Background
With the development of information technology, the amount of data generated is increasing explosively, and the demand for data storage density and data conversion rate is increasing dramatically. Conventional data storage technologies have hardly satisfied the data growth requirements, and new generation storage technologies are urgently developed. Holographic storage technology, which is a three-dimensional volume storage technology, has an ultra-high theoretical storage density and an ultra-fast data conversion rate, is considered as a powerful competitor to the next generation of storage technology.
Currently, an amplitude type holographic storage system is one of the most studied holographic storage systems because a CCD detector can directly detect intensity information, and an amplitude type spatial light modulator such as a DMD (digital micromirror device) can provide a very high refresh rate, which can increase the conversion rate of data.
The digital micromirror device (Digital Micromirror Device, abbreviated as DMD) is a micro-electro-mechanical system, which is composed of a two-dimensional micromirror array, wherein the micromirror optical switch array is integrated on a microchip by adopting a monolithic manufacturing technology of CMOS technology, and each micromirror can individually perform two states of positive and negative 12 degrees around an axis, so that the amplitude of a light field can be modulated. Each optical switch has a mirror coupled to a memory cell. By controlling the charge state of the storage unit, the rotation motion of the micro-reflector around the fixed shaft and the time response are changed, so that the modulation of the light angle direction and dead time passing through each unit reflection component and emission is realized. The DMD can realize the modulation and gating of the space of light rays, the time required by gating is microsecond, and mechanical movement does not exist in the device in the modulation process, but the DMD can only realize the light beam modulation of a space two-dimensional plane, and the coding and the modulation of the space propagation angle cannot be realized.
In the laser direct imaging system, the long side direction of the mounting surface of the DMD and the stepping direction of exposure theoretically need to maintain an ideal working angle theta, so that the left and right adjacent strips of the exposed pattern have no error of vertical dislocation. In fact, after the DMD is mounted and fixed, there is always an operating angle error e between the actual assembly angle θ ' of the DMD and the ideal operating angle θ, e=θ ' - θ, and in order to calculate the magnitude of the error, the actual assembly angle θ ' of the DMD, that is, the deflection angle of the micromirror needs to be measured, and then the operating angle error e is obtained by combining the ideal operating angle θ.
Currently, the allowable range of angle error of a Texas Instrument (TI) of a known DMD manufacturer in the world is ±1°, which can meet most of basic applications of the DMD, but the angle error of the DMD is required to be relatively high in some application fields with high precision requirements, such as holographic storage, maskless lithography, super-resolution microscopy and the like, so that a more accurate method for detecting the deflection angle of the micromirror of the DMD is needed to be provided for accurately measuring the angle error of the DMD.
At present, although some micromirror deflection angle detection systems of DMDs are already appeared in the market, the defects of complex structure, high manufacturing cost, low detection accuracy, complex operation and difficult mastering of the detection device exist in many cases. Therefore, the micromirror deflection angle detection system of the DMD, which has the advantages of simple structure, easy implementation, accurate detection of the micromirror deflection angle of the DMD and simple operation process, is one of technical problems to be solved urgently by those skilled in the art.
Disclosure of Invention
The invention aims at solving the technical problems and provides a method and a device for detecting the deflection angle of a micromirror of a DMD (digital micromirror device) so as to realize accurate and convenient detection of the deflection angle of the micromirror of the DMD.
