JP4604572B2 - Light source device and light intensity monitor used for it - Google Patents

Description

  The present invention relates to a light source device including a light amount controller, and more particularly to a light source of an inspection device that needs to maintain a constant light amount irradiated to an inspection object such as an image processing inspection device using a CCD camera or the like. It is suitable for use.

  For example, in the flat panel display manufacturing process, conventionally, image processing inspection that detects defects such as scratches and paint defects by irradiating light on the glass plate or paint coating surface that is the inspection object and observing this with a CCD camera etc. The device is in use.

  At that time, as a condition required for the light source device, the amount of light to the inspection object (object to be irradiated) does not change at least during the inspection time, and the necessary amount of light according to the light receiving sensitivity performance level of the camera to be used. For example, it can be irradiated with light.

As light sources for light source devices for image processing inspection, solid-state light elements such as halogen lamps and LEDs, discharge lamps such as mercury lamps and metal halide lamps are used, among which discharge lamps such as mercury lamps and metal halide lamps are Although it is slow in time, a high amount of light can be obtained, so it is optimal as this type of light source.
However, when these discharge lamps are lit for 1000 to 2000 hours, the amount of light irradiated to the inspection object gradually attenuates. Therefore, when using these lamps, the amount of light can be adjusted each time so that the brightness on the camera side does not change. Necessary.

Therefore, conventionally, as shown in FIG. 11, a detection optical fiber is provided at the light emitting end 33 out of the mixing rod 33 that equalizes the light amount distribution of the light irradiated from the lamp 31 and transmitted through the infrared cut filter 37 and leads to the bundle fiber 32. One end of 34 is connected, and the power supplied to the lamp 31 output from the drive circuit 36 is controlled based on the amount of light detected by the light receiving element 35 connected to the other end of the detection optical fiber 34.
JP 2001-307523 A

However, according to the inventor's experiment, when the amount of light emitted from the light emitting end 33out of the mixing rod 33 is detected, the change in the amount of light emitted from the lamp itself 31 can be accurately detected. When it was used for a line, it was found that there are cases where this change in the amount of irradiated light cannot be detected even though the amount of light applied to the inspection object has changed.
Furthermore, when the cause was pursued, the cause of the amount of light irradiating the test object being attenuated over time was not due to the change in the light emission amount of the lamp 31 itself, but rather the change in the discharge location or the light emission due to the change in the electrode. It has been found that the influence of the change in the light quantity distribution pattern of the lamp is stronger, such as the point deviating from the first focus.
That is, even if there is almost no change in the light emission amount of the lamp 31, if the light amount distribution pattern changes, the irradiation light amount irradiated to the inspection object via the bundle fiber or the like changes.

When light is derived from the light exit end 33out of the mixing rod 33 and the amount of light is detected, the amount of light emitted from the lamp 31 itself changes even if the amount of light emitted changes due to the light emission point deviating from the first focal point. Without this, this could not be detected, resulting in a fatal defect that the amount of light applied to the inspection object could not be kept constant.
This is considered to be caused by the fact that a part of the strong light emitted from the lamp 31 is also directly emitted to the portion connecting the detection optical fiber 34 of the light emitting end portion 33out.

  In fact, this apparatus has a characteristic that the ratio between the amount of light incident on the bundle fiber 32 and the amount of light of the optical fiber for detection does not change even if the light amount distribution pattern differs depending on the lamp 31. It has been impossible to detect a change in the amount of irradiation light caused by a change in pattern.

  Therefore, the present invention can accurately detect an irradiation light amount change caused by a lamp light amount change or a light amount distribution pattern change caused by a change in the light amount distribution pattern, and can maintain the irradiation light amount constant. The challenge is to do so.

