JP2509019B2 - Interference fringe inspection device and interference fringe on / off method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interference fringe inspection device and an interference fringe on / off method.

[0002]

2. Description of the Related Art In a product inspection or the like, when an inspection surface of an inspection object is a curved surface, the inspection surface can be inspected by an image of the inspection surface and an interference fringe pattern corresponding to the inspection surface. Has been done.

FIG. 3 schematically shows a conventional interference fringe microscope for inspection as an example of an "interference fringe inspection device" for performing such inspection. In this example, the object to be inspected 0 is a magnetic head, and the contact portion with the magnetic tape is the surface to be inspected 0A. The surface to be inspected 0A is a cylindrical curved surface, and a gap 01 for magnetic detection is formed on the top thereof.

When monochromatic light is emitted from the illumination light source device 10, the light is reflected by the semi-transparent mirror 12, and the objective lens 14
The surface to be inspected 0A of the magnetic head 0 is irradiated through the transparent parallel plate 16 and the transparent flat plate 16. The parallel plate 16 is fixedly provided at a fixed position in the device space, and the magnetic head 0 has a surface 0 to be inspected.
A is a surface 16 of the parallel plate 16 opposite to the objective lens 14.
It is in contact with A. A surface 16A of the parallel plate 16 that comes into contact with the surface to be inspected 0A is called a "reference surface".

A part of the light emitted to the surface 0A to be inspected is reflected by the surface 0A to be inspected, and a part thereof is reflected by the reference surface 16A. These reflected lights are transmitted through the parallel plate 16 and are re-incident on the objective lens 14, are transmitted through the semi-transparent mirror 12, and are reflected by the CCD.
It is incident on the light receiving surface of the camera 18. The light receiving surface of the CCD camera 18 and the reference surface 16A are the same as the objective lens 14 and the parallel plate 1.
6 has an optical conjugate relationship with each other, and the surface to be inspected 0A is in contact with the reference surface 16A.
An enlarged image of the surface 0A to be inspected is formed on the light receiving surface of the camera 18. Therefore, the reference surface 16A has a function of focusing the surface to be inspected 0A on the one hand.

Light reflected by the surface to be inspected 0A and the reference surface 16A
The light reflected by the light beams interferes with each other and forms an interference fringe pattern on the light receiving surface of the CCD camera 18. Therefore, when the output of the CCD camera 18 is displayed on the display 20, the state of the surface to be inspected 0A and the interference fringe pattern can be observed at the same time.

Since the interference fringe pattern is determined by the optical path length difference between the reference surface 16A and the surface to be inspected 01, the surface 0A to be inspected has an "appropriate shape" by looking at the interference fringe pattern. It is possible to detect whether the surface to be inspected 0A maintains the "correct posture" or the like. Further, the presence or absence of "dirt" or "scratch" on the surface 0A to be inspected can be known depending on the image of the surface 0A to be inspected. You can know whether or not you are in the "correct position" above.

In this way, the interference fringe pattern and the image of the surface to be inspected can be observed at the same time, and many things can be known about the object to be inspected 0. When observing the presence or absence in detail, it may be easier to observe if there is no interference fringe pattern. In the interference fringe inspection device, the interference fringe pattern should be generated / erased (interference fringe on / off) as necessary. Has become.

The interference fringes are turned on and off conventionally by a mechanical method, for example, "the position of the work is moved after the distance between the objective lens and the CCD camera is deviated from the standard distance". However, there is a problem that the operation is complicated, or the structure of the inspection apparatus itself is complicated to enable such operation.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and is a novel interference fringe that can be turned on / off without mechanical operation. An object is to provide an inspection device and an interference fringe on / off method.

[0011]

According to the interference fringe inspection apparatus of the present invention, an objective lens is attached to a reference surface of a transparent parallel flat plate whose one surface is a reference surface while the inspection surface of the inspection object is in contact with the reference surface. This is a device that irradiates illumination light through a parallel flat plate and inspects an object to be inspected with an image of the surface to be inspected and an interference fringe pattern formed by reflected light from each of the surface to be inspected and the reference surface.

