RU2498364C1 - Eyepiece with withdrawn pupil - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: eyepiece can be used in optical and optoelectronic devices which require withdrawal of the exit pupil, at least 2.5 times greater than the focal distance. The eyepiece has on beam path a negative doublet lens, a positive meniscus whose concave surface faces the object plane, a positive doublet lens whose negative lens is on the side of the object plane, a positive lens in form of a meniscus whose concave surface faces the exit pupil. The ratio of the inner and outer radii of the negative lens of the positive doublet lens, multiplied by the magnitude of the difference in the basic average variance coefficients of materials of the lenses of the positive doublet lens lies between 6 and 12, and the focal distance of the positive lens lies between 0.9 and 1.2 times the value of withdrawal of the exit pupil. The negative and positive lenses of the doublet lenses are made of the same material. Parameters of the optical system of the eyepiece satisfy relationships given in the claim.

EFFECT: reduced size and weight, high image quality owing to reduced chromatism of magnification and astigmatism in the image without reducing the angular field and aperture ratio of the eyepiece, providing a main beam path in the object space close to telecentric.

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Description

The invention relates to the field of optical instrumentation, namely, eyepieces with a remote pupil, and can be used in optical and optoelectronic devices, the operation of which requires a large removal of the exit pupil - not less than 2.5 times the focal length of the eyepiece, for example, to observe images from a microdisplay or screen of an optoelectronic converter in optoelectronic devices.

Known eyepieces with a distant pupil [Theory of optical systems / B.N. Begunov, N.P. Zakaznov, S.I. Kiryushin, V.I. Kuzichev. - M.: Mechanical Engineering, 1981., S. 219-220]. Typically, eyepieces with a distant pupil include eyepieces, if the pupil removal in them is equal to or slightly greater than the focal length of the eyepiece. The task of obtaining a large exit pupil removal, for example, in an optical system of a telescopic type, is solved by choosing the appropriate magnitude of the focal length of the eyepiece. At the same time, the required increase in the entire optical system is achieved by choosing the focal length of the lens and other optical components included in the optical system. However, in optical-electronic devices there are tasks of visual observation of the image, for example, on the microdisplay screen or the screen of the electron-optical converter, which require a large visible increase (small focal length of the eyepiece) and a large exit pupil. Such tasks require eyepieces, the removal of the exit pupil of which significantly exceeds the focal length of the eyepiece.

So, the disadvantage of these eyepieces - analogues is the small removal of the exit pupil compared with the focal length of the eyepiece. Because of this, taking into account the existing elemental base of the devices, their use is limited in optoelectronic devices, the operation of which requires a large exit pupil removal, for example 70 mm, while allowing the observation of the objective plane of the eyepiece with a visible magnification of at least 8 times with sufficient the magnitude of the angular size of the observed image required for the visual work of the operator.

The closest analogue to the claimed device by technical nature is an eyepiece with a remote pupil, the exit pupil in which exceeds the focal length by at least 2.5 times [Patent RU 2212700, 2003], containing a positive meniscus facing a concave surface to the subject planes, a positive doublet containing a positive and negative lens, and a positive lens, while the ratio of the values of the internal and external radii of the negative lens of the positive doublet, multiplied by the absolute value Well main difference average dispersion coefficient of the positive doublet lens materials is in the range from 6 to 12, the focal length of the positive lens is in the range from 0.9 to 1.2 times the value of the removal of the exit pupil.

All refracting surfaces in the closest analogue are spherical. The eyepiece has an angular field of 27 °, a relative aperture of 1: 3.5. The focal length of the eyepiece is 100 mm, the exit pupil is 259 mm. The eyepiece length along the axis from the subject plane to the last surface is 194 mm. Astigmatism at the edge of the field in the reverse is 2.2 mm, the relative chromatism of the increase at the edge of the field in the reverse is 0.6%. The mass of the eyepiece, calculated according to the parameters given in the patent, for the specified focal length is 8800 g, the volume of the glass of the lenses of the eyepiece is 2099 cm ³ .

