JPH07107578B2 - Optical device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an optical device, for example, a visual inspection device for a printed circuit board or the like, a microscope, or the like.

[Conventional technology]

Conventionally, a method of projecting a specific pattern on an object to be detected and detecting a specific shape has been used in an automatic visual inspection apparatus, but in this case, it is necessary to darken the surroundings in order to detect the specific pattern image. There is a drawback that the property is significantly reduced. Further, there has been a bright field illumination method using a microscope or the like, and a technique for illuminating only a detection surface has been established. An appearance foreign matter inspection device for a semiconductor wafer or the like is known, for example, from Japanese Patent Publication No. 59-48540.

[Problems to be Solved by the Invention]

An object of the present invention is to provide an illuminating optical device that is suitable for brightly illuminating a surrounding work surface while detecting a specific portion and improving a work environment.

[Means for solving problems]

In the illumination device according to the embodiment of the present invention, a specific shape (pattern) light-shielding plate is arranged on the focal plane of the projection lens in the illumination optical system, and this shape is projected onto the illuminated surface to perform specific partial illumination. A horizontal polarizing plate is arranged for external general illumination to illuminate with horizontal polarized light and a vertical polarizing plate is arranged for the image detection optical system to remove external horizontal polarized illumination light (in this case,
Horizontally polarized light means polarized light with a 90 ° phase difference from each other), and by combining these two, the external surrounding work surface is illuminated brightly, and at the same time only a specific shape is illuminated and detected. .

[Action]

According to the above configuration, the specific portion of the object such as the inspection object or the observation object is illuminated by the light shielding plate (illumination mask) having the specific shape. Therefore, it is possible to observe an image of the target object in a specific range with an eyepiece lens against a dark field background, or to display it on a monitor television or the like using a video camera. On the other hand, when scanning an object vertically and horizontally, the illumination light that brightens a work surface or a wide range of the object is an optical system that does not reach the eyepiece lens or the imaging device. The object surface can be illuminated over a wide range. Thus, the present invention was able to satisfy the contradictory requirements of dark field and wide range illumination.

〔Example〕

 Details of the present invention will be described below with reference to the drawings.

FIG. 1 shows an overall configuration diagram of a specific shape detection illumination device to which the present invention is applied.

Although a bright field illumination device is used for the specific shape projection illumination here, this illumination system may be separately provided. The light beam emitted from the bright-field illumination light source 1 is refracted by 90 ° by the 45 ° half mirror 2 inside the lens barrel, sent to the illuminated surface 4 by the lens 3, returns through the same optical path, and passes through the lens 3 again. Passes through the 45 ° half mirror 2 and forms an image on the image pickup device 5. In this case, the image pickup device 5 may be an eyepiece for visual inspection. In this illumination system, the focal plane of the lens 3 is at the 45 ° half mirror 2 in addition to the plane of the imaging device 5.
It also exists on the optical path that is refracted by 90 °. Now, when the light shielding plate 6 having a specific shape is arranged on the focal plane on this optical path, this specific shape is imaged (projected) on the illuminated surface 4, and as a result, only the specific shape portion is illuminated.

In addition to the above illumination device, the light flux from the external illumination light source 7 passes through the horizontal polarizing plate 8 to illuminate the illuminated surface 4 as horizontal polarized light, and the reflected light does not reach the imaging device 5 on the imaging optical path. Vertically polarized light (with 90 ° phase difference from horizontal polarized light)
Place a board so that it can block light.

When such an illuminating device is used, the imaged (imaged) result can detect only the specific shape portion as shown in FIG. 2 (a), and the illuminated surface is shown in FIG. 2 (b). Uniform uniform illumination can be obtained as shown. For this reason, it is possible to perform the specific shape detection without darkening the surroundings in the specific shape illumination such as the local window or the slit light illumination, so that the workability is improved and the peripheral image is detected by using another optical device, and another image is detected. There is an advantage that it can be processed as information.

Hereinafter, two application examples of the device of the present invention will be described with reference to FIGS. 3 and 4.

