Of the structural grating of grating sensor detect principle

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The structure of grating sensor is current, major diffractive grating product all duplicates by mother matrix and become, craft of mother matrix preparation basically has accurate machine score, but ionic bundle those who increase is holographic plate making, also have the measure of new science and technology such as photoetching of semiconductor of a few such as additionally. A typical diffractive grating includes base (it is optical material normally) , its surface passes the many parallel groove that treatment forms, and the reflection film such as some aluminous film forms exterior plating. The quality of groove and span are the crucial index of grating parameter. If assume the part of grating surface and orthogonality of its score direction is,curium flute profile, can derive grating is basic equation. Wavelengh is the A of beam of light of L and B, with grating normal (Grating Normal) becomes angle I incident to photograph adjacent groove. Diffractive light A’ and B’ and grating normal become angle D. Both optical path difference can express to be:   of A Sin I + A Sin D is become when the random that optical path difference is wavelengh L is times more integral, the overlay of A’ of beam of light and B’ can generate long interference:   of A(sin I + Sin D) = Mλ among them M is integer, namely diffractive progression. This is grating basic equation. If D and I are in the both sides of grating normal, m takes negative worth. Above has two groove only to assume simplify circumstance, and consider other and all groove integratedly, basic equation also won't change grating diffraction, can increase diffractive strength nevertheless the sensitivity of D of relatively diffractive horn. Portant;" />   pursues 1: Curium the illuminate of odd shade beam of light of parallel of actual grating equation goes to flute profile grating on grating, can produce different level second diffractive, if pursue,2 are shown. In class of “ grating diffraction second ” paragraphic lieutenant general is expatiatory. Illuminate of parallel much shade beam of light arrives on grating, can produce chromatic dispersion, in order to make different wavelengh all satisfies grating equation, if pursue,3 are shown. Portant;" />   pursues 2.

The   of grating equation Portant;" /> with parallel monochromatic contented light pursues 3.

Via the much shade of grating diffraction. Negative diffractive level shows only in the graph second. In major monochromator, incident slit and collimation lens decided grating is incident smooth direction, focusing lens and piece shot slit to determine a direction that shoots light. The wavelengh that accords with grating equation only can be passed through piece shoot slit, the light of the others is reached to absorb by scattering inside monochromator. Although rotate,grating can change I of an angle of incidence and diffractive horn D, but their poor value keeps constant from beginning to end, this depends on the geometry of monochromator is tectonic. Monochromator is more applicable and the following grating equation of the form: Mλ= 2 X A X Cosφ  of X Sin θ among them: φ= incident Guang Yan shoots the half of smooth included angleθ= grating is opposite the relation of these parameter and I of an angle of incidence and diffractive horn D can express the point of view of 0 class position the I = that it is  θ+ φ , d =θ–Class of diffraction of φ   grating second diffraction class second of “m” losing can decide by the grating equation of either form. In monochromator, I of an angle of incidence and diffractive horn D depend on of grating rotate. The article will be all in grating normal the angle set of anticlockwise direction is, the set of the clockwise is negative, if pursue,4 are shown. Half horn φ is from beginning to end. If D and I size are same way is opposite, grating angle and class second all be 0, beam of light is reflexed entirely. It is when grating angle when class second for (M=1) , conversely class second to lose (M=-1) . When | M | > 1 when, grating equation is in advanced second fall to also hold water, be like the λ2=λ1/2 when M = ±2, the λ3 = λ1/3 when M = ±3. λ2 and λ3 belong to 2 class and the wavelengh with 3 corresponding class namely, definition by the graph 3 give out. Actual application needs one class diffraction only normally, other and advanced wavelengh need below be divided by filter. The sensitivity of incident and spectral limits and detector decided to whether need to use anthology connect or end filter. Of Portant;" /> grating detect the principle is common the working principle of grating is a basis of stripe of the Mo Er on physics form a principle to have the job. Graph 4-9 is graph of its job principle. When the strain line on the strain line that should make indicate grating to go up and rear sight grating sets two grating rule into one angle, the strain line that can create two grating feet to go up necessarily is mutual across. Below the illuminate of illuminant, crossing overlaps as a result of black strain line inside near zonule, shading area is the consequently smallest, the effect that block light is the weakest, smooth accumulation action makes this area appears bright belt. Contrary, be apart from the region with more remote crossing, because of two grating feet the jackknife part of opaque black strain line becomes less and less, opaque area area greatens gradually, namely shading area greatens gradually, make strain of the effect that block light strong, only less light can pass through grating through this area, make this area appears shady area. These and grating strain line are almost perpendicular, the light that alternate with appears, shady area is Mo Er stripe. Mo Er stripe has the following quality: (When 1) should use grating of illuminate of parallel beam of light, through Mo Er the luminous intensity of stripe distributings approximate at cosine function. (If 2) indicates the breadth of Mo Er stripe with W, d states the bar of grating is apart from, θ expresses the included angle of strain line of two grating feet, criterion the geometrical relation between them is W=d / Sin (4—15) when horn very hour, take Sin≈ , type can be written into W=d / θ approximately on (4—16) if take D=0.