In the closest analogue there are signs formulated in the form of relations between its parameters: the radius of the second along the rays from the subject of the refracting surface is in the range from minus 0.9 to minus 0.5 from the focal length of the eyepiece; the ratio of the radii of the first and second along the rays of the refracting surfaces of the positive meniscus is in the range from 5 to 8.

The disadvantages of the closest analogue are the large overall dimensions and mass, poor image quality due to the presence of astigmatism and increase chromatism.

In addition, in the analog lens, the main ray path in the space of the eyepiece objects is not telecentric, which can lead to a decrease in illumination in the image of off-axis points.

The large overall dimensions and weight of the analog eyepiece are due to the optical power and design (shape) of the lenses that form it. In the analogue, the relations between the focal lengths and the radii of curvature of individual lenses of the eyepiece are stated, which lead to the fact that to ensure technologically acceptable thicknesses along the edge of the eyepiece lens, they have a large thickness along the optical axis. This applies primarily to the positive meniscus and the positive doublet. As a result, the components of the eyepiece have a large volume and, as a result, a large mass.

Recalculation of the analog eyepiece according to the similarity coefficient to the focal length of 30 mm, made for further comparison with the proposed device, showed that in this case the glass volume of the analog eyepiece lenses in light diameters is 42 cm ³ , weight 170 g.

The presence of only one glued component when using two materials for all lenses in the optical scheme of the analog eyepiece allows the correction of only one chromatic aberration - position chromatism; at the same time, to eliminate the second chromatic aberration - increase chromatism - there are no correction parameters.

The optical forces and the shape of the lenses of the analogue eyepiece are such that there is astigmatism at the edge of the field of view and an increase in chromatism, which leads to a decrease in image quality during visual observation of the subject plane through the eyepiece. When recalculating the analog eyepiece by the similarity coefficient to the focal length of 30 mm, made for further comparison with the proposed device, it was found that the magnitude of astigmatism in the image space exceeds 1 diopters.

Thus, in the closest analogue it is not possible to achieve a decrease in overall dimensions and mass, as well as a decrease in the chromaticity of the increase and astigmatism (and, as a result, an increase in image quality) without a significant change in the structure of the optical system of the eyepiece, changes in the ratio between the optical forces and changes in the design included in him lenses and components.

The task to which the proposed device is aimed is to create an optical system of a small-sized eyepiece, which allows observing a flat object (for example, a microdisplay) with a significant removal of the exit pupil and the visible magnification and angular size of the observed image required for effective operator work.

The technical result achieved in solving this problem is to reduce the overall dimensions and mass, improve image quality by reducing the increase chromatism and astigmatism in the image without reducing the angular field and relative aperture of the eyepiece. Additionally, in the proposed device provides the main rays in the space of objects close to telecentric. With this course of light beams from the subject, the illumination in the image becomes more uniform, and the visible increase during diopter movement of the eyepiece also changes to a lesser extent, which increases the ergonomic characteristics of the proposed device.

The problem is solved, and the technical result is achieved by the fact that, in contrast to the closest analogue between the positive meniscus and the object plane, a negative doublet is additionally installed, the negative and positive lenses of which are made of the same materials as the negative and positive lenses of the positive doublet, a positive doublet oriented with its negative lens towards the objective plane of the eyepiece, the positive lens is made in the form of a meniscus facing a concave surface Strongly to the exit pupil of the eyepiece, and wherein the following relations hold:

where φ ₁ , φ ₂ , φ ₃ , φ ₄ are the relative optical powers of the negative doublet, positive meniscus, positive doublet, and positive lens, respectively;

R ₁ , R ₂ are the radii of the first and second along the rays from the subject plane of the refracting surfaces of the negative lens of the negative doublet;

R ₅ is the radius of the second along the rays from the subject plane of the eyepiece of the refracting surface of the positive meniscus;

R ₉ , R ₁₀ are the radii of the first and second along the rays from the subject plane of the eyepiece of the refractive surfaces of the positive lens;

Δν is the absolute value of the difference between the coefficients of the main average dispersion of the materials of the doublet lenses;

f ′ is the focal length of the eyepiece.

