JPS58159509A - Lens holding device - Google Patents

Abstract

PURPOSE:To improve the temperature resistance of a lens by fixing the lens with a retainer ring through a lens sleeve. CONSTITUTION:The lens sleeve 30 is incorporated in the fitting part 21 of a mirror frame 20 and they are fixed with the retainer ring 24 engaging the screw part 23 of the mirror frame 20 threadably. Consequently, one side surface 41b and outer circumferential surface 41c of the outer circumferential edge 41 of a plastic lens 40 incorporated by engaging the other side surface 41a of the outer circumferential edge 41 with a flanged part 22 are held elastically by a thrust beam 33 and a radial beam 34 respectively. Therefore, the shape variation of the plastic lens 40 with temperature is absorbed by the beams 33 and 34 which deform in the thrust and radial directions of the lens sleeve 30, so the temperature resistance of the lens 40 is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a lens holding device that absorbs temperature changes within the lens frame of a lens such as a plastic lens in a structure that holds the lens, and prevents the original performance of the lens from being affected by temperature changes within the lens frame. We have improved the humidity resistance of lenses with poor temperature resistance such as plastic lenses, and expanded the operating temperature range. The purpose is to make the provision possible.

Conventionally, when a lens, for example, a plastic lens 1, is to be mounted in a lens frame 2, as shown in FIG. The plastic lens 1 is fitted into the lens frame fitting part 4 while being in contact with each other, and the threaded part I threaded on the outer periphery of the presser ring 6 is screwed into the lens frame threaded part 5 threaded on the inner periphery of the lens frame 2. While doing so, screw the presser ring 6 into the inside of the lens frame 2, and then tighten the presser ring T.
The contact edge 8 with the plastic lens 1 formed on the inner periphery of R6 is pressed against the outer periphery 1b on the front side of the plastic lens 1, and the plastic lens 1 is fixed within the lens frame 2.

Now, what happens when the plastic lens 1 having the above structure is assembled to the lens frame 2 at room temperature and then exposed to a high temperature atmosphere.

Since the coefficient of linear expansion of the molding material of the plastic lens 1 is larger than that of the molding materials of the lens frame 2 and the presser ring 6, the clearance of the lens frame fitting portion 4 in the lens frame 2 becomes small.

Furthermore, this effect is most noticeable at point A where the lens and presser ring contact each other in Figure 1a (see the enlarged view shown in Figure 1A); The clearance is already zero, and in the high-temperature atmosphere, the difference in linear expansion coefficient of the molding materials of the lens 1 and the presser ring 6 directly affects the surface shape.

That is, at the contact point A of the lens 1 and the presser ring 6, the outer peripheral edge 1b on the front side of the lens 1, which the contact edge 8 of the presser ring 6 presses against, is depressed, and the abutment edge 8 of the presser ring 6 causes
The lens 1 is regulated to have zero clearance.

Therefore, as the temperature increases, the plastic lens 1 begins to expand in the radial direction, but the deformation of the plastic lens 1 in the radial direction is restricted by the restriction by the presser ring 6. thermal stress occurs.

Then, the thermal stress generated inside the plastic lens 1 concentrates on unregulated deformation in the optical axis direction, causing the plastic lens 1 to deform in the optical axis direction.

Considering the cross section of the plastic lens 1 in the axial direction including the optical axis, the length of the chord B in FIG.

Expansion concentrates at the corner AB, and as a result, the radius of curvature becomes smaller.

Now, suppose that the length of the arc at room temperature is AB, the length of the arc at t° C. higher than room temperature is B', and the coefficient of linear expansion of the plastic lens 1 is α.

□, to A’B6AB@(1+αt) Approximate to

Conversely, when the plastic lens 1 and lens frame 2 assembled together at room temperature are exposed to a low-temperature atmosphere, the linear expansion coefficients of the molding materials of the plastic lens 1, lens frame 2, and presser ring 6 differ as described above. Therefore, as the temperature decreases, the plastic lens 1 contracts more than the lens frame 2 and the presser ring 6, and tends to shrink more than the lens frame 2 and the presser ring 6. Outer edge ib on the front side of the plastic lens 1 fixed by pressure contact of the contact edge 8 of the ring 6
As a result, as in the case of high temperatures, the plastic lens 1 cannot contract more than the contraction of the presser ring 6, and thermal stress is generated inside the plastic lens 1. is concentrated in the optical axis direction of the plastic lens 1, which is not restricted by the presser ring 6, and deforms the plastic lens 1 in the optical axis direction.

