Position detection system and method

Abstract

A position detection system 100 comprises: a scale unit 10 including an incremental scale 11 having plate-like members or slits arranged at predetermined intervals in a predetermined direction, and a reset scale 12 having an area different from that of the plate-like members or the slits; a light-emitting unit 21 for emitting light onto the scale unit 10; an incremental PD 22 and a reset PD 24 for receiving light that has been reflected off or passed through the scale unit 10 and transmitting signals respectively corresponding to the incremental scale 11 and the reset scale 12; a comparator 25 for receiving the signal corresponding to the reset scale 12 from the reset PD 24 and outputting a voltage corresponding to the area of the reset scale 12; and a signal processing unit 26 for detecting the position of the scale unit 10 on the basis of the voltage output corresponding to the area of the reset scale 12.

Description

Location detection system and method

[0001] The present disclosure relates to position detection of a linear encoder using an optical semiconductor device.

[0002] Conventionally, there has been a known system that measures the position of a device by connecting a linear scale to the device whose position is to be measured and detecting the graduations of the scale. When using such a scale to detect position, information about the position of the scale in an initial state that serves as a reference is required.

[0003] In order to detect the position of the scale in such an initial state, Patent Document 1 discloses a scale device provided with a plurality of scale blocks, each having a different number of graduations. The scale blocks are arranged at predetermined intervals on the scale. In Patent Document 1, a detection head is used to detect pulses corresponding to the number of graduations in each scale block, and each scale block is recognized as a separate unit based on the number of detected pulses, thereby detecting the position of the scale relative to the initial state.

[0004] Japanese Unexamined Patent Publication No. 7-63578

[0005] However, in Patent Document 1, it is necessary to count the number of pulses in order to detect the position of the scale relative to the initial state, which requires a separate configuration for counting the number of pulses and may cause processing delays due to counting the number of pulses.

[0006] Therefore, an object of the present disclosure is to detect the position of a scale while suppressing processing delays with a simple configuration.

[0007] In order to achieve the above-mentioned objective, the position detection system and method disclosed herein employ a technique of detecting the position of a scale portion based on a voltage output corresponding to the area of ​​a second scale having an area different from that of the plate-like members or slits of the first scale arranged at a predetermined period.

[0008] Specifically, the position detection system of the present disclosure comprises: a scale section including a first scale having plate-like members or slits arranged at a predetermined period in a predetermined direction, and a second scale having an area different from that of the plate-like members or slits; an incident section that directs light into the scale section; a light receiving section that receives the light reflected or transmitted by the scale section and sends out signals corresponding to each of the first scale and the second scale; an output section that receives the signal corresponding to the second scale from the light receiving section and outputs a voltage corresponding to the area of ​​the second scale; and a position detection section that detects the position of the scale section based on the voltage output corresponding to the area of ​​the second scale.

[0009] The position detection method disclosed herein is a method for detecting the position of a scale section that includes a first scale having plate-like members or slits arranged at a predetermined period in a predetermined direction, and a second scale having an area different from that of the plate-like members or slits, and includes the steps of: irradiating light onto the scale section; receiving the light reflected or transmitted by the scale section and sending signals corresponding to the first scale and the second scale; receiving the signal corresponding to the second scale and outputting a voltage corresponding to the area of ​​the second scale; and detecting the position of the scale section based on the voltage output.

[0010] According to these, the position of the scale portion can be detected while suppressing processing delays using a simple configuration that detects a voltage output corresponding to the area of ​​the second scale, which has an area different from that of the plate-like member or slit of the first scale.

[0011] Furthermore, in the above configuration, the second scale may have a plurality of plate-like members or slits each having a different width in the specified direction, the output unit may receive a signal corresponding to the second scale from the light receiving unit and output a voltage corresponding to each of the widths of the plurality of plate-like members or slits, and the position detection unit may detect the position of the scale unit based on the voltage output corresponding to each of the widths of the plurality of plate-like members or slits.

[0012] This makes it possible to detect the position of the scale portion while suppressing processing delays with a simple configuration in which a voltage output corresponding to the width of the plate-like member or slit of the second scale is detected.

