PHOTOELECTRIC POSITION SENSOR

Abstract

A photoelectric position sensor (1) for detecting position information from a relative movement amount between a scale (2) having a scale pattern and a detection head (3), the photoelectric position sensor (1) comprising: a light-emitting unit (4) configured to emit a light beam; an index (5) configured from a translucent element having a transmissive diffraction grating to diffract the light beam from the light-emitting unit (4) toward the scale (2); and a detection unit (6) configured to detect an interference fringe generated through the index (5) and the scale (2) to output an electrical signal, wherein the index (5) comprises: a first index section (50) consisting of diffraction and non-diffraction sections arranged alternately at a predetermined interval in a longitudinal direction of the scale (2), and a second index section (51) consisting of diffraction and non-diffraction sections arranged alternately at twice the distance of the first index section (50), where the scale pattern includes: a first pattern section (20) consisting of diffraction and non-diffraction sections arranged alternately at a predetermined interval in a longitudinal direction of the scale (2), and a second pattern section (21) consisting of diffraction and non-diffraction sections arranged in a checkerboard pattern at a predetermined pitch in a longitudinal direction of the scale (2), wherein the first pattern section (20) and the second pattern section (21) are alternately placed next to each other in a longitudinal direction of the scale (2), and wherein the detection unit (6) detects the following: an incremental signal by an interference fringe generated by the first index section (50), the first pattern section (20) and the second pattern section (21), and an absolute signal by an interference fringe generated by the second index portion (51), the first pattern portion (20) and the second pattern portion (21).

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This non-provisional application claims priority under USC §119(a) to Japanese Patent Application No. JP 2016-021126 A, filed on February 5, 2016, the entire contents of which are hereby incorporated by reference. BACKGROUNDTechnical field

[0002] The present invention relates to a photoelectric position sensor. Related technology

[0003] Conventionally, a photoelectric position sensor is known that includes a scale having a scale pattern and a detection head that moves along the scale and detects a relative movement amount with the scale. The detection head includes a light-emitting unit for irradiating a light beam toward the scale and a detection unit for detecting interference fringes generated by diffracting from the scale to output an electrical signal. The relative movement amount is calculated based on the electrical signal output from the detection unit.

[0004] The types for detecting the relative movement amount of such a photoelectric position sensor include an incremental (INC) type and an absolute (ABS) type. The INC type continuously detects incremental (INC) patterns provided on the scale at a constant pitch and detects a relative position by counting up or down the number of scale divisions of the scanned INC pattern. The ABS type detects absolute (ABS) patterns randomly provided on the scale at an appropriate timing and detects absolute positions by analyzing the ABS patterns.

[0005] The photoelectric position sensor includes one that uses either the INC type or the ABS type, and one that uses the combined INC-ABS type, which consists in using a juxtaposed scale of the INC pattern and the ABS pattern. However, the combined INC-ABS type is problematic in that, since the INC pattern and the ABS pattern, which are juxtaposed in the transverse direction of the scale, are detected using respective different detection units, when the posture of the detection head is shifted or a ripple occurs in the scale, an error occurs in the position information detected by the detection unit. Thus, a position sensor (photoelectric position sensor) using hybrid integrated INC-ABS scale patterns that combine the INC patterns and the ABS patterns with a series of scale patterns has been proposed (see, for example, Japanese Patent JP 4 008 356 B2).Other position sensors of this type are disclosed, for example, in DE 10 2015 209 716 A1, JP 2005-164 533 A, JP 2013-234 852 A and DE 10 2012 221 566 A1. SUMMARY OF THE INVENTION

[0006] However, in the photoelectric position sensor using the conventional integrated INC-ABS scale patterns as described in Japanese Patent No. 4008356, the INC patterns are thinned to be integrated with the ABS patterns, and are no longer a series of INC patterns continuous at a predetermined pitch. For this reason, there is a problem that the incremental (INC) signal detected by the INC patterns becomes an incomplete signal in a thinned state and has deteriorated accuracy because the INC signal to be detected has a dropout compared to that using the INC patterns in a non-thinned state, and the detection accuracy of the photoelectric position sensor decreases.

[0007] An object of the present invention is to provide a photoelectric position sensor capable of reducing errors in position information between the INC patterns and the ABS patterns and capable of improving detection accuracy by detecting an INC signal without signal dropout.

[0008] The present invention provides a photoelectric position sensor according to claim 1. Further aspects of the invention are the subject of the subclaims, the drawings and the description of embodiments.

[0009] Diffraction is a phenomenon in which, when a light beam is intercepted by an obstacle, the light beam spreads around the obstacle. A diffraction grating that has diffraction portions and non-diffraction portions to achieve this phenomenon includes a transmissive type in which a light beam transmitted through the diffraction portions and non-diffraction portions from the emitted light beam is diffracted at any angle, and a reflective type in which the light beam reflected by the diffraction portions and non-diffraction portions from the emitted light beam is diffracted at any angle.

[0010] According to the present invention, diffracting the light beam from the light-emitting unit by two types of index portions of a predetermined pitch and a pitch twice the predetermined pitch and a series of scale patterns in which two types of pattern portions having different arrangement patterns are alternately juxtaposed to generate interference fringes enables the detection of an incremental (INC) signal and an absolute (ABS) signal.

