CN103837096A - Device and method for detecting surface shape error of flat optical element - Google Patents

Abstract

The invention relates to a device and a method for detecting surface shape errors of a flat optical element. The device comprises an optical element support, matching liquid and a matching liquid containing tank. The device can eliminate the interference of the reflected light of the back optical surface of the flat optical element on the detection of the surface shape error of the front optical surface when the flat optical element is measured by using the vertical interferometer, thereby detecting the reliable distribution of the surface shape error of the optical surface. The device and the method can effectively solve the problem that the common vertical interferometer can not detect the surface shape error of the flat optical element, have simple principle and lower manufacturing and using cost, and can complete the detection of the surface shape error of the flat optical element under the condition of not changing the structure of the original vertical interferometer. The non-contact method is used for detecting the surface shape error of the optical element, and has no damage to the optical element and no clamping stress. The surface shape error of the optical element is detected, and the optical element is cleaned by tap water in the process without special cleaning solvent and method.

Description

A kind of device and method for detection of planar optics element face shape error

Technical field

The present invention relates to the technical field that optical element detects, be specifically related to a kind of device and method for detection of planar optics element face shape error.

Background technology

The face shape error of optical element generally adopts interferometer to measure by interferometric method.But, when High Accuracy Flat optical element detects, former and later two optical surfaces all can reflection ray, and reflection ray Jun Nengyanyuan road is reflected back, itself and reference wavefront all can be interfered and on image detector, be formed interference fringe, after, the reflection ray of optical surface produces and disturbs the detection of front optical surface, makes effectively to detect the face shape error of front optical surface.Take the typical optical glass of refractive index n=1.55 as example, under atmospheric environment, through calculating, when light vertical incidence, the light reflection energy of uncoated former and later two optical surfaces of optical glass is respectively 4% and 3.67%.After, the energy of reflection light of optical surface and front optical surface is very approaching, it is larger that the reflected light of rear optical surface detects interference to the face shape error of front optical surface, effective interference fringe cannot be formed, thereby the face shape error on detected optics surface cannot be effectively detected.

Summary of the invention

In order to overcome the problem of existing detection technique, a kind of method is exactly the reflectivity of optical surface after reduction planar optics element.Object of the present invention is to provide a kind of can realize the device and method that reduces rear optical surface reflectivity, to obtain the effective detection to planar optics element Optical Surface.

The technical solution used in the present invention is: a kind of device for detection of planar optics element face shape error, comprise: optical element support, coupling liquid and coupling liquid containing tank, described optical element support is for holding optical components, and can be by optical element stentplacement on coupling liquid containing tank, coupling liquid is to approach or on all four clear solution with the Refractive Index of Material of the planar optics element that will detect, and coupling liquid must not cause chemical damage to detected optics element.

Further, coupling liquid is benzene, ether, glycerine or terebinthina, coupling liquid can be also solution, for example sodium chloride solution, 20 degrees Celsius time, the refractive index of sodium chloride solution can, according to the concentration of sodium chloride solution from 1.33 allotments to 1.6, cover the ranges of indices of refraction of most of optical material.

Further, coupling liquid containing tank inside has delustred coating or matt structure, light can not produce strong mirror-reflection after injecting, for example can adopt the additional blacking of frosted to process to eliminate mirror-reflection, can adopt Catadioptric system structure to refract light into incoherent region yet.

Further, this coupling solution containing tank exists one to add liquid mouth for what add coupling solution, this adds liquid mouth upper maintaining an equal level with the upper edge of mate liquid containing tank along height or upper along highly a little less than coupling liquid containing tank.

A kind of method that adopts said apparatus to detect planar optics element face shape error is provided in addition, and concrete steps are as follows:

Step (1): inquire about or test the refractive index of the optical material that this optical element adopts, select and allocate coupling liquid;

Step (2): will mate liquid and inject in matching fluid containing tank; The detected optics surface of the detected planar optics element of wiped clean, by clamped detected member optical element optical element stentplacement in coupling liquid containing tank on, before detected optics element, optical surface upward, for optical surface to be detected, rear optical surface submerges in matching fluid, front optical surface must not submerge in coupling liquid, and must not be by matching fluid body pollution; As improperly in liquid level can suitably add or take out coupling liquid by adding liquid mouth;

Step (3): the device that places optical element and coupling liquid in step (2) is positioned on vertical interferometer work support, and static a period of time, until liquid level stabilizing;

Step (4): according to the routine operation step of common vertical interferometer, detect and read the face graphic data of optical element;

Step (5): take off coupling liquid containing tank, and take off successively optical element and optical element support, pour out coupling liquid, rinse optical element and coupling liquid containing tank drying with tap water.