[0013] In addition, the above configuration may further include an optical sensor having the incident portion and the light receiving portion, and an actuator that moves either the scale portion or the optical sensor in the predetermined direction relative to the other, and the output portion may receive a signal corresponding to the second scale from the light receiving portion and output a voltage corresponding to the area of ​​the second scale in response to the actuator moving either the scale portion or the optical sensor in the predetermined direction.

[0014] According to this, the position of the scale unit in the initial state can be determined by using the actuator to move either the scale unit or the optical sensor relative to the other and detecting the area and width of the second scale. Therefore, even if the position information of the scale unit is lost when the device is turned on or off, there is no need to move the scale unit to the position in the initial state, which shortens the time required for position detection and enables power saving.

[0015] In addition, in the above configuration, the position detection unit may exclude the first voltage output from the output unit after driving the actuator, and detect the position of the scale unit based on the subsequent voltage outputs from the output unit.

[0016] This prevents the width of the second scale from being erroneously detected.

[0017] In addition, in the above configuration, after the actuator is driven, the position detection unit may detect the position of the scale unit based on a second voltage output from the output unit, and exclude any subsequent voltage outputs from the output unit.

[0018] This allows the processing time required by the position detection unit to be reduced.

[0019] In addition, in the above configuration, the position detection unit may receive a signal corresponding to the first scale from the light receiving unit, which changes in response to the actuator moving either the scale unit or the optical sensor in the specified direction, and calculate the amount of displacement of the position of the scale unit.

[0020] This makes it possible to calculate the variation in the position of the scale portion with a simple configuration.

[0021] In addition, in the above configuration, the output unit may be a comparator that outputs a reset signal as a voltage indicating that the second scale has been detected when the voltage value corresponding to the second scale input from the light receiving unit is greater than a predetermined value, and the position detection unit may detect the position of the scale unit based on the reset signal.

[0022] This makes it possible to detect the position of the scale portion using a simple comparator.

[0023] The above disclosures can be combined as much as possible.

[0024] According to the present disclosure, it is possible to detect the position of the scale while suppressing processing delays with a simple configuration.

[0025] FIG. 1 is a diagram illustrating an overview of a position detection system according to an embodiment of the present disclosure. FIG. 2 is a diagram illustrating processing of an incremental signal by a signal processing unit. FIG. 3 is a diagram illustrating processing of an incremental signal by a signal processing unit. FIG. 4 is a diagram illustrating the relationship between a current flowing through a reference PD and a current flowing through a reset PD. FIG. 5 is a diagram illustrating detection of a reset scale by a comparator. FIG. 6 is a diagram illustrating a related scale unit. FIG. 7 is a diagram illustrating a reset scale according to an embodiment. FIG. 8 is a diagram illustrating detection of an origin position by a position detection system according to an embodiment of the present disclosure. FIG. 9 is a diagram illustrating detection of an origin position by a position detection system according to an embodiment of the present disclosure. FIG. 10 is a flowchart illustrating detection of an origin position by a position detection system according to an embodiment of the present disclosure.

[0026] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited to the embodiments shown below. These implementation examples are merely illustrative, and the present disclosure can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art. Note that components with the same reference numerals in this specification and drawings indicate the same components.

[0027] First Embodiment A position detection system 100 according to a first embodiment of the present disclosure will be described with reference to FIGS. 1 to 5. FIG. 1 illustrates an overview of the position detection system 100. The position detection system 100 includes a scale unit 10, an optical sensor 20, and an actuator 30. The position detection system 100 is a system capable of detecting the positions of various devices connected to the scale unit 10. For example, the position detection system 100 can be used as a linear encoder and can be installed in various devices that require absolute position detection, such as single-lens / mirrorless cameras, interchangeable lenses, camcorders, robots, machine tools, and measuring instruments. Here, the absolute position refers to the objective position of a device connected to various devices and subject to position detection, relative to the various devices. For example, the position detection system 100 can detect the position of an interchangeable lens connected to a camera body and moving back and forth relative to the body. In this way, this embodiment can detect the position of a device connected to a device and moving relative to the device body.

