JPH09318558A - Method for inspecting pinhole and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a highly accurate and stable inspection result by stepwise increasing the quantity of the irradiated light from a light source on the basis of the quantity value of the transmitted light from an object to be inspected detected by a photodetector. SOLUTION: A light source and a photodetector are provided in a dark box 12 so as to hold a sheet material 14 being an object to be inspected. The sheet material 14 is held by the chucks 16 provided to both outside surfaces of the dark box 12. The light source is equipped with a light emitter and the photodetector consists of a photomultiplier 30, a counter 34 and a shutter 34. For example, the photomultiplier tube 30 has sensitivity wavelength range of 300 650nm and the max. sensitivity in the vicinity of 400nm. The counter 34 converts the voltage of a photomultiplier tube 30 to the quantity of incident light and converts the converted value to pulse voltage to output the same to a control unit 40. The control unit 40 controls the quantity of the light from the light source and the opening and closing of the shutter 32 on the basis of the pulse voltage and also judges the presence of the pinhole of the object to be inspected and the quality of the object to be inspected to display the judge result on a display 42.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for inspecting the presence or absence of pinholes in an opaque sheet material used as a light-shielding member in optical equipment or the like.

[0002]

2. Description of the Related Art In an optical device, an opaque sheet material is used for the purpose of shielding light from a gap between components of the optical device. Particularly in a shutter curtain of a camera, since it is used immediately before a photosensitive film, a light shielding property is strongly required. That is, if the shutter curtain has a translucent defect such as a minute pinhole, the light passing through the pinhole exposes the film for a long time. Therefore, the amount of exposure (light intensity x
Time), which adversely affects the image quality.

Conventionally, visual inspection by human eyes has been carried out in order to detect this type of defect. However, human inspection has short accumulation capacity and is not quantitative, and variations due to individual differences occur. There was a drawback that it lacked objectivity. So, recently, without relying on visual inspection,
2. Description of the Related Art Inspection devices that can objectively judge by measuring the amount of light passing through a pinhole with a photodetector have been used. In such an inspection apparatus, a highly sensitive light receiving element, a photomultiplier tube (hereinafter referred to as “photomal”), or the like is used as a photodetector in order to detect weak light with high accuracy.

[0004]

However, in the prior art as described above, when there is a large defect such as a crack in the opaque sheet material to be inspected, the photocathode of a highly sensitive light receiving element or photomultiplier is used. A large amount of light is incident on the photodetector, and damages the photodetector, making it impossible to measure. This kind of damage can be recovered by leaving the light receiving element or the photomultiplier in the dark room for several hours, but there is a problem that the inspection cannot be performed during that time.

Therefore, according to the present invention, even an inspection object having a defect such as a crack that allows a large amount of light to pass therethrough can be inspected without being damaged to the extent that the photodetector cannot be measured. It is an object of the present invention to provide a pinhole inspection method and device capable of performing the above.

[0006]

In order to achieve the above object, according to the first aspect of the present invention, the light from the light source is applied to the object to be inspected and the amount of light passing through the object to be inspected is changed. Provided is a pinhole inspection method for detecting the presence or absence of a pinhole in an object to be inspected based on the light amount value detected by the photodetector, which is detected by the photodetector. It is characterized in that the light quantity of the light emitted from the light source is increased stepwise based on the obtained light quantity value.

According to the second aspect of the present invention, the light source for irradiating the object to be inspected with light, the photodetector for detecting the amount of light passing through the object to be inspected, the light source and the photodetector are provided. There is provided a pinhole inspection device including a control device that controls and determines the presence or absence of a pinhole in an object to be inspected based on a light amount value detected by a photodetector. However, based on the light amount value detected by the photodetector, the light source is controlled so that the light amount of the light emitted by the light source is increased stepwise. In this case, it is preferable that the light source is composed of a housing having an opening, a light emitter housed in the housing, and a diffusion plate arranged in the opening. In addition, the light emitter is a plurality of LEDs that are regularly arranged.
It is preferably composed of Further, the photodetector is connected to a housing having a window, a photomultiplier tube housed in the housing, a shutter that can open and close the window, and a photomultiplier tube. It is preferably configured with a counter. Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, at the beginning of inspection, the amount of light that the light source irradiates the object to be inspected is made minute, and thereafter, it is gradually increased based on the detection value of the photodetector. Go. Therefore, when the inspection object has a large defect such as a crack, the inspection object is determined to be defective when the light amount of the light source is very small. Moreover, since the light amount of the light source is gradually increased based on the detection value of the photodetector, even a minute pinhole can be accurately detected. The presence or absence of the pinhole is determined by the control device by comparing the detection value of the photodetector with a predetermined determination reference value. The determination reference value is set according to the degree of light-shielding property of the inspected object, and in consideration of the ratio of the amount of light emitted by the light source and the amount of light passing through the inspected object at that time. When the amount of light passing through the inspection object exceeds the determination reference value within a predetermined determination time, the inspection object is determined to be defective.

