JPH0429201A - Resin mold lens - Google Patents

Abstract

PURPOSE:To absorb compression and play due to the difference in coefficient of thermal expansion to stabilize the optical function of a lens by extending an elastically deformable hook part, with which a lens fixing part provided on the outside periphery of a lens part is attached to a lens barrel, to the outside of the lens fixing part. CONSTITUTION:With respect to a collimator lens 11, a central lens part 12, a peripheral part 13 surrounding this lens part 12, and elastically deformable hook parts 14 which are radially extended from the peripheral part 13 in four directions and are slightly bent forward are constituted as one body. An annular recessed groove 16 is provided in the inside face of a lens barrel 15 in which the collimator lens 11 is stored, and front end parts of hook parts 14 of the collimator lens 11 are fitted to the recessed groove 16. The hook parts 14 of the collimator lens is inserted into the barrel 15 in the narrowed state and is pushed forward in the direction of an arrow A, thereby fixing the collimator lens 11 in the barrel 15. Since elastically deformable hook parts 14 formed around the lens part 12 as one body are provided in this manner, destruction of the lens 11, defocusing, or the like due to thermal deformation is avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a resin molded lens used, for example, as a collimator lens used in a laser beam printer or a pickup lens for an optical disk.

"Prior Art" For example, in a laser beam printer that records an image by scanning a laser beam, a collimator lens is used to convert the laser beam into parallel light.

FIG. 8 schematically shows a laser scanning device of a conventional laser beam printer, in which a laser beam emitted from a semiconductor laser light source 1 modulated by an image signal is made into parallel light by a collimator lens 2, and then The polygon mirror 3 performs deflection scanning, and the imaging lens 4 forms an image on the recording medium 5 to perform main scanning.

The collimator lens 2 used in such a laser scanning device is composed of a plurality of glass lenses 6a, 6b, 6c, a precision spacer 7, a retaining ring screw 8, a lens barrel 9, etc., as shown in FIG. and unitized.

However, the collimator lens unit constructed by combining a plurality of glass lenses 68 to 6c in this way requires strict control of the tightening torque of the retainer ring screw 8 during assembly, and also requires cone processing etc. Because it requires precision finishing, it is not suitable for mass production. Therefore,
Instead of using multiple lenses, a gradient index lens is used to create a single lens, reduce the number of assembly steps, and improve mass production.In this case, assembly is easy, but Gradient index lenses have the disadvantage that they are more expensive than glass lenses.

On the other hand, recently, in order to reduce the size, weight, and cost of collimator pickups, attempts have been made to use resin molded lenses made of acrylic or polycarbonate-based synthetic resins as collimator lenses. However, since the collimator lens must strictly suppress positional changes in the optical axis direction, that is, defocus, the lens barrel 9 is required to be made of a material with as low a coefficient of thermal expansion as possible. It is built.

Therefore, when a resin molded lens made of acrylic or polycarbonate resin is used, a large difference in thermal expansion will occur between the lens and the lens barrel 9. For example, the coefficient of thermal expansion of acrylic is 5 to 9 x 10-'cm/cm/'C, so if an acrylic lens with an outer diameter of 10 mm is used, the outer diameter of the lens will increase to 28 μm due to a temperature change of ±40°C.
This causes a dimensional change. On the other hand, when this is combined with a steel lens barrel, the coefficient of thermal expansion of steel is 1.5XlO-5cm/
cm/'C, the dimension of the lens barrel 9 is approximately 6 μm.
Change. Therefore, at high temperatures, the acrylic lens is approximately 22
μm compressed, and conversely, at low temperatures, the distance between the lens barrel 9 and the lens is approximately 22 μm.
This will result in a gap of m.

[Problems to be Solved by the Invention] As described above, for example, when a collimator lens is molded from a resin such as acrylic or polycarbonate, the lens may be deformed or destroyed at high temperatures due to the difference in thermal expansion coefficient between the lens and the lens barrel 9. On the other hand, at low temperatures, a gap is created between the lens and the lens barrel 9 due to the difference in shrinkage, which causes the lens to move in the axial direction, causing the focus position to be out of alignment. Furthermore,
When fixing resin lenses with adhesive, if the organic solvent component of the adhesive causes the lens to deteriorate, or if the lens peels off due to insufficient adhesive, or if the adhesive exceeds the appropriate amount, the adhesive may not reach the lens surface. There are problems such as rotation.

