CN109253867B - Optical system focal length measuring system and method - Google Patents

Optical system focal length measuring system and method Download PDF

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CN109253867B
CN109253867B CN201811130587.2A CN201811130587A CN109253867B CN 109253867 B CN109253867 B CN 109253867B CN 201811130587 A CN201811130587 A CN 201811130587A CN 109253867 B CN109253867 B CN 109253867B
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optical system
illumination
focus
positioning module
laser
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CN109253867A (en
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刘大礼
贾馨
郝言慧
岳丽清
李文广
李立广
张志飞
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Beijing Institute of Space Research Mechanical and Electricity
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Beijing Institute of Space Research Mechanical and Electricity
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
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    • G01M11/02—Testing optical properties

Abstract

The invention discloses a focal length measuring system and method of an optical system, which comprises a laser spot lighting positioning module, a spectroscope, a spot detection positioning module, a standard plane mirror and angle measuring equipment, wherein the laser spot lighting positioning module emits a laser light source on a focal point of the measured optical system; and measuring the position change delta y of the reflection auto-collimation focus corresponding to the change delta theta of the included angle between the standard plane mirror and the optical axis of the optical system to be measured, and calculating the focal length of the optical system to be measured according to the relation between the image height and the focal length. The method has accurate focus positioning and is suitable for the assembly, adjustment and detection of the large-caliber long-focus optical lens of the space optical remote sensor.

Description

Optical system focal length measuring system and method
Technical Field
The invention relates to a focal length measuring system and method of an optical system, in particular to a method realized by combining a laser confocal technology, an auto-collimation technology and a precise angle measuring principle. The method has important application in the manufacturing and detection of optical systems, particularly large-caliber long-focus lenses, lenses and other optical systems.
Background
Focal length is an extremely important optical parameter of an optical system. In an optical system, particularly a long-focus large-caliber optical system, accurate measurement of the focus is particularly critical. Typical long-focus large-caliber optical systems include space optical systems and laser nuclear fusion optical systems. In a spatial optical system, accurate measurement of the focal length of a lens is related to the accuracy of the ground resolution of an image and to the accurate assembly of an optical lens and a focal plane device. In a laser nuclear fusion optical system, accurate measurement of the focal length of a lens is related to key characteristics of collimation, focusing, beam quality and the like of strong laser.
At present, a precise angle measurement method based on pentaprism focus determination is mostly adopted in a space optical system, namely, the pentaprism method is used for focusing a vitrolite, the focus determination precision is low, the theodolite is adopted for aiming at the logarithm by human eyes, and the angle measurement precision is low, so that the relative measurement precision is only +/-1%. In the aspect of measuring the focal length of a lens in a laser nuclear fusion optical system, the American national ignition device adopts a laser interference combined focal length measuring method to realize the phase measurement precision of the focal length of 7m +/-0.01 percent, and the method is limited by an interferometer and the caliber of a reference lens; the domestic Shenguang III adopts various methods: the laser confocal combined focal length measuring method realizes the phase measurement precision of +/-0.013% of the focal length of 5m, but the method is limited by the caliber of a confocal sensor and the caliber of a reference lens; the improved precise angle measurement method adopts the wavefront sensor to precisely position the laser light source, realizes the phase measurement precision of +/-0.2% of the focal length of 7m, and is limited by the caliber of the wavefront sensor; the Talbot method achieves a relative measurement accuracy of + -0.02% for a focal length of 7m, which is limited by the laser collimation aperture and the Ronchi grating aperture.
In the method, the precision angle measurement method based on pentaprism focus determination has low precision, the aperture measured by other methods is difficult to break through, and the requirement of the accurate measurement of the focal length of a meter-class aperture optical system with a longer focal length of more than 10m cannot be met.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the method overcomes the defects of the prior art, provides the method for measuring the focal length of the optical system, and solves the problem of low focal point positioning precision during the focal length measurement of the optical system.
