External lighting lens barrel with a lens barrel passing through it

Abstract

To provide a compact lens barrel which can be removably attached on the outer periphery of an image capturing lens barrel and is designed to irradiate an object under observation with illumination light from an annular light source through a tip-end lens in the lens barrel.SOLUTION: A lens barrel 1 provided herein comprises a first lens group 12, a transparent plastic light guide ring 14, and a second lens group 16 arranged in order from an object side of the lens barrel 1 so as to have a common optical axis 18. The transparent plastic light guide ring 14 has a reflective surface 14a having an inner edge extending into the inside of the lens barrel to reflect light from the outside toward the object side.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a lens barrel, and more particularly to a compact external illumination light passing-through lens barrel inside the lens barrel that can introduce annular illumination light mounted outside the lens barrel into the lens barrel and irradiate an observation object from the inside of the lens.

Background Art

[0002] In the inspection of semiconductor elements, high-density printed circuit boards, etc., reflected light from an observation object is acquired by an imaging element, and inspection information such as the position of each component, the presence or absence of defects, and the soldering state is obtained. Since the inspection information obtained varies greatly depending on the type and arrangement of the light source used at this time, it is important to configure the optical system using a light source suitable for the inspection object.

[0003] Conventionally, an illumination device such as annular illumination has been arranged at the tip of an imaging lens barrel to illuminate an inspection object. For example, in Patent Document 1, an optical device has been proposed in which annular illumination with light sources arranged at substantially equal intervals in the circumferential direction is arranged outside the lens, and the inspection object is illuminated from the outside of the lens. However, in this technique, since a larger illumination device is attached outside the diameter of the imaging lens barrel, the imaging lens portion becomes large, and it is not suitable for an environment where a small and compact design is required.

[0004] In addition, coaxial epi-illumination is used in which external illumination light is incident perpendicular to the optical axis from the side of the lens barrel, a half mirror prism is arranged on the internal optical axis, and the illumination light is reflected parallel to the optical axis by the half mirror surface and irradiated onto the observation object (for example, Patent Document 2). However, since the illumination light of this technique is perpendicular to the inspection object, there is a problem that it does not become the optimal illumination light in an application where it is desired to irradiate the inspection object with illumination light obliquely from the side.

[0005] In Patent Document 3, a lens barrel incorporating an annular light source with LED elements arranged in the circumferential direction has been proposed. However, since the annular light source is incorporated and the lens barrel is assembled, it is not possible to change the light for each inspection object or replace a faulty LED element, and the entire lens needs to be replaced for any change, resulting in problems in terms of usability and cost.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] An object of the present invention is to provide a compact lens barrel that irradiates illumination light from a detachable annular light source outside the imaging lens barrel through a front lens in the lens barrel onto an observation object.

Means for Solving the Problems

[0008] The present invention is a lens barrel in which a first lens group, a transparent plastic light guide ring, and a second lens group are arranged in order from the objective side of the lens barrel, and the first lens group, the transparent plastic light guide ring, and the second lens group have a common optical axis. The most main feature is that the inner edge portion of the transparent plastic light guide ring extends inside the lens barrel and has a reflecting surface that reflects light from the outside toward the observation object side.

[0009] In this lens barrel, it is preferable to further include a detachable annular LED light source body that emits illumination light from the outside of the transparent plastic light guide ring toward the reflecting surface.

[0010] Also, between the first lens group and the transparent plastic light guide ring, there is provided a circular first linear polarizer (polarizer) with a hole in the center, and between the second lens group and the first linear polarizer, there is provided a circular second linear polarizer (analyzer), and it is preferable that the linear polarization directions of the first linear polarizer and the second linear polarizer are orthogonal to each other.

Advantages of the Invention

[0011] The lens barrel of the present invention can provide a compact lens barrel that irradiates an observation object with optimal illumination light by reflecting external illumination light toward the observation object within the lens barrel by means of a transparent plastic light guide ring having a reflecting surface on its inner edge.

[0012] Also, by providing a thin annular LED light source body with a plurality of LEDs arranged detachably outside the transparent plastic light guide ring, a lens barrel in which only the light source can be replaced as needed can be provided.

