JP2860221B2 - Stereoscopic projection lens - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens having a stereoscopic projection characteristic, that is, a stereoscopic projection lens.

[0002]

2. Description of the Related Art As an imaging optical system telecentric in both object and image spaces, for example, as shown in FIG.
There is known a telescope-type optical system which is spaced apart by f1 + f2). This optical system has the feature that the magnification does not change even if the object distance and image distance change, and due to its nature, it can be easily coupled to other telecentric imaging optical systems without using a relay lens. Therefore, it is widely used.

Further, this telecentric imaging optical system is constituted by combining two lenses 1 and 2 having a normal image height characteristic (the image height is proportional to the tangent of the incident angle) as described above. An image similar to the object can be obtained.

[0004]

However, in the telecentric imaging optical system configured as described above, due to its configuration, the aperture of the lens 1 on the object side is made larger than the size of the object 3 and the lens on the image side It is necessary to make the diameter of the lens 2 larger than that of the image 4. for that reason,
In order to handle a larger object 3 or a larger image 4, it is necessary to use large-aperture lenses 1 and 2, and the focal length of the lenses 1 and 2 is inevitably increased. It may be long. Further, in order to keep the aperture constant and shorten the overall length, it is necessary to increase the aperture ratio of the lens. In this case, however, the number of lenses constituting the lens increases, and problems such as deterioration of aberrations tend to occur.

Therefore, in order to solve the above-mentioned problem, it is considered to use, for example, a rotating parabolic mirror (hereinafter simply referred to as a parabolic mirror) instead of the lens 1 as the optical element on the object side. (FIG. 14). Here, the use of the parabolic mirror 5 means that the parabolic mirror 5 has a large aperture ratio and is capable of converging a parallel light beam at its focal point with one reflecting surface with no aberration. This is because it has characteristics.

However, in order to obtain an image similar to an object by a telescope system using a parabolic mirror 5 as an object-side optical element and a lens 6 as an image-side optical element, the lens 6 must be It is required to have a special image height characteristic called stereoscopic projection (or polar projection) instead of the normal image height characteristic (the image height is proportional to the tangent of the incident angle). The reason will be described below.

[0007] In the image forming optical system shown in FIG.
The parabolic mirror 5 and the lens 6 are spaced from each other so that the focal point of the lens 6 coincides with the focal point of the lens 6 at a predetermined position 7. Here, in order to obtain an image similar to the object, the ray heights of the incoming and outgoing light fluxes LB1, LB3 are set to hi, hi, respectively.
´

[0008]

(Equation 1)

It is necessary that the relationship represented by ## EQU1 ## is always satisfied, but the imaging optical system of FIG. 14 satisfies this condition (Equation 1).

For example, as shown in FIG. 14, when a light beam LB1 parallel to the optical axis Z at an object height (light height from the optical axis Z) hi enters the parabolic mirror 5, the parabolic mirror 5 The reflected light beam LB2 passes through a position 7 separated by a focal distance f5 from the parabolic mirror 5 at an angle .theta.i. At this time, from the optical characteristics of the parabolic mirror 5,

[0011]

(Equation 2)

The relationship expressed by the following holds. Then, the light beam LB2 passing through the position 7 is

[0013]

(Equation 3)

Where f6 is the focal length of the lens 6, hi
′ Is incident on a lens 6 having an image height characteristic (so-called stereoscopic projection characteristic) represented by an image height (light height from the optical axis Z). Therefore, the image height hi 'of the light beam LB3 emitted from the lens 6 can be obtained by substituting Equation 2 into Equation 3.

[0015]

(Equation 4)

Here, m 1 is represented by the magnification of the imaging optical system. Thus, Equation 1 is satisfied only when the lens 6 has the stereoscopic projection characteristic.

As can be seen from the above analysis, the parabolic mirror 5
By configuring a telecentric imaging optical system with the lens having a stereoscopic projection characteristic (stereoscopic projection lens) 6, it is possible to cope with a large object or image. However, even if the paracentric mirror 5 and the lens 6 immediately constitute a telecentric imaging optical system, it cannot be applied to actual use.
This is because if a lens having a stereoscopic projection characteristic is simply manufactured, a desired telecentric characteristic cannot be obtained due to large aberration.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a stereoscopic projection lens in which aberration is corrected in a telecentric state.

