JP2002014283A - Infrared ray zoom lens or infrared ray multifocal lens, infrared ray imaging system and panoramic observation optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an IR zoom lens or IR multifocal lens or IR imaging, system which has an aspherical surface shape at a prescribed surface with five-group constitution and has high imagery performance over the entire part of a visual field and over the entire part of respective magnification ranges and is small in F value and compact and to obtain a panoramic observation optical system which can be arranged with a compact image rotating correction prism. SOLUTION: The lens described above is disposed, successively from an object side, with a first lens group G1 which has a focusing function and is positive, a second lens group G2 which has a variable power function and is negative, a third lens group G3 which has a compensation function by accompanying variable power and is positive, a fourth lens group G4 which has a function to form an intermediate image and is positive, a fifth lens group G5 for relay forming the intermediate image on a detecting surface 1, a mask 2 and a Dewar window 3. The fourth lens group G4 and the fifth lens group G5 respectively have at least one aspherical surfaces. The lens satisfies the condition equations (1) 0.5<f/f1-4<1.0 and (2) 2.5<f4/f5<3.0.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared zoom lens or an infrared multifocal lens, an infrared imaging system, and a panoramic observation optical system, and more particularly, to an infrared imaging system and a panoramic observation optical system equipped with an infrared observation means. The present invention relates to an infrared zoom lens or an infrared multifocal lens.

[0002]

2. Description of the Related Art Conventionally, an infrared zoom lens used in an infrared optical system is disclosed in, for example, US Pat. No. 4,411,488.
No. 4,632,498, No. 4,659,171, No. 4,676,58
No. 1 in each specification, and in Japan, Patent Gazette No. 2,512,881
And many have been proposed, as disclosed in U.S. Pat. No. 2,701,445. These are infrared zoom lenses of the afocal type, and are used by scanning with a mirror or the like arranged at the exit pupil position.

In recent years, an infrared lens which can be used for a two-dimensional area sensor or the like has been proposed. For example, there is an infrared zoom lens disclosed by the present applicant which has already been disclosed in Japanese Patent Application Laid-Open No. 10-213746. The infrared zoom lens is bright and has good imaging performance over the entire field of view and the entire zoom region, and is adapted to an area sensor.

An infrared camera lens system disclosed in Japanese Patent Application Laid-Open No. H11-287951 is also an infrared optical system compatible with an area sensor. However, this lens system does not have a lens configuration that can perform focusing by moving the lens but can change the focal length.

[0005]

There are the following demands for an infrared zoom lens or an infrared multifocal lens suitable for use in a two-dimensional area sensor or the like. It is required to meet the demand. That is, a zoom or multifocal lens is desired to have a higher resolution over a wider field of view and over the entire field of view and each magnification area. Also, as an infrared lens, since it is an optical system that collects heat radiated from a subject, that is, infrared rays as a characteristic of an infrared lens and forms an image on a detector surface, it has an F value to improve NETD (noise equivalent temperature difference). , That is, a bright lens is required. In addition, there is a strong demand for a more compact lens as the camera itself becomes smaller.

The present invention has been made in view of the above circumstances, and provides a compact infrared zoom lens or infrared multifocal lens which has high imaging performance over the entire field of view and the entire magnification area, and has a small F value. The purpose is to do so. It is another object of the present invention to provide an infrared imaging system and a panoramic observation optical system including the infrared zoom lens or the infrared multifocal lens.

[0007]

An infrared zoom lens or an infrared multifocal lens according to the present invention comprises, in order from the object side, a first lens group having a focusing function and a positive refractive power;
A second lens group having a zooming function and having a negative refractive power, a third lens group having a function of compensating a focal position changed by zooming and having a positive refractive power, and having at least one aspheric surface A fourth lens group for forming an intermediate image and a fifth lens group having at least one aspheric surface for relay-imaging the intermediate image on a detector surface; It is characterized by the following.

It is preferable that the zoom lens is configured to satisfy the following conditional expressions (1) and (2). _{0.5 <f / f 1-4 <1.0} ...... (1) 2.5 <f 4 / f 5 <3.0 ...... (2) where, f: total focal at the telephoto end distance f _1-4: first at the telephoto end synthesis of a lens group to the fourth lens group focal length f _4: the focal point of the fourth lens group distance f _5: focal length of the fifth lens group

Further, a mask for limiting an aperture is arranged between the fifth lens group and the detector surface,
Further, it is more preferable that all the light beams transmitted through the mask for the effective size of the detector surface are transmitted through an optical system from the first lens group to the fifth lens group.