The purpose of the present invention is to stabilize the optical function of the lens by absorbing the compression and wobble caused by the difference in thermal expansion coefficient between the resin molded lens and the lens barrel, and also to eliminate the adverse effects caused by adhesives. Our objective is to provide resin molded lenses.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the resin molded lens according to the present invention includes a lens fixing part provided on the outer periphery of the lens part, and a lens fixing part for attaching the lens fixing part to the lens barrel. The present invention is characterized in that an elastically deformable hook portion extends outward from the lens fixing portion.

[Function] When the resin molded lens having the above-mentioned configuration is housed in the lens barrel, the elastic deformation of the hook portion absorbs the compressive force applied to the lens due to the difference in coefficient of thermal expansion with the lens barrel at high temperatures. Conversely, at low temperatures, it absorbs the backlash that occurs between the lens and the lens barrel.

[Example] The present invention will be described in detail based on the example illustrated in FIGS. 1 to 7.

Figure 1 shows a collimator lens unit to which the present invention is applied, Figure 2 is a front view of the collimator lens alone, and Figure 3 is a front view of the collimator lens alone.
The figure is a side view. The conometer lens 11, which is molded from synthetic resin such as acrylic or polycarbonate, includes a central lens portion 12, a peripheral portion 13 surrounding the central lens portion 12, and a peripheral portion 13 that extends radially in four directions in the embodiment and extends forward. An elastically deformable hook portion 14 slightly bent
are integrally constructed. This collimator lens 11
An annular groove 16 is provided on the inner surface of the lens barrel 15 that accommodates the collimator lens 11.
4 are fitted. Note that an optical aperture 17 having an appropriate diameter is provided at the front end of the lens barrel 15, and a semiconductor laser light source 18 is disposed at the rear of the lens barrel 15.

When installing the collimator lens 11 inside the lens barrel 15,
If the hook part 14 of the collimator lens 11 is inserted into the lens barrel 15 in a shortened state and pushed forward in the A direction, the tip of the hook part 14 will fit into the groove 16, and even after this fitting, the hook part will remain intact. Since the lens 14 is in an elastically deformed state, the collimator lens 11 is fixed within the lens barrel 15 by its elasticity. Here, the inner diameter of the lens barrel 15 is φD, the outer diameter of the collimator lens 11, that is, the distance between the tips of the hook portions 14 is φd, the amount of thermal contraction of the collimator lens 11 is △dc, and the amount of thermal contraction of the lens barrel 15 is △Dc. As, φd〉φD−ΔDc+Δd
c = il), no gap is created between the collimator lens 11 and the lens barrel 15 at low temperatures, and movement of the collimator lens 11 can be avoided. In addition, at high temperatures, the collimator lens 11 thermally expands more than the lens barrel 15, so compressive stress is generated between the collimator lens 11 and the lens barrel 15, and a bending moment M acts on the hook portion 14, which increases the allowable stress Oa of the material. The length 2, thickness h, and width of the hook portion 14 may be selected so as not to exceed the length 2, thickness h, and width.

From the theoretical formula for a leaf spring in material mechanics, the allowable deformation amount δa of the hook portion 14 is expressed by the following formula (2). However, E is Young's modulus.

δa = 212” oa /3hE
-(2) Therefore, collimator lens 1 at high temperature
If the amount of thermal expansion of the outer diameter φd of the lens 1 is ΔdH and the amount of thermal expansion of the lens barrel 15 is 800, then φd+ΔdH-(to φD+80)>δa-(31).

If the outer diameter φd of the collimator lens 11 and the shape of the hook portion 14 are selected so as to satisfy the conditions of these formulas (1) to (3), the gap between the collimator lens 11 and the lens barrel 15 that occurs at low temperatures can be reduced. In addition, compressive force applied to the collimator lens 11 at high temperatures can be avoided.

FIG. 4 shows a second embodiment, in which the collimator lens 11 has a skirt-like hook portion 14' integrally molded around the lens portion 12, and this hook portion 14° has a structure that allows easy elastic deformation. A slit 19 for guiding the lens part 12 and a tapered part 20 for guiding insertion into the lens barrel 15 are provided, and an abutting part 21 for positioning is provided around the lens part 12. On the other hand, a groove 22 for accommodating the collimator lens 11 is provided on the inner surface of the lens barrel 15. A hook portion 14 is attached to the rear groove wall surface 24.
° The rear edge is locked.