[0019]

SUMMARY OF THE INVENTION claims 1 invention, from the object side to the image side, a name Ru stereographic projection lens by arranging the first to third lens groups in this order, wherein the first lens The group is formed by joining a first lens having negative power disposed on the object side and a second lens having positive power disposed on the image side, and forming the second lens group with a convex surface on the image side. The third lens group is composed of a fourth lens having a positive power, and the radius of curvature of the cemented surface of the first and second lenses is r.
2 and the refractive indices of the first and second lenses are n1 and n2, respectively.

[0020]

(Equation 5)

[0021]

(Equation 6)

Is satisfied. And things
Meniscus ren with negative power with convex surface facing body side
Lens on the object side with respect to the front focal point of the stereoscopic projection lens.
It has been added.

According to a second aspect of the present invention, there is provided an image processing apparatus, comprising:
Stereoscopic projection in which the first to third lens groups are arranged in this order
A shadow lens, wherein the first lens group is disposed on an object side.
A first lens having negative power,
And a second lens having a positive power.
The two lens groups have positive power with the convex surface facing the image side
A third lens group , wherein the third lens group is a biconvex cemented lens in which a fifth lens having a positive power and a sixth lens having a negative power are cemented;
The radius of curvature of the cemented surface of the first and second lenses is r2.
And the refractive indices of the first and second lenses are respectively n1
, N2, the inequalities of Equations 5 and 6 are satisfied.
And the refractive indices of the fifth and sixth lenses are respectively n5
, N6, the inequality

[0024]

(Equation 7)

Is satisfied.

[0026]

[0027]

According to the first aspect of the present invention, the first lens unit is formed by joining a first lens having a negative power disposed on the object side and a second lens having a positive power disposed on the image side. And a second lens group consisting of a third lens having a positive power and a convex surface facing the image side, and a third lens group consisting of a fourth lens having a positive power are arranged in this order from the object side to the image side. It is arranged to form a stereoscopic projection lens. And in this stereoscopic projection lens, Expressions 5 and 6 are satisfied. Hereinafter, the significance of Equations 5 and 6 will be described.

When a ray from the object side enters the stereoscopic projection lens through its front focal point, an angle between the incident ray and the optical axis of the stereoscopic projection lens is θ, and the image height at that time is y0, When the focal length of the stereoscopic projection lens is f, an ideal stereoscopic projection lens satisfies the relational expression y0 = 2ftan (θ / 2) regardless of the value of the angle θ. However, in a stereoscopic projection lens which is simply composed of the first to third lens groups as described above and does not consider Equations 5 and 6 at all, there is a tendency that Δ <0 regardless of the value of the angle θ. Here, Δ represents the image height error, that is, the error of the image height y ′ of the actual lens from the ideal image height as a percentage.

[0029]

(Equation 8)

## EQU1 ## Therefore, as can be seen from Expression 8, the fact that the image height error Δ is negative means that an image formed by the stereoscopic projection lens is formed closer to the optical axis.

The conditions for correcting the image height error Δ to be close to zero are Expressions 5 and 6. That is,
By satisfying the expression (5), the incident angle of the light beam incident on the cemented surface of the first and second lenses constituting the first lens group increases, and by satisfying the expression (6), the refractive index of the first lens The difference between the first lens and the second lens is increased, and a larger exit angle is obtained. Therefore, the image formed by the stereoscopic projection lens tends to move away from the optical axis, the image height error Δ approaches zero, and a stereoscopic projection imaging lens having image height characteristics that are close to ideal can be obtained.

Further, the negative power with the convex surface facing the object side
The meniscus lens having
It is additionally arranged on the object side with respect to the side focus. Add this way
Of the front side focus by the action of the negative meniscus lens
The angle of incidence of light passing through the stereoscopic projection lens is small.
It becomes. Therefore, the lens elements that constitute the stereoscopic projection lens
The individual power of the child can be relatively small,
This also increases the degree of freedom in design. As a result, good optical
A stereoscopic projection lens having characteristics can be obtained.