[0028] Specifically, the position detection system 100 comprises: a scale section 10 including an incremental scale 11 having plate-like members or slits arranged at a predetermined period in a predetermined direction, and a reset scale 12 having an area different from that of the plate-like members or slits; an emitting section 21 that directs light onto the scale section 10; an incremental PD 22 and a reset PD 24 that receive light reflected or transmitted by the scale section 10 and send signals corresponding to the incremental scale 11 and the reset scale 12, respectively; a comparator 25 that receives a signal corresponding to the reset scale 12 from the reset PD 24 and outputs a voltage corresponding to the area of ​​the reset scale 12; and a signal processing section 26 that detects the position of the scale section 10 based on the voltage output corresponding to the area of ​​the reset scale 12.

[0029] The scale unit 10 is provided so as to be immovable relative to the device whose absolute position is to be detected. For example, if the position of an interchangeable lens connected to a camera body and moving back and forth relative to the body is to be detected, the scale unit 10 is provided so as to be immovable relative to the interchangeable lens but movable relative to the camera body. The scale unit 10 includes an incremental scale 11 and a reset scale 12. The scale unit 10 is arranged so as to be able to reflect light from the optical sensor 20. For example, the scale unit 10 may be arranged so as to overlap the optical sensor 20 in a top view. The incremental scale 11 and the reset scale 12 are movable together in a predetermined direction relative to the device body to which the device whose position is to be measured is connected. In the following description, the movement direction of the incremental scale 11 and the reset scale 12 relative to the device body may be simply referred to as the "movement direction of the scale unit 10." Note that the scale unit 10 may move approximately 70 mm in that movement direction. The movement direction of the scale unit 10 is an example of a "predetermined direction."

[0030] The incremental scale 11 is composed of multiple plate-like members formed in strips and capable of reflecting optical signals from the optical sensors. The multiple plate-like members are arranged side by side at equal intervals in the movement direction of the scale unit 10. In other words, the incremental scale 11 is a mirror with multiple slits formed in strips at equal intervals. When the scale unit 10 is positioned in its initial state, the plate-like member located at the end of the movement direction of the scale unit 10 (the left end or the right end in FIG. 1 ) overlaps with the optical sensor 20. The initial state of the scale unit 10 can be set arbitrarily; for example, the position where the center of the scale unit 10 in a predetermined direction overlaps with the optical sensor 20 may be set as the initial state. The incremental scale 11 functions as a "first scale."

[0031] The reset scale 12 is formed to have a width different from that of each plate-like member of the incremental scale 11 in the movement direction of the scale unit 10. In other words, the reset scale 12 has a different area from that of each plate-like member of the incremental scale 11 in a top view. In this embodiment, the reset scale 12 is formed to be wider than that of each plate-like member of the incremental scale 11 in the movement direction of the scale unit 10. The width of the reset scale 12 may be formed to be narrower than that of the incremental scale 11 in the movement direction of the scale unit 10. Furthermore, the reset scale 12 is separated from the plate-like member located at the end of the incremental scale 11 in the movement direction of the scale unit 10. Information regarding the distance between the reset scale 12 and the plate-like member located at the end of the incremental scale 11 is stored in advance in the memory of the optical sensor 20. In other words, information regarding the distance between the reset scale 12 and the overlapping plate-like members in the initial state is stored in advance in the memory of the optical sensor 20. The specific arrangement and number of the reset scales 12 will be described later. The reset scale 12 functions as a "second scale."