In the pinhole inspection apparatus according to the present invention, it is preferable that the light source and the photodetector are arranged near the object to be inspected. If the light source and the photodetector are installed in a dark box, it is not necessary to carry out an inspection in a dark room, which improves convenience. The light source and the photodetector are controlled by the control device that determines the presence / absence of a pinhole. The light source used in the device of the present invention is composed of a light emitter, a diffusion plate, and a housing that houses them. The light emitter may be a bulb such as a halogen lamp or a tungsten lamp, or a light emitting element such as an LED, as long as the light quantity can be changed by changing the voltage applied to the light emitter. . However, it is desirable that a stable light amount can be obtained even if the voltage is changed. Especially with an LED, it does not take time to obtain the required amount of light. Further, by arranging a plurality of LEDs regularly according to the inspection area of the inspection object, the inspection object can be uniformly irradiated. Further, when a plurality of LEDs are used, not only the applied voltage can be changed to change the light amount, but also the light amount can be changed by changing the number of LEDs to be turned on. Therefore, by using these together,
There is also an advantage that the width of the stable light amount setting range of the light source is widened.

The photodetector used in the device of the present invention comprises a photomultiplier, a counter, a shutter, and a housing for accommodating them. The shutter is installed to prevent unnecessary light from being incident on the photomal when the inspection is stopped. Photons passing through minute pinholes can be counted by using a photomultiplier and a counter.
Therefore, it is possible to perform a highly sensitive inspection.

The method and apparatus for inspecting pinholes according to the present invention are not only effective for inspecting the presence or absence of pinholes in an object to be inspected, but also, for example, a microaperture stop often used in optical equipment is used. It can also be used to inspect whether the is manufactured according to the optical design.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. Referring to FIG. 1 showing a cross section of an embodiment of a pinhole inspection device according to the present invention, a pinhole inspection device 10 includes a dark box 12, and in this dark box 12,
A light source and a photodetector, which will be described later in detail, are arranged so as to sandwich the opaque sheet material 14 which is the inspection object. The sheet material 14 is held by chucks 16 provided on both outer surfaces of the dark box 12 and having a light shielding function. The light source is a plurality of LEDs 20b (Fig. 2)
Are regularly arranged, a pick-up glass 22 as a diffusion plate, and a housing 24 accommodating the pick-up 20 and having the pick-up glass 22 attached to its opening. There is. LED 20b used in this embodiment
Is 450 nm according to the sensitivity characteristics of the photodetector described later.
61 LEDs 20b having a peak wavelength of, and having a maximum inspection area of 61 LEDs 20b are arranged in a staggered pattern in a plane as shown in FIG.
Is formed. The amount of light emitted by the light emitter 20 is controlled by the control device 40 described later.

The photodetector comprises a photo-maru 30 and a shutter 3.
2, a counter 34, and a housing 36 that houses them, and the housing 36 is formed with a window portion 36a. The Photomaru 30 used in this embodiment is 30
It has a sensitivity wavelength range of 0 nm to 650 nm and a maximum sensitivity near 400 nm. The shutter 32 that opens and closes the window portion 36a of the housing 36 is composed of a pneumatic cylinder 32a and a light shielding plate 32b provided at the tip of the rod, and the opening and closing operations are performed by moving the rod forward and backward. To do. The opening / closing operation of the shutter 32 is controlled by the control device 40 described later. The counter 34
The voltage of the photomultiplier 30 generated when a photon is incident on the photocathode 30 of the photomultiplier 30 is converted into the amount of incident light (number of incident photons / second), and the converted value is converted into a pulse voltage and output to the control device 40. The control device 40 including a microprocessor controls the light amount of the light source and the opening / closing control of the shutter based on the pulse voltage that is input from the counter 34 and represents the amount of light incident on the photomultiplier 30. The presence / absence of holes, that is, the quality of the object to be inspected is determined, and the determination result is displayed on the display 42.

Next, the pinhole inspection method according to the present invention will be described with reference to the flowchart of FIG. 3 showing the inspection procedure. The following pinhole inspection routine is executed by the control device 40 as described above.
First, in step 101, it is determined whether or not the shutter 32 is closed, that is, whether or not the pneumatic cylinder 32a is deenergized. If the determination result is negative (N),
The process proceeds to step 109, the shutter 32 is closed, and the process proceeds to step 102. On the other hand, if the determination result is affirmative (Y), the process directly proceeds to step 102.