Considering the axial cross-section including the optical axis of the plastic lens 1 shown in FIG. the result.

The radius of curvature becomes larger.

Now, if the length of the arc at room temperature is AB, the length of the arc at t°C lower than room temperature is A'B', and the coefficient of linear expansion of the molding material of the plastic lens 1 is α, then A'B'2AB. (1-αt
) is approximated.

For the above reasons, when the plastic lens 1 is mounted in the lens frame 2 having a conventional structure using the presser ring 6, the radius of curvature of the plastic lens 1 changes by two changes due to temperature changes. That is, it is clear that it is small at high temperatures and becomes large at low temperatures, and it is also clear that the focus position shifts significantly and various aberrations worsen compared to at room temperature.

Further, in the conventional lens and lens frame configuration, as shown in FIG. 1e, the lens fitting portion 1 of the lens holding member 10
By fitting at least two lenses 12.13 into the lens 1 and interposing an alignment member 14 between both lenses 12.13, the distance between the two lenses 12.13 that are adjacent to each other by the outer periphery of the lens 12.13 is adjusted. A composite lens constructed in such a manner as to reduce the frictional resistance in the lens 12 and 13 and to prevent lens misalignment between the two lenses 12 and 13 has been proposed as proposed in Japanese Utility Model Application Publication No. 55-138606.

However, in the case of this configuration, the friction between the two lenses 12 and 13 is only reduced.

Structure 5 in which the lens 12.13 is fixed in the fitting part 11 by the presser ring 15 is equivalent to the conventional structure, and the lens 12.13 has an outer diameter l') that is fixed to the fitting part of the lens holding member 10. 11 or the inner diameter of the presser ring 15, and like the plastic lens 1, one lens 12.13
It is impossible to prevent changes in the radius of curvature due to temperature changes, and it is impossible to avoid shifts in the focus position and worsening of aberrations due to temperature changes.

Therefore, in the conventional lens mounting structure for the lens frame, a lens holding structure that prevents changes in the radius of curvature caused by temperature changes and that does not cause focus position deviation or deterioration of each phase aberration, or other appropriate lens holding structures is required. The development of countermeasures was desperately needed.

Therefore, when the lens is held within the lens frame by a holding ring, the present invention provides a lens sleeve that is provided with a beam that can be deformed in the thrust direction and the radial direction and is held between the lens frame and the lens. , by improving the conventional lens holding device, the beam of the lens sleeve absorbs changes in the radius of curvature of the lens housed in the fitting part of the lens frame due to changes in humidity, and the focal position due to changes in temperature of the lens is absorbed by the beam of the lens sleeve. This prevents movement of the lens and aggravation of aberrations, and also expands the temperature range in which the lens can be used.

An embodiment of the lens holding device of the present invention will be specifically described below with reference to Figures i+1+i.

FIG. 2a is a side sectional view showing the first embodiment of the present invention, and the same figure is a partially enlarged sectional view of the lens sleeve.

Reference numeral 20 denotes a lens frame, and 21 a fitting portion for a lens sleeve 30 provided inside the lens frame 20. A barrel portion 22 of a lens 40 is protruded from this fitting portion 21.

23 is a threaded portion screwed onto the inner peripheral surface of the lens frame 20, and 24 is screwed onto the threaded portion 23 of the lens frame 20.

This is an annular holding ring that holds the lens sleeve 30 fitted into the fitting part 21 of the lens frame 20, and a threaded part 25 corresponding to the threaded part 23 of the lens frame 20 is screwed onto the outer periphery of this holding ring 24. At the same time, a pressing edge 26 of the lens sleeve 30 is provided on the inner peripheral portion so that the lens sleeve 30 is integrally formed.

Therefore, when holding the plastic lens 40 in the lens frame 20, the inside of the fitting part 21 and the plastic lens 4
An annular lens sleeve 30 is interposed between the outer circumferential sides of the plastic lens 40 and the plastic lens 40 is inserted inside the lens frame 20 while one side 40 & of the outer circumferential edge 41 of the plastic lens 40 is engaged with the twisting frame 20 brushing attachment part 22. After loading the holding ring 24 into the lens frame 2,
The pressing edge 26 of this holding ring 24 is screwed into the threaded portion 23 of
The plastic lens 40 is held inside the lens frame 20 via the lens sleeve 30 by screwing the press ring 24 into the lens frame 20 while abutting the press ring abutting portion 32 of the lens sleeve 30. be able to.

