that a signal variation of the DC conversion signal is detected by differentiating the DC conversion signal by the differential circuit 17, and the various information about the object is obtained based on the variation of the DC conversion signal. By the constitution, so called effect of temperature drift can be eliminated, lowering the threshold value for detection can be made possible, and the detection distance can be extended. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an object detection sensor and an object detection method for detecting various types of information on a detection target, and a card reader using them.

  Generally, an object detection sensor is a type of a card inserted into a coin unevenness or material identification device, a motor rotation drive control device, or a card reader in a vending machine, automatic ticket vending machine, ATM or other device that handles coins. Widely used in a wide variety of devices such as a device for identifying the like. Such an object detection sensor usually has a structure called an eddy current type. For example, as shown in FIG. 12, a current is applied to a coil 2 wound around a rod-shaped core body 1. , And a detection magnetic flux φr is generated, and the detected body 3 and the core body 1 are relatively moved in the magnetic field formed by the detection magnetic flux φr. Since the magnitude of the eddy current generated in the detected object 3 changes in response to the change in the distance and the magnetic resistance changes, the detected output is obtained by capturing the change as the change in inductance. I have to.

  However, in such a conventional object detection sensor, a countermeasure against a so-called temperature drift that is an output fluctuation (amplitude fluctuation) with respect to a temperature change when the detection target 3 is not detected is not sufficiently taken. There is a problem that good temperature characteristics of the object detection sensor cannot be obtained due to the influence of the magnetic permeability of the core body 1 due to the change.

  Accordingly, an object of the present invention is to provide an object detection sensor and an object detection method having high sensitivity and good temperature characteristics with a simple configuration, and a card reader using them.

In order to achieve the above object, in the object detection sensor according to claim 1 of the present invention, a sinusoidal detection output output from the detection coil based on a change in magnetic flux formed by energizing the excitation coil is provided. A detection processing circuit that acquires various types of information about the detected object by performing appropriate processing on the DC converted signal that has been DC converted is provided with a differentiating circuit that detects an output change of the DC converted signal.
According to the object detection sensor of the first aspect having such a configuration, since the differentiation circuit for detecting the output change of the DC conversion signal is provided, the object detection sensor uses the differential waveform of the DC conversion signal. Various information will be acquired. Therefore, the influence of so-called temperature drift is eliminated, and the temperature drift amount does not have to be estimated as the detection threshold value. Therefore, the detection threshold value can be lowered and the detectable distance is expanded. It has become so.

Further, in the object detection method according to claim 2 of the present invention, various types of information on the detected object are obtained by performing appropriate processing on the DC conversion signal obtained by direct-converting the sinusoidal detection output output from the detection coil. In the detection processing circuit, the DC conversion signal is differentiated to detect a signal change of the DC conversion signal.
According to the object detection method according to claim 2 having such a configuration, since the differentiating circuit for detecting the output change of the DC conversion signal is provided, the object detection method using the differential waveform of the DC conversion signal is provided. Various information will be acquired. Therefore, the influence of so-called temperature drift is eliminated, and the temperature drift amount does not have to be estimated as the detection threshold value. Therefore, the detection threshold value can be lowered and the detectable distance is expanded. It has become so.

Furthermore, in the card reader according to claim 3 of the present invention, the object detection sensor according to claim 1 is provided as an entrance sensor for detecting the type of the card inserted into the apparatus.
Furthermore, the card reader according to claim 4 of the present invention is configured to detect the type of the card inserted into the apparatus by the object detection method according to claim 2.
Also in the card reader according to claim 3 or claim 4 having such a configuration, the same action as the object detection sensor or the object detection method described above can be obtained.

  As described above, the object detection sensor according to the first aspect of the present invention or the object detection method according to the second aspect of the present invention appropriately converts the sinusoidal detection output output from the detection coil into a DC conversion signal obtained by DC conversion. In the detection processing circuit that acquires various types of information about the detected object by performing processing, the signal conversion of the DC conversion signal is detected by differentiating the DC conversion signal, and the detectable threshold is reduced by reducing the detection threshold. Since it is configured to be enlarged, the temperature characteristics can be improved with a simple configuration, a good detection result can be obtained with high sensitivity, and an inexpensive and high-performance object detection sensor can be obtained. it can.

