WO2016181578A1

WO2016181578A1 - Three-dimensional measurement device and three-dimensional measurement method

Info

Publication number: WO2016181578A1
Application number: PCT/JP2015/082486
Authority: WO
Inventors: 大山　剛; 憲彦坂井田; 二村　伊久雄
Original assignee: Ckd株式会社
Priority date: 2015-05-11
Filing date: 2015-11-19
Publication date: 2016-11-17
Also published as: JP6126640B2; JP2016211986A; TWI580927B; CN107429992B; TW201640076A; CN107429992A

Abstract

Provided are a three-dimensional measurement device and three-dimensional measurement method capable of reducing measurement time for height measurement using a phase shift method. A substrate inspection device 1 is provided with an illumination device 4 for irradiating a prescribed optical pattern from a diagonally upward position onto the surface of a printed circuit board 2, a camera 5 for imaging a portion of the printed circuit board 2 irradiated with the optical pattern, and a control device 6 for carrying out various control, image processing, and calculation within the substrate inspection device 1. The control device 6 uses the relationship between the gain and offset of an optical pattern determined by prescribed imaging conditions and a gain or offset value of the optical pattern that is for coordinates to be measured on image data and is determined from brightness values at the coordinates to be measured to measure the height of the coordinates to be measured using a phase shift method on the basis of two sets of image data imaged under optical patterns with two shifted phases.

Description

Three-dimensional measuring apparatus and three-dimensional measuring method

The present invention relates to a three-dimensional measurement apparatus and a three-dimensional measurement method that perform height measurement using a phase shift method.

Generally, when an electronic component is mounted on a printed circuit board, cream solder is first printed on a predetermined electrode pattern disposed on the printed circuit board. Next, the electronic component is temporarily fixed on the printed circuit board based on the viscosity of the cream solder. Thereafter, the printed circuit board is guided to a reflow furnace, and soldering is performed through a predetermined reflow process. In recent years, it is necessary to inspect the printed state of cream solder in the previous stage of being guided to a reflow furnace, and a three-dimensional measuring device is sometimes used for such inspection.

In recent years, various so-called non-contact type three-dimensional measuring apparatuses using light have been proposed. For example, a technique relating to a three-dimensional measuring apparatus using a phase shift method has been proposed.

In the three-dimensional measuring device using the phase shift method, a combination of a light source that emits predetermined light and a grating that converts light from the light source into a light pattern having a sinusoidal (stripe) light intensity distribution. The object to be measured (in this case, the printed circuit board) is irradiated by the irradiation means. And it observes using the imaging means which has arrange | positioned the point on a board | substrate directly above. As the imaging means, a CCD camera or the like including a lens and an imaging element is used.

With the above configuration, the light intensity (luminance) I of each pixel on the image data picked up by the image pickup means is given by the following equation (T1).

I = f · sinφ + e (T1)
Where f: gain, e: offset, φ: sine wave phase angle at the pixel.

Here, by switching and controlling the grating, the phase of the light pattern is changed in, for example, four stages (φ + 0, φ + 90 °, φ + 180 °, φ + 270 °), and intensity distributions I ₀ , I ₁ , I ₂ corresponding thereto. , I ₃ is taken in, f (gain) and e (offset) are canceled based on the following equation (T2), and the phase angle φ is obtained.

φ = arctan {(I ₁ −I ₃ ) / (I ₂ −I ₀ )} (T2)
Then, using this phase angle φ, the height (Z) at the measured coordinates (X, Y) on the printed circuit board (cream solder) is calculated based on the principle of triangulation (see, for example, Patent Document 1). ).

For example, when the height (Z) at the measured coordinates (X, Y) is “0”, the phase angle φ of the pattern light applied to the coordinates (X, Y) is “0 °”, which is a predetermined height. The phase angle φ related to the coordinates (X, Y) varies depending on the height, such that the phase angle φ becomes “10 °” when it has a height.

On the other hand, in recent years, a technique has been proposed in which the phase of the light pattern is changed in three stages and the phase angle φ is acquired from three types of image data (see, for example, Patent Document 2).

