JPS58100836A - Photographing device - Google Patents

Abstract

PURPOSE:To decrease unnecessary length of optical path and to reduce the size of a titled device by disposing a pair of optical elements for focusing of which the combined refracting power changes when the elements are relatively displaced within the plane perpendicular to the optical axis in the optical path of a photographing system. CONSTITUTION:When the eyegrounds Ef is illuminated by putting an observing light source 22 on, the primary fundus image Ef' is formed by an objective lens 1. The luminous flux from the image Ef' passes through a stop 2 and is made into parallel light by a positive lens 3. The parallel light is made incident to a variable refracting power lens 4, by which the magnification is changed; thereafter, the light is made incident to a stationary lens 5. Since a photographinc lens Z is set at a focal length, the image is formed as the secondary image Ef'' of a desired magnfication on a film 10. If the lens elements 4a and 4b are changed in mutually opposite directions by operating a moving mechanism with the sharpness of the fundus image as a measure, the combined magnification of the lens 4 changes; therefore, the image Ef' and the film 10 are made conjugate. Thus, the size of the device is reduced by moving the lens 4 in proximity to the stop 2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to focus adjustment of a photographic optical system, and is particularly suitable for a fundus camera.

With the spread of medical examinations for adult diseases, the KIN fundus camera has become widely used, and along with this, there have been significant improvements in fundus cameras. However, the 7-orcus structure often follows the conventional format, and for example, the eye moves to the final surface of the photographic lens. The method that changes the optical path length has the advantage of maintaining a telecentric arrangement, but it has the disadvantage of being mechanically large, whereas the method that moves the focusing lens has a much smaller structure. However, it is undeniable that moving the focusing lens in the optical axis direction increases the size of the optical system. Once this was no longer considered the case, it was no longer allowed for the aircraft to occupy a large space, and in practice, it became desirable to have something large enough to not get in the way even in a small medical room.

In addition, in the case of a retinal camera where magnification can be changed, the total length becomes longer due to the length of the photographing lens, but in particular, the photographing lens reaches from the aperture due to the range of movement of the focusing lens. And along with that, oblique light 1Ii
Since it passes through the lens at a position away from the l#i optical axis, it is thought that the lens diameter increases, which, together with the increase in the total length, increases the overall size.

An object of the present invention is to reduce the size of the device.

Therefore, the present invention provides a relative K in a plane perpendicular to the optical axis.
The composite refractive power changes by at least %1 when it is placed in the 11th position.
A pair of seven focusing optical elements are arranged in the optical path of the imaging system to reduce unnecessary optical path length.Hereinafter, an embodiment in which the present invention is applied to a fundus camera capable of zooming will be described.

[Figure 1] C is the silver to be examined, XtFi fundus. Further, 1 has the function of forming a fundus image with an objective lens. Reference numeral 2 is a photographic aperture, which has the function of determining the first number of the photographic system, and is arranged approximately conjugate with the pupil of the eye to be examined.

3 is a standard positive lens for diopter correction, emmetropia (zero dioptre)
Milli01! The light beam emitted from the bottom and imaged by the objective lens l is converted into parallel light. 3' C is another lens for diopter correction, which has stronger refractive power than a standard positive lens, and is replaceable and detachable. In addition, a positive lens with a weak refractive power and a lens f with a negative refractive power are detachably provided.

