JPH0314646Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial field of application] The present invention relates to various optical devices such as optical head devices, and is a method for aligning multiple optical elements such as lenses with their optical axes aligned. The present invention relates to a fixed combination optical device.

[Background of the idea]

Various optical instruments use optical devices in which a plurality of optical elements such as lenses are arranged with their optical axes aligned. Generally, in this type of device, the peripheral portion of an optical element such as a lens is fixed. Therefore, in order to improve the accuracy of alignment of the optical axes of each optical element, it is necessary to minimize the deviation between the center position of the optical element with respect to its outer circumference and the optical axis of the optical element. The accuracy of assembly of the element and its support must be maintained. Therefore, the optical element itself must maintain high processing accuracy around the outer periphery around the optical axis, and must also maintain high processing accuracy for the lens barrel that holds the outer periphery of the optical element. The positioning accuracy of the elements must also be high, and skill is required to assemble the entire device, and the number of man-hours is also increased.

Further, in a device that fixes the peripheral portions of a plurality of optical elements such as lenses, the structure of the fixing portion is complicated, which may cause mechanical problems. FIG. 1 is a longitudinal cross-sectional view of an optical head device showing an example of this conventional problem. This optical head device is used in optical equipment such as an optical video disk device, an optical audio disk device, or a disk memory device. At the center of this optical head device, a plurality of lenses 1a, 1
b and 1c are arranged coaxially to form the optical device 1. Each lens 1a, 1b, 1c is a lens barrel 2
The upper and lower ends of the lens barrel 2 are connected to leaf springs 3 and 4 at predetermined intervals. The leaf springs 3 and 4 are fixed inside the cylindrical frame 5, and the elastic force of the leaf springs 3 and 4 allows the lens barrel 2 to move vertically within the frame 5. is supported by Further, a core 2a is integrally provided on the outside of the lens barrel 2, and a coil 6 is wound around the core 2a. A permanent magnet 7 is fixedly installed inside the frame 5, and the coil 6 is housed in a recess 7a of the permanent magnet 7.

In addition, 8 indicated by a two-dot chain line is a recording medium,
Information is recorded on its surface in a spiral or concentric pattern. The optical head device shown in FIG. 1 moves in the radial direction with respect to the rotating information medium 8,
The light from the semiconductor laser is transmitted through lenses 1a, 1b, 1c.
The information is read by focusing the information on the surface of the information medium 8. Focus adjustment control for focusing the laser beam as a minute spot on the recording surface of the recording medium 8 is performed by converting a focus error signal into an electrical signal by a focus error detection section (not shown) and sending it to the coil 6. This is done by applying a driving current. Then, the lens barrel moves up and down in response to changes in the magnetic force between the coil 6 and the permanent magnet 7.
Automatic focus adjustment is performed. The tracking adjustment control and the radial adjustment control are performed by moving the frame 5 in the left-right direction in FIG. 1 and in the front-rear direction with respect to the plane of the paper using a drive mechanism (not shown).

[Problem that the invention attempts to solve]

In this optical head device, lenses 1a, 1b,
In order to automatically adjust the relative positional relationship between the laser beam focused by 1c and the recording medium 8 so as not to deviate, that is, to perform proper automatic focus adjustment, the response speed of each member is increased. is required. Therefore, in focus adjustment control, it is required to reduce the weight of the support part of the optical device 1 (lenses 1a, 1b, 1c), and in radial adjustment control,
The weight of the entire mechanism within the frame 5 is required to be reduced.

However, in the conventional mechanism described above, the lenses 1a,
As long as 1b and 1c are fixed at their respective peripheries,
This makes it impossible to reduce the weight of the lens support section and to increase the control response speed.

Furthermore, as mentioned above, each lens 1a, 1b,
Since lens 1c is mounted with reference to its surrounding area, it is not possible to increase the accuracy of alignment of the optical axes of lenses 1a to 1c, and it is not possible to increase the accuracy of focusing the micro spot of the laser beam. . Conversely, in order to align the optical axes of the lenses 1a to 1c, it is necessary to increase the processing accuracy of the outer periphery of each lens.

The present invention was developed by focusing on the above-mentioned conventional problems, and is an optical system that has a simple structure, can fix multiple optical elements coaxially with high precision, and can reduce the overall weight. The purpose is to provide equipment.