[0011] In the present invention, since the INC signal to be detected is detected as an INC signal in a non-dropout state, the detection accuracy of the position information can be improved even when the INC pattern and the ABS pattern are integrated into a series of scale patterns to be arranged. Furthermore, since the ABS signal can also be obtained simultaneously, more accurate position information can be detected, and the accuracy of the position information to be detected can be improved.

[0012] Furthermore, even if the position of the detection head deviates from the scale or there is a ripple on the scale, the errors in the position information conventionally caused by separate reading can be reduced, and therefore the detection unit can reliably detect the position information.

[0013] In addition, although a signal from each pattern is detected by using an optical lens system in a normal photoelectric position sensor, since the present invention has a configuration that can be achieved without using a lens and the like, the photoelectric position sensor can be configured with a small number of components, and cost reduction and miniaturization can be achieved.

[0014] In the photoelectric position sensor of the present invention, it is preferred that the first pattern portion and the second pattern portion are juxtaposed such that the mutual lengths of the first pattern portion and the second pattern portion in the longitudinal direction of the scale form an M-sequence code.

[0015] Typically, a Gray code is used for the ABS pattern to generate the ABS signal. The Gray code is a type of binary number called an alternating binary code, and is characterized by the fact that the alternating bit is always restricted to one position when the codes of adjacent numerical values are compared. As a code with a resolution equivalent to this Gray code, there is an arrangement pattern based on an M-sequence code, which is part of a pseudorandom code.

[0016] The M-sequence code is formed by (2 to the power of n - 1) codes consisting of 0 or 1, and is a pattern in which all combinations of n consecutive codes are different code series. The detection unit can detect the absolute position from the arrangement pattern of the M-sequence code by reading n consecutive codes of 0 or 1.

[0017] Arranging the first pattern portion and the second pattern portion in the longitudinal direction of the scale so that their mutual lengths form an M-sequence code enables the ABS signal to be calculated, which appears according to this arrangement, to be encoded as 0 or 1, and thus more detailed position information can be calculated.

[0018] It is preferred that the first index section and the second index section are placed next to each other in a transverse direction of the scale.

[0019] By this configuration, the index can shorten the length in the longitudinal direction of the scale compared with the case where they are juxtaposed in the longitudinal direction of the scale; and therefore, cost reduction and miniaturization can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] They show: Fig. 1 is a perspective view showing a photoelectric position sensor according to a first embodiment of the present invention; Fig. 2 a scale of the photoelectric position sensor; Fig. 3 an index of the photoelectric position sensor; Fig. 4A is a diagram illustrating how an INC signal is generated by a scale and the first index section; Fig. 4B is a diagram illustrating how an ABS signal is generated by the scale and the second index section; Fig. 5A the first index section in an index; Fig. 5B the second pattern section in the scale; Fig. 5C shows an operation of the photoelectric position sensor through the second pattern section and the first index section in cross section along the line AA Fig. 5A and Fig. 5B seen; Fig. 6A the second index section in the index; Fig. 6B the second pattern section; Fig. 6C shows an operation of the photoelectric position sensor through the second pattern section and the second index section in cross section along the line BB Fig. 6A and Fig. 6B seen; Fig. 7 is a perspective view showing a photoelectric position sensor according to a second embodiment of the present invention; Fig. 8 a scale of the photoelectric position sensor; Fig. 9 is a perspective view showing a photoelectric position sensor according to a third embodiment of the present invention; Fig. 10 an index of the photoelectric position sensor; Fig. 11 shows a modified example of the index of the photoelectric position sensor according to each embodiment of the present invention; and Fig. 12 shows a modified example of the scale pattern of the photoelectric position sensor according to each embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTSFirst Embodiment

[0021] Hereinafter, the first embodiment of the present invention will be described with reference to the drawings.

[0022] In each figure, the longitudinal direction of the scale is referred to as the X direction, the transverse direction as the Y direction, and the height direction as the Z direction, and in the following description, they are sometimes referred to as the X direction, Y direction, and Z direction, respectively.

[0023] Fig. 1 is a perspective view showing a photoelectric position sensor according to a first embodiment of the present invention.

[0024] The photoelectric position sensor 1 comprises an elongated scale 2 and a detection head 3 for moving along the scale 2 and detecting the position information from the relative movement amount with the scale 2.

[0025] The detection head 3 includes a light-emitting unit 4 for irradiating a light beam, an index 5 for diffracting the light beam from the light-emitting unit 4 toward the scale 2, and a detection unit 6 for detecting interference fringes generated by the scale 2 and the index 5 to output an electrical signal. The detection head 3, which includes these parts, is provided integrally so as to be capable of reciprocating relative to the scale 2 in the X direction.

[0026] The scale 2 is made of a translucent member, such as glass, capable of transmitting a light beam from the light-emitting unit 4, and includes a transmissive diffraction grating provided on one side of the scale 2. In the transmissive diffraction grating, the diffraction portion is a transmission portion, and the non-diffraction portion is a non-transmission portion. The transmissive diffraction grating provided on one side of the scale 2 has an alternating arrangement in the X direction of a first pattern portion 20 consisting of transmission portions and non-transmission portions alternately juxtaposed at a predetermined pitch P in the X direction, and a second pattern portion 21 consisting of transmission portions and non-transmission portions arranged in a checkerboard pattern at a predetermined pitch to be provided in the X direction.

