JP2001004491A - Apparatus for inspecting light beam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute excellently inspection of the parallelism, inclination and power distribution of collimated light. SOLUTION: This apparatus is equipped with a collimator lens 2 making a light beam of a semiconductor laser 1 into parallel beams, an imaging lens 3 imaging the light from the lens 2 and focusing it, an image pickup element 4, a means 5 for changing the state of a focus by changing a distance between the image pickup element 4 and the imaging lens 3, a means 6 for displaying a luminescent spot imaged on the image pickup element 4 and an image processing device 7 measuring feature values from the image of the image pickup element 4. A shift in the X, Y direction of a point of emission of the semiconductor laser 1 or the inclination of collimated light is detected from the position of the luminescent spot at the focusing position of the light beam, while a shift of the focusing position from a reference position which is the focusing position based on a reference beam is measured and the amount of the shift in the direction of the optical axis of the point of laser emission of the semiconductor laser 1 or the parallelism of the collimated light is determined from the magnification of an optical system. By observing a defocused image in a condition that the image pickup element 4 is shifted by a prescribed amount from the focusing position and by measuring a peak position in luminance distribution, besides, the shift in the direction of laser emission of the semiconductor laser 1 or the power distribution of the collimated light is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a light beam inspection device. More specifically, the present invention relates to a light beam inspection apparatus suitable for inspection of collimated light, such as an optical pickup device.

[0002]

2. Description of the Related Art In an apparatus using a parallel light beam (collimated light) generated by using a semiconductor laser (laser diode: LD) and a collimating lens, such as an optical pickup device, it is necessary to obtain high-quality collimated light. Therefore, inspection of collimated light is performed. In conventional inspection of collimated light, the collimated light passing through a collimating lens is reflected by a mirror or the like to increase the distance traveled by the light, and the inspection is performed in a state where the deviation of the optical axis and the parallelism are amplified. .

As another method, a method of inspecting collimated light using an autocollimator has been considered. FIG. 9 shows the principle of the inspection using this autocollimator. Light emitted from the light source 101 through the condenser lens 102 through the illumination-side focusing screen 103 forms a parallel light beam from the objective lens 104, travels to the opposing reflecting mirror 105, is reflected and passes through the objective lens 104 again, and passes through the eyepiece 106.
An image is formed on the reticle 107 on the side. Here, the reflecting mirror 105
Is tilted by the angle θ, the image is formed on the reticle 107 at a position shifted by d. Assuming that the focal length of the objective lens 104 is f, d = f · tan2θ ≒ 2fθ. Therefore, by measuring d, the inclination angle θ can be calculated. That is, a parallel light beam based on this principle is considered as collimated light generated by a semiconductor laser and a collimating lens, and inspection is performed using an autocollimator.

[0004]

However, in the method of performing inspection by increasing the traveling distance of the collimated light, a large space is required for inspection. In the inspection of collimated light, it is necessary to evaluate the parallelism, inclination, and power distribution of the collimated light. It is difficult to quantify and inspect all of the parallelism, inclination, and power distribution of.

If the optical axis direction of the laser is defined as the Z direction, and two directions perpendicular to the Z direction are defined as the XY directions, the deviation of the laser emission point in the XY directions causes the inclination of the collimated light. In this case, the image is shifted in the X and Y directions (the direction is point-symmetric with respect to the optical axis). In addition, the deviation of the laser emission point in the Z direction causes deterioration of the parallelism of the collimated light, and in this case, the focal position of the image is shifted. Further, a shift in the laser emission direction (a shift in the θ direction) causes a bias in the power distribution of the collimated light, and in this case, a bias in the luminance distribution occurs in the image formation at the defocus position. Therefore, it is possible to quantify and inspect the inclination, parallelism, and power distribution of the collimated light based on these phenomena.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a light beam inspection apparatus which does not require a large space for the inspection and can inspect the parallelism, inclination and power distribution of collimated light satisfactorily. I do.