Japanese Patent Laid-Open No. 5-280945 JP 2002-81924 A

However, in the conventional three-dimensional measuring apparatus, it is necessary to change the phase into four or three stages and to capture four or three kinds of images having intensity distributions corresponding to these. That is, since it is necessary to perform imaging four times or three times with respect to one point, it takes time for imaging and there is a possibility that measurement time becomes long. Therefore, further reduction in measurement time has been demanded.

Note that the above-mentioned problem is not necessarily limited to the height measurement of cream solder or the like printed on a printed circuit board, but is inherent in the field of other three-dimensional measurement devices.

The present invention has been made in view of the above circumstances, and its purpose is to provide a three-dimensional measurement apparatus and a three-dimensional measurement apparatus that can shorten the measurement time when performing height measurement using the phase shift method. It is to provide a measurement method.

Hereafter, each means suitable for solving the above-mentioned problems will be described in terms of items. In addition, the effect specific to the means to respond | corresponds as needed is added.

Means 1. A light source that emits predetermined light, and a grating that converts the light from the light source into a light pattern having a striped light intensity distribution, and an irradiation unit that can irradiate at least the object to be measured with the light pattern;
Phase control means for controlling the transfer or switching of the grating and capable of changing the phase of the light pattern irradiated from the irradiation means in a plurality of ways;
Imaging means capable of imaging reflected light from the object to be measured irradiated with the light pattern;
Image processing means capable of performing three-dimensional measurement of the object to be measured based on image data picked up by the image pickup means;
The image processing means includes
The relationship between the gain and offset of the light pattern determined by predetermined imaging conditions;
By using the gain or offset value of the light pattern related to the measured coordinates determined from the luminance value of the measured coordinates on the image data,
A three-dimensional measuring apparatus characterized in that height measurement of the measured coordinates can be performed by a phase shift method based on two kinds of image data picked up under the light pattern whose phase is changed in two ways.

According to the means 1, the relationship between the gain A and the offset B of the light pattern determined by the predetermined imaging condition [for example, A = K (proportional constant) × B] and the measured coordinates (x, y) on the image data. By using the value of the gain A (x, y) or the offset B (x, y) of the light pattern related to the measured coordinate (x, y) determined from the luminance value V (x, y), 2 The height of the coordinate to be measured can be measured by the phase shift method based on the two types of image data captured under the light pattern whose phase is changed in the way.

As described above, this means can measure the height of an object to be measured based on two kinds of image data, and therefore, compared with the conventional technique that requires four or three imaging operations for one point. The total number of times of imaging can be reduced, and the imaging time can be shortened. As a result, the measurement time can be dramatically shortened.

The light emitted from the light source is first attenuated when passing through the grating, then attenuated when reflected by the object to be measured, and finally A / D converted (analog-digital converted) by the imaging means. Is obtained as the luminance value of each pixel of the image data.

Therefore, the luminance value of each pixel of the image data imaged by the imaging means is the brightness of the light source, the attenuation rate when the light emitted from the light source passes through the grid, and the light when the light is reflected by the object to be measured. This can be expressed by multiplying the reflectance and the conversion efficiency when A / D conversion (analog-digital conversion) is performed in the imaging means.

For example, the brightness of the light source (uniform light): L
Transmittance of lattice: G = αsinθ + β
α and β are arbitrary constants.

Reflectance at coordinates (x, y) on the measurement object: R (x, y)
Conversion efficiency of each pixel of the imaging means (imaging device): E
The luminance value of the pixel on the image corresponding to the coordinate (x, y) on the object to be measured: V (x, y)
Gain of light pattern at coordinates (x, y) on the measurement object: A (x, y)
Offset of light pattern at coordinates (x, y) on the measurement object: B (x, y)
In this case, it can be expressed by the following formula (F1).

Here, the gain A (x, y) is a luminance value V (x, y) _MAX by the light of “sin θ = 1”, and a luminance value V (x, y) _MIN by the light of “sin θ = −1”. Can be expressed from the difference between
For example, transmittance when the grating is θ = 0 (= average transmittance): Gθ _{= 0}
Transmittance when the grating is θ = π / 2 (= maximum transmittance): Gθ ₌ π _{/ 2}
Transmittance when the grating is θ = −π / 2 (= minimum transmittance): Gθ ₌ −π _{/ 2}
In this case, it can be expressed by the following formula (F2).