[0027] The light-emitting unit 4 uses, for example, an LED (light-emitting diode). It should be understood that the light-emitting unit 4 is not limited to an LED, but can also use any light source. Furthermore, the light-emitting unit 4 is installed at an appropriate angle to irradiate the scale 2 and the index 5 with a light beam.

[0028] The index 5 is made of a translucent member, such as glass, capable of transmitting a light beam from the light-emitting unit 4, and is installed facing the scale 2 so as to overlap on one side in the Z direction of the scale 2 (upward). Then, a transmissive diffraction grating is provided on one side of the index 5. Specifically, a first index portion 50 consisting of transmitting portions and non-transmitting portions alternately juxtaposed at a predetermined pitch in the X direction and a second index portion 51 consisting of transmitting portions and non-transmitting portions alternately juxtaposed at twice the pitch of the first index portion 50 are provided, and the first index portion 50 and the second index portion 51 are juxtaposed in the Y direction of the index 5.

[0029] The detection unit 6 uses a PDA (photodiode array) and is installed facing the scale 2 so as to overlap on another side in the Z direction of the scale 2 (downward). That is, the index 5 and the detection unit 6 are installed facing each other so as to overlap across the scale 2 and are installed in positions where the respective distances from the scale 2 are the same.

[0030] The PDA is a detector capable of simultaneously measuring a plurality of interference fringes. Note that the detection unit 6 is not limited to a PDA, but can use any detector, such as a PSD (position dependent device) and a CCD (charge-coupled device).

[0031] The detection unit 6 detects the INC signal using the interference fringes generated by the first index portion 50, the first pattern portion 20, and the second pattern portion 21, and detects the ABS signal using the interference fringes generated by the second index portion 51, the first pattern portion 20, and the second pattern portion 21. The INC signal and the ABS signal detected by the detection unit 6 are analyzed by a microcomputer (not shown) and the like and displayed as position information on a display unit (not shown).

[0032] The photoelectric position sensor 1 of the present invention is configured by the scale 2 and the detection head 3 including the light emitting unit 4, the index 5 and the detection unit 6 as described above.

[0033] Fig. Figure 2 is a diagram showing the scale of the photoelectric position sensor.

[0034] As in Fig. 2, the scale 2 is configured to include a scale pattern in which the first pattern portion 20 and the second pattern portion 21 are alternately arranged in the X direction. This first pattern portion 20 and this second pattern portion 21 are arranged such that their mutual lengths in the X direction represent an M-sequence code.

[0035] The first pattern portion 20 includes pass-through portions 20a and non-pass-through portions 20b arranged alternately in the X direction. The pass-through portions 20a and non-pass-through portions 20b are arranged at a predetermined pitch P in the X direction, and the length of the non-pass-through portion 20b in the X direction is set to P / 2.

[0036] The second pattern section 21 includes pass-through sections 21a and non-pass-through sections 21b arranged in a checkerboard pattern. The pass-through sections 21a and the non-pass-through sections 21b are arranged at a predetermined pitch P in the X direction and a pitch Q in the Y direction. Furthermore, the length of the non-pass-through section 21b in the X direction is set to P / 2, and the length in the Y direction is set to Q / 2.The distance Q in the Y direction may be the same as the predetermined distance P in the X direction, whereby the non-passage portion 21b can be formed in a square shape, may be larger than the predetermined distance P, whereby the non-passage portion 21b can be formed in a rectangular shape that is longer in the Y direction, and may be smaller than the predetermined distance P, whereby the non-passage portion 21b can be formed in a rectangular shape that is longer in the X direction.

[0037] Fig. 3 is a diagram showing the index of the photoelectric position sensor.

[0038] As in Fig. 3, the index 5 includes a first index portion 50 and a second index portion 51, and the first index portion 50 and the second index portion 51 are juxtaposed in the Y direction of the index 5.

[0039] The first index section 50 includes pass-through sections 50a and non-pass-through sections 50b arranged alternately in the X direction. The pass-through sections 50a and the non-pass-through sections 50b are arranged at a predetermined pitch P in the X direction, and the length of the non-pass-through section 50b in the X direction is set to P / 2.

[0040] The second index section 51 includes pass-through sections 51a and non-pass-through sections 51b arranged alternately in the X direction. The pass-through sections 51a and the non-pass-through sections 51b are arranged at a predetermined pitch 2P, which is twice the predetermined pitch P, in the X direction, and the length of the non-pass-through section 51b in the X direction is set to P.

[0041] The first pattern section 20 and the second pattern section 21 (see Fig. 2) of the scale 2 and the first index portion 50 of the index 5, the respective passing portions 20a, 21a, and 50a and non-passing portions 20b, 21b, and 50b, whose predetermined distances P in the X direction are set to be the same. That is, the lengths of the passing portions 20a, 21a, and 50a and the non-passing portions 20b, 21b, and 50b in the X direction are set to be equal to P / 2.

[0042] Fig. 4A and Fig. 4B are diagrams showing signals detected by the photoelectric position sensor.

[0043] In particular, Fig. 4A is a diagram illustrating how the INC signal 7 is generated by the scale 2 and the first index section 50, and Fig. Figure 4B is a diagram illustrating how the ABS signal 8 is generated by the scale 2 and the second index section 51.