In the invention of claim 2, the same as the invention of claim 1 is provided.
Having first and second lens groups having the same configuration,
Group has a fifth lens with positive power and a fifth lens with negative power
Bi-convex cemented lens that is joined with the sixth lens
Be composed. Equation 7 is satisfied. like this
Then, the fifth lens and the sixth lens are joined to form a joint surface.
The direction of the light beam can be finely adjusted.
Wear. The arrangement of the fifth and sixth lenses is particularly limited.
It is not fixed, and the fifth lens and the sixth lens are placed in order from the object side.
Or vice versa. Also the number
By satisfying 7, the joint surface has a divergent effect.
Light from the entire biconvex cemented lens
Can be kept small. As a result, the third lens group
Beam exit angle without increasing the beam deflection angle due to
Can be fine-tuned on the image side of the stereoscopic projection lens.
Telecentricity can be improved.

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment FIG. 1 is a diagram showing a first embodiment of a stereoscopic projection lens which is a premise of the present invention. In this stereoscopic projection lens, the first to third lens groups 10, 20, 30 are arranged in this order from the object side (the left hand side in the figure) to the image side (the right hand side in the figure). The first lens group 10 is formed by joining a first lens L1 having a negative power disposed on the object side and a second lens L2 having a positive power disposed on the image side. The second lens group 20 is composed of a third lens L3 having a positive power with the convex surface S3 facing the image side.
Further, the third lens group 30 is constituted by a fourth lens L4 having a positive power.

Table 1 is a table showing lens data of the stereoscopic projection lens according to the first embodiment.

[0036]

[Table 1]

In this table (and Tables 2 to 6 to be described later), each symbol is defined as follows. That is, ri ... the radius of curvature of the i-th lens surface counted from the object side, and di ... the i-th lens surface counted from the object side and (i +
1) The distance between the lens surfaces on the optical axis Z with respect to the first lens surface, n: the refractive index of each lens (glass) with respect to the wavelength λ of the laser beam used.

In the first embodiment, the focal length f of the stereoscopic projection lens, the F number FNO, the wavelength λ of the laser beam used, and the distance on the optical axis Z from the entrance pupil to the first lens surface. d0 and angle of view 2ω are f = 10.00, FNO = 30.00, λ = 780 nm, and d0 = 4.8529, respectively.
40, 2ω = 56.2 °.

FIG. 2 is a graph showing the lens characteristics of the stereoscopic projection lens according to the first embodiment. In FIG. 1 (and FIGS. 4, 6, 8, 10, and 12 described later), FIG. 1A is a graph showing spherical aberration. Also, FIG.
Is a graph showing astigmatism, wherein a solid line S indicates a sagittal image plane, and a broken line M indicates a meridional image plane. FIG. 3C is a graph showing image height characteristics (image height error Δ).
FIG. 6D is a graph showing telecentricity, which is represented by the inclination angle of the light beam emitted from the stereoscopic projection lens with respect to the image height y '.

FIG. 3 is a diagram showing a modification of the stereoscopic projection lens according to the first embodiment. The basic configuration of this modification is the same as the stereoscopic projection lens of FIG.

Table 2 is a table showing lens data of the stereoscopic projection lens according to this modification.

[0042]

[Table 2]

In this modification, the focal length f of the stereoscopic projection lens, the F number FNO, the wavelength λ of the laser beam, the distance d0, and the angle of view 2ω are f = 10.00, FNO = 30.00, λ = 780 nm, d0, respectively. = 3.2522
09, 2ω = 56.2 °.

FIG. 4 is a graph showing the lens characteristics of the stereoscopic projection lens according to this modification.