[0007]

According to one aspect of the present invention, there is provided a light beam inspection apparatus, comprising: a laser source; a collimating lens for converting a light beam emitted from the laser source into parallel light; An imaging lens that forms an image by focusing light from the camera, an imaging element, a unit that changes a focal state by changing a distance between the imaging element and the imaging lens (a movable unit), and a luminous element formed on the imaging element. Means for displaying points;
Equipped with an image processing device that measures the feature value from the image of the image sensor, while detecting the shift in the XY direction of the laser emission point of the laser source or the inclination of the collimated light from the position of the bright spot at the focus position of the light beam, The displacement between the reference position, which is the focus position by the reference beam, and the focus position is measured, and the displacement of the laser emission point of the laser source in the optical axis direction or the parallelism of the collimated light is obtained from the magnification of the optical system. .

A light beam emitted from a laser source is converted into parallel light (collimated light) by a collimating lens, and then is imaged on an image sensor by an imaging lens. This image is displayed on means (display means) for displaying the bright spot formed on the image sensor. The image processing device measures the characteristic value of the collimated light based on the image. Here, assuming that the optical axis direction is the Z-axis direction and two directions perpendicular to the Z-axis direction are the X and Y directions, if the laser emission point of the laser source is shifted in the X and Y directions, the collimated light is Since the bright point is tilted with respect to the optical axis, the bright spot displayed on the display means is displayed shifted by a distance corresponding to the shift. Therefore, it is possible to determine the displacement of the laser emission point of the laser source in the X and Y directions or the inclination of the collimated light based on the displacement of the displayed bright point. In addition, if a reference position at which light passing through the imaging lens is focused is determined in advance using a reference light that is an accurate parallel light, the image pickup device is located at a focusing position at which the light to be inspected is focused by the movable means. Is moved to obtain the in-focus position, whereby the shift of the laser emission point of the laser source in the optical axis direction (Z-axis direction) is obtained based on the shift between the reference position and the in-focus position, and the parallelism of the collimated light is obtained. Can be requested.

According to a second aspect of the present invention, there is provided a light beam inspection apparatus, comprising: a laser source; a collimator lens for converting the light beam emitted from the laser source into parallel light; and a focusing device for imaging and focusing light from the collimator lens. An image lens, an image sensor, means for changing the focal state by changing the distance between the image sensor and the imaging lens (movable means), means for displaying bright spots formed on the image sensor, and an image of the image sensor An image processing device that measures the characteristic value from the laser beam, detects the shift of the laser emission point of the laser source in the XY directions or the inclination of the collimated light from the position of the bright spot at the focus position of the light beam, and focuses the image sensor. Observe the defocused image with a certain amount of deviation from the position, measure the peak position of the luminance distribution, and detect the deviation in the laser emission direction of the laser source or the power distribution of the collimated light Than it is.

A light beam emitted from a laser source is converted into parallel light (collimated light) by a collimating lens, and is then imaged on an image sensor by an imaging lens. This image is displayed on means (display means) for displaying the bright spot formed on the image sensor. The image processing device measures the characteristic value of the collimated light based on the image. Here, assuming that the optical axis direction is the Z-axis direction and two directions perpendicular to the Z-axis direction are the X and Y directions, if the laser emission point of the laser source is shifted in the X and Y directions, the collimated light is Since the bright point is tilted with respect to the optical axis, the bright spot displayed on the display means is displayed shifted by a distance corresponding to the shift. Therefore, it is possible to determine the displacement of the laser emission point of the laser source in the X and Y directions or the inclination of the collimated light based on the displacement of the displayed bright point. In addition, the defocused image is displayed by moving the imaging device by a fixed amount from the in-focus position by the movable means. The luminance distribution appears clearly in the defocused image, and when the laser emission direction of the laser source is shifted, the peak position of the luminance distribution is displayed shifted. Therefore, it is possible to detect a shift in the laser emission direction of the laser source or a power distribution of the collimated light based on the shift in the peak position of the luminance distribution of the displayed defocused image.