[0044] As in Fig. 4A, the INC signal 7 is generated by the scale 2 and the first index section 50 and detected by the detection unit 6 (see Fig. 1).

[0045] First, the scale 2 is irradiated with the light beam from the light-emitting unit 4 through the transmission portions 50a and the non-transmission portions 50b of the first index portion 50 in the index 5 (see Fig. 3). Then, the light beam transmitted through the transmitting portions 50a of the first index portion 50 generates interference fringes through the transmitting portions 20a and the non-transmitting portions 20b of the first pattern portion 20 in the scale 2 (see Fig. 2). The detection unit 6 detects a signal 70 from the generated interference fringes.

[0046] Next, the scale 2 is irradiated with the light beam from the light-emitting unit 4 through the transmitting portions 50a and the non-transmitting portions 50b of the first index portion 50 in the index 5. Then, the light beam transmitted through the transmitting portions 50a of the first index portion 50 generates interference fringes through the transmitting portions 21a and the non-transmitting portions 21b of the second pattern portion 21 in the scale 2 (see Fig. 2). The detection unit 6 detects a signal 71 from the generated interference fringes.

[0047] Since the signals 70 and 71 detected by the detection unit 6 are signals having the same period and phase, superimposing them on each other generates a single signal. Therefore, the photoelectric position sensor 1 can detect the INC signal 7 based on analysis by a microcomputer and the like (not shown).

[0048] As in Fig. 4B, the ABS signal 8 is generated by the scale 2 and the second index section 51 and detected by the detection unit 6 (see Fig. 1).

[0049] First, the scale 2 is irradiated with the light beam from the light-emitting unit 4 through the transmission portions 51a and the non-transmission portions 51b of the second index portion 51 in the index 5 (see Fig. 3). Then, the light beam transmitted through the transmitting portions 51a of the second index portion 51 generates interference fringes through the transmitting portions 20a and the non-transmitting portions 20b of the first pattern portion 20 in the scale 2 (see Fig. 2). The detection unit 6 detects a signal 80 from the generated interference fringes.

[0050] Next, the scale 2 is irradiated with the light beam from the light-emitting unit 4 through the transmitting portions 51a and the non-transmitting portions 51b of the second index portion 51 in the index 5. Then, the light beam transmitted through the transmitting portions 51a of the second index portion 51 generates interference fringes through the transmitting portions 21a and the non-transmitting portions 21b of the second pattern portion 21 in the scale 2 (see Fig. 2). The detection unit 6 detects a plurality of signals with the same period and a phase shift of 180° from the generated interference fringes. The detection unit 6 cannot detect any signal because the plurality of signals with the same period and a phase shift of 180° cancel each other out. Therefore, the detection unit 6 detects the non-signal 81.

[0051] The operation of the photoelectric position sensor 1 in that the second pattern section 21 has the checkerboard pattern in the scale 2 and the index 5 will be explained below with reference to Fig. 5A to 5C and Fig. 6A to 6C.

[0052] Fig. 5A to 5C and Fig. 6A to 6C are diagrams illustrating the operation of the scale 2 and the index 5 of the photoelectric position sensor 1.

[0053] Fig. 5A depicts the first index section 50 in the index 5. Fig. Figure 5B shows the second pattern section 21 in scale 2. Fig. 5C illustrates an operation of the photoelectric position sensor 1 through the second pattern portion 21 and the first index portion 50 in cross section along the line AA Fig. 5A and Fig. 5B seen from.

[0054] In the first index section 50, which is Fig. 5A, the passage portions 50a and the non-passage portions 50b are alternately arranged at a predetermined pitch P in the X-direction of the scale 2. In the second pattern portion 21 shown in Fig. 5B, the transmission portions 21a and 22a and the non-transmission portions 21b and 22b are arranged in a checkerboard pattern, and these transmission portions 21a and 22a and the non-transmission portions 21b and 22b are each arranged at a predetermined pitch P in the X direction, are juxtaposed in the Y direction of the scale 2, and are arranged to be mutually shifted by half a period in the X direction.

[0055] As in Fig. As shown in Fig. 5C, the first index portion 50, in which the non-transmitting portions 50b having a length P / 2 in the X direction are arranged at a predetermined pitch P, diffracts the light beam from the light-emitting unit 4 and transmits the diffracted light beam toward the second pattern portion 21. The second pattern portion 21 diffracts the light beam from the light-emitting unit 4 through the transmitting portions 21a and the non-transmitting portions 21b, the diffracted light beam advances in the direction indicated by the solid arrow to form interference fringes, and the interference fringes are detected by the detecting unit 6 (not shown) as a signal S1.

[0056] In addition, the light beam from the light-emitting unit 4, which is diffracted by the transmission portions 22a and the non-transmission portions 22b of the second pattern portion 21, advances in the direction of the two-dot chain arrow to form interference fringes, and the interference fringes are detected by the detection unit 6 as a signal S2. Therefore, since a plurality of signals S1 and S2 having the same phase and the same period are detected from the interference fringes by the detection unit 6, and these signals S1 and S2 are signals with the same phase and the same period, the signals S1 and S2 are superimposed on each other and detected as the signal S1, as shown in FIG. Fig. 4A shown.

[0057] Fig. 6A depicts the second index section 51 in the index 5. Fig. Figure 6B depicts the second pattern section 21. Fig. 6C illustrates an operation of the photoelectric position sensor 1 by the second pattern portion 21 and the second index portion 51 in cross section along the line BB Fig. 6A and Fig. 6B seen from.

