JPWO2020095843A1 - Coaxial lighting device - Google Patents

Abstract

In order to provide a coaxial lighting device that can widen the field of view while being compact and can simplify the adjustment work, the work W to be observed and the observation unit M for observing the work W are connected. The half mirror 1 obliquely arranged on the observation axis A1 and the half mirror 1 are irradiated with light from a direction different from that of the observation axis A1, and the light reflected by the half mirror 1 irradiates the work W. A light source 2 arranged so as to be formed, a lens 3 provided between the half mirror and the work, and a first aperture 4 provided between the light source 2 and the half mirror 1. The first aperture 4 is arranged at the focal point of the lens 3 on the irradiation axis A2 connecting the light source 2 and the half mirror 1.

Description

The present invention relates to a coaxial lighting device.

For example, as a lighting device for surface inspection, as shown in Patent Document 1, light emitted from a light source in a direction different from the observation direction is reflected by a half mirror in the same direction as the observation direction by a camera or the like. Coaxial illumination that illuminates the workpiece to be observed is known.

In such a coaxial lighting device, not only a light source and a half mirror, but also an optical element such as a lens is held in the housing, and for example, the image captured by the camera can be adjusted to be suitable for surface inspection. The relative positional relationship of is adjustable.

However, if a plurality of lenses such as a lens on the light source side and a lens on the camera side are provided, adjustment is required for each lens, which is troublesome and difficult to adjust so as to obtain an appropriate image.

Further, in order to increase the field of view in which the work can be observed, it is necessary to increase the size of each of the plurality of members, and the housing that holds them inside also becomes large, and as a result, the size of the coaxial illuminating device as a whole becomes large. .. In addition, the manufacturing cost will increase significantly as the size increases.

JP-A-2002-39956

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a coaxial lighting device capable of widening a field of view while being compact and simplifying adjustment work. do.

That is, the coaxial illumination device according to the present invention includes a half mirror obliquely arranged on an observation axis connecting a work to be observed and an observation unit for observing the work, and a half mirror from a direction different from the observation axis. A light source arranged so that the light reflected by the half mirror is irradiated to the work, a lens provided between the half mirror and the work, and the light source. A first aperture provided between the half mirror and the first aperture is provided, and the first aperture is arranged at the focal point of the lens on an irradiation axis connecting the light source and the half mirror. do.

In such a case, the telecentric optical system can be configured by the light source, the first diaphragm, and the lens to irradiate the work with parallel light, and the lens can be shared on the observation unit side as well. Therefore, the number of lenses used can be reduced as compared with the conventional coaxial illuminating device, and the labor of adjustment work can be reduced.

Further, since the number of parts can be reduced, it is possible to increase the field of view in the observation unit without making the coaxial illumination device so large.

Further, the light emitted from the light source can be applied to the work as parallel light, and the NA of the light source can also be adjusted by the first diaphragm. Therefore, for example, the brightness of the work observed in the observation unit can be easily adjusted as appropriate. For example, due to the presence of minute waviness on the surface of the work, it may be difficult for the reflected light or scattered light from the object to be observed or its surroundings to reach the observation portion. In such a case, the NA of the light source is increased so that the amount of reflected light or scattered light incident in the field of view of the observation unit is large so that the object to be observed is clear even if the surface is wavy. It becomes possible to catch it.

In order to simplify the adjustment work of the light applied to the work and facilitate the miniaturization of the entire apparatus, only the first diaphragm is provided as an optical element between the light source and the half mirror. Just do it.

In order to irradiate each point of the work with uniform and less uneven brightness, the light source has a flat light emitting surface, and the light emitting surface is the irradiation axis and the observation. It suffices if they are arranged so as to be orthogonal to the axis.

In order to further fine-tune the mode in which the light reflected or scattered by the work is observed in the observation unit, a second diaphragm is further provided between the half mirror and the observation unit. All you need is.

In order to prevent the surface of the work W from being undulated and the reflected light or scattered light from the surface from reaching the observation part, and to enable accurate surface inspection, it is specified by the first diaphragm. The NA may be configured to be larger or larger than the NA specified by the second diaphragm.

For example, in order to limit the place where the adjustment work is required to only the first diaphragm and to greatly reduce the labor of the adjustment work as compared with the conventional case, the half mirror, the light source, the first diaphragm, and the like. In addition, a housing that fixes the positional relationship between the lenses and holds each of them may be further provided.

As described above, according to the coaxial illumination device according to the present invention, the lens acts as a telecentric lens with respect to the light source and collects the reflected light or the scattered light from the work with respect to the observation unit. It can act as a condenser lens. Therefore, it is not necessary to provide a lens for each of the light source and the observation unit, and it is easy to increase the field of view while reducing the number of parts and reducing the size of the entire device. Further, since the number of lens arrangements can be reduced, the adjustment work for appropriately observing the work can be simplified as compared with the conventional case.