  The card reader according to claim 3 or 4 of the present invention includes the object detection sensor according to claim 1 described above or the object detection method according to claim 2 of the present invention. By detecting the signal change of the DC conversion signal by differentiating the signal and lowering the detection threshold and expanding the detectable distance, it is possible to obtain a good detection result with high sensitivity. A high performance card reader can be obtained.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In the object detection sensor 10 according to the embodiment shown in FIG. 1, a detection coil 12 is wound around a central core portion 11a of a core body 11 made of a single thin plate member, and the center An exciting coil 13 is wound around a shaft end core portion 11c that is integrally connected to the upper end side of the core portion 11a in the figure via a locking collar portion 11b.

  The shaft end core portion 11c is disposed so as to be able to face a detection object made of a metal member or a magnetic body (not shown). In the present embodiment, the shaft end core portion 11c extends from the shaft end core portion 11c to the center core portion 11a. The direction of the axis (the vertical direction in the figure) is set to a positional relationship that is substantially orthogonal to the moving direction of the detection target. And the to-be-detected object which abbreviate | omitted illustration with respect to the said shaft end core part 11c is reciprocated along the direction substantially orthogonal to an axial center, The said shaft end core part 11c and a to-be-detected body mutually When the two members face each other within an appropriate distance range when facing and separating from each other while facing each other, the presence (presence) of the detected object is detected. In addition, the structure which the object detection sensor 10 side moves in the state to which the to-be-detected body was fixed may be sufficient.

  More specifically, the central core portion 11a is disposed so as to be sandwiched between the pair of locking collar portions 11b and 11b in the extending direction of the shaft center (the vertical direction in the drawing), and the direction of the shaft center The width dimension W1 in the orthogonal direction (left-right direction in the figure) is formed to be a relatively wide dimension. On the other hand, the width dimension W2 of the shaft end core portion 11c is set to be smaller than the width dimension W1 of the central core portion 11a (W2 <W1). In the present embodiment, the width dimension is less than half (W2 ≦ W1). / 2). This is to improve the current efficiency in the shaft end core portion 11c by making the shaft end core portion 11c facing the object to be detected narrow, and by generating more magnetic flux, This is to increase the detection sensitivity related to the amount of change in detection, that is, the presence or absence of the detection target.

  The exciting coil 13 wound around the shaft end core portion 11c has a lead portion 13b drawn from the winding portion 13a connected to a terminal portion of an AC power supply (not shown). By applying a sine wave or a rectangular wave generated from the power source to the winding portion 13a of the excitation coil 13, an appropriate detection magnetic field φ is formed along the axis. Yes.

  At this time, the locking collar portion 11b provided at the boundary portion between the above-described central core portion 11a and the shaft end core portion 11c protrudes in the width direction (the left-right direction in the drawing) substantially orthogonal to the axial direction. The excitation coil 13 and the detection coil 12 described above are wound around positions in the axial direction with respect to the locking collar portion 11b. That is, the winding position of each of the coils 13 and 12 is positioned by the locking collar portion 11b. Thus, if the winding position of each coil 12 and 13 can be positioned with high accuracy by providing the locking collar portion 11b at the boundary portion between the central core portion 11a and the shaft end core portion 11c, the phase shift or Output deviation is reduced and a large change rate is obtained.

  The sensor output obtained from the detection coil 12 is a sinusoidal signal as shown in the “sensor raw output” column on the left end side in FIG. The sensor output signal is input to the detection circuit 14 as shown in FIG.

  In the detection circuit 14, the signal is first amplified by the amplifier circuit 15, and as shown in the “Amplifier waveform” column in FIG. 2, and then converted into direct current by the DC converter 16. ”Is converted into a substantially linear DC conversion signal as shown in each column.

  Next, the DC conversion signal output from the DC converter 16 is input to the differentiation circuit 17. The differentiation circuit 17 has a function of detecting the output change of the DC conversion signal described above, that is, a function of differentiating the DC conversion signal and converting it into a differential signal, and the column of “DC differential waveform” in FIG. As shown in the upper “A” column and the middle “B” column, when the above-described DC conversion signal does not change, the differential signal output from the differentiating circuit 17 is “0”. " On the other hand, when the DC conversion signal changes, that is, when it is shown in the lower “C” column in the “DC differential waveform” column in FIG. A differential signal corresponding to the degree of the above is obtained from the differentiation circuit 17, and the output signal from the differentiation circuit 17 is passed through the detection unit 18 and the determination circuit 19, so that the final presence / absence or type of the detected object is determined. It is to be judged.