[0010] The infrared zoom lens or the infrared multifocal lens according to the present invention is characterized in that the fourth zoom lens or the infrared multifocal lens according to the temperature change.
By moving the positions of some or all of the lenses in the lens group or the fifth lens group by a predetermined amount along the optical axis, fluctuations in the focal position caused by temperature changes when the field of view is changed are reduced. More preferably, it is configured to compensate.

Further, the first lens group is composed of a meniscus lens having a positive refractive power made of silicon and a lens having a negative refractive power made of germanium, and the second lens group is made of germanium. It is preferably composed of a lens having a positive refractive power made of a material and a lens having a negative refractive power made of silicon and used in a wavelength band of 3 to 5 μm.

An infrared imaging system according to the present invention includes the infrared zoom lens or the infrared multifocal lens having the above-described configuration, and imaging means for imaging an image using the infrared zoom lens or the infrared multifocal lens. It is.

[0013] The panoramic observation optical system according to the present invention comprises the infrared zoom lens or infrared multifocal lens, a turning mirror turned around an axis, a mirror turning mechanism for turning the turning mirror, An image rotation correction prism that corrects the rotation of the image due to the rotation of the rotation mirror, a prism rotation mechanism that rotates the image rotation correction prism, and an image whose rotation is corrected by the image rotation correction prism Image rotation means, and the image rotation correction prism is disposed between the fourth lens group and the fifth lens group.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. FIGS. 1 and 2 are diagrams showing a configuration of an infrared imaging system including an infrared zoom lens according to a first embodiment of the present invention. This infrared imaging system includes the infrared zoom lens according to the first embodiment and an imaging unit. Be prepared. FIG. 1 is a diagram showing a lens position at a telephoto end, and FIG. 2 is a diagram showing a positional relationship of each lens group of the infrared zoom lens at a telephoto end (A), an intermediate position (B), and a wide-angle end (C). is there. First, an embodiment of an infrared zoom lens according to the present invention will be described with reference to FIGS. Note that the embodiment of the infrared multifocal lens of the present invention also conforms to the embodiment of the zoom lens unless otherwise specified.

This infrared zoom lens is an optical system for forming an image of an object at an image forming position P on the detection surface 1 of the image pickup means. The infrared zoom lens has a focusing function and a positive refractive power in order from the object side. A first lens group G ₁ having a variable power function and a second lens group G ₂ having a negative refractive power, and a third lens having a function of compensating a focal position changed by the variable power and having a positive refractive power. Group G
₃ , a fourth lens group G ₄ having a function of forming an intermediate image and having a positive refractive power, and a final detection surface 1 for the intermediate image
The fifth lens group G ₅ in order to relay imaging is configured to disposed. In the figure, X indicates an optical axis. As shown in FIG. 2, during zooming, the first, fourth and fifth lens groups G ₁ , G ₄ and G ₅ are fixed, while the second and third lens groups are fixed. G ₂ and G ₃ are movable. The zooming is performed by moving the second lens group G ₂ in the optical axis X direction, and the third lens group G ₃ is moved in the optical axis X direction. It is configured to correct the imaging position by moving.

[0016] Incidentally, Table each lens group in the fourth lens group G ₄ and the fifth lens group G ₅ are each has at least one aspherical surface, the aspherical shape by an aspherical shape formula shown below Is done.

[0017]

(Equation 1)

This first lens group G₁To the fourth lens group G
₄The configuration up to the commonly known positive / negative / positive type
This is a four-unit zoom lens. But here, the fourth lens
Group G ₄And the fifth lens group G₅In each lens group
At least one aspheric surface corrects aberrations of the peripheral light beam
The spherical aberration, coma, and field curvature.
Compensation over the entire field of view and each magnification area.
High resolution can be obtained. Furthermore, these aspheric surfaces
The lens system and the overall length of the lens
A compact infrared zoom lens can be obtained.