The offset B (x, y) is the luminance value V (x, y) in the light of “sin θ = 0”, and the luminance value V (x, y) _{MAX in} the light of “sin θ = 1” Since it is an average value with the luminance value V (x, y) _MIN due to the light of “sin θ = −1”, it can be expressed by the following formula (F3).

That is, the maximum value V (x, y) _MAX , the minimum value V (x, y) _MIN , and the average value V (x, y) _AV of the luminance value are expressed by the following equations (F4), (F5), and (F6), respectively. The relationship is as shown in the graph of FIG.

As can be seen from FIG. 3, the average value V (x, y) of the maximum value V (x, y) _MAX of the luminance value and the minimum value V (x, y) _MIN of the luminance value at a predetermined coordinate (x, y). y) _AV becomes an offset B (x, y), the difference between the offset B (x, y) and the maximum value V (x, y) _MAX , and the offset B (x, y) and the minimum value V ( x, y) The difference from _MIN is the gain A (x, y).

Further, since the luminance value V (x, y) changes in proportion to the brightness L or the reflectance R (x, y) of the light source, for example, at the coordinate position where the reflectance R is halved, the gain A and the offset The value of B is also halved.

Next, after formulating the above formulas (F2) and (F3) into the following formulas (F2 ′) and (F3 ′) and arranging them together, the following formula (F7) can be derived.

Furthermore, when the above equation (F7) is solved for A (x, y), the following equation (F8) is obtained, which can be represented as the graph shown in FIG.

That is, when one of the brightness L or the reflectance R (x, y) of the light source is fixed and the other is changed, the offset B (x, y) increases and decreases and the offset B (x, y) ), The gain A (x, y) also increases / decreases. If one of the gain A and the offset B is known from the equation (F8), the other can be obtained. Here, the proportionality constant K is determined by the transmittance G of the grating irrespective of the brightness L and the reflectance R of the light source. That is, the following

means

2 and 3 can be used in other words.

Means 2. The three-dimensional measuring apparatus according to claim 1, wherein the relationship between the gain and the offset is a relationship in which the gain and the offset are uniquely determined.

If the relationship between the gain A and the offset B is uniquely determined, for example, by creating a numerical table or table data representing the relationship between the gain A and the offset B, the offset B from the gain A or the offset The gain A can be obtained from B.

Means 3. The three-dimensional measuring apparatus according to claim 1, wherein the gain and the offset are proportional to each other.

If the gain and the offset are in a proportional relationship, for example, it can be expressed by a relational expression such as A = K × B + C [where C is the dark current (offset) of the camera]. The gain A can be obtained from B. As a result, it can be set as the following means 4.

Means 4. When the luminance value of each pixel of the two types of image data when the relative phase relationship of the light pattern having the two phase changes is set to 0 and γ, respectively, is V ₀ and V ₁ ,
The image processing means includes
The three-dimensional measuring apparatus according to means 1, wherein a phase angle θ satisfying a relationship of the following formulas (1), (2), and (3) is obtained, and the height measurement is performed based on the phase angle θ.

V ₀ = Asinθ + B (1)
V ₁ = Asin (θ + γ) + B (2)
A = KB (3)
However, γ ≠ 0, A: gain, B: offset, K: proportional constant.

According to the above means 4, the following formula (4) can be derived by substituting the above formula (3) into the above formula (1).

V ₀ = KBsinθ + B (4)
When this is solved for the offset B, the following equation (5) can be derived.

B = V ₀ / (Ksinθ + 1) (5)
Further, the following formula (6) can be derived by substituting the above formula (3) into the above formula (2).

V ₁ = KBsin (θ + γ) + B (6)
By substituting the above equation (6) into the above equation (5) and rearranging as shown in the following [Equation 7], the following equation (7) can be derived.

