JP2000097631A - Displacement measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable to remove light reflected nearby by the shape of an object to be measured, etc., and to permit the highly accurate measurement of especially an object to be measured with a narrow pitch. SOLUTION: Light radiated from a laser 1 is converted into circularly polarized light with the predetermined direction of rotation by a λ/4 wavelength plate 3 to irradiate an object to be measured 11. The reflected light at the object to be measured 11 is returned to linearly polarized light by a λ/4 wavelength plate 6, is transmitted through a polarization beam splitter 7, and becomes incident on the light receiving plane of a light location detecting means 8. The light location detecting means 8 outputs a displacement signal corresponding to the amount of displacement of the object to be measured 11 according to the location of reception of the reflected light on the light receiving plane. Even if the reflected light at the object to be measured 11 is secondarily reflected by a nearby object to be measured 12 toward the λ/4 wavelength plate 6, the stray light component 33 of the reflected light is in a state of circularly polarized light with the reverse direction of rotation, is not transmitted through the polarization beam splitter 7, is bent, does not become incident on the light location detecting means 8, does aggravate measurement accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a displacement measuring device for measuring a displacement of a measuring object in a non-contact manner, and more particularly to a displacement measuring device capable of removing unnecessary reflected light at the time of measuring a narrow pitch and performing a highly accurate measurement. It relates to a measuring device.

[0002]

2. Description of the Related Art FIG. 5 is a schematic diagram showing a displacement measuring device. The light emitted from the laser 1 is transmitted to a collimator lens 2
Are collimated, and a light spot is formed on the measurement target (measurement target) 11 by the light projecting lens. The light reflected by the measuring object 11 forms a light spot on the light position detecting means 8 via the light receiving lens 5. Thereby, the displacement amount (for example, height) of the measurement target 11 can be measured according to the position of the light spot detected on the light position detection means 8.

[0003]

However, in the above configuration, when the arrangement of the measuring objects 11 is narrow,
In some cases, light reflected secondarily from a nearby measurement target 12 reduces measurement accuracy. The measurement object 11 shown is LS
A terminal of a semiconductor package such as I, and the state (coplanarity) of this terminal is to be measured. The measurement target 11 is a glossy spherical metal surface (called a solder ball or a bump) such as a BGA (Ball Grid Array), and is arranged at a narrow pitch of about 0.3 to 0.8 mm.

[0004] Such a glossy spherical measurement object 1
The light that has been projected to 1 is easily reflected toward the nearby measurement target 12 (depicted by a dotted line in the figure). Measurement object 11 of the above shape
When measuring the displacement of the light, the light (stray light component 33) secondary reflected by the measurement object 12 is reflected by the light position detecting means 8.
At the same time, there is a problem that the measurement accuracy is remarkably deteriorated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and can remove light reflected nearby due to the shape and the like of a measuring object. It is an object of the present invention to provide a displacement measuring device that can perform the measurement.

[0006]

In order to achieve the above object, a displacement measuring device according to the present invention has the following features.
In a displacement measuring device that irradiates light to a measurement target, detects the position of reflected light by a light position detection unit, and detects a displacement amount of the measurement target in a non-contact manner, light emitted from a light source is circularly moved in a predetermined rotation direction. Circularly polarized light means (3) for polarizing and irradiating the object to be measured, linearly polarizing means (6) for converting circularly polarized light reflected from the measured object to linearly polarized light, and returned to linearly polarized light by the linearly polarized light means And a transmission polarization means (7) for transmitting only the reflected light linearly polarized in a predetermined direction to the light position detection means.

According to a second aspect of the present invention, there is provided a displacement measuring apparatus for irradiating a measuring object with light, detecting a position of reflected light by a light position detecting means, and detecting a displacement amount of the measuring object in a non-contact manner. A first λ / 4 wave plate (3) for circularly polarizing light emitted from a light source in a predetermined rotation direction and irradiating the measurement target with the light, and converting the circularly polarized light reflected from the measurement target into linearly polarized light A second λ / 4 wavelength plate (6) and, of the light returned to linearly polarized light by the second λ / 4 wavelength plate, transmit only reflected light that is linearly polarized in a predetermined direction, and A polarizing beam splitter (7) for bending a linearly polarized stray light component, and a light position for receiving light transmitted through the polarizing beam splitter and outputting a displacement signal corresponding to a displacement amount of the object to be measured based on a light receiving position. Detecting means (8);
It is characterized by having.

