JPH0372248A - Dust detector - Google Patents

Abstract

PURPOSE:To enable detection of dust alone on the surface side of a light transmitting surface to be inspected by defining an angle between a scanning light incident into a surface to be inspected and reflected light thereof at a specified value to set an angle of incidence of the scanning light within a specified range. CONSTITUTION:A projection optical system 7 of a dust detector 1 is made up of a laser oscillator 4, a galvanomirror 5 and a ftheta lens 6 and a scanning light A is made to irradiate a surface 2a to be inspected of a window glass 2 to form an image of the reflected light B on a slit plate 9 through a condenser lens 8. Then, light transmitted through the slit 9a is converted into an electric signal with an optoelectrical transducer 10 and a mirror 5 is driven to rotate and inclines the scanning light A in a direction of the arrow C. Here, an angle between the scanning light A and the reflected light B is set at about 90 deg. and an angle of incidence of the scanning light A is set at about 20 deg.-40 deg. or about 50 deg.-60 deg. to the surface 2a to be inspected. Thus, scattered light is separated accurately thereby enabling detection of dust adhering to the surface of the surface 2a to be inspected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose of the Invention (Industrial Application Field) The present invention relates to a dust detection device whose object to be inspected is, for example, a window glass adhered to a package of a CCD solid-state image sensor.

(Prior art) A window glass provided in the imaging section of a CCD solid-state imaging device is
If the CCD is bonded to the side surface with dust attached to it, a clear image cannot be obtained, and the CCD itself becomes a defective product and must be discarded.

Therefore, before bonding the window glass of the CCD, it is necessary to inspect whether dust has adhered to the window glass.

To detect such dust, many surface inspection devices that scan the surface to be inspected with a scanning beam have been put into practical use.

However, such a surface inspection device cannot be used to detect dust on COD window glass mainly for the following two reasons.

First, an adhesive (sealing material) is provided along the periphery of the bonded surface of the window glass, and when light hits this adhesive, strong scattered light is generated, making it difficult to accurately detect dust. becomes impossible. This is because it is necessary to perform dust detection immediately before adhering the window glass, so inspection with the adhesive in place cannot be avoided.

Second, although it is necessary to detect only the dust attached to the side of the window glass where the adhesive is applied, the dust that has passed through the window glass and attached to the opposite side is also detected.
Efficient testing was not possible.

For these reasons, a dust detection device for detecting dust attached to a window glass used in a fixed CCD image sensor has not been put into practical use.

(Problem 8 to be Solved by the Invention) Generally used surface inspection devices inspect the surface of a material that transmits light, and the back surface is also included in the inspection target. Therefore, it is impossible to detect only the dust attached to one side, and the dust on the back side is also detected. Additionally, if there is a convex part on the surface to be inspected, this will easily cause scattered light, making it impossible to perform accurate inspection. Furthermore, if a convex portion is formed around the surface to be inspected using an adhesive, detection of dust becomes almost impossible, making it impossible to put it to practical use.

The present invention has been made with attention to the above-mentioned problems, and it is possible to inspect only one side of a light-transmitting object to be inspected, and even if there is a convex part on the surface to be inspected, this convex part can be inspected. It is an object of the present invention to provide a dust detection device that can accurately detect dust while minimizing the influence on inspection.

[Structure of the Invention] (Means for Solving the Problems) A light source is provided, and a projection optical system is provided that irradiates a surface to be inspected with a scanning beam from the light source, so that only the scanning beam reflected by the surface to be inspected is transmitted. A photoelectric conversion element is provided to convert the light transmitted through the slit into an electrical signal, and the angle between the scanning light beam incident on the surface to be inspected and the scanning light beam reflected on the surface to be inspected is approximately 90''. The angle of incidence of the scanning light beam that enters the surface to be inspected is determined from the maximum value of the angle at which the scanning beam is diffusely reflected on the convex portion of the surface to be inspected near the horizontal to the angle at which the light reflected from the surface to be inspected re-enters the light source near the vertical. The dust detection device is set to an angular range that includes a minimum angle of 45° from the surface to be inspected and excludes the angular range in which the light emitted from the light source directly enters the photoelectric conversion element.