In order to solve this problem, the present invention condenses the light of the lamp with a reflecting mirror, emits it from the light exit, and directly or indirectly irradiates the irradiated object with a predetermined irradiation light amount. , A light amount monitor equipped with an optical sensor for detecting the amount of light leaked from the light guide rod that is an optical path that makes the light collected by the reflecting mirror enter from the light incident end surface and guide it from the light exit end surface to the light exit port, and its detection In a light source device including a light amount controller that feedback-controls the irradiation light amount according to the light amount,
The light guide rod has a light shielding pipe as a light shielding material on its outer surface, except for a portion that guides light leakage detected by an optical sensor to the outside.
On the light incident side end face of the light guide rod, an aperture is attached that covers the peripheral edge portion and has a light-transmitting portion having a diameter smaller than the diameter of the light guide rod,
Frost treatment is performed on the light emitting end face to return a part of the light transmitted through the light guide rod into the light guide rod ,
An inner surface of an annular groove formed along the circumferential direction of the inner peripheral surface of the light shielding pipe is formed as a light diffusion surface, and the annular groove is formed in a light diffusion space for diffusing light leakage from the light guide rod. ,
The optical sensor is attached to the light diffusion space with its light detection surface facing the peripheral surface of the light guide rod .

The light guide rod not only has countless internal defects, but also has fine scratches on its outer surface, so if the light collected by the reflector is incident on the light guide rod, it will cause internal defects and scratches. Diffuse reflection occurs, and a part of the light leaks from the peripheral surface.
In particular, in the present invention, the light emitting end face of the light guide rod is frosted to such an extent that it does not affect the amount of irradiation light, so that part of the light transmitted through the light guide rod is returned into the light guide rod. The return light causes irregular reflection due to internal defects or scratches in the light guide rod, and part of the light becomes leaked light, so that the amount of leaked light is increased and the detection accuracy is improved.
And according to the experiment of the inventor, an optical sensor is provided on the peripheral surface of the light guide rod, the amount of light leaked from the light guide rod, and the tip of the bundle fiber connected to the light exit port of the light guide rod to the irradiated object As a result of detecting the amount of irradiating light, it is possible to accurately detect not only the amount of irradiating light caused by the change in the amount of light emitted from the lamp itself, but also the amount of irradiating light caused by the change in the light amount distribution pattern. It was.

That is, even if the cause is unknown, the amount of light leaked from the light guide rod corresponds to the amount of light irradiated to the irradiated object. The change in the amount of light could be detected reliably.
Therefore, if the amount of light incident on the light guide rod from the lamp is adjusted when the amount of detected light changes, the amount of light can be kept constant. In this case, the light amount adjustment may be performed by variably controlling the amount of light incident on the light guide rod using a dimming filter, for example .

The peripheral surface of the light guide rod of the light quantity monitor is covered with a light shielding material except for the part that introduces the leakage light detected by the optical sensor to the outside, so the light quantity can be accurately measured without being affected by the light incident from the outside. Can be detected.

Also, disposed in the light detection surface of the optical sensor faces the peripheral surface of the light guiding rod, by forming a light diffusion space between the circumferential surface and the light detecting surface of the light guide rod, the light diffusing space Since the light leaked into is averaged, it can be detected more accurately.

Furthermore, the light guide rod to form a light diffusion space of annular grooves formed on the inner peripheral surface of the shielding pipe is exterior, by attaching a light sensor in the light diffusion space, from the entire circumference of the light guide rod The light leakage is diffused in the light diffusion space and the entire amount of light leakage can be detected by the optical sensor, so that the detection accuracy is improved.

Tends to occur a large chips and scratches in the end face periphery of the light guiding rod, because that affects the the detection accuracy is such chipping and scratches, the light-transmitting portion of smaller diameter than the diameter of the light guide rod is formed If the aperture is attached to the light incident side end face of the light guide rod so as to cover the peripheral edge of the end face, the light passing through the chip and scratches can be blocked, resulting in improved detection accuracy.

  In this example, not only the change in the amount of light emitted due to the change in the amount of light emitted from the lamp itself, but also the change in the amount of light emitted due to the change in the light amount distribution pattern is detected accurately to keep the amount of light emitted constant. The task of maintaining was realized with a very simple configuration.

