CN102628811B - Verifying device of grating groove defect - Google Patents

Abstract

A verifying device of a grating groove defect aims at resolving the problem that a main ruler has the conditions of stain and inconsistency of front and back phases in the manufacture process of a grating ruler, and a manual method cannot finish verifying of the grating ruler. A first shifting driving device of the verifying device drives a signal detection head to move along the detection direction, the signal detection head detects light transmitted by a light source and modulated by a grating to be measured and a standard grating, the light is converted into electric signals through a photoelectric detector, amplification processing and analog-digital conversion are conducted through a signal processing module on the electric signals, finally a pulse detection module is used for detecting and scoring the defect and copying existence and position of the defect through pulse signals, a second shifting driving device moves the position of the standard grating, and the processing is repeated till the detection finished. The verifying device is used for measuring the defect of long grating, groove evenness detection and phase consistency detection of a length grating ruler.

Description

Grating Line Defect Inspection Device

technical field

The invention relates to a device for inspecting line defects of a grating ruler.

Background technique

The primary task of achieving high-precision measurement of grating displacement sensors is to ensure the scoring and copying accuracy of standard gratings. The marking accuracy is usually relatively high, but there are also cases where the black-and-white ratio does not meet the requirements; The stains caused, or the certain distortion of the light will affect the phase consistency, etc., which will seriously affect the accuracy of the final grating ruler. Not only that, the lengthening error existing in the grating lengthening process will also greatly reduce the accuracy and performance of the entire grating scale.

After the general grating scale is marked or copied, due to the large amount of data, it is impossible to fully detect the marking accuracy with the naked eye by using a general microscope. At the same time, the inconsistency of the front and rear phases cannot be observed with the naked eye. If specific detection equipment can be made, and effective detection methods can be used to automatically record the stains on the main scale of the grating scale and the inconsistency of the front and rear phases, it can be effectively improved. Improve the accuracy of the finished grating ruler, improve production efficiency and production quality.

Contents of the invention

The invention provides a grating line defect inspection device to solve the problem that the existing grating ruler has stains and phase inconsistencies between the front and rear sides in the manufacturing process of the grating ruler, and the inspection of the grating ruler cannot be completed manually.

A grating line defect inspection device, which includes a standard grating, a signal detection head, a first displacement drive device, a second displacement drive device, a signal processing module, and a pulse detection module; the first displacement drive device moves along the standard grating Move the signal detection head in the scanning direction of the length, and the signal detection head records the modulated light intensity information,

The second displacement driving device is used to drive the moving position of the standard grating, and the signal processing module receives the displacement information of the first displacement driving device, the light intensity information output by the signal detection head and the standard grating output by the second displacement driving device The position information; and the position information is subjected to signal amplification and digital-to-analog conversion processing, and output to the pulse detection module; the pulse detection module detects the received signal, and analyzes the position information of the grating line defect to be tested;

The specific process is: the pulse detection module records all the scanning data, and after the scanning of the standard grating is completed, the positions of the grating marking defects and copying defects to be tested are analyzed;

First, the pre-calibrated amplitude changes with the phase difference, expressed as:

formula one, $A=A_0\×\cos (2\×\mathrm{\π}\×\frac{x}{T})+B_0;$

In the formula, A is the output value of the signal processing module, A ₀ and B ₀ are constants, π is the circumference ratio, T is the reticle period of the standard grating, and x is the displacement deviation equivalent to the phase difference;

Then average the output values A of all read points to obtain the average value M, and obtain the average difference of the phase difference, which is expressed as:

Formula two, $\mathrm{\θ}={\cos }^{-1}\left(\frac{m-B_0}{A_0}\right);$

Finally, analyze the phase corresponding to the amplitude of each point point by point, calculate the phase difference corresponding to the amplitude change, and judge whether the grating to be tested is qualified according to the requirements of the phase difference.

Beneficial effects of the present invention: the present invention provides a device with simple principle and capable of effectively detecting stains and phase inconsistencies. The device of the invention automatically records the performance of the grating scale to be tested, thereby quickly and accurately judging whether the grating scale to be tested meets the production requirements.

Description of drawings

FIG. 1 is a schematic diagram of a grating line defect inspection device according to the present invention;

Fig. 2 is a schematic diagram of the variation of the output amplitude of the detection signal of the pulse detection module with the distance in the grating groove defect inspection device according to the present invention;

Fig. 3 is a schematic diagram of the phase deviation detected by the pulse detection module changing with distance in the inspection device for grating rule line defects according to the present invention;

Fig. 4 is a schematic diagram of a signal detection head in the inspection device for grating rule line defects according to the present invention.