[0032] The optical sensor 20 is provided so as to be movable relative to the device whose absolute position is to be detected. For example, when an interchangeable lens connected to a camera body and moving back and forth is to be the object whose absolute position is to be detected, the optical sensor 20 is provided so as to be movable relative to the interchangeable lens but not movable relative to the camera body. The optical sensor 20 includes a light-emitting unit 21, an incremental PD (Photo Diode) 22, a reference PD (Photo Diode) 23, a reset PD (Photo Diode) 24, a comparator 25, and a signal processing unit 26. The optical sensor 20 is a reflective semiconductor optical sensor device configured to receive light emitted by the light-emitting unit 21 and reflected by the scale unit 10 with the incremental PD 22 and the reset PD 24. Note that the scope of the present disclosure is not limited to detecting the scale position using a reflective semiconductor optical sensor device, and may be configured to detect the scale position using an MR (Magneto Resistance) sensor device. The optical sensor 20 may also be a transmission-type semiconductor optical sensor device.

[0033] The light-emitting unit 21 is a light source configured to be able to emit light. The light-emitting unit 21 is, for example, an LED. The light emitted from the light-emitting unit 21 is reflected by the incremental scale 11 and the reset scale 12. As described above, in this embodiment, only one light source is provided, but two or more light sources may be provided. The light-emitting unit 21 functions as an "incident unit."

[0034] The incremental PD 22 is provided corresponding to the incremental scale 11. Specifically, the incremental PD 22 is disposed in a position where it can receive light emitted by the light-emitting unit 21 and reflected by the incremental scale 11. The incremental PD 22 is configured so that a current flows when light strikes the light-receiving surface.

[0035] 2, the signal processor 26 detects the current flowing through the incremental PD 22 and converts it into an analog incremental voltage signal. Specifically, the signal processor 26 outputs two analog incremental signals, a sine signal and a cosine signal, which are 90 degrees out of phase with each other.

[0036] The signal processing unit 26 performs arctangent processing on the two analog incremental signals, sine and cosine, as shown in the lower graph of Fig. 2. This makes it possible to calculate the amount of change in position corresponding to one period of the arrangement of the plate-like members of the incremental scale 11 for the device whose position is to be detected.

[0037] The signal processing unit 26 calculates the amount of displacement from a specific position by adding up the positional variations for one period, as shown in Fig. 3. This makes it possible to calculate the amount of change in the position of a device connected to the device body and moving relative to the device body.

[0038] In other words, the signal processing unit 26 can calculate the amount of displacement of the position of the scale unit 10 by receiving a signal corresponding to the incremental scale 11 from the incremental PD 22, which changes in response to the actuator 30 moving either the scale unit 10 or the optical sensor 20 in a predetermined direction.

[0039] However, to specifically determine the position of a device that moves relative to the device body, information about the device's position relative to the device body at the time when the optical sensor 20 starts measuring the position is required. Therefore, in this embodiment, the reset signal obtained by the reset PD 24 is used to determine the device's position relative to the device body at the time when the optical sensor starts measuring the position. In other words, in this embodiment, the position of the reset scale 12 is determined to determine how far the device and scale unit 10, the object of position measurement, have moved from their initial positions. In the following description, the position of the scale unit 10 in the initial state is referred to as the origin position. At the origin position, the plate-like member located at the end of the incremental scale 11 and the optical sensor 20 overlap. A more detailed method for determining the origin positions of the device and scale unit 10, the object of position measurement, will be described later.

[0040] The reference PD 23 is configured to receive light from the light emitting unit 21 without passing through the scale unit 10, and to allow a constant current to flow through it. The current flowing through the reference PD 23 is converted into a voltage using a general current-voltage conversion circuit or the like.

[0041] The reset PD 24 is provided corresponding to the reset scale 12. Specifically, the reset PD 24 is positioned so that it can receive light emitted by the light-emitting unit 21 and reflected by the reset scale 12. The reset PD 24 is configured so that a current flows when light strikes its light-receiving surface. The current flowing through the reset PD 24 is converted into a voltage using a general current-voltage conversion circuit or the like. As shown in FIG. 4 , the reset PD 24 is designed so that when it receives light reflected from the reset scale 12, the current flowing through the reset PD 24 is greater than the current flowing through the reference PD 23. Because the voltage value is proportional to the current value, the voltage corresponding to the current flowing through the reset PD 24 is greater than the voltage corresponding to the current flowing through the reference PD 23. The incremental PD 22 and the reset PD 24 function as "light-receiving units."

