CN117471705A - Cross-band ultra-large-range achromatic focusing optical system - Google Patents

Abstract

The invention describes a cross-band ultra-large range achromatic focusing optical system, which is provided with a near end close to an emission position of a light source and a far end far from the emission position, wherein a first lens group with positive optical power and a second lens group with positive optical power are sequentially arranged from the near end to the far end along the incident light direction in a common optical axis way, the first lens group comprises a first achromatic lens and the second lens group comprises a second achromatic lens; the interval between the emitting position and the second lens group on the optical axis is a first distance, the interval between the first lens group and the second lens group on the optical axis is a second distance, the first distance is a fixed value, and the first lens group can move along the optical axis to change the second distance; the ratio of the focal length of the first lens group to the focal length of the second lens group is within a first preset range. Therefore, a set of light path system can be used for focusing a plurality of light beams with different wavelengths on the surface of the measured object at the same time, and focal length adjustment can be realized.

Description

Cross-band ultra-large-range achromatic focusing optical system

Technical Field

The invention relates to the technical field of laser measurement, in particular to a cross-band ultra-large-range achromatic focusing optical system.

Background

The laser ranging system (also called as a laser interferometry system) can rapidly and accurately obtain relevant distance information in a non-contact measurement mode in a large distance range, meets the requirements of high-precision detection and assembly, and is widely applied to precision detection and assembly of workpieces of various sizes, particularly large-size workpieces. In actual operation, the laser ranging system generally irradiates measuring light onto the surface of the measured object, receives return light reflected or scattered by the measured object, and makes interference between the measuring light and the return light to form an interference wave.

Because infrared light has the characteristics of long wavelength, strong diffraction capability, small interference by ambient light and the like, the laser ranging system generally uses infrared light as measuring light, and because the infrared light is not seen by naked eyes, in order to facilitate operation, the laser ranging system often adds visible light band laser as indicating light, in the prior art, because the band difference of the measuring light and the indicating light is large, the measuring light and the indicating light are respectively collimated through respective optical path systems and then are combined into an optical path to irradiate on a measured object.

In the prior art, on one hand, measuring light and indicating light are respectively irradiated on an object to be measured through a multi-light path system, and the light path structure is high in complexity; on the other hand, due to the limitation of the collimation degree of the optical path system, the loss of optical energy in propagation increases along with the increase of the measurement distance L (namely, the distance between the laser ranging system and the measured object), and the information of return light (namely, the return light information) received by the laser ranging system decreases along with the increase of the measurement distance, particularly for the measured object with low reflectivity and large surface roughness, the return light information is weaker, so that interference waves are not formed; therefore, in another prior art, in order to increase the return light information of the surface of the measured object, part of the laser ranging system uses a mirror target (also referred to as a target) to be attached to the surface of the measured object, but the use of the target limits the measurement speed and measurement accuracy of the laser ranging system, and cannot meet the measurement requirements of high efficiency and high accuracy.

Disclosure of Invention

The present invention has been made in view of the above-mentioned circumstances of the prior art, and an object of the present invention is to provide a compact broadband-spanning ultra-large-range achromatic focusing optical system with a simple structure, which can focus a plurality of light beams with different wavelengths on the surface of a measured object at the same time by using a set of optical path system, so as to obtain strong return information, thereby facilitating optical processing by using the return information, and adjusting the focal length of the focusing optical system according to actual needs.

To this end, the present invention provides a cross-band ultra-large-range achromatic focusing optical system having a proximal end near an emission position of a light source and a distal end far from the emission position, a first lens group having positive optical power and a second lens group having positive optical power being disposed coaxially in order from the proximal end to the distal end in an incident light direction, the first lens group including a first achromatic lens and the second lens group including a second achromatic lens; setting a first distance between the emission position and the second lens group on the optical axis, setting a second distance between the first lens group and the second lens group on the optical axis, setting the first distance to be a constant value, and enabling the first lens group to move along the optical axis to change the second distance; the ratio of the focal length of the first lens group to the focal length of the second lens group is within a first preset range.

In the invention, by adopting the achromatic lens, laser beams with various different wavelengths tend to be focused on a consistent point under the same measuring distance, a better focusing state is obtained, and the diameter difference of light spots formed by focusing with different wavelengths is smaller, so that the concentration of light energy is high, the return light signal reflected or scattered back by the surface of the measured object is further enhanced, and when the first lens group moves along the optical axis to focus the measuring light incident to the focusing optical system on a preset point on the surface of the measured object, the return light formed by reflecting or scattering by the measured object is focused on the position of the transmitting position of the light source, thereby obtaining the return light with higher light energy, and being beneficial to optical signal processing. And the position of a focusing light spot formed by the focusing system by the laser beams with various different wavelengths can be changed by moving the first lens group along the optical axis, namely, the laser beams with different wavelengths can be focused on the surface of the measured object through the focusing system by moving the first lens group according to the difference of the measured distances of the measured object, so that the focal length of the focusing system can be adjusted. In addition, the invention can make the structure of the focusing optical system compact, reduce the volume and weight and realize quick focusing by reasonably distributing the focal power of the first lens group and the second lens group.

In addition, according to the cross-band ultra-large-range achromatic focusing optical system according to the present invention, optionally, said first achromatic lens includes a first lens having negative optical power and a second lens having positive optical power. In this case, the first lens of negative power and the second lens of positive power can form a lens combination of a "positive and negative" structure, so that correction of chromatic aberration and spherical aberration can be advantageously achieved.

In addition, according to the cross-band ultra-large-range achromatic focusing optical system according to the present invention, optionally, the focal length of the first achromatic lens measured under d-light is not less than 90 mm and not more than 140 mm. In this case, it is possible to facilitate the second lens having positive optical power to be mated with the first lens having negative optical power to alleviate the problem of spherical aberration, and to facilitate achievement of a focus position of light beams of different wavelengths to be uniform.

In addition, according to the cross-band ultra-large-range achromatic focusing optical system according to the present invention, optionally, the refractive index of the material of the first lens measured under d-light is not less than 1.85 and not more than 1.95, and the abbe coefficient of the first lens measured under d-light is not less than 30 and not more than 35; the second lens has a material refractive index of not less than 1.4 and not more than 1.5 measured under d-light, and an Abbe's number of not less than 80 and not more than 95 measured under d-light. In this case, the first lens has a larger material refractive index and a smaller abbe coefficient, which means that the first lens has a higher dispersion characteristic; the second lens has a smaller material refractive index and a larger abbe coefficient, which means that the second lens has a lower dispersion characteristic, so that the first lens has a larger material refractive index and a smaller abbe coefficient having a certain difference from the material refractive index and abbe coefficient of the second lens, thereby being capable of facilitating systematic chromatic aberration correction.

In addition, according to the cross-band ultra-large-range achromatic focusing optical system according to the present invention, optionally, said second lens group further comprises a third lens having positive optical power, said third lens being disposed on a side of said second achromatic lens near said proximal end. In this case, the third lens has positive focal power, can further realize focusing of light beam, and simultaneously, the third lens cooperates with the second achromatic lens, can be more convenient for realize the focal power distribution of second lens group, and reasonable focal power distribution is in order to do benefit to the correction of system spherical aberration.

