Method for correcting reticle errors caused by surface type errors of grating blanks
Technical Field
The invention relates to the technical field of diffraction grating preparation, in particular to a method for correcting a scribing error caused by a surface type error of a grating blank.
Background
The mechanical etching method is one of the main methods for manufacturing a grating master plate, and gratings with deep groove depth, high diffraction efficiency and strict groove requirements, such as infrared gratings and most echelle gratings, are generally manufactured by the mechanical etching method. The surface shape error of the grating blank directly affects the position error of grating lines and further affects the diffraction wavefront quality of the grating, and the measurement, correction and control are required.
Factors influencing the surface shape error of the grating blank mainly comprise the processing quality of the surface shape of the grating substrate and the uniformity of the film layer. In the prior art, the processing quality of the surface type of the grating substrate is mainly ensured by optical processing, the processing cost and difficulty are higher when the size is larger, and the surface type of the grating substrate with the diameter larger than 500mm is difficult to be processed to be better than lambda/6 (@632.8 nm). In addition, the uniformity of the grating film layer is mainly ensured by adjusting the parameters of a film coating machine, especially the coating of the large-size echelle grating film layer, the grating size is large, the film layer is 10 microns or more, large-size coating equipment is needed, the required cost is high, the parameters of the film coating machine need to be repeatedly adjusted in order to obtain the optimal value of the film coating uniformity, however, for the film layer with the size larger than 500mm and the film layer thickness larger than 10 microns, the uniformity of the film coating machine hardly reaches the index requirement superior to 0.5%.
Therefore, a new method for correcting the scribing error caused by the processing quality of the grating substrate surface type and the uniformity of the film layer is needed to solve the above problems.
Disclosure of Invention
The invention aims to provide a method for correcting a scribing error caused by a surface type error of a grating blank, aiming at the defects in the prior art, and solving the problems of high cost, high difficulty, difficulty in reaching a higher level and the like in the correction method in the prior art.
The object of the invention can be achieved by the following technical measures:
the invention provides a method for correcting a scribing error caused by a surface type error of a grating blank, which comprises the following steps of:
step S1: coating a film layer on the grating substrate by using a coating machine to prepare a grating blank;
step S2: measuring the wave front error value of the surface to be scribed of the grating blank;
step S3: collecting the wavefront error values and establishing a zero-order wavefront error matrix deltanm,
Wherein the rows represent different positions of the same reticle, the columns represent different reticles, δnmThe wave front error value of the nth position of the mth reticle is indicated, m and n are natural numbers, and m and n are more than or equal to 2;
step S4: on the basis of the zero-order wavefront error matrix, a reticle error matrix xi caused by the surface type error of the grating blank is obtained by using the scalar theory of geometric optics and grating diffractionnm,
Wherein alpha is an incident angle and beta is a diffraction angle;
step S5: mounting the grating blank on a workbench of a ruling machine, adjusting the position of the grating blank on the workbench, and positioning;
step S6: determining zero positions and scribing areas of the grating blank in the scribing direction and the indexing direction;
step S7: writing the scribed line error matrix in the scribed area into an operation program of a scribing machine;
step S8: and during grating ruling, measuring the position of the grating ruling tool relative to the grating blank, correcting the ruling error caused by the face shape error of the grating blank in real time through a ruling machine micro-positioning system according to the ruling error matrix, and completing the ruling of the grating.
Furthermore, the grating blank positioning device further comprises a scribing limiting block and an indexing limiting block which are respectively arranged in the scribing and indexing directions of the grating blank, and the positioning of the grating blank is realized through the scribing limiting block and the indexing limiting block.
Further, the step S6 is specifically:
step S61: adjusting the workbench to move to the initial position of grating ruling;
step S62: adjusting the running stroke of the nicking tool to ensure the length of the grating groove;
step S63: operating a ruling machine to carve a single grating groove by a falling knife;
step S64: taking out the grating blank, measuring the position relation of the single grating groove relative to the edge of the grating blank, and determining the corresponding relation between the position of the single grating groove and the zero-order wavefront error matrix;
step S65: and positioning and putting the grating blank back to the original position through the arranged limiting block.
Furthermore, the wavefront error value is measured by an interferometer and is determined by the processing precision and the coating uniformity of the grating substrate.
Further, the processing precision of the grating substrate is less than 1 times of lambda, wherein lambda is 632.8 nm.
Further, the uniformity requirement of the film layer of the grating blank is as follows: the diameter of the grating substrate is more than 500mm, and when the thickness of the film layer is more than 10um, the uniformity is better than 10%.
Further, the measurement of the position of the grating ruling tool relative to the grating blank is realized through a laser interferometer or a grating interferometer.