[0058] In the second index section 51, which is Fig. 6A, the passing portions 51a and the non-passing portions 51b are alternately arranged at a predetermined pitch 2P, which is twice as large as the predetermined pitch P, in the X direction of the scale 2. The second pattern portion 21 shown in Fig. 6B is the same as the one shown in Fig. 5B shown.

[0059] As in Fig. As shown in Fig. 6C, the second index portion 51, in which the non-transmitting portions 51b having a length P in the X direction are arranged at a predetermined pitch 2P, diffracts the light beam from the light-emitting unit 4 and transmits the diffracted light beam toward the second pattern portion 21. The second pattern portion 21 diffracts the light beam from the light-emitting unit 4 through the transmitting portions 21a and the non-transmitting portions 21b, the diffracted light beam advances in the direction indicated by the solid arrow to form interference fringes, and the interference fringes are detected by the detecting unit 6 (not shown) as a signal S3.

[0060] In addition, the light beam from the light-emitting unit 4, which is diffracted by the transmitting portions 22a and the non-transmitting portions 22b of the second pattern portion 21, advances in the direction of the double-dashed arrow to form interference fringes, and the interference fringes are detected by the detecting unit 6 as a signal S4. Therefore, two types of signals S3 and S4, which have the same period and are 180° out of phase, are detected by the detecting unit 6 from the interference fringes. These two types of signals S3 and S4 cancel each other out because they have the same period and are 180° out of phase, and the detecting unit 6 detects the non-signal S1 as shown in FIG. Fig. 4B shown.

[0061] As in Fig. 4B, the detection unit 6 detects the signal 80 and the non-signal 81 by the above-described operation. At this time, since the first pattern portion 20 and the second pattern portion 21 are arranged to be an arrangement pattern of the M-sequence code, the detected signal 80 and the non-signal 81 are analyzed by a microcomputer (not shown) and the like, whereby the ABS signal 8 can be detected.

[0062] According to the present embodiment as described above, the following actions and effects can be achieved. (1) The photoelectric position sensor 1 transmits the light beam from the light-emitting unit 4 to the index 5 and generates interference fringes by further transmitting the light beam transmitted to the index 5 to the scale 2; and the INC signal 7 to be detected from the generated interference fringes is detected as a single INC signal 7 in a non-failure state; and therefore, the detection accuracy of the position information can be improved even when the INC pattern and the ABS pattern are integrated into a series of scale patterns to be arranged. (2) In addition, since the ABS signal 8 can also be obtained at the same time as the INC signal 7, more accurate position information can be detected, and the accuracy of the position information to be detected can be improved.

[0063] (3) Even if the position of the detection head 3 deviates from the scale 2 or there is a corrugation in the scale 2, the scale 2 further includes the first pattern portion 20 and the second pattern portion 21 in a series of scale patterns, thereby reducing the error in the position information caused by separately reading the INC pattern and the ABS pattern. Therefore, the detection unit 6 can reliably detect the position information.

[0064] (4) Since the photoelectric position sensor 1 has the configuration that can be achieved without using lenses and the like by using the scale 2 and the index 5, the photoelectric position sensor 1 can be configured with a small number of components, and the cost reduction and miniaturization can be achieved. (5) Arranging the first pattern portion 20 and the second pattern portion 21 of the scale 2 in the X direction so that their mutual lengths form an M-sequence code, and encoding the ABS signal to be calculated, which appears according to this arrangement, as 0 or 1, enables the calculation of more detailed position information. (6) Since juxtaposing the first index portion 50 and the second index portion 51 in the Y direction in the index 5 enables the length of the index 5 in the X direction of the scale 2 to be shortened compared with the case of juxtaposing in the X direction, cost reduction and miniaturization can be achieved. Second embodiment

[0065] Hereinafter, the second embodiment of the present invention will be described with reference to the drawings.

[0066] Although in the first embodiment, the transmitting diffraction grating is provided in the scale 2 and the index 5, the reflecting diffraction grating may be provided in the scale 2, and the transmitting diffraction grating may be provided in the index 5.

[0067] Fig. 7 is a perspective view showing a photoelectric position sensor according to the second embodiment of the present invention.

[0068] The photoelectric position sensor 1A includes an elongated scale 2A and a detection head 3A for moving along the scale 2A and detecting the position information from the relative movement amount with the scale 2A.

[0069] The detection head 3A includes a light-emitting unit 4 for irradiating a light beam, an index 5 for transmitting the light beam from the light-emitting unit 4 toward the scale 2A, and a detection unit 6 for detecting interference fringes generated by the scale 2A and the index 5 to output an electrical signal. The detection head 3A, which includes these parts, is provided integrally so as to be capable of reciprocating relative to the scale 2A in the X direction.

[0070] The scale 2A consists of a member capable of reflecting the light beam emitted from the light-emitting unit 4, such as glass coated with metal on one side, and the reflective diffraction grating is provided on one side of the scale 2A. In the reflective diffraction grating, the diffraction portion is a reflection portion, and the non-diffraction portion is a non-reflection portion.The reflective diffraction grating provided on one side of the scale 2A has an alternating arrangement in the X direction of a first pattern portion 20A consisting of reflection portions and non-reflection portions alternately juxtaposed at a predetermined pitch P in the X direction, and a second pattern portion 21A consisting of reflection portions and non-reflection portions arranged in a checkerboard pattern at a predetermined pitch to be provided in the X direction.

