JP3070140B2 - Inspection method and inspection device for surface condition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for inspecting a surface condition, and more particularly to a method for inspecting defects such as scratches, dirt and stains on an outer ring or affecting its original function by using optical means. The present invention relates to a method and an apparatus for inspecting a surface state to be inspected.

[0002]

2. Description of the Related Art Parts such as drums used in copying machines and the like have conventionally been required to be visually inspected for defects existing on the surface, for example, scratches, dirt, and stains. Defects such as scratches that appear in the surface shape are measured using light scattering, diffraction or reflection intensity, while density defects such as dirt and stains are measured by measuring the reflectance or using white fluorescent light. Means have been taken to perform visual detection using a lamp, an ultraviolet lamp, or the like.

[0003]

However, the inspection method used in the conventional example has various practical problems. For example, as described in the above description, since the detection method is different for a shape defect such as a scratch and a density defect such as dirt or a stain, it is difficult to detect both at the same time, and each requires a separate device and time. It has been. This has a great effect particularly on cost in the case of products that are premised on mass production.

[0004] In particular, since the detection of density defects must be of a degree which can be finally judged visually, it is difficult to automatically measure the reflectivity by measurement, and in practice, it depends on visual inspection. Was the most.

However, when an object on which a defect is formed, that is, a state in which the color of the drum and the color of the density defect are close to each other in a protective color, it is difficult to detect the defect visually and causes fatigue of the inspector. Further, when an ultraviolet lamp is used, the energy density is low, so that it may not be possible to detect some defects. As described above, in the visual inspection, there are some elements that are not stable due to omission of detection of a defect or fluctuation of a determination standard.

According to the present invention, there is provided a method and apparatus for inspecting a surface state which solves the above two conventional problems, namely, simultaneous detection of a shape defect and a density defect, automatic detection of a density defect and improvement of detection accuracy. With the goal.

[0007]

[0008]

According to the surface state inspection method of the present invention, when a defect on the surface of an object is detected, light from a light source is irradiated on the object by a projection optical system, and reflected light from the object is detected by an optical system. Upon detection by, then the light of the wavelength from the light source and the light from the defect itself are separated and detected by spectral means,
It is characterized in that a defect is determined from each light intensity information.

In the surface state inspection apparatus of the present invention, when detecting a defect on the surface of an object, light from a light source is irradiated on the object by a projection optical system, and reflected light from the object is detected by an optical system. When detecting the defect, the light of the wavelength from the light source and the light from the defect itself are separated and detected by spectral means, and the defect is determined from each light intensity information.

[0011]

FIG. 1 is a schematic view of a main part of a first embodiment of the present invention. In the figure, 1 is a He-Cd laser as a light source for exciting a defect, 2 is a mirror, 3 is He for adjusting the optical axis.
-Ne laser, 4 for aperture, 5 for filter, 6 for glass for surface reflection, 7 for mirror, 8 for photoelectric element, 9 for reflection mirror, 10 for reflecting light of excitation laser 1 for optical axis adjustment A dichroic mirror transmitting the light of the laser 3,
Reference numeral 11 denotes a lens for condensing a laser beam, and each element so far forms a light projecting optical system. Reference numeral 12 denotes an inspection target, which is a cylindrical sleeve used in a copying machine in the present embodiment, into which inspection light is incident.

13 is a filter, 14 is a condenser lens, 15
Is an optical fiber, 16 is a spectroscope, 17 is a photoelectric device, 18 is a controller for operating the wavelength range of the spectroscope, 19 is
Is a motor for driving the sleeve 12 in the rotation direction, 20 is a motor for moving the sleeve 12 in the longitudinal direction, 21 is a controller for controlling the rotation direction and the movement in the longitudinal direction, and 22 is a controller for controlling the movement of the photoelectric elements 17 and 8. A computer that analyzes signals and controls the movement of the spectrometer and sleeve. The elements 13 to 22 form a detection optical system.

The operation of the above system will be described according to the progress of light. The light emitted from the He-Cd laser 1 has its optical path bent by 90 degrees by the mirror 2, the ghost light from the mirror generated at the time of laser oscillation and the visible light existing incidentally are cut by the diaphragm 4, and then the light is further filtered by the filter 5. The visible light located near the laser light emitted from the laser discharge tube or the like is cut. Since the wavelength of the He-Cd laser is in the ultraviolet range of 325 nm, such filtering can be easily realized, and the S / N ratio for discriminating the light emitted by excitation from light can be increased. The glass 6 reflects a part of the laser light on the surface, and guides the light to the photoelectric element 8 via the reflection mirror 7. The photoelectric element 8 is used for measuring a change in the intensity of the laser light, and generates a reference signal of a detection signal described later.