  FIG. 1 is an explanatory view showing a light source device according to the present invention, FIG. 2 is an explanatory view showing a dimming filter, FIGS. 3 to 8 are explanatory views showing a light quantity monitor, and FIG. FIG. 10 is a graph showing the relationship between the irradiation light amount and the detected light amount.

The light source device 1 shown in FIG. 1 irradiates illumination light to the inspection object via the bundle fiber 2 when, for example, imaging the surface of the inspection object (object to be irradiated) and performing product inspection by image processing. Used for.
The light source device 1 condenses the light emitted from the metal halide lamp 4 disposed in the housing 3 by the elliptical reflecting mirror 5, transmits the infrared cut filter 20, and emits the light from the light exit port 6. The inspection object is irradiated through the bundle fiber 2 connected to the light exit port 6.

Further, in the housing 3, a light amount monitor M that detects a light amount leaked from the light guide rod 8 that becomes an optical path for guiding the light collected by the reflecting mirror 5 to the light exit port 6, and according to the detected light amount. In addition to a light amount controller 7 for feedback control of the amount of irradiation light, a lighting circuit 21 for the lamp 4 and a cooling fan 22 are provided.

The light quantity monitor M includes a light guide rod 8 that serves as an optical path for guiding the light collected by the reflecting mirror 5 to the light exit 6, a silicon photocell that detects the amount of light leaked from the peripheral surface 8 a of the light guide rod 8, and the like. The photoelectric conversion type optical sensor 9 is provided.
The light guide rod 8 is formed of a translucent glass body. In this example, the light guide rod 8 is a cylindrical rod having a diameter of 12.4 mm and a length of 40 mm, and the second focal point of the reflecting mirror 5 is located at the center of the light incident end face 8in. It is attached to do.

The light quantity controller 7 is connected to the optical sensor 9 of the light quantity monitor M on the input side, and includes a step motor 11 that rotates the dimming filter 10 by a predetermined angle on the output side.
In this light control filter 10, a large number of slits whose aperture ratios gradually change are arranged on the circumference (see FIG. 2), and the amount of transmitted light gradually increases / decreases in accordance with the rotation direction as it rotates. It has become.

3 to 8 are examples of light quantity monitors M _{1 to} M ₆ that have been prototyped , and FIGS. 7 and 8 are examples of light quantity monitors M ₅ and M _{6 according to} the present invention .
In the light amount monitor M ₁ shown in FIG. 3A, the light detection surface 9 a of the optical sensor 9 is brought into contact with the peripheral surface 8 a of the light guide rod 8.
As a result, as shown in FIG. 3B, the light transmitted through the light guide rod 8 hits the defect C in the light guide rod 8 or travels while totally reflecting in the light guide rod 8. When the light hits a scratch on the peripheral surface 8a and diffusely reflects, a part of the light leaks to the optical sensor 9 side, and the optical sensor 9 detects the amount of leakage light.

Intensity monitor M ₂ shown in FIG. 4 (a), a mounting hole 12 for mounting the optical sensor 9 shielding pipe which is formed through the wall 13a (light shielding member) 13 is fitted on the guiding rod 8, the optical sensor 9 The peripheral surface 8a of the light guide rod 8 is covered with a light-shielding material, except for the part that guides light leakage detected by the above.
According to this, but the amount of light leakage at the optical sensor 9 is detected is the same as the light quantity monitor M _1, the peripheral surface 8a as shown in FIG. 4 (b), the outer guiding rod 8 brightness It is not affected by changes or external light leaking into the housing 3.
Further, when the inner surface of the mounting hole 12 is formed by the light diffusion surface 12a and the light detection surface 9a of the light sensor 9 is mounted facing the peripheral surface 8a of the light guide rod 8, the light detection surface 9a and the light guide rod A gap (e.g., about 8 mm) between the eight peripheral surfaces 8a is a light diffusion space 14 surrounded by the light diffusion surface 12a.
Thereby, since the light leakage from the mounting hole 12 is scattered and averaged in the light diffusion space 14, it is considered that the detection accuracy becomes higher.

