Method for acquiring moire fringes and applications thereof

Abstract

The application relates to a method for obtaining Moire fringes and application thereof, comprising a plurality of circular fringes, all the circular fringes being coaxial and equidistant, the widths of all the circular fringes in the axial direction being equal, and the circular fringes being capable of reflecting light, transmitting light or self-luminous; further comprising a spiral light-blocking fringe sleeved outside all the circular fringes, the spiral light-blocking fringe being coaxial with the circular fringes, and the spiral light-blocking fringe and the plurality of circular fringes being correspondingly matched so as to generate Moire fringes; an optoelectronic detector is arranged outside the spiral light-blocking fringe, and a detection surface of the optoelectronic detector faces the axial direction of the spiral light-blocking fringe; when all the circular fringes move axially relative to the spiral light-blocking fringe as a whole, the light beams reflected or emitted by the circular fringes are received by the optoelectronic detector after passing through the spiral light-blocking fringe. The axial displacement amount of the circular fringes is converted into the circumferential Moire fringe displacement amount for detection, and the application is applied to the measurement of the Z-axis displacement of numerical control equipment, and can effectively detect in the non-rotating state and the rotating state.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of physical measurement characterized by using optical methods for metrology, and particularly relates to a method for obtaining Moire fringes and its application. BACKGROUND

[0002] The engineering value of the Moire fringe pattern has been recognized and applied, and the most widely used field is the relative displacement measurement of gratings, and there are application products such as grating rulers. The existing grating ruler application products use Moire fringes, which can be seen in the attached Figure 1 , which is mostly in the form of a point light source 100, a lens 101, two measurement gratings (one as a scale grating 102 and the other as an indicator grating 103), and a photoelectric element 104. Specifically, the point light source, the lens, one measurement grating, and the photoelectric element are integrated into a reading detection head, which is moved relative to the other measurement grating. The light beam of the point light source passes through the lens and is transmitted through the two measurement gratings, and the transmitted light is imaged on the photoelectric element. There are several equidistant spaced lines on the two measurement gratings with an inclination angle θ. The Moire fringe phenomenon of the grating is used to realize one-dimensional displacement measurement, i.e. the relative movement of the grating causes the transmitted light intensity to change periodically, and the photoelectric element converts this light intensity signal into a periodic change in electrical signal. The relative displacement of the grating is obtained by the change in the electrical signal.

[0003] However, the manufacturing of measurement gratings is difficult, and the existing technology has a detection method based on Moire fringes disclosed in CN113029008A, which controls a surface array light source to display equidistant and equi-width bright fringes, and a surface array photoelectric detector (CCD) reads signals in an equi-width and equidistant fringe reading band. The fringes are matched with the reading band and have an inclination angle, so that the photoelectric detector can read and obtain Moire fringe data signals. Further processing by a computer can also measure the geometric values of the movement. The mechanism for generating Moire fringes in this way is different from the traditional way, and there are many advantages such as greatly reducing hardware costs.

[0004] It can be seen that it is a very practical and meaningful research direction to study how to generate or obtain Moire fringes, which can well improve and solve the difficulties or bottlenecks faced in the detection of physical quantities in actual working conditions. For example, in the traditional processing industry, a large number of numerical control equipment has been widely used, and there are more and more high-precision numerical control equipment. For the Z-axis that connects the tool and rotates the clamped workpiece, its height can be measured and compensated to ensure that the machining is performed according to the set depth. However, due to long-time operation, thermal expansion and contraction, and other reasons, the Z-axis objectively has a slight change in vertical height, which affects the precision. If this slight change can be effectively detected, even in real time, it can provide the necessary technical support for height compensation and improve the precision of the machine tool! SUMMARY

[0005] In view of the above problems of the prior art, the technical problem to be solved by the present application is to provide another method for obtaining Moire fringes and application thereof, so as to avoid the inconvenience of measuring the slight vertical height change of the Z-axis of the high-precision numerical control equipment, and to achieve the effect of effective detection in both non-rotating state and rotating state.

[0006] To solve the above technical problem, the present application adopts the following technical scheme:

[0007] The method for obtaining Moire fringes comprises a plurality of circular fringes, the plurality of circular fringes are coaxial and arranged at equal intervals along the axial direction, the widths of the plurality of circular fringes in the axial direction are equal, and the circular fringes can reflect light, transmit light or self-illuminate.