The infrared zoom lens is configured to satisfy the following conditional expressions (1) and (2). These conditional expressions (1) and (2) are conditional expressions for achieving both compactness and high imaging performance of the infrared zoom lens. _{0.5 <f / f 1-4 <1.0} ...... (1) 2.5 <f 4 / f 5 <3.0 ...... (2) where, f: total focal at the telephoto end distance f _1-4: first at the telephoto end Lens group G ₁ to 4
Combined focal length f from the lens group _{G 4 4:} the focal length f ₅ of the fourth lens group _{G 4:} focal length of the fifth lens group _{G 5}

If the lower limit of conditional expression (1) is not reached, the total length of the lens will be long, making it difficult to compactly configure the entire optical system. If the upper limit is exceeded, it becomes difficult to correct coma aberration and off-axis aberrations such as field curvature. The conditional expression (1) also includes a fifth lens group G ₅ is a relay lens group, what can be described as indirect defines the power ratio to the entire system, this numerical range, the fourth lens group G ₄ second predetermined space is secured between the fifth lens group G _5. Details will be described later, and the fourth lens group G ₄ 5
Between the lens group G ₅ is also a position where the intermediate image is formed by the fourth lens group G ₄ according to the configuration of the infrared zoom lens of the present embodiment, the infrared zoom lens of the present embodiment panoramic viewing optical system When incorporated as part of
This space is suitable for arranging the image rotation correction prism of the panoramic observation optical system.

Conditional expression (2) is a condition for making the outer diameter of the lens compact and for reducing coma and distortion. If the upper and lower limits are exceeded, it becomes difficult.

[0022] Further, between the detection surface 1 from the fifth lens group G ₅ of the infrared zoom lens, a mask 2 for limiting the opening, and Dewar window (window of the infrared camera is an imaging means) 3 Is arranged. As shown, and is configured to be transmitted through the optical system from the first lens group G _1, all luminous flux transmitted through the mask 2 in the fifth lens group G ₅ with respect to the effective size of the detection surface 1. The mask 2 is an aperture mask generally called a “cold shield”. That is, as a detector used in an infrared imaging system, a hybrid method (InSb, Hg
Cooling types such as CdTe) and Schottky barrier type (using PtSi) and non-cooling types using thermopiles or microbolometers are known. In this configuration, an aperture mask called a “cold shield” is disposed in front of the detector. This "cold shield" has the function of removing the effects of thermal radiation from sources other than the subject, and the infrared optics used in such cooling-type detectors that are sensitive to such noises have their exit pupils marked as "cold". By removing the influence of heat radiation from other than the subject by matching the “shield”, a high-quality infrared image can be obtained.

In the conventional infrared zoom lens disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 10-213746, the exit pupil of the optical system coincides with the "cold shield" disposed in front of the detection surface of the infrared camera. However, it was difficult to remove the influence of heat radiation from other than the subject. The infrared camera lens system disclosed in Japanese Patent Application Laid-Open No. H11-287951, which is also a conventional example, is not configured as a zoom lens, but a "cold" disposed in front of the detection surface of the infrared camera. The optical system has an exit pupil substantially coincident with the “shield” position.

Under such circumstances, it has been desired to develop a variable magnification infrared lens capable of making the exit pupil substantially coincide with the position of the "cold shield" in front of the detection surface. However, it is generally difficult to correct aberrations in an optical system having a configuration in which the exit pupil substantially coincides with the position of the “cold shield”, and it has been extremely difficult to develop a variable magnification lens having both performance and compactness.

As described above, this embodiment satisfies this demand as a compact infrared zoom lens which has good aberration correction, is bright, has a high resolution, and has a small size. the light beam transmitted through the mask 2 is transmitted through all optical system from the first lens group G ₁ to the fifth lens group G _5, "cold shield"
The exit pupil can be almost matched to the position, and the aperture matching is 10
0%. That is, in the effective area of the detection surface 1, a high-quality infrared image with little noise is not affected by unnecessary heat radiation other than heat energy radiated from the subject (for example, heat radiation from the lens barrel). Obtainable.

In addition, the infrared zoom lens according to the present invention
Is the fourth lens group G according to the temperature change. ₄Or 5th
Group G₅Position some or all of the lens along the optical axis.
To change the field of view by moving
Compensation for focal position fluctuations caused by temperature changes
It is configured to be.

Silicon or germanium used as a lens material of the infrared optical system has a characteristic that the refractive index greatly fluctuates due to a temperature change. Therefore, when the temperature changes due to the environment at the time of use, the focal position of the infrared optical system fluctuates, which is likely to cause a problem. Even with infrared optics,
In the case of a fixed focus lens, the solution can be achieved by providing a margin in the adjustment range of the focusing lens in anticipation of the effect of temperature change. However, in the case of a zoom lens or an infrared multifocal lens, it is necessary to compensate for a shift in the focal position due to a temperature change after compensating for a change in the focal position due to zooming. That is, if the focal position fluctuates due to a change in temperature from the reference temperature, for example, it is necessary to solve the problem that the focal position is shifted at the wide-angle end even if focusing is possible at the telephoto end.