The technical solution of the invention is as follows: the utility model provides an optical system focus measurement system which characterized in that includes laser spot illumination orientation module, spectroscope, point detection orientation module, standard level crossing, angle measurement equipment, wherein:
the laser spot lighting positioning module emits a laser light source on the focus of the optical system to be detected, laser enters the optical system to be detected through the spectroscope and then forms parallel light to be emitted, the parallel light is reflected by the standard plane mirror and returns to the optical system to be detected to be converged to form collimated light, the collimated light is reflected by the spectroscope to form a reflection auto-collimation focus, the angle measuring equipment measures the included angle between the standard plane mirror and the optical axis of the optical system to be detected, and the detection positioning module positions the reflection auto-collimation focus; and measuring the position change delta y of the reflection auto-collimation focus corresponding to the change delta theta of the included angle between the standard plane mirror and the optical axis of the optical measurement system by adjusting the included angle of the standard plane mirror relative to the optical axis, and calculating to obtain the focal length of the optical system to be measured according to the relation between the image height and the focal length.
The laser spot illumination positioning module comprises a laser light source, an illumination spectroscope, an illumination objective lens, a spot illumination pinhole and an illumination detector, wherein the laser light source is positioned on an image space focus of the illumination objective lens, the spot illumination pinhole is positioned on an object space focus of the illumination objective lens, the illumination spectroscope is used for enabling the laser light source and the illumination objective lens to be located between, and the illumination detector is positioned on an image space focus of the illumination objective lens formed by reflection of the illumination spectroscope.
The F number of the illumination objective lens is less than or equal to that of the tested optical system.
The point detection positioning module comprises a positioning detector, a detection objective lens and a point detection pinhole, wherein the positioning detector is positioned on an image space focus of the detection objective lens, and the point detection pinhole is positioned on an object space focus of the detection objective lens.
The F number of the detection objective lens is less than or equal to the F number of the detected optical system.
The other technical solution of the invention is as follows: a method for measuring focal length of an optical system, the method comprising the steps of:
s1, adjusting the position of the laser point illumination positioning module, and emitting a laser light source at the focus of the optical system to be tested, so that the laser enters the optical system to be tested through the spectroscope and then forms parallel light to be emitted;
s2, placing a standard plane mirror at a position perpendicular to the optical axis of the optical system to be measured in the object space of the optical system to be measured, so that the parallel light is reflected by the standard plane mirror and returns to the optical system to be measured to be converged to form collimated light, and the collimated light is reflected by the beam splitter to form a reflected auto-collimation focus;
s3, positioning the reflected auto-collimation focus by using a detection positioning module, and measuring the included angle between the standard plane mirror and the optical axis of the optical system to be measured;
s4, adjusting the posture of the standard plane mirror, changing the included angle between the standard plane mirror and the optical axis of the optical system to be measured, and then measuring the included angle between the standard plane mirror and the optical axis of the optical system to be measured again;
s5, adopting the detection positioning module to reposition the reflection auto-collimation focus, and calculating the position change delta y of the reflection auto-collimation focus corresponding to the included angle change delta theta of the standard plane mirror and the optical axis of the optical measurement system;
s6, repeating the steps s 4-s 5 to obtain the change delta theta of the included angle between a group of standard plane mirrors and the optical axis of the optical measurement systemiCorresponding change in position of the reflective autocollimator focus Δ yiAnd i is 1-N, and the focal length of the optical system to be measured is calculated by adopting a least square method according to the relation between the image height and the focal length.
The laser spot illumination positioning module comprises a laser light source, an illumination spectroscope, an illumination objective lens, a spot illumination pinhole and an illumination detector, wherein the laser light source is positioned on an image space focus of the illumination objective lens, the spot illumination pinhole is positioned on an object space focus of the illumination objective lens, the illumination spectroscope is used for enabling the laser light source and the illumination objective lens to be located between, and the illumination detector is positioned on an image space focus of the illumination objective lens formed by reflection of the illumination spectroscope.
The specific method of the step s1 is as follows:
(1.1) adjusting the position of the laser spot illumination positioning module to enable a spot illumination pinhole to be on the design focus of the optical system to be detected;
(1.2) opening a laser spot illumination positioning module to emit an illumination laser light source, enabling the illumination laser light source to enter a tested optical system through a spectroscope, then forming parallel light to be emitted, then reflecting the parallel light to the tested optical system through a standard plane mirror for convergence, and enabling the converged laser to form an auto-collimation focus after being transmitted through the spectroscope;
and (1.3) adjusting the position of the laser spot illumination positioning module until a detection light spot of an auto-collimation focus is formed on the illumination detector, so that a point illumination pinhole of the laser spot illumination positioning module is preliminarily positioned on an actual focus of the optical system to be detected.
