JP5381754B2 - Encoder - Google Patents

Description

  The present invention relates to an encoder that performs position detection.

In the encoder, a method is disclosed in which a pattern provided on a code plate is detected using a two-dimensional sensor in order to detect the position of a controlled object, and absolute position information is detected from the detected position information (for example, a patent). Reference 1).
In recent years, a control system to which an encoder is applied has shortened a response cycle (detection cycle) required for the encoder by shortening a control cycle of a higher-level control system to which a digital control method is applied.

Japanese Patent Laid-Open No. 5-18782

Incidentally, in recent years, as the use of encoders has expanded, it is desired to improve the positioning accuracy of the encoder and to increase the speed of calculation processing for position detection.
However, when increasing the positioning accuracy, it is necessary to refine the pattern (absolute pattern) for specifying the absolute position provided on the code plate, and the number of indexes included in the pattern necessary for determining the absolute position increases. To do. Then, as the number of indices for identifying a pattern increases, the order of encoding processing (for example, M-sequence code) for identifying an absolute position in the pattern also increases. Further, since the detection cycle is shortened, it is necessary to speed up the processing performed during one detection cycle. However, there is a problem that the power consumption increases when the processing speed is increased.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide an encoder that can save power in the process of detecting an absolute position.

  In order to solve the above-described problem, an aspect of the present invention is an Nth-order absolute pattern (N is a natural number) that is formed in the moving direction of the code plate, has a pattern width of the minimum identification width λ, and identifies an absolute position. And a detection unit that defines a range indicated by (N + 1) or more continuous patterns continuous in the moving direction in the absolute pattern as a first detection region, and is capable of detecting the first detection region. The detection unit is an encoder that detects a second detection region indicated by a selection pattern selected from the first detection region in accordance with the movement of the code plate.

  According to the present invention, it is possible to save power when detecting an absolute position.

It is a figure which shows the pattern shown by the code | symbol plate used for the encoder by one Embodiment of this invention. It is a block diagram which shows the structure of the encoder by one Embodiment of this invention. It is a side view which shows arrangement | positioning of the code | symbol board 10, the light source 20, and the sensor 30 by one Embodiment of this invention. It is a top view which shows the light-receiving surface 31 of the sensor 30 by one Embodiment of this invention. It is a figure which shows the detection of the pattern from the code | symbol plate by one Embodiment of this invention. It is a figure which shows the example of a pattern of the 9th M series pattern by one Embodiment of this invention. It is a figure which shows the example of a pattern of the 8th M series pattern by one Embodiment of this invention. It is a figure which shows the selection model in the case of the Nth order M series code | symbol by one Embodiment of this invention. It is a block diagram which shows the structure of the encoder by one Embodiment of this invention. It is a figure which shows the detection of the pattern shown by the code | symbol plate by one Embodiment of this invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 is a diagram showing a pattern shown on a code plate used in the encoder according to the present embodiment.
The code plate 10 shown in FIG. 1 includes both an absolute track including the pattern 11 and an incremental track including the pattern 12. The pattern 11 included in the absolute track is obtained by encoding position information indicating the positional relationship between the sensor 30 and the code plate 10 as an absolute position. Further, the pattern 12 included in the incremental track is obtained by arranging indexes of the same shape at equal intervals.
There are a transmission type and a reflection type for reading this pattern.
In the transmission type, light from a light source is irradiated from the back surface of the code plate, and a shadow of the pattern is created and read on the detection unit of the sensor. In the reflection type, light from the light source 20 is irradiated from the surface of the code plate 10, and reflected light from the code plate 10 is read by the sensor 30. Hereinafter, the reflection type will be described as an example.
The patterns 11 and 12 provided on each track of the code plate 10 are reflective patterns that reflect light emitted from the light source 20. The patterns 11 and 12 are subjected to surface treatment, for example, in a state having different reflectivities so that the amount of reflection differs according to information indicated by the patterns. In FIG. 1, a region having a low reflectance is indicated by a dark color, and a region having a high reflectance is indicated by white.
Hereinafter, a case where an M-sequence code is used for the absolute track pattern 11 will be described.

FIG. 2 is a block diagram showing the configuration of the encoder according to the present embodiment.
The encoder 1a shown in this figure includes a code plate 10, a light source 20, a sensor 30, a light source driving unit 40, a sensor driving unit 50, an amplification unit 60, a storage unit (memory) 70, and an arithmetic processing unit 90. The same components as those in FIG.