Further, in the light beam inspection apparatus according to the third aspect, the light from the laser source and the collimating lens of the optical pickup device is inspected. Therefore, an inspection apparatus suitable for inspection of a parallel light beam obtained by the laser source and the collimating lens of the optical pickup device can be obtained.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail based on the best mode shown in the drawings.

FIG. 1 shows an example of an embodiment of a light beam inspection apparatus to which the present invention is applied. Light beam inspection equipment
For example, a semiconductor laser 1 as a laser source, a collimating lens 2 for converting a light beam emitted from the semiconductor laser 1 into parallel light, an imaging lens 3 for forming an image of the light from the collimating lens 2 for focusing, and an image sensor 4 , This imaging device 4
Means 5 for changing the focus state by changing the distance between the lens and the imaging lens 3; means 6 for displaying the bright spot formed on the image sensor 4;
Image processing device 7 for measuring characteristic values from the image of image sensor 4
And detects a shift in the XY direction of the laser emission point of the semiconductor laser 1 or an inclination of the collimated light from the position of the luminescent spot at the focus position of the light beam. The light beam inspection device measures a shift between the reference position, which is a focus position by the reference beam, and the focus position, and calculates a shift amount of the laser emission point of the semiconductor laser 1 in the optical axis direction from the magnification of the optical system. Alternatively, the degree of parallelism of the collimated light is obtained. Further, the light beam inspection device observes the defocused image with the imaging element 4 shifted from the in-focus position by a fixed amount, measures the peak position of the luminance distribution, and This is to detect the displacement or the power distribution of the collimated light. In the present embodiment, for example, light from the semiconductor laser 1 and the collimating lens 2 of the optical pickup device 15 is to be inspected.

The direction of the optical axis of the semiconductor laser 1 is defined as a Z-axis direction, and two directions perpendicular to the Z-axis direction are defined as X and Y directions.
Direction.

The laser light emitted from the semiconductor laser 1 (laser diode: LD) of the optical pickup device 15 passes through the collimating lens 2 to become parallel light (collimated light), and is focused by the imaging lens 3. The imaging element 4 is, for example, a CCD camera, and is fixed on a moving stage 8 that can move only in the Z-axis direction. The moving stage 8 is moved by a stepping motor 10 controlled by a motor controller 9. That is,
The stepping motor 10 and the moving stage 8 constitute a means 5 for changing the distance between the image sensor 4 and the imaging lens 3 to change the focus state. Further, the output of the CCD camera 4 is supplied to the image processing device 7, and three types of characteristic values of the light beam, that is, parallelism, inclination, and power distribution are measured.
The central processing unit (CPU) 11 is connected to a means 6 for displaying a bright spot formed on the image sensor 4 such as a CRT monitor, and displays an image captured by the CCD camera 4.

The focal length f2 of the imaging lens 3 is designed to be sufficiently larger than the focal length f1 of the collimating lens 2, for example, about 10 times.

In this inspection apparatus, before the inspection is performed, the reference position a (FIG. 2) is obtained using the reference light which is an accurate parallel light. That is, a reference position a at which the reference light is focused when the reference light is incident on the imaging lens 3 along the Z-axis direction is determined in advance, and when the CCD camera 4 is moved to the reference position a, the reference position a is obtained. A focused beam spot is observed (FIG. 3).

Now, consider a case where the position of the semiconductor laser 1 is shifted from the collimating lens 2 in the X and Y directions. When the position of the semiconductor laser 1 is shifted upward by a distance L1 as shown in FIG. 8, for example, the collimated light is parallel but inclined, and the beam spot is offset downward by the distance L2. Similarly, when the position of the semiconductor laser 1 is shifted to the right, for example, the beam spot is offset to the left (FIG. 4). Since the offset amount is multiplied by f2 / f1 on the CCD camera 4 side, for example, when f1 = 15 mm and f2 = 150 mm, f2 / f1 = 10, which is 10 times the actual shift amount of the semiconductor laser 1. And the amount of deviation of the semiconductor laser 1 in the XY directions can be obtained from the amount of offset.
Further, the inclination of the collimated light can be obtained based on this. That is, these can be measured with 10 times the sensitivity.