And (1.4) further adjusting the position of the laser point illumination positioning module to enable the light intensity of the light spot to reach the maximum value, so that the point illumination pinhole of the laser point illumination positioning module is accurately positioned on the actual focus of the optical system to be measured.
The point detection positioning module comprises a positioning detector, a detection objective lens and a point detection pinhole, wherein the positioning detector is positioned on an image space focus of the detection objective lens, and the point detection pinhole is positioned on an object space focus of the detection objective lens.
The method for positioning the reflection auto-collimation focus by adopting the detection positioning module comprises the following steps:
(3.1) adjusting the position of the point detection positioning module to enable the point detection pinhole to be positioned on the designed reflection auto-collimation focus of the optical system to be detected;
(3.2) opening the laser spot illumination positioning module to emit an illumination laser light source, enabling the illumination laser light source to enter the optical system to be detected through the spectroscope, then forming parallel light to be emitted, then reflecting the parallel light to the optical system to be detected through the standard plane mirror for convergence, and reflecting the converged laser light through the spectroscope to form a reflected auto-collimation focus;
and (3.3) adjusting the position of the point detection positioning module, wherein laser passes through the point detection pinhole, the detection objective lens converges, and a detection light spot is formed on the positioning detector, so that the point detection pinhole of the point detection positioning module is preliminarily positioned on the actual reflection auto-collimation focus of the optical system to be detected.
And (3.4) further adjusting the position of the point detection positioning module to enable the light intensity of the detection light spot to reach the maximum value, so that the point detection pinhole of the point detection positioning module is accurately positioned on the actual reflection auto-collimation focus of the measured optical system.
Compared with the prior art, the invention has the beneficial effects that:
(1) the invention applies the technical means of laser confocal measurement, solves the problems that the repeatability and the accuracy of the positioning measurement result of the introduced focal plane or focus can not be ensured, the measurable caliber is limited and the like in the process of testing the focal length of the existing large-caliber long-focus optical lens, and has higher repeatability, accuracy and practicability;
(2) the invention adopts the optical auto-collimation technical means to realize the high-precision positioning and measurement of the auto-collimation focus, thereby improving the measurement accuracy and precision of the change of the focus position delta y, and fundamentally solving the problem of low measurement accuracy and precision of the delta y caused by low focus-fixing precision of the existing precision angle measurement method;
(3) the invention adopts the least square method to process data, can eliminate the influence of the deviation alpha of the initial included angle between the standard plane reflector and the optical axis of the optical system to be measured caused by limited adjustment precision, thereby improving the reliability of focal length calculation.
(4) The invention precisely focuses the laser light source emitted by the laser point illumination positioning module on the focus on the image space axis of the measured optical system by utilizing the characteristic that the peak value of the transverse and axial light intensity response of the laser confocal auto-collimation optical system appears when the focus of the illumination objective lens of the laser point illumination positioning module and the focus of the measured optical system are precisely superposed.
(5) The invention utilizes the characteristic that the peak value of the transverse and axial light intensity response of the laser confocal auto-collimation optical system occurs when the focus of the detection objective lens of the point detection positioning module is precisely superposed with the focus of the measured optical system, and accurately positions the focus of the detection objective lens of the point detection positioning module on the reflection auto-collimation focal plane of the measured optical system and accurately positions the reflection auto-collimation axis and the off-axis focus;
(6) the invention adopts high-precision angle measurement equipment to improve the measurement precision of delta theta;
(7) the caliber of the optical system to be detected is only limited by the caliber of the standard plane mirror, the detection of the optical system within the caliber of the standard plane mirror can be realized, and the focus measurement of a large-caliber long-focus lens and a lens can be realized.
Drawings
FIG. 1 is a schematic diagram of a process implementation of an embodiment of the invention.
Fig. 2 is a schematic diagram of the transverse and axial responses of the laser confocal auto-collimation optical system of the embodiment of the invention.
FIG. 3 is a schematic diagram of focal length measurement according to an embodiment of the present invention.