  This point will be described in more detail. First, the detection output obtained from the detection coil 12 of the object detection sensor 10 described above corresponds to the change in the detection magnetic field φ generated by the excitation coil 13. That is, when there is no object to be detected (none) or the object to be detected is sufficiently far (infinitely far) from the object detection sensor 10, the detection coil 12 causes the detection in FIG. A sinusoidal detection signal having a very small amplitude as shown in the upper “A” column in the “sensor raw output” on the left end side is obtained. On the other hand, when the object detection sensor 10 and the detected object are relatively close to each other and are in the appropriate range (present), they occur in the detected object in response to a change in the distance between them. As the eddy current changes, the above-described excitation magnetic field φ changes, and the detection coil 12 is shown in the middle “B” column in the “sensor raw output” on the left end side in FIG. Thus, a larger amplitude sinusoidal detection signal is obtained.

  Therefore, in the case of a transient state in which the detected object is changed from the state without the detected object or the state at infinity to the state with the detected object, the detection output from the detection coil 12 is “sensor life” on the left end side in FIG. As shown in the lower “C” column in “Output”, the sine wave detection signal having a small amplitude is changed to a sine wave detection signal having a large amplitude. The output of the DC conversion signal from the DC converter 16 also changes with the change in the detection output from the detection coil 12 at that time, and the output change of the DC conversion signal at that time changes as described above. The differential circuit 17 detects the differential signal as shown in the lower “C” column in the “DC differential waveform” column in FIG. Then, by using the differential signal from the differentiating circuit 17, information such as the presence / absence of an object to be detected is detected.

  As described above, according to the present embodiment, the DC conversion signal is differentiated and converted into the differential signal in the differentiation circuit 17 of the detection processing circuit 14, and information such as the presence / absence of the detected object is obtained based on the differential signal. It becomes. Further, even if the amplitude of the “sensor raw output” varies due to a temperature change when the detected object is not detected, the amplitude variation due to the temperature change does not occur instantaneously, so the output from the differentiation circuit 17 The differentiated signal is not affected by temperature changes. Therefore, the influence of so-called temperature drift is eliminated, and the temperature drift amount does not have to be estimated as the detection threshold value. Therefore, the detection threshold value can be set lower, and the detectable distance is expanded. It is like that.

  Here, as a countermeasure against the temperature drift described above, for example, a “differential output type” sensor as shown in FIG. 4 in which the same reference numerals are attached to the components corresponding to the above-described embodiment may be adopted. It is done. That is, in the differential output type object detection sensor shown in FIG. 4, a pair of exciting coils 13 and 13 are provided on shaft end core portions 11c and 11c provided at both end portions of the core body 11 having a vertically symmetrical shape. The detection coil 12 is wound around the central core portion 11a between the pair of excitation coils 13 and 13, respectively. Then, excitation magnetic fluxes Φ1 and Φ2 are formed by appropriately energizing the pair of excitation coils 13 and 13, and the magnetic fluxes of both the magnetic fluxes Φ1 and Φ2 correspond to the positional relationship with the detected object. When changed, a signal corresponding to the difference between them is output from the detection coil 12 as a differential signal.

  More specifically, when the object to be detected does not exist or the object to be detected exists sufficiently far from the object detection sensor, the excitation magnetic fluxes Φ1 and Φ2 described above are balanced in the same state. Then, the output from the detection coil 12 at that time is adjusted to “0”, and then the difference in magnetic flux change between the excitation magnetic fluxes Φ1 and Φ2 when the detected object comes close, that is, a differential signal. Is output from the detection coil 12 and various information such as the presence / absence of an object to be detected is obtained based on the differential signal.