[0042] The comparator 25 is a typical comparator and has two input terminals as shown in FIG. 5 . The comparator 25 is a circuit that generates a predetermined output based on the voltage applied to the negative input terminal. The negative input terminal is connected to the reference PD 23, and the positive input terminal is connected to the reset PD 24. That is, in this embodiment, the output of the comparator 25 is switched depending on the voltage from the reset PD 24, with the voltage from the reference PD being used as the reference. Specifically, when the voltage at the positive input terminal connected to the reset PD 24 is greater than the voltage at the negative input terminal connected to the reference PD 23, the comparator 25 outputs a high signal. On the other hand, when the voltage at the positive input terminal is smaller than the voltage at the negative input terminal, the comparator 25 outputs a low signal. Here, the high signal and the low signal are voltage signals. For example, the optical sensor 20 can be designed so that the low signal is 0 (V) and the high signal is the power supply voltage (V). The High signal and Low signal output from the comparator 25 are sent to the signal processing unit 26. In the following description, these High signal and Low signal will be referred to as reset signals. The comparator 25 functions as an "output unit."

[0043] In other words, when the voltage value corresponding to the reset scale 12 input from the reset PD 24 is greater than a predetermined value, the comparator 25 outputs a reset signal indicating that the reset scale 12 has been detected.

[0044] In this way, in this embodiment, the presence of the reset PD 24 can be detected using a general and simple comparator.

[0045] The signal processing unit 26 detects the presence and width of the reset scale 12 in the movement direction of the scale unit 10 based on the duration of the High signal. In other words, the signal processing unit 26 detects the presence and area of ​​the reset scale 12. That is, in this embodiment, the area of ​​the reset scale is detected according to the voltage output of the comparator 25 corresponding to the area of ​​the reset scale 12. The signal processing unit 26 indirectly determines the origin position based on the detection results of the presence and width of the reset scale 12. In other words, the signal processing unit 26 determines how far the device and scale unit 10, the object of position measurement, have moved from the origin position by calculating the presence and width of the reset scale 12. A detailed method for determining the origin position will be described later. The signal processing unit 26 functions as a "position detection unit."

[0046] As described above, in this embodiment, the reset scale 12 has a plurality of plate-like members or slits of different widths in the movement direction of the scale section 10, the comparator 25 receives a signal corresponding to the reset scale 12 from the reset PD 24 and outputs a voltage corresponding to each of the widths of the plurality of plate-like members or slits, and the signal processing section 25 detects the position of the scale section 10 based on the voltage output corresponding to each of the widths of the plurality of plate-like members or slits.

[0047] In particular, the device is provided with an actuator 30 that moves either the scale section 10 or the optical sensor 20 in a predetermined direction relative to the other, and the comparator 25 outputs a voltage corresponding to the area of ​​the second scale in response to the actuator 30 moving either the scale section 10 or the optical sensor 20 in the predetermined direction.

[0048] With this configuration, the origin position can be indirectly determined by detecting the position and width of the reset scale 12, which is located away from the end of the incremental scale 11 in the movement direction of the scale unit 10. Therefore, even if the position information of the scale unit 10 is lost when the device is turned on or off, there is no need to move the scale unit 10 to the origin position, which shortens the time required for position detection and enables power saving.

[0049] Furthermore, the scale unit 10 and the device to which the scale unit 10 is connected and whose position is to be measured are configured to be automatically movable relative to the optical sensor 20 and the device body by the actuator 30. With this configuration, for example, when the position detection system 100 is mounted on a camera with an interchangeable lens, the origin position can be determined without moving the scale unit 10 to the origin position, and a faster AF (Auto Focus) function can be realized.

[0050] The shape of the reset scale 12 is not limited to a square, and may include any shape that allows the origin position to be determined based on its area. For example, the reset scale 12 may be formed in a triangular shape when viewed from above.

[0051] The reset scale 12 may also be formed as a slit having a predetermined area when viewed from above. In this case, the presence of the slit and the area of ​​the slit can be detected by using a simple comparator to detect the difference between the voltage value from the reset PD 24 and a reference voltage value.