In view of the above, the present invention provides a method for detecting a micromirror deflection angle of a DMD, comprising the steps of:
S1, sequentially placing a DMD chip, a diaphragm I, a diaphragm II and a laser emitter so that central points of the DMD chip, the diaphragm I, the diaphragm II and the laser emitter are positioned on the same straight line;
S2, under the state that the power supply of the DMD chip is disconnected, the position of the laser transmitter is adjusted, so that a first laser beam emitted by the laser transmitter passes through the diaphragm II and the diaphragm I at the same time, and is beaten in the central area of the DMD chip, the fixed angle of the DMD is adjusted, and the light source reflected by the DMD returns to the diaphragm I and the diaphragm II;
S3, electrifying the DMD chip and uploading the checkerboard pattern;
S4, introducing a second laser beam to enable the second laser beam to be incident along the direction perpendicular to the first laser beam;
S5, introducing a reflecting mirror at one side of the first laser beam, and adjusting the position and the direction of the reflecting mirror so that light spots formed on the reflecting mirror by the first laser beam and the second laser beam coincide, wherein at the moment, a reflection line of the second laser beam is incident on the DMD chip along a certain angle, and the incidence angle of the reflection line of the second laser beam on the DMD chip is recorded as theta;
s6, an observation screen is introduced between the DMD chip and the diaphragm I, and a chessboard image formed on the observation screen is observed;
S7, finely adjusting the position and the direction of the reflecting mirror so that the center of a chessboard pattern image formed on the observation screen is five uniform bright spots;
s8, measuring an incident angle theta of the reflection line of the second laser beam to the DMD chip at the moment;
And S9, calculating a micromirror deflection angle theta 0 of the DMD chip according to the incidence angle theta measured in the step S8, wherein theta 0 =0.5 theta.
Further, in the step S1, the center points of the DMD chip, the diaphragm I, the diaphragm II and the laser emitter are located on the same horizontal line.
Further, let the distance between the DMD chip and the diaphragm I be h1, the distance between the diaphragm I and the diaphragm II be h2, and the distance between the diaphragm II and the laser emitter be h3, then h1< h3< h2.
Further, the second laser beam is a green laser beam.
Further, the second laser beam is incident on the reflecting mirror from top to bottom along the vertical direction, and the reflecting mirror is positioned at the lower side of the first laser beam.
Further, the reflecting mirror is located between the DMD chip and the diaphragm I.
Further, the observation screen is parallel to the diaphragm I and the diaphragm II, the center points of the observation screen and the diaphragm I and the diaphragm II are positioned on the same straight line, and the observation screen is positioned between the DMD chip and the diaphragm I.
Further, in the step S7, five bright spots located at the center of the checkerboard image are determined according to the following method:
Firstly, determining a geometric center point of a chessboard picture image formed on the observation screen, taking the geometric center point as a center circle, wherein a bright spot is arranged at the center of the center circle, and the center circle passes through four bright spots which are nearest to the geometric center point and distributed in a cross shape, and the four bright spots are jointly formed into five bright spots positioned at the center of the chessboard picture image.
Further, in the step S7, when the position and the direction of the mirror are adjusted, the change of five bright spots in the center of the checkerboard image formed on the observation screen is observed at the same time, when the position and the direction of the mirror are not adjusted to the designated positions, the bright spot position with the maximum brightness is not located at the center of the center circle among the five bright spots in the center of the checkerboard image formed on the observation screen, and when the position and the direction of the mirror are adjusted to the designated positions, the bright spot with the maximum brightness is located at the center of the center circle.
The detecting device adopts the detecting method to detect the deflection angle of the micromirror of the DMD.
The method and the device for detecting the deflection angle of the micromirror of the DMD have the advantages of simple structure, easiness in implementation, accurate detection of the deflection angle of the micromirror of the DMD and simple operation process.
Detailed Description
The technical solutions of the embodiments of the present application will be clearly described below with reference to the drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which are obtained by a person skilled in the art based on the embodiments of the present application, fall within the scope of protection of the present application.
In the description of the present application, it is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments in accordance with the present application. For ease of description, the dimensions of the various features shown in the drawings are not drawn to actual scale. Techniques, methods, and apparatus known to one of ordinary skill in the relevant art may not be discussed in detail, but should be considered part of the specification where appropriate. In all examples shown and discussed herein, any specific values should be construed as merely illustrative, and not a limitation. Thus, other examples of the exemplary embodiments may have different values. It should be noted that like reference numerals and letters refer to like items in the following figures, and thus once an item is defined in one figure, no further discussion thereof is necessary in subsequent figures.
It should be noted that the terms "first," "second," and the like in the description and in the claims are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged, as appropriate, such that embodiments of the present application may be implemented in sequences other than those illustrated or described herein, and that the objects identified by "first," "second," etc. are generally of a type, and are not limited to the number of objects, such as the first object may be one or more. Furthermore, in the description and claims, "and/or" means at least one of the connected objects, and the character "/", generally means that the associated object is an "or" relationship.