Detailed Description
The invention is described in detail below with reference to the figures and specific examples.
The invention provides an optical system focal length measuring system, namely a laser confocal auto-collimation optical system, which utilizes the strict conjugate characteristic, the axial precise focusing characteristic and the transverse high resolution characteristic of an incident focal point and an auto-collimation focal point of the laser confocal auto-collimation optical system to realize the precise positioning of a laser light source emitted by a laser point illumination positioning module on an axial incident focal point of the laser confocal auto-collimation optical system, the precise positioning of a point detection positioning module on an on-axis focal point and an off-axis focal point of the laser confocal auto-collimation optical system and measure the accurate change delta y of the position between the two; the method has the advantages that the precise angle measuring equipment is synchronously adopted, the corresponding field angle change 2 delta theta of the focus on the auto-collimation axis and the focus outside the auto-collimation axis is accurately measured, then the focal length f is calculated by utilizing a relation formula of the focal length, the field angle and the image height, the accurate measurement of the focal length of the optical system to be measured is realized, the operation is simple, the criterion is objective and precise, the automatic measurement is easy to realize, and the requirement of the focal length measurement in the optical manufacturing and detection of various optical systems can be met.
As shown in fig. 1, the system hardware includes a laser spot lighting positioning module 1, a spectroscope 2, a spot detection positioning module 3, a standard plane mirror 6, and an angle measurement device 7, wherein:
the laser spot lighting positioning module 1 emits a laser light source on a focal point of a measured optical system 5, laser enters the measured optical system 5 through a spectroscope 2 to form parallel light to be emitted, the parallel light is reflected by a standard plane mirror 6 to return to the measured optical system 5 to be converged to form collimated light, the collimated light is reflected by the spectroscope 2 to form a reflected auto-collimation focal point, an angle measuring device 7 measures an included angle between the standard plane mirror 6 and an optical axis of the measured optical system 5, and a detection positioning module 3 positions the reflected auto-collimation focal point; and (3) measuring the position change delta y of the reflection auto-collimation focus corresponding to the change delta theta of the included angle between the standard plane mirror 6 and the optical axis of the optical measurement system 5 by adjusting the included angle between the standard plane mirror 6 and the optical axis, and calculating the focal length of the optical measurement system 5 according to the relation between the image height and the focal length.
The laser spot illumination positioning module 1 comprises a laser light source 101, an illumination beam splitter 102, an illumination objective 103, a spot illumination pinhole 104 and an illumination detector 105, wherein the laser light source 101 is located at an image focus of the illumination objective 103, the spot illumination pinhole 104 is located at an object focus of the illumination objective 103, the illumination beam splitter 102 is used for enabling the laser light source 101 to be located between the illumination objective 103, and the illumination detector 105 is located at an image focus of the illumination objective 103 formed by reflection of the illumination beam splitter 102. The illumination detector 105 may be a point detector or an area array image detector. The F number of the illumination objective lens 103 is less than or equal to the F number of the optical system 5 to be measured. Can be changed according to the F number of the measured optical system 5 to match the F number of the measured optical system 5.
The laser light source 101 generates laser light, the laser light passes through the beam splitter 102, is focused by the illumination objective 103 and exits through the illumination pinhole 104, meanwhile, the laser light transmitted by the beam splitter 2 is converged by the illumination pinhole 104 and the illumination objective 103, and the converged laser light is reflected by the illumination beam splitter 102 on the illumination detector 105 to form a detection light spot.
The point detection positioning module 3 comprises a positioning detector 301, a detection objective lens 303 and a point detection pinhole 302, wherein the positioning detector 301 is located at an image space focus of the detection objective lens 303 and is used for shaping and filtering incident laser spots, and the point detection pinhole 302 is located at an object space focus of the detection objective lens 303. The positioning detector 301 of the detection positioning module 3 may be a point detector or an area array image detector. The F number of the detection objective 303 is less than or equal to the F number of the optical system 5 to be measured. Can be changed according to the F number of the measured optical system 5 to match the F number of the measured optical system 5.