4 is a horizontally smooth IIO variable magnification lens, made in 1976.
The refractive power changes continuously by displacing both lens elements in opposite directions in a direction perpendicular to the optical axis. Defining the thickness t by the equation %(),
m is the article of incorporation that expresses the change in lens magnification due to the displacement of the element, and is a small value compared to the square of the lens radius 0*llK, 1 is the constant of the variable prism along the Fiz axis, c is the constant of the variable prism along the y axis, and D is the lens O The constant of the prism to be removed to minimize the metal thickness, 1 is the thickness at the optical axis, 1 (T)
tfXK As an irrelevant lens thickness, the constant m of the pixel element, m
, o, n, and y as reflective signs, the articles of incorporation excluding self and y are %O, which takes the value 00. FIG. 3 is a perspective view of these lens elements, showing the axial direction from the @4fgFix axial thickness. Of course, the 01 character on the element is added for explanation purposes, and there is no actual number written on it. It represents the average refractive power of each section, the first value is the average power of each section @1) as a spherical lens, and the second value is the average power of a cylindrical lens with an axis in the 45° direction. However, the illustrated divisions are virtual, and in reality, the four refractive powers change continuously at the boundary positions. In Figure 4 (a)
When the Fi pixel elements are superimposed so that their refractive powers are all canceled, the refractive power at this time is #'10 diopter. In addition, (b) and (a) are overlapped by moving ±1 section in the tix direction, and in the case of (b), the overlapping part is connected to -1,0 diopter and 41+, and further 2
The two racks 41 & 4H engage with the tit pinion 42 axially symmetrically to operate the differential. That is, when the binion 42 is rotated simultaneously, the racks 41& and 411+a move in opposite directions, thereby shifting the positions of the lens elements 4a and 41 relative to each other. However, it is preferable to move both lens elements, but one of the lens elements may be moved manually by a knob (not shown), or m for driving the pinion 42. Operated by an autofocus device.

Reference numeral 2 denotes a photographing lens, which is composed of a fixed lens 5 that converges parallel light, a compensator 6 that compensates for image plane movement during zooming, a varinee tough that changes the focal length, and a relay lens 8. Compensator 6 and variator 7#'i
They are simultaneously transported by a zooming mechanism (not shown). Note that instead of a zoomable photographic lens, a combination of a fixed imaging lens and a zoom attachment lens, or only a fixed imaging lens may be provided.

9#i quick return mirror, lO is film, 1
1 field lens placed at position ζ equivalent to film lo, 12 #i prism for changing the optical path, 13 eyepiece lens, 1 member 9, 11, 12, 13 tj finder 411, members 1 to 8. The film 10 defines a photographic system. Figure 2 Fi film 10 top Kll! Draw how the bottom image is formed.

Next, 14 companies have a perforated mirror with an aperture at the optical axis position and are installed obliquely to the optical axis, 15 and 16t; i relay lens, 17
#i optical path bending) mirror, 1B#i light plate with ring slit, 19 and 21 are condenser lenses, 20#'
It is a strobe light source for i-photographing, and an eight-pagen lamp for 22tj observation. In this case, parts 1 to 22 and the objective lens constitute a fundus illumination system, and each light source 20
and 22Fi, the key light plate 18 regarding the intervening optical system, respectively.
is conjugate with respect to the tracing light source 18 and the perforated mirror 14#'i relay lenses 15 and 16, and is set so that the pupil of the eye to be examined and the perforated mirror 14 are conjugate.
When the light source 20 or 22 is turned into a point, a ring slit-shaped secondary light source is formed above the pupil, and the fundus of the eye is illuminated.

Furthermore, the tip of the 30iit mirror is equipped with a small mirror tilted with respect to the optical axis, while the mirror size is 30#i when observing.
It is located in the Fi optical path and moves out of the optical path just before photographing. 3
A 1Fi projection lens and a 32#i-shaped index plate are used to form an index image on the mirror surface of the projection lens 31Fit law 30. This is a 33#i split prism, in which triangular prisms are arranged vertically on the paper so that their inclinations are reversed. Further, 34 is a condenser lens, and 35 is an illumination light source, which is useful for wATIAing the index plate 32. Here, members 3° to 35#i are integrated and connected to the driver @43, and the position adjustment in the optical axis direction is performed.
When O and the fundus are adjusted to be conjugate, the condition that the index plate 32 and the fundus are conjugate is satisfied. As a result, the index image projected on the fundus becomes one line in the focused state, and two lines shifted from the center when the 7 orcus is out of focus. Orcus λ allows you to easily achieve an accurate 7 orcus.