According to a third aspect of the present invention, only the reflected light, which is linearly polarized in a predetermined direction, of the light returned to the linearly polarized light is transmitted instead of the polarization beam splitter according to the second aspect. Alternatively, a configuration may be employed in which a polarizing plate (7a) that does not transmit a stray light component linearly polarized in another direction is used.

According to a fourth aspect of the present invention, in place of the polarization beam splitter according to the second aspect, the reflected light linearly polarized in a predetermined direction out of the light returned to the linearly polarized light is transmitted to a predetermined direction. A polarizing mirror (7b) that bends in a direction and transmits a stray light component that is linearly polarized in another direction is used, and the light position detecting means (8) is configured to receive the light bent by the polarizing mirror. Is also good.

According to a fifth aspect of the present invention, the object to be measured (11) is relatively moved with respect to the displacement measuring device, and the displacement of the object to be measured is continuously measured along the moving direction. It is also possible to adopt a configuration provided with control means.

According to the present invention, the object to be measured is scanned and irradiated with light, the position of the reflected light is detected by the light position detecting means, and the displacement of the object to be measured is continuously measured along the scanning direction. A first λ / 4 wavelength plate (3) for circularly polarizing light radiated from a light source in a predetermined rotation direction and irradiating the object with the light, the first λ / 4 wavelength plate (3);
A deflecting means (22) for scanning the light after passing through the .lambda. / 4 wavelength plate (3) in a predetermined direction, and for converting circularly polarized light reflected from the measurement object into linearly polarized light. A second λ / 4 wave plate (6a) having a corresponding length;
Of the light returned to linearly polarized light by the second λ / 4 wavelength plate, only reflected light linearly polarized in a predetermined direction is transmitted, and stray light components linearly polarized in another direction are bent. A polarizing beam splitter (7c) having a length corresponding to the scanning range, a light receiving the light transmitted through the polarizing beam splitter, and outputting a displacement signal corresponding to a displacement amount of the measurement object based on a light receiving position. And position detecting means (8).

According to a seventh aspect of the present invention, only the reflected light which is linearly polarized in a predetermined direction is transmitted among the light returned to the linearly polarized light instead of the polarization beam splitter (7c) according to the sixth aspect. The stray light component which is linearly polarized in the other direction is not transmitted, and a configuration using a polarizing plate having a length corresponding to the scanning range may be used.

According to an eighth aspect of the present invention, in place of the polarization beam splitter (7c) according to the sixth aspect, of the light returned to the linearly polarized light, reflected light linearly polarized in a predetermined direction is reflected. And a polarizing mirror having a length corresponding to the scanning range is used, and the light position detecting means (8) is provided with a polarized light. A configuration in which the light bent by the mirror is received may be employed.

The emitted light is converted into circularly polarized light having a predetermined rotation direction by the λ / 4 wavelength plate 3 and is irradiated on the measurement object 11. The reflected light of the measurement target 11 is returned to linearly polarized light by the λ / 4 wavelength plate 6, and then passes through the polarization beam splitter 7 and is incident on the light receiving surface of the light position detecting means 8. The light position detecting means 8 outputs a displacement signal corresponding to the amount of displacement of the measuring object 11 according to the light receiving position of the reflected light on the light receiving surface.
Even if the reflected light of the measurement target 11 is secondarily reflected by the neighboring measurement target 12 and reflected in the direction of the λ / 4 wavelength plate 6, the stray light component 33 is in a circularly polarized state having the opposite rotation direction, and the polarized beam The light does not pass through the splitter 7, is bent and does not enter the light position detecting means 8, and does not deteriorate the measurement accuracy.

[0015]

FIG. 1 is a schematic diagram showing a displacement measuring apparatus according to the present invention. The parts described in the related art are denoted by the same reference numerals. A collimator lens 2, a circularly polarizing means 3, and a light projecting lens 4 are provided on an optical axis of light emitted from a light source (laser) 1.
Is provided. An imaging lens 5, a linear polarizing means 6, a transmitting polarizing means 7, and a light position detecting means 8 are provided on an optical axis reflected from the measuring object 11. The emitted light and the reflected light have a predetermined angle θ. On these optical axes, the polarization direction of light is described.

The laser 1 emits light having a predetermined polarization component (linearly polarized light). The collimator lens 2 converts the emitted light into parallel light. As the circularly polarizing means 3, a λ / 4 wavelength plate for converting the light into circularly polarized light is used. The light projecting lens 4 forms a light spot on the measurement target 11 using the light.