  However, even in such a differential output type object detection sensor, portions of the exciting coils 13 and 13 that are not wound around the core body 11, for example, connections indicated by reference numerals 13b and 13b in FIG. A line (hatched portion) may form a useless magnetic field, and a detection component due to the effect of the useless magnetic field may be superimposed on the detection output described above. That is, the magnetic flux formed by the current flowing through the portions 13b and 13b that are not wound around the core body 11 directly jumps from the outside to the detection coil 12 without the core body 11 interposed. As a result, the phase is shifted with respect to the normal excitation magnetic fluxes Φ1 and Φ2 described above. As a result, there may occur a problem that, for example, an output fluctuation with respect to a temperature change when the detection target is not detected appears as a so-called temperature drift. Therefore, if measures such as increasing the threshold value for detection are taken, the detectable distance becomes smaller and the detection sensitivity is lowered. On the other hand, in the object detection sensor according to the present invention, as described above, the influence of such temperature drift is almost eliminated, and a highly sensitive sensor can be obtained.

  Next, an embodiment in which the type of the card inserted into the apparatus is detected by providing the above-described object detection sensor 10 according to the present invention as an entrance sensor of a card reader will be described.

  First, in the apparatus main body 20 of the IC card reader shown in FIG. 4, an IC card 23 inserted through a card insertion slot 22 provided on the right end side in the figure is arranged so as to extend in a substantially horizontal direction. The card is guided by the card transport path 24 and is sent to the rear end side of the apparatus as shown in the figure. The card transport path 24 is configured to be sandwiched between the upper frame 24a and the lower frame 24b, and is transported at a relatively forward (right side in the drawing) position of the card transport path 24. A card feeding roller 25a or a feeding pad 25b as a driving means is rotationally driven by a motor (not shown) so that the IC card 23 is placed on the rear end side (right end side in the drawing) of the card reading / writing. It is guided to the insertion position.

  Specifically, the IC card 23 taken into the inside of the card transport path 24 from the card insertion slot 22 is further pushed after the tip 23a of the IC card 23 comes into contact with the card contact member 26, The card contact member 26 is moved in the card running direction together with the IC card 23. With the movement of the card abutting member 26, the IC contact 27 is moved to the position where it abuts on the contact terminal portion 23b of the IC card 23 by the action of the contact block 28.

  On the other hand, the card abutting member 26 includes a protruding portion 26 a that abuts the tip 23 a of the IC card 23 and a receiving means 26 b that supports the back side of the IC card 23. The protruding portion 26a is formed so as to face downward at the tip end portion (the left end side portion in the drawing) of the card abutting member 26, and the IC card that runs in the card transport path 24 with respect to the protruding portion 26a. A part of the projecting portion 26a is disposed so as to project into the card transport path 24 formed by the upper frame 24a and the lower frame 24b so that the contact portion 23 abuts.

  The card contact member 26 described above is provided so as to be movable in the direction in which the IC card 23 travels. The return bias is applied, and until the IC card 23 comes into contact with the card contact member 26 and is moved, it stands by at the rear position (right position in the figure) as shown in FIG. Then, when the IC card 23 travels toward the card reading / writing position on the left side in the drawing and the tip 23a of the IC card 23 abuts against the protruding portion 26a of the card abutting member 26, the card abutting member 26 moves together with the IC card 23 in the card running direction, that is, toward the left side in the figure, whereby the card contact member 26 reads information from the card set position shown in FIG. / The position to be written is reached.

  On the other hand, the contact block 28 is engaged with the card abutting member 26 while holding the probe needle-like IC contact 27, and interlocks with the card abutting member 26 moving to the left end side in the figure. 6 descends along the cam groove 26e provided in the card contact member 26 so as to extend obliquely from the card separation position in FIG. 6, and reaches the card contact position shown in FIG. It is made to the structure to do. The contact block 28 is configured to bring the IC contact 27 into contact with the contact terminal portion 23b of the IC card 23 immediately before reaching the card contact position.

  The sensor 29 arranged on the upper side in the figure is provided so as to detect the slit 26 c provided in the card contact member 26 and the rear end side end surface 26 d of the card contact member 26. The timing at which the traveling speed of the IC card 23 is reduced by detecting the slit 26c is detected, and the IC card 23 is stopped at the card reading / writing position by detecting the rear end surface 26d. Is to be detected. In the present embodiment, an optical sensor is used as the sensor 29. However, other means such as a magnetic sensor or a mechanical sensor may be used.