The introduction of a negative doublet between the positive meniscus and the subject plane, the negative and positive lenses of which are made of the same materials as the negative and positive lenses of the positive doublet, while satisfying relations (1) and (2), it is possible to correct the chromaticity of the increase and reduce the aberration load to a positive doublet and eliminate astigmatism in the optical system of the eyepiece without reducing the magnitude of the angular field and relative aperture of the eyepiece. The simultaneous introduction of these signs allows you to ensure the main rays in the space of the objects of the eyepiece, close to telecentric. Relation (2) is a feature that is similar in technical essence to the feature used in the closest analogue to characterize the doublet.

Orientation of the positive doublet by its negative lens towards the object plane of the eyepiece while satisfying relations (1) and (3) allows us to find such a design (shape) of the lenses of the positive doublet and the positive meniscus, in which the glass volume of the lenses decreases, and as a result, the thickness decreases along the axis and the mass of the eyepiece.

The implementation of a positive lens in the form of a meniscus facing a concave surface to the exit pupil of the eyepiece, together with the observance of relations (1) and (4), allows to eliminate astigmatism with large removal of the exit pupil, reduce the volume of the glass and, accordingly, reduce the weight of the eyepiece.

The combination of the proposed features allows us to solve the problem, the exclusion of any of them leads to the inability to implement the eyepiece with a remote pupil with the stated technical result.

The authors are not aware of eyepieces with a distant pupil, the removal of the exit pupil in which exceeds the focal length by at least 2.5 times, in which a combination of the indicated features corresponding to the proposed device would be realized.

The proposed solution is illustrated by the following graphic materials:

figure 1 is an optical diagram of an eyepiece with a remote pupil;

figure 2 is a graph of astigmatism;

figure 3 is a graph of the chromatism of the increase.

An eyepiece with a pupil removed, the exit pupil removal which exceeds the focal length by at least 2.5 times (Fig. 1) contains a negative doublet 1 located along the rays from the subject plane, a positive meniscus 2 facing the subject plane with a concave surface , a positive doublet 3, a positive lens 4, made in the form of a meniscus facing a concave surface to the exit pupil of the eyepiece. The negative doublet contains along the rays of the negative lens 5 and the positive lens 6. The positive doublet 3 contains along the rays of the negative lens 7 and the positive lens 8. The negative lenses 5 and 7 of the doublets are made of the same material. Positive lenses 6 and 8 of doublets are also made of the same material.

The ratio of the values of the inner (glued) and outer radii of the negative lens 7 of the positive doublet 3, multiplied by the absolute value of the difference of the coefficients of the main average dispersion of the materials of the lenses of the positive doublet, is in the range from 6 to 12. The focal length of the positive lens 4 is in the range from 0.9 up to 1.2 of the magnitude of the removal of the exit pupil. The relative optical powers of the negative doublet 1, the positive meniscus 2, the positive doublet 3, and the positive lens 4 satisfy relation (1). The ratio of the first and second along the rays from the object plane of the radii of the refracting surfaces of the negative lens 5 of the negative doublet 1, multiplied by the difference in the coefficients of the main average dispersion of the lens materials of the negative doublet 1, has an absolute value of less than 6 (satisfies relation (2)). The radius of the second along the rays from the subject plane of the refracting surface of the positive meniscus 2 satisfies relation (3). The ratio of the radii of the refractive surfaces of the positive lens 4 satisfy the relation (4).

The proposed device operates as follows. The radiation coming from each point (element, pixel) of the subject plane by the components 1–4 of the eyepiece is directed to the exit pupil, the role of which is played by the pupil of the observer’s eye located at a distance along the optical axis exceeding the focal length of the eyepiece by no less than 2.5 times. The components of the eyepiece 1-4 provide parallelism of the rays in the beams of rays emanating from each point of the subject plane. Moreover, the magnitude of the residual aberration divergence of these beams of rays is provided less than the resolution of the observer's eye or, when using the microdisplay as an object, the angular dimensions of the element (pixel) of the microdisplay. To compensate for the ametropia of the observer's eye, diopter movement is carried out jointly by components 1-4 along the optical axis of the eyepiece.