In addition, according to the cross-band ultra-large-range achromatic focusing optical system according to the present invention, optionally, said second achromatic lens includes a fourth lens having negative optical power and a fifth lens having positive optical power. In this case, the fourth lens of negative power and the fifth lens of positive power can form a lens combination of a "positive and negative" structure, so that correction of chromatic aberration and spherical aberration can be advantageously achieved.

In addition, according to the cross-band ultra-large-range achromatic focusing optical system according to the present invention, optionally, a focal length of the third lens measured under d-light is not less than 400 mm and not more than 800 mm, and a focal length of the second achromatic lens measured under d-light is not less than 150 mm and not more than 220 mm. In this case, it is possible to facilitate the fifth lens having positive optical power to be matched with the fourth lens having negative optical power to alleviate the problem of aberration, and to facilitate the achievement of the focus positions of light beams of different wavelengths to be uniform; the third lens is matched with the fourth lens and the fifth lens, so that the focal power distribution of the second lens group can be realized more conveniently, and the reasonable focal power distribution is favorable for correcting the spherical aberration of the system.

In addition, according to the cross-band ultra-large-range achromatic focusing optical system according to the present invention, optionally, the refractive index of the material of the third lens measured under d-light is not less than 1.9 and not more than 2, and the abbe coefficient of the third lens measured under d-light is not less than 15 and not more than 20; a material refractive index of the fourth lens measured under d-light is not less than 1.9 and not more than 2, and an abbe coefficient of the fourth lens measured under d-light is not less than 15 and not more than 25; the refractive index of the material of the fifth lens measured under d-light is not less than 1.4 and not more than 1.5, and the Abbe's number measured under d-light is not less than 80 and not more than 95. In this case, the fourth lens has a larger material refractive index and a smaller abbe coefficient, which means that the fourth lens has a higher dispersion characteristic; the fifth lens has a smaller material refractive index and a larger abbe coefficient, namely the fifth lens has a lower dispersion characteristic, so that the fourth lens has a larger material refractive index and a smaller abbe coefficient and the material refractive index and the abbe coefficient of the fifth lens have a certain difference, and the chromatic aberration correction of the system can be facilitated; the third lens is matched with the fourth lens and the fifth lens, so that the focal power distribution of the second lens group can be realized more conveniently, and the reasonable focal power distribution is favorable for correcting the spherical aberration of the system.

In addition, according to the cross-band ultra-large-range achromatic focusing optical system according to the present invention, optionally, the first preset range is not less than 1/1.5 and not more than 1.

In this case, when the ratio of the focal length of the first lens group to the focal length of the second lens group is smaller than the lower limit of the first preset range, in other words, in the focusing optical system, the focal length of the first lens group is smaller than the focal length of the second lens group, the first lens group bears larger optical power (the optical power is the inverse of the focal length), so that the first lens group has the condition of generating larger chromatic aberration and spherical aberration, which causes the aberration of the focusing optical system to increase and the quality of the focusing light spot to decrease; in addition, when the light beams with different wavelengths pass through the first lens group with larger focal power, the deflection angle difference of the light beams is increased, so that the difference of incidence angles when the light beams enter the second lens group is correspondingly increased, the aberration difference is further increased, and the light beams with different wavelengths are unfavorable to realize that the light beams with different wavelengths present a better focusing state on the surface of an object to be measured under different measuring distances. In addition, the first lens group of larger optical power often has a complicated structure, which may result in a larger volume and weight of the focusing optical system.

When the ratio of the focal length of the first lens group to the focal length of the second lens group is greater than the upper limit of the first preset range, in other words, in the focusing optical system, the focal length of the first lens group is greater than the focal length of the second lens group, the first lens group bears smaller optical power, and when light beams with different wavelengths pass through the first lens group with smaller optical power, the first lens group can only provide weaker aberration correction, thereby complicating the design of the second lens group. At the same time, the focusing ability of the first lens group is also impaired, in other words, the first lens group needs to be moved a larger distance on the optical axis to obtain a better focusing state, whereby, in order to obtain the same measurement distance, the axial dimension of the focusing optical system needs to be increased, or, in the case where the axial dimension of the focusing optical system has been determined, the range of the measurement distance will be reduced. Also, in order to obtain the same focusing state, it is necessary to move the first lens group a larger distance, in other words, the speed of focusing is slowed, so that the requirement of rapid focusing may not be satisfied.

Therefore, the ratio of the focal length of the first lens group to the focal length of the second lens group can be favorable for enabling the first lens group and the second lens group to obtain reasonable focal power distribution respectively in a first preset range, on one hand, the two lens groups can be enabled to bear the function of aberration correction respectively, the axial chromatic aberration effect is weakened, on the other hand, the focusing capability of the first lens group can be improved conveniently, and a larger measuring distance range and a quicker focusing speed are obtained.

In addition, according to the cross-band ultra-wide-range achromatic focusing optical system according to the present invention, optionally, the cross-band ultra-wide-range achromatic focusing optical system is configured to collectively focus at least two light beams of different wavelengths at a preset point, the preset point being changed with a change in the second distance, the wavelength of the light beams being not less than 639 nm and not more than 1550 nm. In this case, the preset point is changed along with the change of the second distance, that is, the first lens group can be used as a focusing lens group, and the focal length of the focusing optical system can be adjusted by moving the first lens group along the optical axis, so that the focusing optical system can adapt to the measured object with different measuring distances, and meanwhile, the light beam with a larger wavelength and the light beam with a smaller wavelength can be focused on the preset point of the measured object together, so that the focusing optical system can be suitable for focusing the light beam with a cross-band ultra-large range together at the preset point, and the application range of the focusing optical system can be enlarged.

According to the invention, the cross-band ultra-large-range achromatic focusing optical system with a simple and compact structure can be provided, and a set of optical path system can be used for focusing a plurality of light beams with different wavelengths on the surface of a measured object at the same time, so that stronger return light information can be acquired, optical processing by utilizing the return light information is facilitated, and the focal length of the focusing optical system can be adjusted according to actual needs.

Drawings

The invention will now be explained in further detail by way of example only with reference to the accompanying drawings.

Fig. 1 is a schematic diagram illustrating a laser ranging system according to an example of the present invention.

Fig. 2A is a schematic diagram showing a first example of the focusing optical system to which the present example relates.

Fig. 2B is a schematic diagram showing that the first lens group movement changes the second distance according to the example of the present invention.

Fig. 2C is a schematic view showing a third lens group to which an example of the present invention relates.

Fig. 3A is a gaussian beam spot diagram showing the measurement light of embodiment 1 of the focusing optical system to which the present example relates at a measurement distance of 0.5 meters.

Fig. 3B is a gaussian beam spot diagram showing measurement light of embodiment 1 of the focusing optical system to which the present example relates at a measurement distance of 50 meters.

Fig. 3C is a gaussian beam spot diagram showing the indicator light of embodiment 1 of the focusing optical system to which the present example relates at a measurement distance of 0.5 meters.

