KR101377687B1 - Optical encoder mixed incremental type and absolute type - Google Patents

Abstract

An optical encoder according to the present invention includes: a first random code grid for partially transmitting a light incident by repeatedly forming a grating corresponding to a random code pattern according to a random code on a path for displacement detection; A first repeating pattern lattice formed of a lattice according to a first repeating pattern on a path for the displacement detection, the first repeating pattern lattice being a perforated lattice to partially transmit incident light; Light source; A second random code grid formed with a grid corresponding to a random code pattern according to the random code and receiving light from the light source and partially transferring the light from the light source to the first random code grid; A second repeating pattern lattice formed of a lattice according to a second repeating pattern, the second repeating pattern lattice being an object lattice which receives light from the light source and partially transmits the light to the first repeating pattern lattice; A third repeating pattern lattice formed of a lattice according to a third repeating pattern and being an object lattice that receives light from the light source and partially transmits the light to the first repeating pattern lattice; A first photodetector arranged to correspond to a random code pattern according to the random code, the first photodetector configured to receive light transmitted by the second random code grid and the first random code grid to generate an absolute displacement detection signal; A second photodetector, in which photodetectors are arranged to correspond to a fourth repeating pattern, the second photodetecting unit receiving light transmitted by the second repeating pattern grid and the first repeating pattern grid to generate a first type of incremental signal; A third photodetector, in which photodetectors are arranged to correspond to a fifth repeating pattern, the third photodetecting unit receiving light transmitted by the third repeating pattern grid and the first repeating pattern grid to generate a second type of incremental signal; And a signal processor for processing the absolute displacement detection signal and the first and second type incremental signals to generate displacement information.

Description

Optical encoder mixed incremental type and absolute type}

The present invention relates to an optical encoder, and more particularly, to an optical encoder in which an incremental method and an absolute value method are mixed.

In order to measure the displacement information of an object with high accuracy, various types of optical encoders are widely used in the field of industrial measuring machines and the like.

The optical encoder may be classified into a rotary encoder or a linear encoder in a form, and may be classified into an incremental encoder and an absolute encoder as a signal processing method. Can be.

The configuration and operation of the 3-grating optical encoder among the above-described optical encoders will be described.

The three-grating optical encoder is composed of a scale which is a fixed grating (Pupil grating) fixed to the base and a head portion fixed to the mover and moving relative to the scale.

The head part includes a light emitting part, a signal processing part, a grating part, and an optical sensor part. In particular, the grating part includes an object grating and an image grating, and the gratings have a periodic pattern structure. Have

Light from the light emitting part is transmitted to the perforated grating through the object grating, the perforated grating transmits or reflects the transmitted light to the image grating, and the image grating is light transmitted by the perforated grating. It passes through and passes to the optical sensor unit.

The amount of light that is incident on the light sensor changes according to the change in the degree of coincidence between the perforated grating and the object grating. This change in the amount of light has the characteristics of a sinusoidal signal at a certain distance condition.

Accordingly, the optical encoder acquires relative displacement information between the scale fixed to the base and the head part fixed to the mover and moving relative to each other by using the characteristic.

In particular, since the light transmitted through the object grating forms a high-contrast moiré image at a specific position, the optical encoder determines the distance between the gratings and the position of the light sensor so that an optical signal can be obtained at the highest contrast. .

In addition, the optical encoder is also provided with an origin detection device for generating reference information for the relative displacement information.

The origin detection apparatus is formed in such a way that the maximum amount of light can be transmitted only when the origin detection patterns respectively installed on the base and the header coincide with each other. The pattern may be a plurality of simple square patterns or any random grid pattern.

In the case of employing a laser (Light Amplification by Stimulated Emission of Radiation) device as a light source of the optical encoder as described above, the position where the contrast of the light is increased is Z = Np ² / λ (Z is the relative motion object and Where N is an integer, p is the period of the diffraction grating, λ is the wavelength of the light), but when the light emitting diode (LED) is employed as the light source of the optical encoder, the position where the contrast of the light is strong is Z = (1/5) p ² / λ (p is the period of the diffraction grating, λ is the wavelength of the light).

In the case of employing such an LED as a light source, in order to obtain a dense output signal, the smaller the P (periodic grating period), the smaller the distance condition for obtaining high optical contrast, so that P is proportional to the square. In addition to configuring a system including a light emitting part and a light receiving part in a gap, there is a problem of maintaining and aligning the narrow gap.

Accordingly, even in the case of employing LED as a light source of the optical encoder, it is required to develop a technology that can design the optical system of the optical encoder to increase the accuracy and reliability of high-contrast optical modulation signal-based displacement information and origin information.