Based on the above optical system focal length measuring system, the invention also provides an optical system focal length measuring method, which comprises the following steps:
s1, adjusting the position of the laser point illumination positioning module 1, and emitting a laser light source at the focus of the optical system 5 to be detected, so that laser enters the optical system 5 to be detected through the spectroscope 2 to form parallel light to be emitted; the specific method comprises the following steps:
1.1, adjusting the position of a laser point illumination positioning module 1 to enable a point illumination pinhole 104 to be on the design focus of a tested optical system 5;
1.2, opening a laser point illumination positioning module 1 to emit an illumination laser light source, enabling the illumination laser light source to enter a tested optical system 5 through a spectroscope 2, then forming parallel light to be emitted, then reflecting the parallel light to the tested optical system 5 through a standard plane mirror 6 to be converged, and enabling the converged laser to form an auto-collimation focus after being transmitted through the spectroscope 2;
1.3, adjusting the position of the laser spot illumination positioning module 1 until a detection light spot of an auto-collimation focus is formed on the illumination detector 105, so as to initially position the spot illumination pinhole 104 of the laser spot illumination positioning module 1 at the actual focus of the tested optical system 5.
And 1.4, further adjusting the position of the laser point illumination positioning module 1 to enable the light intensity of the light spot to reach the maximum value, so that the point illumination pinhole 104 of the laser point illumination positioning module 1 is accurately positioned on the actual focus of the optical system 5 to be detected.
The method specifically comprises the following steps:
defining the optical axis direction of the optical system 5 to be measured as the Z direction, a plane perpendicular to the optical axis direction of the optical system 5 to be measured as an XOY plane, continuously driving the laser spot illumination positioning module 1 along the X direction, measuring the light intensity of a light spot through the illumination detector 105, synchronously recording the position of a point illumination pinhole 104 of the laser spot illumination positioning module 1 in the X direction, then fitting a relation curve of the light intensity and the transverse position to obtain a light intensity peak value and a corresponding X direction position xImax, driving the laser spot illumination positioning module 1 to position the point illumination pinhole 104 at the xImax, and then positioning the point illumination pinhole 104 at the yImax in the Y direction by adopting the same method; then, the point illumination pinhole 104 is positioned at the position of zmimax in the axial Z direction by adopting the same method; therefore, the laser light source emitted by the laser point illumination positioning module 1 is precisely positioned at the focal point on the image side axis of the measured optical system 5, and the transmission auto-collimation focal point and the focal point on the image side axis are precisely superposed at the moment, so that the laser light source illumination with precise position is provided for the laser confocal auto-collimation optical system.
The step utilizes the characteristic that the peak value of the transverse and axial light intensity response of the laser confocal auto-collimation optical system appears when the focus of the illumination objective lens 103 of the laser point illumination positioning module 1 and the transmission auto-collimation focus of the measured optical system 5 are precisely superposed, and the laser light source emitted by the laser confocal micro-illumination system 1 is precisely positioned on the focus on the image space axis of the measured optical system 5, so as to provide point illumination with precise position for the laser confocal auto-collimation optical system.
s2, placing a standard plane mirror 6 at a position perpendicular to the optical axis of the optical system 5 to be measured on the object side of the optical system 5 to be measured, so that the parallel light is reflected by the standard plane mirror 6 to return to the optical system 5 to be measured for converging to form collimated light, and the collimated light is reflected by the spectroscope 2 to form a reflected auto-collimation focus;
and s3, positioning the reflection autocollimation focus by using the detection positioning module 3. Because the posture adjustment accuracy of the standard plane mirror 6 is limited, in practical situations, the standard plane mirror 6 can only be adjusted to make the reflecting surface of the standard plane mirror 6 perpendicular to the optical axis of the optical system 5 to be measured as much as possible, and therefore, the included angle between the standard plane mirror 6 and the optical axis of the optical system 5 to be measured needs to be measured.
The method for positioning the reflection auto-collimation focus by adopting the detection positioning module 3 comprises the following steps:
3.1, adjusting the position of the point detection positioning module 3 to enable the point detection pinhole 302 to be on the designed reflection auto-collimation focus of the detected optical system 5;
3.2, opening the laser point illumination positioning module 1 to emit an illumination laser light source, enabling the illumination laser light source to enter the tested optical system 5 through the spectroscope 2, then forming parallel light to be emitted, then reflecting the parallel light to the tested optical system 5 through the standard plane mirror 6 for convergence, and reflecting the converged laser light through the spectroscope 2 to form a reflected auto-collimation focus;
3.3, adjusting the position of the point detection positioning module 3, converging the laser through the point detection pinhole 302 and the detection objective 303 to form a detection light spot on the positioning detector 301, so as to initially position the point detection pinhole 302 of the point detection positioning module 3 on the actual reflection auto-collimation focus of the measured optical system 5.