To fit the collimator lens 11 into the lens barrel 15, insert a cylindrical jig P into the hook portion 14'' and push the collimator lens 11 into the lens barrel 15 in the six directions of the arrows.
The abutting portion 21 abuts against the groove wall surface 23 and the hook portion 1
The 4° rear end edge can be forcibly locked to the groove wall surface 24. In this state of several units, the hook portion 14' has elasticity both in the diameter direction and in the optical axis direction, so it can absorb deformation due to the difference in thermal expansion coefficient between the collimator lens 11 and the lens barrel 15. I can do it. Further, since the front side and the back side of the collimator lens 11 can be clearly distinguished structurally, there is no possibility of erroneously inserting the collimator lens 11 in the direction of insertion during assembly.

FIG. 5 shows a third embodiment of the present invention, in which the collimator lens 11 housed in the lens barrel 15 has a retaining ring screw 2.
It is fixed by 5. Here, if the lens barrel 15 and the retainer ring screw 25 are made of a material with a low coefficient of thermal expansion, the change in the gap ΔC1 between the lens barrel 15 and the retainer ring screw 25 due to thermal deformation will be extremely small, and the collimator lens 11 hook part 1
The elastic deformation of the collimator lens 11 itself can absorb the thermal deformation of the collimator lens 11 itself, making it possible to suppress changes in the radial direction. On the other hand, the change in the axial direction is caused by the collimator lens 1
1 abuts against the lens barrel 15, and further screws in the retaining screw 25 until it abuts against the collimator lens 11, thereby regulating the collimator lens 11.

6 and 7 show the fourth embodiment, FIG. 6 shows the collimator lens 11 housed in the lens barrel 15, and FIG.
The figure is a side view showing the original form of the collimator lens 11.

In this embodiment, a step 26 is provided at the tip of each hook portion 14 in order to avoid the problem of leaving gate marks on the material when the collimator lens 11 is injection molded.

In this case, the collimator lens 11 is attached by fitting into the groove 27 on the inner surface of the lens barrel 15, but in this state, there is a gap ΔC2 between the tip of each hook portion 14 and the inner surface of the lens barrel 15.
Therefore, it is also possible to take out the collimator lens 11 from the lens barrel 15 by using this gap to bend the hook portion 14 in the direction of arrow H and push it out in the direction of J.

Furthermore, the collimator lens 11 can be removed by providing a through hole 28 on the outer periphery of the lens barrel 15 at a position facing each hook portion 14, and by bending each hook portion 14 from there.

[Effects of the Invention] As explained above, the resin molded lens according to the present invention avoids breakage of the lens and loss of focus due to thermal deformation due to the elastically deformable hook portion integrally molded around the lens portion. I can do it.

In addition, the lens can be assembled into the lens barrel extremely easily, which has the advantage that the number of parts can be reduced, and costs can be significantly reduced.

[Brief explanation of drawings]

1 to 7 show examples of the resin molded lens according to the present invention, and FIG. 1 is a sectional view of the first example, and FIG.
The figure is a front view of the original shape of the lens, the third figure is a side view, and the fourth figure is a front view of the original shape of the lens.
The figure is a sectional view of the second embodiment, the fifth section is a sectional view of the third embodiment, FIG. 6 is a sectional view of the fourth embodiment, and FIG. 7 is a side view of the original shape of the lens. FIG. 8 is a perspective view of a laser scanning device of a conventional laser beam printer, and FIG. 9 is a sectional view of a conventional collimator lens unit. Symbol l is a collimator lens, 12 is a lens portion, 14 is a hook portion, 15 is a lens barrel, 16 is a concave groove, 17 is an optical diaphragm, 1
9 is a slit, 20 is a tapered portion, 21 is an abutment portion, 2
2 is a concave groove, 23 and 24 are groove wall surfaces, and 25 is a retaining ring screw. Patent applicant Canon Co., Ltd. Figure 1 Figure 5 Figure 6

Claims (1)

[Claims] 1. A resin molded lens characterized in that a lens fixing part is provided on the outer periphery of the lens part, and an elastically deformable hook part for attaching the lens fixing part to a lens barrel extends outside the lens fixing part. .