It is an object of the present invention to provide an optical encoder in which an incremental method and an absolute value method are mixed to accurately detect displacement information of an object even when an element generating an incoherent light is used as a light source of the optical encoder. It is done.

The optical encoder according to the present invention for achieving the above object, the first random code to partially transmit the incident light by forming a grating corresponding to the random code pattern according to the random code repeatedly on the path for displacement detection grid; A first repeating pattern lattice formed of a lattice according to a first repeating pattern on a path for the displacement detection, the first repeating pattern lattice being a perforated lattice partially transmitting incident light; Light source; A second random code grid formed with a grid corresponding to a random code pattern according to the random code and receiving light from the light source and partially transferring the light from the light source to the first random code grid; A second repeating pattern lattice formed of a lattice according to a second repeating pattern, the second repeating pattern lattice being an object lattice which receives light from the light source and partially transmits the light to the first repeating pattern lattice; A third repeating pattern lattice formed of a lattice according to a third repeating pattern and being an object lattice that receives light from the light source and partially transmits the light to the first repeating pattern lattice; A first photodetector arranged to correspond to a random code pattern according to the random code, the first photodetector configured to receive light transmitted by the second random code grid and the first random code grid to generate an absolute displacement detection signal; A second photodetector, in which photodetectors are arranged to correspond to a fourth repeating pattern, the second photodetecting unit receiving light transmitted by the second repeating pattern grid and the first repeating pattern grid to generate a first type of incremental signal; A third photodetector, in which photodetectors are arranged to correspond to a fifth repeating pattern, the third photodetecting unit receiving light transmitted by the third repeating pattern grid and the first repeating pattern grid to generate a second type of incremental signal; And a signal processor for processing the absolute displacement detection signal and the first and second type incremental signals to generate displacement information.

The present invention described above causes an effect of accurately detecting displacement information of an object even when an element generating incoherent light is used as a light source of the optical encoder.

1 is a block diagram of an optical encoder according to a preferred embodiment of the present invention.
2 illustrates a photodetection signal of an optical encoder in accordance with a preferred embodiment of the present invention.
3 and 4 illustrate the structure of a second or third photodetector according to a preferred embodiment of the present invention.
5 schematically shows an optical system according to a preferred embodiment of the present invention.
6 illustrates the structure of a transmission optical system according to a preferred embodiment of the present invention.
7 illustrates an OTF graph for optical system determination according to a preferred embodiment of the present invention.
8 is a diagram illustrating a structure of the first to fourth photodetectors according to a preferred embodiment of the present invention.
9 illustrates a structure of a reflective optical system according to a preferred embodiment of the present invention.
10 is a block diagram of a signal processing unit according to a preferred embodiment of the present invention.

The present invention can accurately detect displacement information of an object even when an element that generates incoherent light is used as a light source of the optical encoder.

<Optical Encoder Structure>

The structure of an optical encoder according to a preferred embodiment of the present invention will be described with reference to FIG.

The optical encoder includes a control device 100, an LED module driver 102, an LED module 104, an optical system 106, first to fourth light detectors 108 to 114, and a signal processor 116.

The control device 100 controls the respective parts of the optical encoder as a whole, and in particular, the LED module 104 is driven through the LED module driver 102. In addition, the control device 100 receives the displacement information from the signal processor 116 to recognize the displacement with respect to the object. The displacement information includes absolute displacement detection information, relative displacement detection information, and turn detection information .

The LED module driver 102 drives the LED module 104 under the control of the control device 100.

The LED module 104 emits incoherent light under the control of the LED module driver 102. The light emitted from the LED module 104 is incident to the optical system 106.

The optical system 106 includes a number of configurations for light transmission, with some configurations located in the object and the other configurations located in a housing that moves relative to the object. The optical system 106 transmits the light emitted from the LED module 104 to the first to fourth photodetectors 108 to 114 according to the relative movement between the object and the housing, and the amount of light transmitted therethrough. To change.

Each of the first to fourth photodetectors 108 to 114 receives the light transmitted by the optical system 106, and accordingly, the first and second photodetectors 108 to 114 receive the incremental signals of the first and second types, the absolute displacement detection signal, and the turn detection signal. Output The first and second types of incremental signals, absolute displacement detection signals, and turn detection signals are provided to the signal processor 116.

The signal processor 116 receives and processes the first and second types of incremental signals, absolute displacement detection signals, and turn detection signals to generate relative displacement detection information, absolute displacement detection information, and turn detection information. To generate displacement information.