In the above 1# formation, when the observation light source 22 is turned on and the fundus correction is illuminated, the primary fundus image If' is formed by the objective lens l.
is formed. At that time, the subject has emmetropia and ψF1 weak -
In amblyopia myopia, the image xt' is formed at or near the focal plane of the objective lens l, and the light beam from the image xt' passes through the aperture 2 and becomes parallel light or nearly parallel light at the positive lens 3.
After entering the variable refractive power lens 4 and changing the magnification, the light enters the fixed lens 5, and since the photographing lens 2 is set at the desired focal length, it is recorded on the film 10 as a secondary image xf of the desired magnification. It is formed. At that time, if the secondary image is not conjugate with the film 10, the secondary image will be unclear, so the operator looking through the eyepiece 13 will determine the sharpness of the fundus image and the position of the index line image. The drive mechanism 43 is adjusted based on the degree of deviation.
When the lens elements No. 1 and 4b are operated in mutually opposite directions, the combined magnification of the variable magnification lens No. changes. Rattan Kiru. By placing the variable magnification lens 4 close to the diaphragm 2, the size can be reduced, and the parallel or near parallel beam is incident, so the variable magnification lens number has an effect on image quality. Impact decreases.

Furthermore, if the subject has strong myopia, the #i primary fundus image correction '-1 moves closer to the lens than the focal plane of the objective lens 51, and an image is formed on the #f filter ^10 between the magnifications of the variable magnification lens number am. It becomes dangerous. Of course, it is possible to increase the range of change by changing the dimensions of the lens element, but since the amount of movement of the lens element also increases, this results in an increase in extra space. Since using a lens element with a large size will deteriorate the image quality, it is considered that a corrective lens is a more desirable choice. Proper focusing can be achieved by replacing it with lens 3', which has a stronger refractive power; conversely, if the subject is farsighted, objective lens 1
Although the image mr'-2 is formed at a position away from the focal plane of , it is possible to achieve 7 focusing by attaching a negative correction lens f. Although the above explanation is an example in which the present invention is applied to a fundus camera, the present invention can also be used in general in a so-called front aperture type optical system in which the aperture is located on the object side of the imaging lens. An optical system with a large number is convenient because it causes less aberration due to the aperture ratio.As stated above, the present invention allows focusing without changing the length in the optical axis direction, so the overall length In particular, in the case of an arrangement where the total length of the optical system is longer than the focusing section on the image side, it is possible to reduce the lens diameter along with the short axis of the total length, making it possible to reduce the compactness. Significant cost reductions can be achieved over time.

[Brief explanation of the drawing]

Fig. 1 is an optical cross-sectional view showing the embodiment, Fig. 2 is a drawing showing a fundus image formed on the TIY ilm, and Fig. 3 (1) (b).
Perspective view of F1 side-shifting variable magnification lens, Figure 4 (&)
佽)(o) An explanatory diagram of the action of the Fi lateral shift type variable magnification lens. In the figure, 1 is an objective lens, 2 is a tj photographic aperture, an SFi diopter correction lens, 4 is a side-shifting type variable magnification lens, 2 is a photographic lens, 1 is an otj film, an 18IIi ring slit tracing plate, 20 and 22#i light sources, 41 & This is a drive mechanism for the 411 tj rack, 4211 binion, and 43/fi focus. Applicant Canon Co., Ltd. Agent Marushima Man −“', T, +. L-2,5

Claims (5)

[Claims] (1) At least a pair of optical elements whose composite magnification changes when relatively displaced in a plane perpendicular to the optical axis are placed in the optical path of the photographing system, and the focus #14% means is used to An imaging device characterized by displacing an element. (2) The photographing device according to claim (1), wherein the optical element is arranged close to a photographing aperture of the photographing system. (3) Claim IIK comprising a diopter correction lens group that can be attached to and detached from the optical element and the lever of the photographic diaphragm 9.
The imaging device described in (2). (4) The diopter correction lens group is for emmetropic eyes C4III
The photographing device according to claim (3), further comprising a positive lens that converts the light ray coming from M into parallel light. (5) The photographing system has an objective lens that forms a real image on the object 11 from the photographing aperture, and further includes a fixed lens and a variable magnification lens in sequence on the image side of the optical element. The imaging device described in 2).