Fig. 3D is a gaussian beam spot diagram showing the indicator light of embodiment 1 of the focusing optical system to which the present example relates at a measurement distance of 50 meters.

Fig. 3E is a graph showing the relationship between the spot diameters of the measurement light and the indication light and the measurement distance of embodiment 1 of the focusing optical system according to the example of the present invention.

Fig. 3F is a gaussian beam spot diagram showing that the return light is concentrated at the light source at a measurement distance of 0.5 meters in embodiment 1 of the focusing optical system to which the present example relates.

Fig. 3G is a gaussian beam spot diagram showing that the return light is concentrated at the light source at a measurement distance of 50 meters in embodiment 1 of the focusing optical system to which the present example relates.

Fig. 4A is a gaussian beam spot diagram showing the measurement light of embodiment 2 of the focusing optical system to which the present example relates at a measurement distance of 0.5 meters.

Fig. 4B is a gaussian beam spot diagram showing measurement light of embodiment 2 of the focusing optical system to which the present example relates at a measurement distance of 50 meters.

Fig. 4C is a gaussian beam spot diagram showing the indicator light of embodiment 2 of the focusing optical system to which the present example relates at a measurement distance of 0.5 meters.

Fig. 4D is a gaussian beam spot diagram showing the indicator light of embodiment 2 of the focusing optical system to which the present example relates at a measurement distance of 50 meters.

Fig. 4E is a graph showing the relationship between the spot diameters of the measurement light and the indication light and the measurement distance of embodiment 2 of the focusing optical system according to the example of the present invention.

Fig. 4F is a gaussian beam spot diagram showing that the return light is concentrated at the light source at a measurement distance of 0.5 m in embodiment 2 of the focusing optical system to which the present example relates.

Fig. 4G is a gaussian beam spot diagram showing that the return light is concentrated at the light source at a measurement distance of 50 meters in embodiment 2 of the focusing optical system to which the present example relates.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which are intended to be encompassed by the present invention, will be within the scope of the present invention by those of ordinary skill in the art based on the embodiments of the present invention without any inventive effort.

It should be noted that the terms "first," "second," "third," and "fourth," etc. in the description and claims of the present invention and in the above figures are used for distinguishing between different objects and not for describing a particular sequential order. Furthermore, the terms "comprise" and "have," as well as any variations thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those listed or inherent to such process, method, article, or apparatus but may optionally include other steps or elements not listed. In the following description, the same members are denoted by the same reference numerals, and overlapping description thereof is omitted. In addition, the drawings are schematic, and the ratio of the sizes of the components to each other, the shapes of the components, and the like may be different from actual ones.

In the present invention, the term "measuring light" may refer to a highly focused, high energy, high coherence laser beam generated by a laser in the field of laser technology applications, which may be used for accurate measurement and monitoring; the term "indicator light" may refer to a light beam used to indicate, illuminate or identify a specific area, typically the indicator light may be used to identify the measurement light; the term "return light" may refer to a beam of light reflected or scattered by the measurement light onto the object under test. In some examples, the return light may also refer to a light beam including information including measurement light and information indicative of light before entering the cross-band ultra-large-range achromatic focusing optical system according to the present invention, and after entering the cross-band ultra-large-range achromatic focusing optical system, the light beam including information indicative of light may be filtered or not participate in optical signal processing, at which time the return light may be a light beam including only measurement light information.

In the present invention, the term "achromatic lens" may be a lens group composed of a plurality of lenses, may be a lens system for reducing a chromatic dispersion effect, may be a broad concept, and is not limited to a specific lens system.

In the present invention, the term "d-ray" refers to a light beam having a wavelength of 588 nanometers.

Fig. 1 is a schematic diagram illustrating a laser ranging system 40 in accordance with an example of the present invention.

Referring to fig. 1, the broadband ultra-large-range achromatic focusing optical system 10 (may be simply referred to as focusing optical system 10) provided by the present invention may also be referred to as a focusing optical system, a focusing system, a multiband co-aperture focusing optical system, a focusing lens group, and a multiband focusing optical system. A second aspect of the present invention provides a laser ranging system 40, the laser ranging system 40 may also be referred to as a laser ranging system.

In some examples, the laser ranging system 40 may include a focusing optical system 10, and the focusing optical system 10 may be configured to receive the incidence of the measurement light 21 and the indication light 22 of the laser ranging system 40, form the incident light 24, and emit and co-focus the measurement light 21 and the indication light 22 on the object under test 30. In this case, on the one hand, the information of the stronger return light 25 can be obtained without the aid of a target, whereby the measuring speed of the laser distance measuring system 40 can be increased; on the other hand, the position of the measurement light 21 can be easily indicated by the indication light 22, and thus, the operation convenience and measurement accuracy of the laser ranging system 40 can be improved.

In some examples, laser ranging system 40 may include a fiber optic path system 26. In some examples, fiber optic path system 26 may be a wavelength division multiplexing device. In this case, the optical fiber optical path system 26 can multiplex the measurement light 21 and the indication light 22 on one optical fiber to transmit, thereby enabling the system to be compact.

In some examples, laser ranging system 40 may receive return light 25 reflected or scattered from a predetermined point P on the surface of object 30 under test and interfere with measurement light 21 to form interference wave 42. In some examples, the laser ranging system 40 may include a detector, and the interference wave 41 may be received by the detector 42 and a measured distance L (described later) of a preset point P on the surface of the measured object 30 is obtained based on the interference wave 41. In some examples, the detector may be a photodetector.

It should be noted that, the focusing optical system 10 provided in the present invention may be applied to other systems that need to focus a plurality of light beams with different wavelengths at the preset point P, such as a laser processing application system, and is not limited to the laser ranging system 40.

Fig. 2A is a schematic diagram showing a focusing optical system 10 according to an example of the present invention. Fig. 2B is a schematic diagram showing that the first lens group 11 moves to change the second distance D2 according to the example of the present invention. Fig. 2C is a schematic diagram showing the third lens group 13 according to an example of the present invention.

In some examples, the focusing optical system 10 may be configured to focus at least two light beams of different wavelengths at a preset point P (see fig. 2A), in other words, the focusing optical system 10 may receive the incidence of the at least two light beams of different wavelengths and emit and focus the at least two light beams of different wavelengths at the preset point P together.

Referring to fig. 2A, in some examples, the focusing optical system 10 may be configured to commonly focus the incident light 24 of the combination of the visible light and the invisible light at the preset point P, in other words, the visible light and the invisible light combination may be incident on the focusing optical system 10 and exit, and may be commonly focused at the preset point P. Thus, the visible light can be used as the indicating light 22, and the position of the invisible light (also referred to as the measuring light 21) can be indicated by the indicating light 22, so that the focusing optical system 10 can be conveniently applied to various laser application scenes.

In some examples, the focusing optical system 10 may receive the incidence of the visible light and the invisible light, respectively, and focus together at the preset point P, in other words, the visible light and the invisible light may each be independently incident to the focusing optical system 10, do not need to combine one-way light beams to enter the focusing optical system 10, and may focus together at the preset point P.