Principle of the present invention is:

According to Fresnel principle, the reflectivity R at dielectric surface when light vertical incidence can calculate by following formula:

$R={\left(\frac{n_a-n_b}{n_a+n_b}\right)}^2$

Wherein: n _a, n _bbe respectively the medium refraction index of both sides, interface from above formula, work as n _a≈ n _btime, R ≈ 0, now reflected light almost disappears.And transmissivity R can calculate by following formula (2):

$R^{\text{'}}=1-R=1-{\left(\frac{n_a-n_b}{n_a+n_b}\right)}^2$

Can be similar to think and the refractive index of common most of optical glass according to its scope of different materials between 1.3 to 1.7.If rear optical surface is immersed in the refractive index liquid approaching or consistent with its Refractive Index of Material, after can greatly reducing or eliminate, the reflection ray of optical surface, can effectively reduce or get rid of interference.

The invention has the advantages that:

1. this device and method can effectively solve common vertical interferometer and cannot detect the problem of planar optics element face shape error.

2. simple, the manufacture of this device and method principle and use cost are lower, in the situation that not changing former vertical interferometer structure, can complete the detection to planar optics element face shape error.

3. this device and method adopts non-contacting mode to detect optical component surface shape error, to optical element not damaged, without nip stress.

4. this device and method detects optical component surface shape error, in process, the cleaning of optical element is cleaned with tap water, does not need special cleaning solvent and method.

Accompanying drawing explanation

Fig. 1 is the device schematic diagram of a kind of detection planar optics element with smooth lower curtate of the present invention;

Fig. 2 is the device schematic diagram of a kind of detection planar optics element with undaform lower curtate of the present invention;

Fig. 3 is the device schematic diagram of a kind of detection planar optics element with inclined-plane lower curtate of the present invention;

Fig. 4 is a kind of device schematic diagram with the detection planar optics element that adds liquid mouth of the present invention;

Fig. 5 is the vertical view of the optical element clamping device of a kind of brace summer intersection of the present invention;

Fig. 6 is the cut-open view of the optical element clamping device of a kind of brace summer intersection of the present invention;

Fig. 7 is the vertical view of the Uncrossed optical element clamping device of a kind of brace summer of the present invention;

Fig. 8 is the cut-open view of the Uncrossed optical element clamping device of a kind of brace summer of the present invention;

Fig. 9 light is at the propagation schematic diagram of dielectric surface;

Figure 10 planar optics element is placed the propagation schematic diagram of light in air;

The propagation schematic diagram of light when Figure 11 planar optics element lower surface submerges liquid.

In figure, the implication of Reference numeral is: 101 is detected planar optics element; 102 is optical element support; 103 is coupling liquid; 104 is coupling liquid containing tank; 105 is interferometer measurement head; 106 is interferometer bracing frame; 107 incident lights that send for measuring head; 108 for adding liquid mouth; 109 is dropper; 110 is the incident light on light incident sheet glass; 111 is primary event light; 112 is secondary transmitted light; 113 is a transmitted light; 114 is secondary reflection light; 115 is coupling liquid level of solution; 116 incide two kinds of interfacial incident lights of different medium for light; 117 incide two kinds of interfacial reflected light of different medium for light; 118 incide two kinds of interfacial transmitted lights of different medium for light; 119 incide the interphase of two kinds of different mediums for light; 120 incide two kinds of interfacial side media of different medium for light; 121 light incide two kinds of interfacial opposite side media of different medium; 122 is the upper surface of sheet glass; 123 is sheet glass; 124 is the lower surface of sheet glass; 125 is the transmitted light of light incident sheet glass.

Embodiment

Further illustrate the present invention below in conjunction with accompanying drawing and specific embodiment.

According to Fresnel principle, as shown in Figure 1, the reflectivity R at interface 119 when incident ray 116 vertical incidence can calculate by following formula:

$R={\left(\frac{n_a-n_b}{n_a+n_b}\right)}^2$

Wherein: n _afor the refractive index of interface 119 upside media 120, n _bfor the refractive index of interface 119 downside media 121, in order to be easier to distinguish each reflected light and transmitted light, in figure, each light is separately drawn in the diagram, and in reality, all light all returns and broadcasts on same straight line.From above formula, work as n _a≈ n _btime, R ≈ 0, now reflected light 116 almost disappears.And the transmissivity R of transmitted light 118 can calculate by following formula:

$R^{\text{'}}=1-R=1-{\left(\frac{n_a-n_b}{n_a+n_b}\right)}^2$

Under normal temperature and pressure, can be similar to and think that air refraction equals 1; And the refractive index of common most of optical glass according to its scope of different materials between 1.3 to 1.7.Now the fused quartz planar optics element take refractive index as 1.55 is further analyzed as example.