[0013] Furthermore, between the first lens group and the transparent plastic light guide ring, there is provided a circular first linear polarizer (polarizer) with a hole in the center, and between the second lens group and the first linear polarizer, there is provided a circular second linear polarizer (analyzer), and by making these polarization directions orthogonal to each other, it is possible to prevent illumination light from being internally reflected within the lens barrel and incident on the imaging element, thereby preventing degradation of the captured image.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying out the Invention

[0015] Embodiments for carrying out the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing the configuration of an embodiment of the lens barrel according to the present invention. The lens barrel of the present invention is used for inspecting, for example, semiconductor elements and high-density mounting printed circuit boards. It irradiates light on an object to be observed and acquires the reflected light with an image sensor, and obtains inspection information such as the arrangement of each component in the object to be observed, the presence or absence of defects, and the soldering state. For example, when inspecting the presence or absence of defects in a planar structure, it is easier to detect by irradiating light obliquely rather than parallel to the lens optical axis because a shadow is more likely to be formed. However, the lens barrel of the present invention is not limited to the inspection of precision parts and can be used for various other applications. Therefore, FIGS. 1 to 5 are merely one example, and the present invention is not limited thereto.

[0016] The lens barrel 1 of the present invention has, from the objective side, a first lens group 12, a transparent acrylic (plastic) light guide ring 14, and a second lens group 16 arranged in order, and these have a common optical axis 18. The first lens group 12 is held by the first lens barrel portion 20, and the second lens group 16 is held by the second lens barrel portion 22. The first lens barrel portion 20, the transparent acrylic light guide ring 14, and the second lens barrel portion 22 are configured to be integrated by screwing. An annular LED light source body 24 is mounted on the outer periphery of the transparent acrylic light guide ring 14. The end portion of the second lens barrel portion 22 on the image sensor (camera) side has a male screw structure that can be mounted on a camera conforming to, for example, the C-mount standard. The first lens group 12 and the second lens group 16 are each appropriately designed according to the object to be observed and the required magnification when inspecting using the lens barrel 1, and usually consist of a combination of a plurality of lenses.

[0017] FIG. 2 is a cross-sectional view (a) and a conceptual diagram (b) showing the transparent acrylic light guide ring 14 shown in FIG. 1 alone. The transparent acrylic light guide ring 14 is formed by molding a transparent acrylic material, and the central portion located between the first lens barrel portion 20 and the second lens barrel portion 22 protrudes in the inner circumferential direction, and a reflecting surface 14a for reflecting the irradiation light from the side outside to the observation object side is formed at the inner edge portion thereof. This state is shown in FIG. 2(b). This reflecting surface 14a may reflect all the irradiation light from the outside of the lens barrel to the observation object side by satisfying the conditions of total reflection, or mirror vapor deposition may be performed on the inner surface of the transparent acrylic light guide ring 14 (only the upper side including the reflecting surface 14a) so that light is reflected. The angle, position, size, etc. of the reflecting surface 14a can be appropriately designed according to the observation object to be illuminated and the necessary image information. Further, the transparent acrylic light guide ring 14 can be removed from the first and second lens barrel portions 20 and 22 as needed and exchanged with another light guide ring having different reflecting surfaces.

[0018] Figure 3 is a schematic diagram showing the annular LED light source body 24 shown in Figure 1 alone. As shown in Figure 3, the annular LED light source body 24 of the present embodiment forms a cavity on the inner peripheral surface of an annular body having an inner circumference 24a with a diameter substantially equal to (strictly slightly larger than) the outer circumference of the transparent acrylic light guide ring 14, and a plurality of lighting chip LED light sources 24c arranged on a flexible wiring board 24b are arranged facing inward therein, and are covered with a transparent acrylic ring 24d from above. As shown in Figure 1, the outer surface of the first lens barrel portion 20 and the transparent acrylic light guide ring 14 are formed to be on the same plane, whereby the annular LED light source body 24 can be slid and inserted from the lens tip side (object surface side). In the present embodiment, as shown in Figure 1, when the annular LED light source body 24 is slid until it stops, it is configured to be in a fixed position where the LED irradiation light is introduced into the lens barrel. A wiring cable 24e extends from the flexible wiring board 24b to the outside of the unit, and this is connected to a power source (not shown). Further, by screwing and tightening a detachable fixing screw 24f into a screw hole penetrating the annular LED light source body 24, the annular LED light source body 24 can be fixed in a fixed position. In this way, the annular LED light source body 24 is configured to be detachable (that is, replaceable). Also, since a thin annular LED body can be attached to the outer circumference of the lens barrel for illumination, it is optimal for an environment where miniaturization and compactness are required. Figure 5 is a reference diagram showing the lens barrel 1 with the annular LED light source body 24 removed.

[0019] The LEDs built into the annular LED light source body 24 may be arranged at high density over the entire inner circumference of the body 24, or may be arranged at only several locations (for example, 3 to 4 locations). The emission color of this LED can be appropriately selected, such as R (red), B (blue), G (green), W (white), etc. Also, an IC chip may be provided on the wiring board 24b, or a control unit may be connected to the tip of the wiring cable 24e so that the emission color and intensity irradiated into the lens barrel can be changed. Since such control technology is well-known, detailed description in this specification is omitted.