In accordance with the present embodiment, moved by a predetermined amount the position along the optical axis of the fourth lens group G ₄ or a part or all of the lenses of the fifth lens group G ₅ when the temperature changes By doing so, it is possible to obtain a high-quality infrared image without a focus shift in a wide temperature range. For example, in the infrared zoom lens of Example 1 described later, the focal position at the wide-angle end fluctuates by 0.05 mm in the object direction when the temperature rises by 10 ° C. This infrared zoom lens
2 with temperature rise of 10 ° C in the fifth lens group G ₅ object-side
By 0.19mm moved to single lens L ₈ and L ₉ the object side, and is configured to be able to compensate for variations in the focal position due to temperature.

The direction and amount of movement of the lens moved in response to the temperature change are input in advance to a storage device associated with the optical system in accordance with the temperature change from the reference temperature. , According to the temperature change based on this information,
It is desirable to move these lenses by a lens moving mechanism.

Furthermore, the infrared zoom lens according to the present invention, constituted by a lens in which the first lens group G ₁ has a negative refractive power of the meniscus lens and germanium having a positive refractive power using silicon as a material and material It is, and a lens having a negative refractive power second lens group G ₂ is the lens and the silicon material having a positive refractive power germanium and materials. With such a configuration, the present embodiment is an infrared zoom lens particularly suitable for a wavelength band of 3 to 5 μm.

Firstly the first lens group G ₁ is a material having a small wavelength dispersion of the refractive index as germanium case of a lens for the wavelength band of 8 to 12 .mu.m, also consist of a single convex meniscus lens It is possible. However, in the wavelength band of 3 to 5 μm, it is composed of two lenses having different wavelength dispersions, a meniscus lens having a positive refractive power made of silicon and a lens having a negative refractive power made of germanium. , Spherical aberration and axial chromatic aberration are well corrected. This makes it possible to realize an infrared zoom lens that is bright and suitable for use in a short wavelength band of 3 to 5 μm.

[0032] Next, the second lens group G _2, when a lens for a wavelength band of 8~12μm is often composed of two negative refractive power of the lens to the material zinc sulfide and germanium. However, in the wavelength band of 3 to 5 μm, chromatic aberration of magnification can be corrected well by using a lens having a positive refractive power made of germanium and a lens having a negative refractive power made of silicon.
Thereby, as a lens for a wavelength band of 3 to 5 μm, in each zooming region by a zoom lens or a multifocal lens,
A high-quality infrared image with little image quality deterioration can be obtained.

The infrared zoom lens or the infrared multifocal lens described above is provided with an image pickup means for picking up an image by the infrared zoom lens or the infrared multifocal lens, such as a real-time infrared image pickup device using a two-dimensional array sensor. It is useful because it can be used as an infrared imaging system, so that a captured image can be observed on a separate monitor, information can be shared by a plurality of observers, and the image can be recorded.

As an example of such an infrared imaging system, an embodiment of a panoramic observation optical system having an infrared zoom lens or an infrared multifocal lens according to the present invention will be described. FIG. 10 is a schematic diagram showing the configuration of this panoramic observation optical system, which is a panoramic observation optical system including an infrared multifocal lens according to Example 3 described later.

In this panoramic observation optical system, the observer turns a panoramic turning section made up of a turning mirror 16 around an axis by a mirror turning mechanism (not shown) as shown by an arrow A. It is possible to observe all directions. In addition, the rotating mirror 16 is configured to be able to descend as shown by an arrow B. A light beam from the outside is transmitted through the window glass 15 for dust prevention, which is rotated integrally with the rotation mirror 16, and is reflected by the rotation mirror 16 to be an infrared optical system for image formation according to the present invention. It is led to the infrared zoom lens 10. This optical path is between the fourth lens group G ₄ and the fifth lens group G ₅ in the infrared multifocal lens 10, the image rotation correction prism 14 is disposed. The image of the object is formed by the infrared multifocal lens 10 through the mask 12 and the Dewar window 13 at the image forming position P of the image pickup device 11 of the infrared camera 17 as the image pickup means. In the figure, X
Indicates the optical axis.