[Specific measures to solve the problem]

The optical device according to the present invention is an optical device in which a plurality of optical elements such as lenses are arranged and fixed on their optical axes, and a support rod is inserted into a hole drilled in the optical axis of each optical element. Each of the optical elements is arranged and fixed with their optical axes aligned with each other with respect to a support rod, and the edge of one of the plurality of optical elements is held by a support member. It is.

[Effect]

In the above means, each of the plurality of optical elements such as lenses is continuously fixed with their optical axes aligned with each other with respect to the support rod. Therefore, in the case of a lens, it is not affected by the processing accuracy of the outer periphery,
Each is fixed with its optical axis aligned with high precision. Furthermore, in the case of a lens, even if a thin support rod is passed through the optical axis, the effect on the light condensing function etc. is almost negligible. Furthermore, since the edge of one of the plurality of optical elements is held by the frame, the size of the holding member for the lens or the like can be minimized, and the weight of the optical device can be reduced. Therefore, when implemented in an optical head device, the weight of movable parts such as focus adjustment operations can be reduced, and adjustment operations with high sensitivity can be realized.

〔Example〕

Embodiments of the present invention will be described below with reference to FIG. 2 and the following drawings.

FIG. 3 is a longitudinal sectional view of the optical device 10 according to the present invention, and FIG. 2 is a sectional view of an optical head device using this optical device.

The optical device 10 shown in FIG.
1, 12, and 13 are arranged and fixed on the optical axis. Each of the lenses 11, 12, 13 is provided with a small diameter hole 11a, 12a, 13a that passes through the optical axis. And each hole 11a, 12
A small-diameter support rod 14 is inserted into a and 13a. The holes 11a, 12a, 13a and the support rod 14 are
The diameter dimensions are finished so that they fit together with almost no gaps. Further, a spacer 15a is interposed between lenses 11 and 12, and a spacer 15b is interposed between lenses 12 and 13, and the distance between each lens is set to a predetermined value. A head 14a for preventing slipping off is integrally formed at one end of the support rod 14, and a fixing portion 14b is formed at the other end. This fixing portion 14b is of a screw type when the support rod 14 is made of metal, and is of an adhesive type when the support rod 14 is made of resin. Further, each lens 11, 12, 13 may be a glass lens or a plastic lens depending on the equipment to be equipped.

The optical head device shown in FIG. 2 includes the optical device 10 shown in FIG. Each lens 11,
A peripheral portion of the lens 12 located at the center of the lenses 12 and 13 is held by a support tube 21. The support tube 21 is formed to have an extremely short dimension compared to the lens barrel 2 shown in FIG. The support tube 21 is a frame body 22
The support tube 21 and the optical device 10 are supported by a plate spring 23 fixed inside the second frame, and within the range where the plate spring 23 is elastically deformed, the support tube 21 and the optical device 10 are
It is designed to be able to move up and down in the figure. A core 21a extending outward and downward is integrally formed in the support tube 21, and a coil 2 is attached to the outer periphery of the core 21a.
4 is wrapped. Further, a permanent magnet 25 is fixed inside the frame 22, and this permanent magnet 2
The coil 24 is inserted into the recess 25a of No.5.

A reflecting mirror (not shown) fixed to the frame 22 is provided at a lower position of the optical device 10 in FIG. 2, and the beam emitted from the semiconductor laser provided outside the frame 22 is , reflected by the reflecting mirror and passed through each lens 11, 12, 13,
The light is focused on a minute spot on the surface of the information medium (same as the one shown at 8 in FIG. 1) located above the lens 13. In the focus adjustment control, as in the conventional one shown in FIG. 1, the coil 24 is energized in response to a signal from the focus error detection section, and the optical device 10 is moved in the vertical direction in the figure by the driving force of the coil 24. , the laser beam is reliably focused on a minute spot on the recording surface of the information medium. Further, the tracking adjustment control and the radial adjustment control are performed by driving the entire frame 22 by a drive mechanism (not shown).

In the optical device 10 according to the present invention, the lens 11,
A support rod 14, its head 14a, a fixing portion 14b, and a spacer 15 are attached to the optical axis portions 12 and 13.
a, 15b, the optical characteristics are naturally different compared to the lens arrangement means shown in FIG. , 15b is made sufficiently thinner than the outer diameter of the lens, it will hardly affect the light condensing function. An analysis of this problem will be described below.

