CN100592044C - Birefringence measurement of large-format samples - Google Patents

Abstract

The disclosure is directed to systems and methods for precisely measuring birefringence properties of large-format samples of optical elements. A gantry-like configuration is employed for precise movement of birefringence measurement system components relative to the sample. There is also provided an effective large-format sample holder that adequately supports the sample to prevent induced birefringence therein while still presenting a large area of the sample to the unhindered passage of light.

Description

The double refractive measurement of large-scale sample

Technical field

The application relates to the measuring method of the birefringence of optical element, relates generally to large-scale element, for example is used for the large-sized sheet material of LCD (LCD).

Background technology

A lot of important optical materials all show birefringence.Birefringence means that the light of different linear polarizations passes material with different speed.These different polarization great majority often are regarded as two orthogonal components of polarized light.Birefringence is the intrinsic property of a lot of optical materials, and also may cause by the applied external force that is applied on the material.

Delay (retardation) or retardance (retardance) are representing birefringence along the combined influence that path produced of light beam by sample.If incident light is a linear polarization, two orthogonal components of polarized light will penetrate from sample with different phase places, and this is called delay.The base unit that postpones is a length, for example nanometer (nm).Under the frequent situation, for convenient, postpone also to use phase angular unit (ripple, radian, the perhaps number of degrees) expression, it is proportional divided by light wavelength (nm) with delay (nm)." on average " birefringence of a sample sometimes can be according to being calculated by the ratio of the measured retardation of sample thickness.

Often, term " birefringence " can same term " delay " mutual alternative use, and equivalent in meaning.Like this, unless stated otherwise, these terms also can exchange use below.

Aforesaid two orthogonal polarized components and optical material two are orthogonal to be called as the spool parallel of fast axle and slow axis.Fast axle is with the parallel axle of polarized light component that passes through sample fast.Therefore, need measure the relative angle orientation of retardation and the fast axle of sample (or slow axis) along the complete description of the delay of given optical path a sample.

Demand to precise measurement of birefringence properties has become more and more important in some technology are used.For example, for the employed optical element of high precision instrument in semiconductor and other industry, the accurate mensuration of its linear birefrigence is very important.

In addition, some application requirements carry out the measurement of delay property on the surface of whole massive optics or sample.For example, a manufacturer may wish on whole expanse of material zone retardance to be detected, thus drop into more spend panel is processed into a plurality of unit before (from the angle of birefringence) determine whether material satisfactory.

The detection of the birefringence of these large-scale samples has been brought sample and has been applied to the problem of accurate operation of the instrument of these detections.For example, these large-scale samples with respect to the birefringence instrument do relative mobile be infeasible.Substitute, the optical element of system's necessity can move with respect to static sample.The problem that this system produces is that the element that need guarantee birefringence measurement system all moves each other and with respect to sample accurately, thereby in the process that the large-scale sample of leap moves, no matter how much system element quantity that needs to move is, can both provide the uniform data of birefringence accurately.

As mentioned above, the applied external force that acts on optical element or the sample can cause birefringence.For example, when a sample is bent or is subjected to other pressure fixedly the time, this acting force will produce.Owing to the gravity reason, the quality of sample can produce certain birefringence, especially in the main quality of sample under the situation of vertical direction orientation.Like this, the accurate detection of the inherent birefringence of large-scale sample just requires the optical element of being correlated with or sample can not causing birefringent mode fix in sample or to support, and these cause the error-detecting that birefringent mode will cause inherent birefringence.Specifically, this support requires a flat sample in one plane to be supported substantially equably there not being pressure to be applied under the situation on the sample.

Except needs in one plane support the sample fully, the mechanical hook-up that supports sample must allow to allow light beam pass through sample under the situation of interfering beam not.Light beam is a critical aspects that accurately carries out birefringence in the clear by sample and enter the relevant detection assembly.What wish most usually in addition, is the birefringence of test sample on each position that the tight spacing on the whole sample zone is opened.Therefore, the design of large-scale sample fixer is necessary for uncrossed birefringence light beam required big sample area is provided, simultaneously for preventing that causing birefringence by acting force gives sample enough supports, at this seeking balance between the two.

Certainly, the simplicity of manufacturing and cost, and the delivery and the assembling that comprise a birefringence measurement system of large-scale sample fixer also are the aspects that design the time needs emphasis to consider.