<First light detector 108>

In more detail, the first photodetector 108 may include a plurality of photodetectors corresponding to each bit of a predetermined random code pattern in an absolute displacement detection region through which light is transmitted by the optical system 106. will be. The random code is a random code generated using a linear feedback shift register (LFSR).

In more detail, the absolute encoder according to the present invention is an independent photodetector device corresponding to the number of bits if the LFSR random pattern is composed of (2 ^N -1) bit combinations to detect the LFSR random pattern. And the output of each of the photodetectors is set to 0 or 1 depending on the amount of incident light. Thereafter, a point corresponding to the LFSR random pattern is detected through the output of the photodetectors to detect MSB (Most Significant Bit) data as shown in FIG. The signal processor 116 performs signal processing on the MSB data to generate LSB (Least Significant Bit) data as shown in FIGS. 2B through 2D.

As described above, the signal processing unit 116 stores the MSB data as shown in FIG. 2A and (B) to FIG. 2D from the absolute displacement detection signal of the first photodetector 108. LSB data as shown are generated, and the MSB data and LSB data become absolute displacement detection information.

<2nd light detector 110 and third light detector 112>

The second photodetector 110 and the third photodetector 112 receive the light transmitted through the repeating pattern grating provided in the optical system 106, and accordingly increase the first and second type incremental signals. Create and print

In particular, the second photodetector 110 corresponds to an image repetition pattern in which a slit pitch is determined to correspond to the case where N represents 1, the order in which a moire pattern is formed in an OTF equation according to an optical transfer function (OTF). Are arranged, and the light transmitted through the object repeating pattern lattice and the repeating repeating lattice of the optical system 106 whose slit pitch is determined to correspond to the case where N representing the order of forming the moire pattern in the OTF equation is 1 is received. And generate an increase type signal of the first type accordingly.

The third photodetector 112 includes photodetectors arranged to correspond to an image repetition pattern in which a slit pitch is determined to correspond to the case where N representing the order of forming the moire pattern in the OTF equation according to the OTF is 2, In the OTF equation according to the OTF, the light transmitted through the object repeating pattern lattice and the pupil repeating pattern lattice whose slit pitch is determined to correspond to the case where N representing the order of forming the moire pattern is 2 is received. Produces an incremental signal of. The period of the incremental signal of the second type is 1/2 with respect to the period of the incremental signal of the first type.

The second photodetector 110 and the third photodetector 112 stably generate the incremental signals of the first and second types, and increase the arrangement interval of the photodetector elements, thereby facilitating manufacturing. It can be configured in one of two forms to do so.

<1st form of the 2nd light-detection part 110 or the 3rd light-detection part 112>

First, a first form of the second or third light detectors 110 and 112 will be described in detail with reference to FIG. 3.

In addition to arranging two photodetector PDs in one OTF imaging cycle, nine OTF imaging cycles are determined as one photodetector PD array placement cycle, and the first to sixth OTF imaging cycles are determined in the first to third OTF imaging cycles. The photodetecting elements PD for the incremental signals A, B, A /, B / of the fourth phase are evenly arranged.

As such, by arranging two photodetectors PD in one OTF imaging cycle, a dead section of sufficient size is secured to ensure stability of the photodetection signal and to facilitate manufacturing.

In addition, the photodetecting elements PD of the first to fourth phases are dispersed and arranged within nine OTF imaging cycles, thereby increasing the reliability of the photodetecting signal. That is, as shown in FIG. 3, the photodetecting device PD of the first phase A, the photodetecting device PD of the third phase A /, and the photodetecting device PD of the first phase A are illustrated. ), The photodetecting device PD of the third phase (A /), the PD of the second phase (B), the photodetecting device PD of the fourth phase (B /), and the photodetection of the second phase (B). Element PD, photodetection element PD of the fourth phase B /, photodetection element PD of the first phase A, photodetection element PD of the third phase A /, The photodetecting element PD of one phase A, the photodetecting element PD of the third phase A /, the photodetecting element PD of the second phase B, and the fourth phase B / The photodetecting device PD, the photodetecting device PD of the second phase B, and the photodetecting device PD of the fourth phase B / may be arranged.

The above batch standard is expressed by Equation 1 below.

In Equation 1, P _{PD_array} is a period of a periodic photodetector element (PD) array, P ₂ is an imaging period according to the OTF, S _{ph_each} is the size of each phase, S _{dead_section} is the size of the dead section.

<2nd form of the 2nd light-detection part 110 or the 3rd light-detection part 112>

4, the second form of the second light detector 110 or the third light detector 112 will be described in detail.

The second type of the second photodetector 110 or the third photodetector 112 is to generate an incremental signal of the first to fourth phases adaptively to light incident differently according to the period of the OTF.