Figure 5 intensity monitor M ₃ shown in (a), the inner peripheral surface of the shielding pipe 15 which is fitted on guide rod 8, the inner surface of the light diffusion surface 16a of the annular groove 16 formed along the circumferential direction The light sensor 9 is attached to the light diffusion space 17 with a predetermined gap (for example, about 8 mm) facing the peripheral surface of the light guide rod 8.
According to this, as shown in FIG. 5B, the light diffusion space 17 is formed over the entire circumference of the peripheral surface 8 a of the light guide rod 8, and not only the portion facing the optical sensor 9 but also the light guide. Light leakage from the entire circumference of the rod 8 is diffused in the light diffusion space 17 and the entire amount of light leakage can be detected by the optical sensor, so that the detection accuracy is improved.

The light quantity monitor M ₄ shown in FIG. 6A has an aperture 18 in which a light transmitting end 18 a having a diameter smaller than the diameter of the light guide rod 8 is formed on the light incident end face 8 in of the light guide rod 8 of the light quantity monitor M _3. The light incident side end face peripheral edge 8b of the light guide rod 8 is covered by this.
According to this, as shown in FIG. 6 (b), even if a large chip or scratch is generated in the end face peripheral portion 8b of the light guide rod 8, light transmitted through the chip or scratch can be blocked. Therefore, the detection accuracy is not adversely affected, and as a result, the detection accuracy is improved.

Light amount monitoring M ₅ shown in FIG. 7 (a), the light emitting end face 8out of the light guide rod 8 of the light amount monitor M _3, to the extent that the irradiation light amount is not significantly reduced, a part of the light transmitted through the light guiding rod 8 Frost processing is performed to return the light into the light guide rod 8.
According to this, as shown in FIG. 7B, a part of the light transmitted through the light guide rod 8 is returned into the light guide rod 8, and the return light is irregularly reflected by internal defects or scratches of the light guide rod 8. And a part thereof becomes light leakage, so that the amount of light leakage increases and the detection accuracy is further improved.
The frost process is formed by roughening the light emitting end face 8out. However, the light passing through the light emitting end face 8out is irregularly reflected by the frost process to cause a light quantity loss, but the detected light quantity is improved accordingly.

FIG. 9 is a graph showing changes in the detected light amount and the irradiated light amount with respect to the light loss due to the frost processing, where the horizontal axis represents the light loss of the light transmitted through the light guide rod when the frost processing is performed, the left scale of the vertical axis represents the irradiated light amount, The scale on the right side of the vertical axis is the detected light amount, and in all cases, the light amount when the frost process is not performed (light loss 0) is defined as 100%.
According to this, as the surface is roughened by the frost processing and the light loss is increased, the detected light amount is increased and the detection accuracy is improved, but the irradiated light amount from the bundle fiber 2 is decreased.
Therefore, for example, if the irradiation light quantity is secured at 90% or more and the detection light quantity is secured at 200% or more, the light loss due to the frost process needs to be suppressed to about 4.5 to 5.5%.

Further, the light quantity monitor M ₆ shown in FIG. 8 (a), the light incident end face 8in of the light guide rod 8 of the light amount monitor M _5, made by mounting the aperture 18 used in the light quantity monitor M _4.
According to this, as shown in FIG. 8B, the disturbance is removed by the aperture 18, and the amount of leakage light is increased by the frost processing, and the detection accuracy is further improved.

10 using the intensity monitor M ₁ ~M ₆ formed to this is a graph showing the light quantity irradiated from the bundle fiber 2, the detection light amount of the light amount monitor M ₁ ~M _6.
The change in the amount of irradiated light can be broadly divided into a case caused by a change in the light amount of the lamp 4 and a case caused by a change in the light amount distribution incident on the bundle fiber 2.
Therefore, the light quantity detected by the light quantity monitors M _{1 to} M ₆ is measured with respect to the irradiation light quantity when the light quantity incident on the light guide rod 8 from the lamp 4 is changed, and the position of the second focal point of the reflecting mirror 5 is guided. The detected light amount with respect to the irradiation light amount when the light amount distribution was changed by shifting from the center of the rod 8 was measured.