Here, when “V ₀ cos γ−V ₁ = a”, “V ₀ sin γ = b”, and “(V ₀ −V ₁ ) / K = c” are set, the above equation (7) becomes the following equation (8): It can be expressed as

asinθ + bcosθ + c = 0 (8)
Here, as shown in the following [Equation 8], when the above equation (8) is solved for the phase angle θ, the following equation (9) shown in the following [Equation 9] can be derived.

Therefore, “to obtain a phase angle θ satisfying the relationship of the following formulas (1), (2), (3) in the above means 4 and perform the height measurement based on the phase angle θ” means “ In other words, the phase angle θ is obtained based on the following formula (9), and the height measurement is performed based on the phase angle θ. Of course, the algorithm for obtaining the phase angle θ is not limited to the above equation (9), and any other configuration may be adopted as long as the relationship of the above equations (1), (2), and (3) is satisfied. May be.

In addition, if the dark current C of the camera mentioned above is taken into consideration, the measurement accuracy can be further improved.

Means 5. The three-dimensional measuring apparatus according to means 4, wherein γ = 180 °.

According to the means 5, the image is taken twice under two light patterns whose phases are different by 180 °.

The following equation (10) is derived by setting γ = 180 ° in the above equation (2).

V ₁ = Asin (θ + 180 °) + B
= -Asinθ + B (10)
Then, the following formula (11) can be derived from the above formulas (1) and (10). When this is solved for the offset B, the following formula (12) can be derived.

V ₀ + V ₁ = 2B (11)
B = (V ₀ + V ₁ ) / 2 (12)
Furthermore, the following formula (13) can be derived by substituting the above formula (12) into the above formula (3).

A = KB
= K (V ₀ + V ₁ ) / 2 (13)
Further, when the above equation (1) is arranged for “sin θ”, the following equation (1 ′) is obtained.

sinθ = (V ₀ −B) / A (1 ′)
Then, the following formula (14) can be derived by substituting the above formulas (12) and (13) into the above formula (1 ′).

sin θ = {V ₀ − (V ₀ + V ₁ ) / 2} / {K (V ₀ + V ₁ ) / 2}
= (V ₀ -V ₁ ) / K (V ₀ + V ₁ ) (14)
Here, when the above equation (14) is solved for the phase angle θ, the following equation (15) can be derived.

θ = sin ⁻¹ [(V ₀ −V ₁ ) / K (V ₀ + V ₁ )] (15)
That is, the phase angle θ can be specified by the known luminance values V ₀ and V ₁ and the constant K.

As described above, according to the means 5, the phase angle θ can be obtained based on a relatively simple arithmetic expression, and the processing speed can be further increased when the height of the object to be measured is measured.

Means 6. The three-dimensional measuring apparatus according to means 4, wherein γ = 90 °.

According to the above means 6, two images are taken under two light patterns whose phases are different by 90 °.

The following equation (16) is derived by setting γ = 90 ° in the above equation (2).

V ₁ = Asin (θ + 90 °) + B
= Acosθ + B (16)
When the above equation (16) is arranged for “cos θ”, the following equation (17) is obtained.

cos θ = (V ₁ −B) / A (17)
Further, when the above equation (1) is arranged with respect to “sin θ”, as described above, the following equation (1 ′) is obtained.

sinθ = (V ₀ −B) / A (1 ′)
Next, when the above formulas (1 ′) and (17) are substituted into the following formula (18), the following formula (19) is obtained. Further, by arranging this, the following formula (20) is derived.

sin ² θ + cos ² θ = 1 (18)
{(V ₀ −B) / A} ² + {(V ₁ −B) / A} ² = 1 (19)
(V ₀ −B) ² + (V ₁ −B) ² = A ² (20)
Then, when the above equation (3) is substituted into the above equation (20), the following equation (21) is obtained, and by further arranging this, the following equation (22) is derived.

(V ₀ -B) ² + (V ₁ -B) ² = K ² B ² (21)
(2-K ² ) B ² -2 (V ₀ + V ₁ ) B + V ₀ ² V ₁ ² = 0 (22)
Here, when the above equation (22) is solved for the offset B, the following equation (23) can be derived.