That is, the lens sleeve 30 has a sleeve main body 31 having an outer diameter approximately equal to or slightly larger than the inner diameter of the fitting portion 21 of the lens frame 20, and a presser ring abutting portion 32 protruding from the sleeve body 31. A thrust beam 33 is provided protruding from the portion 32 side.

In addition, by providing a radial beam 34 protruding from the opposite end, it is integrally formed of a material having an elastic modulus smaller than that of the lens material to be held in the m-frame 20.

Furthermore, due to their elasticity, the thrust beam 33 and the radial beam 34 are intended to absorb deformation in the thrust and radial directions of the plastic lens 40 held within the e20, as will be described later. By providing the thrust groove 35 and the radial groove 36 at the protruding end of the sleeve body 31,
(However, one groove 35
．． 36 (which is of course also possible) and the sleeve body 31 for the radial beam 34.
In order to protrude more, as shown in FIG. 2, instead of the embodiment in which the protruding piece 37 of the sleeve body 31 is protruded orthogonally to the vertical direction, the protruding angle is set at an angle larger than 90°. By slanting and protruding, it is possible to impart greater elasticity.

By inserting the lens sleeve 30 having such a configuration into the fitting part 21 of the lens frame 20 and fixing it with the presser ring 24 screwed onto the threaded part 23 of the lens frame 20, the barrel attachment part 2
2, one side 41 of the periphery 41. The other side surface 41b of the outer peripheral edge 41
Thrust = 33. Its outer peripheral surface 41o is connected to the radial beam 34
They can be held elastically.

The molding material for the lens sleeve 30 is AB
The actual measurement data when integrally formed with SIM resin will be described in detail later, but other molding materials include FA.
(nylon), etc.; as another example, it is possible to carry out the implementation while applying a material that can satisfy the above conditions in relation to the lens (including glass lens) to be held in the lens frame. can.

Also, the thrust beam 33. The radial beams 34 are formed by protruding a plurality of thrust beams 33 and radial beams 34 intermittently along the annular direction of the sleeve body 31, or by alternately protruding the drawing frames 33 and 34. Further, the presser ring abutting portion 32 with the presser ring 24 is not necessarily necessary, and does not need to be provided protrudingly (a case in which this is implemented is specifically shown in FIG. 3).

The embodiment shown in Fig. 3 is an embodiment in which the lens sleeve 30 is constructed without the presser ring abutment [32 protrudingly provided.The other configuration is the same as the embodiment shown in Fig. 2a, so the same number is used. with
The explanation will be omitted.

Now, as mentioned above, if the plastic lens 40 is held in the lens frame 20 with the lens sleeve 30 interposed and left in a high temperature state, the plastic lens 40 will begin to stretch. .

We have specifically explained that in the case of the conventional configuration shown in Figure 1, the outer diameter of the plastic lens becomes larger than the inner diameter of the lens frame, resulting in a large change in the shape r. According to the configuration shown in FIGS. 2a and 3FA, the lens sleeve 30 made of a material having an elastic modulus smaller than that of the lens material is interposed around the outer periphery of the plastic lens 40. The radial expansion of the lens 40 is caused by the radial beam 34. Each of the thrust beams 33 expands in the thrust direction.

The plastic lens 40 is absorbed while being deformed inwardly and outwardly, and the thermal stress generated inside the plastic lens 40 is extremely small or almost non-existent, thereby preventing the plastic lens 40 from changing its shape. This effect will be more specifically demonstrated using actual measurement data, which will be described later.

Further, the thrust beam 33. Regarding the effect of absorbing deformation of the radial beam 34, the illustrated thrust groove 35. As mentioned above, the radial groove 36 can provide more accurate operation and effect.

Furthermore, contrary to the above, if you leave it in a low temperature state,
Plastic lens 40 begins to shrink.

However, the thrust beam 33 that contacts the side surface 41b of the plastic lens 40 has an elastic modulus smaller than the elastic modulus of the material of the lens.