Here, the image rotation correcting prism 14 is a prism that performs an odd number of internal reflections and makes the incident optical axis and the outgoing optical axis coaxial. When the rotating mirror 16 is rotated by θ degrees in the horizontal direction, it is interlocked therewith. And a prism rotating mechanism (not shown) that rotates θ / 2 (degrees) around the optical axis. Since the image rotation correction prism 14 rotates, the image captured by the imaging unit at the subsequent stage does not rotate regardless of the rotation of the rotation mirror 16, so that the image is rotated even on the monitor displaying the image. Without observing, the observer can observe an image in any direction with the same vertical feeling as the observation target.

As an example of the image rotation correction prism 14, a Panchang prism made of silicon transmitting infrared rays is provided in the panoramic observation optical system shown in FIG. As shown in the figure, since the optical path is bent inside the Pechan prism, the effect that the total length of the optical system can be shortened can also be obtained.

The panoramic observation optical system may be provided with an infrared zoom lens according to the present invention instead of the infrared multifocal lens. Hereinafter, the operation and effect of the panoramic observation optical system of the present embodiment including the infrared multifocal lens according to the present invention will be described, but the operation and effect when the zoom lens according to the present invention is used unless otherwise specified. This also applies to this.

In a panoramic observation optical system, a method of correcting the rotation of an image due to the turning of a mirror of a head in conjunction with a prism having an image rotation correction function has been conventionally performed. However, in the conventional panoramic observation optical system using a general infrared camera, the image rotation correction prism tends to be large, and thus there is a problem that the entire observation optical system is also increased in size. For example, a configuration of a conventional general infrared panoramic observation optical system is shown in FIG. In this panoramic observation optical system, if the names and functions of the respective members described in the above-described panoramic observation optical system according to the present embodiment are the same, the reference numerals are assigned with the same lower digits. Detailed description is omitted.

In this conventional panoramic observation optical system,
The image rotation correction prism 24 is arranged between the rotation mirror 26 and the infrared optical system 20 for imaging. Therefore, the light beam incident on the image rotation correction prism 24 is in a state of parallel light having a large light beam diameter as shown in the figure, and the image rotation correction is performed with this light beam diameter as it is. For this reason, the prism 24 needs to have a reflection surface having a size commensurate with the light beam diameter, and it is inevitable to increase the size of the prism 24 itself. As the prism 24 to be inserted at this position, it is possible to insert a prism 24 having a substantially triangular prism shape as shown in the drawing, which is smaller than the Pechan prism because it is in a parallel light beam. However, in spite of this, the prism 24 becomes quite large, and as a result, the entire device becomes large.

Conventionally, in the panoramic observation optical system for infrared rays, the development of the optical system 20 for image formation has been proceeding in the direction of its own compactness. Such a problem has not been considered together with the problem that the image rotation correction prism 24 becomes large.

However, even if the optical system 20 is downsized, if the image rotation correction prism 24 is large, it is difficult to downsize the panoramic observation optical system as a whole. The panoramic observation optical system according to the present embodiment is based on the idea that the prism 14 is arranged in the optical path of the infrared optical system 10, completely changing the idea from the conventional one. In the conventional infrared panoramic observation optical system, the configuration in which the prism 24 is arranged in the optical path of the infrared optical system 20 as in the present invention is not assumed at all. This is evident from the fact that it is difficult to secure a space in the optical path of the infrared optical system 20 aiming at compactness, which is sufficient to arrange the prism 24 having a size that allows observation of a certain visual field range. It is.

The panoramic viewing optical system of this embodiment is provided with the infrared multifocal lens 10 according to the present invention, image rotation correcting prism between its fourth lens group G ₄ and the fifth lens group G ₅ 14 can be arranged. That is,
Infrared multifocal lens 10 according to the present invention has a structure connecting the once focus between the fourth lens group G ₄ as described above fifth lens group G _5. Therefore, by arranging the image rotation correction prism 14 at this position, this prism 1
As shown in FIG. 4, a convergent light beam having a smaller light beam diameter than the parallel light beam is incident on the light source 4, focuses while passing through the prism 14, and is emitted as a divergent light beam. Furthermore, as shown in the lens configuration diagram in a fourth two lenses and two lenses with similar lens of the lens system is less differ not magnitude of the object side of the fifth lens group G ₅ lens group G ₄ In some cases, a small prism can be used as the image rotation correction prism 24 disposed at this position. Incidentally, the fourth lens group G ₄ is the interval between the fifth lens group G _5, the lens unit from the first lens group G ₁ to the fourth lens group G ₄ relay magnification of the fifth lens group G ₅ According to the above-mentioned conditional expression (1) to be defined, it is preferable that the distance is set to a predetermined value.

