RU81345U1 - LENS - Google Patents

Abstract

The utility model relates to optical instrumentation, namely, to lenses and can be used as a lens with image formation on a CCD matrix and a photodetector. The lens consists of four components and a spectrum splitting unit located between the third and fourth components. The first component is a positive lens glued from a biconvex and biconcave lens. The second component is the negative meniscus glued from biconvex and biconcave lenses. The third component is made in the form of a biconvex lens. The fourth component is made in the form of a negative meniscus facing a space of objects with a concave surface, mounted with the possibility of quotation movements along the optical axis, and is optically coupled to the face of the spectrodividing unit, which emits a spectral range of 500 nm ... 900 nm. The distance between the third and fourth components along the optical axis is at least 0.6 of the focal length of the lens, the sum of the optical forces of all components does not exceed 0.0014 mm ^-1 , the refractive indices of the materials of biconvex lenses of the first and second components are not less than 1.6, the refractive indices of the materials of biconcave lenses of these components are not less than 1.7, while the difference in the Abbe number in the absolute value of the lens materials of the first and second components does not exceed 26 and 17, respectively, and the refractive indices of the materials of the third and fourth components does not exceed 1.61. The lens provides the ability to simultaneously register images on a CCD and photodetector, has high image quality in the spectral range of wavelengths λ = 575 nm ... 850 nm due to an increase in modulation transmission coefficients across the entire field of view while maintaining a small lens length. 5 ill.

Description

The utility model relates to optical instrumentation, namely, to lenses and can be used as a lens with image formation on a CCD matrix and a photodetector.

A known lens [1] of five components and a spectrodivision unit, configured to transmit radiation in the spectral range of wavelengths from 500 nm to 900 nm and reflect radiation of a wavelength of 1067 nm or 1570 nm, located on the optical axis of the lens between the fourth and fifth components, the first component is made in the form of a negative two-glued meniscus facing a concave surface to the space of objects, the second component contains a positive lens, the third component is a negative meniscus facing that surface of the space image, the fourth component comprises a positive meniscus concave surface facing to the image space, the fifth component is in the form of a positive lens dvuskleennoy mounted for quotation displacement along the optical axis. This lens design provides high quality images in a wide spectral range, as well as the ability to simultaneously register images on a CCD and photodetector. The disadvantage of the lens is its long length: the distance from the first surface of the lens to the image plane is 1.7 of the focal length of the lens.

Closest to the proposed lens is a lens [2], consisting of four components. The first component is completed

in the form of a positive lens. The second component contains a negative meniscus glued from biconvex and biconcave lenses. The third component consists of a negative meniscus facing a concave surface to the image space. The fourth component contains a positive meniscus facing a concave surface to the space of objects.

This lens design has a short length not exceeding 1.1 of the focal length of the lens, as well as high quality images in the spectral range of 660 nm ... 920 nm. However, the disadvantage of the prototype is the impossibility of simultaneously registering the image on the CCD and photodetector.

The objective of the utility model is to create the possibility of simultaneously recording images on a CCD matrix and photodetector, improving image quality in the spectral range of wavelengths λ = 575 nm ... 850 nm by increasing the modulation transmission coefficients across the entire field of view while maintaining a small lens length.

The lens of four components located on the optical axis, the first component of which is a positive lens, the second component is a negative meniscus glued from a biconvex and biconcave lenses, unlike the prototype, contains a spectro-splitting unit located between the third and fourth components, the positive lens of the first component is glued from biconvex and biconcave lenses, the third component is made in the form of a biconvex lens, the fourth component is made in the form of a negative meniscus facing concave th surface to the object space, quotation mounted for movement along the optical axis and is optically coupled with a face spektrodelitelnogo blocks allocated spectral

the range is 500 nm ... 900 nm, while the distance between the third and fourth components along the optical axis is at least 0.6 of the focal length of the lens, the sum of the optical forces of all components does not exceed 0.0014 mm ^-1 , the refractive indices of the materials of biconvex lenses of the first and second components do not less than 1.6, the refractive indices of the materials of the biconcave lenses of these components is not less than 1.7, while the difference in the Abbe number in the absolute value of the lens materials of the first and second components does not exceed 26 and 17, respectively, and whether the refraction of the lens materials of the third and fourth components do not exceed 1.61.

