Patent Application
20080100932
The present invention relates to lens units with multiple lenses press-fitted and anchored in position in a lens barrel.
Lens units featured in addition to a primary phoning function in recent camera-mounted mobile phones or the like have a structure in which lenses 2a, 2b, and 2c are integrated with lens barrel 1 to be attached to the main body of the device as shown in
In
In a conventional lens unit as described above, the number of steps is determined in accordance with the number of lenses configuring the lens unit. The diameter of through-hole 3 between adjacent steps 4 is uniform.
A related prior art is, for example, disclosed in Japanese Patent Unexamined Publication No. 2004-147032.
In
A lens unit of the present invention includes a lens barrel with a through-hole, a first lens press-fitted into the through-hole, a first step catching an outer edge of the first lens in the through-hole, a second lens press-fitted into the through-hole in a direction of an optical axis of the first lens, and a second step catching an outer edge of the second lens in the through-hole. The second lens has a diameter larger than that of the first lens. A third step or a sloped area broadening the through-hole from the first lens to the second lens is further provided between the first step and the second step.
This structure suppresses the concentration of an enlargement stress, generated by the lens press-fitted afterward, on the step catching the lens press-fitted first. Damage to the lens unit is thus preventable. Accordingly, the productivity of the lens unit can be improved.
Exemplary embodiments of the present invention are described below with reference to drawings.
The structure of the lens unit in the first exemplary embodiment of the present invention is detailed next. In
The outer edge of first lens 8a is anchored inside through-hole 6 by contacting first step 9a. The outer edge of second lens 8b is anchored inside through-hole 6 by contacting second step 9b. The outer edge of third lens 8c is anchored inside through-hole 6 by contacting fourth step 9c. In this way, an insertion distance of each of lenses 8a, 8b, and 8c is set in through-hole 6.
In this lens unit, the lenses are press-fitted into through-hole 6 in the order of smaller diameter with respect to lens barrel 7, i.e., lens 8a, lens 8b, and then lens 8c. The distance between adjacent lenses is set by making the outer edge of each lens 8a, 8b, and 8c caught at steps 9a, 9b, and 9c corresponding to the diameters of lenses 8a, 8b, and 8c, respectively.
Step 10a is further formed between step 9a and step 9b in this lens unit. Step 10b is further formed between step 9b and step 9c. Provision of these steps 10a and 10b suppresses the concentration of enlargement stress 11, generated by the lens press-fitted afterward (e.g., lens 8b), on step 9a catching lens 8a which is press-fitted first. Damage to lens barrel 7 due to this enlargement stress 11 is thus suppressed, allowing the productivity of the lens unit to be improved.
Damage can be suppressed because provision of third step 10a between lenses 8a and 8b, for example, changes a thickness of lens barrel 7 in front and back of step 10a, and thus the strength of lens barrel 7 also changes. In other words, if lens 8b is press-fitted under conditions where lens 8a is already press-fitted, a press-fitting stress of this lens 8b applies a force that acts to enlarge lens barrel 7, using a base of step 9a holding lens 8a press-fitted first as a fulcrum. Provision of step 10a between this preceding lens 8a and subsequent lens 8b can intentionally change the strength of lens barrel 7 at this stepped portion.
In this structure, enlargement stress 11 accompanying the press-fitting of subsequent lens 8b first acts to enlarge lens barrel portion 31 at the side of lens 8b than step 10a. In line with this enlargement, enlargement stress 11 further acts to enlarge lens barrel portion 33 at the side of lens 8a than step 10a.
More specifically, in the conventional structure shown in
In addition, reduction of the effect of enlargement stress 11 applied to step 9acatching preceding lens 8a also enables the suppression of deviation of optical axis 23 of preceding lens 8a due to this enlargement stress 11. Accordingly, variations in optical characteristics due to assembly of the lens unit can be suppressed.
Ridge 12a in through-hole 6 formed by providing third step 10a may be curved. Ridge 12b in through-hole 6 formed by providing fifth step 10b may also be curved.
The lens unit of the present invention establishes a light path with respect to a light beam entering lenses 8a, 8b, and 8c disposed inside through-hole 6. Provision of steps 10a and 10b in the light path tends to cause flare due to diffused reflection at these steps. As a countermeasure, ridges 12a and 12b of steps 10a and 10b protruding in through-hole 6, which are a major cause of diffused reflection, may be curved. This effectively suppresses diffused reflection, and also suppresses deterioration of optical characteristics of the lens unit.
