JP2013145123A - Optical system with wide-angle reflection coaxial illumination - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical system with a wide-angle reflection coaxial illumination securing a wide illumination area without sacrifice of WD (Working Distance) in the optical system with the coaxial illumination formed by combining an image capture optical system of an area sensor camera with a surface light source coaxial illumination device.SOLUTION: The wide-angle reflection optical system with coaxial illumination includes: an image capture optical system for forming an image of an inspection object on an area sensor camera; a branch optical element disposed rearward a lens that is closest to the inspection object side of the image capture optical system, and located on an optical axis; and a surface light source coaxial illumination light source causing an illumination luminous flux to enter the branch optical element from a direction of crossing with the optical axis of the image capture optical system.

Description

  The present invention relates to an optical system with a wide-angle reflective coaxial illumination used for an alignment process and an inspection process when bonding an object to be inspected (for example, an electronic device such as a semiconductor, LED, liquid crystal, and biochip).

  In this type of optical system with coaxial illumination, a half mirror is placed on the optical axis of the image capturing optical system of the CCD camera, and fiber illumination light is incident through the half mirror. However, the fiber illumination light has a problem that the illumination area is narrow and the reflected light (inspection light) from the work does not enter the camera (image capturing optical system) with a slight inclination of the work. When the image capturing optical system is a zoom (magnification) optical system, the same problem occurs particularly when the inspection area is wide and the magnification is low.

  For example, Patent Literature 1 and Patent Literature 2 are known as surface light source coaxial illumination devices that have a wide illumination area and allow tilting of a workpiece. This surface light source coaxial illuminating device is designed to make a large number of LED lights arranged in a matrix form enter a work via a half mirror, and is used by positioning a half mirror on an image capturing optical system of a CCD camera.

  Further, the conventional optical system with coaxial illumination moves the CCD camera and the entire image capturing optical system in the optical axis direction to adjust the distance from the workpiece and adjust the focus.

JP 2006-133052 A JP 2011-106912 A

  However, the conventional apparatus in which the surface light source coaxial illumination device is inserted between the image capturing optical system of the CCD camera and the work is in a condensing light path by the front lens (most condensing lens on the work side) of the image capturing optical system. Since the surface light source coaxial illumination device is inserted (between the front lens and the workpiece), the working distance (WD, the distance from the front lens to the workpiece) is sacrificed, and the workability is poor.

  In addition, the conventional focus adjustment mechanism of the optical system with coaxial illumination guides the entire lens barrel of the image capturing optical system equipped with the CCD camera in the optical axis direction (direction parallel to the optical axis) by the guide mechanism. As a result, both the movable part and its guide mechanism become large and heavy, and it is difficult to improve accuracy while reducing the weight.

  The present invention provides an optical system with coaxial illumination that combines an image capturing optical system of a CCD camera and a surface light source coaxial illumination device, while ensuring a wide illumination area without sacrificing WD, even if the surface to be inspected is slightly inclined. An object of the present invention is to obtain an optical system with a wide-angle reflection coaxial illumination that has a highly accurate and compact focus adjustment mechanism with less illumination unevenness.

  In the present invention, a branching optical element is positioned on the optical axis behind the lens (front lens) closest to the object to be inspected in an image capturing optical system for forming an image of the object to be inspected on a CCD camera. The present invention has been completed based on the viewpoint that the surface light source illumination light beam is incident on the branch optical element.

  That is, the optical system with a wide-angle reflection coaxial illumination of the present invention is an image capturing optical system that forms an image of the inspection object on the area sensor camera, and behind the lens on the most inspection object side of the image capturing optical system, A branch optical element disposed on the optical axis, and a surface light source illumination light source composed of a plurality of light emitters that make the illumination light beam incident on the branch optical element from a direction intersecting the optical axis of the image capturing optical system; It is characterized by having.

  In the optical system with wide-angle reflective coaxial illumination according to the present invention, the lens diameter closest to the object to be inspected is that the illumination light beam reflected by a plane inclined by ± 1 ° to ± 3 ° from the direction orthogonal to the optical axis is the most inspected. It is desirable to set the size to be incident on the lens on the object side.