  On the other hand, particularly as shown in FIGS. 7, 8 and 9, the card insertion portion, that is, the position upstream of the card reading / writing position in the insertion direction of the IC card 23 (left direction in the figure). For example, two or three inlet sensors 30 and 10 for detecting the type of the inserted card are provided. That is, in the configuration of the card reader described above, two entrance sensors 30 and 10 are provided. These entrance sensors 30 and 10 include a first magnetic sensor 30 that detects a magnetic stripe of the magnetic card, and And a second magnetic sensor 10 for detecting a contact terminal portion of the contact IC card. On the other hand, when the card reader has a known non-contact IC card antenna (not shown), three entrance sensors are provided. These entrance sensors 30, 10, and 10 are magnetic sensors of the magnetic card. From the 1st magnetic sensor 30 which detects a stripe, the 2nd magnetic sensor 10 which detects the contact terminal part of a contact type IC card, and the 3rd magnetic sensor 10 which detects the antenna part of a non-contact type IC card It is configured.

  Among them, the second magnetic sensor 10 and the third magnetic sensor 10 are provided so as to face the card transport path 24, and the magnetic sensor according to the present invention shown in FIG. 1 is fixed to the housing. In the present embodiment, these sensors 10 are arranged in parallel in a direction substantially orthogonal to the card running direction immediately after the card insertion port 22 on the left side in FIG. , 10 are arranged so as to be in substantially the same position. As shown in FIGS. 10 and 11 in particular, it is embedded in the resin body 10b attached to the housing 10a and extends from the magnetic sensor constituting the second magnetic sensor 10. Each terminal plate 10c that protrudes substantially horizontally toward the outside of the housing 10a is connected to a circuit control unit (not shown).

  Here, the second magnetic sensor 10 has a function of detecting the contact terminal portion 23b provided on the contact-type IC card 23 described above as a detected object. Is inserted from the card insertion slot 22, a detection signal is emitted from the second magnetic sensor 10. Further, the third magnetic sensor 10 is arranged so as to detect as an object to be detected an antenna portion that is arranged in a non-contact type IC card so as to form a band or the like. When an IC card is inserted from the card insertion slot 22, a detection signal is emitted from the third magnetic sensor 10.

  On the other hand, the first magnetic sensor 30 constitutes a magnetic pre-head in the case where a card having a magnetic stripe is used as the magnetic recording information section, and the second and third magnetic sensors 10, 10. When a card having a magnetic stripe such as a magnetic card is inserted through the card insertion slot 22, a detection signal is generated from the first magnetic sensor 30. It has become.

  Furthermore, a known shutter means 40 for opening and closing the card transport path 24 is disposed on the downstream side (back side) of the first magnetic sensor 30 in the card transport direction, and an appropriate IC card 23 is inserted. If it is, the shutter means 40 is opened based on the appropriate detection signal. However, when an inappropriate card is inserted, that is, when the contact terminal portion 23b of the IC card 23 is not detected. By holding the shutter means 40 in the shut-off state, unauthorized use of the card is prevented in advance.

  Since the open / close circuit of the shutter means 40 is the same as that conventionally known, the description thereof will be omitted, but without providing such a shutter means 40, an illegal card is not taken into the apparatus by motor drive control. It is also possible to make it.

  On the other hand, when a detection signal from the proper IC card 23 is emitted from the inlet sensors 30, 10, and 10, the card and the motor of the conveyance driving means are driven based on the detection signal, thereby the card feeding roller 25a described above. The IC card 23 is carried into the card transport path 24 through the shutter means 40. Then, the leading end 23 a of the IC card 23 running in the card transport path 24 is guided to the protruding portion 26 a of the card abutting member 26. Even after the tip 23a of the IC card 23 comes into contact with the protrusion 26a, the card feed roller 25a is continuously driven to run the IC card 23. Accordingly, the protruding portion 26a of the card abutting member 26 is pushed in the card running direction by the tip 23a of the IC card 23, and the card abutting member 26 is integrated with the IC card 23 in the card running direction, that is, on the left side in the figure. It will move to the back side.