Next, consider the case where the position of the semiconductor laser 1 is shifted from the collimator lens 2 in the Z-axis direction. In this case, the light passing through the collimating lens 2 does not become an accurate parallel light but becomes a convergent light. As shown in FIG. 2B, when the position of the semiconductor laser 1 is farther from the collimator lens 2 in the Z-axis direction, the CC at the reference position a
The defocused beam is observed by the D camera 4 (FIG. 5). Although it is possible to measure the amount of displacement in the Z-axis direction by measuring this beam diameter, the direction in which the semiconductor laser 1 is displaced (the collimating lens 2
It is difficult to identify and quantify whether it is shifted in the direction away from or in the direction approaching. Therefore,
In the inspection device of the present invention, the moving stage 8 is moved by the stepping motor 10 and the CCD camera 4 is moved to a focus position c (FIG. 2B) where a focused beam spot can be observed.
To move. Then, by measuring the difference (the distance between a and c) between the in-focus position c and the reference position a, the deviation in the Z-axis direction can be accurately obtained, and based on this, the parallelism of the collimated light is calculated. You can ask. That is, the amount of movement in the Z-axis direction is (f2 / f1) ² on the CCD camera 4 side.
When f1 and f2 are the above values, a and c
The value of 1/100 of the difference is the amount of deviation of the semiconductor laser 1 in the Z-axis direction, and the parallelism of the collimated light can be obtained based on this.

Also, consider a case where the emission angle of the semiconductor laser 1 is shifted (inclined) with respect to the collimating lens 2. In this case, it is difficult to observe the brightness distribution even if the focused beam spot is captured by the CCD camera 4, but it is easy to observe the brightness distribution by capturing the defocused beam. (FIG. 6). Therefore, the defocused beam is observed by moving the CCD camera 4 to the defocus position b in FIG. Since the luminance distribution at this time has a similar shape to the emission intensity distribution of the semiconductor laser 1, by measuring the position of the maximum luminance, the angle deviation θ between the Z-axis direction and the direction of the semiconductor laser 1 can be obtained. Further, a power distribution can be obtained based on this. That is, if the position of the maximum luminance is observed at a position shifted by k from the center reference position, and if the distance between the reference position a and the defocus position b in FIG. 2A is D, θ = tan ^{− 1} ｛(f2 / f
1) · (k / D)｝

Next, a measuring procedure using the inspection apparatus of the present invention will be described.

Before the measurement, reference light (parallel light from a light source whose parallelism is guaranteed) is incident on the imaging lens 3.
Focusing is performed to minimize the bright spot. As shown in FIG. 3, the position where the bright spot becomes the smallest is the reference position a.
Becomes

After confirming the reference position a, for example, the optical system of the optical pickup device 15 is inspected. In this case, FIG.
The semiconductor laser 1 and the collimating lens 2 of the optical pickup device 15 are
It is.

First, while measuring the maximum brightness and the beam diameter of the beam spot formed on the CCD camera 4, the CC
The D camera 4 is moved in the Z-axis direction to perform focusing of the imaging optical system, and find the in-focus position c. Next, the distance between the focus position c and the reference position a is measured. Then, based on this distance, the shift amount of the semiconductor laser 1 in the Z-axis direction is obtained from the magnification of the optical system as described above. This value is a characteristic value indicating the parallelism of the collimated light.

Next, X,
The offset amount of the Y position is measured, and the shift amount of the semiconductor laser 1 in the X and Y directions is obtained from the magnification of the optical system as described above. This value is a characteristic value indicating the inclination of the collimated light.

Then, the stepping motor 10 is driven to move the moving stage 8, and the CCD camera 4 is shifted from the in-focus position c by a fixed amount to observe a defocused image.
The peak position of the luminance distribution is measured to determine the angle shift. This value is a characteristic value indicating the power distribution of the collimated light.