Still more, the upper and lower ends of sloped area 16 may conform to ends of first step 15a and second step 15b. Furthermore, at least upper or lower ends of sloped area 16 may be curved.
The structure of the lens unit in the second exemplary embodiment of the present invention is detailed next. In
The same effect is also achievable when the upper and lower ends of this sloped area 16 conform to ends of steps 15a and 15b. In addition, diffused reflection in a light path can be effectively suppressed by applying an aforementioned curved structure also, to ridge 17 formed at the upper end or lower end of this sloped area 16, and thus deterioration of optical characteristics of the lens unit can be suppressed.
In the aforementioned first exemplary embodiment, although not particularly illustrated, lenses 8a, 8b, and 8c are press-fitted into lens barrel 7 in a structure such that an internal-wall shape of through-hole 6 substantially conforms to the outer-periphery shape of lenses 8a, 8b, and 8c, and thus the entire side faces of the outer periphery of the lenses tightly contact the inner wall of the through-hole when the lenses are press-fitted.
On the other hand, in the third exemplary embodiment, multiple protrusions 19 protruding inward are provided along area 18 where the outer-periphery face of lenses 8a, 8b, and 8c tightly contact the inner wall of the through-hole. Lenses 8a, 8b, and 8c tightly contact the inner wall of through-hole 6 via these protrusions 19. Also in this exemplary embodiment, the same effect and advantage as the first exemplary embodiment and the second exemplary embodiment are achievable by providing steps 10a and 10b in through-hole 6.
When lenses 8a, 8b, and 8c are press-fitted into through-hole 6 via protrusions 19, as shown in
As shown in
In addition, in this lens unit, six protrusions 19 and six spaces 20 formed by these protrusions 19 are provided at equal intervals in an axisymmetrical arrangement with respect to optical axis 23 of lenses 8a, 8b, and 8c. Directions of contact stress 21b generated at contact portions of each protrusion 19 and lenses 8a, 8b and 8c are thus dispersed in directions equally dividing lenses 8a, 8b, and 8c. The vectorial sum therefore theoretically becomes zero. Accordingly, deviation in the optical axis of lenses 8a, 8b, and 8c caused by the contact stress exerted by each contact portion onto lenses 8a, 8b, and 8c is preventable. The productivity of the lens unit can thus be further improved.
In the lens unit in which lenses 8a, 8b, and 8c are press-fitted into lens barrel 7 for integration, each lens 8a, 8b, and 8c and lens barrel 7 may be anchored in position by adhesive so as to further improve the integrity of each lens 8a, 8b, and 8c and lens barrel 7. In this case, the use of space 20 for adhesion, as shown in
In addition, in this lens unit, it is preferable that air passes through easily in front and back of lenses 8a, 8b, and 8c in lens barrel 7, taking into consideration the risk of condensation on lenses 8a, 8b, and 8c. To ensure proper air flow, at least one space 20 in multiple spaces 20 is preferably made non-adhesion area 25. When providing this non-adhesion area 25, stress dispersion is also considered in the same way as previously described using
Since lenses 8a, 8b, and d8c are press-fitted to protrusions 19, adhesion area 24 and non-adhesion area 25 are completely separated by the presence of protrusion 19 between these areas. Accordingly the adhesive in adhesion area 24 does not creep over non-adhesion area 25.
Still more, this lens unit has a structure in which six protrusions 19 are provided in lens barrel 7 for contacting lenses 8a, 8b, and 8c. To securely hold lenses 8a, 8b, and 8c with respect to lens barrel 7, it is preferable to provide three or more protrusions 19. Taking into account the alternate arrangement of adhesion area 24 and non-adhesion area 25 in spaces 20, however, it is preferable to provide four or more protrusions 19. In addition, with consideration to at least three-point support by adhesion areas 24, it is preferable to provide six or more protrusions 19.
Furthermore, if the shape of through-hole 6 in this lens barrel 7 is designed to be polygonal, mold shape of lens barrel 7, particularly the mold shape for the side of through-hole 6, can be made by linearly cutting a side face of a cylindrical mold. This achieves good processability and ensures high molding accuracy. The productivity of the lens unit can thus be improved.
The lens unit of the present invention improves its productivity, and can thus be effectively applied to image pickup devices in a range of electronic apparatuses including compact high-performance digital cameras and mobile cameras.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-323361 | Nov 2004 | JP | national |
| 2005-296279 | Oct 2005 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP05/20272 | 11/4/2005 | WO | 00 | 3/21/2007 |