That is, after arranging the first to eighth light detecting elements A, B, C, D, E, F, G, and H twice in order, the first and fifth may be considered in consideration of the case where the period of the OTF is one. A first output terminal connecting the photodetectors A and E, a second output terminal connecting the second and sixth photodetectors B and F, and a third and seventh photodetector Considering a case in which a third output terminal connecting C and G and a fourth output terminal connecting the fourth and eighth light detecting elements D and H are connected, and the period of the OTF is 2, A fifth output terminal connecting the first and second photodetection elements A and B, a sixth output terminal connecting the third and fourth photodetection elements C and D, and the fifth and fifth output terminals. And a seventh output terminal connecting the six light detecting elements E and F, and an eighth output terminal connecting the seventh and eighth light detecting elements G and H.

As described above, the present invention is provided with output terminals connecting photodetecting elements corresponding to the period of the OTF, so that the second photodetector 110 and the third photodetector 112 can be used even if only one type of photodetector is manufactured. To be.

The signal processor 116 receives the incremental signals A, B, A /, and B of the first to fourth phases provided from the second photodetector 110 as peak type incremental signals. And detect the first relative displacement detection information according to the detected peak, and provide it to the control device 100.

In addition, the signal processor 116 receives the incremental signals A, B, A /, and B of the first to fourth phases provided from the third photodetector 112 as the second incremental signals. The peak is detected, second relative displacement detection information is generated according to the detected peak, and the control unit 100 is provided to the control unit 100.

<4th light detector 114>

The fourth light detector 114 receives the light transmitted through the windows for turn detection provided in the optical system 106, generates a turn detection signal according to the signal, and provides the signal to the signal processor 116. The signal processor 116 detects a peak of the turn detection signal, generates turn detection information according to the detected peak, and provides the same to the control device 100.

<Optical System 106>

In the optical system 106 according to the preferred embodiment of the present invention, the path for the displacement detection may be a straight line or a circumference. In the following description, only the example of generating the displacement information on the circumference or more will be described.

5 schematically shows an optical system 106 according to a preferred embodiment of the present invention.

The optical system 106 may be divided into first and second plates 208 and 210 and a disc-shaped disc 200 which are largely connected to the housing of the device.

At the circumferential edge of the disc-shaped disc 200, a first random code grid 202 for partially transmitting light incident through a grid corresponding to a random code pattern according to a random code is formed, and the first random code grid ( Inside the 202, a first repeating pattern grid 204 for partially transmitting light incident through a grating corresponding to the repeating pattern is formed, and a part of the inside of the first repeating pattern grid 204 is turned off. A first window 206 is formed. In particular, the first random code grid 202 is formed by repeating a long random code pattern along the circumference, the random code pattern is based on a random code generated using the LFSR.

The first plate 208 and the second plate 210 are located on the upper and lower surfaces with the circumferential edge of the disk 200 when the optical system is a transmission type, and the disk 200 when the optical system is a reflection type. It is located on the upper or lower surface of.

Thus, the structure of the first plate 208 and the second plate 210 will be described by dividing the transmission type and the reflection type.

<Transmissive optical system>

First, the structure of the transmission optical system will be described with reference to FIG. 6.

Light from the LED module 104 is provided to the first collimated lens unit 300.

The first collimated lens unit 300 collimates and emits light from the LED module 104.

The light collimated by the first collimated lens unit 300 includes the second random code grid 302, the second repeated pattern grid 304, and the third repeated pattern grid 306 provided in the first plate 208. ) And a second window 308.

The second random code grid 302 partially transmits the light incident through the grating corresponding to the random code pattern according to the random code, which is transmitted to the first random code grid 202 of the disc-shaped disc 200. do. The random code pattern is based on a random code generated using LFSR.

The second repetitive pattern grid 304 is a repetitive pattern grid in which the slit pitch is determined to correspond to the case where N, which represents the order in which the Moire pattern is formed in the OTF equation according to the OTF, is an object lattice, and repeats incident light. The transmission is partially transmitted according to the pattern grid, which is transmitted to the first repeating pattern grid 204 of the disc-shaped disc 200.

The third repetitive pattern grid 306 is a repetitive pattern grid in which the slit pitch is determined to correspond to the case where N, which represents the order in which the moire pattern is formed in the OTF equation according to the OTF, is an object lattice, and repeats incident light. The transmission is partially transmitted according to the pattern grid, which is transmitted to the first repeating pattern grid 204 of the disc-shaped disc 200.

The second window 308 transmits incident light to the first window 206 of the disc-shaped disc 200.