The schematic diagram which shows the surface inspection system and the coaxial lighting apparatus which concerns on 1st Embodiment of this invention. The schematic perspective view which shows the coaxial lighting apparatus which concerns on 1st Embodiment. The schematic sectional perspective view of the coaxial lighting apparatus which concerns on 1st Embodiment. The schematic diagram which shows the mode of irradiating the work with light by the coaxial lighting apparatus which concerns on 1st Embodiment. The schematic diagram which shows an example of the effect by changing NA on the light source side by the coaxial lighting apparatus which concerns on 1st Embodiment. The schematic diagram which shows the surface inspection system and the coaxial lighting apparatus which concerns on 2nd Embodiment of this invention.

200 ・ ・ ・ Surface inspection system 100 ・ ・ ・ Coaxial lighting 1 ・ ・ ・ Half mirror 2 ・ ・ ・ Light source 3 ・ ・ ・ Lens 4 ・ ・ ・ 1st diaphragm 5 ・ ・ ・ 2nd diaphragm 7 ・ ・ ・ Housing

The coaxial lighting device 100 according to the first embodiment of the present invention and the surface inspection system 200 using the coaxial lighting device 100 will be described with reference to FIGS. 1 to 3. The coaxial lighting device 100 of the first embodiment is used for surface inspection or the like, for example, by irradiating a work W which is an object such as a product with light and observing scratches or characters on the surface of the work W with a camera or the like for automatic inspection. It is used. Specifically, as shown in FIG. 1, the coaxial illuminating device 100 is located between the work W and the observation unit M on the observation axis A1 connecting the work W and the observation unit M such as a camera for observing the work W. Is installed. The surface inspection system 200 is composed of the coaxial illumination device 100 and the observation unit M arranged in this way.

The details of the coaxial lighting device 100 will be described below.

As shown in FIGS. 1 to 3, the coaxial illumination device 100 includes a half mirror 1 arranged on the observation axis A1, a light source 2 that irradiates light toward the half mirror 1, a half mirror 1, and a work W. A lens 3 arranged between them, a first aperture 4 arranged between the half mirror 1 and the light source 2, a second aperture 5 arranged between the half mirror 1 and the observation unit M, and a second aperture. It includes an observation side lens 6 arranged between the diaphragm 5 and the observation unit M, and a housing 7 for accommodating these.

The half mirror 1 is a cube half mirror formed in a cubic shape by combining two prisms. A dielectric multilayer film or a metal thin film is coated on the joint surface of each prism, and the joint surface is arranged so as to form 45 degrees with respect to the observation axis A1 and the irradiation axis A2 of the light source 2, respectively.

The light source 2 emits surface light from a rectangular, for example, square light emitting surface, and emits uniform diffused light from the light emitting surface. The light source 2 is formed, for example, by arranging a large number of LED chips on a substrate in an array. In the first embodiment, there is no optical element other than the first diaphragm 4 between the light source 2 and the half mirror 1. Further, the light source 2 is fixed to the housing 7, and the position in the housing 7 is fixed.

The lens 3 is composed of a single lens or a plurality of lenses, and is fixed around the work-side opening 71 of the housing 7. The light emitted from the light source 2 and reflected by the half mirror 1 is refracted by the lens 3 and irradiated perpendicularly to the work W. Further, the light reflected or scattered by the work W is collected by the lens 3 and transmitted through the half mirror 1 and then incident on the observation unit M. In this way, the lens 3 is shared by both the light source 2 and the observation unit M. The lens 3 is arranged so that the focal point of the lens 3 exists between the light source 2 and the half mirror 1 on the irradiation axis A2 and between the half mirror 1 and the observation unit M on the observation axis A1. There is.

The first diaphragm 4 is arranged at the focal point of the lens 3 on the irradiation axis A2. That is, the light source 2, the first diaphragm 4, and the lens 3 form a telecentric optical system, and the light emitted from the light source 2 is parallelized by the lens 3 and irradiated to the work W. The first diaphragm 4 is a variable diaphragm, and is configured so that the opening diameter thereof can be appropriately adjusted by an adjustment knob 41 projecting to the outside of the housing 7. Further, in the coaxial lighting device 100 of the first embodiment, only the first diaphragm 4 is adjustable. The position of the first diaphragm 4 is also fixed in the housing 7.

The second diaphragm 5 is arranged at the focal point of the lens 3 on the observation axis A1. That is, the work W, the lens 3, and the second diaphragm 5 form a telecentric optical system, and of the light reflected or scattered by the work W, only the light having an optical axis in the direction parallel to the observation axis A1 is the second diaphragm. The observation unit M can be reached after passing through 5. In the first embodiment, the second diaphragm 5 is a fixed diaphragm, and its opening diameter is fixed to a predetermined size. Further, the NA defined by the first diaphragm 4 is configured to be larger than the NA defined by the second diaphragm 5.

The observation side lens 6 refracts the light that has passed through the second diaphragm 5 and causes the light to enter the observation unit M. For example, the focal point of the observation side lens 6 may be located on the second diaphragm 5, and the light passing through the observation side lens 6 may be parallelized and incident on the observation unit M.