The quality of the collimated light of the optical pickup device 15 to be inspected is evaluated based on the measured values, that is, the three types of characteristic values.
Determine defective products. If the optical pickup device 15 to be inspected can adjust the position of the semiconductor laser 1 with respect to a defective product, the position of the semiconductor laser 1 is adjusted based on the above-described measured values. If it cannot be done, it shall be disposed of.

The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the gist of the present invention. For example, as shown in FIG. 7, a second mirror 1 having a focal length of f3 (レ ン ズ f1≪f2) with a half mirror 12 interposed between the collimator lens 2 and the imaging lens 3.
A part of the collimated light is led to 3 and the second CCD camera 1
4, a defocused image may be obtained.
Generally, it is necessary to move the CCD camera 4 to a position sufficiently far from the reference position a in order to obtain a defocused image enough to measure the luminance distribution. However, by adopting a configuration as shown in FIG. There is no need to move the camera 4 significantly.

Further, by providing an adjuster for adjusting the position of the semiconductor laser 1 to be inspected, the position of the semiconductor laser 1 may be automatically adjusted based on the inspection result.

In a configuration in which a total reflection mirror is inserted between the semiconductor laser 1 and the collimating lens 2 to bend the optical path, both the attitude of the semiconductor laser 1 and the attitude of the total reflection mirror affect the quality of the collimated light. In this case, the inspection apparatus of the present invention is effective.

Further, instead of the means 5 for changing the distance between the CCD camera 4 and the imaging lens 3, a focusing state is searched for using a lens with a distance ring, and the distance ring rotation angle from the reference position a is determined by the parallelism. May be used as an index.

The laser source is not limited to the semiconductor laser 1 as a matter of course.

[0033]

As described above, in the light beam inspection apparatus according to the first aspect, the laser source, the collimating lens for converting the light beam emitted from the laser source into parallel light,
An imaging lens that forms an image by focusing light from a collimating lens; an imaging element; a unit that changes a focus state by changing a distance between the imaging element and the imaging lens; and a luminescent spot formed on the imaging element. Means for displaying, and an image processing device for measuring a characteristic value from an image of the image sensor, wherein a deviation of the laser emission point of the laser source in the XY direction or a tilt of the collimated light from the position of the luminescent spot at the focus position of the light beam. And the displacement between the reference position, which is the focus position by the reference beam, and the focus position is measured. Based on the magnification of the optical system, the shift amount of the laser emission point of the laser source in the optical axis direction or the parallelism of the collimated light is measured. , The inclination and parallelism of the collimated light can be measured with high accuracy, and the quality of the collimated light can be quantified and evaluated based on these values. Non-defective, it is possible to easily discriminate defective. In addition, the measurement of these values can be automated by processing the image obtained from the image sensor with an image processing device, and can be adjusted from the inspection by interlocking with the adjustment mechanism that adjusts the position of the laser source. It is possible to automate a series of operations up to this point. Further, since it is not necessary to reflect the collimated light many times to secure a long optical path, a large space is not required for the inspection.

Further, in the light beam inspection apparatus according to the second aspect, a laser source, a collimating lens that converts the light beam emitted from the laser source into parallel light, and a focusing device that forms an image by focusing the light from the collimating lens. An image lens, an image sensor,
Means for changing the focus state by changing the distance between the image sensor and the imaging lens, means for displaying bright spots formed on the image sensor, and an image processing device for measuring a feature value from an image of the image sensor, Detecting the deviation of the laser emission point of the laser source in the XY directions or the inclination of the collimated light from the position of the luminescent spot at the focus position of the light beam, and defocusing the image sensor with the image sensor shifted by a fixed amount from the focus position By observing the image and measuring the peak position of the luminance distribution to detect the deviation in the laser emission direction of the laser source or the power distribution of the collimated light, the deviation of the optical axis of the collimated light and the power distribution are increased. In addition to being able to measure with accuracy, the quality of the collimated light can be quantified and evaluated based on these values, making it easy to discriminate between non-defective products and defective products to be inspected. Kill. In addition, the measurement of these values can be automated by processing the image obtained from the image sensor with an image processing device, and can be adjusted from the inspection by interlocking with the adjustment mechanism that adjusts the position of the laser source. It is possible to automate a series of operations up to this point. Further, since it is not necessary to reflect the collimated light many times to secure a long optical path, a large space is not required for the inspection.