The light source 20 irradiates light necessary for detecting a pattern provided on the track of the code plate 10. The lighting state of the light source 20 is controlled according to a control signal supplied from the light source driving unit 40.
The sensor 30 detects a pattern provided on the track of the code plate 10.
Photodetecting elements (light receiving elements) arranged on a two-dimensional lattice are provided on the light receiving surface of the sensor 30.
The light receiving surface of the sensor 30 is disposed to face the surface of the code plate 10 on which the tracks are provided. Further, the sensor 30 is located at a position opposite to the position where the track of the code plate 10 is arranged, in a direction parallel to the tangential direction of the track provided on the code plate 10 or in a direction along the track. It is a two-dimensional image sensor provided with a plurality of light detection elements.
Each light detection element of the sensor 30 performs photoelectric conversion according to the amount of received light, and converts it into an analog signal indicated by a voltage corresponding to each light quantity. For example, a C-MOS (Complementary Metal Oxide Semiconductor) sensor can be applied to each photodetecting element. In the case of the C-MOS sensor, the light detection element includes a photodiode, a charge voltage conversion unit, a selector switch, and the like. Each light detection element of the sensor 30 is selected according to a control signal supplied from the sensor driving unit 50, and can detect the amount of light received from information output from the selected light detection element.

The light source driving unit 40 supplies a control signal for causing the light source 20 to emit light necessary for detecting a pattern provided on a track of the code plate 10.
The sensor driving unit 50 supplies the sensor 30 with a control signal and a timing signal for detecting the amount of light received by the photodetecting elements included in the selected region on the light receiving surface of the sensor 30 in accordance with an instruction from the arithmetic processing unit 90. .
The sensor driving unit 50 sequentially outputs a signal voltage corresponding to the electric charge accumulated according to the amount of received light to the light detection elements included in the range corresponding to the selected region.
The amplifying unit 60 amplifies a signal corresponding to the amount of received light detected by the light detection element in the sensor 30. The amplification unit 60 adjusts the amplification factor according to the signal level output from the sensor 30 so as to obtain an appropriate signal level.

The storage unit (memory) 70 stores operation mode designation information supplied from the outside, a reference value used for determination processing, setting information according to the state of the sensor 30, and the like in a variable area. The storage unit 70 is not limited to a semiconductor memory element, and may be a latch that stores a state.
The arithmetic processing unit 90 performs various settings in the encoder 1a, outputs a control instruction to each unit during operation, and generates and outputs position information detected based on the amount of light detected by the sensor 30. The arithmetic processing unit 90 includes an input / output unit 91, a light source control unit 92, a sensor control unit 93, a signal detection unit 94, and a position detection unit 95.
The input / output unit 91 receives setting information such as an initial value and a threshold value that determine the operation of the encoder 1 a according to setting information supplied from the outside, and records the setting information in the memory 70. Further, when an instruction to refer to a setting state or the like is supplied from the outside, the input / output unit 91 refers to and outputs corresponding information.
The light source control unit 92 supplies a control signal for controlling the light emission state of the light source 20 to the light source driving unit 40 based on an instruction from the input / output unit 91.
The sensor control unit 93 supplies a control signal that supports information to be output from the sensor 30 to the sensor driving unit 50 based on an instruction from the input / output unit 91.
The signal detection unit 94 is supplied with information based on the signal detected by the sensor 30 via the amplification unit 60. The signal detection unit 94 performs signal conversion processing on the information. Examples of signal conversion processing include filtering processing and analog-digital conversion processing.
The position detection unit 95 performs determination processing based on the result processed by the signal processing unit 94. As the determination process, there is a determination process for comparing with a predetermined reference value.

Next, with reference to the drawings, the arrangement of each component described above will be described.
FIG. 3 is a side view showing the arrangement of the code plate 10, the light source 20 and the sensor 30.
The code plate 10 shown in FIG. 3 is provided with a track provided with the patterns 11 and 12 shown in FIG. 2 on the lower surface. The light receiving surface 31 of the sensor 30 is arranged in a state parallel to and opposite to the surface on which the patterns 11 and 12 are arranged. The light source 20 is disposed on the light receiving surface 31 of the sensor 30 with the optical axis directed toward the code plate 10. Light emitted from the light source 20 is irradiated toward the code plate 10, and each reflected light through the patterns 11 and 12 of the code plate 10 is applied to the light receiving surface 31 of the sensor 30.