[0052] Furthermore, contrary to this embodiment, the optical sensor 20 may be provided so as to be immovable relative to the device whose absolute position is to be detected. For example, if the object to be detected is the position of an interchangeable lens connected to a camera body and moving back and forth relative to the body, the optical sensor 20 is provided so as to be immovable relative to the interchangeable lens but movable relative to the camera body by an actuator. In this case, the scale unit 10 may be provided so as to be movable relative to the device whose absolute position is to be detected. For example, the scale unit 10 is provided so as to be movable relative to the interchangeable lens but immovable relative to the camera body.

[0053] Second Embodiment Next, a reset scale according to a second embodiment will be described with reference to Fig. 6 to Fig. 8. First, a related position detection system will be described with reference to Fig. 6. The related position detection system includes a scale unit 10A and an optical sensor 20A.

[0054] The scale unit 10A is equipped with an incremental scale. This makes it possible to calculate the amount of change in the position of a device connected to the device body and moving relative to the device body. However, the scale unit 10A does not have a special configuration for determining the origin position. Therefore, if the position information of the scale unit 10A is lost when the device is turned on or off, it is necessary to move the scale unit 10A to the origin position.

[0055] 7, the scale unit 10 according to this embodiment includes a reset scale 13 in addition to the incremental scale 11. Like the reset scale 12 in the first embodiment, the reset scale 13 is formed to be wider than the plate-like members of the incremental scale 11 in the movement direction of the scale unit 10. In other words, the reset scale 12 has a different area from the plate-like members of the incremental scale 11 when viewed from above.

[0056] In this embodiment, the optical sensor 20 detects the presence and width of the reset scale 13 based on the reset signal output by the comparator 25. As a result, even if the position information of the scale unit 10 is lost due to turning the device on or off, the origin position can be detected without moving the scale unit 10 to the origin position.

[0057] Furthermore, the number of reset scales does not have to be one. For example, FIG. 8 shows an example in which the scale unit 10 is provided with multiple reset scales 14. The multiple reset scales 14 are arranged at equal intervals in the movement direction of the scale unit 10. In this manner, multiple reset scales 14 may be arranged, and the origin position may be determined by counting the reset signals as pulses. Note that the number of reset scales 14 is not limited to two, and may be three or more. Furthermore, the number of reset scales 14 may vary depending on the equipment in which the position detection system 100 is installed.

[0058] The shape of the reset scales 13 and 14 is not limited to a square, and the shape of the reset scale 12 includes any shape that allows the origin position to be determined based on its area. The reset scales 13 and 14 may also be formed as slits cut into them to have a predetermined area when viewed from above. Even in this case, the presence of the slits and the area of ​​the cut-outs can be detected by using a simple comparator to detect the difference between the voltage value from the reset PD 24 and a reference voltage value.

[0059] 9 to 11, an origin position detection method using the position detection system 100 according to an embodiment of the present disclosure will be described. In this embodiment, the scale unit 10 includes a plurality of reset scales 15 in addition to the incremental scale 11.

[0060] Specifically, the position detection method disclosed herein is a position detection method for a scale section 10 comprising an incremental scale 11 having plate-like members or slits arranged at a predetermined period in a predetermined direction, and a reset scale 15 having an area different from that of the plate-like members or slits, and includes the steps of: irradiating light onto the scale section 10; receiving light reflected or transmitted by the scale section 10 and sending signals corresponding to the incremental scale 11 and the reset scale 12; receiving a signal corresponding to the reset scale 12 from a reset PD 24 and outputting a voltage corresponding to the area of ​​the reset scale 12; and detecting the position of the scale section 10 based on the voltage output corresponding to the area of ​​the reset scale 12.

[0061] The multiple reset scales 15 each have a different width in the movement direction of the scale unit 10. Specifically, the reset scales 15A, 15B, 15C, 15D, 15E, 15F, and 15G each have a width of 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, and 160 μm in the movement direction of the scale unit 10. In other words, each reset scale 15 has a different area. Information regarding the width and area of ​​each reset scale 15 is stored in advance in the memory of the optical sensor 20.