01mm, θ=0.

01rad, criterion by on type can get W=1mm. This explains, need not complex optical system and electric subsystem, use smooth interference appearance, can be apart from the bar of grating changeover becomes enlarge the width of the Mo Er stripe of 100 times. Action of this kind of enlarge is a of grating important characteristic. (3) because Mo Er stripe is by a certain number of collective interference forms grating strain line, so the bar between specific to grating strain line is apart from Mo Er stripe the error has average effect, can eliminate grating bar to be apart from the effect that inhomogenous place causes. (The shift of stripe of 4) Mo Er and the opposite shift between two grating feet are opposite should. Two grating feet is relatively mobile a bar is apart from D, mo Er stripe moves accordingly W of width of stripe of a Mo Er, its direction and the direction with two grating relatively mobile feet are perpendicular, and when be being changed relative to mobile direction when two grating feet, the direction with Mo Er mobile stripe also is changed subsequently. Basis of principle of job of graph 4-9 grating the character of afore-mentioned Mo Er stripe, if we are in,Mo Er opens 4 viewport mouth A on the direction with mobile stripe, b, c, d, and make two two-phase are apart from these 4 windows 1 / width of 4 Mo Er stripe, namely W / 4. By afore-mentioned discussion knowable, when two grating feet is relatively mobile, mo Er stripe moves subsequently, observe window A from 4, b, c, d can get 4 are in phasic go up ordinal lead or lag (depend on the direction with two grating relatively mobile feet) 4 cycle of 1 / (namely of π / 2) change at the luminous intensity of cosine function approximately process, with express, see graph 4-9(c) . If use photosensitive component to detect, photosensitive component changes the luminous intensity change that passes through viewport mouth into corresponding voltage signal, set for. According to signal of these 4 voltage, can detect the opposite shift that gives grating rule. 1. Of  displacement size those who because the shift of Mo Er stripe and the opposite shift between two grating feet are to answer relatively,detect, reason is passed detect the metabolic circumstance of signal of these 4 voltage, can detect accordingly an opposite shift between two grating feet. Every change a cycle, namely Mo Er stripe every change a cycle, show two grating feet moved relatively the distance that a bar is apart from; If the opposite shift between two grating feet is less than a bar to be apart from, because be cosine function, the value of reason foundation also can be calculated the space that gives its to move relatively. Of direction of 2  displacement detect in graph 4-9(a) , if rear sight grating is secured,do not move, square of demonstrative grating edge to shift, at this moment, mo Er stripe moves accordingly along the direction that be down, pass through viewport mouth A and B, the process of luminous intensity change that photosensitive component detects and the corresponding voltage signal that reach output and place of the 4-10(a) that be like a graph are shown, below this kind of circumstance, of lag phasic for / 2; Conversely, if rear sight grating is secured,do not move, demonstrative grating moves along negative direction, at this moment, mo Er stripe is corresponding ground edge up direction is mobile, pass through viewport mouth A and B, the process of luminous intensity change that photosensitive component detects and the corresponding voltage signal that reach output and place of the 4-10(b) that be like a graph are shown, below this kind of circumstance, of lead phasic for / 2. Accordingly, basis and two signal mutual the lead between and lag concern, can decide the relatively mobile way between two grating feet truly. The displacement of graph 4-10 grating detects block diagram of circuitry of information processing of grating of 4-11 of principle plan plan of 3  speed detect the floating rate that the relatively floating rate of two grating feet is deciding Mo Er stripe, deciding to pass through the frequency of the luminous intensity of viewport mouth namely, accordingly, can conclude through detected metabolic frequency the relatively floating rate that gives two grating rule. CNC Milling CNC Machining