By providing the infrared zoom lens or the infrared multifocal lens according to the present invention as described above, the panoramic observation optical system according to the present embodiment is configured to reduce the size of the prism by narrowing the field of view. On the other hand, the image rotation correction prism 14 can be downsized while having the same field of view as the conventional one, so that the panoramic observation optical system as a whole can have a compact configuration.

[0045]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments 1 to 3 of an infrared zoom lens or an infrared multifocal lens of the present invention will be described below with reference to the drawings.
Will be described.

<Embodiment 1> FIGS. 1 and 2 are views showing a configuration of an infrared imaging system provided with an infrared zoom lens according to the present embodiment. It is provided with imaging means. FIG. 1 is a diagram showing a lens position at a telephoto end, and FIG. 2 is a diagram showing a positional relationship of each lens group of the infrared zoom lens at a telephoto end (A), an intermediate position (B), and a wide-angle end (C). is there.

Table 1 shows the radius of curvature R (mm) of each lens surface of the infrared zoom lens according to the present embodiment, the center thickness of each lens, and the air space between the lenses (hereinafter, these are collectively referred to as the axial upper surface space). D) (mm), the refractive index N, and the material constituting each lens. In Table 1 and Tables 2 and 3 below, the numbers in the table represent the order from the object side, and the * mark attached to the left side of the surface number indicates that the surface is represented by the above-mentioned aspherical shape formula. Indicates that the surface is aspheric. Also, the middle row of Table 1 shows the values K, A ₄ , A ₆ , A ₈ , and A ₁₀ of the constants of the aspheric surface, and the lower row of Table 1 shows the variable values d1, d2, d3
At the telephoto end, the intermediate position, and the wide-angle end. The F-number of the infrared zoom lens according to this embodiment is as bright as 1.5, and the focal length of the entire system is 25 to 100 mm.

[0048]

[Table 1]

The infrared zoom lens is configured to satisfy the conditional expressions (1) and (2) as shown in Table 4 described later. In the infrared zoom lens according to the present embodiment, the focal position at the wide-angle end fluctuates by 0.05 mm in the object direction when the temperature rises by 10 ° C. 8 out of ₅
The two lenses of the lens L ₈ and the ninth lens L ₉ can compensate for variations in the focal position due to temperature by 0.19mm moves toward the object side.

<Embodiment 2> FIGS. 3 and 4 show the configuration of an infrared imaging system having an infrared zoom lens according to the present embodiment. It is provided with imaging means. FIG. 3 is a diagram showing a lens position at a telephoto end, and FIG. 4 is a diagram showing a positional relationship of each lens group of the infrared zoom lens at a telephoto end (A), an intermediate position (B), and a wide-angle end (C). is there. Incidentally, FIG. 3, 4 and Table 2 below, a configuration in which image rotation correcting prism 4 is disposed between the fourth lens group G ₄ of the infrared zoom lens according to this embodiment the fifth lens group G ₅ It is shown.

Table 2 shows the radius of curvature R (mm) of each lens surface of the infrared zoom lens according to the present embodiment, the distance D (mm) between the upper surfaces of the respective lenses, the refractive index N, and the materials constituting each lens. Show. The middle row of Table 2 shows the values K, A ₄ , A ₆ , A ₈ , and A ₁₀ of the respective constants of each aspheric surface. The lower row of Table 2 shows the variable values d 1, d 2 in the column of the shaft upper surface distance D. ,
The values of d3 at the telephoto end, the intermediate position, and the wide-angle end are shown. Note that the F value of the infrared zoom lens according to the present embodiment is
It is as bright as 1.6, and the focal length of the whole system is 25-100 mm.

[0052]

[Table 2]

The infrared zoom lens is configured to satisfy the above conditional expressions (1) and (2), as shown in Table 4 described later. In the infrared zoom lens according to this embodiment, the focal position at the wide-angle end fluctuates 0.07 mm toward the object due to the temperature rise of 10 ° C. _Fourth lens L ₆ and seventh lens L ₇ are moved toward the image side.
By moving by 0.09 mm, it is possible to compensate for the fluctuation of the focal position due to the temperature.