Summary of the invention

The present invention relates to accurately to detect the system and method for the birefringence of massive optics sample.

In a preferred embodiment, the structure of a gantry-like is used to accurately the moving along Y direction that the birefringence measurement system element is done with respect to sample.This element is to be used for accurately moving of X-direction.Accordingly, the whole zone of sample is passed through by the birefringence element.

An effective large-scale sample fixer also is provided, and it can be for uncrossed birefringence light beam provides large-area sample, provides enough support to prevent to cause therein birefringence to sample simultaneously.

Description of drawings

Fig. 1 is the diagram of an embodiment, and it has shown a preferred arrangement according to the optical element of the birefringence measurement system that is used to detect massive optics of the present invention.

Fig. 2 is the block diagram of the Signal Processing Element in Fig. 1 institute descriptive system.

Fig. 3 has described a preferred equipment, is used for supporting some element of a massive optics (sample) and fixing and mobile Fig. 1 and 2 system, and these elements are used for detecting birefringence on each position in whole sample zone.

Figure 4 and 5 are local amplification views of the sample fixer part of equipment shown in Figure 3.

Fig. 6 is the detailed cross sectional view of an amplification, has shown another embodiment of the part of the sample fixer among the present invention.

Embodiment

According to Fig. 1 and Fig. 2, the embodiment of a birefringence measurement system has been described.Native system uses the low-level linear birefringence in two photoelasticity modulator (PEM) device detection optical elements.Present embodiment can be measured birefringent size and angular orientation and have signal processing apparatus, the data gathering system of specific design and be used for algorithm with very high accuracy detection low-level linear birefringence.

As shown in Figure 1, two photoelasticity modulators (PEM) of present embodiment device 20 comprises two modules.Source module comprises the polarizer 24 of light source 22, miter angle orientation and the PEM 26 of 0 degree angular orientation.Light source 22 is polarization helium-neon lasers, and it can produce wavelength is 632.8 nanometers, the about 1 millimeter light beam of spot definition (diameter).

Detection module comprises the 2nd PEM 28, and the modulating frequency of its setting is different with the modulating frequency of a PEM 26.The 2nd PEM 28 is orientated with miter angle.Detection module also comprises the analyzer 30 and a detecting device 32 at one 0 degree angle.

Be the sample fixer 34 (shown in Figure 1) that is used for supporting optical component or sample 36 between source module and detection module, will describe in detail below.The arrow of vertically arranging among Fig. 1 represents to enter through sample 36 (also can be other optical element the system) from the light beam that light source 22 is launched the path of detecting device 32.

Still with reference to figure 1, each all is Ge Lan-Tang Pusheng type for the polarizer 24 and analyzer 30.Use si-photodiode detector 32 in the present embodiment.PEM 26 and 28 is the form that has the bar-shaped fused silica glass of two sensors.Sensor uses the flexible adhesion material to be connected on the fused quartz optical element.For reducing the birefringence that optical element causes, only there is sensor to be contained on the housing of PEM.Two PEM 26 and 28 nominal resonant frequencies are respectively 50 and 55Hz.

According to Fig. 2, the electronic signal that produces on detecting device 32 all comprises " exchanging (AC) " and " direct current (DC) " signal, and through different processing.AC signal is applied on two lock-in amplifiers 40 and 42.The 1F signal that each lock-in amplifier (1F) under the modulating frequency of PEM basis all shows detecting device and provided.In a preferred embodiment, the lock-in amplifier model specification is EG﹠amp; 7265 types of G.

Direct current signal is recorded after detector signal is through analogue-to-digital converters 44 and low pass electronic filter 46.Direct current signal represents to arrive the average intensity of detecting device 32.Postpone to be provided with record direct current and AC signal down at different PEM.

The theoretical analysis of the detection institute foundation of 36 birefringences of sample in the present embodiment is based on the Mueller matrix analysis, and in conjunction with the signal Processing of light intensity, so that the data of birefringent size of representative and angular orientation to be provided.

With reference to figure 3, the details of large-scale birefringence measurement system of the present invention is described at this.Birefringence measurement system comprises a housing 49 that has top 51.Sample 36 is placed on the case top 51 by fixator 34.Sample 36 is large-scale samples, for example may be that thickness is approximately 0.5 millimeter 1250 millimeters * 1100 millimeters LCD (LCD) sheet material.In Fig. 3, sample thickness is exaggerated greatly.