The method for correcting the groove error caused by the surface type error of the grating blank corrects the groove error caused by the surface type error of the carved grating blank through micro-positioning control, has low requirements on the processing quality of a grating substrate, the size of a film coating machine and the uniformity of the film coating machine, greatly reduces the manufacturing difficulty of the grating blank and the requirements on the film coating machine, is not limited by the processing level and the film coating process level of the grating substrate, and is more easy to obtain higher wavefront quality especially for large-size gratings.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic flow chart of the method for correcting the reticle error caused by the face shape error of the grating blank according to the present invention;
fig. 2 is a detailed flowchart of step S6;
FIG. 3 is a schematic structural diagram of a grating blank, a limiting block and a single reticle;
description of reference numerals: 1-scribing a limit block; 2-indexing a limiting block; 3-grating blank; 4-single score line.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.
In order to make the description of the present disclosure more complete and complete, the following description is given for illustrative purposes with respect to the embodiments and examples of the present invention; it is not intended to be the only form in which the embodiments of the invention may be practiced or utilized. The embodiments are intended to cover the features of the various embodiments as well as the method steps and sequences for constructing and operating the embodiments. However, other embodiments may be utilized to achieve the same or equivalent functions and step sequences.
As shown in fig. 1 to 3, the present invention provides a method for correcting a reticle error caused by a face shape error of a grating blank, comprising the following steps:
step S1: coating a film layer on the grating substrate by using a coating machine to prepare a grating blank 3;
step S2: measuring the wave front error value of the surface to be scribed of the grating blank 3;
step S3: collecting the wavefront error values and establishing a zero-order wavefront error matrix deltanm,
Wherein the rows represent different positions of the same reticle, the columns represent different reticles, δnmThe wave front error value of the nth position of the mth reticle is indicated, m and n are natural numbers, and m and n are more than or equal to 2;
step S4: on the basis of the zero-order wavefront error matrix, a scale error matrix xi caused by the surface type error of the grating blank 3 is obtained by using the scalar theory of geometric optics and grating diffractionnm,
Wherein alpha is an incident angle and beta is a diffraction angle;
step S5: installing the grating blank 3 on a workbench of a ruling machine, adjusting the position of the grating blank 3 on the workbench, and positioning;
step S6: determining zero positions and scribing areas of the grating blank 3 in the scribing direction and the indexing direction;
step S7: writing the scribed line error matrix in the scribed area into an operation program of a scribing machine;
step S8: and during grating ruling, measuring the position of the grating ruling tool relative to the grating blank 3, correcting a ruling error caused by a face shape error of the grating blank 3 in real time through a ruling machine micro-positioning system according to a ruling error matrix, and completing the ruling of the grating.
The grating blank positioning device is characterized by further comprising a scribing limiting block 1 and an indexing limiting block 2 which are respectively arranged in the scribing and indexing directions of the grating blank 3, and the positioning of the grating blank 3 is realized through the scribing limiting block 1 and the indexing limiting block 3.
Wherein, the step S6 specifically includes:
step S61: adjusting the workbench to move to the initial position of grating ruling;
step S62: adjusting the running stroke of the nicking tool to ensure the length of the grating groove;
step S63: a single grating scribed line 4 is scribed by operating a scribing machine;
step S64: taking out the grating blank 3, measuring the position relation of the single grating groove 4 relative to the edge of the grating blank 3, and determining the corresponding relation between the position of the single grating groove and the zero-order wavefront error matrix;
step S65: positioning and replacing the grating blank 3 by the arranged limit blocks (the scribing limit block 1 and the indexing limit block 2).
The wavefront error value is measured by an interferometer, preferably a Zygo interferometer, and is determined by the processing precision and the coating uniformity of the grating substrate. In step S1, the requirement for the processing accuracy of the grating substrate is greatly reduced, and the processing accuracy may be greater than λ or less than 1 time λ, where λ is 632.8 nm. The size of the film plating machine used in step S2 is required to meet the requirement of the grating size, but there is no high requirement for the uniformity of the film plating, and the requirement for the uniformity of the film layer of the grating blank 3 is as follows: when the diameter of the grating substrate is more than 500mm and the thickness of the film layer is more than 10um, the uniformity is better than 10 percent. The step S8 of measuring the position of the grating ruling tool relative to the grating blank may be implemented by a laser interferometer or a grating interferometer, etc.
The method for correcting the groove error caused by the surface type error of the grating blank corrects the groove error caused by the surface type error of the carved grating blank through micro-positioning control, has low requirements on the processing quality of a grating substrate, the size of a film coating machine and the uniformity of the film coating machine, greatly reduces the manufacturing difficulty of the grating blank and the requirements on the film coating machine, is not limited by the processing level and the film coating process level of the grating substrate, and is more easy to obtain higher wavefront quality especially for large-size gratings.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.