That is, the offset B can be specified by the known luminance values V ₀ and V ₁ and the constant K.

Further, when the above formulas (1 ′) and (17) are substituted into the following formula (24), the following formula (25) is obtained, and by further arranging this, the following formula (26) is derived.

tanθ = sinθ / cosθ (24)
= {(V ₀ -B) / A} / {(V ₁ -B) / A} (25)
= (V ₀ -B) / (V ₁ -B) (26)
Then, when the above equation (26) is solved for the phase angle θ, the following equation (27) can be derived.

θ = tan ⁻¹ {(V ₀ −B) / (V ₁ −B)} (27)
That is, the phase angle θ can be specified by the known luminance values V ₀ and V ₁ and the constant K by using the above equation (23).

As described above, according to the means 6, the phase angle θ can be obtained based on the arithmetic expression using “tan ⁻¹ ”, so that the height can be measured in the range of 360 ° from −180 ° to 180 °. Thus, the measurement range can be further increased.

Means 7. The three-dimensional measuring apparatus according to any one of means 1 to 6, further comprising storage means for storing the relationship between the gain and offset of the light pattern calculated from a calibration or a separately performed measurement result in advance.

For example, the reference plate is irradiated with light patterns whose phases are changed in three or four ways, and the gain A and the offset B in each pixel are specified based on the three or four kinds of image data captured under these patterns. A constant K is determined from Equation (3). Thereby, according to the said means 7, more accurate height measurement can be performed in each pixel.

Means 8. 7. The method according to claim 1, wherein the relationship between the gain and offset of the light pattern is obtained based on two types of image data captured under the light pattern whose phase has been changed in the two ways. 3D measuring device.

For example, the offset B is obtained for all the pixels of the image data using the above equation (12) and the like, the luminance value V of the pixel having the same value of the offset B is extracted, and the histogram is created. Then, the maximum value V _MAX and the minimum value V _MIN of the luminance value are determined from the histogram.

As described above, the average value of the maximum value V _MAX and the minimum value V _MIN of the luminance value is the offset B, and the half of the difference between the maximum value V _MAX and the minimum value V _MIN is the gain A. Based on this, the constant K can be determined from the above equation (3). Thereby, according to the means 8, the labor of calibration as in the means 7 can be omitted, and the measurement time can be further shortened.

Means 9. A light source that emits predetermined light, and a grating that converts the light from the light source into a light pattern having a striped light intensity distribution, and an irradiation unit that can irradiate at least the object to be measured with the light pattern;
Phase control means for controlling the transfer or switching of the grating and capable of changing the phase of the light pattern irradiated from the irradiation means in a plurality of ways;
A three-dimensional measurement method performed by a three-dimensional measurement apparatus including an imaging unit capable of imaging reflected light from the measurement object irradiated with the light pattern,
A relationship acquisition step of obtaining a relationship between gain and offset of the light pattern determined by a predetermined imaging condition based on a measurement result obtained by calibration or separately;
An image acquisition step of acquiring two types of image data imaged under the light pattern that has undergone two phase changes;
Using the relationship between the gain and offset of the light pattern obtained in the relationship acquisition step and the gain or offset value of the light pattern related to the measured coordinate determined from the luminance value of the measured coordinate on the image data. And a measuring step of measuring the height of the measured coordinates by a phase shift method based on the two types of image data.

According to the means 9, the same effects as the means 1 and means 7 can be obtained.

It is a schematic block diagram which shows a board | substrate inspection apparatus typically. It is a block diagram which shows the electric constitution of a board | substrate inspection apparatus. It is a graph which shows the relationship between the brightness or reflectance of a light source, and a luminance value. It is a graph which shows the relationship between a gain and an offset. It is a distribution table showing the distribution of the number of luminance values included in each data section. It is the histogram showing distribution of the number of the luminance values contained in each data section.