FIG. 4 is a top view showing the light receiving surface 31 of the sensor 30.
In FIG. 4, the change in the amount of light caused by the light irradiated onto the regions 32 and 33 where the light detection elements for detecting the reflected light from the patterns 11 and 12 are selected and the light receiving surface 31 is schematically shown. Show.
For example, light reflected by a portion having a low reflectance is absorbed by the patterns 11 and 12 provided on the code plate 10, and the amount of light irradiated on the light receiving surface 31 by the reflected light is reduced. In FIG. 4, a shadow indicated by a square area is formed in accordance with a pattern having a low reflectance.
The patterns 11 and 12 are parallel patterns on the code plate 10 by providing each pattern on the same circumference with different radii with the rotation axis of the code plate 10 as a reference. The light source 20 is disposed on the light receiving surface 31 that faces the gap formed between the pattern 11 and the pattern 12. The optical axis of the light source 20 is parallel to the rotation axis of the code plate 10 and is provided so as to pass through a gap formed between the pattern 11 and the pattern 12. That is, the light source 20 is provided at a position facing the gap between the pattern 11 and the pattern 12 provided in parallel. When the light source 20 is arranged at such a position, as shown in the figure, the shadow of the pattern 11 and the pattern 12 is projected on the light receiving surface 31 with the light source 20 interposed therebetween.

FIG. 5 is a diagram showing detection of a pattern from the code plate in the present embodiment.
FIG. 5A shows a range in which the sensor 30 detects the code plate 10 in which the pattern 11 and the pattern 12 are provided in parallel.
The code plate 10 has an N-order (N is a natural number) M-sequence pattern that can identify an absolute position with a minimum identification width λ (minimum reading unit) shown as a pattern 11 of 100 μm (micrometer), and a pattern. There is an incremental pattern of a repetitive pattern in which the basic pitch (1 pitch) shown as 12 is 100 μm. In the range shown in FIG. 5, a part of the pattern 11 and the pattern 12 is shown, and the pattern 11 and the pattern 12 are formed in the moving direction of the code plate 10.
When the absolute position is specified using the Nth order M-sequence pattern, the absolute position can be specified if (N + 1) continuous patterns continuous in the moving direction of the code plate 10 can be detected. That is, since the absolute position in the M-sequence pattern can be determined from the index provided continuously in the moving direction of the code plate 10, the pattern of the region (first detection region) indicated by the continuous pattern is continuously displayed. The range to be detected. The sensor 30 has a detection area capable of detecting (N + 1) continuous patterns at least simultaneously. Hereinafter, a case where the order of the M-sequence pattern shown in the pattern 11 is the ninth order (N = 9) will be described.

Although the code plate 10 of FIG. 5 is drawn linearly for the sake of drawing, it is a disc-shaped code plate 10 as an example for application to a rotary encoder. If the radius of the pattern formed on the code plate 10 is 19 mm (millimeters) and the maximum rotation speed v (maximum moving speed) is 6000 min ⁻¹ (per rotation), the maximum tangential speed on the circumference is 12 m. / s (meters per second).
On the other hand, if a request to refer to position information from a host system is repeatedly supplied with a cycle (cycle time) of 25 μs (microseconds), even if the rotation is at the maximum rotation speed, the connection at one cycle time is performed. The upper limit of the moving amount of the code plate 10 on the line is 300 μm.
That is, even if it rotates at the maximum rotation speed, the code plate 10 moves only by three pitches of the M-sequence pattern within the range of one cycle time corresponding to the detection interval t.
In order to detect the movement of the maximum three pitches, activating the entire sensor 30 (two-dimensional sensor) having a wider detection area is suitable for reducing power consumption and improving response speed. There will be no.