The first plate 208 on which the second random code grid 302, the second repeating pattern grid 304, the third repeating pattern grid 306, and the second window 308 are formed has a predetermined first distance. It is installed spaced apart from the disk-shaped disk (200). The first distance is set to a distance to which both N and 1, which represent the order in which the moire pattern is formed in the OTF equation according to the OTF, are applicable.

The first random code grid 202, the first repeating pattern grid 204, and the first window 206 formed on the disc-shaped disc 200 transmit the incident light. In particular, the first repeating pattern grid 204 is a perforated lattice.

First to fourth photodetectors 108, 110, 112, and 114 are provided on the second plate 210 spaced apart from the disc-shaped disc 200 by a predetermined second distance. The second distance is set to a distance to which both N and 1, which represent the order in which the moire pattern is formed in the OTF equation according to the OTF, are applicable.

The first photodetector 108 includes photodetectors arranged to correspond to a random code pattern according to the random code, thereby generating an absolute displacement detection signal.

In order to simultaneously perform the role of the image grating and the photodetecting device, the second photodetector 110 has a slit pitch corresponding to the case where N represents 1, the order in which the moire pattern is formed in the OTF equation according to the OTF. It is composed of photodetectors arranged to correspond to the determined repeating pattern, and receives the light transmitted through the second repeating pattern grid 304 and the first repeating pattern grid 204 to generate a first type of incremental signal. .

In order to simultaneously perform the role of the image grating and the photodetecting device, the third photodetector 112 has a slit pitch corresponding to the case where N is 2, which represents the order in which the moire pattern is formed in the OTF equation according to the OTF. The photodetector is arranged to correspond to the determined repeating pattern, and receives the light transmitted through the third repeating pattern grid 306 and the first repeating pattern grid 204 to generate a second type of incremental signal. .

The fourth light detector 114 receives the light transmitted through the first and second windows 308 and 206 to generate a turn detection signal.

The transmission optical system transmits light to the first light detector 108 using the first and second random code grids 202 and 302 to generate absolute displacement information whenever the random code pattern is repeated.

In addition, the above-described transmission optical system uses an image of the first and second repetitive pattern grids 204 and 304, which are perceptual gratings and object gratings whose slit pitches are determined to correspond to the case where N is 1, in order to generate an incremental signal of the first type. To transmit light to the second photodetector 110 in which the photodetectors are arranged in the form of a grating, and to generate a second type incremental signal whose period is 1/2 for the first type of incremental signal. By using the first and third repeating pattern grids 204 and 306 which are the lattice of the slit pitch and the object lattice corresponding to the case where N is 2, the photodetectors 112 are arranged in the form of an image lattice. The first and second distances, which transmit light, and are the distance between the first plate 208 and the second plate 210 with respect to the disc-shaped disc 200, indicate the order in which the moire pattern is formed in the OTF equation according to the OTF. Both cases where N is 1 and 2 apply The distance that can be determined is determined.

In addition, the transmission optical system transmits light to the fourth photodetector 114 through the first to second windows 206 and 308 for turn detection.

Here, the process of determining the slit pitch and the first and second distances of the repeating pattern grids will be described in more detail. In the following description, the first distance is referred to as the object distance Z1 and the second distance is referred to as the image distance Z2.

The OTF equation OTF (F) of the optical system may be given as a term of autocorrelation of a general pupil function.

In Equation 2, λ is the wavelength of incident light, σ ₂ is the spatial frequency of the Fourier image, k is (2π) / λ, a is (1 / Z ₂ + 1 / Z ₂ ) / 2, and Z2 is The distance between the pupil grid and the image grid. Here, the perforated lattice is the first repeating pattern grid 204 formed in the disc-shaped disk 200. The image grating becomes a repeating pattern of the second and second photodetectors formed on the second plate 210.

The perfill transfer function P (X) by the perfill lattice is represented by Equation 3 below.

In Equation 3, P is the slit pitch of the perforated lattice, 2ε is the width of each slit, and n is an integer.

After substituting Equation 3 into Equation 2, assuming that the number of slits in the perforated lattice is infinitely large, Equation 4 is obtained.

In Equation 4, m is an integer, and 2ε is less than or equal to p / 2.

Equation 4 is solved after assuming that sigma ₂ is greater than or equal to mp / λZ _{2 and} less than (mp / λZ 2) + (2ε / λZ ₂ ).

The modified OTF equation based on the object distance Z1 between the perforated lattice and the object lattice generated according to the above-described equation is given by Equation 6. The object grating is any one of the second and third repeating pattern grids 304 and 306 formed on the first plate 208.

 The OTF equation based on the image distance Z2 between the perforated lattice and the image lattice generated by solving the above equation is represented by Equation 7.