  As the card contact member 26 moves in the card running direction, the contact block 28 engaged with the card contact member 26 moves up and down. That is, the contact block 28 is lowered using the cam groove 26 e to bring the IC contact 27 into contact with the contact terminal portion 23 b of the IC card 23. Thereafter, since the IC card 23 moves to a position where information is read / written, the contact block 28 is further lowered accordingly. Therefore, as the IC card 23 approaches the card reading / writing position, the IC contact 27 is further pressed against the contact terminal portion 23b of the IC card 23.

  As mentioned above, although the embodiment of the invention made by the present inventor has been specifically described, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. Not too long.

  For example, in the above-described embodiment, the present invention is applied to an object detection sensor that does not use a differential output, but the differential output type object detection sensor as shown in FIG. In contrast, the differentiation circuit according to the present invention can be similarly provided.

  In the embodiment described above, the width dimension of the shaft end core portion 11c is made smaller than the width dimension of the central core portion 11a (W2 <W1), but both are made equal or set to the opposite magnitude relationship. Is also possible.

  Furthermore, in the embodiment described above, a single thin plate-shaped member is used as the core body, but even a three-dimensional core body can be similarly employed.

  The object detection sensor and the object detection method according to the present invention described above are devices for handling coins such as vending machines, ticket vending machines, ATMs, etc., as well as devices for identifying the type or the like of a card inserted into a card reader. Can be widely used in a wide variety of devices such as a coin unevenness and material identification device and a motor rotation drive control device in various rotation drive devices.

It is side explanatory drawing showing the schematic structure of the non-differential type object detection sensor in one Embodiment of this invention. FIG. 4 is a diagram showing a detection output obtained from the object detection sensor shown in FIG. 1 and waveforms of respective outputs obtained when the detection output is used in the detection circuit of FIG. 3. It is a block diagram showing the schematic structure of the detection circuit in one Embodiment of this invention. It is side surface explanatory drawing showing the schematic structure of the differential type | mold object detection sensor in other embodiment of this invention. FIG. 4 is a longitudinal cross-sectional explanatory view showing a state where an IC card is conveyed to a reading / writing position in a card conveying path of a card reader according to an embodiment of the present invention. FIG. 6 is a longitudinal cross-sectional explanatory view showing a state immediately before the card reaches the reading / writing position in the card transport path of the card reader shown in FIG. 5. FIG. 6 is an enlarged side view illustrating a card insertion slot portion in the card transport path of the card reader shown in FIG. 5. It is front explanatory drawing of the card insertion slot part represented by FIG. It is front explanatory drawing which expanded and represented the card insertion slot part represented by FIG. It is side surface explanatory drawing showing an example of the magnetic sensor group used for the card reader shown by FIG. 5 and FIG. FIG. 11 is an explanatory plan view of the magnetic sensor set shown in FIG. 10. It is side surface explanatory drawing showing the schematic structure of the general object detection sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Object detection sensor 11 Core body 11a Central core part 12 Coil for detection 11b Locking hook part 11c Shaft end core part 13 Excitation coil 13a Winding part 13b Lead part 14 Detection circuit 15 Amplifier circuit 16 DC converter 17 Differentiation circuit 20 IC card reader device main body 22 Card insertion slot 23 IC card 23b Contact terminal 27 IC contact 10, 30 Entrance sensor

Claims (4)

A core body arranged to face the object to be detected;
An excitation coil and a detection coil wound around the core body;
The sinusoidal detection output output from the detection coil is converted into a DC conversion signal by DC conversion based on a change in excitation magnetic flux formed by energizing the excitation coil, and appropriate processing is performed on the DC conversion signal. A detection processing circuit for acquiring various information related to the detected object,
In the object detection sensor with
The object detection sensor, wherein the detection processing circuit is provided with a differentiation circuit for detecting an output change of the DC conversion signal. An exciting coil and a detecting coil are wound around a core body facing the detected object, and a sinusoidal detection output output from the detection coil is converted into a DC conversion signal by DC conversion in a detection processing circuit, and the DC In the object detection method in which various information about the detected object is obtained by performing appropriate processing on the converted signal,
An object detection method characterized in that the detection processing circuit detects a signal change of the DC conversion signal by differentiating the DC conversion signal. A card reader, wherein the object detection sensor according to claim 1 is provided as an entrance sensor for detecting a type of a card inserted into the apparatus. A card reader configured to detect a type of a card inserted into the apparatus by the object detection method according to claim 2.

Images