FIG. 3 shows an application example in which a transmission type liquid crystal device is used and the pattern of the light shielding plate of a specific shape is variable.

In FIG. 3, the light source 11 and the half mirror 14 are the bright field illumination light source 1 and the 45 ° half mirror 12 in FIG. 1, respectively.
In addition, the transmission type liquid crystal 13 is arranged at the position of the specific shape light shielding plate 6 in FIG. 1 as an alternative thereto. Here, the light flux sent from the light source 11 passes through the transmissive liquid crystal 12 and is irradiated by the half mirror 14 onto the illuminated surface. Liquid crystal lighting device now
If the lighting pattern of the transmissive liquid crystal 12 is controlled by 13, the light-shielding shape changes, and the specific shape illumination pattern can be changed.

In this case, since the light flux that has passed through the transmissive liquid crystal is itself polarized, the polarizing plate used for external illumination has a phase difference of 90 ° from this liquid crystal transmission light flux.

FIG. 4 shows an example in which a light flux having a complementary color relationship is used instead of the 90 ° polarized light of the present invention. In this example, since the surface to be illuminated is illuminated with complementary light, the workability in ambient illumination is reduced, but the image itself can be obtained with high contrast. FIG. 4 shows an illumination method in which the selective reflection of the background color is taken into consideration.

In FIG. 4, the reflection surface 21, the low wavelength cut filter 23 and the long wavelength cut filter 25 are arranged at the positions of the illuminated surface 4, the horizontal polarization plate 8 and the vertical polarization plate 9 of FIG. 1, respectively. The reflecting surface 21 is colored to some extent, and its surface has a characteristic such as a reflecting surface selective reflection characteristic 22 (wavelength-reflectance characteristic). If illumination and image detection are performed with wavelength components having a complementary color relationship with the selective reflection light, the lightness will drop on the reflecting surface 21 and high contrast will be obtained when foreign matter having other selective reflection characteristics is present on this surface. The image can be detected. In this example, the low-wavelength cut filter 23 illuminates the surroundings with a light flux having a low-wavelength cut filter characteristic 24 (wavelength-transmittance characteristic), and the long-wavelength cut filter 25 is arranged in the image inspection optical system. The image is detected at 26 (wavelength-transmittance characteristic). Here, the bright field illumination system is arranged as in FIG. 1, and the relationship of complementary colors is not limited to this.

FIG. 5 shows the principle of background color for realizing FIG. Selective transmission filter for the light flux condensed using the lens 31
An image is formed through 32 (this filter may be used in front of the lens 31. Here, the selective reflection characteristic of the background 34 is shown in FIG. 5 (d) (wavelength-reflectance characteristic), and the selective reflection characteristic of the foreign matter 33 is shown in FIG. Assuming that (c) (wavelength-reflectance characteristic), the selective transmission characteristic of the selective transmission filter 32 is shown in FIG.
With the reflectance characteristic), the foreign matter 33 can be detected with high contrast.

〔The invention's effect〕

According to the present invention, since the surrounding work surface can be kept at high brightness while performing the specific shape illumination, it is possible to improve workability and safety.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of a lighting device using the present invention,
FIG. 2 is a diagram showing an illumination effect by the device of FIG. 1, FIG. 3 is a diagram showing an application example using a transmission type liquid crystal in the present invention, and FIG.
FIG. 5 is a diagram showing another embodiment of the present invention using a light flux having a complementary color relationship instead of 90 ° polarized light, and FIG. 5 is a diagram showing the principle of background color according to the present invention. 1 …… Brightfield illumination light source, 2 …… 45 ° half mirror, 3
...... Lens, 4 ...... Illuminated object (inspected object), 5 ... Imaging device, 6 ... Illumination mask, 7 ... Illumination device, 8 ... Horizontal polarizing plate, 9 ... Vertical polarizing plate.

Claims (1)

[Claims] 1. A first illumination system for illuminating an object in a specific shape range, a second illumination system for illuminating the object via a first polarizing plate, and the first polarizing plate. Is a projection system for projecting the object through a second polarizing plate whose polarization axes are offset from each other.