Using the OTF equation based on the object distance Z1 and the image distance Z2 as described above, the slit pitches of the image grating and the object grating can be obtained assuming that the ratio of the object distance Z1 and the image distance Z2 is determined .

이며, 여기서 상기 N은 정수이다. 그리고 시스템 배율(system magnification)은

이라 할 수 있다. In other words, the imaging condition is

Where N is an integer. And system magnification

This can be called.

로 주어지고, 이미지 격자에 의한 변조 주파수는

로 주어진다. 그리고 상기 퍼필 격자의 변조 주파수는

이고, 변조된 신호 주파수는

로 주어질 수 있다. The modulation frequency by the object grid is

And the modulation frequency by the image grid

. And the modulation frequency of the perforated grating is

And the modulated signal frequency is

Lt; / RTI &gt;

Accordingly, the present invention calculates the modulation frequencies σ ₁ and σ ₂ of the object grating and the image grating from the conditions that the wavelength λ of the incident light, the slit pitch P of the perforated grating 204, and the ratio of the object distance Z1 and the image distance Z2 are determined. The slit pitches P1 and P2 of the object grating and the image grating are obtained by taking the inverse of the calculated modulation frequencies σ ₁ and σ ₂ .

The present invention also obtains the distance D _{F at} which the moire image is formed and the period P _N of the modulation intensity change based on the wavelength λ of the incident light and the slit pitch P of the perforated grating, and among the multiples of the period of the modulation intensity change. One is determined as the object distance Z1 between the perforated grating and the object grating, and the image distance Z2 between the perforated grating and the image grating is determined according to the ratio between the object Z1 and the image distance Z2. Here, D _F is determined as P ² / λ.

In Equation 8, P _N is a period of modulation intensity change.

Referring to FIG. 7 which simulates the modulation intensity according to the change in the object distance Z1 between the perforated lattice and the object lattice and the image distance Z2 between the perforated lattice and the image lattice , the modulation intensity according to the change of N The change cycle is changed, and when N is 2, the modulation intensity change cycle is 1/2.

Accordingly, the present invention generates the relative displacement information with high precision by using the repeating pattern grids defined by N as 1 and 2.

FIG. 8 illustrates an example in which the first through fourth photodetectors 108 through 114 for the disc-shaped disc are arranged, and is formed in a fan shape to stably receive light while following the circumference.

Reflective Optics

First, the structure of the reflective optical system will be described with reference to FIG. 9.

Light from the LED module 104 is provided to the second collimated lens unit 400.

The second collimated lens unit 400 collimates and emits light from the LED module 104.

The light collimated by the second collimated lens unit 400 includes a third random code grid 402, a fourth repeating pattern grid 404, and a fifth repeating pattern grid 406 provided in the third plate 410. ) And a third window 408.

The third random code grid 402 partially transmits the light incident through the grid corresponding to the random code pattern according to the random code, which is transmitted to the first random code grid 202 of the disc-shaped disc 200. do. The random code pattern is based on a random code generated using LFSR.

The fourth repeating pattern grid 304 is a repeating pattern grid in which the slit pitch is determined to correspond to the case where N, which represents the order in which the moire pattern is formed in the OTF equation according to the OTF, is an object lattice, and repeats incident light. The transmission is partially transmitted according to the pattern grid, which is transmitted to the first repeating pattern grid 204 of the disc-shaped disc 200.

The fifth repeating pattern grid 406 is a repeating pattern grid in which the slit pitch is determined to correspond to the case where N is 2, which represents the order in which the Moire pattern is formed in the OTF equation according to the OTF as an object lattice, and repeats incident light. The transmission is partially transmitted according to the pattern grid, which is transmitted to the first repeating pattern grid 204 of the disc-shaped disc 200.

The third window 408 transmits incident light to the first window 206.

The third plate 410 on which the third random code grid 402, the fourth repeated pattern grid 404, the fifth repeated pattern grid 406, and the third window 408 are formed has a predetermined third distance. It is installed spaced apart from the disk-shaped disk (200). The third distance is set to a distance to which both N and 1, which represent the order in which the moire pattern is formed in the OTF equation according to the OTF, are applicable.

The first random code grating 202, the first repeating pattern grating 204, and the first window 206 formed on the disc-shaped disc 200 reflect and transmit incident light. Here, the first repeating pattern grid is a perforated grid.

First to fourth photodetectors 108, 110, 112, and 114 are provided on the fourth plate 412 spaced apart from the disc-shaped disc 200 by a predetermined fourth distance. The fourth distance is set to a distance to which both N and 1, which represent the order in which the moire pattern is formed in the OTF equation according to the OTF, are applicable.