The image forming lens 5 forms an image so that the reflected light from the measuring object 11 forms a light spot on the light position detecting means 8. As the linear polarization means 6, a λ / 4 wavelength plate for converting circularly polarized reflected light into linearly polarized light is used. This linear polarization means 6
The λ / 4 wavelength plate used in (1) has the same configuration as that of the circularly polarizing means 3 and is arranged so that the direction of setting the optical axis is different. Specifically, the circular polarization means 3 and the linear polarization means 6
In, the optical axis of the λ / 4 wavelength plate is changed by 90 °.

The transmission polarization means 7 is a polarization beam splitter that transmits only light of a predetermined polarization direction out of the linearly polarized reflected light and bends light of a different polarization direction (for example, light of a polarization direction different by 90 degrees). Is used. As the light position detecting means 8, a position sensor that outputs a detection signal according to the position of the light receiving surface that receives the reflected light is used.

According to the above configuration, the light emitted from the laser strikes the object to be measured 11 and forms a spot-like light spot at a predetermined position on the light receiving surface of the light position detecting means 8. This light spot becomes a position corresponding to the amount of displacement (for example, height) of the measurement target 11, and the light position detecting means 8 outputs a displacement signal corresponding to the position of this light spot.

The control means (not shown) calculates and outputs a displacement amount (for example, height) of the measuring object 11 based on the displacement signal of the light position detecting means 8. Further, by controlling the displacement measuring device to relatively move the measurement target 11 horizontally, the displacement amount of the measurement target 11 is continuously measured along the moving direction, and the surface shape and the shape of the measurement target 11 are measured. The cross-sectional shape can also be calculated.

For example, the measurement target 11 is a terminal of a semiconductor package such as an LSI, and the state (coplanarity) of the terminal can be measured. Thereby, B
Each height of a shiny metal surface (solder ball) such as GA,
It is possible to detect variations in the height of a plurality of solder balls, missing solder balls, and detection of extra solder balls.

At this time, the λ / 4 wavelength plate 3 is provided with the optical axis 3 of the radiation.
The light on 1 is circularly polarized and applied to the measurement object 11 with a predetermined rotation direction. Correspondingly, as for the optical axis 32 of the reflection from the measurement object 11, the circularly polarized light is incident on the λ / 4 wavelength plate 6 with the same rotation direction. The light is returned to linearly polarized light by the λ / 4 wavelength plate 6, passes through the polarization beam splitter 7 with the predetermined polarization angle, and reaches the light position detecting means 8.

Here, as shown in FIG.
It is arranged at a narrow pitch such as BGA, and 2
The case where the next reflection occurs will be described. In this case, similarly to the related art, light applied to the glossy spherical measurement object 11 is
In addition to the above-mentioned optical axis 32 of the reflection, it is assumed that the light is reflected in the direction of the nearby measurement target 12 (shown by a dotted line in the figure). The reflected light (referred to as stray light component 33) is reflected by the measurement object 12, travels in the same direction as the optical axis 32 of the reflection, and enters the polarization beam splitter 7.

The stray light component 33 is a reflection at the object 12 to be measured (that is, extra reflection for one time compared to normal time: secondary reflection), and the rotation direction of the circularly polarized light is different from the optical axis 32 of the reflection. The direction is reversed. Therefore, the λ / 4 wavelength plate 6 polarizes the stray light component 33 in a direction in which the polarization direction of the linearly polarized light is different. The polarization beam splitter 7 does not transmit the stray light component 33 having the different polarization direction but emits it in a bent angle direction (a direction orthogonal to the reflection optical axis 32 by 90 degrees). Thereby, it is possible to prevent the light of the stray light component 33 from being incident on the light position detecting means 8. It is desirable that the stray light component 33 be absorbed in the bending direction of the stray light component 33 in the polarizing beam splitter 7 by absorbing the stray light component 33 to prevent unnecessary reflection.

As described above, even if the measurement target 11 is arranged at a narrow pitch and has a shape that easily causes secondary reflection, the measurement error due to the secondary reflection does not occur, and the measurement accuracy is improved. Accuracy can be improved. Not only BGA but also secondary reflections such as measurement of IC lead bending, measurement of cream solder printed on lands formed at a narrow pitch on a printed wiring board and solder shape after reflow, etc. The same operation and effect can be obtained even when measuring a measurement object having an easy shape.