<Embodiment 3> FIGS. 5 and 6 show a configuration of an infrared imaging system having an infrared multifocal lens according to the present embodiment. This imaging system is an infrared bifocal lens according to Embodiment 3. , And imaging means. FIG. 5 is a diagram showing a lens position at a telephoto end, and FIG. 6 is a diagram showing a positional relationship of each lens group of the infrared bifocal lens at a telephoto end (A) and a wide-angle end (B). Incidentally, FIG. 5, in FIG. 6 and Table 3, the configuration image rotation correcting prism 4 is disposed between the fourth lens group G ₄ of the infrared bifocal lens system according to Example and the fifth lens group G ₅ It is shown as

Table 3 shows the radius of curvature R (mm) of each lens surface of the infrared bifocal lens according to the present embodiment, the distance D (mm) between the axial top surfaces of each lens, the refractive index N, and the materials constituting each lens. Is shown. Also, the middle row of Table 3 shows values K, A ₄ , A ₆ , A ₈ , and A ₁₀ of each constant of each aspherical surface, and the lower row of Table 3 shows the variable values d 1, d 2 in the column of the above-mentioned shaft upper surface distance D. ,
The values of d3 at the telephoto end and the wide-angle end are shown.

[0056]

[Table 3]

The infrared bifocal lens is configured to satisfy the conditional expressions (1) and (2) as shown in Table 4 described later. Further, in the infrared bifocal lens according to the present embodiment, the focal position at the wide-angle end fluctuates 0.04 mm toward the object when the temperature rises by 10 ° C. G first of ₅
It is possible to compensate for variations in the focal position due to temperature by 0.05mm moving the first lens L ₁₁ and two lenses of the 12 lens L ₁₂ to the image side.

The F value of the infrared bifocal lens according to this embodiment is as bright as 1.4, and the focal length of the entire system is 25 mm and 1 mm.
00 mm. Since this lens is not a zoom lens configuration but a bifocal switchable lens, it can be made brighter and shorter in overall length than the above-described zoom lens. Moreover, since it is possible to improve the positional accuracy and repeatability of the second lens group G ₂ and the third lens group G ₃ of the movable unit as compared to the zoom lens structure, to reduce the fluctuation of visual axis position by the zooming operation Thus, it is possible to obtain a zoomable lens suitable for finer observation.

Table 4 shows values corresponding to the conditional expressions (1) and (2) of the infrared zoom lens or the infrared multifocal lens according to Examples 1 to 3.

[0060]

[Table 4]

FIGS. 7 to 9 are aberration diagrams showing spherical aberration, astigmatism, distortion, and chromatic aberration of magnification of the infrared zoom lens or the infrared multifocal lens according to Examples 1 to 3, respectively. 9 shows various aberrations at the telephoto end (A), the intermediate position (B), and the wide-angle end (C), and FIG. 9 shows various aberrations at the telephoto end (A) and the wide-angle end (B). As is apparent from these figures, according to each of Examples 1 to 3, in the wavelength band of 3 to 5 μm, it has good imaging performance up to the periphery of the visual field, and has high imaging performance over the entire magnification region. An infrared zoom lens or an infrared multifocal lens having the following can be obtained.

Incidentally, the infrared zoom lens or the infrared multifocal lens of the present invention is not limited to the above-described embodiment, but various modifications can be made. For example, the curvature radius R and the lens interval of each lens can be changed. (Or lens thickness) D can be changed as appropriate. Further, the infrared multifocal lens is not limited to the bifocal lens described in the third embodiment, and may be a lens that can be switched and used for three or more focal points.

[0063]

As described above, according to the present invention,
High imaging performance over the entire field of view and each magnification area,
In addition, a compact infrared zoom lens or infrared multifocal lens and an infrared imaging system having a small F value can be obtained. Further, according to the present invention, by providing the infrared zoom lens or the infrared multifocal lens, it is possible to arrange a compact image rotation correction prism in this lens, and to have the same field of view as the conventional one. A compact panoramic observation optical system can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a lens configuration of an infrared zoom lens according to a first embodiment at a wide-angle end.

FIG. 2 is a diagram showing a positional relationship of each lens group of the infrared zoom lens according to Example 1 at a wide angle end (A), an intermediate position (B), and a telephoto end (C).

FIG. 3 is a diagram illustrating a lens configuration at a wide-angle end of an infrared zoom lens according to a second embodiment.

FIG. 4 is a diagram showing a positional relationship of each lens group of the infrared zoom lens according to Example 2 at a wide angle end (A), an intermediate position (B), and a telephoto end (C).

FIG. 5 is a diagram illustrating a lens configuration at a wide-angle end of an infrared bifocal lens according to a third embodiment.