[0071] Although the light-emitting unit 4 and the index 5 are the same as in Fig. 1, the light-emitting unit 4 is installed at a suitable angle to reflect the emitted light beam onto the scale 2A.

[0072] The detection unit 6 is installed facing the scale 2A on one side in the Z direction of the scale 2A (upward). That is, the index 5 and the detection unit 6 are juxtaposed in the X direction on one side in the Z direction of the scale 2A (upward) and are installed in positions where the respective distances from the scale 2A are the same.

[0073] The detection unit 6 detects the INC signal using the interference fringes generated by the first index portion 50, the first pattern portion 20A, and the second pattern portion 21A, and detects the ABS signal using the interference fringes generated by the second index portion 51, the first pattern portion 20A, and the second pattern portion 21A. The INC signal and the ABS signal detected by the detection unit 6 are analyzed by a microcomputer (not shown) and the like and displayed as position information on a display unit (not shown).

[0074] The photoelectric position sensor 1A of the present invention is configured by the scale 2A and the detection head 3A including the light emitting unit 4, the index 5 and the detection unit 6 as described above.

[0075] Fig. 8 is a diagram illustrating the scale of the photoelectric position sensor according to the second embodiment.

[0076] As in Fig. As shown in Figure 8, the scale 2A, which has a reflective diffraction grating, is configured to include a scale pattern in which the first pattern portion 20A and the second pattern portion 21A are alternately arranged in the X direction. This first pattern portion 20A and this second pattern portion 21A are arranged such that their mutual lengths in the X direction represent an M-sequence code.

[0077] The first pattern portion 20A includes reflection portions 20c and non-reflection portions 20d arranged alternately in the X direction. The reflection portions 20c and the non-reflection portions 20d are arranged at a predetermined pitch P in the X direction, and the length of the non-reflection portion 20d in the X direction is set to P / 2.

[0078] The second pattern portion 21A includes reflection portions 21c and non-reflection portions 21d arranged in a checkerboard pattern. The reflection portions 21c and the non-reflection portions 21d are arranged at a predetermined pitch P in the X direction and at a pitch Q in the Y direction. Furthermore, the length of the non-reflection portion 21d in the X direction is set to P / 2, and the length in the Y direction is set to Q / 2.The distance Q in the Y direction may be the same as the predetermined distance P in the X direction, whereby the non-reflection portion 21d may be formed in a square shape; may be larger than the predetermined distance P, whereby the non-reflection portion 21d may be formed in a rectangular shape that is longer in the Y direction; and may be smaller than the predetermined distance P, whereby the non-reflection portion 21d may be formed in a rectangular shape that is longer in the X direction.

[0079] In the first pattern section 20A and the second pattern section 21A of the scale 2A and in the first index section 50 of the index 5 (see Fig. 3) the lengths of the reflection sections 20c and 21c, the transmission section 50a, the non-reflection sections 20d and 21d and the non-transmission section 50b in the X direction are all set to P / 2.

[0080] This configuration causes the light beam from the light-emitting unit 4 to pass through the first index portion 50, and the first pattern portion 20A and the second pattern portion 21A of the scale 2A, which have the reflective diffraction grating, are irradiated with the light beam diffracted by the transmission. The radiated light beam is reflected by the first pattern portion 20A and the second pattern portion 21A, the light beam diffracted by the reflection is applied to the detection unit 6 as interference fringes, and the detection unit 6 detects the INC signal 7 from the interference fringes (see Fig. 4A).

[0081] In addition, the light beam from the light-emitting unit 4 passes through the second index portion 51, and the first pattern portion 20A and the second pattern portion 21A of the scale 2A, which have the reflective diffraction grating, are irradiated with the light beam diffracted by the transmission. The irradiated light beam is reflected by the first pattern portion 20A and the second pattern portion 21A, the light beam diffracted by the reflection is applied to the detection unit 6 as interference fringes, and the detection unit 6 detects the ABS signal 8 from the interference fringes (see Fig. 4B).

[0082] According to the present embodiment, as described above, the same actions and effects as items (2) to (6) in the above embodiment can be achieved, and the following actions and effects can be achieved.

[0083] (7) The photoelectric position sensor 1A transmits the light beam from the light-emitting unit 4 to the index 5 and generates interference fringes by causing the light beam transmitted through the index 5 to be reflected by the scale 2A, and the INC signal 7 to be detected from the generated interference fringes is detected as a single INC signal 7 in a non-failure state, and accordingly, the detection accuracy of the position information can be improved even if the INC pattern and the ABS pattern are integrated into a series of scale patterns to be arranged. Third embodiment

[0084] Hereinafter, the third embodiment of the present invention will be described with reference to the drawings.

[0085] Although in the second embodiment, the reflective diffraction grating is provided in the scale 2A and the transmissive diffraction grating is provided in the index 5, a transmissive diffraction grating may be provided in the scale 2 and a reflective diffraction grating may be provided in the index 5.

[0086] Fig. 9 is a perspective view showing a photoelectric position sensor according to the third embodiment of the present invention.