Detailed ways

This embodiment is described in conjunction with FIG. 1 , a grating groove inspection device, the detection device includes a standard grating 3, a signal detection head 1, a first displacement drive device 7, a second displacement drive device 9, a signal processing module 8, a pulse The detection module 10 , the signal detection head 1 further includes a light source 5 , an optical system 6 , and a signal detection chip 2 . The first displacement drive device 7 drives the signal detection head 1 to move the position; the second displacement drive device 9 drives the standard grating 3 to move the position; the signal processing module 8 pairs the signal detection head 1, the first displacement drive device 7, the second displacement drive device The information obtained by the two-shift driving device 9 is converted and processed; the pulse detection module 10 is used to analyze and calculate the phase distribution of the grating to be measured 4; the standard grating 3 is a standard component used to detect the grating to be measured, which has a higher reticle Accuracy, usually the standard grating that has passed the standard inspection, its grating pitch is equal to the target grating pitch of the grating to be tested, and its black and white ratio deviation is also qualified. The quality of the standard grating 3 determines the detection accuracy. The light source 5 can be a laser diode, which emits coherent light. The optical system 6 converts the light emitted by the light source into collimated light, which is irradiated onto the grating 4 to be tested. The position of the signal detection head 1 is controlled by the first displacement drive device 7, and the first displacement drive device 7 moves the signal detection head 1 in the scanning direction. The signal detection head 1 detects the optical signal emitted by the light source 5 and modulated by the grating to be tested 4 and the standard grating 3, and converts it into an electrical signal, which is amplified and processed by the signal processing module 8 and converted from analog to digital, and finally the pulse detection module 10 Detect the existence and position of the scribe defect and copy defect through the pulse signal, then change the position of the standard grating 3 through the second shift drive device 9, and repeat the above process until the detection is completed.

When the signal detection head 1 scans, the first displacement drive device 7 and the second displacement drive device 9 will adjust the positions of the signal detection head 1 and the standard grating 3 respectively, so that the signal detection head 1 is at the new position of the grating to be measured 4 to rescan. The signal detection chip 2 can be used as a photodetection element, and a silicon photocell can be selected.

The pulse detection module 10 described in this embodiment records all the scanning data, and after the scanning of the standard grating 3 is completed, the existence and position of the marking defects and replication defects of the grating 4 to be tested are analyzed.

The pulse detection module 10 described in this embodiment records all the scanning data, and after the scanning is completed, the presence and location of the marking defects and replication defects of the grating 4 to be tested are analyzed.

The working process of the device of the present invention is as follows: first place the grating 4 to be measured on the device, place the signal detection head 1 and the standard grating 3 at the initial position, and the first displacement drive device 7 moves the position of the signal detection head 1 along the scanning direction , the speed can be set, the signal detection head 1 records the light intensity information in the moving process, and the signal processing module 8 obtains the standard grating 3 obtained from the second shift drive device 9 according to the shift information of the first shift drive device 7 The position information of the signal detection head 1 and the output information of the signal detection head 1, and through basic processing such as signal amplification and digital-to-analog conversion, obtain the relationship between the position and the amplitude within the length of the standard grating 3 within the range of L, and output it to the pulse detection module 10, pulse detection The module 10 analyzes the signal detection information, and then the second displacement driving device 9 moves the standard grating 3 to a new designated position, the first displacement driving device 7 adjusts the signal detection head 1 to a new initial position, and repeats the above scanning operation , until the scanning work of the grating 4 to be tested is completed, it is worth mentioning that the above pulse detection module 10 can analyze the signal detection information section by section, or it can not be analyzed until the scanning work is completed. There needs to be a section of overlap between adjacent sections in order to obtain phase consistency information between sections.

The analysis process of the signal detection data will be described in detail below.

Combining with Fig. 2, the relationship curve between a section of detection distance obtained by scanning and the signal output amplitude is firstly expressed as:

$A=A_0\×\cos (2\×\mathrm{\π}\×\frac{x}{T})+B_0$ formula one

Here A represents the output value of the signal processing module 8, A ₀ and B ₀ are both constants, π represents the circumference ratio, T represents the reticle period of the standard grating 3, such as 20 microns, and x represents the displacement deviation equivalent to the phase difference.