  It is preferable to provide a focus adjustment mechanism that adjusts the focus by moving the lens closest to the object to be inspected in the optical axis direction.

  The lens barrel frame supporting the focus adjustment mechanism and the illuminator frame of the surface light source illumination light source are coupled together so as not to cause relative movement.

  The image capturing optical system can be a variable magnification optical system. In this zoom optical system, a branching optical element is arranged behind the lens group closest to the object to be inspected.

  The branching optical element is a half mirror, and it is practical to arrange a diffusion plate between the half mirror and the surface light source illumination light source in order to make the light quantity distribution more uniform.

  The optical system with wide-angle reflection coaxial illumination according to the present invention has a branch optical element behind the lens (front lens) closest to the inspection object in the image capturing optical system that forms an image of the inspection object on the area sensor camera. Since the included optical system with wide-angle reflective coaxial illumination is inserted, the distance (WD) from the front lens to the object to be inspected is not sacrificed by the optical system with wide-angle reflective coaxial illumination. In addition, the lens diameter of the front lens is set to a size such that the illumination light beam reflected by a plane inclined by ± 1 ° to ± 3 ° from the direction perpendicular to the optical axis is incident on the lens closest to the object to be inspected. Therefore, even if the surface to be inspected is slightly inclined, the occurrence of uneven illumination is small, so that adjustment of the arrangement of the object to be inspected becomes unnecessary, and workability can be improved. Furthermore, the optical system with wide-angle reflective coaxial illumination of the present invention moves the front lens in the optical axis direction to adjust the focus, thereby reducing the mass of the movable part and making the focus adjustment mechanism compact. Accuracy can be increased.

It is a perspective view of the optical system with a wide angle reflective coaxial illumination which concerns on one Embodiment of this invention. It is a front view of the optical system with the same wide-angle reflective coaxial illumination. FIG. 3 is a cross-sectional view taken along a cutting line III-III in FIG. 2. FIG. 4 is a cross-sectional view taken along a cutting line IV-IV in FIG. 3. It is a figure which shows the structure of one Embodiment of the optical system with the same wide angle reflective coaxial illumination, and the structure of an illumination optical system. It is an illumination ray tracing diagram of the optical system with the same wide-angle reflection coaxial illumination.

  1 to 6 show an embodiment of an optical system 10 with a wide-angle reflection coaxial illumination according to the present invention. The optical system 10 with wide-angle reflection coaxial illumination integrally has a lens barrel machine frame 20 and an illuminator frame 30. A mount (C mount) 22 for connecting a CCD camera (area sensor camera) 21 is provided at the upper end of the barrel machine frame 20 in the figure. For example, an image capturing optical system (inspection optical system) 23 for forming an image of the surface of a printed wiring board (W) on the CCD camera 21 (imaging surface 21a) is housed. In this embodiment, the image capturing optical system 23 is composed of a variable magnification (zoom) optical system, and sequentially from the CCD camera 21 side, a fixed lens group 23a, variable magnification lens groups 23b, 23c movable in the optical axis O direction, A fixed lens group 23d and a movable objective lens group (front lens) 23e are provided. By moving the zoom lens groups 23b and 23c in the optical axis direction along a predetermined movement locus, the imaging magnification of the work W on the CCD camera 21 changes. The objective lens group 23e is a focus lens group that moves in the optical axis direction to adjust the focus, and the image capturing optical system 23 is an optical system that forms an image of the workpiece W on the imaging surface 21a of the CCD camera 21 as a whole. It is composed.

  A focus adjustment mechanism 40 that moves the objective lens group 23e shown in FIGS. 3 and 4 back and forth in the optical axis direction will be described. The lens frame 41 that supports the objective lens group 23e is disposed in a fixed barrel (machine frame) 42 fixed to the illuminator frame 30 (lens barrel machine frame 20) so as to be movable in the optical axis direction, and protrudes from the outer periphery. The plurality of cam follower pins 41a that pass through a straight guide groove (through hole) 42a formed in the optical axis direction in the fixed barrel 42 and are rotatably fitted in the fixed barrel 42 The cam groove (lead groove, through hole) 43a is fitted. The cam ring 43 is connected to a focus operation ring 44 fitted outside so as to rotate integrally. When the focus operation ring 44 is rotated, the cam follower pin 41a restrained by the cam groove 43a and the linear guide groove 42a moves forward and backward in the optical axis direction, and the objective lens group 23e moves forward and backward in the optical axis direction to adjust the focus. Is made.