[0008] Further, a spiral light-blocking fringe is arranged outside the plurality of circular fringes, the spiral light-blocking fringe is coaxial with the plurality of circular fringes, the pitch of the spiral light-blocking fringe and the interval of the plurality of circular fringes are correspondingly matched to generate Moire fringes.

[0009] An optoelectronic detector is arranged outside the spiral light-blocking fringe, and the detection surface of the optoelectronic detector faces the axial direction of the spiral light-blocking fringe and the plurality of circular fringes.

[0010] When the plurality of circular fringes as a whole moves axially relative to the spiral light-blocking fringe, the light beams reflected, transmitted or emitted by the plurality of circular fringes are received by the optoelectronic detector after passing through the spiral light-blocking fringe, and the optoelectronic detector can read and obtain the Moire fringe data signal with the circumferentially periodic change in intensity.

[0011] Further to the above technical scheme, the number of optoelectronic detectors is multiple, and the optoelectronic detectors are circumferentially and uniformly distributed outside the spiral light-blocking fringe.

[0012] Alternatively, the spiral light-blocking fringe is a multi-start thread, the number of optoelectronic detectors is multiple, and the optoelectronic detectors are circumferentially arranged outside the spiral light-blocking fringe with unequal circumferential intervals.

[0013] The present application also relates to the application of the above method for obtaining Moire fringes, which comprises a numerical control equipment, the numerical control equipment has a Z-axis, the Z-axis has a fixed part and a rotating part rotatably connected to the fixed part, the plurality of circular fringes are fixed on the rotating part, the spiral light-blocking fringe is fixed on the fixed part, and the optoelectronic detector and the spiral light-blocking fringe form a fixed whole.

[0014] Further, the plurality of circular fringes are formed by fluorescent paint coated on the rotating part, the fixed part is further provided with a light source, the light beams emitted by the light source are reflected on the fluorescent paint surface, and the light beams are received by the optoelectronic detector after passing through the spiral light-blocking fringe.

[0015] Optionally, a plurality of light sources are embedded on the rotating part in axial direction, and the plurality of light sources form the plurality of circular stripes when the rotating part rotates; the light beams emitted by the light sources are received by the photoelectric detector after passing through the spiral light blocking stripes.

[0016] Further, the plurality of circular stripes are fixed on the rotating part near the free end thereof.

[0017] Compared with the prior art, the present application has the following beneficial effects:

[0018] 1. The method for obtaining the Moiré stripe can convert the axial displacement of the circular stripe relative to the spiral light blocking stripe into the circumferential Moiré stripe displacement, and the axial relative displacement can be calculated by reading and obtaining the Moiré stripe through the photoelectric detector. When applied to the measurement of the vertical height micro-variation of the Z-axis, the vertical height micro-variation of the Z-axis can be detected in the static state (non-rotating state) due to the particularity of the circular stripe, and the vertical height micro-variation of the Z-axis can also be detected in the rotating state in use, which cannot be achieved by the ordinary Moiré stripe obtaining method, and is not limited by the rotating speed, and can provide technical support for the compensation setting, and is beneficial to further improve the precision of the high-precision equipment.

[0019] 2. The method for obtaining the Moiré stripe, the spiral light blocking stripe adopts a multi-start thread, and there are a plurality of complete signal periods on one circumference, and in addition to the light intensity fitting method for calculating the displacement, the peak number counting method can also be used to convert the displacement. A new Moiré stripe generating method and a new calculation method are provided.

[0020] 3. The Moiré stripe generated in the present application is periodically distributed on the circumference, the number of periods is the same as the number of light blocking stripe heads, the Moiré stripe intensity distribution has a circular closed characteristic, the high-precision measurement of the Moiré stripe position can be realized by using the circular closed characteristic, and the axial displacement measurement precision is improved. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The schematic diagram of the Moiré stripe obtaining and application method in the conventional method mentioned in the background art;

[0022] Figure 2 The schematic diagram of the method for obtaining the Moiré stripe in the specific embodiment (for easy observation, the circular stripe does not fall into the spiral light blocking stripe);

[0023] Figure 3 The schematic diagram of the five-start spiral light blocking stripe that can be used for the description in the embodiment;

[0024] Figure 4This is a top view schematic diagram of the photodetector in the embodiment, with the photodetector evenly distributed outside the spiral light-blocking stripes;

[0025] Figure 5 This is a schematic diagram of the spiral light-blocking stripes covering the outer edge of the circular stripes in the embodiment;

[0026] Among them, circular stripe 1, spiral light-blocking stripe 2, and photodetector 3. Detailed Implementation

[0027] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0028] Please see Figure 2 , Figure 5 The method for obtaining moiré fringes in a specific embodiment includes a plurality of circular fringes 1, which are coaxial and equally spaced along the axial direction. The circular fringes 1 have equal widths in the axial direction and can be reflective, translucent, or self-luminous.