In Fig. 2, planar optics element 123 upper and lower surface media 120 are air, in order to be easier to distinguish each reflected light and transmitted light, in figure, each light is separately drawn in the diagram, in reality, all light all returns and broadcasts on same straight line, high order reflection and transmission light a little less than, ignore at this.When incident light 110 vertical incidence planar optics element, a part of light reflects at planar optics element upper surface 122, forms primary event light 111; The transmission of another part light enters after planar optics glass 123, forms one time transmitted light 113; When one time transmitted light 113 incides planar optics element lower surface 124, a part of light can reflect at interface 124, forms secondary reflection light 114, and another part light is gone out from 124 transmissions of planar optics element lower surface.Primary event light 111 energy of upper surface 122 are calculated as according to above formula:

$R_1={\left(\frac{n_0-n_1}{n_0+n_1}\right)}^2\×100\%\≈4\%$

The ratio that the energy of the secondary reflection light 114 of lower surface 124 accounts for initial total beam energy may be calculated:

$R_2={(1-R_1)\×\left(\frac{n_0-n_1}{n_0+n_1}\right)}^2\×100\%\≈3.84\%$

The ratio that the energy of the secondary transmitted light 112 of upper surface 122 accounts for initial total beam energy may be calculated:

$R_3=R_2\×{\left(\frac{n_0-n_1}{n_0+n_1}\right)}^2\×100\%\≈3.67\%$

But, if lower surface 124 is soaked in coupling liquid 103, the sodium chloride solution that for example refractive index is 1.55, as shown in Figure 3, in order to be easier to distinguish each reflected light and transmitted light, in figure, each light is separately drawn in the diagram, and in reality, all light all returns and broadcasts on same straight line, high order reflection and transmission light a little less than, ignore at this.The ratio that energy of the secondary reflection light 114 of lower surface 124 accounts for initial total beam energy may be calculated:

$R_2^{\text{'}}={(1-R_1)\×\left(\frac{n_0-n_1}{n_0+n_1}\right)}^2\×100\%\≈0\%$

The ratio that the energy of the secondary transmitted light 112 of upper surface 122 accounts for initial total beam energy may be calculated:

$R_3^{\text{'}}={R_2^{\text{'}}\×\left(\frac{n_0-n_1}{n_0+n_1}\right)}^2\×100\%=0\%$

The secondary transmitted light 112 that is upper surface 122 will disappear, and has reached the object of eliminating secondary transmitted light 112.

In the time using vertical interferometer to detect planar optics element, utilization be the interference effect formation interference fringe between primary event light 111 and the reference light 110 of upper surface 122, and then calculate the face shape error of upper surface 122.But, if planar optics element 123 is positioned in air, according to above-mentioned analysis, can exist the secondary transmitted light 112 of upper surface 122 to participate in interfering, the energy equivalence of its energy and primary event light 111, the interference fringe brightness that the interference fringe that primary event light 111 produces and secondary transmitted light 112 produce is close, and cannot distinguish, thereby can cause severe jamming to detecting face shape error.But according to above-mentioned analysis, as long as lower surface 124 is immersed in liquid, and this liquid refractivity is close with planar optics element material refractive index, such as refractive index differs and is less than 0.1, or refractive index is consistent, and the secondary transmitted light 112 of upper surface 122 almost disappears.This can reach eliminates the object of disturbing, and then completes smoothly the detection to upper surface 122 face shape errors.

Because the Refractive Index of Material of optical element is different.In order completing, the planar optics element of different refractivity material to be detected, to need to select the coupling liquid of different refractivity.According to different optical material refractive indexes, in following table 1, be alternative several frequently seen coupling liquid.

Refractive index and the reflectivity of table 1 glass (refractive index is calculated by 1.55) and some optical medium interfaces

Medium	Refractive index	With glass contact face reflectivity
			Air	1.0	4％
Water	1.333	0.584％
			Ether	1.354	0.456％
Methenyl choloride	1.447	0.118％
			Terebinthina	1.472	0.067％
Glycerine	1.473	0.065％
			Benzene	1.501	0.026％
Carbon disulphide	1.628	0.060％

In addition, coupling liquid 103 also can be selected solution.Under 20 degrees Celsius, its refractive index of the sodium chloride solution of variable concentrations can cover 1.33 to 1.6, and adjustable continuously, is suitable as the coupling liquid 103 of most of optical materials.Coupling liquid 103 can be aforesaid liquid, but is not limited to aforesaid liquid.