(Function) When the included angle between the scanning light beam incident on the surface to be inspected and the scanning light beam reflected on the surface to be inspected is approximately 90#, the angle of incidence of the scanning light beam on the surface to be inspected is defined as the surface to be inspected. By setting the value to a value exceeding the maximum angle of diffuse reflection on the convex portion, it is possible to prevent the scanning beam from being diffusely reflected on the convex portion. In addition, by making the angle smaller than the minimum angle at which the scanning light beam incident from the direction almost perpendicular to the surface to be inspected is reflected by the surface to be inspected and re-enters the light source,
It is possible to prevent reflected light from the surface to be inspected from entering the light source. Furthermore, by setting the angle range to include a position 45° from the surface to be inspected and exclude the angle at which light from the light source directly enters the photoelectric conversion element, direct light from the light source can be prevented from entering the photoelectric conversion element.

(Embodiment) An embodiment of the present invention will be described with reference to FIGS. 1 to 10. The dust detection device 1 shown in the figure is, for example, C
This detects dust attached to the surface of the window glass 2 that is bonded facing the imaging section of the CD solid-state image sensor.

This window glass 2 is formed, for example, in the shape of a rectangular plate, and an adhesive 3 is adhered in a convex shape along the peripheral edge of the surface on the joining side. This window glass 2 is oriented upward with the surface to be inspected 2a on the bonding side, for example, X-Y
The table is placed on top.

The dust detection device 1 includes a laser oscillation device 4 as a light source. This laser oscillation device 4 is configured to output laser light in a predetermined direction by a support device (not shown). A galvanometer mirror 5 is disposed on the optical path of the laser beam output from the laser oscillation device 4, so that the laser beam is reflected at a predetermined angle. Also, on the optical path of the laser beam reflected by this galvano mirror 5, f
A θ lens 6 is inserted, thereby setting a predetermined focal length. Here, the laser oscillation device 4
, a galvano mirror 5, and an fθ lens 6 form a projection optical system 7.

The laser beam that has passed through the fθ lens 6 is reflected at a predetermined angle on the inspection surface 2a of the window glass 2 as a scanning beam. A condenser lens 8, a pick-pocket plate 9, and a photomultiplier 10 are sequentially arranged on the optical path of the laser beam reflected by the surface to be inspected 2a. Here, the photomultiplier 10 is a photoelectric conversion element.

The angle between the scanning beams A and B passing through the fθ lens 6 and the condensing lens 8 is set to about 90''.

Further, as shown in FIG. 10, the slit plate 9 includes scattered light 11a1 from dust on the surface to be inspected 2a, scattered light 11b1 from the adhesive 3, and dust attached to the back surface of the surface to be inspected 2a. The scattered light 11C is imaged. The slits 9a formed through the slit plate 9 are formed corresponding to the coupling positions of the scattered light 11H from the dust attached to the surface to be inspected 2a. here,
The longitudinal direction of the slit 9a is formed so as to correspond to the direction in which the light from the laser oscillation device 4 oscillates, by a galvanometer scanner 5a that supports the galvanometer mirror 5 in a rotationally driven state. In other words, galvano mirror 5
The scanning light beam A is swung in the direction of arrow C in the figure, and the width of the test sleeve 2a is set within this swiveling range. If dust is attached to the surface to be inspected 2a, scattered light 11a is emitted and the slit plate 9
The image is formed within the slit 9a.

As described above, measurement is performed one-dimensionally by swinging the galvanomirror 5, and when this -dimensional direction All] determination is completed, the measurements are sequentially orthogonal to the -dimensional direction C (swinging direction of the galvanomirror 5). In this direction, the X-Y table t is moved by a dimension smaller than the spot diameter of the scanning light beam A. Through this inspection process, δll] is determined over almost the entire area of the window glass 2.

When detecting dust with the above-described configuration, according to past experiments, it was not possible to accurately detect dust in the angular range described below.

Hereinafter, the scanning light beam A has an angle of about 900.

At B, it is reflected by the galvano mirror 5 and is reflected by the fθ lens 6.
The influence of the angle at which the scanning light beam A transmitted through the inspection target surface 2a is incident on the inspection target surface 2a on dust detection will be explained.

In addition, in order to make it clear that the scanning beam A from the laser oscillation device 4 and the scanning beam B incident on the photomultiplier 10 are shown, the galvano mirror 5 and the fθ lens 6 are not shown in the figure, and the laser beam is directly transmitted. The scanning light beam A from the oscillator 4 is shown to be incident on the surface to be inspected 2a, and the reflected scanning light beam B is shown to be directly incident on the photomultiplier 10. When actually measuring the non-inspection surface 2a, it is necessary to provide a galvanometer mirror 5, an fθ lens 6, a condensing lens 8, and the like.