In step 102, 13 LEDs out of 61 LEDs (see FIG. 2) are lit in order to turn on with a small amount of light.
Is turned on, and then in step 103, the shutter 32 is opened by urging the pneumatic cylinder 32a, and the process proceeds to step 104. In step 104, the amount of incident light (the number of incident photons / the number of incident photons based on the pulse voltage from the photomultiplier)
Second), and then in step 105, the measured value n1 as the measurement result is a predetermined first determination reference value N1.
It is determined whether or not this is the case. If the determination result is affirmative, it is determined that the sheet material 14 as the inspection object is a defective product, the display 42 indicates "defective" in step 106, and the pneumatic cylinder 32a is deactivated in step 107. Then close the shutter 32, and
In step 108, the LED is turned off. On the other hand, if the determination result in step 105 is negative, the process proceeds to step 110.

In step 110, 33 LEDs out of 61 LEDs are turned on to increase the light quantity, and step 1
Measure the amount of incident light at 11, then step 11
In 2, it is determined whether or not the measured value n2 is equal to or more than a predetermined second determination reference value N2 smaller than the first determination reference value. If the determination result is affirmative, the sheet material 14
Is determined to be a defective product, "defective" is displayed on the display 42 in step 113, the shutter 32 is closed (step 107), and the LED is turned off (step 1).
08). On the other hand, if the determination result in step 112 is negative, the process proceeds to step 114.

In step 114, all 61 LEDs are
Is turned on to increase the light quantity to the maximum, the incident light quantity is measured in step 115, and then, in step 116, the measured value n3 is equal to or larger than a predetermined third judgment reference value N3 smaller than the second judgment reference value. Determine if there is.
If the determination result is affirmative, it is determined that the sheet material 14 is a defective product, the display 42 displays "Defective" in step 117, the shutter 32 is closed (step 107), and the LED is extinguished (step 107). Step 108).
On the other hand, if the determination result in step 116 is negative, it is determined that the sheet material 14 as the inspection object is a non-defective product, and the display 42 displays “good” in step 118.
Is displayed and the shutter 32 is closed (step 107),
The LED is turned off (step 108), and this pinhole inspection routine ends.

In the pinhole inspection routine described above, the predetermined judgment reference values N1, N2 and N3 are set to N1.
Although it has been set such that>N2> N3, it is not always necessary to set it as such, and N1 = N2 = N3 may be set depending on the light-receiving element or the photomultiplier used. Also,
Although the light quantity of the light source is adjusted by changing the number of LEDs to be lit, instead of this, the light quantity of the light source may be adjusted by changing the voltage applied to the LED.
You may use them together.

[0019]

As described above, according to the present invention, a high-sensitivity photodetector can be inspected without being damaged, regardless of the size of the pinhole. Therefore, there is an effect that a stable inspection result can be obtained with high accuracy.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing the configuration of an embodiment of a pinhole inspection device according to the present invention.

FIG. 2 is a plan view showing an array of LEDs in a light emitter used in the pinhole inspection apparatus according to the present invention.

FIG. 3 is a flowchart showing a procedure of a pinhole inspection method according to the present invention.

[Explanation of symbols]

 10 pinhole inspection device 12 dark box 14 sheet material (inspection object) 16 chuck 20 light emitter 20a light emitting surface 20b LED 22 picked glass (diffusion plate) 24 housing 30 photomal 32 shutter 32a pneumatic cylinder 32b light shielding plate 34 counter 36 housing 36a window

Claims (5)

[Claims] 1. An object to be inspected is irradiated with light from a light source, a light amount of passing light from the object to be inspected is detected by a photodetector, and the object to be inspected is detected based on a light amount value detected by the photodetector. In a pinhole inspection method for determining the presence or absence of a pinhole in an inspection object, based on a light amount value detected by the photodetector, the light amount of the light emitted by the light source is increased stepwise. Pinhole inspection method. 2. A light source for irradiating an object to be inspected with light, a photodetector for detecting the amount of light passing through from the object to be inspected, a light source for controlling the light source and the photodetector, and the photodetector. In a pinhole inspection device comprising a control device for determining the presence or absence of a pinhole in the inspection object based on the detected light amount value, the control device is based on the light amount value detected by the photodetector. The pinhole inspection device is characterized in that the light source is controlled so that the amount of light emitted by the light source increases stepwise. 3. The light source according to claim 2, wherein the light source includes a housing having an opening, a light emitter housed in the housing, and a diffusion plate arranged in the opening. Pinhole inspection device described. 4. The pinhole inspection device according to claim 3, wherein the light emitter is composed of a plurality of LEDs arranged regularly. 5. The photodetector includes a housing having a window portion,
5. A photomultiplier tube housed in the housing, a shutter that can open and close the window portion, and a counter connected to the photomultiplier tube. The pinhole inspection device according to any one of 1.