The implementation of an eyepiece with a distant pupil is confirmed by examples of a specific design: an eyepiece with a focal length of 30 mm and a pupil distance of 75.3 mm. The eyepiece is designed for visual observation of the image on the microdisplay screen with side dimensions of 12.78 × 9 mm (microdisplay 852 × 600, pixel pitch 0.015 mm). The eyepiece provides a visible magnification of 8X. The eyepiece parameters are shown in table 1. For ease of comparison with an analog, the parameters in table 1 are given for normalization by the focal length of 1.

Table 1 Parameters of a specific example of execution Parameter Value f ′ one s ^′ _{p ′} 2,51 2y 0.52 D ′ 0.285 φ ₁ -0.46 φ ₂ 0.41 φ ₃ 0.24 φ ₄ 0.34 ν ₅ 23 ν ₆ 54 ν ₇ 23 ν ₈ 54 R ₁ / R ₂ 0.09 R ₅ -1.3 R ₇ / R ₆ 0.24 R ₁₀ / R ₉ 10.7 L 1,53

The size of the object 2u and the focal length of the eyepiece f ′ determine the magnitude of the angular field behind the eyepiece 29 °, i.e. no less than in the closest analogue.

The diameter of the exit pupil D ′ and the focal length of the eyepiece f ′ define a relative aperture of 1: 3.5, i.e. the relative aperture is maintained the same as in the closest analogue.

The indices of the coefficients of the main average dispersion correspond to the positions of the lenses in figure 1.

All refracting surfaces of an example of a particular embodiment are spherical.

In table 1, the letter L denotes the distance from the subject plane to the last surface of the eyepiece for the adopted normalization.

Note that between the parameters of a specific example of the eyepiece, there are two relationships that are common features with the closest analogue:

- from the table it follows that (R ₇ / R ₆ ) Δν = 0.24 (54-23) = 7.56, i.e. lies in the range from 6 to 12;

- the focal length of the positive lens 4 is 1 / 0.34 = 2.94, i.e. falls into the range from 2.26 to 3, defined as a range from 0.9 to 1.2 of the magnitude of the exit pupil removal (0.9 × 2.51 = 2.26 and 1.2 × 2.51 = 3).

The remaining relationships between the parameters of the proposed device differ from the closest analogue.

As follows from table 1 and figure 1, the signs of the optical forces and the shape of the lenses correspond to the claimed device.

The values of the parameters of the example of a specific implementation justify the claimed distinctive features, formulated in the form of relations between the parameters of the device. So, the relative optical powers of the components 1-4 are related as follows: φ ₁ : φ ₂ : φ ₃ : φ ₄ = -0.46: 0.41: 0.24: 0.34, i.e. corresponds to relation (1). The ratio of the first and second along the rays from the object plane of the radii of the refracting surfaces of the negative lens 5 of the negative doublet 1, multiplied by the difference in the coefficients of the main average dispersion of the lens materials of the negative doublet 1, has an absolute value of 0.09 × (54-23) = 2 , 8, i.e. satisfies relation (2).

The radius of the second along the rays from the subject plane of the refracting surface of the positive meniscus 2 is minus 1.3, i.e. less than minus 1, and accordingly satisfies relation (3).

The ratio of the second and the first along the rays from the subject plane of the radii of the refracting surfaces of the positive lens 4 has, in the example of a specific embodiment, a value of 10.7, i.e. satisfies relation (4).

The length between the subject plane and the last surface of the eyepiece along the axis is 1.53 of the focal length of the eyepiece, which is 1.26 times less than in the closest analogue and indicates a decrease in overall dimensions.

The reduction of this length is the result of using in the example of a specific embodiment of the eyepiece lenses with a smaller thickness along the axis, the design of which is determined by the stated relations (1) - (4), as a result, the volume of the glass of the eyepiece lenses is reduced. A comparison with the closest analogue in terms of the volume of the glass material and the mass should be correctly carried out at the same focal lengths and proximity of the remaining characteristics (angular field, relative aperture, pupil removal). So, in the example of a specific design with a focal length of 30 mm, the volume of the glass of the lenses in terms of light diameters was 31 cm ³ and the mass was 115 g. The volume of the glass was reduced by 1.35 times, the weight was 1.5 times in comparison with the closest analogue.