Furthermore, the amount of movement of the code plate 10 detected by the encoder 1a is 11938 mm (about 12 m) because it is 19 mm (radius) per second when the maximum rotational speed is 6000 min ⁻¹ . Since the encoder 1a detects the pattern of the code plate 10 every 25 μs, it is detected 40000 times per second. And the movement amount in the meantime is 0.298 mm.
The tangential acceleration (maximum acceleration) when the maximum rotational speed reaches 6000 min ⁻¹ after 100 ms from the stop state is (12 m / s−0 m / s) /0.1 ms = 120 m / s ² (meter per second per second). Therefore, at a detection interval of 25 μs, the maximum speed change is 120 m / s ² × 25 μs = 3 mm / s. The amount of movement at that time is (3 mm / s × 25 μs) /2=0.00004 mm. Even if the maximum acceleration is applied to the code plate 10 when the code plate 10 is moving at the maximum rotational speed of 6000 min ⁻¹ , the fluctuation amount in one section is 0.04 μm. Therefore, the fluctuation amount 0.04 μm in this one section is considered to be a negligible value. Here, assuming that a position detected at a certain mth time is DET (m) and a position at the next (m + 1) th time is DET (m + 1), when positions are detected at intervals of 25 μs, DET (m) and DET (m + 1) The difference is limited to 2 sections (0.466 mm).
In addition, the value of one movement difference is 298 μm. Thus, since the change for each time is very small, when the position detected at a certain mth time is indicated by DET (m) in the encoder 1a, the next (m + 1) th position DET (m + 1) is ( It can be limited to a position within a range indicated as (move of velocity calculated at m-th time) ± 300) μm.

From this, in the case of the 9th order M-sequence pattern, it is possible to specify the amount of movement of the code plate 10 that moves by the next time by detecting 11 consecutive M-sequence patterns.
In the present embodiment, 14 continuous patterns (continuous patterns) taking into account redundancy are projected onto the light receiving surface of the sensor 30. The sensor 30 detects four specific patterns (selected patterns) among the 14 patterns. Therefore, the sensor 30 detects a range (first detection region) indicated by 14 consecutive patterns. Further, the sensor 30 detects a range (second detection region) indicated by four specific patterns among the 14 patterns.
Further, the encoder 1a can estimate the position information det (m + 1) detected at the (m + 1) th time from the position information det (m) detected at a certain mth time.
Patterns detected as position information det (m) and det (m + 1) are shown as a matrix.

det (m) = (1 1 1 0 1 0 1 1 1 1 0 0 1 0)
det (m + 1) = (0 0 1 1 1 0 1 0 1 1 1 1 0 0)

  Comparing the two pieces of position information, it can be seen that the two positions are moved to the right by two patterns.

Next, extraction of a specific pattern from the 9th M-sequence pattern will be described with reference to the drawings.
FIG. 6 is a diagram illustrating a pattern example of the 9th order M-sequence pattern.
FIG. 6A is a diagram showing a state of a pattern (referred to as “original” pattern) detected at the current position of the code plate 10 and a pattern in which the “original” pattern can move by the next detection cycle. .
The detection of the code plate 10 is sampled by the sensor 30 at intervals at which adjacent patterns indicated by detection positions (1) to (14) can be detected.
The movable range from the position of the “original” pattern to the next detection cycle is three patterns in the moving direction of the code plate 10. Therefore, the range that can be moved from the position of the “original” pattern to the next detection cycle can be covered by the sensor 30 that can detect the range shown in the detection positions (1) to (14) at a time. The case of moving 1, 2, 3 patterns in the right direction from the position of the “original” pattern is shown as “right 1” and “right 2”, respectively. Further, the case of moving 1, 2, 3 patterns in the left direction is shown as “left 1” and “left 2”, respectively.