It is static that sample 36 keeps under the support of fixator 34.In a preferred embodiment, fixator comprises the line 37 of a plurality of isolated tensions between two brace summer assemblies 39,41 of stretching tight and is positioned at the beam assembly on the one side on the opening 63 of housing upper surface.The detail section of fixator will be described below more fully.

Light path " P " is between source module 50 and detection module 52 (Fig. 3).Source module 50 is the complete module that above-mentioned a plurality of elements are formed, and detection module 52 also is the complete module that a plurality of element of above-mentioned this module of composition is formed.

Source module 50 is fixed on the upper beam member 56, and upper beam member 56 is along the direction of X-axis, and promptly the Width of sample fixer 34 (being sample 36 here) extends.This upper beam member is supported by gantry columns 58 at its opposite end.Beam parts 56 are fixed, and move with post on Y direction.Each post extends by being positioned near the slit groove 60 that forms case top 51 lateral edges.

Detection module 52 is fixed on the lower beam member 62, and lower beam member 62 is positioned at below the sample fixer 34, and is connected between the gantry columns 58 (moving) thereupon.

Groove 60 allows gantry columns 58 to move to cross on the length direction of sample 36 in Y direction.For this reason, the lower end of gantry columns is fixed on the actuator 64 of a pair of coupling (only can see one at Fig. 3), as sufficiently long ball-screw linear actuators, so that cross over the length of sample.The motor of suitable position transducer and processor control also is provided, guaranteeing the same moved further of gantry columns, thereby on Y direction, obtains source module and the consistent of detection module moves.

Upper beam member 56 and lower beam member 62 all are set and are used to transmit the servo motion control module 66 that is connected with module 50,52.This unit 66 comprises that suitable scrambler and relevant motion controller can both consistently move at X-direction upper module 50,52 guaranteeing.

Should be appreciated that repeatably birefringence has been guaranteed in the accurate control of aforesaid source module and detection module motion on the X-Y axle.For example, this motion guarantees that light path " P " will can not change with respect to detector aperture, otherwise this variation may cause birefringence result's systematic error.

According to Fig. 3-5, fixator 34 comprises a fixing beam assembly 39, and it comprises a flat substrate 70 that is connected to housing 49 tops 51.Substrate 70 is connected near 51 edges, top.Some dividing plate 72 (see figure 3)s are fixed on the upper surface of substrate 70, to extend therefrom and to support the anchor slab 74 that is positioned at substrate 70 tops.Anchor slab 74 general xsects are L shaped, have a flat leg 76 and a flange that projects upwards 78.The bottom of leg 76 is fixed on the top of dividing plate 72.The top 77 of flange 78 is roundings.

The end of every line 37 above-mentioned all is fixed on the anchor slab 74.Concrete, the end of line (having only the end of a single line to show at Figure 4 and 5) is by the hole on the leg 76 and pass the columned stop sleeve 82 of a hollow.Thereby sleeve 82 is curled and makes sleeve fix online end, and because the diameter of sleeve greater than the diameter in hole 80, line 37 can be closed on the sleeve tension of the leg 76 of anchor slab 74, thus with the terminal grappling of line.Line 37 is pulled out by pulling force, by the edge 77 of rounding, arrives another above-mentioned beam assembly 41.

In a preferred embodiment, line 37 is the stainless steel cotton rope, can apply or not apply low-friction coating, for example Teflon.The cotton rope of nylon coated and various other materials also may be used as this line.

Preferably, the diameter of line 37 will be selected enough for a short time (for example 1 or 2 millimeter), and (and this is with stray light beam passage " P ", as shown in Figure 3) so that the amount of space that passes window 63 that is occupied by these lines is reduced to minimum.Identical distance is all selected between the material of line and the every line, like this, weight per sample, sufficient tension force is added on the every line (below with more detailed description) and places in one plane under without any the situation of bending stress to guarantee sample, if and the permission sample sink, just may produce this stress.

Big (elasticity that depends on unit weight and sample) is wanted at interval in the fixator between the solid wire 37 as far as possible, and like this, as described in just now, it is minimum that the space of passing window 63 that line is occupied becomes.Interval between the line may be from several millimeters to several centimetres, and as previously mentioned, it depends on the physical property of sample.Preferably, keep a minimum interval (for example 5 millimeters), guaranteeing between every line keeping enough big gap, thereby the pollutant (glass particle, coating bits etc.) that allows to disturb light beam can be not online between gathering.