And 3.4, further adjusting the position of the point detection positioning module 3 to enable the light intensity of the detection light spot to reach the maximum value, so that the point detection pinhole 302 of the point detection positioning module 3 is accurately positioned on the actual reflection auto-collimation focus of the measured optical system 5.
The method specifically comprises the following steps:
similarly, the direction of the reflection autocollimation optical axis of the measured optical system 5 is defined as the Z ' direction, and a plane perpendicular to the direction of the reflection autocollimation optical axis of the measured optical system 5 is defined as the X ' OY ' plane. As shown in fig. 2, the transverse and axial response of the laser confocal auto-collimation optical system precisely positions the point detection positioning module 3 by the following specific method: continuously driving a point detection positioning module 3 in the transverse X ' direction, synchronously measuring the light intensity and the transverse position of the light spot, then fitting a relation curve of the light intensity and the transverse position to obtain a light intensity peak value and a transverse position xImax ' corresponding to the light intensity peak value, driving the point detection positioning module 3 to position a point detection pinhole 302 at the xImax ', and then positioning the point detection pinhole 302 at a yImax ' position in the transverse Y ' direction by adopting the same method; then, the point detection pinhole 302 is positioned at the position of zmimax 'in the axial X' direction by adopting the same method; thus, the point detection pinhole 302 of the point detection positioning module 3 is precisely positioned at the position of the focal point on the reflection self-collimation axis of the optical system 5 to be detected, and the focal point on the reflection self-collimation axis and the focal point on the image space axis are conjugated at the moment, so that the position accurate point detection is provided for the laser confocal self-collimation optical system; the position y0 of the now reflected autocollimator focus is measured and recorded.
The step utilizes the characteristic that the peak value of the transverse and axial light intensity response of the laser confocal auto-collimation optical system appears when the focus of the detection objective 303 of the point detection positioning module 3 and the reflection auto-collimation focus of the measured optical system 5 are precisely superposed, so as to realize the accurate positioning of the on-axis and off-axis reflected focuses and the accurate measurement of the focus position.
When the position detector 301 of the point detection positioning module 3 detects a maximum value, the focus of the illumination objective lens 103 of the laser point illumination positioning module 1 is conjugated with the focus of the detection objective lens 303 of the point detection positioning module 3;
s4, adjusting the posture of the standard plane mirror 6, changing the included angle between the standard plane mirror 6 and the optical axis of the optical system 5, and then measuring the included angle between the standard plane mirror 6 and the optical axis of the optical system 5;
the standard flat mirror 6 is driven to rotate by a small angle, and the angle theta of the standard flat mirror 3 at the moment is measured1Measuring and recording the position y1 of the reflected autocollimator focus at this time; note the change in focal position as Δ y1＝y1-y0(ii) a Standard mirror angle change is delta theta1＝θ1-θ0The change of the focal point-to-field angle is 2 Δ θ1。
s5, the detection positioning module 3 positions the reflection auto-collimation focus again, and calculates the position change delta y of the reflection auto-collimation focus corresponding to the change delta theta of the included angle between the standard plane mirror 6 and the optical axis of the optical measurement system 5;
s6, repeating the steps s 4-s 5 to obtain a group of standard plane mirrors 6 and the change delta theta of the included angle of the optical axis of the optical measurement system 5iCorresponding change in position of the reflective autocollimator focus Δ yiAnd i is 2.. n, and the focal length of the measured optical system 5 is calculated by adopting a least square method according to the relation between the image height and the focal length.
The relationship between the image height and the focal length is as follows:
ftan(2Δθ+2α)＝Δy
s7, processing ftan (2 Δ θ +2 α) ═ Δ y by a least square method, and obtaining the focal length f of the optical lens to be measured and the initial included angle deviation α between the standard plane mirror and the optical axis of the optical system to be measured.