[0087] The photoelectric position sensor 1B includes an elongated scale 2 and a detection head 3B for moving along the scale 2 and detecting the position information from the relative movement amount with the scale 2.

[0088] The detection head 3B includes a light-emitting unit 4 for irradiating a light beam, an index 5B for reflecting the light beam from the light-emitting unit 4 toward the scale 2, and a detection unit 6 for detecting interference fringes generated by the scale 2 and the index 5B to output an electrical signal. The detection head 3B, which includes these parts, is provided integrally so as to be capable of reciprocating relative to the scale 2 in the X direction.

[0089] Although the scale 2 and the light-emitting unit 4 are the same as in Fig. 1, the light-emitting unit 4 is installed at a suitable angle to cause the index 5B to reflect the emitted light beam.

[0090] The index 5B consists of an element capable of reflecting the light beam emitted from the light-emitting unit 4, such as glass coated with metal on one side, and is installed facing the scale 2 on the other side in the Z direction of the scale 2 (downward). Then, a reflective diffraction grating is provided on one side of the index 5B. In the reflective diffraction grating, the diffraction portion is a reflection portion, and the non-diffraction portion is a non-reflection portion.In the reflective diffraction grating provided on one side of the index 5B, a first index portion 50B consisting of reflection portions and non-reflection portions alternately arranged at a predetermined pitch in the X direction and a second index portion 51B consisting of reflection portions and non-reflection portions alternately juxtaposed at twice the pitch of the first index portion 50B are provided, and the first index portion 50B and the second index portion 51B are juxtaposed in the Y direction of the index 5B.

[0091] The detection unit 6 is installed facing the scale 2 on one side in the Z direction of the scale 2 (upward). That is, the index 5B and the detection unit 6 are installed facing each other across the scale 2, and are installed in positions where the respective distances from the scale 2 are the same.

[0092] The detection unit 6 detects the INC signal using the interference fringes generated by the first index portion 50B, the first pattern portion 20, and the second pattern portion 21, and detects the ABS signal using the interference fringes generated by the second index portion 51B, the first pattern portion 20, and the second pattern portion 21. The INC signal and the ABS signal detected by the detection unit 6 are analyzed by a microcomputer (not shown) and the like and displayed as position information on a display unit (not shown).

[0093] The photoelectric position sensor 1B of the present invention is configured by the scale 2 and the detection head 3B including the light emitting unit 4, the index 5B and the detection unit 6 as described above.

[0094] Fig. 10 is a diagram showing the index of the photoelectric position sensor according to the third embodiment.

[0095] As in Fig. 10, the index 5B includes a first index portion 50B and a second index portion 51B, and the first index portion 50B and the second index portion 51B are juxtaposed in the Y direction of the index 5B.

[0096] The first index portion 50B includes reflection portions 50c and non-reflection portions 50d arranged alternately in the X direction. The reflection portions 50c and the non-reflection portions 50d are arranged at a predetermined pitch P in the X direction, and the length of the non-reflection portion 50d in the X direction is set to P / 2.

[0097] The second index portion 51B includes reflection portions 51c and non-reflection portions 51d arranged alternately in the X direction. The reflection portions 51c and the non-reflection portions 51d are arranged at a predetermined distance 2P, which is twice the predetermined distance P, in the X direction, and the length of the non-reflection portion 51d in the X direction is set to P.

[0098] The first sample section 20 and the second sample section 21 of scale 2 (see Fig. 2) and the first index portion 50B of the index 5B, the respective transmission portions 20a and 21a, the reflection portion 50c, the non-transmission portions 20b and 21b, and the non-reflection portion 50d, whose predetermined distances P in the X direction are set equal. That is, the lengths of the transmission portions 20a and 21a, the reflection portion 50c, the non-transmission portions 20b and 21b, and the non-reflection portion 50d in the X direction are all set to P / 2.

[0099] This configuration causes a light beam from the light-emitting unit 4 to be reflected by the first index portion 50B having a reflective diffraction grating, and the light beam diffracted by the reflection is applied to the first pattern portion 20 and the second pattern portion 21 of the scale 2. The emitted light beam passes through the first pattern portion 20 and the second pattern portion 21, the light beam diffracted by the transmission is applied to the detection unit 6 as interference fringes, and the detection unit 6 detects the INC signal 7 from the interference fringes (see Fig. 4A).

[0100] In addition, a light beam from the light-emitting unit 4 is reflected by the second index portion 51B having a reflective diffraction grating, and the light beam diffracted by the reflection is applied to the first pattern portion 20 and the second pattern portion 21 of the scale 2. The emitted light beam passes through the first pattern portion 20 and the second pattern portion 21, the light beam diffracted by the transmission is applied to the detection unit 6 as interference fringes, and the detection unit 6 detects the ABS signal 8 from the interference fringes (see Fig. 4B).

[0101] According to the present embodiment, as described above, the same actions and effects as (2) to (6) in the above embodiment can be achieved, and the following actions and effects can be achieved.

[0102] (8) The photoelectric position sensor 1B generates interference fringes by causing the index 5B to reflect the light beam from the light-emitting unit 4 and transmitting the light beam 20 reflected by the index 5B to the scale 2, and the INC signal 7 to be detected from the generated interference fringes is detected as a single INC signal 7 in a non-failure state, and accordingly, the detection accuracy of the position information can be improved even if the INC pattern and the ABS pattern are integrated into a series of scale patterns to be arranged. Change of embodiments

[0103] It should be noted that the present invention is not limited to each of the embodiments, and variations, improvements, and the like within the scope of achieving the object of the present invention are included in the present invention.