The design of the first component, made in the form of a positive lens, glued from biconvex and biconcave lenses, as well as the use of biconvex lens materials of the first and second components with a refractive index of at least 1.6, the refractive index of the materials of the biconcave lenses of these components is at least 1.7 and the difference in absolute Abbe number the magnitude of the lens materials of the first and second components is not more than 26 and 17, respectively, and the refractive indices of the lens materials of the third and fourth components are not more than 1.61, provides correction of chromatic aberrations in the spectral range from 575 nm to 850 nm.

The execution of the second component in the form of a negative meniscus, facing the concave surface of the image space, and glued from a biconvex and biconcave lenses, the third component in the form of a biconvex lens, made it possible to correct spherochromatic aberrations and ensured high correction of axial beam aberrations.

The fourth component in the form of a negative meniscus facing a concave surface to the space of objects located at a distance of at least 0.6 of the focal length of the lens

from the last surface of the third component, the choice of the sum of the optical powers of all components not exceeding 0.0014 mm ^-1 allows you to correct the curvature of the image over the entire field, the aberration of the inclined beams and get a high image quality correction over the entire field of view.

The introduction of a spectrodividing unit located between the third and fourth components, made with the possibility of dividing the spectral range from 575 nm to 850 nm and the radiation wavelength of 1570 nm, allows the lens to be used both for image formation on a CCD matrix and for recording return radiation from a laser rangefinder at the site of the photodetector.

The fourth component of the lens is installed with the possibility of alignment movements along the optical axis, which allows it to be used effectively to focus the lens from 50 m to infinity when finding the plane of best installation on the CCD matrix and to compensate for the thermal disintegration of the lens.

In the proposed lens, the spectrodividing unit is designed in such a way that it reflects radiation in the spectral range from λ = 575 nm to λ = 850 nm and transmits radiation with a wavelength of λ = 1570 nm, the lens has a focal length of 130.5 mm, relative aperture 1: 2.6, input a pupil with a diameter of 50 mm coincides with the first surface of the lens. The polychromatic modulation transmission coefficients (T) for the spatial frequency N = 60 mm ^-1 at a point on the axis (y '= 0) of at least 0.76, at the edge of the field of view (y' = 3.2 mm) of at least 0.67.

Such values of the modulation transmission coefficients made it possible to obtain the energy concentration in the image of a point on a square

area equal to the pixel of the CCD matrix measuring 0.0085 × 0.0085 mm, at least 86% for the point on the axis and at least 79% for the edge of the field.

Figure 1 shows the optical scheme of the proposed lens.

Figure 2 shows a graph of the transverse spherical aberration of the lens.

Figure 3 shows the graphs of the aberrations of wide inclined beams of the meridional section of the angle of the field of view 2W = 3 degrees.

Figure 4 shows a graph of the calculated polychromatic frequency-contrast characteristic (T) for a point on the axis.

Figure 5 shows a graph of the calculated polychromatic frequency-contrast characteristic (T) for a point on the edge of the field of view 2W = 3 deg.

The frequency-contrast characteristics of the lens are calculated in accordance with table 1 of the spectral efficiency coefficients of the actinic radiation flux given below

Table 1 λ, μm 575 600 650 750 850 FROM 0.13 1.0 0.85 0.37 0.07

The lens (figure 1) consists of four components 1-4, a spectro-splitting unit 5 located between the third and fourth components, a light filter 6. The first component contains a positive double-glued lens 1, consisting of a biconvex and biconcave lenses, the optical power is 0.00265 mm ^-1 . The second component is a negative meniscus 2, facing a concave surface to the image space and glued from a biconvex and biconcave lenses, its optical power is -0.00591 mm ^-1 . The third component contains a biconvex lens 3, its optical power is 0.0131 mm ^-1 . The fourth component is made in the form of a negative meniscus 4 facing the space of objects with a concave surface, mounted with the possibility of quotation movements along the optical axis, while the adjustment movement of the component is not more than ± 1.2 mm, and its optical power is -0.00852 m ^-1 . The optical powers of the components were calculated for λ = 700 nm. The distance between the third and fourth components along the optical axis is 90 mm, which is 0.69 of the focal length of the lens. Between the third and fourth components there is a spectro-splitting unit 5, which reflects radiation in the spectral range λ = 500 nm ... 900 nm and transmits radiation with a wavelength of λ = 1570 nm. The lens contains a filter 6, highlighting the spectral range in accordance with table 1. When calculating the lens, the thickness of the protective glass of the CCD matrix is taken into account. The length of the lens from the first surface to the image plane of the CCD matrix along the optical axis is 150.4 mm, which is 1.15 of the focal length of the lens.