In some examples, the preset point P may be a position having a preset interval from the focusing optical system 10. In some examples, the preset point P may be a point located on the measured object 30, and may also be referred to as a measured point.

In some examples, the preset point P may be changed according to actual needs, in other words, the focal length of the focusing optical system 10 may be changed. Thus, it is possible to facilitate a scene in which different measurement distances L are applied.

In some examples, the measurement distance L may refer to the interval from the preset point P to the focusing optical system 10, that is, the interval from the measured point on the surface of the measured object 30 to the focusing optical system 10.

In some examples, the wavelength of the light beam incident on the focusing optical system 10 may be not less than 639 nanometers and not more than 1550 nanometers. In this case, the light beam having a larger wavelength and the light beam having a smaller wavelength can be focused together at the preset point P of the object 30 to be measured, and thus the focusing optical system 10 can be applied to the light beam having an ultra-large range across the wavelength band to be focused together at the preset point P, and the application range of the focusing optical system 10 can be expanded.

In some examples, the focusing optical system 10 may be configured to simultaneously enter two light beams having a wavelength of 639 nm (belonging to visible light) and a wavelength of 1550 nm (belonging to invisible light) into the focusing optical system 10 and to collectively focus at the preset point P. In this case, the wavelength of 1550 nm has a low absorption rate in the atmosphere, less loss when propagating in the air, better atmospheric transparency, and the 639 nm wavelength beam has a high contrast, contributing to the generation of a clear, high-quality image, whereby the use of the 1550 nm wavelength beam as the measuring light 21 is advantageous in obtaining a more accurate measurement result, and the 639 nm wavelength beam as the indicating light 22 can facilitate the indication of the position of the 1550 nm wavelength beam, thereby facilitating the practical operation.

In some examples, the focusing optical system 10 may be configured to simultaneously enter two light beams having a wavelength of 670 nm (belonging to visible light) and a wavelength of 1550 nm (belonging to invisible light) into the focusing optical system 10 and to collectively focus at the preset point P.

In some examples, combining the light beams of different wavelengths into one beam may be incident on the focusing optical system 10 on the optical axis 23 of the focusing optical system 10. In this case, the light beam is propagated along the optical axis 23, a spot of a larger brightness can be generated, the size and shape of the focused spot can be more easily controlled, and the design of the optical system can be simplified.

In some examples, the focusing optical system 10 may have a proximal end proximate to the emission location 20 of the light source and a distal end distal to the emission location 20 of the light source.

In some examples, a light source may refer to a device of an entity that emits a light beam. In some examples, the light source may include a light beam that emits light at a wavelength that is not visible. In some examples, the light source may include a light beam with an emission wavelength of 1550 nanometers. In some examples, the light source may include a light beam that emits light at a wavelength of visible light. In some examples, the light source may include a light beam that emits light having a wavelength of 639 nanometers or 670 nanometers.

In some examples, the light beam emitted by the light source propagates through the fiber optic system 26 to the emission location 20 of the light source, where it is incident upon the focusing optical system 10. In other words, the light beam emitted by the light source may be incident into the focusing optical system 10 at the emission position 20.

In some examples, the light beam emitted by the light source may propagate through an optical fiber to the emission location 20. In other words, the emission location 20 may be an end face of an optical fiber.

In some examples, the light beams of different wavelengths may be separately incident to the focusing optical system 10 through separate optical path systems.

In some examples, the first lens group 11 having positive optical power and the second lens group 12 having positive optical power may be disposed in order from the proximal end to the distal end along the incident light 24 direction along the common optical axis 23. In this case, both the first lens group 11 and the second lens group 12 have positive optical power, and the incident light 24 of the light source can be focused to the preset point P so as to optically operate or measure the preset point P.

Referring to fig. 2A, in some examples, first lens group 11 may include a first acromatic lens 111. In this case, when light beams of different wavelengths pass through the optical system, axial chromatic aberration is generated due to refraction of the light beams of different wavelengths with different refractive indexes, and quality and performance of the optical system are reduced, whereby the focusing optical system 10 can correct or reduce the refractive difference (i.e., chromatic aberration effect) of light rays of different wavelengths by using an achromatic lens, and focus the light beams of different wavelengths on the same focus as much as possible, thereby enabling more accurate focus focusing.

Referring to fig. 2A, in some examples, second lens group 12 may include a second acromatic lens 121. In this case, it is possible to further correct chromatic aberration of light beams of different wavelengths and ensure that light beams of different wavelengths converge on the same focal point.

Referring to fig. 2A, in some examples, the emission location 20 may be spaced a first distance D1 from the second lens group 12 on the optical axis 23. In some examples, the first lens group 11 and the second lens group 12 may be spaced apart by a second distance D2 on the optical axis 23. In some examples, the emission position 20 of the light source may be spaced from the first lens group 11 by a third distance D3.

In some examples, the first distance D1 may be a fixed value. In some examples, the sum of the second distance D2 and the third distance D3 may be the first distance D1 minus the total thickness of the first lens group 11. In other words, the sum of the second distance D2 and the third distance D3 may be a constant value.

In some examples, the first lens group 11 may be moved along the optical axis 23 to change the second distance D2. In this case, the first lens group 11 can function as a focus lens group, and focal length adjustment of the focusing optical system 10 can be achieved by moving the first lens group 11 along the optical axis 23, whereby the object 30 to be measured at different measurement distances L can be accommodated.

In some examples, the first distance D1 may be a fixed value and the first lens group 11 may be moved along the optical axis 23 to change the second distance D2. In this case, the first lens group 11 can function as a focusing lens group, the second lens group 12 can function as a fixed lens group, and by moving the first lens group 11 along the optical axis 23, focal length adjustment of the focusing optical system 10 can be achieved while the focusing position of the focusing optical system 10 can be adjusted without changing the position of the second lens group 12, whereby rapid focusing can be advantageously achieved.

In some examples, the absolute values of the amounts of change of the second distance D2 and the third distance D3 may be the same when the first lens group 11 moves along the optical axis 23.

In some examples, the preset point P may change as the second distance D2 changes. In other words, the focal length of the focusing optical system 10 can be changed by moving the first lens group 11 along the optical axis 23. In this case, when the measurement distance L is changed according to actual needs, the position of the condensed light spot formed by the condensed system 10 by the laser beams of a plurality of different wavelengths can be changed by moving the first lens group 11 along the optical axis 23, that is, according to the difference of the measurement distance L of the measured object 30, the laser beams of different wavelengths can be simultaneously condensed on the surface of the measured object 30 by moving the first lens group 11 through the condensed system 10, so that the focal length of the condensed system 10 can be adjusted.

In some examples, the ratio of the focal length of the first lens group 11 to the focal length of the second lens group 12 may be within a first preset range.

In some examples, the first preset range may be not less than 1/1.5 and not greater than 1.