[0104] For example, although in each of the embodiments, the first index portion 50 or 50B and the second index portion 51 or 51B are juxtaposed at the index 5 or 5B in the Y direction, as shown in Fig. 11, in the index 5C having the first index portion 50C and the second index portion 51C, which consists of diffractive portions 51e (transmitting portions or reflecting portions) and non-diffractive portions 51f (non-transmitting portions or non-reflecting portions), the first index portion 50C and the second index portion 51C may be arranged in the X direction. It should be noted that in Fig. 11, the first index portion 50C is arranged on the left side in the X direction, and the second index portion 51C is arranged on the right side, but the second index portion 51C may be arranged on the left side in the X direction, and the first index portion 50C may be arranged on the right side. Thus, even if the first index portion 50C and the second index portion 51C are juxtaposed in the longitudinal direction of the scale 2 or 2A, the detection position of the detection unit 6 corresponding to each of the index portions 50C and 51C is predetermined, and therefore the INC signal 7 and the ABS signal 8 can be detected by calculating the detected interference fringes accordingly.

[0105] In addition, although in each of the embodiments, the non-transmission portion 21b of the second pattern portion 21 and the non-reflection portion 21d of the second pattern portion 21A in the scale 2 or 2A are rectangular, the shape is not limited to a rectangle and may be any shape. For example, as shown in Fig.As shown in FIG. 12, the second pattern portion 21C, which includes one of the transmitting diffraction grating and the reflecting diffraction grating, may form the non-diffraction portions 21f in a circular shape. Furthermore, the second pattern portion 21C may form the diffraction portions 21e in a circular shape. That is, the diffraction portions 21e and the non-diffraction portions 21f of the second pattern portion 21C may be mutually arranged in a checkerboard pattern in the X and Y directions. The individual shapes of the diffraction portion 21e and the non-diffraction portion 21f are not particularly limited. Suitable shapes, such as an elliptical shape or any polygonal shape, may be selected in addition to the rectangular shape and the circular shape.

[0106] Although in each of the embodiments, the first pattern portion 20 or 20A and the second pattern portion 21 or 21A of the scale 2 or 2A are arranged in the arrangement pattern of the M-sequence code, they are not limited thereto and need only be arranged in an arbitrary arrangement pattern, such as the pseudorandom arrangement. That is, the ABS signal only needs to be detected from the respective pattern of the interference fringes based on the arrangement of the first pattern portion 20 or 20A and the second pattern portion 21 or 21A, and the arrangement pattern can be set arbitrarily.

[0107] Although in the second embodiment, the detection head 3A includes the index 5 and the detection unit 6 juxtaposed in the X direction, the index 5 and the detection unit 6 may be juxtaposed in the Y direction. INDUSTRIAL APPLICABILITY

[0108] As described above, the present invention can be applied to a photoelectric position sensor capable of reducing errors in position information between the INC pattern and the ABS pattern and capable of improving detection accuracy by detecting the INC signal without signal dropout.

Claims

[1] A photoelectric position sensor (1) for detecting position information from a relative movement amount between a scale (2) having a scale pattern and a detection head (3), the photoelectric position sensor (1) comprising: a light-emitting unit (4) configured to emit a light beam; an index (5) configured from a translucent element having a transmissive diffraction grating to diffract the light beam from the light-emitting unit (4) toward the scale (2); and a detection unit (6) configured to detect an interference fringe generated through the index (5) and the scale (2) to output an electrical signal, wherein the index (5) comprises: a first index section (50) consisting of diffraction and non-diffraction sections arranged alternately at a predetermined interval in a longitudinal direction of the scale (2), and a second index section (51) consisting of diffraction and non-diffraction sections arranged alternately at twice the distance of the first index section (50), where the scale pattern includes: a first pattern section (20) consisting of diffraction and non-diffraction sections arranged alternately at a predetermined interval in a longitudinal direction of the scale (2), and a second pattern section (21) consisting of diffraction and non-diffraction sections arranged in a checkerboard pattern at a predetermined pitch in a longitudinal direction of the scale (2), wherein the first pattern section (20) and the second pattern section (21) are alternately placed next to each other in a longitudinal direction of the scale (2), and wherein the detection unit (6) detects the following: an incremental signal by an interference fringe generated by the first index section (50), the first pattern section (20) and the second pattern section (21), and an absolute signal by an interference fringe generated by the second index portion (51), the first pattern portion (20) and the second pattern portion (21). [2] Photoelectric position sensor (1) according to claim 1, wherein the first pattern portion (20) and the second pattern portion (21) are juxtaposed such that the mutual lengths of the first pattern portion (20) and the second pattern portion (21) in the longitudinal direction of the scale (2) form an M-sequence code, the M-sequence code being formed by (2 to the power of n-1) codes consisting of 0 or 1. [3] Photoelectric position sensor (1) according to claim 1, wherein the first index portion (50) and the second index portion (51) are juxtaposed in a transverse direction of the scale (2). [4] Photoelectric position sensor (1) according to claim 2, wherein the first index portion (50) and the second index portion (51) are juxtaposed in a transverse direction of the scale (2).

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