[0029] It also includes a spiral light-blocking stripe 2 that is sleeved on the outside of the plurality of circular stripes 1. The spiral light-blocking stripe 2 is coaxial with the plurality of circular stripes 1. The width of a single spiral on the spiral light-blocking stripe 2, the pitch of adjacent spirals and the width and spacing of the plurality of circular stripes 1 are matched accordingly to generate moiré fringes.

[0030] A photodetector 3 is provided on the outer side of the spiral light-blocking stripe 2, and the detection surface of the photodetector 3 faces the axial direction of the spiral light-blocking stripe 2 and the plurality of circular stripes 1.

[0031] When the plurality of circular stripes 1 move axially relative to the spiral light-blocking stripe 2 as a whole, the light beams reflected, transmitted, or emitted by the plurality of circular stripes 1 are received by the photodetector 3 after passing through the spiral light-blocking stripe 2. The photodetector 3 can read and obtain the moiré fringe data signal with circumferential periodic intensity changes.

[0032] The method for obtaining moiré fringes in this embodiment converts the axial displacement of the circular fringe 1 relative to the helical light-blocking fringe 2 into a circumferential moiré fringe displacement, which is then read by a photodetector 3, and the corresponding relative axial displacement can be calculated. When applied to measure minute changes in the vertical height of the Z-axis of CNC equipment, due to the special nature of the circular fringe 1, it can detect minute changes in the vertical height of the Z-axis not only in a static (non-rotating) state, but also in real time during rotation. This is a new effect that existing ordinary moiré fringe acquisition methods cannot achieve, and it is not limited by rotational speed, providing technical support for compensation settings and helping to further improve the accuracy of high-precision equipment. In implementation, the helical light-blocking fringe can be a single-start or multi-start thread.

[0033] The method can also effectively utilize the self-closing property of the circle in the prior art to improve the detection accuracy. The Moire fringes obtained by the method will form a complete period in a circle, which is beneficial to detection correction, and the movement amount of the Moire fringes can be accurately measured.

[0034] In implementation, please refer to Figure 4 The number of the photodetectors 3 can be multiple (four are shown) and are arranged in a circumferential direction outside the spiral light blocking stripe 2.

[0035] In this way, the movement amount of the Moire fringes can be more accurately obtained through intensity fitting.

[0036] In addition, as another implementable manner, the spiral light blocking stripe 2 is a multi-start thread (also referred to as a multi-threaded thread), and the number of the photodetectors 3 is multiple and arranged in a circumferential direction outside the spiral light blocking stripe 2 with unequal circumferential spacings.

[0037] In this way, please refer to Figure 3 For example, if the spiral light blocking stripe 2 is a five-start thread, there are five complete signal periods in a circle. In addition to the intensity fitting of the light intensity to calculate the displacement amount, the displacement amount can also be converted by counting the peak number. In theory, the latter is more efficient and has lower requirements for the configuration of the detection and calculation hardware.

[0038] The application also provides an application of the above-mentioned Moire fringe acquisition method, including a numerical control device, the numerical control device has a Z-axis (not shown in the figure), the Z-axis has a fixed part with random bed lifting and a rotating part rotatably connected to the fixed part, the free end of the rotating part is connected to a tool, the plurality of circular stripes 1 are fixed on the rotating part, the spiral light blocking stripe 2 is fixed on the fixed part, and the photodetector 3 and the spiral light blocking stripe 2 are a fixed whole.

[0039] In specific application and detection, the forms can be various, which are not listed here, and the following simple examples are given:

[0040] The plurality of circular stripes 1 can be formed by fluorescent paint coated on the rotating part, and the fixed part is also provided with a light source. The light beam emitted by the light source is reflected on the fluorescent paint surface, and is received by the photodetector 3 after passing through the spiral light blocking stripe 2.