[0020] Further optionally, the lens barrel 1 of the present embodiment incorporates two linear polarizers (polarizer 26 and analyzer 28) so that the internal reflection of the irradiation light by the first lens group 12 does not enter the imaging element and cause image degradation. As shown in FIG. 1, the lens barrel 1 includes a first linear polarizer 26 (polarizer) between the first lens group 12 and the transparent acrylic light guide ring 14, and a second linear polarizer 28 between the second lens group 16 and the first linear polarizer 26. FIG. 4 is a schematic diagram showing these linear polarizers 26 and 28 extracted. As shown in FIG. 4, the first linear polarizer 26 is a circular polarizer with a hole in the center, and polarizes the light emitted from the transparent acrylic light guide ring 14 in the first direction (horizontal direction in FIG. 4). On the other hand, the second linear polarizer 28 is a circular analyzer, and polarizes the light about to pass through the second lens group 16 in the second direction (vertical direction in FIG. 4). By making the linear polarization directions of the first linear polarizer 26 and the second linear polarizer 28 orthogonal to each other, the internal reflection light that passes through the polarizer, is reflected by the first lens group, etc., and travels toward the imaging element is blocked by the analyzer, and the internal reflection light does not reach the imaging element, preventing image degradation.

[0021] As described above, one embodiment of the present invention has been described in detail. However, the present invention is not limited to the above-described embodiments or examples and can be realized in various modified forms. For example, although the above embodiment has the first and second polarizing plates, these may not be provided in another embodiment. In the distribution form of the present invention, the lens barrel 1 does not necessarily have to be sold as a set with the annular LED light source body, and a light source suitable for the required conditions can be selectively purchased and used from among a plurality of different types of annular LED light source bodies. In addition, the material of the transparent plastic light guide ring is not limited to acrylic, and other transparent plastics such as polyethylene terephthalate (PET), polycarbonate (PC), and cycloolefin polymer (COP, for example, ZEONEX and ZEONOR (both are registered trademarks)) may also be used. Further, the angle, size, etc. of the reflecting surface 14a of this light guide ring can be appropriately determined according to the actual inspection object and the desired acquired information, etc., of the implementation environment. Furthermore, the lens barrel of the present invention is not limited to the optical inspection of precision parts, and can also be designed for other applications such as other close-up lenses.

Industrial Applicability

[0022] The lens barrel of the present invention provides a compact imaging illumination lens barrel by detachably attaching a thin annular LED light source body outside the imaging lens barrel as an external illumination light source, and can be suitably used for inspection applications such as semiconductor elements and high-density mounted printed circuit boards.

Explanation of Signs

[0023] 1 Lens barrel 12 First lens group 14 Transparent acrylic (plastic) light guide ring 14a Reflecting surface 16 Second lens group 18 Optical axis 24 Annular LED light source body 26 First linear polarizing plate (polarizer) 28 Second linear polarizing plate (analyzer)

Claims

1. A lens barrel in which a first lens group, a transparent plastic light guide ring, and a second lens group are arranged in order from the object side of the lens barrel, the first lens group, the transparent plastic light guide ring, and the second lens group have a common optical axis, and the transparent plastic light guide ring has a reflecting surface whose inner edge extends inside the lens barrel and reflects light from the outside to the observation object side, the first lens group is held by a first lens barrel portion, the second lens group is held by a second lens barrel portion, and the first lens barrel portion and the second lens barrel portion are removably connected to the transparent plastic light guide ring. A lens barrel characterized by that.

2. In the lens barrel according to Claim 1, the lens barrel is characterized in that the first lens barrel portion and the transparent plastic light guide ring are configured such that their outer surfaces are on the same plane.

3. The lens barrel according to Claim 1 or 2 further includes a detachable annular LED light source body that emits illumination light from the outside of the transparent plastic light guide ring toward the reflecting surface, and the annular LED light source body is the first lens barrel portion and the transparent plastic light guide ring. A lens barrel characterized by being removably provided on the outer surface of the lens barrel.

4. In the lens barrel according to any one of Claims 1 to 3, a circular first linear polarizing plate with a hole in the center is provided between the first lens group and the transparent plastic light guide ring, and between the second lens group and the first linear polarizing plate. A circular second linear polarizing plate is provided, and the linear polarization directions of the first linear polarizing plate and the second linear polarizing plate are orthogonal to each other. A lens barrel characterized by that.

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