The horizontal axis of the graph represents the amount of irradiation light, the vertical axis represents the amount of detection light, and the amount of irradiation light is the amount of light detected by the optical sensor disposed at the light exit end of the bundle fiber 2 when the lamp 4 is lit at the rated voltage. The detected light quantity is a value normalized with the light quantity detected by the light quantity monitors M _{1 to} M ₆ when the irradiation light quantity is 100 as 100.

A broken line L ₀ indicates the detected light amount of the light amount monitors M _{1 to} M ₆ with respect to the irradiation light amount when the light control filter 10 is rotated to change the incident light amount to the light guide rod 8.
In this case, the measurement results of all the light quantity monitors M _{1 to} M ₆ are the same, and the detected light quantity accurately follows the irradiation light quantity.

Solid lines L _{1 to} L ₆ indicate changes in the detected light amounts of the light amount monitors M _{1 to} M ₆ with respect to changes in the amount of irradiated light that changes by shifting the position of the second focal point of the reflecting mirror 5 from the center of the light guide rod 8.
In this case, the aperture 18 is attached to the light incident end face 8in of the light guide rod 8, the detection light amount of the light amount monitor M ₆ subjected to frost treatment to the light emitting end face 8out are accurately follow the irradiation light amount (solid line L ₆ reference).
Therefore, the light amount monitor M ₆ can detect the amount of leakage light and control the amount of irradiation light based on whether the change in the amount of irradiation light is caused by the light amount change of the lamp 4 or the light amount distribution change. .

Further, the other light quantity monitors M _{1 to} M ₅ do not accurately follow the irradiation light quantity over the entire range, but in the range near the irradiation light quantity 100%, the detected light quantity is the same as the light quantity monitor M _6. There has been accurately follow irradiation light amount (see a solid line _L 1 ~L _5).
That is, the leakage light amount detected by the optical sensor 9 corresponds to the irradiation light amount irradiated from the bundle fiber 2, and therefore, even when the change in the irradiation light amount is caused by the light amount change of the lamp 4, it is also caused by the light amount distribution change. Even in this case, it is possible to control the irradiation light amount based on the leakage light amount.

The above is one configuration example of the present invention, and the operation thereof will be described next.
Since the irradiation light amount after lighting for 1500 to 2000 hours is expected to be reduced by about 40% compared to the initial light amount, the light amount of the lamp 4 is reduced to about 60% by the dimming filter 10 from the beginning. .
In this state, the detected light quantity Q ₀ detected by the optical sensor 9 of the light quantity monitor M (M _{1 to} M ₆ ) is stored in the light quantity controller 7 as 100%, and the detection initially stored when the detected light quantity Q changes. rotating the dimming filter 10 equal to the quantity Q _0.
Since the detected light quantity Q tends to decrease with time, for example, when the detected light quantity Q decreases by 1%, the dimming filter 10 is rotated in the direction in which the slit 10a becomes larger, and the detected light quantity Q = 100 (% ) Adjust the amount of light so that

In this case, the detected light quantity Q is always maintained at 100 (%), and the light quantity is adjusted every time the detected light quantity Q changes by 1%. Therefore, the detected light quantity Q always changes in the vicinity of 100 (%). Even when any of the light quantity monitors M _{1 to} M ₆ is used, a change in the quantity of irradiated light can be accurately detected.
Moreover, even if the cause is caused by a change in the light amount of the lamp 4 or a change in the light amount distribution, the amount of irradiation light can be accurately detected regardless of the cause.

  In this way, by gradually increasing the amount of light incident on the light guide rod 8 by the dimming filter 10 according to the detected amount of light, even after lighting for 1500 to 2000 hours, irradiation is performed with a light amount substantially equal to the initial irradiation light amount. Can do.

In the above description, the light control filter 10 that variably controls the amount of light incident on the light guide rod 8 is used as the light amount controller 7. May be.
Further, the present invention is not limited to the case of using the lamp 4 that irradiates visible light, but can also be applied to a light irradiation apparatus that uses an ultraviolet lamp or an infrared lamp as a light source.