[0041] The plurality of circular stripes 1 can also be transparent and not rotating, and a light source is arranged on the axis. The Moire fringes formed by the light emitted by the light source passing through the circular stripes 1 and the light blocking stripe 2 in turn are received by the photodetector 3, that is, the light transmission form. This form is beneficial to high-precision axial displacement measurement by utilizing the self-closing property of the Moire fringe emphasized distribution circle.

[0042] Also can be: the rotating part is embedded with several light sources along the axial direction, when the rotating part rotates, the several light sources form the several circular stripes 1; the light beams emitted by the light sources are received by the photoelectric detector 3 after passing through the spiral light blocking stripes 2. This mode is particularly suitable for real-time detection of the rotating state.

[0043] When there is no suitable carrier site on the Z axis, the several circular stripes 1 can also be arranged on a cylinder, and the cylinder is fixed outside the rotating part; the spiral light blocking stripes 2 can also be opaque light blocking paint coated on the transparent cylinder, and then fixedly connected to the fixed part, and the photoelectric detector 3 is fixed outside the transparent cylinder; there is also a mode, which does not form an integral visible spiral light blocking stripe 2, but only the part of the spiral light blocking stripe 2 in front of the receiving end of the photoelectric detector 3 in the foregoing mode is directly coated on the transparent surface of the receiving end of the photoelectric detector 3, which can also achieve the same effect, and this implementation form should also fall within the protection scope of the present application.

[0044] Considering thermal expansion and contraction and end effect, in order to make the detection more effective, the several circular stripes 1 are preferably fixed on the rotating part near the free end thereof.

[0045] Finally, it should be pointed out that the above embodiments are only used to illustrate the technical solutions of the present application and are not limiting, although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced equivalently without departing from the purpose and scope of the technical solutions of the present application, and they should all be covered in the scope of the claims of the present application.

Claims

1. An application of a method for obtaining moiré fringes, including a CNC machine having a Z-axis, the Z-axis having a fixed part and a rotating part rotatably connected to the fixed part, characterized in that: It also includes several circular stripes, which are coaxial and equally spaced along the axial direction. The width of the circular stripes is equal in the axial direction. The circular stripes can reflect light, transmit light, or emit light on their own. It also includes a spiral light-blocking stripe sleeved on the outside of the plurality of circular stripes. The spiral light-blocking stripe is coaxial with the plurality of circular stripes, and the pitch of the spiral light-blocking stripe and the spacing of the plurality of circular stripes are matched accordingly to generate moiré fringes. A photodetector is provided on the outer side of the spiral light-blocking stripe, and the detection surface of the photodetector faces the axial direction of the spiral light-blocking stripe and the plurality of circular stripes. When the plurality of circular stripes move axially relative to the spiral light-blocking stripes as a whole, the light beams reflected, transmitted, or emitted by the plurality of circular stripes are received by the photodetector after passing through the spiral light-blocking stripes. The photodetector can read and obtain the moiré fringe data signal with circumferential periodic intensity changes. The circular stripes are fixed on the rotating part, and the spiral light-blocking stripes are fixed on the fixed part, with the photodetector and the spiral light-blocking stripes forming a fixed whole.

2. The application of the method for obtaining moiré fringes according to claim 1, characterized in that: There are multiple photodetectors, which are evenly distributed circumferentially on the outside of the spiral light-blocking stripes.

3. The application of the method for obtaining moiré fringes according to claim 1, characterized in that: The spiral light-blocking stripes are multi-start threads.

4. The application of the method for obtaining moiré fringes according to claim 3, characterized in that: There are multiple photodetectors arranged circumferentially on the outside of the spiral light-blocking stripes, with varying circumferential spacing.

5. The application of the method for obtaining moiré fringes according to claim 1, characterized in that: The circular stripes are formed by fluorescent paint applied to the rotating part. A light source is also provided on the fixed part. The light beam emitted by the light source is reflected on the fluorescent paint surface and received by the photodetector after passing through the spiral light-blocking stripes.

6. The application of the method for obtaining moiré fringes according to claim 1, characterized in that: A plurality of light sources are embedded at intervals along the axial direction on the rotating part. When the rotating part rotates, the plurality of light sources form the plurality of circular stripes. The light beam emitted by the light sources is received by the photodetector after passing through the spiral light-blocking stripes.

7. The application of the method for obtaining moiré fringes according to claim 1, characterized in that: The circular stripes are fixed on the rotating part near its free end.

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