FIG. 2 is a diagram showing a modification of the configuration of the first embodiment. Instead of the polarizing beam splitter 7, a configuration using a polarizing plate 7a may be adopted. In the case of this configuration, the polarizing plate 7a transmits only the optical axis 32 of the reflection in the predetermined polarization direction returned to the linearly polarized light, and does not transmit the stray light component 33 having a different polarization direction.

FIG. 3 is a diagram showing a configuration in which a polarizing mirror 7b is used instead of the polarizing beam splitter 7 described above.
When this polarizing mirror 7b is used, the reflection optical axis 32,
Since the relationship between the transmission and bending of the stray light component 32 is opposite to that of the polarization beam splitter 7, the reflection optical axis 3
What is necessary is just to arrange the light position detection means 8 on the 2nd side.

In the displacement measuring device having the above-described structure, the displacement measuring device and the measuring object 11 are relatively moved (for example, the measuring object 1).
By moving the first side in the direction of arrow A in the figure), the displacement of the measurement target 11 is continuously measured along the moving direction. Next, the displacement measuring device shown in FIG. 4 is a second embodiment of the present invention, and has a scanning type configuration for scanning light emitted to the measurement target 11. The measurement object 11 is fixedly arranged.

On the optical axis 31 from the laser 1, the λ / 4 wavelength plate 3 and the deflecting means 22 are arranged. Deflection means 22
A rotating mirror type or a vibrating mirror type is used to deflect (scan) the optical axis in the direction of arrow B in the figure. The lens 23 irradiates the scanned light within a predetermined range (for example, 30 mm) so as to be parallel to the measurement target 11 in the same plane.

A lens array 25, a λ / 4 wavelength plate 6a, a polarizing beam splitter 7c, an imaging lens 26, and a light position detecting means 8 are provided on the optical axis 32 of the reflection from the measuring object 11. The lens array 25 has a length corresponding to the scanning width of the reflection optical axis 32, and emits parallel light to the λ / 4 wavelength plate 6a. As the λ / 4 wavelength plate 6a and the polarization beam splitter 7c, those having a length corresponding to the scanning width of the reflection optical axis 32 are used.

The polarization beam splitter 7 c transmits through the reflection optical axis 32 and exits to the imaging lens 26, and outputs a stray light component 33.
Is bent and emitted. As a result, the light receiving surface of the light position detecting means 8 is provided with the reflected optical axis 3 focused by the imaging lens 26.
Only two light spots are formed.

As described above, also in the scanning type displacement measuring device, the influence of the secondary reflection can be similarly prevented and the displacement can be measured with high accuracy. According to such an optical axis scanning type, displacement measurement can be performed at a higher speed than that of the first embodiment.

In the configuration of the second embodiment, a polarizing plate or a polarizing mirror having a length corresponding to the scanning width may be similarly used instead of the polarizing beam splitter 7c.

[0034]

According to the displacement measuring apparatus of the present invention, even if light reflected nearby due to the shape of the object to be measured is reflected on the side of the reflected optical axis, it can be removed without being incident on the light position detecting means. With this configuration, a narrow-pitch measurement target can be measured with high accuracy. The above effect is achieved by
A quarter-wave plate can be obtained with a simple configuration in which a ビ ー ム wavelength plate is provided on each of the emission and reflection optical axes and a polarization beam splitter is provided on the reflection optical axis side, and a change to another polarization element is also possible. Also, a scanning displacement measuring device that scans the optical axis can be simply configured by simply disposing a λ / 4 wavelength plate having a scanning width and a polarizing beam splitter in the same manner.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a first embodiment of a displacement measuring device according to the present invention.

FIG. 2 is a diagram showing a modification of the configuration of FIG. 1;

FIG. 3 is a diagram showing a modification of the configuration of FIG. 1;

FIG. 4 is a schematic diagram illustrating a scanning displacement measurement device according to a second embodiment.

FIG. 5 is a schematic diagram showing a conventional displacement measuring device.

[Explanation of symbols]

1: laser, 2: collimator lens, 3, 6, 6a: λ
/ 4 wavelength plate, 4 ... light projection lens, 5,26 ... imaging lens,
7, 7c: polarizing beam splitter, 7a: polarizing plate, 7b
... Polarizing mirror, 8 ... Light position detecting means, 11, 12 ... Measurement object, 22 ... Deflecting means, 23 ... Lens, 25 ... Lens array, 31 ... Irradiation optical axis, 32 ... Reflection optical axis, 33 ... Stray light component.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Kazuki Nagatsuka 5- 10-27 Minamiazabu, Minato-ku, Tokyo Anritsu Corporation (72) Inventor Eiji Tsujimura 5- 10-27 Minamiazabu, Minato-ku, Tokyo F-term in Anritsu Corporation (reference) 2F065 AA09 AA24 AA46 AA51 CC25 DD12 DD15 FF01 FF44 GG04 HH04 HH10 JJ16 KK01 LL10 LL13 LL32 LL36 LL37 LL62 MM03 MM16 2H042 AA04 AA09 AA21