Different with the thicker relatively sample of selecting for purpose of description 36 shown in Figure 1, in Fig. 4 and Fig. 5, the thickness of the sample 36 that is drawn has reflected the relatively thin essence of the sample of at least some types that are used for current fixator 34, the LCD of 0.5 millimeters thick for example above-mentioned (LCD) material.

As shown in Figure 5, the other end of line 37 is connected on the stretching beam assembly 41, and it produces the also pulling force of retention wire.Stretching beam assembly 41 comprises a flat substrate 90 that is connected to housing 49 tops 51.Substrate 90 is connected near the edge of opening 63 at top 51.A plurality of cylindric spacers 92 are fixed on the upper surface of substrate 90 according to isolated spacing, to extend therefrom and the anchor slab 94 of supporting substrate top.Anchor slab 94 is roughly L shaped, the flange 98 that has a flat leg 96 and project upwards.The downside of leg 96 is fixed on spacer 92 tops.The uppermost margin 97 of flange 98 is roundings.

The edge 97 that the end of every line 37 is crossed rounding is stretched and is connected on the leg 96 of anchor slab 94, and its connected mode makes the end of line be anchored, and allows the pulling force effect simultaneously on line.A mode that forms this connection is to use traditional terminal joint, bolt end fitting 100 for example shown in Figure 5.The end of bolt end fitting 100 capture line in an external thread sleeve 102, this screw shell 102 is screwed into hex bolts 104.The screw rod 106 of bolt passes the hole of leg 96 and passes through the lock nut 108 of a supporting leg end portion.In case in enough pulling force effects online 37, nut is tauted.

Beam assembly 39,41 is set and arranges, thereby the topmost that makes rounding end 77,97 separately is on the common plane, the line of straining between these assemblies like this 37 will keep sample levels, do not have bending stress, thereby guarantee that the light beam that passes sample can not influenced by the birefringence in the sample that this bending caused.

Should be appreciated that in the process of making current fixator, be the accurate level that keeps sample that sample stage supports, the thing that need do only is to guarantee beam assembly top 77,97 on a common plane, and acts on appropriate pulling force on line.This can with for example make have large-scale, the rigidity that is used for openings machined that light passes through, the complicacy of accurate horizontal support supporting plate compares.

Expection, as the substitute of tight line 37, can use other parts thin, that can extend.For example, as shown in Figure 5, the cylindrical rods 110 of minor diameter can be crossed over window 63.In such an embodiment, cylindrical rods can be rotated to be installed on the bearing 112, and picture is discussed above, is installed between the anchor log 74,94 at window 63 opposite side edge places.Rotatable bar makes the contact between sample and the fixator be reduced to minimum, and a method that makes sample roll on and roll down fixator easily is provided simultaneously.

Can expect that also sample fixer can be built in following a kind of mode, it allows relatively fast the pulling force effect to be discharged pulling force on line and accordingly relatively apace, thereby makes things convenient for the assembly and disassembly of fixator, to satisfy the needs of delivery.About in this respect an embodiment as shown in Figure 6.

Fig. 6 has described a kind of method of fixed support line 37, thus make a whole set of line can by regulate one movably drawing plate 190 strain and loosen, the end of line is fixed on this drawing plate.In this embodiment, beam assembly 139 comprise one with top 51 in the substrate 170 that closely links to each other of the edge of opening 63.This substrate can connect by coupling bolt 171, and for example, it can be removed so that whole assembly 139 separates with housing 45.At this on the one hand, the same with the essentially identical beam assembly of beam assembly fixing among Fig. 4 or the assembly in the image pattern 5 41 beam assembly can be applied in the other end of the opposite edges of window 63 with static line.

A plurality of space bars 172 are fixed on the upper surface of substrate 170, extend the also anchor slab 174 of supporting substrate 170 tops therefrom.Anchor slab 174 is roughly L shaped, has a flat leg 176, and leg 176 extends internally and crosses space bar 172, ends at the flange 178 that projects upwards.