The light transmitted through the glass 6 is reflected by the reflection mirror 9 and is aligned with the axis of the He-Ne laser 3 by the dichroic mirror 10. As described above, the wavelength of the He-Cd laser is out of the visible region in the ultraviolet region, and
The e-Ne laser 3 is used when adjusting the optical axis of the light receiving system. When the He-Ne laser 3 is actually measured, measures are taken to stop the oscillation so as not to enter the detection optical system. Next, the laser light reaches the condenser lens 11 and is condensed on the surface of the sleeve 12 as an object to be inspected at an incident angle of about 45 degrees.

The light receiving section is arranged at 90 degrees to the surface of the sleeve 12. Since the incident angle is around 45 degrees, this arrangement is a detection optical system that performs dark field detection that does not receive specularly reflected light. Further, unlike the laser light, the light emission generated by being excited by the He—Cd laser 1 is emitted by the defect itself, and thus has no clear directionality. Therefore, it is possible to easily detect even the arrangement as in this embodiment. . The filter 13 allows light emitted from a defect of the sleeve 12 to pass therethrough, and reduces the excitation light of the He-Cd laser 1 to 1% or less. The light transmitted through the filter 13 is condensed by a condenser lens 14 and is incident on a spectroscope 16 through an optical fiber 15. The spectroscope 16 measures the intensity for each wavelength with the photoelectric element 17 by rotating the built-in diffraction grating, and outputs the emission spectrum from the inspection object.

The computer 22 determines a defect from the signals of the photoelectric elements 17 and 8. FIG. 2 shows an example of an analysis signal sent from the photoelectric element 17. The horizontal axis shows the wavelength, and the vertical axis shows the spectrum of the detected light intensity. FIG. 2A shows the measurement at the non-defective part, and FIG. 2B shows the measurement at the dirty part. 2 (A) and 2 (B) show the spectrum of the He-Cd laser for excitation, and FIG. 2 (B) shows another example in which the laser is excited by the laser and emits light at the stained portion. Light is appearing.
Computer 22 provides a good indication of the nature of the defect at each wavelength.
Addition is performed for a certain range of the visible region, and the sum of the sums is determined to determine whether the sum is good or bad. The light emitted by the excitation light has a spectrum specific to a substance causing a concentration defect. Since the detection is performed irrespective of the color of the test object itself as a background, there is no influence of the protection color which has been conventionally difficult to visually observe. Further, since the laser beam is connected to a high-intensity laser beam, stable automatic detection can be performed without a problem of a light amount.

Further, a shape defect such as a flaw can be detected by monitoring a peak value at a He-Cd laser wavelength for performing dark field detection. In this way, by processing the output from the spectroscope 16, it is possible to simultaneously detect a geometric defect and a density defect.

In this embodiment, since the laser beam is focused on the test object 12 due to the problem of the amount of light, one inspection area is small. For this reason, the computer 22 sends an instruction to the controller 18 when confirming that the measurement in the predetermined wavelength range has been completed, and returns the spectroscope 16 to the wavelength initially instructed, and at the same time sends an instruction to the controller 21. Upon receiving this instruction, the controller 21 moves the sleeve 12 to the motor 19.
Then, the test object is moved in the longitudinal direction by the motor 20 when one rotation is completed. In parallel with these two operations, the computer 22 obtains a total sum for each predetermined wavelength range from the signals of the photoelectric elements 17 and 8, and compares the sum with a non-defective state to determine the presence or absence of a defect.

As described above, in the present embodiment, by utilizing the high brightness of the laser beam for excitation and analyzing its spectral output, stable automatic measurement can be performed even for density defects, Are simultaneously detected. Further, in this embodiment, the entire surface can be inspected by relatively scanning the test object with the excitation laser beam.