FIG. 6 is a diagram showing a positional relationship of each lens group of the infrared bifocal lens according to Example 3 at the wide-angle end (A) and the telephoto end (B).

FIG. 7 is an aberration diagram showing various aberrations of the infrared zoom lens according to Example 1;

FIG. 8 is an aberration diagram showing various aberrations of the infrared zoom lens according to Example 2;

FIG. 9 is an aberration diagram showing various aberrations of the infrared bifocal lens according to Example 3;

FIG. 10 is a schematic diagram illustrating a configuration of a panoramic observation optical system including an infrared bifocal lens according to the third embodiment.

FIG. 11 is a schematic view showing a configuration of a conventional infrared panoramic observation optical system.

[Explanation of symbols]

L _{1 to} L ₁₂ Lenses R _{1 to} R ₃₀ Curvature radii D _{1 to} D ₂₉ Axis upper surface spacing G _{1 to} G ₅ Lens group X Optical axes 1, 11, 21 Detection surface (imaging element) 2, 12, 22 Mask 3, 13, 23 Dewar window 4, 14, 24 Image rotation correction prism 10, 20 Infrared imaging lens 15, 25 Window glass 16, 26 Rotating mirror 17, 27 Infrared camera

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03B 15/00 G03B 15/00 WF Term (Reference) 2H044 EC12 2H087 KA01 NA03 PA11 PA17 PB11 QA02 QA06 QA12 QA21 QA25 QA37 QA41 QA45 RA05 RA12 RA13 RA37 RA41 RA42 RA44 SA23 SA27 SA29 SA32 SA63 SA64 SA72 SA75 SB03 SB13 SB22 SB23 SB37 TA01 TA02 UA02

Claims (7)

[Claims] 1. A first lens group having a focusing function and a positive refractive power, a second lens group having a zooming function and a negative refractive power, and a focus changed by zooming in order from the object side. A third lens group having a function of compensating the position and having a positive refractive power;
A fourth lens group having at least one aspheric surface and forming an intermediate image, and a fifth lens group having at least one aspheric surface and relaying the intermediate image on a detector surface are provided. An infrared zoom lens or an infrared multifocal lens, characterized in that it has a configuration as described above. 2. The apparatus according to claim 1, wherein the following conditional expressions (1) and (2) are satisfied.
Infrared zoom lens or infrared multifocal lens as described. _{0.5 <f / f 1-4 <1.0} ...... (1) 2.5 <f 4 / f 5 <3.0 ...... (2) where, f: total focal at the telephoto end distance f _1-4: first at the telephoto end synthesis of a lens group to the fourth lens group focal length f _4: the focal point of the fourth lens group distance f _5: focal length of the fifth lens group 3. A luminous flux, wherein a mask for limiting an aperture is arranged between the fifth lens group and the detector surface, and which passes through the mask for an effective size of the detector surface. 2. All the lenses are configured to be transmitted through an optical system from the first lens group to the fifth lens group.
Or the infrared zoom lens or the infrared multifocal lens according to 2. 4. The field of view is changed by moving a position of a part or all of the fourth lens group or the fifth lens group by a predetermined amount along an optical axis according to a temperature change. The infrared zoom lens or the infrared multifocal lens according to any one of claims 1 to 3, wherein the infrared zoom lens or the infrared multifocal lens according to any one of claims 1 to 3, is configured to compensate for a change in a focal position caused by a temperature change. 5. The first lens group includes a meniscus lens having a positive refractive power made of silicon and a lens having a negative refractive power made of germanium.
The second lens group includes a lens having a positive refractive power using germanium as a material and a lens having a negative refractive power using silicon as a material, and is used in a wavelength band of 3 to 5 μm. The infrared zoom lens or the infrared multifocal lens according to claim 1. 6. An infrared zoom lens or an infrared multifocal lens according to any one of claims 1 to 5, and an imaging means for imaging an image by the infrared zoom lens or the infrared multifocal lens. And infrared imaging system. 7. An infrared zoom lens or an infrared multifocal lens according to claim 1, a turning mirror turned around an axis, and a mirror turn for turning the turning mirror. A moving mechanism, an image rotation correcting prism for correcting rotation of an image accompanying rotation of the rotating mirror, a prism rotating mechanism for rotating the image rotation correcting prism, and a rotation corrected by the image rotation correcting prism. A panoramic observation optical system, comprising: an image pickup means for picking up an image formed by the image rotation correction prism, wherein the image rotation correction prism is disposed between the fourth lens group and the fifth lens group.