Further, in the light beam inspection device according to the third aspect, since the light from the laser source and the collimating lens of the optical pickup device is to be inspected, the collimated light obtained by the laser source and the collimating lens of the optical pickup device. An inspection apparatus suitable for the inspection can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an example of an embodiment of a light beam inspection device according to the present invention.

2A and 2B show an optical system of the inspection apparatus, wherein FIG. 2A is a schematic configuration diagram when a semiconductor laser position is ideal, and FIG. 2B is a schematic diagram when a semiconductor laser position is shifted in an optical axis direction. It is a block diagram.

FIG. 3 is a schematic configuration diagram illustrating a captured image of a CCD camera that has captured a reference light at a reference position.

FIG. 4 is a schematic configuration diagram showing an image captured by a CCD camera when a position of a semiconductor laser is shifted in a Y-axis direction.

FIG. 5 is a schematic configuration diagram showing a captured image of a CCD camera when a position of a semiconductor laser is shifted in a Z-axis direction.

FIG. 6 shows CC when the direction of the semiconductor laser is shifted.
FIG. 2 is a schematic configuration diagram illustrating an image captured by a D camera.

FIG. 7 shows another embodiment of the light beam inspection apparatus of the present invention, and is a schematic configuration diagram of an optical system thereof.

FIG. 8 is a schematic configuration diagram showing an optical system of the inspection apparatus of the present invention, in a case where a position of a semiconductor laser is shifted in XY directions.

FIG. 9 is a schematic configuration diagram of a conventional inspection method.

[Explanation of symbols]

Reference Signs List 1 semiconductor laser (laser source) 2 collimating lens 3 imaging lens 4 CCD camera (imaging element) 6 CRT monitor (means for displaying bright spots) 7 image processing device 8 moving stage (distance between imaging element and imaging lens) Stepping motor (means for changing the distance between the image sensor and the imaging lens)

Claims (3)

[Claims] 1. A laser source, a collimator lens that converts a light beam emitted from the laser source into parallel light, an imaging lens that forms an image by focusing light from the collimator lens, an image sensor, and the image sensor. Means for changing the focus state by changing the distance between the imaging lenses, means for displaying bright spots formed on the image sensor, and an image processing device for measuring a characteristic value from an image of the image sensor; XY of the laser emission point of the laser source from the position of the luminescent spot at the focused position of the beam
In addition to detecting the deviation of the direction or the inclination of the collimated light, the deviation between the reference position, which is the focus position by the reference beam, and the focus position is measured, and the optical axis of the laser emission point of the laser source is obtained from the magnification of the optical system. An inspection apparatus for a light beam, wherein a deviation amount in a direction or a parallelism of the collimated light is obtained. 2. A laser source, a collimating lens for converting a light beam emitted from the laser source into parallel light, an imaging lens for imaging and focusing light from the collimating lens, an image sensor, and the image sensor. Means for changing the focus state by changing the distance between the imaging lenses, means for displaying bright spots formed on the image sensor, and an image processing device for measuring a characteristic value from an image of the image sensor; XY of the laser emission point of the laser source from the position of the luminescent spot at the focused position of the beam
In addition to detecting the deviation of the direction or the inclination of the collimated light, the defocused image is observed in a state where the image sensor is shifted from the in-focus position by a certain amount, the peak position of the luminance distribution is measured, and the laser of the laser source is measured. A light beam inspection apparatus for detecting a shift in an emission direction or a power distribution of the collimated light. 3. The light beam inspection apparatus according to claim 1, wherein light from a laser source and a collimating lens of the optical pickup device is an object to be inspected.