[0062] In the following description, an example of the position detection system 100 will be described in which the position detection system 100 is provided for AF (Auto Focus) of an interchangeable lens of a camera. In other words, it is assumed that the scale unit 10 is connected to the interchangeable lens of the camera. The position detection system 100 detects the AF point by turning on the power of the camera body. Here, the AF point refers to the position of the scale unit 10 (i.e., the interchangeable lens) that corresponds to the position where the lens focuses on the subject.

[0063] In the following description, it is assumed that the scale unit 10 is initially in an initial state, and that the relative positions of the scale unit 10 and the optical sensor 20 change in the order of (A), (B), (C), and (D) as shown in Figure 10.

[0064] First, the user turns on the power of the camera equipped with the position detection system 100 (step S1).

[0065] In this state, the actuator 30 is driven, causing the position detection system 100 to detect the AF point (step S2). Specifically, the position detection system 100 moves the scale unit 10 from the initial state to the AF point while observing the amount of change in the relative position of the scale unit 10 with respect to the optical sensor 20 from the incremental signal using the signal processing unit 26 (step S3). In this embodiment, the first AF point is assumed to be located between the third reset scale 15C and the fourth reset scale 15D.

[0066] With the scale unit 10 positioned at the AF point, the user takes a photo or video (step S4). There are no limitations on the method of taking a photo or video, and the user may take the photo manually or the device may take the photo automatically. After that, the user turns off the power of the camera (step S5).

[0067] The user turns on the camera again (step S6). In this state, the actuator 30 moves the scale unit 10 left and right, or side to side, causing the signal processing unit 26 to detect the presence and width of either or both of the reset scales 15C and 15D. Specifically, the signal processing unit 26 detects the presence and width of either or both of the reset scales 15C and 15D by comparing data regarding the width of the reset scales previously stored in memory with the actual measured values. The signal processing unit 26 then determines the origin position based on the detection results (step S7). In this embodiment, the reset scales 15A to 15G each have a different width, so it is possible to indirectly determine the origin position by detecting the width of any of the reset scales 15A to 15G.

[0068] Thereafter, the position detection system 100 moves the scale unit 10 to the next AF point, starting from either the reset scale 15C or 15D (step S8). With the scale unit 10 positioned at the AF point, the user takes a photo or video (step S9). Figure 10 (D) shows a case where the next AF point is between the fifth reset scale 15E and the sixth reset scale 15F.

[0069] In this way, in this embodiment, when the power is turned on after being turned off, there is no need to move the scale unit 10 to the origin position, and the time until the next AF point is detected can be significantly reduced. This allows, for example, cameras and other devices that use linear actuators to have high performance.

[0070] In this embodiment, the reset scales 15A to 15G each have a different width depending on their position from the origin position. Therefore, the position detection system 100 can conveniently determine the origin position without having to return the scale unit 10 to the origin position, even if it does not have a memory that stores position information of the scale unit 10 when the power is off.

[0071] Note that when the scale unit 10 is moved left, right, or left and right when the power is turned on again, the signal processing unit 26 may be configured to exclude the detection result corresponding to the first reset signal transmitted from the reset PD. That is, the signal processing unit 26 may exclude the first voltage output from the comparator 25 after driving the actuator 30, and detect the position of the scale unit 10 based on the subsequent voltage outputs from the comparator 25. This prevents erroneous detection of the width of the reset scale 15, for example, when the power is turned off while any part of the reset scale 15 and the optical sensor 20 are positioned so as to overlap each other in a top view.

[0072] Once the origin position has been determined, there is no need to determine the origin position again until the scale unit 10 moves to the AF point, and therefore the signal processing unit 26 may be configured not to perform processing to detect the presence and width (area) of the reset scale 12 during that time. In other words, the signal processing unit 26 may detect the position of the scale unit 10 based on the second voltage output from the comparator 25 after driving the actuator 30, and exclude any subsequent voltage outputs from the comparator 25. This allows the processing time by the signal processing unit 26 to be shortened.