FIG. 1 shows the basic form of the present invention, but various other embodiments are also conceivable. For example, in the first embodiment, a temporal scanning signal was obtained from the photoelectric element 17 for detecting the spectroscope by rotating the diffraction grating built in the spectroscope 16. If a one-dimensional imaging device is placed in the photoelectric element unit 17 instead of rotating the diffraction grating, the same scanning signal as when rotating the diffraction grating can be obtained because the spectrum by the diffraction grating appears there. In this case, each of the elements constituting the one-dimensional image pickup element corresponds to a certain wavelength component, and the values of the respective pixels within a certain range are added, and it is possible to judge good or bad by the sum thereof. When a one-dimensional imaging device is used, there is also an effect that processing time is greatly reduced because there is no mechanical scanning.

Further, as another embodiment, it is possible to separate and detect excitation light and light emission from a defect by using a prism or a dichroic mirror as spectral means. The light condensed by the condensing lens 14 is separated by the above-described means and is incident on another photoelectric element, and the intensity is measured. In this case, the detection of light emission from the defect may be integrated using a simple photoelectric element, or the spectral distribution thereof may be signal-processed using a one-dimensional imaging element. When the light is simply received by the photoelectric element, it is necessary to adjust the characteristics of the optical system with a filter or the like in accordance with the spectral characteristics of the emitted light. Also, the characteristics of the dichroic mirror need to be selected according to the light emission from the defect. In the simplest modification, light condensed by the condenser lens 14 of the light receiving system may be directly incident on the spectroscope 16.

In the system shown in FIG. 1, the output of the laser is monitored by the photoelectric element 8 as a reference for the light intensity of the output light. Instead of performing such detection, a power stabilizer may be inserted to stabilize the intensity of the laser beam itself, thereby stabilizing the laser output. A for the stabilizer method
Several methods are known, such as using an O element,
All of them are applicable. The output may be stabilized by applying feedback to the laser itself.

[0023]

As described above, the surface state inspection method and inspection apparatus of the present invention use a new means of utilizing the physical properties of the defect itself to excite and emit light from the defect substance.
S / N
It was possible to detect it with good efficiency. Since the defect itself emits light, it is possible to perform stable automatic detection even if it is difficult to detect with the conventional technology, such as a protective color due to the effect of the measurement object. In addition, since dark field detection is possible due to the high brightness of the laser light used for excitation, the shape defect can be detected simultaneously with the density defect by measuring the scattered light. As described above, according to the present invention, it is possible to improve the detection capability and the reliability of various types of defects to be detected as well as to shorten the inspection time.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a main part of a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a signal detected in the first embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 He-Cd laser 2,7,9 mirror 3 He-Ne laser 4 Stop 5 Filter 6 Glass using surface reflection 8 Photoelectric element 10 Dichroic mirror 11 Condensing lens 12 Sleeve to be measured 13 Filter 14 Condensing lens Reference Signs List 15 optical fiber 16 spectroscope 17 photoelectric element 18 spectroscope controller 19 motor for rotating sleeve 20 motor for moving sleeve 21 controller for moving sleeve 22 computer for controlling whole system

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01N 21/88 G01N 21/952 G01B 11/30 G11B 7/00

Claims (8)

(57) [Claims] 1. A method for detecting defects on a surface of an object .
In irradiating the object with light from the light source by the light projection optical system and detecting the reflected light from the object by the detection optical system ,
Method of inspecting the surface condition characterized in that the light from the light and the defect itself wavelengths from the light source is detected and separated by the spectroscopic means, determines a defect from each of the light intensity information. 2. The method according to claim 1, wherein the light source is an ultraviolet laser. 3. The surface state inspection method according to claim 1, wherein said light projecting optical system and said detecting optical system are arranged for dark field detection. 4. The inspection of the entire surface of the object by rotating and translating the object.
Inspection method of surface condition. 5. The inspection apparatus for detecting defects on the surface of the object when the light from the light source to be detected by the detection optical system the light reflected from said object irradiated with said object in the projection optical system
And, the wavelength of the light from the light and the defect itself and separately detected by the spectral means, the inspection apparatus of the surface state, characterized in that to determine the defect from each of the light intensity information from the light source. 6. A surface condition inspection apparatus according to claim 5, wherein said light source is an ultraviolet laser. 7. The surface condition inspection apparatus according to claim 5, wherein the light projecting optical system and the detection optical system are arranged for dark field detection. 8. The whole surface of the object is inspected by rotating and moving the object.
Surface condition inspection equipment.