As shown in FIG. 6B, the encoder 1a does not have to compare all the patterns obtained from the 14 detection positions within the movement range of two patterns from the position of the “original” pattern. It is possible to calculate position information capable of identifying the movement position of That is, based on a specific pattern (selected pattern) extracted from the 14 patterns obtained from the output signal of the sensor 30, a detection position where the position information movement destination of the code plate 10 can be specified can be determined.
With reference to the current position in FIG. 6A, four patterns of detection positions (1), (5), (10), and (14) are extracted (selected). At this time, the “right 1” pattern when moved to the “right 1” position is detected by a combination of (0 1 0 1). Similarly, the patterns of “Right 2”, “Original”, “Left 1”, “Left 2” are similarly expressed as (0 1 0 0), (1 0 0 1), (0 1 1 0), (1 1 0 1).
Thus, it can be seen that the current position and the four estimated movement positions can be identified at a small number (for example, four) of detection positions.
The selection of which detection position to extract from the 14 detection positions differs depending on the current position pattern (“original” pattern), but can be uniquely specified according to each detection position. Further, as described above, the information for specifying the detection position is stored in advance in the memory 70 as a table for each pattern of the current position, and the table is used when the position detection unit 95 performs position determination in the detection cycle. The detection position may be selected based on the above.
In addition, you may control the operation | movement of the sensor control part 93 and the signal processing part 94 based on the information which specifies the detection position obtained by the position detection part 95 referring the table.
For example, the position detection unit 95 can limit the range in which the sensor 30 is activated with respect to the sensor control unit 93. The sensor control unit 93 changes the control signal and the timing signal for the sensor 30 so as to detect the information of the light detection elements in the range designated by the position detection unit 95.
Further, the position detection unit 95 can cause the signal processing unit 94 to acquire necessary information by limiting the signals to be detected. The signal processing unit 94 changes the detection timing based on the detection signal supplied from the sensor 30 so as to detect the information of the light detection elements in the range instructed by the position detection unit 95, and obtains effective information. Information is acquired at the timing of detection.
With the above processing, the amount of information to be collected can be greatly reduced, and the calculation processing of the position detection unit 95 that performs position detection from the collected information can also be reduced.

(Second Embodiment)
Next, extraction of a specific pattern in the 8th order M-sequence pattern will be described with reference to the drawings.
FIG. 7 is a diagram illustrating a pattern of an 8th order M-sequence pattern.
FIG. 7A is a diagram showing a state of a pattern (referred to as “original” pattern) detected at the current position of the code plate 10 and a pattern in which the “original” pattern can move by the next detection cycle. is there.
Detection of the code plate 10 is sampled by the sensor 30 at intervals at which adjacent patterns indicated by detection positions (1) to (11) can be detected.
Assuming that the radius of the pattern formed on the code plate 10 is the same as that of the first embodiment, one pitch of the M-sequence pattern is 0.466 mm, and the amount of tangential movement when the maximum speed is changed is 0.298 mm as in the first embodiment. Therefore, the moving amount of the code plate 10 is 1 pitch. The movable range from the position of the “original” pattern to the next detection cycle is one pattern at a time in the moving direction of the code plate 10. Therefore, the range that can be moved from the position of the “original” pattern to the next detection cycle can be covered by the sensor 30 that can detect the ranges shown in the detection positions (1) to (11) at a time. A case where 1, 2, 3 patterns are moved in the right direction from the position of the “original” pattern is indicated as “right 1”. A case where one pattern is moved in the left direction is indicated as “left 1”.

FIG. 7B shows the movement position of the code plate 10 without comparing all the patterns obtained from the 13 detection positions including redundancy within the movement range of one pattern from the position of the “original” pattern. Can be calculated. That is, based on a specific pattern (selected pattern) extracted from the 13 patterns obtained from the output signal of the sensor 30, a detection position where the position information of the code plate 10 can be specified can be determined. Accordingly, the sensor 30 detects a range (first detection region) indicated by the 13 consecutive patterns. In addition, the sensor 30 detects a range (second detection region) indicated by four specific patterns among the 13 patterns.
With reference to the current position in FIG. 7A, four detection positions (1), (5), (9), and (11) are extracted (selected). At this time, the “right 1” pattern when moved to the “right 1” position is detected by a combination of (1 1 0 1). Similarly, the “original” and “left 1” patterns are (1 1 1 1) and (0 1 1 0).
Thus, it can be seen that the current position and the two estimated movement positions can be identified by a small number (for example, four) of detection positions.

(Third embodiment)
Next, referring to the drawing, it will be shown how to reduce the amount of calculation when transitioning from the initialization state to the operation state.
FIG. 8 shows a selection model in the case of an Nth order M-sequence code.
(Processing in initialization mode) Since the encoder 1 has not been able to specify the position of the code plate 10 in the initialization state, that is, when the power is turned on, the pattern 11 is detected by detecting (N + 1) or more patterns in the detection cycle. Detection is performed using the sensor 30 every t seconds. The detection positions in this case are (N + 1) or more consecutive patterns (continuous patterns) necessary for identification.
(Processing in Power Saving Mode) The encoder 1 can reduce the number of detection patterns after power-on to i. The number i is derived by the following relationship determined by the maximum moving speed v, the detection cycle period (detection interval) t, and the minimum pattern identification width λ.
i is a minimum integer satisfying ((integer part of (v × t / λ)) + 1) × 2 <2 ⁱ .
Therefore, the number of patterns (selected patterns) to be extracted can be determined as i or more and less than N patterns.