It should be noted that, in the description of the present application, the terms "front, rear, upper, lower, left, right", "horizontal, vertical, horizontal", and "top, bottom", etc., generally refer to the orientation or positional relationship shown in the drawings, and merely for convenience of describing the present application and simplifying the description, and these orientation terms do not indicate or imply that the apparatus or elements to be referred to must have a specific orientation or be constructed and operated in a specific orientation, and thus should not be construed as limiting the scope of the present application, but rather the orientation terms "inside and outside" refer to the inside and outside with respect to the outline of each component itself.
It should be noted that, in the present application, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element. Furthermore, it should be noted that the scope of the methods and apparatus in the embodiments of the present application is not limited to performing the functions in the order shown or discussed, but may also include performing the functions in a substantially simultaneous manner or in an opposite order depending on the functions involved, e.g., the described methods may be performed in an order different from that described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.
As shown in fig. 1 to 4, a method for detecting a deflection angle of a micromirror of a DMD includes the steps of:
S1, sequentially placing a DMD chip 1, a diaphragm I2, a diaphragm II3 and a laser emitter 4 so that central points of the DMD chip and the diaphragm II are positioned on the same straight line;
S2, in the state that the power supply of the DMD chip 1 is disconnected, the position of the laser transmitter 4 is adjusted, so that a first laser beam 5 emitted by the laser transmitter passes through the diaphragm II3 and the diaphragm I2 at the same time, and is beaten in the central area of the DMD chip 1, the fixed angle of the DMD is adjusted, and the light source reflected by the DMD returns to the diaphragm I and the diaphragm II;
s3, electrifying the DMD chip 1 and uploading the checkerboard pattern 7;
S4, introducing a second laser beam 9 to make the second laser beam incident along the direction perpendicular to the first laser beam 5;
S5, introducing a reflecting mirror 6 at one side of the first laser beam 5, and adjusting the position and the direction of the reflecting mirror 6 so that light spots formed on the reflecting mirror 6 by the first laser beam 5 and the second laser beam 9 are basically overlapped, wherein at the moment, a reflection line of the second laser beam 9 is incident on the DMD chip 1 along a certain angle, and the incidence angle of the reflection line of the second laser beam 9 on the DMD chip 1 is marked as theta;
S6, an observation screen 8 is introduced between the DMD chip 1 and the diaphragm I2, and a chessboard pattern image formed on the observation screen 8 is observed;
S7, finely adjusting the position and the direction of the reflecting mirror 6 so that the center of a chessboard pattern image formed on the observation screen 8 is five uniform bright spots 10;
S8, measuring an incident angle theta of the reflected line of the second laser beam 9 to the DMD chip 1 at the moment;
And S9, calculating a micromirror deflection angle theta 0 of the DMD chip 1 according to the incidence angle theta measured in the step S8, wherein theta 0 =0.5 theta.
Further, the DMD chip 1, the diaphragm I2 and the diaphragm II3 are arranged in parallel.
Preferably, in the step S1, the DMD chip 1, the diaphragm I2, the diaphragm II3, and the laser emitter 4 may be sequentially arranged such that the central points thereof are located on the same horizontal line.
Further, let the distance between the DMD chip 1 and the diaphragm I2 be h1, the distance between the diaphragm I2 and the diaphragm II3 be h2, and the distance between the diaphragm II3 and the laser emitter 4 be h3, then h1< h3< h2.
Further, the ratio of h2/h3 is 3-1.5, and the ratio of h2/h1 is 5-12.
Preferably, the laser emitter 4 is a red laser, and the emitted light is red light, i.e. the first laser beam 5 is a red laser beam.
Further, in the step S2, the wavelength of the first laser beam 5 emitted by the laser emitter 4 is 680-740 nm.
Further, in the step S3, the checkerboard pattern 7 is a checkerboard pattern formed by black and white two-color checkers.
Further, in said step S3, uploading the checkerboard pattern 7 means marking said checkerboard pattern 7 on a fourier plane.