Be described further the present invention below in conjunction with the drawings and specific embodiments.

As shown in Figure 4, a kind of device schematic diagram that detects planar optics element, comprises optical element support 102, coupling liquid 103, coupling liquid containing tank 104, interferometer measurement head 105, interferometer bracing frame 106.Wherein, optical element support 102 is for placing optical element 101, it can be positioned over frame on coupling liquid containing tank 104, thereby optical element 101 rear surfaces (non-detection faces) are immersed in coupling liquid, and front surface (surface to be detected) can be by soaked with liquid.Optical element support 102 can be structure as shown in Figure 8, and it exists a frame, and frame exists three brace summers that stretch out outward so that by this stentplacement in coupling liquid containing tank 104 on.The brace summer that frame is outer inwardly to be existed three and intersect with frame midline, for placing optical element, this brace summer need to adopt matte surface, and adopts pitch-dark PROCESS FOR TREATMENT, to reduce mirror-reflection, testing result is impacted.Between inner support beam and frame, adopt hanging beam to be connected.Fig. 9 is it along the cut-open view of dot-and-dash line direction in Fig. 8.Optical element support 102 can be also structure as shown in figure 10, and the difference of itself and Fig. 8 is that the brace summer of frame inside is shorter, and non-intersect, the optical element that applicable placement is larger, and Figure 11 is it along the cut-open view of dot-and-dash line direction in Figure 10.

Coupling liquid 103 is the transparency liquid that refractive index approaches optical element 101 to be detected as far as possible, according to the Refractive Index of Material of optical element to be detected, according to different optical Refractive Index of Material, this coupling liquid can be selected one or more from benzene, ether, glycerine, terebinthina or sodium chloride solution etc., as long as the refractive index of coupling liquid 103 and optical element material refractive index approach or be basically identical, but coupling liquid must not cause chemical damage to optical element.

Coupling liquid containing tank 104 inside can be right cylindrical, there is bottom, do not need upper cover, can contain fluid when mouthful static placement upward and can not make leak of liquid, its inside has delustred coating or matt structure, and light can not produce strong mirror-reflection after injecting, in this example, adopt frosted, and adopt the black PROCESS FOR TREATMENT of surface lacquer that optical field is conventional, to reduce mirror-reflection, but delustring mode is not limited to which.

Treat the impact of master plate optical element 101 face shape errors in order further to reduce mirror-reflection, this coupling solution containing tank 104 also can be made into shape as shown in Figure 5, its bottom is wavy shaped configuration, also can be made as the shape shown in Fig. 6, its bottom is inclined-plane, this design can prevent that light from seeing through after detected optics element, after being reflected by coupling solution containing tank 104 inwalls, the detected optics element 101 of transmission enters interferometer measurement head 105 again, and then prevents that opposite shape detection from causing interference.

For the ease of regulating the height of coupling liquid 103 liquid levels, these coupling solution containing tank 104 upper side can have one and add liquid mouth 108 for what add coupling solution, as shown in Figure 7.This adds liquid mouth 108 upper maintaining an equal level with the upper edge of mate liquid containing tank 104 along height or upper along highly a little less than coupling liquid containing tank 104.Add liquid mouth 108 up big and down small, shape is as funnel, so that add liquid.End opening with mate liquid containing tank 104 internal run-throughs and combine together.This position and size shape of adding liquid mouth 108 is not limited to this.

Now step is used said apparatus to carry out the detection of face shape as follows:

Step (1): the refractive index of inquiring about or testing the optical material that this optical element 101 adopts.Select or allocate transparency liquid that refractive index approaches this optical material refractive index the most as coupling liquid 103 according to the refractive index of optical material, generally mate liquid 103 and be no more than 0.1 with optical material refringence.According to different optical Refractive Index of Material, this coupling liquid can be selected benzene, ether, glycerine, terebinthina, sodium chloride solution etc., as long as the refractive index of coupling liquid 103 and optical element material refractive index approach or be basically identical.In this example, selecting detected optical element 101 its Refractive Index of Materials is 1.55, is about 1.55 sodium chloride solution as coupling liquid 103, but is not limited to this liquid using refractive index.

Step (2): the coupling liquid 103 in step (1) is injected in matching fluid containing tank 104.The optical surface of the detected planar optics element 101 of wiped clean, is positioned over the optical element support 102 that has clamped detected member on coupling liquid containing tank 104, and detected optics surface (front optical surface) upward.Rear optical surface submerges in coupling liquid 103, and front optical surface must not submerge in coupling liquid 103, and must not be polluted by coupling liquid 103.Visual liquid level, as improperly in liquid level can adopt dropper 109 suitably to add or take out coupling liquid 103 by adding liquid mouth 108.