  Hereinafter, an example will be described. For example, the case of an 8th order M-sequence code pattern (N = 8) is shown. The required specifications of the encoder 1 are as follows.

Travel speed: Maximum speed 6000 min ^-1 (per rotation), (= 100 s ^-1 (per rotation)),
Wavelength: λ = 360 degrees / 256,
Angular velocity: v = 36000 degrees / s (degrees per second),
Detection interval: 100 μs
The value of (v × t / λ) at this time is derived from the following equation.

v × t / λ = 36000 ÷ (1000000 × 360/256) = 0.025

That is, from the above result, the minimum integer i satisfying (2 <2 ⁱ ) is 2.
Even if rotating at the maximum speed, if the detection cycle is every 100 μs, it moves only by one pitch with respect to the current position.
Therefore, as shown in FIG. 8, the next to the eighth-order number sequence specifying the detection location can be represented by a combination of “0” or “1”, and there are four types of combinations. In the drawing, the description of the eighth-order number sequence portion is omitted.

If only the patterns at both ends are detected, the position detection unit 95 detects if the condition is determined to have moved to the right if (0, 1) and moved to the left if (1,0). However, if a combination of “0” at both ends (0,0) and a combination of “1” and (1,1) is detected, it cannot be determined whether it is right or left.
However, since it is encoded with an 8th order M-sequence code, it does not become “1” (or “0”) in succession, so in the 8 number sequences, “1” ”And“ 0 ”each exist at least one or more.
Therefore, if both ends are “0” s or “1s”, it is determined whether it is a part that becomes “1” or a part that becomes “0” in the 8 number sequence parts, and is passed to the second detection part. That's fine.

(Fourth embodiment)
FIG. 9 is a block diagram showing the configuration of the encoder according to the present embodiment.
The encoder 1b shown in FIG. 9 includes a code plate 10, a light source 20, a sensor 30, a light source driving unit 40, a sensor driving unit 50, an amplification unit 60, a storage unit (memory) 70B, and an arithmetic processing unit 90B. The same components as those in FIGS.
In addition to the configuration shown in the storage unit (memory) 70 in FIG. 1, the storage unit (memory) 70 </ b> B stores information for determining a reference area among the light detection elements included in the sensor 30. The area to be referred to can be determined in units of a plurality of rows in which the light detection elements are arranged in the moving direction of the code plate.

The arithmetic processing unit 90B includes an input / output unit 91, a light source control unit 92, a sensor control unit 93, a signal detection unit 94B, a position detection unit 95B, and a determination unit 96.
The signal detection unit 94B in the arithmetic processing unit 90B detects the signals of the plurality of light detection element arrays supplied from the amplification unit 60 based on the information of the plurality of light detection element arrays detected by the sensor 30.
The position detection unit 95B refers to the storage unit (memory) 70B based on the previously detected information on the current position, and acquires information for determining a reference region among the light detection elements included in the sensor 30. The position detection unit 95B selects a plurality of columns arranged in the moving direction of the code plate 10 based on the information defining the acquired area, and detects the light detection elements included in the plurality of columns by the light source driving unit 50. To direct.
The position detection unit 95B performs determination processing on the information of the plurality of light detection element arrays detected by the signal detection unit 94B by the determination unit 96, and detects the rotation angle position of the code plate 10 based on the determination result. Do.
The determination unit 96 performs majority operation processing based on the result of determining the information of the plurality of light detection element arrays detected by the sensor 30.

FIG. 10 is a diagram showing detection of the pattern shown on the code plate 10 according to the present embodiment.
The code plate 10 shown in FIG. 10A has the same configuration as that shown in FIG.
A range in which the code plate 10 is detected by the sensor 30 is indicated by a detection range DET.
In this figure, the absolute track area including the pattern 11 is divided into a plurality of detection areas. Here, the number of divisions of the region is 3 or more. In this figure, three areas of division detection areas DETa, DETb, and DETc are shown.