B. Second Embodiment FIG. 5 is a diagram showing a second embodiment of the stereoscopic projection lens according to the present invention. In this stereoscopic projection lens, the first to third lens groups 10, 20, 30 are arranged in this order from the object side (the left hand side in the figure) to the image side (the right hand side in the figure). The first lens group 10 is formed by joining a first lens L1 having a negative power disposed on the object side and a second lens L2 having a positive power disposed on the image side. The second lens group 20 is composed of a third lens L3 having a positive power with the convex surface S3 facing the image side.
Further, the third lens group 30 is a biconvex lens formed by joining a fifth lens L5 having a positive power disposed on the object side and a sixth lens L6 having a negative power disposed on the image side. Is composed of a cemented lens L56.

Table 3 is a table showing lens data of the stereoscopic projection lens according to the second embodiment.

[0047]

[Table 3]

In the second embodiment, the focal length f of the stereoscopic projection lens, the F-number FNO, the wavelength λ of the laser beam, the optical axis Z from the entrance pupil to the first lens surface.
The upper distance d0 and the angle of view 2ω are f = 10.00, FNO = 30.00, λ = 780 nm, and d0 = 3.1067, respectively.
70,2ω = 56.2 °.

FIG. 6 is a graph showing the lens characteristics of the stereoscopic projection lens according to the second embodiment.

FIG. 7 is a view showing a modification of the stereoscopic projection lens according to the second embodiment. This modification is different from the stereoscopic projection lens in FIG. 5 in that the third lens unit 30 has a sixth lens L6 having a negative power disposed on the object side and a positive lens disposed on the image side. The fifth embodiment is constituted by a biconvex cemented lens L65 formed by joining the fifth lens L5, and the other basic structure is the same as that of the stereoscopic projection lens of FIG.

Table 4 is a table showing lens data of the stereoscopic projection lens according to this modification.

[0052]

[Table 4]

In this modified example, the focal length f of the stereoscopic projection lens, the F number FNO, the wavelength λ of the laser beam, the distance d0, and the angle of view 2ω are f = 10.00, FNO = 30.00, λ = 780 nm, d0, respectively. = 3.2679
80,2ω = 56.2 °.

FIG. 8 is a graph showing lens characteristics of a stereoscopic projection lens according to this modification.

C. Third Embodiment FIG. 9 is a diagram showing a third embodiment of the stereoscopic projection lens according to the present invention. In this stereoscopic projection lens, a meniscus lens 40 having a negative power and having a convex surface S1 facing the object side is added to the first embodiment described above. As shown in the figure, the meniscus lens 40 has an object with respect to a front focal point FP of a lens system including the first to third lens groups 10, 20, and 30 (the same configuration as the stereoscopic projection lens according to the first embodiment). Located on the side. The other configuration is the same as that of the first embodiment.

Table 5 is a table showing lens data of the stereoscopic projection lens according to the third embodiment.

[0057]

[Table 5]

In the third embodiment, the focal length f of the stereoscopic projection lens, the F-number FNO, the wavelength λ of the laser beam, the optical axis Z from the entrance pupil to the first lens surface.
The upper distance d0 and the angle of view 2ω are f = 10.00, FNO = 30.00, λ = 780 nm, and d0 = −7.985, respectively.
820, 2ω = 56.2 °.

FIG. 10 is a graph showing the lens characteristics of the stereoscopic projection lens according to the third embodiment.

FIG. 11 is a view showing a modification of the stereoscopic projection lens according to the third embodiment. The basic configuration of this modification is the same as the stereoscopic projection lens of FIG.

Table 6 is a table showing lens data of the stereoscopic projection lens according to this modification.

[0062]

[Table 6]

In this modification, the focal length f of the stereoscopic projection lens, the F-number FNO, the wavelength λ of the laser beam, the distance d0, and the angle of view 2ω are f = 10.00, FNO = 30.00, λ = 780 nm, d0, respectively. = -7.517
473, 2ω = 56.2 °.

FIG. 12 is a graph showing lens characteristics of a stereoscopic projection lens according to this modification.

[0065]

As described above, according to the first aspect of the present invention, the first lens having negative power disposed on the object side and the second lens having positive power disposed on the image side are provided. Are combined to form a first lens group, a third lens group having a positive surface with a convex surface facing the image side constitutes a second lens group, and a fourth lens group having a positive power forms a third lens group. In addition, when the radii of curvature of the cemented surfaces of the first and second lenses are r2 and the refractive indices of the first and second lenses are n1 and n2, respectively, the inequality r2>0n1-n2> 0. 20 is satisfied, so that a stereoscopic projection lens whose aberration is corrected in a telecentric state can be obtained.