[0073] The number of reset scales 15 may vary depending on the device in which the position detection system 100 is installed. The shape of the reset scale 15 is not limited to a square, and may include any shape that allows the origin position to be determined based on its area. The reset scale 15 may also be formed as a slit cut into the scale to have a predetermined area when viewed from above. Even in this case, the presence of the slit and the area of ​​the cut slit can be detected by using a simple comparator to detect the difference between the voltage value from the reset PD 24 and a reference voltage value.

[0074] The device of the present invention can also be realized by a computer and a program, and the program can be recorded on a recording medium or provided via a network. The program of the present disclosure is a program for causing a computer to realize each function of the device according to the present disclosure, and a program for causing a computer to execute each procedure of the method executed by the device according to the present disclosure.

[0075] 10, 10A: Scale section 11: Incremental scale 12, 13, 14, 15, 15A, 15B, 15C, 15D, 15E, 15F, 15G: Reset scale 20, 20A: Optical sensor 21: Light emitting section 22: Incremental PD 23: Reference PD 24: Reset PD 25: Comparator 26: Signal processing section 30: Actuator 100: Position detection system

Claims

1. A position detection system comprising: a scale unit including a first scale having plate-like members or slits arranged at a predetermined period in a predetermined direction, and a second scale having an area different from that of the plate-like members or slits; an incident unit that irradiates the scale unit with light; a light receiving unit that receives the light reflected or transmitted by the scale unit and sends out signals corresponding to the first scale and the second scale respectively; an output unit that receives the signal corresponding to the second scale from the light receiving unit and outputs a voltage corresponding to the area of the second scale; and a position detection unit that detects the position of the scale unit based on the voltage output corresponding to the area of the second scale.

2. The position detection system according to claim 1, wherein the second scale has a plurality of plate-like members or slits with different widths in the predetermined direction, the output unit receives the signal corresponding to the second scale from the light receiving unit and outputs a voltage corresponding to each of the widths of the plurality of plate-like members or slits, and the position detection unit detects the position of the scale unit based on the voltage output corresponding to each of the widths of the plurality of plate-like members or slits.

3. The position detection system according to claim 2, further comprising: an optical sensor including the incident unit and the light receiving unit; and an actuator that moves either one of the scale unit and the optical sensor in the predetermined direction with respect to the other, wherein the output unit receives the signal corresponding to the second scale from the light receiving unit and outputs a voltage corresponding to the area of the second scale in response to the actuator moving either one of the scale unit and the optical sensor in the predetermined direction.

4. The position detection system according to claim 3, wherein the position detection unit excludes the first voltage output from the output unit after driving the actuator, and detects the position of the scale unit based on the subsequent voltage outputs from the output unit.

5. The position detection system according to claim 4, wherein the position detection unit detects the position of the scale unit based on the second voltage output from the output unit after driving the actuator, and excludes the subsequent voltage outputs from the output unit.

6. The position detection unit receives a signal corresponding to the first scale from the light receiving unit that changes in response to the actuator moving either the scale unit or the optical sensor in the predetermined direction, and calculates the displacement amount of the position of the scale unit. The position detection system according to claim 3.

7. The output unit is a comparator, and when the voltage value corresponding to the second scale input from the light receiving unit is greater than a predetermined value, outputs a reset signal indicating that the second scale has been detected as a voltage. The position detection unit detects the position of the scale unit based on the reset signal. The position detection system according to any one of claims 1 to 6.

8. A method for detecting the position of a scale unit including a first scale having plate-like members or slits arranged at a predetermined period in a predetermined direction and a second scale having an area different from that of the plate-like members or slits, the method including: a step of irradiating the scale unit with light; a step of receiving the light reflected or transmitted by the scale unit and sending out signals corresponding to the first scale and the second scale respectively; a step of receiving the signals and performing a voltage output corresponding to the area of the second scale; and a step of detecting the position of the scale unit based on the voltage output.

Images