In this case, when the ratio of the focal length of the first lens group 11 to the focal length of the second lens group 12 is smaller than the lower limit of the first preset range, in other words, in the focusing optical system 10, the focal length of the first lens group 11 is smaller than the focal length of the second lens group 12, the first lens group 11 assumes a larger optical power (the optical power is the inverse of the focal length), so that there is a case where the first lens group 11 generates a larger chromatic aberration and a spherical aberration, which causes an increase in aberration of the focusing optical system 10, and a decrease in quality of the focused light spot; in addition, when the light beams with different wavelengths pass through the first lens group 11 with larger focal power, the deflection angle difference of the light beams is increased, so that the difference of incidence angles when the light beams enter the second lens group 12 is correspondingly increased, and further, the aberration difference is increased, and under different measuring distances L, the light beams with different wavelengths are unfavorable to realize that the surface of the measured object 30 presents a better focusing state. In addition, the first lens group 11 having a larger optical power generally has a complicated structure, which may result in a larger volume and a larger weight of the focusing optical system 10.

When the ratio of the focal length of the first lens group 11 to the focal length of the second lens group 12 is greater than the upper limit of the first preset range, in other words, in the focusing optical system 10, the focal length of the first lens group 11 is greater than the focal length of the second lens group 12, the first lens group 11 assumes smaller optical power, and when light beams of different wavelengths pass through the first lens group 11 having smaller optical power, the first lens group 11 can provide only weaker aberration correction, thereby increasing the design complexity of the second lens group 12. At the same time, the focusing ability of the first lens group 11 is also reduced, in other words, the first lens group 11 needs to be moved a larger distance on the optical axis 23 to obtain a better focusing state, whereby, in order to obtain the same measurement distance L, the axial dimension of the focusing optical system 10 needs to be increased, or, in the case where the axial dimension of the focusing optical system 10 has been determined, the range of the measurement distance L will be reduced (i.e., the ranging range is limited). Also, in order to obtain the same focusing state, it is necessary to move the first lens group 11 a larger distance, in other words, the focusing speed is slowed, so that the requirement of quick focusing may not be satisfied.

Therefore, the ratio of the focal length of the first lens group 11 to the focal length of the second lens group 12 can be in favor of enabling the first lens group 11 and the second lens group 12 to obtain more reasonable focal power distribution respectively, on one hand, the two lens groups can be enabled to bear aberration correction function respectively, and the axial chromatic aberration effect is weakened, on the other hand, the focusing capability of the first lens group 11 can be improved conveniently, and a larger measuring distance L range and a quicker focusing speed can be obtained.

The first lens group 11 will be described in detail below with reference to the drawings.

In some examples, first acromatic lens 111 may be an acromatic lens. In some examples, the achromatic lens may perform chromatic aberration correction for different bands of light.

Referring to fig. 2A, in some examples, first acromatic lens 111 may include a first lens 1111 having negative optical power and a second lens 1112 having positive optical power. In this case, the first lens 1111 of negative power and the second lens 1112 of positive power can form a lens combination of a "positive and negative" structure, so that correction of chromatic aberration and spherical aberration can be advantageously achieved.

In some examples, the first lens 1111 may be a meniscus lens having negative optical power; the second lens 1112 may be a biconvex lens having positive optical power, and the first lens 1111 and the second lens 1112 may constitute a biconvex lens.

In some examples, the first lens 1111 may be flint glass and the second lens 1112 may be crown glass.

In some examples, the second lens 1112 may be an ultra-low dispersion lens. Thus, the spherical aberration difference caused by the two wavelengths of the ultra-large-range cross-band can be reduced, and the two wavelength light beams can be in a better focusing state on the surface of the measured object 30 under the same measuring distance L.

In some examples, the material of the second lens 1112 may be an ultra-low dispersion glass material H-FK95N.

In some examples, the focal length of first acromatic lens 111 measured under d-light may be no less than 90 millimeters and no greater than 140 millimeters. In this case, it can be advantageous for the second lens 1112 having positive optical power to be able to reduce the problem of spherical aberration in cooperation with the first lens 1111 having negative optical power, and for achieving that the focus positions of the light beams of different wavelengths tend to be uniform.

In some examples, the material refractive index of the first lens 1111 measured under d-light may be not less than 1.85 and not more than 1.95, and the abbe coefficient of the first lens 1111 measured under d-light may be not less than 30 and not more than 35; the refractive index of the material of the second lens 1112 measured under d-light may be not less than 1.4 and not more than 1.5, and the abbe coefficient of the second lens 1112 measured under d-light may be not less than 80 and not more than 95. In this case, the first lens 1111 has a larger material refractive index and a smaller abbe coefficient, that is, means that the first lens 1111 has a higher dispersion characteristic; the second lens 1112 has a smaller material refractive index and a larger abbe coefficient, which means that the second lens 1112 has a lower dispersion characteristic, so that the first lens 1111 has a larger material refractive index and a smaller abbe coefficient having a certain difference from the material refractive index and abbe coefficient of the second lens 1112, and thus, systematic chromatic aberration correction can be facilitated.

The second lens group 12 will be described in detail below with reference to the drawings.

In some examples, second lens group 12 may further include a third lens 122 having positive optical power, third lens 122 may be disposed on a side of second acromatic lens 121 near the proximal end. In this case, third lens 122 has positive power to further achieve focusing of the beam, while third lens 122 cooperates with second acromatic lens 121 to further facilitate power distribution of second lens group 12, with a reasonable power distribution to facilitate system spherical aberration correction.

In some examples, the third lens 122 may be a positive power meniscus lens.

In some examples, the focal length of the third lens 122 measured under d-light may be no less than 400 millimeters and no greater than 800 millimeters.

In some examples, the refractive index of the material of the third lens 122 measured under d-light may be not less than 1.9 and not more than 2. In some examples, the abbe coefficient of the third lens 122 measured under d-light may be not less than 15 and not more than 20.

In some examples, second acromatic lens 121 may include a fourth lens 1211 having negative optical power and a fifth lens 1212 having positive optical power. In this case, the fourth lens 1211 of negative power and the fifth lens 1212 of positive power can form a lens combination of a "positive and negative" structure, so that correction of chromatic aberration and spherical aberration can be advantageously achieved.

In some examples, fourth lens 1211 may be a meniscus lens with negative optical power; the fifth lens 1212 may be a biconvex lens having positive optical power, and the fourth lens 1211 and the fifth lens 1212 may constitute a biconvex lens.

In some examples, the focal length of second acromatic lens 121, measured under d-light, may be no less than 150 millimeters and no greater than 220 millimeters.

In some examples, the fourth lens 1211 may be flint glass and the fifth lens 1212 may be crown glass.

In some examples, the fifth lens 1212 may be an ultra-low dispersion lens. In some examples, the material of the fifth lens 1212 may be an ultra-low dispersion glass material H-FK95N.

In some examples, the focal length of third lens 122 measured under d-light may be no less than 400 millimeters and no greater than 800 millimeters, and the focal length of second acromatic lens 121 measured under d-light may be no less than 150 millimeters and no greater than 220 millimeters. In this case, the fifth lens 1212 having positive optical power can be advantageously matched with the fourth lens 1211 having negative optical power to alleviate the problem of spherical aberration, and the focusing positions of the light beams of different wavelengths can be advantageously made to be uniform; the third lens 122, the fourth lens 1211 and the fifth lens 1212 can be matched to more conveniently realize the optical power distribution of the second lens group 12, and the reasonable optical power distribution is beneficial to correcting the spherical aberration of the system.