  Since the present embodiment is characterized by the fact that the objective lens group 23e of the image capturing optical system is movable, an example of the moving mechanism has been described. However, the present invention is not limited to the focus lens group (objective lens group 23e). ) Does not ask the movement mechanism itself. Similarly, various movement mechanisms (and variable magnification optical systems) of the variable magnification lens group are well known, and the present invention does not ask any question about the variable magnification mechanism (lens movement mechanism), and therefore illustration and description thereof are omitted. .

  The illuminator frame 30 includes a half mirror (branching optical element) 31 that forms an angle of 45 ° with respect to the optical axis O of the image capturing optical system 23, and a surface light source coaxial illumination device 32 that provides an illumination light beam to the half mirror 31. It is supported. The surface light source coaxial illumination device 32 has an illumination optical axis S orthogonal to the optical axis O, and a large number of LEDs arranged in a matrix on a plane orthogonal to the illumination optical axis S (parallel to the optical axis O). A surface light source illumination light source composed of a (light emitter) 33 and a diffuser plate 34 that is positioned between the LEDs 33 and the half mirror 31 and that is orthogonal to the illumination optical axis S and makes the light amount distribution uniform. . The lens barrel frame 20 and the illuminator frame 30 are rigidly coupled so that relative movement does not occur, and the relative positional relationship between the half mirror 31 and the multiple LEDs 33 (the half mirror 31 and the diffusion plate 34) is fixed. ing. The objective lens group 23e also has a function of illuminating the work W by condensing the illumination light beam reflected by the half mirror 31, and FIGS. 1 and 6 show an imaging area on the surface of the work W and an illumination area by the illumination light beam. showed that.

  In this embodiment, the diameter of the objective lens group 23e is such that even if the plane orthogonal to the optical axis O is inclined ± 2 ° (± 1 ° to ± 3 °) from the direction orthogonal to the optical axis O, The reflected illumination light beam is set to a size that enters the objective lens group 23e. When the objective lens group 23e and the half mirror 31 are orthogonally projected onto a plane orthogonal to the optical axis O (as viewed from the CCD camera 21 side), the contour of the half mirror 31 is within the effective outer shape (contour) of the objective lens group 23e. It is set to a size relationship that fits. As a result, as apparent from FIGS. 3 to 6, the diameter of the objective lens group 23e is set sufficiently larger than the diameters of the other lens groups 23a to 23d. As a result, most of the illumination light beam reflected by the half mirror 31 is transmitted through the objective lens group 23e to illuminate the work W, so that a large illumination area can be obtained, and even if the work W is slightly tilted, the reflected light is reflected. Light enters the fixed lens group 23d from the objective lens group 23e, and further reliably enters the CCD camera 21 via the movable variable lens groups 23c and 23d and the fixed lens group 23a.

  The above optical system 10 with wide-angle reflection coaxial illumination uses a CCD camera 21 coupled to a connection mount 22 of a lens barrel frame 20. When a large number of LEDs 33 emit light, illumination light that can be regarded as a surface light source is diffused by the diffuser plate 34, enters the half mirror 31, and is reflected toward the objective lens group 23e. The illumination light beam from the surface light source coaxial illumination device 32 is irradiated onto the workpiece W through the objective lens group 23e, and the reflected light forms an image on the imaging surface 21a of the CCD camera 21 through the image capturing optical system 23 (FIG. 5, FIG. 5). FIG. 6). Since the work W surface can be widely illuminated (a large illumination area including an imaging area is secured) with the illumination light flux of the surface light source coaxial illumination device 32 (FIGS. 1 and 6), the work W surface is somewhat (in the illustrated embodiment, the optical axis). Even if it is tilted (about ± 2 ° from the direction orthogonal to O), the necessary illumination light beam is sufficiently incident on the image capturing optical system 23, and no vignetting (insufficient light quantity) of the captured image does not occur (FIG. 6).