Figure 2 shows a graph of sagittal (s) and meridional (m) astigmatic segments, and figure 3 is a graph of the chromatism of increasing Δу ′ in the field. The ordinates on these graphs indicate the angles of inclination of the main rays behind the eyepiece in degrees. Astigmatism does not exceed 0.4 diopters; the chromatism of the increase does not exceed 1.8 minutes for the edge of the field of view, which is 0.2%. Thus, the values of these aberrations are reduced in comparison with the closest analogue. The result was an increase in image quality within the field of view of the eyepiece, which is confirmed by the rms angular aberrations of wide oblique beams, the values of which for a point on the axis do not exceed 0.6 minutes, for the middle of the field of view - 1.5 minutes, for the edge of the field of view - 3 ,5 minutes.

In addition, from figure 1 it follows that the deviation of the main rays of the inclined beams of rays from the normal to the surface of the object is negligible. This helps to maintain a constant increase in diopter movement of the eyepiece and uniform illumination of the image, taking into account the radiation pattern of the microdisplay installed in the subject plane of the eyepiece in a specific embodiment.

Thus, in the example of a specific embodiment of the eyepiece, there is a technical result, the achievement of which the claimed device is aimed at: reducing overall dimensions and mass, improving image quality by reducing the chromaticity of increase and astigmatism in the image without reducing the angular field and relative aperture of the eyepiece. Additionally, the main rays in the space of objects close to telecentric are provided.

Specific values of the design parameters are provided by standard optimization, which is part of any modern optical program for calculating optical systems, using the indicated optical forces and materials.

Thus, the implementation of the technical advantages of the proposed eyepiece with a remote pupil allows you to create an optical system of a small-sized eyepiece that allows you to observe a flat object (for example, a microdisplay or the screen of an electron-optical converter in optoelectronic devices) with significant removal of the exit pupil and required for the operator to work effectively visible magnification and angular size of the observed image.

Literature

1. Theory of optical systems / B.N. Begunov, N.P. Zakaznov, S.I. Kiryushin, V.I. Kuzichev. - M.: Mechanical Engineering, 1981. - 432 p.

2. Patent RU 2212700, 2003.

Claims (1)

An eyepiece with a removed pupil, the removal of the exit pupil in which exceeds the focal length by at least 2.5 times, containing a positive meniscus facing a concave surface to the subject plane, a positive doublet containing positive and negative lenses, and a positive lens, while the ratio of values the inner and outer radii of the negative lens of the positive doublet, multiplied by the absolute value of the difference of the coefficients of the main average dispersion of the lens material of the positive doublet, is I am in the range of 6 to 12, the focal length of the positive lens is in the range of 0.9 to 1.2 of the magnitude of the exit pupil removal, characterized in that between the positive meniscus and the subject plane an additional negative doublet is installed, the negative and positive lenses of which are made of the same materials as the negative and positive lenses of the positive doublet, the positive doublet is oriented with its negative lens towards the objective plane of the eyepiece, the positive lens is made in the form meniscus facing a concave surface toward the exit pupil of the eyepiece, and wherein the following relations hold:
φ ₁ : φ ₂ : φ ₃ : φ ₄ = - (0.4 ÷ 0.6) :( 0.3 ÷ 0.5) :( 0.2 ÷ 0.4) :( 0.2 ÷ 0, four);

where φ ₁ , φ ₂ , φ ₃ , φ ₄ are the relative optical powers of the negative doublet, positive meniscus, positive doublet, and positive lens, respectively;
R ₁ , R ₂ are the radii of the first and second along the rays from the subject plane of the refracting surfaces of the negative lens of the negative doublet;
R ₅ is the radius of the second along the rays from the subject plane of the eyepiece of the refracting surface of the positive meniscus;
R ₉ , R ₁₀ are the radii of the first and second along the rays from the subject plane of the eyepiece of the refractive surfaces of the positive lens;
Δν is the absolute value of the difference between the coefficients of the main average dispersion of the materials of the doublet lenses;
f ′ is the focal length of the eyepiece.

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