In some examples, the refractive index of the material of the fourth lens 1211 measured under d-light may be not less than 1.9 and not more than 2, and the abbe coefficient of the fourth lens 1211 measured under d-light may be not less than 15 and not more than 25; the refractive index of the material of the fifth lens 1212 measured under d-light may be not less than 1.4 and not more than 1.5, and the abbe coefficient of the fifth lens 1212 measured under d-light may be not less than 80 and not more than 95. In this case, the fourth lens 1211 has a larger material refractive index and a smaller abbe coefficient, that is, means that the fourth lens 1211 has a higher dispersion characteristic; the fifth lens 1212 has a smaller material refractive index and a larger abbe coefficient, which means that the fifth lens 1212 has a lower dispersion characteristic, so that the fourth lens 1211 has a larger material refractive index and a smaller abbe coefficient having a certain difference from the material refractive index and abbe coefficient of the fifth lens 1212, and thus, systematic chromatic aberration correction can be facilitated.

In some examples, the refractive index of the material of the third lens 122 measured under d-light may be not less than 1.9 and not more than 2, and the abbe coefficient of the third lens 122 measured under d-light may be not less than 15 and not more than 20; the refractive index of the material of the fourth lens 1211 measured under d-light may be not less than 1.9 and not more than 2, and the abbe coefficient of the fourth lens 1211 measured under d-light may be not less than 15 and not more than 25; the refractive index of the material of the fifth lens 1212 measured under d-light may be not less than 1.4 and not more than 1.5, and the abbe coefficient of the fifth lens 1212 measured under d-light may be not less than 80 and not more than 95. In this case, the fourth lens 1211 has a larger material refractive index and a smaller abbe coefficient, that is, means that the fourth lens 1211 has a higher dispersion characteristic; the fifth lens 1212 has a smaller material refractive index and a larger abbe coefficient, which means that the fifth lens 1212 has a lower dispersion characteristic, so that the fourth lens 1211 has a larger material refractive index and a smaller abbe coefficient having a certain difference from the material refractive index and abbe coefficient of the fifth lens 1212, thereby being capable of facilitating the system chromatic aberration correction; the third lens 122, the fourth lens 1211 and the fifth lens 1212 can be matched to more conveniently realize the optical power distribution of the second lens group 12, and the reasonable optical power distribution is beneficial to correcting the spherical aberration of the system.

Referring to fig. 2C, in some examples, focusing optical system 10 may further include a third lens group 13, and third lens group 13, first lens group 11, and second lens group 12 may be disposed along incident light 24 in order along common optical axis 23.

In some examples, third lens group 13 may include a wave plate (also referred to as a phase retarder). In this case, when the focusing optical system 10 receives the return light 25 transmitted by the focusing optical system 10, some of the disturbance light beams can be filtered by the wave plate, for example, the indication light 22 can be filtered out, whereby the subsequent optical processing using the measurement light 21 can be facilitated.

In some examples, the wave plate may be a quarter wave plate. In some examples, the wave plate may be a half wave plate.

The focusing optical system 10 according to the present invention will be described below with reference to examples 1 and 2. Before explaining embodiment 1 and embodiment 2, parameter information common to embodiment 1 and embodiment 2 is first described.

In examples 1 and 2, the measuring light 21 was a light beam having a wavelength of 1550 nm, the indicating light 22 was a light beam having a wavelength of 639 nm, and the measuring light 21 and the indicating light 22 were simultaneously emitted from the end face of the optical fiber, and the optical fiber numerical aperture NA (Numerical aperture) was 0.14. In other words, the measurement light 21 and the indication light 22 enter the same optical fiber through the optical fiber optical path system 26, and are incident on the focusing optical system 10 at the emission position 20 of the light source.

The first lens group 11 is a positive power bi-cemented lens, and includes a first lens 1111 and a second lens 1112, wherein the first lens 1111 is a negative power meniscus lens, the second lens 1112 is a positive power biconvex lens, the first lens 1111 is near the proximal end, and the material of the second lens 1112 is an ultra-low dispersion glass material H-FK95N.

The second lens group 12 includes a third lens 122 and a cemented doublet (i.e., a second acromatic lens 121), the third lens 122 being a positive power meniscus lens, the cemented doublet including a fourth lens 1211 and a fifth lens 1212, the fourth lens 1211 being a negative power meniscus lens and near the proximal end, the fifth lens 1212 being a positive power biconvex lens and the material being an ultra-low dispersion glass material H-FK95N.

In embodiments 1 and 2, the interval from the end face of the optical fiber (i.e., the emission position 20 of the light source) to the second lens group 12 is constant, that is, the distance between the emission position 20 and the convex apex of the third lens 122 facing the proximal end (i.e., the first distance D1) is constant;

let the distance between the emission position 20 of the light source and the convex vertex of the first lens 1111 facing the light source be a third distance D3; the first lens group 11 is movable along the optical axis 23 to change the interval between the first lens group 11 and the second lens group 12, that is, the interval between the convex apex of the second lens 1112 facing the distal end and the convex apex of the third lens 122 facing the proximal end (i.e., the second distance D2). The first distance D1 is a fixed value, the second distance D2 and the third distance D3 are variable values and the sum of the total thicknesses of the second distance D2 and the third distance D3 and the first lens group 11 is equal to the first distance D1, the second distance D2 increases as the measured distance L increases, the third distance D3 decreases as the measured distance L increases, and the absolute values of the amounts of change of the second distance D2 and the third distance D3 are equal.

In embodiment 1 and embodiment 2, by adjusting the second distance D2, the measurement light 21 and the indication light 22 are focused at the preset point P of the surface of the object 30 under measurement at the measurement distance L after passing through the first lens 1111 and the second lens 1112 of the first lens group 11, the third lens 122, the fourth lens 1211 and the fifth lens 1212 of the second lens group 12 in this order. The measuring light 21 is reflected or scattered by the surface of the measured object 30 and then enters the focusing optical system 10 again, and the light beam (i.e. the return light 25) sequentially passes through the fifth lens 1212, the fourth lens 1211, the third lens 122, the second lens 1112 and the first lens 1111 and then is focused on the end face of the optical fiber, i.e. the emission position 20 of the light source.

By adjusting the second distance D2, the measurement distance L may be varied between 0.5 meters and 50 meters, in other words, the measurement light 21 and the indication light 22 may be simultaneously focused at the preset point P of the surface of the object 30 to be measured within 0.5 meters and 50 meters by the variation of the second distance D2. Also, with the second distance D2 kept unchanged, the return light 25 may be simultaneously focused at the emission position 20 of the light source.

The surface numbers, the radii of curvature, the surface intervals, the variable surface intervals, the refractive indices and abbe coefficients measured at the wavelength 588 nm beam, and the component names of the respective lenses in example 1 and example 2 are shown in tables 1 and 2.