[First Embodiment]
Hereinafter, an embodiment will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram schematically illustrating a substrate inspection apparatus 1 including a three-dimensional measurement apparatus according to the present embodiment. As shown in FIG. 1, the substrate inspection apparatus 1 includes a mounting table 3 for mounting a printed circuit board 2 as an object to be measured on which cream solder as a measurement target is printed, and a surface that is oblique to the surface of the printed circuit board 2. An illumination device 4 as an irradiating unit that irradiates a predetermined light pattern from above, a camera 5 as an imaging unit for imaging a portion irradiated with the light pattern on the printed circuit board 2, and various types in the substrate inspection apparatus 1 And a control device 6 for performing control, image processing, and arithmetic processing.

The mounting table 3 is provided with

motors

15 and 16, and the

motors

15 and 16 are driven and controlled by the control device 6 (motor control means 23), whereby the printed circuit board mounted on the mounting table 3. 2 can be slid in any direction (X-axis direction and Y-axis direction).

The illumination device 4 includes a light source 4a that emits predetermined light, and a liquid crystal lattice 4b that converts light from the light source 4a into a light pattern having a sinusoidal (stripe) light intensity distribution. On the other hand, it is possible to irradiate a striped light pattern whose phase changes in a plurality of ways from obliquely above.

More specifically, in the illuminating device 4, the light emitted from the light source 4a is guided to a pair of condensing lenses by an optical fiber, and is converted into parallel light there. The parallel light is guided to the projection lens through the liquid crystal grating 4b. Then, a striped light pattern is irradiated onto the printed circuit board 2 from the projection lens.

The liquid crystal lattice 4b includes a liquid crystal layer formed between a pair of transparent substrates, a common electrode disposed on one transparent substrate, and a plurality of strips arranged in parallel on the other transparent substrate so as to face the common electrode. By switching on and off the switching elements (thin film transistors, etc.) connected to each strip electrode by a drive circuit, and controlling the voltage applied to each strip electrode, the “bright portion with high light transmittance” is provided. ”And a“ dark part ”having a low light transmittance is formed. And the light irradiated on the printed circuit board 2 via the liquid crystal grating 4b becomes a light pattern having a sinusoidal light intensity distribution due to blur caused by diffraction action or the like.

The camera 5 includes a lens, an image sensor, and the like. A CMOS sensor is used as the image sensor. Of course, the imaging device is not limited to this, and a CCD sensor or the like may be employed, for example. Image data captured by the camera 5 is converted into a digital signal inside the camera 5 and then input to the control device 6 (image data storage means 24) in the form of a digital signal. Then, the control device 6 performs image processing, inspection processing, and the like, which will be described later, based on the image data. In this sense, the control device 6 constitutes image processing means.

Next, the electrical configuration of the control device 6 will be described. As shown in FIG. 2, the control device 6 includes a camera control unit 21 that controls the imaging timing of the camera 5, an illumination control unit 22 that controls the illumination device 4, and a motor control unit 23 that controls the

motors

15 and 16. Image data storage means 24 for storing image data (luminance data) captured by the camera 5, calibration data storage means 25 for storing calibration data described later, and phase data calculated based on the image data The phase data storage means 26 for storing information, the three-dimensional measurement means 29 for performing three-dimensional measurement based on the calibration data and the phase data, and the printing state of the cream solder 4 based on the measurement result of the three-dimensional measurement means 29 And a determination means 30 for inspecting. The phase control means in this embodiment is constituted by the illumination control means 22 that controls the illumination device 4 (liquid crystal grating 4b).

Although not shown in the drawings, the substrate inspection apparatus 1 includes an input unit composed of a keyboard and a touch panel, a display unit having a display screen such as a CRT or a liquid crystal, a storage unit for storing inspection results, and a solder printing machine. Output means for outputting inspection results and the like.

Next, the inspection procedure of the printed circuit board 2 by the substrate inspection apparatus 1 will be described in detail. First, calibration is performed to grasp the variation (phase distribution) of the light pattern.

In the liquid crystal lattice 4b, due to variations in characteristics (offset, gain, etc.) of the transistors connected to the strip electrodes, the voltages applied to the strip electrodes also vary. ", The light transmittance (luminance level) varies for each line corresponding to each strip electrode. As a result, the light pattern irradiated onto the object to be measured does not have a sinusoidal ideal light intensity distribution, and an error may occur in the three-dimensional measurement result.