In addition, due to the elastic effect of the beam itself, there is no possibility of the presser ring contact point A shown in FIG. 1. The plastic lens 40 can freely contract in the radial direction. Also, the coefficient of linear expansion of the lens is compared to that at high temperatures.

Because it is small at low temperatures, the outer diameter of the lens 40 and the thrust beam 33 of the lens sleeve 30. There is also no play in the inner diameter of the radial beam 34 to the extent that it degrades lens performance.

Furthermore, the radial beam 34 of the lens sleeve 30
In the case of the configuration shown in the figure, when the lens sleeve 30 is fitted onto the plastic lens 40 at room temperature, the radial beam 34 resists the elasticity of the outer peripheral surface 41 of the plastic lens 40. This more effectively prevents the occurrence of play when the plastic lens 40 contracts at low temperatures.

In the thrust direction, depending on the amount of tightening of the presser ring 24, the thrust beam 33 can exert the required elastic action, and the plastic lens, which is positioned in the thrust direction by the body attachment part 22 in the lens frame 20, can be tightened depending on the amount. It can always be held in a proper position.

Next, a second embodiment will be explained with reference to FIGS. 4a and 4b.

In such an embodiment, the thrust beam 62 of the lens sleeve 60 is attached to the outer periphery of the plastic lens 50 held within the lens frame 20. It is constructed by attaching a holder [51 with contact edges s1a and sib with the radial beam 63 and providing a contact surface 510 with the barrel portion 27 of the lens frame 20 on the back side of the outer periphery of the plastic lens 50. On the other hand, the lens sleeve 60 has an annular sleeve body 61 as shown in FIG.
By providing a protruding portion 64 that abuts against the pressing edge 26 of the presser ring 24 and protruding thrust beams 62 and radial beams 63 intermittently and alternately along the circumferential direction of the sleeve body 61, the above-mentioned It is integrally formed from a material based on the same conditions as the lens sleeve 30 of the first embodiment.

After fitting the lens sleeve 60 into the holding part 51 of the plastic lens 50, the contact surface 510 of the plastic lens 50 is brought into contact with the barrel part 27 of the lens frame 20, and the lens sleeve 60 is attached to the lens frame 20. Insert the plastic lens 50 into the lens frame 20 while fitting it into the fitting part 21 of the lens frame 20, and then insert the plastic lens 50 into the screw part 21 of the lens frame 20. By screwing the presser ring 24 onto the lens sleeve 3 and tightening the presser ring 24 while making contact with the abutting portion 64 of the lens sleeve 60, the plastic lens 50 can be held in the lens frame 2 while the lens sleeve 60 is interposed.
0 can be held inside.

This embodiment also provides the same effects as the first embodiment, and the holding part 51 of the plastic lens 50
Lens sleeves 60 are attached to the abutting edges sia and s1b, respectively.
Thrust beam 62. By bringing the radial beam 63 into contact and tightening the lens sleeve 60 with the presser ring 24, the thrust beam 62 is deformed to the left and is constantly subjected to stress, which causes the presser 1 caused by temperature changes.
It is also possible to prevent a decrease in loosening torque caused by stress relaxation between the abutting portion 64 of the lens sleeve 60 and the lens sleeve 60, although not shown.
By providing thrust grooves and radial grooves at the protruding ends of the first side beams 63 as in the first embodiment, it is possible to further enhance the absorption effect of the first side beams 62 and 63 against deformation of the plastic lens 50.

Further, FIG. 5 shows a third embodiment, and FIG. 5A is a partially omitted sectional view, and FIG. 5A is a front view.

In such an embodiment, a tapered portion 71 is provided on the outer periphery of the plastic lens 70, while a lens sleeve 80
In this case, an annular sleeve main body 81 is sloped to correspond to the slope of the thrust beam 82 and the tapered portion 71 of the plastic lens 70, and a radial beam 83 is formed with a thrust groove 84. Protruding through the radial groove 85,
It is integrally formed from the same material as the embodiments described above.

Also, the thrust beam 82. FIG. 5 shows an embodiment in which the radial beams 83 are provided protrudingly along the circumferential direction of the sleeve body 81 intermittently and in different positions, but the present invention is not limited thereto. do not have.