The upper limb 177 of flange 178 is roundings.The end of above mentioned every line 37 passes leg 176 hole 180 on the outshot inwards, passes the hole in the centre of the rigidity drawing plate 190 between the part that case top 51 and anchor slab 174 extend internally subsequently.The end of line is captured by stop sleeve 182, and just as the sleeve among the embodiment noted earlier 82, it curls sleeve is fixed to the end of line.Similar, because the diameter of sleeve surpasses the diameter in hole on the drawing plate, therefore line 37 is closed on the sleeve tension of plate 190 downsides.

Expection, as the groove as shown in 179 among Fig. 6, can locate to form and receive line 37 on the top 177 (and edge 77,97 of discussing in the early time) of beam assembly, thereby reach also correct spacing between the retention wire according to size.

Some isolated arm shape bolts 192 that are used for the pulling force adjustment pass the through hole on the drawing plate and are screwed into substrate 170.Should be appreciated that, these bolts 192 tighten and unscrew with correspondingly increase and reduce the pulling force on wired 37.Under the situation that also to be understandable, online end captured by single rigid rod parts or similar parts as single group, any one in the clamping mechanical device of a plurality of snap-out release all can be used for tension and loosens this group line.In addition, any one in a plurality of mechanical hook-ups can both be used for fastening anchor slab when allowing the drawing plate motion.For example, bolt 192 and web member be can not use, but housing or substrate 170 are connected to by a hinge, long limit by plate 190.A handle can be connected on the plate, with around the hinge movable plate, strains simultaneously or loosens all lines.Nail or blocking device are fastening with plate with the position of online tension in can being included in.

Although the present invention preferably describes with the embodiment that substitutes, it should be noted that the spirit and scope of the present invention are not limited to these embodiment, but extend in various improved forms and the equivalent.For example, although discuss above the sample fixer in the birefringence measurement system, should be appreciated that this sample stage can be applicable to any different optical equipment or the application of system.

In addition, although concentrate on large-scale sample here, it should be noted that the fixator among the present invention also goes for the sample of virtually any size, comprises very little sample, and does not need fixator is done improvement.

Claims (15)

1. One kind at lead beam by supporting the method for sample in the optical devices of sample, this method may further comprise the steps:

   At a plurality of isolated long these samples of parts upper support, these a plurality of long arrangements of components become to be defined for the plane of supporting this sample, and these long parts are not intersected each other.
2. 2. the method for claim 1 is characterized in that, described long parts are line, and described method comprises the step of these a plurality of lines of tensioning.
3. 3. the method for claim 1 is characterized in that, comprises the step of passing through the different piece of sample with respect to the element of sample mobile optical device with lead beam.
4. 4. optical element bracing or strutting arrangement comprises:

   Two isolated anchoring members; And

   A plurality of long parts are fixed between the anchoring members, and these long parts are spaced from each other and are arranged to be defined for the plane of supporting sample and these long parts are not intersected each other, are used to optical element to provide support.
5. 5. device as claimed in claim 4 is characterized in that, described long parts are line, the tensioning between anchoring members of described line.
6. 6. device as claimed in claim 5 comprises tensioning system, is used for optionally described line being discharged and applying tension force.
7. 7. device as claimed in claim 6, wherein said tensioning system comprises clamp device, is used for optionally discharging simultaneously and applying tension force institute is wired.
8. 8. device as claimed in claim 4, wherein said long parts are cylindrical rods, each in these a plurality of cylindrical rods is fixed between the anchoring members and is installed between anchoring members rotates.
9. 9. measure birefringent method for one kind on the zone of large-scale sample, wherein, birefringent measurement is needed light source and detecting device, this method may further comprise the steps:

   Make it stable at Uncrossed a plurality of isolated long parts upper support sample each other; And

   With respect to mobile simultaneously light source of sample and detecting device and pass through the zone of this sample.
10. 10. method as claimed in claim 9 is characterized in that, comprising provides the step of line as long parts and the described line of tensioning.
11. 11. method as claimed in claim 10 is characterized in that, comprises tensioning simultaneously or loosens the step of many whole lines.
12. 12. method as claimed in claim 9, wherein said long parts are for being fixed between the anchoring members and rotatable cylindrical rods between anchoring members.
13. 13. method as claimed in claim 9 comprises and arranges that these long parts make its parallel step.
14. 14. method as claimed in claim 9 is included in the step that supports this sample in the plane of basic horizontal.
15. 15. method as claimed in claim 9 is included in the step of discontiguous each other a plurality of long these samples of parts upper support.

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