First, as shown in FIG. 5, when the scanning light beam A is incident on the surface to be inspected 2a at an angle of approximately 90°, the scanning light beam A output from the laser oscillation device 4 is After being reflected by the surface 2a, it directly enters the laser oscillation device 4, making the oscillation state of the laser oscillation device 4 unstable.
This made it impossible to accurately detect dust.

Furthermore, in this state, as shown in FIG. 7, since the included angle between the scanning beam A and the scanning beam B is approximately 90°, the scanning beam B reflected on the surface to be inspected 2a is reflected on the surface to be inspected 2a.
The scanning light beam B did not reach the photomultiplier 10 because it was blocked by the convex adhesive 3 provided on the edge of the photomultiplier 10. This property was a phenomenon that occurred in an angular range close to 90''.

Furthermore, when the scanning beam A outputted from the laser oscillation device 4 is incident at an angle of approximately 45° as shown in FIG. A part of the light is directly incident on the photomultiplier 10, which also has the drawback that accurate measurement cannot be performed. This property is a phenomenon that occurs in an angle range around 45° including 45°.

Further, when the scanning light beam A output from the laser oscillation device 4 is irradiated from the surface to be inspected 2a at an angle close to 0° or close to the convex portion formed by the adhesive material 3, the scanning light beam A It is blocked or scattered by the convex portions of the material 3, making accurate measurement impossible.

Here, when adding the condition that the surface 2a to be inspected is translucent, when the incident angle of the scanning light beam A is small, as shown in FIG. 9, the scattered light 11 scattered by the dust on the surface
Between a and the scattered light 11c scattered by the dust on the back side,
A predetermined distance d results. Furthermore, when the incident angle of the scanning beam A is increased, the distance d between the scattered light 11a scattered by the dust on the front surface and the scattered light 11c scattered by the dust on the back surface is as shown in FIG. This is smaller than in the case described above.

According to these properties, it can be seen that the smaller the incident angle of the scanning light beam A is, the more reliable the separation of images by the slit 9a becomes, and the more accurately detecting only the dust on the surface.

Based on the properties described above, the incident angle of the scanning light beam A in this embodiment is set as shown below. Note that at this time, the angle between the scanning light beam A incident on the surface to be inspected 2a and the reflected scanning light beam B is limited to about 90'.

The specific range of the incident angle of this scanning beam A is
about 20″ to about 40° or about 50″ to about 6° relative to a
It is set to 0'.

This means that the opening angle of the scanning light beam A from the surface to be inspected 2a is approximately 2.
For angles smaller than 0'', adhesive 3 is used as described above.
This is because the scattered light 11b generated by the incident light makes accurate measurement impossible, and it is necessary for the light to be incident at an angle greater than about 20°.

In addition, a part of the scanning beam A that is output from the laser oscillation device 4 is reflected by the surface to be inspected 2a, which is incident at an angle range of about 50 degrees to about 60 degrees including 45 degrees from the surface to be inspected. The light directly enters the photomultiplier 10 without being detected, making accurate measurement impossible. Therefore, it is necessary to make the scanning light beam A incident at an angle deviating from the angle of about 50'' to about 60''.

Furthermore, if the scanning beam A is incident at an opening angle of about 90 degrees from the surface to be inspected 2a, the scanning beam B reflected by the surface to be inspected 2a will enter the laser oscillation device 4 again.
This made the laser output of the laser oscillation device 4 unstable. Therefore, it is necessary to avoid the angle of about 60' to about 90' and make the scanning light beam A incident from another angle.

For the reason mentioned above, if the angle between the scanning beam A and the scanning beam B is limited to 90°, the surface to be inspected 2 of the scanning beam A is
The suitable range of angle of incidence on a is limited to about 20° to about 40″ or about 50′ to about 60°.

Since the surface 2a to be inspected is the window glass 2 which is transparent, it is necessary to avoid detecting dust on the back surface side. Therefore, by reducing the angle of incidence of the scanning light beam A on the surface to be inspected 2a, more accurate separation of scattered light can be achieved. For this reason, the optimum angle of incidence is in the range of about 20'' to about 40°.

If dust is detected under these conditions, each scattered light beam can be accurately separated as shown in FIG. 10, and dust attached to the surface of the surface to be inspected 2a of the window glass 2 can be detected.