Now, also in the case of this embodiment, the plastic lens 7
The outer periphery back of the lens 0 is brought into contact with the barrel attachment 22 of the lens frame 20, and the plastic lens 7 is inserted while the lens sleeve 80 is interposed on the outer periphery.
0 is placed inside the lens frame 20, and the presser ring 24 is screwed onto the threaded portion 23 of the lens frame 20, and the pressing edge 26 presses the lens sleeve 80, and the thrust beam 82 is attached to the front surface of the outer periphery of the plastic lens 70. The plastic lens 70 is held within the lens frame 20 by bringing the radial beams 83 into contact with the tapered portions 71a of the tapered portions 71, respectively.

Therefore, the deformation of the plastic lens 70 in the lens frame 20 due to temperature changes is caused by the thrust beam 82. It can be absorbed by both the radial beams 83.

FIG. 6 shows a fourth embodiment of the present invention, in which tapered portions 91 are provided on both sides of the outer periphery of a plastic lens 90 to be held in the lens frame 20, and the tapered portions 91 are provided with the picture frames 102 and 103 of the lens sleeve 100, and the other , the lens sleeve 100 is attached to a diagonal beam 102 . A diagonal beam 103 on the side of the barrel is provided intermittently and is integrally formed of the same molded material as the lens sleeve of the first to third embodiments.

Thus, the plastic lens 90 can be held in the lens frame 20 in which the lens sleeve 100 is inserted into the fitting part 21 of the lens frame 20 by abutting against the barrel attachment part 22 in the lens frame 20.

Incidentally, instead of the lens sleeve 100 having the annular sleeve body 101 and the drawing holders 102 and 103 protruding therefrom, one drawing holder 102 and 103 are provided on both sides of the sleeve main body 111 and grooves 104 and 1 are provided.
It is also possible to implement the present invention by inserting a single lens sleeve 110 projecting through the plastic lens 90 at intervals in the circumferential direction of the plastic lens 90.

Now, the deformation of the plastic lens 90 held in this manner in the thrust direction and the radial direction due to temperature changes can be absorbed by the action of expanding the image racks 102 and 103 on the top side of the presser foot and on the side of the barrel section outward. In the opposite case, it can be absorbed by the return elasticity of the drawing racks 102 and 103.

As is clear from the above description, the lens holding device of the present invention holds the lens while interposing the lens sleeve in the lens frame fitting portion, so it is difficult to prevent the lens from changing due to temperature changes in the lens, especially the plastic lens. Changes in shape can be prevented by being absorbed by beams that have elastic deformation action in the thrust and radial directions provided in the lens sleeve, and the temperature resistance of the lens can be improved.

In addition, for the lens sleeve inserted between the lens frame and the lens, at room temperature, the tightening of the presser ring depends on the amount.
By causing elastic deformation in the thrust beam, etc., it is possible to prevent the reduction in loosening torque of the presser ring due to stress relaxation, which has conventionally occurred due to temperature changes, and as a result, the lens can be held more firmly.

Furthermore, by allowing the radial beam of the interposed lens sleeve to undergo elastic deformation at room temperature, it is possible to prevent the lens from wobbling or eccentricity due to temperature changes, improving the temperature resistance performance of the lens system. I can do it.

In the above embodiments, the case where the lens is applied to a plastic lens has been explained, but it can also be applied to a glass lens with a thin center wall, a lens that is easily distorted or deformed when fixed with a conventional holding ring, or other parts. It is also possible to maintain the same effect.

In addition, Table I and Table ■ below show actual measurement data comparing the amount of change in the radius of curvature due to temperature change of the lens between the lens holding device according to the second embodiment of the present invention and the conventional lens holding device. .

Table 1 shows the change in lens shape r due to the conventional lens holding device (FIG. 1L), and Table 1 shows the case of the embodiment of the present invention.

Table I [7 Table ■

[Brief explanation of drawings]