Therefore, so-called calibration or the like is performed to grasp the variation (phase distribution) of the light pattern in advance.

As a calibration procedure, first, separately from the printed board 2, a height reference plane 0 and a flat reference plane are prepared. The reference surface has the same color as the cream solder to be measured. That is, the reflectances of the cream solder and the light pattern are equal.

Subsequently, the light pattern is irradiated onto the reference plane, and this is imaged by the camera 5 to obtain image data including the luminance value of each coordinate. In the present embodiment, unlike the actual measurement described later, when performing calibration, the phase of the light pattern is shifted by 90 °, and four types of image data captured under each light pattern are acquired.

Then, the control device 6 calculates the phase angle θ of the light pattern at each coordinate from the above four types of image data, and stores this in the calibration data storage means 25 as calibration data.

Furthermore, in this embodiment, the gain A and the offset B of the light pattern at each coordinate and the relationship between both are specified from the above four types of image data, and these are stored in the calibration data storage means 25 as calibration data. Therefore, the calibration data storage means 25 constitutes the storage means in the present embodiment, and this process constitutes the relationship acquisition process in the present embodiment.

Here, the procedure for calculating the gain A and the offset B will be described in more detail. The relationship between the luminance values (V ₀ , V ₁ , V ₂ , V ₃ ) at each coordinate of the four types of image data, the gain A, and the offset B is expressed by the following equations (H1), (H2), (H3), It can be represented by (H4).

Then, the luminance values (V ₀ , V ₁ , V ₂ , V ₃ ) of the four kinds of image data are added, and the above equations (H1), (H2), (H3), and (H4) are expressed by the following [Equation 12]. The following formula (H5) can be derived by arranging as shown in FIG.

Moreover, the following formula (H6) can be derived from the above formulas (H1) and (H3).

Further, the following formula (H7) can be derived from the above formulas (H2) and (H4).

Then, as shown in [Equation 15] below, when the above formulas (H6) and (H7) are substituted into the following formula (H8) and rearranged, the following formula (H9) can be derived.

Further, the proportional constant K of the gain A and the offset B is calculated based on the following formula (H10) derived from the above formulas (H5) and (H9).

Then, the gain A, the offset B, and the proportionality constant K of the light pattern at each coordinate calculated as described above are stored in the calibration data storage unit 25 as calibration data. Of course, only the proportionality constant K may be stored as calibration data.

Next, the inspection routine performed for each inspection area will be described in detail. This inspection routine is executed by the control device 6.

The control device 6 (motor control means 23) first drives and controls the

motors

15 and 16 to move the printed circuit board 2, and adjusts the field of view of the camera 5 to a predetermined inspection area (measurement range) on the printed circuit board 2. The inspection area is one area in which the surface of the printed circuit board 2 is divided in advance with the size of the field of view of the camera 5 as one unit.

Subsequently, the control device 6 switches and controls the liquid crystal lattice 4b of the illumination device 4, and sets the position of the lattice formed in the liquid crystal lattice 4b to a predetermined reference position.

When the switching setting of the liquid crystal lattice 4b is completed, the control device 6 causes the light control unit 22 to emit the light source 4a of the lighting device 4, starts the irradiation of a predetermined light pattern, and drives the camera 5 by the camera control unit 21. Control is performed to start imaging of the inspection area portion irradiated with the light pattern. The image data captured by the camera 5 is transferred to and stored in the image data storage device 24.

Similarly, the above-described series of processing is performed under a light pattern in which the phase of the light pattern is shifted by 180 °, for example. Thereby, two kinds of image data captured under two kinds of light patterns whose phases are shifted by 180 ° are obtained for a predetermined inspection area. This process constitutes an image acquisition process in the present embodiment.

Then, the control device 6 calculates the phase angle θ of the light pattern at each coordinate from the two types of image data by the phase shift method, and stores this in the phase data storage means 26 as phase data. Specifically, based on the above equation (15), the luminance values V ₀ and V _{1 at} the respective coordinates on the two types of image data, and the calibration data (based on the calibration) stored in the calibration data storage unit 25. The phase angle θ of the light pattern at each coordinate is calculated in consideration of the proportional constant K) of each coordinate.