Here, the above-mentioned approximately 20° is the maximum angle at which diffused reflection occurs on the adhesive 3 of the surface to be inspected 2a. Also, about 40° to about 5
0@ is an angular range that includes 45° and in which a portion of the scanning light beam A output from the laser oscillation device 4 directly enters the photomultiplier 10.

Furthermore, the above-mentioned approximately 60° is the minimum value of the angle at which the scanning beam A that is incident at an angle close to perpendicular is reflected and the reflected scanning beam B is incident on the laser oscillation device 4 again.

Window glass 2 inserted into the CCD (solid-state image sensor)
If dust adheres to the insertion side surface 2a, it will not be possible to obtain a clear image and the product will be defective. Even if dust adheres to the surface facing outward after insertion, it will not have a negative effect on quality.

It is possible to provide an optimal dust detection device for detecting dust attached only to one surface of such a light-transmitting plate member.

Further, since it is extremely necessary to detect dust immediately before inserting the window glass 2 into the COD, the adhesive material 3 is already provided on the surface to be inspected 2a.

When performing an inspection in this manner, a convex adhesive material 3 is provided around the surface to be inspected 2a. Since measurements can be made while avoiding these obstacles, dust can be detected accurately.

As a result, dust can be accurately and efficiently detected immediately before the CCD window glass 2 is mounted, and dust can be detected on only one side, which was previously impossible.

Note that the present invention is not limited to the above embodiment. For example, in the above embodiment, the surface to be inspected is the window glass 2 that is inserted into the imaging surface of the COD, but it is not limited to this, but it is a plate member having a translucent property and having a convex portion formed on the side surface to be measured. If,
Applicable.

[Effects of the invention] The included angle between the scanning light beam incident on the surface to be inspected and the scanning light beam reflected by the surface to be inspected is approximately 90 degrees, and the scanning light beam incident on the surface to be inspected is Within the angular range between the maximum angle at which the opening angle with the surface to be inspected is diffusely reflected by the convex portion formed on the surface to be inspected, and the minimum angle at which the scanning beam is reflected to the light source when the opening angle with the surface to be inspected is close to perpendicular. By making the scanning beam from the light source enter the photoelectric conversion element in an angular range that includes 45° and excludes the angular range in which it directly enters the photoelectric conversion element, diffuse reflection is prevented, the light source is stabilized, and detection performance is stabilized. can be done. Furthermore, with the scanning light beam incident within the above angle range, even if the surface to be inspected is translucent, only dust on the surface side can be detected.

[Brief explanation of drawings]

FIG. 1 to FIG. 10 are one embodiment of the present invention,
Fig. 1 is a perspective view of the dust detection device, Fig. 2 is a perspective view showing the window glass and its detection surface, Fig. 3 is a sectional view of the section marked ■-■ in Fig. 2, and Fig. 4 is the positive angle. FIG. 10 is a front view showing each scattered light imaged on the slit plate. DESCRIPTION OF SYMBOLS 1... Dust detection device, 3... Adhesive material, 4... Laser oscillation device (light source), 2a... Surface to be inspected, 7... Acoustic optical system, 9a... Slit, 10 ...Photomultiplier (photoelectric conversion element), A...Scanning light beam incident on the surface to be inspected, B...Scanning light beam reflected on the surface to be inspected.

Claims (1)

[Claims] a light source, a light projecting optical system that causes a scanning beam from the light source to scan a surface to be inspected having a convex portion around the surface, and a scanning beam reflected by the surface to be inspected at an image formation position of the scanning beam reflected by the surface to be inspected. A dust detection device includes a slit arranged at the imaging position of the light beam so that only the scanning light beam reflected from the surface to be inspected passes through, and a photoelectric conversion element that converts the light passing through the slit into an electrical signal. The included angle between the scanning light beam incident on the surface to be inspected and the scanning light beam reflected on the surface to be inspected is approximately 90
゜, and the incident angle of the scanning light beam that enters the surface to be inspected is the maximum value of the angle at which the scanning beam is diffusely reflected by the convex portion of the surface to be inspected near the horizontal, and the light reflected from the surface to be inspected near the vertical enters the light source. and within an angular range that includes an angle of 45° from the surface to be inspected and excludes the angular range in which the light emitted by the light source directly enters the photoelectric conversion element. dust detection device.