In the "interference fringe inspection device" of claim 1, the illumination light source device includes the first and second light sources, and has a reflection / transmission film on the reference surface of the parallel plate. Of the two light sources of the illumination light source device, at least the second light source can blink independently of the first light source, and the first light source has a wavelength of λ.
It is intended to emit light "that includes a _first and second light source" Wavelength: in which emits light containing lambda ₂ ". Reflection above
The transmissive film substantially transmits the light from the first light source,
The spectral reflectance characteristic is determined so that the light from the second light source is reflected with a predetermined reflectance. The second light source is a light source for generating an interference fringe pattern. "Predetermined reflectance" of the reflective / transmissive film with respect to the light from the second light source
Is set according to the reflectance of the surface to be inspected, depending on how the contrast of the interference fringe pattern to be generated is set. In order to generate it, the "predetermined reflectance" is preferably 30 to 40% (claim 2).

A third aspect of the present invention is a method for "turning on / off interference fringes" in the interference fringe inspection apparatus according to the first or second aspect, wherein "interference fringes are turned on / off by turning on / off the second light source." The pattern is generated / erased ”.

[0014]

FIG. 2 shows a characteristic portion of an "inspection interference fringe microscope" as an example of the interference fringe inspection apparatus of the present invention in relation to the inspection of the magnetic head 0 described with reference to FIG. There is.
Therefore, the same reference numerals as in FIG. 3 are used. Figure 2
As shown in (a), a reflective / transmissive film 16B is formed on the reference surface 16A of the parallel plate 16. In FIG. 2B, the enlarged view of the portion surrounded by the broken line in this figure is an explanatory diagram. Since the reflection / transmission film 16B substantially transmits the light emitted from the first light source as described above, the interference fringe pattern is not substantially generated by the light emitted from the first light source.

Considering how the light from the second light source behaves, as shown in the figure, the light L from the second light source is
_{When 00} is incident on the reference surface 16A, part of it is reflected as reflected light L ₀₁ , part of it is transmitted as transmitted light L ₁₀ , and the surface to be inspected 0
A is incident on A. The reflected light L _{11 from the} surface 0A to be inspected is partially reflected as reflected light L ₁₃ by the reflection / transmission film 16B and partially transmitted as transmitted light L ₁₂ . Assuming that the reflection / transmission film 16B for the light from the second light source and the amplitude reflection coefficient of the surface to be inspected 0A are r ₁ and r ₂ , respectively, the reflected light is
Each relative intensity of transmitted light, reflected light L _01: r _1, the transmitted light L _{10: 1-r} 1, the reflected light _{L 11: (1-r 1} ) r 2, the transmitted light L _{12: (1-r} 1 ) ² r ₂ , reflected light L ₁₃ : (1-r ₁ ) r
It becomes ₁ r ₂ . The condition for forming a high-contrast interference fringe pattern is that the intensity of the reflected light L _{01 and} the intensity of the transmitted light L ₁₂ are substantially equal, that is, the relationship: r ₁ ≈ (1-r ₁ ) ² r ₂ ( 1) is established. Therefore, the amplitude reflection coefficient of the inspected surface 0A: if r ₂ is determined, accordingly, be determined r ₁ satisfying formula (1), it is possible to generate the most contrast good fringe pattern.

In particular, when the reflectance of the surface 0A to be inspected is extremely high and r ₂ ≈1, the above equation (1) is
r ₁ ² −3r ₁ + 1≈0, and r ₁ satisfying this is about 0.36. Therefore, the reflectance of the reflective / transmissive film 16B is 3
By setting it to 0 to 40%, an interference fringe pattern with high contrast can be generated.

[0017]

EXAMPLES Specific examples will be described below.

FIG. 1A shows an embodiment in which the present invention is applied to the interference fringe microscope for inspection described with reference to FIG. When it comes to things that don't seem to be confused,
The same reference numerals as in FIG. 3 are used. Explaining the characteristic part, the illumination light source device 100 includes the first light source 1
0A and the second light source 10B are combined. These first and second light sources 10A and 10B are LEDs in this embodiment, and the first light source 10A is
As shown in FIG. 1B, light L ₁ (for example, blue light) having a Gaussian spectral intensity distribution including wavelength: λ ₁ is emitted, and the second light source 10B includes wavelength: λ ₂ . Light L ₂ (for example, red light) having a Gaussian spectral intensity distribution is emitted.

In FIG. 1, reference numeral 160 indicates an interference fringe generator including a transparent parallel plate 161. Interference fringe generator 1
Reference numeral 60 denotes a transparent parallel plate 16 as shown in FIG.
A reflection / transmission film 161B is formed on a reference surface 161A of No. 1 (a glass plate in this embodiment), and a reinforcing member 162 is integrated on a surface opposite to the reference surface 161A.