For lenses that work with a CCD, the parameters characterizing the image quality are the spectral region (from 575 nm to 850 nm), the relative aperture, the value of the modulation transmission coefficients at a frequency determined by the pixel size, and the energy concentration in the image of a point per square area equal to one pixel of the CCD.

The graphs of aberrations shown in FIGS. 2 and 3, as well as the graphs of a polychromatic frequency-contrast characteristic for a point on the axis and for the edge of the field of view, shown in FIGS. 4 and 5, confirm that the lens has good image quality over the entire field of view, which allows you to get an image of objects with low contrast (K = 0.1).

The design parameters of the objective lenses and the characteristics of glasses, where R is the radius of curvature of the lens surfaces, D is the distance between the lens surfaces, n _e is the refractive index of the lens glasses for the e line (λ = 546 nm), and ν _{e the} Abbe number for the e line are given in table 2.

table 2 R D n _e ν 119.95 10 1,66 50.81 -84.33 5 1.8138 25.17 659.2 3 64.71 9 1.6522 33.62 -129.72 5 1,7476 50.21 44.98 3 44.98 9.5 1.4879 84.07 -191.43 60 0 25 1.4846 66,2 0 5 -23.12 2 1,6071 37.77 -35.64 four 0 4.9 1,5183 63.83 0

The lens works as follows: a parallel beam of light with a field of view angle of 2W = 3 ° passes through the entrance pupil of the lens with a diameter of 50 mm, which coincides with the first surface, and, being refracted through the lens surfaces of components 1, 2, 3, enters the spectro-splitting unit 5 whose radiation with wavelengths λ = 575 nm ... 850 nm, reflected from the hypotenuse face of the spectrodividing unit, hits the component 4 of the lens, is refracted through its surfaces, filter 6, and is focused in the plane of the image, where the CCD matrix is located. A beam of rays with λ = 1570 nm passes through a spectro-fission unit 5 and focuses on the site of the photodetector.

The proposed lens has a higher image quality in the spectral range of wavelengths from 575 nm to 850 nm while maintaining a small lens length, compared with the prototype, and also has the ability to form images on a CCD, and to register the return radiation of the laser rangefinder on the site a photodetector located in the direction of transmission of the spectrum splitter.

Information sources

1. Patent BY No. 6385, publication 2001, MKI G02B 9/00

2. Patent RU No. 2175774, publication - prototype.

Claims (1)

A lens of four components located on the optical axis, the first component of which is a positive lens, the second component is a negative meniscus glued from a biconvex and biconcave lens, characterized in that it contains a spectrum splitting unit located between the third and fourth components, the positive lens of the first component is glued from a biconvex and biconcave lenses, the third component is made in the form of a biconvex lens, the fourth component is made in the form of a negative meniscus facing concave nth surface to the space of objects, is mounted with the possibility of quotation movements along the optical axis and is optically coupled to the face of the spectrodividing unit, which distinguishes the spectral range 500 nm ... 900 nm, while the distance between the third and fourth components along the optical axis is at least 0.6 the focal length of the lens, the sum of the optical forces of all components does not exceed 0.0014 mm ^-1 , the refractive indices of the materials of biconvex lenses of the first and second components are not less than 1.6, the refractive indices of the material the biconcave lenses of these components are at least 1.7, while the difference in the Abbe number in the absolute value of the lens materials of the first and second components does not exceed 26 and 17, respectively, and the refractive indices of the lens materials of the third and fourth components do not exceed 1.61.