And by combining with a precise angle measurement device 7, accurately measuring the corresponding field angles of the on-axis and off-axis focuses reflected from the collimation axis, and by combining with a least square data processing method, separating the initial adjustment error of the standard plane mirror 6 and the measured optical system 5, and realizing accurate measurement of the focal length of the measured optical system 5.
The invention has simple operation, objective and accurate criterion, accurate focus positioning and easy realization of automatic measurement, has very important application in the assembly, adjustment and detection of the large-caliber long-focus optical lens of the space optical remote sensor, the detection of the large-caliber long-focus lens of the laser nuclear fusion optical system and can also be used for measuring the focal length and the top focal length of various conventional caliber focal length optical systems.
Parts of the specification which are not described in detail are within the common general knowledge of a person skilled in the art.

Claims (9)

1. The utility model provides an optical system focus measurement system which characterized in that includes laser spot illumination orientation module (1), spectroscope (2), point detection orientation module (3), standard level crossing (6), goniometric equipment (7), wherein:
the laser spot illumination positioning module (1) emits a laser light source on the focus of a detected optical system (5), laser penetrates through the spectroscope (2) and enters the detected optical system (5) to form parallel light to be emitted, the parallel light is reflected by the standard plane mirror (6) and returns to the detected optical system (5) to be converged to form collimated light, the collimated light is reflected by the spectroscope (2) to form a reflected auto-collimation focus, the angle measuring equipment (7) measures the included angle between the standard plane mirror (6) and the optical axis of the detected optical system (5), and the detection positioning module (3) positions the reflected auto-collimation focus; measuring the position change delta y of a reflection auto-collimation focus corresponding to the change delta theta of the included angle between the standard plane mirror (6) and the optical axis of the optical system (5) to be measured by adjusting the included angle of the standard plane mirror (6) relative to the optical axis, and calculating the focal length of the optical system (5) to be measured according to the relation between the image height and the focal length;
the laser spot illumination positioning module (1) comprises a laser light source (101), an illumination spectroscope (102), an illumination objective (103), a spot illumination pinhole (104) and an illumination detector (105), wherein the laser light source (101) is located at an image space focus of the illumination objective (103), the spot illumination pinhole (104) is located at an object space focus of the illumination objective (103), the illumination spectroscope (102) is used for enabling the laser light source (101) and the illumination objective (103) to be located between, and the illumination detector (105) is located at an image space focus of the illumination objective (103) formed by reflection of the illumination spectroscope (102).
2. An optical system focal length measuring system according to claim 1, characterized in that the F-number of the illumination objective lens (103) is equal to or less than the F-number of the optical system (5) under test.
3. The focal length measuring system of an optical system as claimed in claim 1, wherein the point detection positioning module (3) comprises a positioning detector (301), a detection objective (303) and a point detection pinhole (302), wherein the positioning detector (301) is located at an image-side focal point of the detection objective (303), and the point detection pinhole (302) is located at an object-side focal point of the detection objective (303).
4. A focal length measuring system of an optical system according to claim 3, wherein the F-number of the detection objective lens (303) is equal to or less than the F-number of the optical system (5) to be measured.
5. A method for measuring the focal length of an optical system based on the system of claim 1, comprising the steps of:
s1, adjusting the position of the laser spot illumination positioning module (1), and emitting a laser light source on the focus of the optical system to be detected (5), so that laser enters the optical system to be detected (5) through the spectroscope (2) to form parallel light to be emitted;
s2, placing a standard plane mirror (6) at a position perpendicular to the optical axis of the optical system (5) to be detected on the object side of the optical system (5) to be detected, so that the parallel light is reflected by the standard plane mirror (6) and returns to the optical system (5) to be detected to be converged to form collimated light, and the collimated light is reflected by the spectroscope (2) to form a reflected auto-collimation focus;
s3, positioning the reflected auto-collimation focus by using the detection positioning module (3), and measuring the included angle between the standard plane mirror 6 and the optical axis of the optical system (5) to be measured;
s4, adjusting the posture of the standard plane mirror (6), changing the included angle between the standard plane mirror (6) and the optical axis of the optical system (5) to be measured, and then measuring the included angle between the standard plane mirror (6) and the optical axis of the optical system (5) to be measured again;
s5, adopting the detection positioning module (3) to reposition the reflection auto-collimation focus, and calculating the position change delta y of the reflection auto-collimation focus corresponding to the change delta theta of the included angle between the standard plane mirror (6) and the optical axis of the optical system (5) to be detected;
s6, repeating the steps s 4-s 5 to obtain a group of standard plane mirrors (6) and the change delta theta of the included angle of the optical axis of the optical system (5) to be measurediCorresponding change in position of the reflective autocollimator focus Δ yiAnd i is 1-N, and the focal length of the optical system (5) to be measured is calculated by adopting a least square method according to the relation between the image height and the focal length.