When the parallel plate 161 is optically thick, the surface image to be inspected by the objective lens 14 is deteriorated by the spherical aberration generated by the parallel plate 161. To avoid this, in this embodiment, the thickness of the parallel plate 161 is large. In order to prevent the bending of the parallel plate 161 (which adversely affects the inspection accuracy due to the interference fringe pattern) due to the contact force of the inspection object 0, the reinforcement is made as thin as possible. The members are integrated.

The reflection / transmission film 161B formed on the reference surface 161A of the parallel plate 161 has a spectral reflectance characteristic: R (λ) as shown in FIG. 1 (b). Due to this characteristic,
The light L ₁ from the first light source 10A reflects the reflection / transmission film 161.
Light L that is substantially transmitted through B and is emitted from the second light source 10B
_In No. ₂ , about 35% of it is reflected.

When performing the inspection, as shown in FIG. 1 (a), the inspected surface 0A of the inspected object 0 is brought into contact with the reference surface, and the first and second light sources 10A of the illumination light source device 100, 10B
Lights together. If the output of the CCD camera 18 is displayed on the display 20, the image of the surface to be inspected 0A (by the light L ₁ of the first light source 10A) and the interference fringe pattern based on the surface to be inspected 0A (of the second light source 10B). And (due to light L ₂ ) can be observed simultaneously.

In this state, if the second light source 10B is turned off, the interference fringes can be turned off and only the image of the surface 0A to be inspected can be observed. On the contrary, if the first light source 10A is turned off while the second light source 10B is turned on, only the interference fringe pattern can be observed.

In the above embodiment, the case where the contrast of the interference fringe pattern can be increased has been described, but the contrast of the interference fringe pattern does not necessarily have to be set to be so high. This is because even if the contrast of the interference fringe pattern is low, the contrast can be corrected by image processing. For example, by calculating the "difference" between the image in which the interference fringe pattern is generated and the image in which the interference fringe is turned off, the interference fringe pattern can be obtained, and if necessary, this can be amplified to obtain the desired interference fringe pattern. This is because an interference fringe pattern having contrast can be displayed.

[0025]

As described above, according to the present invention, a novel interference fringe inspection apparatus and interference fringe on / off method can be provided.
Since the present invention has the above-mentioned configuration, it is possible to easily and surely turn on / off the interference fringe without requiring a mechanically complicated structure.

In the embodiment, the case where the image of the surface to be inspected and the interference fringe pattern are displayed on the display through the CCD camera has been described.
Needless to say, the optical system may be configured to be visually observable, and the optical system may be configured to perform both visual observation and display display.

As an interference fringe inspection device, generally,
The imaging magnification of the surface to be inspected does not necessarily have to be the magnification. Therefore, the embodiment apparatus is not limited to the microscope. When a CCD camera is used, the image of the surface to be inspected may be an equal-magnification or reduced image, which may be enlarged by image processing and displayed on the display.

[Brief description of drawings]

FIG. 1 is a diagram for explaining one embodiment of the present invention.

FIG. 2 is a diagram for explaining the operation of the present invention.

FIG. 3 is a diagram for explaining a conventional technique and its problems.

[Explanation of symbols]

 0A Surface to be inspected 100 Light source device for illumination 10A First light source 10B Second light source 12 Semi-transparent mirror 14 Objective lens 161 Transparent parallel plate 161A Reference surface 161B Reflective / transmissive film 18 CCD camera

Claims (3)

(57) [Claims] 1. An illuminating light is irradiated through an objective lens and the parallel plate in a state where the surface to be inspected of an object to be inspected is in contact with the reference surface of a transparent parallel plate having one surface as a reference surface. An inspection device for inspecting an inspection object by an interference fringe pattern formed by reflected light from each of the inspection surface and the reference surface, and an image of the inspection surface, wherein the illumination light source device includes first and second At least a second of the two light sources of the illumination light source device including two light sources, having a reflective / transmissive film on the reference surface of the parallel plate.
Light source can be blinked independently of the first light source, the first light source emitting light having a wavelength: λ ₁ and the second light source emitting light having a wavelength: λ _2. Yes, the reflection / transmission film has spectral reflectance characteristics determined so that the light from the first light source is substantially transmitted and the light from the second light source is reflected at a predetermined reflectance. The interference fringe inspection device is characterized in that 2. The interference fringe inspection apparatus according to claim 1, wherein the reflectance of the reflective / transmissive film with respect to the light from the second light source is 30 to 40%. 3. The interference fringe on / off method according to claim 1 or 2, wherein the interference fringe pattern is generated / erased by turning on / off the second light source. .