Figure 1a is a side sectional view showing a conventional lens holding device;
The figure is a partial enlarged cross-sectional view of Figure 1 &, Figure 1 a and d are 1
Explanatory diagram showing the change in the shape of the lens in Figure a, Figure 1e
1A is a side sectional view showing a conventional example different from that shown in FIG. 1A, FIG. 2A is a side sectional view showing the first embodiment of the present invention, FIG. This figure is a cross-sectional view showing an embodiment in which the abutting portion of the lens sleeve in FIG. 2a is not provided in a protruding manner. FIG. 4a is a sectional view showing a second embodiment of the present invention, FIG. 4 is a perspective view of a lens sleeve used in the same embodiment,
Fig. 5a is a sectional view showing a third embodiment of the present invention, Fig. 5 is a front view of the same with some parts omitted, and Fig. 6a is a sectional view showing a fourth embodiment of the invention. FIG. 6 is a perspective view showing an example of a single length and a rib for the annular lens sleeve used in the same example. 1.12, 13, 40.50, 70°90... Plastic lens 2.20... Lens frame 3.22, 27... Lens leg attachment part 4. Lens fitting part 5.23. ...Threaded portions of the lens frame 6.15, 24...Pressure ring 7.25 years old Threaded portion 21 of the presser ring...Fitting portion of the lens sleeve in the lens frame 26...Pressed edge of the presser ring 30.60, 80, 100, 110... Φ Lens sleeve 31.61, 81, 101 *... Sleeve body 32.64 Fist Φ/Press ring abutment part 33.62.82 φ... Thrust beam 34.63, 83φ... Radial beam '35. 84... Slash F groove 36, 85 @O radial groove 37... Projecting piece 41. @φ Plastic lens outer periphery 51... φ Plastic lens holding part 71. 91・Φ・Taper part of plastic lens 102...Oblique beam on presser source side 103...Oblique beam on leg attachment side 104.105・@φ diagonal beam groove Patent applicant Olympus Optical Industry Co., Ltd. Figure 1 (b) ＼ 8 Figure 1 (C) Δ Snake (d) Figure 1 (e) Figure 2 Figure 1!3 Figure 4 Figure 5 (b)

Claims (9)

[Claims] (1) A lens holding device for fixing a lens inserted into a lens frame with a holding ring, comprising a beam deformable in the thrust direction and the radial direction between the inside of the lens frame and the outer periphery of the lens. A lens holding device characterized in that a lens sleeve is interposed and the lens sleeve is fixed by the holding ring, and the lens is held via the lens sleeve. (2) In a lens holding device that fixes a lens inserted into a lens frame with a holding ring, an annular sleeve body is inserted between the inside of the lens frame and the outer periphery of the lens in the thrust direction and through a thrust groove and a radial groove. A lens sleeve comprising a beam deformable in the radial direction is interposed, and the lens sleeve is fixed by the holding ring.
1. A lens holding device characterized in that a lens according to the invention is held via a lens sleeve. (3) In a lens holding device that fixes a lens inserted into a lens frame with a holding ring, along the outer periphery of the lens,
A lens sleeve comprising a parallel or tapered surface for contact with a thrust beam and/or a radial beam of the lens sleeve, and a beam deformable in the thrust direction and the radial direction between the inside of the lens frame and the outer periphery of the lens. The lens sleeve is interposed so that its beam is brought into contact with a contacting parallel surface or tapered surface of a thrust beam and a radial beam provided on the outer periphery of the lens, and the lens sleeve is interposed between the inside of the lens frame and the outer periphery of the lens. is fixed by the presser ring, and the lens is held via a lens sleeve. (4) The lens sleeve has an annular sleeve main body whose outer diameter corresponds to the inner diameter of the lens barrel, and a beam that can be deformed in the thrust direction and the radial direction protruding along the annular direction of the sleeve main body. A lens holding device according to claim 1, 2, or 3, characterized in that the lens holding device is constructed as follows. (5) The lens sleeve includes an annular sleeve body whose outer diameter corresponds to the inner diameter of the lens barrel, and thrust beams and radial beams intermittently and/or alternately provided along the annular direction of the sleeve body. A lens holding device according to claim 1, 2, or 3, characterized in that it is constructed by: (6) The lens sleeve according to claim 1, 2, 3, 4, or 5, wherein the lens sleeve includes a portion that abuts against the presser ring. Lens holding device. (7) The lens sleeve has a holding ring side beam and a body side frame protruding from the lens frame fitting portion and both left and right ends of the lens frame fitting portion, and a beam groove is provided at the projecting end of the picture frame. A lens holding device according to claim 1, characterized in that the lens holding device is constructed by: (8) A patent claim characterized in that the lens frame is configured by providing a lens mounting portion and a lens sleeve fitting portion on the inside of the lens frame, and providing a threaded portion for screwing the presser ring. The lens holding device according to the range 1, 2 or 3. (9) The lens holding device according to claim 1, 2 or 3, wherein the front lens is made of a plastic lens.