The first photodetector 108 includes photodetectors arranged to correspond to a random code pattern according to the random code, through the third random code grid 402 and the first random code grid 202. It receives the transmitted light to generate the absolute displacement detection signal.

In order to simultaneously perform the role of the image grating and the photodetecting device, the second photodetector 110 has a slit pitch corresponding to the case where N represents 1, the order in which the moire pattern is formed in the OTF equation according to the OTF. The photodetector is arranged to correspond to the determined repeating pattern, and receives the light transmitted through the fourth repeating pattern lattice 404 and the first repeating pattern lattice 204 to receive an increase type signal of a first type. Create

In order to simultaneously perform the role of the image grating and the photodetecting device, the third photodetector 112 has a slit pitch corresponding to the case where N is 2, which represents the order in which the moire pattern is formed in the OTF equation according to the OTF. The photodetectors are arranged to correspond to the determined repeating pattern, and receive light transmitted through the fifth repeating pattern grid 206 and the first repeating pattern grid 204 to receive a second type of increased signal. Create

The fourth light detector 114 receives the light transmitted through the first and third windows 206 and 408 to generate a turn detection signal.

The reflective optical system includes a first light in which photodetecting elements are arranged to correspond to the random code pattern using first and third random code grids 202 and 402 to generate absolute displacement information whenever the random code pattern is repeated. The light is transmitted to the detector 108.

In addition, the above-described reflective optical system uses the first and fourth repetitive pattern grids 204 and 404, which are perl gratings and object gratings whose slit pitches are determined to correspond to the case where N is 1, in order to generate the first type of incremental signal. According to the image lattice pattern in which the slit pitch is determined to correspond to the case where N is 1, light is transmitted to the second photodetector 110 in which the photodetectors are arranged, and the period is 1/1 for the incremental signal of the first type. In the case where N is 2 using the perforated lattice and the object lattice first and fifth repeating pattern lattice 204 and 406 whose slit pitches are determined to correspond to the case where N is 2 to generate a second type of incremental signal of 2; The light is transmitted to the third photodetector 112 in which the photodetectors are arranged in accordance with the image lattice pattern in which the slit pitch is determined, and the first and second distances, which are the distance between the first plate and the second plate, are OTF according to OTF It is determined in advance according to the official.

The reflective optical system also transmits light through the first and third windows 206 and 408 for turn detection.

<Signal Processing Unit 116>

Now, the configuration of the signal processor 116 according to the preferred embodiment of the present invention will be described in more detail with reference to FIG. 10.

The signal processor 116 generates an absolute displacement detection information by detecting an absolute displacement detection signal processor 510 for processing an absolute displacement detection signal provided from the first photodetector 108, and a peak of the absolute displacement detection signal. Provide absolute displacement detection information generation unit 504 for generating absolute displacement detection information, and first and second types of incremental signals from the second light detection unit 110 and the third light detection unit 112; An AD converter 500 for receiving an AD conversion, a reference signal correction unit 502 for correcting the AD conversion light detection signal and the absolute displacement detection signal through an adjustment process by a user , and the fourth light detection unit ( A turn detection information generation unit 508 for detecting peaks of the turn detection signals provided by 114 and generating turn detection information accordingly, and a relative displacement detection being an incremental signal of the first and second types AD converted. Information and the absolute displacement detection information and turn detection Merge information and consists of a displacement information generating unit 506 to generate a displacement information.

In the above-described preferred embodiment of the present invention, only the case of employing the LED for irradiating incoherent light as a light source has been described. It is apparent by the present invention that it can.

In addition, while the above-described preferred embodiment of the present invention illustrates the generation of the first and second types of incremental signals, it is also apparent by the present invention to use only one incremental signal in consideration of ease of manufacture.

100: Control device
102: LED driver
104: LED Module
106: optical system
108: first light detector
110: second light detector
112: third light detector
114: fourth light detector
116: signal processing unit

Claims (12)