FIG. 10B shows information to be detected when the detection area DET is detected.
However, in each divided detection area, a case is assumed in which erroneous detection occurs for some reason in detection of a pattern in a partial area. Here, it is assumed that the fourth pattern from the left of the division detection area DETb is a pattern that has been erroneously detected, and “0” is detected where it should be determined as “1”. Accordingly, the result of the division detection areas DETa and DETc in which the positions of the same pattern are detected is correctly determined as “1”.

FIG. 10C shows the majority operation processing.
Therefore, when there is a difference between the detection results in the respective divided detection areas, the code determination unit 94 determines the determination value that is frequently determined as the true determination value of the pattern. As a result, majority calculation processing can be performed based on the detected result, so that even if erroneous detection occurs in one division detection region, erroneous detection is performed if another region is correctly determined. Except for this, the correct violation result can be output.

  Further, in addition to the above-described majority calculation processing, the (m + 1) th accurate position can be determined using the predetermined six movement position patterns as described above. Since the encoder according to the present embodiment can reduce calculation processing such as the number of comparisons necessary for estimation, rather than detecting all 14 patterns, the position of the next time can be determined in a short time. Further, the encoder according to the present embodiment can reduce power consumption by limiting the detection range of the sensor 30.

The encoder according to the present embodiment is formed in the moving direction of the code plate, has a pattern width of the minimum identification width λ, and identifies the absolute position of the N-th absolute pattern (N is a natural number) and the absolute pattern among the absolute patterns. A range indicated by (N + 1) or more continuous patterns continuous in the movement direction is defined as a first detection region, and a detection unit capable of detecting the first detection region is provided, and the detection unit includes the code Detecting a second detection region indicated by a selection pattern selected from the first detection region in response to movement of the plate.
As a result, the encoder can save power when detecting the absolute position.
The present invention is not limited to the above embodiments, and can be modified without departing from the spirit of the present invention.

1a, 1b Encoder 10 Code plate 11 Pattern (absolute pattern)
12 patterns (incremental patterns)
30 sensors

Claims (10)

An Nth-order absolute pattern (N is a natural number), which is formed in the moving direction of the code plate, has a pattern width of the minimum identification width λ, and identifies an absolute position;
A range indicated by (N + 1) or more continuous patterns continuous in the movement direction in the absolute pattern is defined as a first detection region, and includes a detection unit capable of detecting the first detection region,
The encoder detects the second detection area indicated by the selection pattern selected from the first detection area according to the movement of the code plate. The encoder according to claim 1, wherein
An encoder comprising: an arithmetic processing unit that determines the second detection region based on at least one of a variable among a maximum moving speed of the code plate, a detection interval, and the minimum identification width λ. . The encoder according to claim 1 or 2,
An encoder comprising: an arithmetic processing unit that determines the second detection area based on a result obtained by dividing a product of a maximum moving speed v of the code plate and a detection interval t by the minimum identification width λ. The encoder according to any one of claims 1 to 3,
The detection of the first detection area by the detection unit is as follows:
An encoder characterized by repeatedly detecting a predetermined number of times in accordance with an initialization operation for initializing the absolute position to be held. The encoder according to any one of claims 1 to 4,
The detection of the second detection area by the detection unit is as follows.
The encoder is characterized in that it is performed in a steady operation state after the initialization operation for initializing the absolute position is completed. The encoder according to any one of claims 3 to 5,
The detector is
detecting i or more and less than N selected patterns,
I is
(Integer part of v × t / λ + 1) × 2 <2 ⁱ
An encoder characterized by being the smallest integer that satisfies the relational expression shown below. The encoder according to any one of claims 1 to 6,
The encoder comprising: a two-dimensional image sensor capable of detecting a two-dimensional detection region. The encoder according to any one of claims 1 to 7,
A storage unit that stores selection information that defines a range of the second detection region in association with prediction pattern information that can be detected in the first detection region;
The detector is
An encoder, wherein a range of the second detection area is selected with reference to the selection information based on the continuous pattern detected in the first detection area. The encoder according to claim 7 or claim 8,
An encoder comprising: a selection unit that selects whether or not the pixel is required for detection of the selection pattern based on a light reception image from the detection unit. The encoder according to any one of claims 7 to 9,
The two-dimensional image sensor has a light receiving area capable of receiving the first detection areas in three or more rows along the moving direction of the code plate,
An encoder comprising: a determination unit configured to determine the position information of the code plate by a majority vote based on a result detected in each of the light receiving regions.

Images