Further, in the step S4, the second laser beam 9 is a green laser beam.
Further, the second laser beam 9 is incident on the reflecting mirror 6 from top to bottom in the vertical direction, and the reflecting mirror 6 is located at the lower side of the first laser beam 5.
Further, the intersection point of the incident light rays of the second laser beam 9 and the first laser beam 5 is located between the DMD chip 1 and the diaphragm I2.
Further, in the step S5, the mirror 6 is located between the DMD chip 1 and the diaphragm I2.
Further, in the step S6, the viewing screen 8 is disposed parallel to the diaphragm I2 and the diaphragm II3, and the central points of the viewing screen 8 and the diaphragm I2 and the diaphragm II3 are located on the same straight line.
Further, the viewing screen 8 is located between the DMD chip 1 and the diaphragm I2.
Further, the viewing screen 8 is located between the incident ray of the second laser beam 9 and the diaphragm I2.
Further, in the step S7, five bright spots 10 located at the center of the checkerboard image are determined according to the following method:
Firstly, determining the geometric center point of a chessboard picture image formed on the observation screen 8, and then taking the geometric center point as a center circle 11, wherein the center circle 11 passes through four bright spots 10 which are closest to the geometric center point and are distributed in a cross shape. Meanwhile, a bright spot 10 is arranged at the center of the center circle 11, and the bright spot 10 and four bright spots 10 distributed in a cross shape on the center circle 11 form five bright spots 10 positioned at the center of the chessboard pattern image.
Further, in the step S7, when determining whether the position and the direction of the reflecting mirror 6 are adjusted to the specified positions and whether the checkerboard image formed on the viewing screen 8 meets the requirements, the specific method may be obtained by observing the appearance and the change of the bright spots 10 in the central area of the checkerboard image formed on the viewing screen 8, which comprises:
when the position and direction of the mirror 6 are not adjusted to the designated position, as shown in fig. 5, among the five bright spots 10 in the center of the checkerboard image formed on the observation screen 8, there is a bright spot 10 with brightness significantly higher than that of the four bright spots 10, and the position thereof is not at the center point of the checkerboard image formed on the observation screen 8, i.e., not at the center of the center circle 11, and when the position and direction of the mirror 6 are adjusted to the designated position, as shown in fig. 4, among the five bright spots 10 in the center of the checkerboard image formed on the observation screen 8, the bright spot 10 with brightness maximum is at the center point of the checkerboard image formed on the observation screen 8, i.e., at the center of the center circle 11, and the brightness of the bright spot 10 with brightness maximum is substantially equal to or slightly higher than that of the surrounding four bright spots 10, the bright spots with brightness uniformity is at the center of the five bright spots of the checkerboard image observed with naked eyes.
In addition, the application also provides a device for detecting the deflection angle of the micromirror of the DMD, and the device adopts the detection method to detect the deflection angle of the micromirror of the DMD.
Specifically, the micromirror deflection angle detection device of the DMD includes:
The detecting object DMD chip 1, a diaphragm I2, a diaphragm II3, a laser transmitter 4, a reflecting mirror 6 and an observation screen 8, wherein the laser transmitter 4 can transmit a first laser beam 5, the DMD chip 1 uploads a checkerboard pattern 7 and simultaneously introduces a second laser beam 9, a plurality of bright spots 10 are formed in a checkerboard image formed on the observation screen 8 through the second laser beam 9 and the first laser beam 5, and the deflection angle of the micro mirror of the DMD is detected through the change of the bright spots 10.
In summary, the method and the device for detecting the deflection angle of the micromirror of the DMD have the advantages of simple structure, easy realization, accurate detection of the deflection angle of the micromirror of the DMD and simple operation process.
The embodiments of the present application have been described above with reference to the accompanying drawings, in which the embodiments of the present application and features of the embodiments may be combined with each other without conflict, the present application is not limited to the above-described embodiments, which are merely illustrative, not restrictive, of the present application, and many forms may be made by those of ordinary skill in the art without departing from the spirit of the present application and the scope of the claims, which are protected by the present application.