  The optical system 10 with the wide-angle reflective coaxial illumination described above is a distance (working distance) from the objective lens group 23e to the workpiece W, as compared with the conventional device in which the surface light source coaxial illumination device is arranged on the object side of the objective lens group 23e. WD) can be made longer. For this reason, a freedom degree arises in the arrangement position of the workpiece | work W, and workability | operativity at the time of approaching the workpiece | work W or the element on the workpiece | work W can be improved.

  Further, the optical system 10 with the wide-angle reflection coaxial illumination of the present embodiment adjusts the focus by moving the objective lens group 23e back and forth in the optical axis direction by the rotation of the focus operation ring 44 of the focus adjustment mechanism 40, so that other than the objective lens group 23e. The image capturing optical system, the lens barrel frame 20, the CCD camera 21, the illuminator frame 30, the surface light source coaxial illumination device 32, and the fixed barrel 42 do not move. For this reason, it is possible to reduce the mass of the movable part, improve the operability, speed up the response, increase the accuracy, and reduce the size.

  In the above embodiment, the optical axis O of the image capturing optical system 23 and the illumination optical axis S of the surface light source coaxial illumination device 32 are orthogonal to each other, but the optical axis O and the illumination optical axis S are the surface light source coaxial illumination device 32. As long as the surface illumination light beam from the light beam is irradiated onto the optical axis O. Further, the diffusion plate 34 of the surface light source coaxial illumination device 32 can be omitted. The surface light source coaxial illumination device 32 can also use an organic EL illumination panel as a surface light source illumination light source composed of a large number of light emitters. Further, in the present invention, a branching optical element that can split a light beam, such as a beam splitter, can be used instead of the half mirror 31.

10 Optical system with wide angle reflective coaxial illumination 20 Lens barrel frame 21 CCD camera (area sensor camera)
21a Imaging surface 22 Connection mount 23 Image capturing optical system 23a Fixed lens group 23b 23c Variable magnification lens group 23d Fixed lens group 23e Objective lens group (lens closest to the object to be inspected, focus lens group)
30 Illuminator frame 31 Half mirror (branching optical element)
32 Surface light source coaxial illumination device (surface light source illumination light source)
33 LED
34 Diffuser 40 Focus adjusting mechanism 41 Lens frame 41a Cam follower pin 42 Fixed lens barrel (lens barrel frame)
42a Linear guide groove 43 Cam ring 43a Cam groove 44 Focus operation ring O Optical axis S of image capturing optical system Illumination optical axis W Workpiece (inspection object)
WD Working Distance

Claims (6)

An image capturing optical system for forming an image of the inspection object on the area sensor camera;
A branching optical element disposed on the optical axis behind the lens on the most inspection object side of the image capturing optical system;
A surface light source illumination light source composed of a number of light emitters that make illumination light beams incident on the branch optical element from a direction intersecting the optical axis of the image capturing optical system,
An optical system with a wide angle reflective coaxial illumination. 2. The optical system with wide-angle reflection coaxial illumination according to claim 1, wherein the lens diameter closest to the object to be inspected is an illumination beam reflected by a plane inclined by ± 1 ° to ± 3 ° from a direction orthogonal to the optical axis. An optical system with a wide-angle reflective coaxial illumination that is set to a size that is incident on the lens closest to the object to be inspected. 3. The optical system with wide-angle reflection coaxial illumination according to claim 1, further comprising a focus adjustment mechanism for adjusting the focus by moving the lens closest to the object to be inspected forward and backward in the optical axis direction. Attached optical system. 4. The optical system with wide-angle reflective coaxial illumination according to claim 3, further comprising a lens barrel frame that supports the focus adjustment mechanism and an illuminator frame of a surface light source illumination light source that are integrally coupled. Optical system. 5. The optical system with wide angle reflective coaxial illumination according to claim 1, wherein the image capturing optical system is a variable magnification optical system, and the rear of the lens group closest to the object to be inspected in the variable magnification optical system. An optical system with a wide-angle reflective coaxial illumination in which the branch optical element is disposed. 6. The optical system with wide-angle reflection coaxial illumination according to claim 1, wherein the branch optical element is a half mirror, and a diffusion plate is disposed between the half mirror and the surface light source illumination light source. Optical system with wide-angle reflective coaxial illumination.

Images