Referring to fig. 2B, in embodiment 1 and embodiment 2, the first lens 1111 has a proximal-facing surface S1, the second lens 1112 has a proximal-facing surface S2 and a distal-facing surface S3, the third lens 122 has a proximal-facing surface S4 and a distal-facing surface S5, the fourth lens 1211 has a proximal-facing surface S6, the fifth lens 1212 has a proximal-facing surface S7 and a distal-facing surface S8, and the object 30 to be measured has a proximal-facing surface S9.

The unit of radius of curvature, face spacing, and variable face spacing is "millimeters". In tables 1 and 2, the plane interval refers to the interval of two adjacent planes. Taking table 1 as an example, the plane interval 2.1 mm corresponding to the plane number S1 refers to the interval between the vertices of the plane S1 and the plane S2, the plane interval 7.7 mm corresponding to the plane number S2 refers to the interval between the vertices of the plane S2 and the plane S3, the plane interval 3.0 mm corresponding to the plane number S4 refers to the interval between the vertices of the plane S4 and the plane S5, the plane interval 0.2 mm corresponding to the plane number S5 refers to the interval between the vertices of the plane S5 and the plane S6, the plane interval 2.5 mm corresponding to the plane number S6 refers to the interval between the vertices of the plane S6 and the plane S7, and the plane interval 6.0 mm corresponding to the plane number S7 refers to the interval between the vertices of the plane S7 and the plane S8.

In some examples, the face spacing may also be referred to as thickness.

The variable face spacing includes a third distance D3, a second distance D2, and a measured distance L. Taking table 1 as an example, 57.41 mm to 42.94 mm for the variable surface interval refer to the third distance D3, 28.13 mm to 42.60 mm for the variable surface interval refer to the second distance D2, and 500 mm to 50000 mm for the variable surface interval refer to the measured distance L.

[ example 1 ]

In example 1, the parameters of each lens are shown in table 1.

Table 1 lens parameters of example 1

Based on the data of table 1, it can be known by calculation by Zemax software that at the wavelength 588 nm beam, the focal length of the first lens group 11 (i.e., the first acromatic lens 111) composed of the first lens 1111 and the second lens 1112 is 108 mm, the focal length of the third lens 122 is 733 mm, and the focal length of the second acromatic lens 121 composed of the fourth lens 1211 and the fifth lens 1212 is 174 mm.

By calculation with the Zemax software, it can be derived from table 1 that the third distance D3 is 57.41 mm, the second distance D2 is 28.13 mm, and the first distance D1 is 85.54 mm when the measured distance L is 0.5 m. When the measured distance L is 50 meters, the third distance D3 is 42.94 millimeters, the second distance D2 is 42.6 millimeters, and the first distance D1 is 85.54 millimeters. The ratio of the focal length of the first lens group 11 to the second lens group 12 is about 1/1.31 and is within a first predetermined range.

Fig. 3A is a gaussian beam spot diagram showing the measurement light 21 of embodiment 1 of the focusing optical system 10 to which the present example relates at a measurement distance of 0.5 meters. Fig. 3B is a gaussian beam spot diagram showing the measurement light 21 of embodiment 1 of the focusing optical system 10 according to the example of the present invention at a measurement distance of 50 meters. Fig. 3C is a gaussian beam spot diagram showing the indicator light 22 of embodiment 1 of the focusing optical system 10 according to the present example at a measurement distance of 0.5 meters. Fig. 3D is a gaussian beam spot diagram showing the indicator light 22 of embodiment 1 of the focusing optical system 10 according to the present example at a measurement distance of 50 meters. Fig. 3E is a graph showing the spot diameters of the measurement light 21 and the indication light 22 of embodiment 1 of the focusing optical system 10 according to the example of the present invention as a function of the measurement distance L.

By referring to fig. 3A and 3C, it can be seen that the focus state of the spot of the measurement light 21 and the indication light 22 at the measurement distance L of 0.5 m is good, and the light intensity of the spot is large. By referring to fig. 3B and 3D, it can be seen that the focus state of the spot of the measurement light 21 and the indication light 22 at the measurement distance L of 50 meters is good, and the light intensity of the spot is large.

As can be seen from fig. 3E, as the measurement distance L increases, the measurement light 21 and the indicator light 22 maintain a good focused state all the time, the spot diameters of the focus of the measurement light 21 and the indicator light 22 are both smaller than 4 mm, and the absolute value of the difference in the spot diameters of the focus of the measurement light 21 and the indicator light 22 is not larger than 1 mm. Thus, the focusing optical system 10 of embodiment 1 can make the focusing states of the measurement light 21 and the indication light 22 at the same measurement distance L tend to be uniform.

Fig. 3F is a gaussian beam spot diagram showing that the return light 25 is concentrated at the light source at a measured distance of 0.5 meters in embodiment 1 of the focusing optical system 10 to which the present example relates. Fig. 3G is a gaussian beam spot diagram showing that the return light 25 is concentrated at the light source at a measured distance of 50 meters in embodiment 1 of the focusing optical system 10 to which the present example relates.

By referring to fig. 3F and 3G, the return light 25 with information of the measuring light 21 can likewise be focused at the emission location 20 of the light source at measuring distances L of 0.5 meter and 50 meter.

[ example 2 ]

In example 2, the parameters of each lens are shown in table 2.

Table 2 lens parameters of example 2

Based on the data of table 2, it can be known by calculation by Zemax software that at the wavelength 588 nm beam, the focal length of the first lens group 11 (i.e., the first acromatic lens 111) composed of the first lens 1111 and the second lens 1112 is 118 mm, the focal length of the third lens 122 is 426 mm, and the focal length of the second acromatic lens 121 composed of the fourth lens 1211 and the fifth lens 1212 is 196 mm.

By calculation with the Zemax software, it can be derived from table 2 that the third distance D3 is 59.32 mm, the second distance D2 is 24.52 mm and the first distance D1 is 83.84 mm when the measured distance L is 0.5 m. When the measured distance L is 50 meters, the third distance D3 is 43.9 millimeters, the second distance D2 is 39.94 millimeters, and the first distance D1 is 83.84 millimeters. The ratio of the focal length of the first lens group 11 to the second lens group 12 is about 1/1.15 and is within a first predetermined range.

Fig. 4A is a gaussian beam spot diagram showing the measurement light 21 of embodiment 2 of the focusing optical system 10 according to the example of the present invention at a measurement distance of 0.5 meters. Fig. 4B is a gaussian beam spot diagram showing the measurement light 21 of embodiment 2 of the focusing optical system 10 according to the example of the present invention at a measurement distance of 50 meters. Fig. 4C is a gaussian beam spot diagram showing the indicator light 22 of embodiment 2 of the focusing optical system 10 according to the present example at a measurement distance of 0.5 meters. Fig. 4D is a gaussian beam spot diagram showing the indicator light 22 of embodiment 2 of the focusing optical system 10 according to the present example at a measurement distance of 50 meters. Fig. 4E is a graph showing the relationship between the spot diameters of the measurement light 21 and the indication light 22 and the measurement distance L of embodiment 2 of the focusing optical system 10 according to the example of the present invention.