As shown in FIG. 4, when parallel light is applied to the convex lens L, the luminance distribution at the focal point F can be described by a curve as shown by an arrow A. Since the optical device 10 according to the present invention has the support rod 14 on the optical axis, it corresponds to a circular light-shielding plate M provided at the center of the lens L, as shown in FIG. Therefore, at the focal position of the lens L having this light shielding plate M,
If we set a surface that includes the x ₁ axis and y ₁ axis, and find the brightness at each point on this surface as a function of the distance x from the intersection F of the surface and the optical axis to that point, we can obtain the following formula. I′(x)=(2/πx) ² [J ₁ (πX)−sJ ₁ (πsx)
] ^2In the above formula, x=l ₁ r ₁ /λf {x is the distance from F in the focal plane (plane including the x ₁ axis and y ₁ axis)} {l ₁ : Effective diameter of lens L, r ₁ : Distance from the origin O in the focal plane (plane including x ₁ axis and y ₁ axis) λ: wavelength of light, f: focal length of lens L} ・s=l ₂ /l ₁ (lens effective diameter and light shielding plate l ₂ : Diameter of the light-shielding plate J ₁ (x): Represents the Betzel function of the first kind with degree 1.

FIG. 7 shows this as a graph.
In the figure, the horizontal axis represents x and the vertical axis represents I'(x).

As can be seen from this graph, if s is made small, that is, if the diameter l ₂ of the light shielding plate M is made sufficiently smaller than the effective diameter l ₁ of the lens L, the luminance distribution at the focal plane can be changed to the normal convex lens ( It is possible to approximate the brightness distribution of a lens with s=0. Therefore, in the optical device 10 shown in FIGS. 2 and 3, the head 14a of the support rod 14 and the spacer 15
By reducing the diameters of lenses a, 15b, etc., the optical characteristics of each lens 11, 12, 13 can be made practically acceptable.

In addition, in the above embodiment, the convex lenses 11, 12,
Although the optical device combining 13 was explained,
Depending on the equipment used, a convex lens L ₁ , a concave lens L ₂ , a prism P, etc. may be combined as shown in FIG. 6, and each optical element may be fixed by a support rod.

As described above, according to the present invention, the following effects can be achieved.

(1) Since there is a hole in the optical axis of the lens,
When processing the lens, the optical surface can be polished using this hole as a reference, which not only simplifies the processing, but also improves the precision of the lens by aligning the hole with the optical axis.

(2) Even if the positional relationship between the outer periphery of the lens and the optical axis is rough, the optical axis of each optical element can be aligned using the support rod as a reference, making lens processing easier. Cost reduction can also be achieved.

(3) Since the optical axes of each optical element are made to coincide with each other by the support rod, the structure of the optical element support part of the device can be simplified. Furthermore, since there is no need to align each optical element during assembly, assembly of various devices is also easier.

(4) Since a plurality of optical elements are fixed on a support rod and integrated, and the edge of one of the plurality of optical elements is held by the support member 21, the support member 21 can be reduced to the minimum shape. can. Therefore, the optical device 10 configured by the plurality of optical elements and the support member 21 can be made smaller and lighter.
Therefore, if this lightweight optical device 10 is used in an optical head device as shown in FIG. can be carried out quickly, and the sensitivity of the control operation of the optical device can be increased.

(5) When using plastic lenses etc. as optical elements, the three lenses 1 shown in Figure 3.
1, 12, 13, etc. can be simultaneously molded integrally with the support rod 14, and the molding process can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an optical head device equipped with a conventional optical device 1, and FIG. 2 is a sectional view of an optical head device equipped with a conventional optical device 1.
3 is a cross-sectional view of the optical device 10 according to the present invention, FIG. 4 is a side view of a lens for calculating the brightness distribution, and FIG. 6 is a side view showing an optical device according to another embodiment, and FIG. 7 is a brightness distribution diagram. 10... Optical device, 11, 12, 13... Optical element, 11a, 12a, 13a... Hole on optical axis,
14... Support rod, 14a... Head, 14b... Fixed part, 15a, 15b... Spacer, 21... Support tube, 22... Frame, 23... Leaf spring, 24...
Coil, 25...Permanent magnet.

Claims (1)

[Scope of utility model registration request] In an optical device consisting of a plurality of optical elements such as lenses arranged and fixed on their optical axes, a support rod is inserted into a hole drilled in the optical axis of each optical element, and each optical element is attached to the support rod. An optical device characterized in that the plurality of optical elements are arranged and fixed with their optical axes aligned as a reference, and the edge of one of the plurality of optical elements is held by a support member.