Claims (8)

[Claims] 1. A displacement measuring apparatus for irradiating a measuring object with light and detecting a position of reflected light by an optical position detecting means to detect a displacement amount of the measuring object in a non-contact manner. A circularly polarizing means (3) for circularly polarizing in the direction of rotation and irradiating the object to be measured; a linearly polarizing means (6) for converting circularly polarized light reflected from the object to linearly polarized light; A transmission polarization means (7) for transmitting only reflected light, which is linearly polarized in a predetermined direction, of the light returned to linearly polarized light to the light position detection means. 2. A displacement measuring device for irradiating a measuring object with light, detecting a position of reflected light by an optical position detecting means and detecting a displacement amount of the measuring object in a non-contact manner, wherein light emitted from a light source is determined in a predetermined manner. A first λ / 4 wave plate (3) for making the object to be circularly polarized in the direction of rotation and irradiating the object to be measured, and a second λ / 4 wave plate to make circularly polarized light reflected from the object to be linearly polarized And (6) transmitting only reflected light that is linearly polarized in a predetermined direction among the light that has been returned to linearly polarized light by the second λ / 4 wavelength plate, and removes stray light components that are linearly polarized in other directions. A polarizing beam splitter (7) to be bent; and a light position detecting means (8) for receiving light transmitted through the polarizing beam splitter and outputting a displacement signal corresponding to a displacement amount of the object to be measured based on a light receiving position. A displacement measuring device, comprising: 3. The light beam returned to the linearly polarized light instead of the polarizing beam splitter (7) according to claim 2 transmits only reflected light that is linearly polarized in a predetermined direction and linearly polarized light in another direction. A displacement measuring device using a polarizing plate (7a) that does not transmit the stray light component. 4. The light beam returned to the linearly polarized light instead of the polarization beam splitter (7) according to claim 2, wherein the reflected light, which is linearly polarized in a predetermined direction, is bent in a predetermined direction and is bent in another direction. A displacement measuring device, wherein a polarizing mirror (7b) for transmitting a stray light component which is linearly polarized is used, and the optical position detecting means (8) receives light bent by the polarizing mirror. 5. A control means for moving the measurement target relative to the displacement measuring device and continuously measuring a displacement amount of the measurement target along the moving direction. 5. The displacement measuring device according to any one of claims 4 to 4. 6. A displacement for scanning and irradiating a measuring object with light, detecting a position of reflected light by a light position detecting means, and continuously detecting a displacement amount of the measuring object in a non-contact manner along the scanning direction. In the measuring device, a first λ / 4 wavelength plate (3) for circularly polarizing light emitted from a light source in a predetermined rotation direction and irradiating the object to be measured with the first λ / 4 wavelength plate (3) A deflecting means (22) for scanning the light after passing in a predetermined direction; and a second means for converting the circularly polarized light reflected from the measurement object into linearly polarized light and having a length corresponding to the scanning range. a λ / 4 wavelength plate (6a), and transmitting only reflected light that is linearly polarized in a predetermined direction out of the light returned to linearly polarized light by the second λ / 4 wavelength plate, and linearly polarized in another direction. This is to bend the stray light component, and has a length corresponding to the scanning range. A light beam splitter (7c); and a light position detecting means (8) for receiving light transmitted through the polarization beam splitter and outputting a displacement signal corresponding to a displacement amount of the measurement target based on a light receiving position. A displacement measuring device characterized by the above-mentioned. 7. Instead of the polarization beam splitter (7c) according to claim 6, only the reflected light linearly polarized in a predetermined direction among the light returned to the linearly polarized light is transmitted, and the linearly polarized light in the other direction. A displacement measuring device that does not transmit the stray light component and uses a polarizing plate having a length corresponding to the scanning range. 8. A light beam which has been linearly polarized in a predetermined direction among the light beams returned to the linearly polarized light instead of the polarization beam splitter (7c) according to claim 6, is bent in a predetermined direction, and is bent in another direction. A polarizing mirror having a length corresponding to the scanning range is used, and the light position detecting means (8) receives the light bent by the polarizing mirror. A displacement measuring device configured to