6. The focal length measuring method of an optical system according to claim 5, wherein the laser spot illumination positioning module (1) comprises a laser light source (101), an illumination beam splitter (102), an illumination objective (103), a spot illumination pinhole (104), and an illumination detector (105), wherein the laser light source (101) is located at an image-side focal point of the illumination objective (103), the spot illumination pinhole (104) is located at an object-side focal point of the illumination objective (103), the illumination beam splitter (102) is used for connecting the laser light source (101) and the illumination objective (103), and the illumination detector (105) is located at an image-side focal point of the illumination objective (103) formed by reflection of the illumination beam splitter (102).
7. The method according to claim 6, wherein the step s1 is executed by:
(1.1) adjusting the position of the laser spot illumination positioning module (1) to enable a spot illumination pinhole (104) to be on the design focus of the optical system (5) to be detected;
(1.2) opening a laser spot illumination positioning module (1) to emit an illumination laser light source, enabling the illumination laser light source to enter a tested optical system (5) through a spectroscope (2) to form parallel light to be emitted, reflecting the parallel light back to the tested optical system (5) through a standard plane mirror (6) to be converged, and enabling the converged laser to form an auto-collimation focus after being transmitted through the spectroscope (2);
(1.3) adjusting the position of the laser spot illumination positioning module (1) until a detection light spot of an auto-collimation focus is formed on an illumination detector (105), so that a spot illumination pinhole (104) of the laser spot illumination positioning module (1) is preliminarily positioned on an actual focus of the optical system to be detected (5);
(1.4) further adjusting the position of the laser point illumination positioning module (1) to enable the light intensity of the light spot to reach the maximum value, so that the point illumination pinhole (104) of the laser point illumination positioning module (1) is accurately positioned on the actual focus of the optical system (5) to be measured.
8. An optical system focus measuring method based on the system of claim 5, characterized in that the spot detection positioning module (3) comprises a positioning detector (301), a detection objective (303), and a spot detection pinhole (302), wherein the positioning detector (301) is located at the image-side focal point of the detection objective (303), and the spot detection pinhole (302) is located at the object-side focal point of the detection objective (303).
9. The method for measuring the focal length of the optical system according to claim 8, wherein the method for positioning the reflection auto-collimation focal point by using the detection positioning module (3) comprises the following steps:
(3.1) adjusting the position of the point detection positioning module (3) to enable the point detection pinhole (302) to be on the designed reflection auto-collimation focus of the optical system (5) to be detected;
(3.2) opening the laser spot illumination positioning module (1) to emit an illumination laser light source, enabling the illumination laser light source to enter the optical system (5) to be detected through the spectroscope (2), then forming parallel light to be emitted, then reflecting the parallel light to the optical system (5) to be detected through the standard plane mirror (6) to be converged, and reflecting the converged laser light through the spectroscope (2) to form a reflected auto-collimation focus;
(3.3) adjusting the position of the point detection positioning module (3), converging the laser through a point detection pinhole (302) and a detection objective lens (303), and forming a detection light spot on a positioning detector (301), so that the point detection pinhole (302) of the point detection positioning module (3) is preliminarily positioned on an actual reflection auto-collimation focus of the optical system (5) to be detected;
and (3.4) further adjusting the position of the point detection positioning module (3) to enable the light intensity of the detection light spot to reach the maximum value, so that the point detection pinhole (302) of the point detection positioning module (3) is accurately positioned on the actual reflection auto-collimation focus of the optical system (5) to be detected.
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