By referring to fig. 4A and 4C, it can be seen that the focus state of the spot of the measurement light 21 and the indication light 22 at the measurement distance L of 0.5 m is good, and the light intensity of the spot is large. By referring to fig. 4B and 4D, it can be seen that the focus state of the spot of the measurement light 21 and the indication light 22 at the measurement distance L of 50 meters is good, and the light intensity of the spot is large.

As can be seen from fig. 4E, as the measurement distance L increases, the measurement light 21 and the indicator light 22 maintain a good focused state all the time, the spot diameters of the focus of the measurement light 21 and the indicator light 22 are both smaller than 4 mm, and the absolute value of the difference in the spot diameters of the focus of the measurement light 21 and the indicator light 22 is not larger than 1 mm. Thus, the focusing optical system 10 of embodiment 2 can make the focusing states of the measurement light 21 and the indication light 22 at the same measurement distance L tend to be uniform.

Fig. 4F is a gaussian beam spot diagram showing that the return light 25 is concentrated at the light source at a measurement distance of 0.5 m in embodiment 2 of the focusing optical system 10 to which the present example relates. Fig. 4G is a gaussian beam spot diagram showing that the return light 25 is concentrated at the light source at a measured distance of 50 meters in embodiment 2 of the focusing optical system 10 to which the present example relates.

By referring to fig. 4F and 4G, the return light 25 with information of the measuring light 21 can likewise be focused at the emission location 20 of the light source at measuring distances L of 0.5 meter and 50 meter.

The present invention can enhance a cross-band ultra-large-range achromatic focusing optical system 10, the cross-band ultra-large-range achromatic focusing optical system 10 may have a proximal end near an emission position 20 of a light source and a distal end far from the emission position 20, a first lens group 11 having positive optical power and a second lens group 12 having positive optical power may be sequentially disposed along an incident light 24 direction from the proximal end to the distal end so as to be in common with an optical axis 23, the first lens group 11 may include a first achromat 111 and the second lens group 12 may include a second achromat 121; let the distance between the emission position 20 and the second lens group 12 on the optical axis 23 be a first distance D1, let the distance between the first lens group 11 and the second lens group 12 on the optical axis 23 be a second distance D2, the first distance D1 may be a constant value, and the first lens group 11 may be moved along the optical axis 23 to change the second distance D2; the ratio of the focal length of the first lens group 11 to the focal length of the second lens group 12 may be within a first preset range.

In the present invention, by employing an achromatic lens, it is possible to make laser beams of a plurality of different wavelengths tend to be focused on a uniform point at the same measurement distance L and to obtain a better focusing state, and the difference in diameter of the light spots formed by focusing of different wavelengths is small, whereby it is possible to make the concentration of light energy high, further enhance the return light 25 signal that is reflected or scattered back from the surface of the object under test 30, and when the measurement light 21 incident on the focusing optical system 10 is focused on the preset point P on the surface of the object under test 30 by the movement of the first lens group 11 along the optical axis 23, the return light 25 formed by reflection or scattering of the object under test 30 can be focused on the position where the emission position 20 of the light source is located, whereby the return light 25 with high light energy can be obtained, thereby facilitating the optical signal processing. And the position of the focusing light spot formed by the focusing system 10 by the laser beams with various different wavelengths can be changed by moving the first lens group 11 along the optical axis 23, namely, according to the difference of the measured distance L of the measured object 30, the laser beams with different wavelengths can be focused on the surface of the measured object 30 through the focusing system 10 by moving the first lens group 11, so that the focal length of the focusing system 10 can be adjusted. In addition, the present invention can make the structure of the focusing optical system 10 compact, can reduce the volume and weight, and can facilitate the realization of rapid focusing by reasonably distributing the optical powers of the first lens group 11 and the second lens group 12.

While the invention has been described in detail in connection with the drawings and examples thereof, it should be understood that the foregoing description is not intended to limit the invention in any way. Those skilled in the art can make modifications and variations to the present invention as required without departing from the true spirit and scope of the invention, and these modifications and variations fall within the scope of the invention.

Claims (10)

1. A cross-band ultra-wide-range achromatic focusing optical system having a proximal end near an emission location of a light source and a distal end distant from said emission location, a first lens group having positive optical power and a second lens group having positive optical power being disposed coaxially in order from said proximal end to said distal end along an incident light direction, said first lens group comprising a first achromatic lens and said second lens group comprising a second achromatic lens; setting a first distance between the emission position and the second lens group on the optical axis, setting a second distance between the first lens group and the second lens group on the optical axis, setting the first distance to be a constant value, and enabling the first lens group to move along the optical axis to change the second distance; the ratio of the focal length of the first lens group to the focal length of the second lens group is within a first preset range.

2. The cross-band ultra-large range achromatic focusing optical system of claim 1, wherein said first achromatic lens comprises a first lens having negative optical power and a second lens having positive optical power.

3. The cross-band ultra-large range achromatic focusing optical system of claim 2, wherein a focal length of said first achromatic lens measured under d-light is not less than 90 millimeters and not greater than 140 millimeters.

4. The cross-band ultra-large range achromatic focusing optical system according to claim 3, wherein a refractive index of a material of said first lens measured under d-light is not less than 1.85 and not more than 1.95, and an abbe coefficient of said first lens measured under d-light is not less than 30 and not more than 35; the second lens has a material refractive index of not less than 1.4 and not more than 1.5 measured under d-light, and an Abbe's number of not less than 80 and not more than 95 measured under d-light.

5. The cross-band ultra-large range achromatic focusing optical system of claim 1, wherein said second lens group further comprises a third lens having positive optical power disposed on a side of said second achromatic lens near said proximal end.

6. The cross-band ultra-large range achromatic focusing optical system of claim 5, wherein said second achromatic lens comprises a fourth lens having negative optical power and a fifth lens having positive optical power.

7. The cross-band ultra-large range achromatic focusing optical system of claim 6, wherein a focal length of said third lens measured under d-light is not less than 400 millimeters and not greater than 800 millimeters, and a focal length of said second achromatic lens measured under d-light is not less than 150 millimeters and not greater than 220 millimeters.

8. The cross-band ultra-large range achromatic focusing optical system according to claim 7, wherein a refractive index of a material of said third lens measured under d-light is not less than 1.9 and not more than 2, and an abbe coefficient of said third lens measured under d-light is not less than 15 and not more than 20; a material refractive index of the fourth lens measured under d-light is not less than 1.9 and not more than 2, and an abbe coefficient of the fourth lens measured under d-light is not less than 15 and not more than 25; the refractive index of the material of the fifth lens measured under d-light is not less than 1.4 and not more than 1.5, and the Abbe's number measured under d-light is not less than 80 and not more than 95.

9. The cross-band ultra-large range achromatic focusing optical system according to claim 1, wherein said first preset range is not less than 1/1.5 and not more than 1.

10. The cross-band ultra-wide-range achromatic focusing optical system according to claim 1, wherein said cross-band ultra-wide-range achromatic focusing optical system is configured to co-focus at least two light beams of different wavelengths at a preset point, said preset point changing with a change in said second distance, said light beams having wavelengths not less than 639 nanometers and not more than 1550 nanometers.