  As described above, according to the light source device of the present invention, it is possible to detect both the irradiation light amount change caused by the lamp light amount change and the irradiation light amount change caused by the light amount distribution change. There is an excellent effect that the irradiation light quantity can be controlled to be kept constant based on the light quantity.

  The present invention requires that the amount of light to the inspection object (object to be irradiated) does not change at least during the inspection time, and that it can irradiate with the necessary amount of light according to the light receiving sensitivity performance level of the camera used. The present invention can be applied to light source devices such as image processing inspection devices.

Explanatory drawing which shows the light source device which concerns on this invention. Explanatory drawing which shows a light control filter. Explanatory drawing which shows a light quantity monitor. Explanatory drawing which shows a light quantity monitor. Explanatory drawing which shows a light quantity monitor. Explanatory drawing which shows a light quantity monitor. Explanatory drawing which shows a light quantity monitor. Explanatory drawing which shows a light quantity monitor. The graph which shows the relationship between the light loss by a frost process, a detected light quantity, and an irradiation light quantity. The graph which shows the relationship between irradiation light quantity and detection light quantity. Explanatory drawing which shows a conventional apparatus.

Explanation of symbols

1 Light source device 4 Lamp 5 Reflector 5
6 Light exit 6
M (M _{1 to} M ₆ ) Light quantity monitor 7 Light quantity controller
8 Light guide rod 8a Peripheral surface 9 Optical sensor 9a Light detection surface 10 Light control filters 12a and 16a Light diffusion surfaces 13 and 15 Light shielding pipe (light shielding material) 13
14, 17 Light diffusion space 16 Annular groove 18 Aperture

Claims (2)

When the light from the lamp is condensed by the reflecting mirror and emitted from the light exit, and the object is irradiated directly or indirectly with a predetermined amount of light, the light collected by the reflecting mirror is incident on the light. A light quantity monitor equipped with a light sensor that detects the amount of light leaked from the light guide rod, which is an optical path that enters from the end face and leads from the light exit end face to the light exit opening, and the light quantity for feedback control of the irradiation light quantity according to the detected light quantity In a light source device equipped with a controller,
The light guide rod has a light shielding pipe as a light shielding material on its outer surface, except for a portion that guides light leakage detected by an optical sensor to the outside.
On the light incident side end face of the light guide rod, an aperture is attached that covers the peripheral edge portion and has a light-transmitting portion having a diameter smaller than the diameter of the light guide rod,
Frost treatment is performed on the light emitting end face to return a part of the light transmitted through the light guide rod into the light guide rod ,
An inner surface of an annular groove formed along the circumferential direction of the inner peripheral surface of the light shielding pipe is formed as a light diffusion surface, and the annular groove is formed in a light diffusion space for diffusing light leakage from the light guide rod. ,
The light source device, wherein the light sensor is attached to the light diffusion space with its light detection surface facing the peripheral surface of the light guide rod . In a light amount monitor comprising a light guide rod that becomes an optical path for guiding light emitted from a light source, and a light sensor that detects a leakage light amount from the peripheral surface of the light guide rod,
The light guide rod has a light shielding pipe as a light shielding material on its outer surface, except for a portion that guides light leakage detected by an optical sensor to the outside.
On the light incident side end face of the light guide rod, an aperture is attached that covers the peripheral edge portion and has a light-transmitting portion having a diameter smaller than the diameter of the light guide rod,
Frost treatment is performed on the light emitting end face to return a part of the light transmitted through the light guide rod into the light guide rod ,
An inner surface of an annular groove formed along the circumferential direction of the inner peripheral surface of the light shielding pipe is formed as a light diffusion surface, and the annular groove is formed in a light diffusion space for diffusing light leakage from the light guide rod. ,
The light sensor according to claim 1, wherein the light sensor is mounted in the light diffusion space with its light detection surface facing the peripheral surface of the light guide rod .

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