First, average all the read points to get the average value M, knowing that the average difference of the phase difference is expressed by formula 2:

$\mathrm{\θ}={\cos }^{-1}\left(\frac{m-B_0}{A_0}\right);$ formula two

Here the phase difference: $\mathrm{\θ}=2\×\mathrm{\π}\×\frac{x}{T}.$

Then analyze the phase corresponding to the amplitude of each point point by point. Since the arccosine function may have two results, however, due to the continuity between adjacent points, we only need to take one of the values arbitrarily, and we can still calculate The phase difference corresponding to the amplitude change. Through calculation, we know that the phase difference changes with the distance in any section. Combining with Figure 3, we only need to judge whether the grating to be tested is qualified according to the specific phase difference requirements. For example, when the phase difference requirement is set to 5° , then point A in Figure 3 is a disqualified place, then it can be judged that the ruler to be inspected cannot pass the inspection due to contamination or spots at point A.

The following is an introduction to the method of detecting the phase consistency before and after the full scale.

In conjunction with Fig. 1, when the first displacement drive device 7 completes the first scan of the standard grating 3, the pulse detection module 10 can simultaneously divide the scanning length L into two sections before and after, and average the phases of the two sections before and after, respectively. Get θ ₂ and θ ₁ , and thus get the phase difference Δ ₁ between the first half and the second half,

Where: Δ ₁ = θ ₂ - θ ₁ .

Move the standard grating 3 by the second displacement driving device 9, and the moving distance is The first displacement driving device 7 drives the signal detection head 1 to complete the second scan of the standard grating 3, and obtains the phase difference of the first half and the second half in the second scan by calculating the phase difference of the first half and the second half above. phase difference Δ ₂ , so until the grating 4 to be tested is scanned, and every The phase difference of the distance, Δ ₁ , Δ ₂ , Δ ₃ , Δ ₄ , Δ ₅ ,….

If the front and rear phase difference curves are required, it is only necessary to accumulate the above phases step by step, for example, the phase difference Δ between the first segment and the fifth segment is required, here each The distance is one segment, and the formula is obtained:

Claims (3)

1. Grating line defect inspection device, the device includes a standard grating (3), a signal detection head (1), a first displacement drive device (7), a second displacement drive device (9), a signal processing module (8 ) and pulse detection module (10); it is characterized in that, The first displacement drive device (7) moves the signal detection head (1) along the length scanning direction of the standard grating (3), the signal detection head (1) records the modulated light intensity information, and the second displacement drive The device (9) is used to drive the moving position of the standard grating (3), and the signal processing module (8) receives the displacement information of the first displacement drive device (7), the light intensity information output by the signal detection head (1) and The position information of the standard grating (3) output by the second displacement driving device (9); and the position information is subjected to signal amplification and digital-to-analog conversion processing, and is output to the pulse detection module (10); The pulse detection module (10) detects the received signal, and analyzes the position information of the line defect of the grating (4) to be tested; The specific process is: the pulse detection module (10) records all the scanning data, and after the standard grating (3) is scanned, the position of the marking defect and the copying defect of the grating to be tested (4) is analyzed; Scan the standard grating (3) segment by segment, the specific process is as follows: First, the pre-calibrated amplitude changes with the phase difference, expressed as: formula one, $A=A_0\×\cos (2\×\mathrm{\π}\×\frac{x}{T})+B_0;$ In the formula, A is the output value of the signal processing module (8), A ₀ and B ₀ are constants, π represents the circumference ratio, T is the grating period of the standard grating (3), and x is the displacement deviation equivalent to the phase difference ; Then average the output values A of all read points to obtain the average value M, and obtain the average difference of the phase difference, which is expressed as: Formula two, $\mathrm{\θ}={\cos }^{-1}\frac{(m-B_0)}{A_0};$ Finally, analyze the phase corresponding to the amplitude of each point point by point, calculate the phase difference corresponding to the amplitude change, and judge whether the grating (4) to be tested is qualified according to the requirements of the phase difference. 2. The inspection device for grating rule line defects according to claim 1, characterized in that, the signal detection head (1) comprises a light source (5), an optical system (6) and a signal detection chip (2), the light source ( 5) The emitted optical signal is converted into collimated light by the optical system (6), and the signal detection chip (2) is used to detect the light intensity information modulated by the grating to be tested (4) and the standard grating (3). 3. The inspection device for grating rule line defects according to claim 1, characterized in that, the pulse detection module (10) calculates the phase difference between each position point through the signal amplitude.