In the optical encoder,
A first random code grid for partially transmitting the incident light by repeatedly forming a grid corresponding to a random code pattern according to a random code on a path for displacement detection;
A first repeating pattern lattice formed of a lattice according to a first repeating pattern on a path for the displacement detection, the first repeating pattern lattice being a perforated lattice partially transmitting incident light;
Light source;
A second random code grid formed with a grid corresponding to a random code pattern according to the random code and receiving light from the light source and partially transferring the light from the light source to the first random code grid;
A second repeating pattern lattice formed of a lattice according to a second repeating pattern, the second repeating pattern lattice being an object lattice which receives light from the light source and partially transmits the light to the first repeating pattern lattice;
A third repeating pattern lattice formed of a lattice according to a third repeating pattern and being an object lattice that receives light from the light source and partially transmits the light to the first repeating pattern lattice;
A first photodetector arranged to correspond to a random code pattern according to the random code, the first photodetector configured to receive light transmitted by the second random code grid and the first random code grid to generate an absolute displacement detection signal;
The second light is an image grating in which photodetecting elements are arranged to correspond to a fourth repeating pattern, and is an image grating which receives the light transmitted by the second repeating pattern grid and the first repeating pattern grid to generate an increased type signal of a first type. Detection unit;
A third light, which is an image grating in which photodetecting devices are arranged to correspond to a fifth repeating pattern, and receives an image of light transmitted by the third repeating pattern grid and the first repeating pattern grid to generate a second type of incremental signal; Detection unit;
And a signal processor configured to process the absolute displacement detection signal and incremental signals of the first and second types to generate displacement information. The method of claim 1,
A first window formed on the path for detecting the displacement and transmitting incident light;
A second window spaced apart from the first window by a first distance to transmit light from the light source to the first window;
And a fourth photodetector spaced apart from the first window by a second distance to receive light from the first window to generate a turn detection signal and provide the turn detection signal to the signal processor.
And the signal processor generates turn detection information according to the turn detection signal of the fourth light detector and adds the turn detection information to the displacement information. 3. The method of claim 2,
The signal processing unit,
An AD converter which receives the first and second types of incremental signals and converts them into AD;
Absolute displacement detection information generation unit for generating absolute displacement detection information from the absolute displacement detection signal;
A turn detection information generation unit detecting turn peaks of the turn detection signals and generating turn detection information;
And a displacement information generator for generating displacement information by merging the output signal of the AD converter, the absolute displacement detection information, and the turn detection information. The method of claim 1,
The slit pitch of the object grating and the slit pitch of the image grating are determined by taking the inverse of the modulation frequency of the object grating and the modulation frequency of the image grating according to Equation 9,
The object distance Z1 between the perforated lattice and the object lattice is selected as one of multiples for the modulation intensity change period according to Equation 9,
And the image distance Z2 between the perforated grating and the image grating is calculated according to a ratio with the object distance Z1.
Equation 9

In Equation (9), N is an integer indicating the order in which a moire image is formed according to an optical transfer function (OTF),
Z1 is a distance between the perforated lattice and the object lattice,
Z2 is the distance between the perforated grating and the image grating,
P is the slit pitch of the perfill lattice,
P1 is the slit pitch of the object lattice,
P2 is the slit pitch of the image grid,
Λ is the wavelength of incident light,
P _N is a period of modulation intensity change. The method of claim 1,
The second or third light detector,
Photodetecting elements according to a plurality of phases are arranged repeatedly a predetermined number of times according to a predetermined arrangement pattern,
The array pattern is characterized in that the optical detection elements according to the plurality of phases are determined to be dispersed within a plurality of OTF imaging cycles, and that a few optical detection elements are arranged in one OTF imaging period. 6. The method of claim 5,
The plurality of phases are composed of first to fourth phases,
The array pattern includes a light detection device of a first phase, a light detection device of a third phase, a light detection device of a first phase, a light detection device of a third phase, a light detection device of a second phase, and a light detection of a fourth phase. Element, the second phase photodetection element, the fourth phase photodetection element, the first phase photodetection element, the third phase photodetection element, the first phase photodetection element, the third phase photodetection element, An optical encoder including a photodetector in which a plurality of photodetectors are arranged, wherein the photodetector of a second phase, the photodetector of a fourth phase, the photodetector of a second phase, and the photodetector of a fourth phase . 6. The method of claim 5,
A plurality of output terminals of the second or third photodetector are provided to correspond to the OTF imaging period,
Each of the output terminals corresponding to the OTF imaging cycle,
An optical encoder, characterized in that it is connected to a plurality of optical detection elements differently depending on the OTF imaging cycle. 3. The method of claim 2,
The first repeating pattern grid, the first random code grid, the first window,
Partially transmit the incident light, or
And partially reflects and transmits the incident light. The method of claim 1,
And the light emitted from the light source is an incoherent light. The method of claim 1,
The light source is an optical encoder, characterized in that the LED module. The method of claim 1,
A collimating lens unit collimating and emitting light from the light source;
Optical encoder characterized in that it further comprises. The method of claim 1,
The random code is a random code generated through a linear feedback shift register (LFSR);
An optical encoder comprising a light detection unit is arranged a plurality of light detection elements, characterized in that.

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