The housing 7 has a vertical cross section along the observation axis A1 having a substantially horizontal T-shape. The housing 7 is configured so that the separation distance between the half mirror 1 and the lens 3 is longer than the separation distance between the light source 2 and the half mirror 1. Further, the diameter of the observation hole 72, which is the opening on the observation portion M side, is formed smaller than the opening on the work W side.

In the coaxial illumination device 100 of the first embodiment configured in this way, since the lens 3 is provided only in the work-side opening 71 of the housing 7, the number of lenses used can be reduced as compared with the conventional case. can. Therefore, such labor can be significantly reduced as compared with the case where the adjustment work is performed for each of the lenses on the light source side and the observation unit side as in the conventional case.

Further, since the number of parts constituting the coaxial illumination can be reduced, the field of view in the observation unit M can be increased without making the entire device so large.

Further, since the light source 2, the first diaphragm 4, and the lens 3 form a telecentric optical system, the light emitted from the light source 2 can be applied to the work W as parallel light, and the NA (numerical aperture) of the light source 2 is also increased. It can be adjusted with the first aperture 4. Specifically, as shown in FIGS. 4A and 4B, when the NA of the light source 2 is changed by the first diaphragm 4, the range of solid angles at which light can be incident at each point on the surface of the work W. Can be changed uniformly. In the first embodiment, the NA of the observation unit M is fixed by the second aperture 5 which is a fixed aperture. Therefore, by changing the aperture diameter of the first aperture 4, the NA of the light source 2 is higher than the NA of the observation unit M. Can be made large enough.

For example, as shown in FIG. 5A, when the work W inspects a character engraved on a flat surface by machine vision, if there is a region D having a minute undulation on the surface other than the character, FIG. 5B ), The amount of reflected light or scattered light that reaches the observation unit M from the characters as well as the area D is reduced, and the inspection by machine vision may not be performed accurately. This is because the reflected light and the scattered light do not travel in the direction parallel to the observation axis A1 due to the swell, and cannot be incident on the observation unit M. In such a situation, when the NA of the light source 2 is increased as shown in FIGS. 4 (a) to 4 (b), a direction parallel to the observation axis A1 is provided in a part of the light reflected or scattered in the region D of the work W. It is possible to generate a component that progresses to the above and make it incident on the observation unit M. Therefore, as shown in FIG. 5C, a certain amount of reflected light or scattered light can reach the observation unit M even in the wavy region D, and the inspection by machine vision can be performed with high accuracy. ..

Further, in the first embodiment, since the irradiation mode of light to the work W can be adjusted only by the opening diameter of the first diaphragm 4, the irradiation mode such as brightness and brightness suitable for surface inspection can be realized only by a simple adjustment work. It's easy to do.

Next, the coaxial lighting device 100 according to the second embodiment of the present invention will be described with reference to FIG. The members corresponding to the members described in the first embodiment are designated by the same reference numerals.

The coaxial illumination device 100 of the second embodiment is different from the first embodiment in that the second diaphragm 6 which is a variable diaphragm is provided between the half mirror 1 and the observation unit M.

By providing such a second diaphragm 6, it is possible to adjust the amount of light incident on the observation unit M, and it is possible to easily obtain an image suitable for surface inspection.

Other embodiments will be described.

The coaxial lighting device according to the present invention is not only used for surface inspection, but can also be used for other inspections such as visual inspection.

The light source is not limited to the LED, and other types may be used. The lens is not limited to a convex lens, and a Fresnel lens or the like may be used. In addition, the irradiation axes may not be orthogonal to the observation axis but may simply intersect.

In addition, a part of various embodiments may be combined and modified as long as it does not contradict the gist of the present invention.

According to the present invention, it is possible to provide a coaxial lighting device that can be compact but has a wide field of view and can easily perform adjustment work.

Claims (6)

A half mirror diagonally arranged on the observation axis connecting the work to be observed and the observation unit for observing the work,
A light source arranged so that the half mirror is irradiated with light from a direction different from the observation axis and the light reflected by the half mirror is irradiated to the work.
A lens provided between the half mirror and the work
A first diaphragm provided between the light source and the half mirror is provided.
A coaxial illuminating device, wherein the first diaphragm is arranged at the focal point of the lens on an irradiation axis connecting the light source and the half mirror. The coaxial lighting device according to claim 1, wherein only the first diaphragm is provided as an optical element between the light source and the half mirror. The light source has a flat light emitting surface and has a flat light emitting surface.
The coaxial lighting device according to claim 1, wherein the light emitting surface is arranged so that the irradiation axis and the observation axis are orthogonal to each other. The coaxial lighting device according to claim 1, wherein a second diaphragm is further provided between the half mirror and the observation unit. The coaxial lighting device according to claim 4, wherein the NA defined by the first diaphragm is larger than or can be made larger than the NA defined by the second diaphragm. The coaxial lighting device according to claim 1, further comprising a housing that fixes and holds the positional relationship between the half mirror, the light source, the first diaphragm, and the lens.

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