Step (3): the device that places optical element 101 and coupling liquid 103 in step (2) is positioned on interferometer workpiece holder 106, and static a period of time, until liquid level stabilizing.

Step (4): according to the routine operation step of common vertical interferometer, detect and read the face graphic data of optical element 101.

Step (5): take off coupling liquid containing tank 104, and take off successively optical element 101 and optical element support 102, pour out coupling liquid 103, with tap water flushing optical element 101 and coupling liquid containing tank 104, dry.

The invention has the advantages that:

1. this device and method, by reducing the rear optical surface energy of reflection light of planar optics element 101, disturbs the problem that cannot detect planar optics element face shape error thereby can effectively solve common vertical interferometer because of rear optical surface reflected light.

2. simple, the manufacture of this device and method principle and use cost are lower, in the situation that not changing former vertical interferometer structure, can complete the detection to planar optics element face shape error.

3. this device and method adopts non-contacting mode to detect optical component surface shape error, to optical element not damaged, without nip stress.

4. this device and method detects optical component surface shape error, in process, the cleaning of optical element is cleaned with tap water, does not need special cleaning solvent and method.

The above; it is only the specific embodiment of the present invention; but protection scope of the present invention is not limited to this; in the technical scope that any people who is familiar with this technology uncovers in the present invention; intelligible conversion or replacement; all should be encompassed in of the present invention comprising in scope, therefore, protection scope of the present invention should be as the criterion with the protection domain of claims.

Claims (5)

1. the device for detection of planar optics element face shape error, it is characterized in that comprising: optical element support (102), coupling liquid (103) and coupling liquid containing tank (104), described optical element support (102) is for holding optical components (101), and optical element support (102) can be positioned on coupling liquid containing tank (104), coupling liquid (103) is to approach or on all four clear solution with the Refractive Index of Material of the planar optics element (101) that will detect, coupling liquid (103) must not cause chemical damage to detected optics element (101).

2. a kind of device for detection of planar optics element face shape error according to claim 1, it is characterized in that: coupling liquid (103) is benzene, ether, glycerine or terebinthina, coupling liquid (103) can be also solution, for example sodium chloride solution, 20 degrees Celsius time, the refractive index of sodium chloride solution can, according to the concentration of sodium chloride solution from 1.33 allotments to 1.6, cover the ranges of indices of refraction of most of optical material.

3. a kind of device for detection of planar optics element face shape error according to claim 2, it is characterized in that: coupling liquid containing tank (104) inside has delustred coating or matt structure, light can not produce strong mirror-reflection after injecting, for example can adopt the additional blacking of frosted to process to eliminate mirror-reflection, also can adopt Catadioptric system structure to refract light into incoherent region.

4. a kind of device for detection of planar optics element face shape error according to claim 2, it is characterized in that: this coupling solution containing tank (104) exists one to add liquid mouth (108) for what add coupling solution this adds liquid mouth (108) upper maintaining an equal level with the upper edge of mate liquid containing tank (104) along height or upper along highly a little less than coupling liquid containing tank (104).

5. for detection of a method for planar optics element face shape error, the method utilizes the device for detection of planar optics element face shape error described in claim 1 to 4 any one to realize, and it is characterized in that comprising following step:

Step (1): inquire about or test the refractive index of the optical material that this optical element (101) adopts, select and allocate coupling liquid (103);

Step (2): will mate liquid (103) and inject in matching fluid containing tank (104); The detected optics surface of the detected planar optics element (101) of wiped clean, the optical element support (102) of the optical element (101) that has clamped detected member is positioned on coupling liquid containing tank (104), the detected front optical surface of optics element (101) upward, for optical surface to be detected, rear optical surface submerges in matching fluid (103), front optical surface must not submerge in coupling liquid (103), and must not be polluted by coupling liquid (103); As improper in liquid level can by add liquid mouth (108) suitably add or take out coupling liquid (103);

Step (3): the device that places optical element (101) and coupling liquid (103) in step (2) is positioned on vertical interferometer work support (106), static a period of time, until can adopt vertical interferometer to carry out optical component surface shape error-detecting after liquid level stabilizing;

Step (4): according to the routine operation step of common vertical interferometer, detect and read the face graphic data of optical element;

Step (5): take off coupling liquid containing tank, and take off successively optical element and optical element support, pour out coupling liquid, rinse optical element and coupling liquid containing tank drying with tap water.

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