Further, the negative power with the convex surface facing the object side
Lens in front of the stereoscopic projection lens
Since it is located on the object side with respect to the side focal point,
Optical characteristics of the laser can be improved.

According to the second aspect of the present invention, the first aspect of the present invention is provided.
It has first and second lens groups having the same configuration as
Lens group, a fifth lens having a positive power and a negative lens
Bi-convex joint lens formed by joining a sixth lens having
And the bending of the fifth and sixth lenses.
Since the inequality n5 <n6 is satisfied when the folding ratios are n5 and n6, respectively, the image side of the stereoscopic projection lens
Telecentricity can be further improved
You.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of a stereoscopic projection lens which is a premise of the present invention.

FIG. 2 is a graph showing lens characteristics of the stereoscopic projection lens according to Example 1.

FIG. 3 is a diagram showing a modification of the stereoscopic projection lens according to the first example.

FIG. 4 is a graph showing lens characteristics of a stereoscopic projection lens according to the modification.

FIG. 5 is a view showing a second embodiment of the stereoscopic projection lens according to the present invention.

FIG. 6 is a graph showing lens characteristics of a stereoscopic projection lens according to Example 2.

FIG. 7 is a diagram showing a modification of the stereoscopic projection lens according to the second example.

FIG. 8 is a graph showing lens characteristics of a stereoscopic projection lens according to the modification.

FIG. 9 is a diagram showing a third embodiment of the stereoscopic projection lens according to the present invention.

FIG. 10 is a graph showing lens characteristics of a stereoscopic projection lens according to Example 3.

FIG. 11 is a view showing a modification of the stereoscopic projection lens according to the third example.

FIG. 12 is a graph showing lens characteristics of a stereoscopic projection lens according to the modification.

FIG. 13 is a diagram showing a conventional telecentric imaging optical system.

FIG. 14 is a diagram showing an example of a telecentric imaging optical system using a paraboloid of revolution.

[Explanation of symbols]

 Reference Signs List 10 first lens group 20 second lens group 30 third lens group 40 meniscus lens L1 first lens L2 second lens L3 third lens L4 fourth lens L5 fifth lens L6 sixth lens S1, S3 convex surface

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G02B 13/22 G02B 13/16

Claims (2)

(57) [Claims] To 1. A image side from the object side, a first to third lens stereoscopic projection lenses ing arranged in this order a group
Te, the first lens group is constituted by joining a second lens having a first lens having a negative power disposed on the object side, a positive power disposed on the image side, the second lens The group includes a third lens having a positive power with a convex surface facing the image side, and the third lens group includes a fourth lens having a positive power, and a junction of the first and second lenses. When the radius of curvature of the surface is r2 and the refractive indices of the first and second lenses are n1 and n2, respectively, the inequality r2> 0 n1 -n2> 0.20 is satisfied, and the negative surface with the convex surface facing the object side is satisfied. With power of
The varnish lens is positioned at the front focal point of the stereoscopic projection lens.
A stereoscopic projection lens additionally provided on the object side . 2. A first to a third lens from an object side to an image side.
A stereoscopic projection lens composed of lens groups arranged in this order.
Te, the first lens group, a negative power disposed on the object side
And a positive lens disposed on the image side.
And a second lens unit that has a positive power with a convex surface facing the image side.
A third lens having the third lens group is constituted by the positive fifth lens and a negative biconvex shape of the cemented lens formed by cementing a sixth lens having a power having a power, moreover, the Radius of curvature of the cemented surface of the first and second lenses
Let r2 be the refractive index of the first and second lenses.
When n1 and n2 are satisfied, respectively , the inequality r2> 0 n1 -n2> 0.20 is satisfied, and when the refractive indices of the fifth and sixth lenses are n5 and n6, respectively, the inequality n5 <n6 is satisfied. A stereoscopic projection lens characterized by the following .