Subsequently, the control device 6 (three-dimensional measuring unit 29) has the calibration data (phase angle of each coordinate based on calibration) stored in the calibration data storage unit 25 and the phase data stored in the phase data storage unit 26. Compared with (phase angle of each coordinate based on actual measurement), a shift amount of coordinates having the same phase angle is calculated, and height data at each coordinate of the inspection area is acquired based on the principle of triangulation. Such a process constitutes a measurement process in the present embodiment.

For example, when the actually measured value (phase angle) at the measured coordinates (x, y) is “10 °”, the position on the data stored by the calibration is the value of “10 °”. To detect. Here, if “10 °” exists 3 pixels adjacent to the measured coordinates (x, y), it means that the stripe of the light pattern has shifted by 3 pixels. Based on the principle of triangulation, the height data (z) of the measured coordinates (x, y) can be obtained based on the irradiation angle of the light pattern and the amount of deviation of the stripe of the light pattern.

Furthermore, the control device 6 (three-dimensional measuring means 29) detects the printing range of the cream solder that is higher than the reference plane based on the obtained height data at each coordinate of the inspection area, and within this range. The amount of printed cream solder is calculated by integrating the height of each part.

Then, the control device 6 (determination means 30) compares and determines the data such as the position, area, height, or amount of the cream solder thus obtained with reference data stored in advance, and the comparison result is within an allowable range. Whether the printing state of the cream solder in the inspection area is good or not is determined depending on whether it is in the inspection area.

While such processing is being performed, the control device 6 drives and controls the

motors

15 and 16 to move the printed circuit board 2 to the next inspection area. Thereafter, the above series of processing is performed in all inspection areas. By being repeatedly performed, the inspection of the entire printed circuit board 2 is completed.

As described above in detail, according to the present embodiment, the relationship between the gain A and the offset B of the light pattern determined by predetermined imaging conditions [for example, A = K (proportional constant) × B] and the measurement target on the image data The value of the gain A (x, y) or offset B (x, y) of the light pattern related to the measured coordinates (x, y) determined from the luminance value V (x, y) of the coordinates (x, y) By using, the height of the measured coordinate can be measured by the phase shift method based on the two types of image data captured under the light pattern whose phase is changed in two ways.

As described above, since the height can be measured based on the two types of image data, the total number of times of imaging is less than that of the conventional technique that requires four or three times of imaging for one point. The imaging time can be shortened. As a result, the measurement time can be dramatically shortened.

[Second Embodiment]
Hereinafter, the second embodiment will be described with reference to the drawings. In addition, about the same component as 1st Embodiment, the same code | symbol is attached | subjected and the detailed description is abbreviate | omitted.

In the first embodiment, the relationship between the gain A and the offset B (proportional constant K) of the light pattern at each coordinate is obtained in advance by calibration. Instead, in the second embodiment, The relationship (proportional constant K) between the gain A and the offset B of the light pattern is obtained on the basis of the two types of image data imaged under the light pattern that has been phase-shifted in the two ways imaged at the time of actual measurement. .

As the procedure, first, the offset B is obtained for all the pixels of the image data using the above equation (12). Next, the luminance value V (= Asin θ + B) of the pixels having the same offset B value is extracted, and a histogram thereof is created. An example is shown in the tables of FIGS. 5 and 6 exemplify a case where the gain A is “1” and the offset B is “0”. FIG. 5 is a distribution table in which the luminance value V is divided into data sections having a width of “0.1” and the number of luminance values included in the data section is represented. FIG. 6 is a histogram in which the luminance values are plotted. .

Based on this histogram, the maximum value V _MAX and the minimum value V _MIN of the luminance value are determined. By using the characteristic of “sin θ”, two peaks generated in the histogram can be determined as the maximum value V _MAX and the minimum value V _MIN of the luminance values, respectively. In the example shown in FIGS. 5 and 6, the number of luminance values V that fall within the data section with luminance values V of “−1.0 to −0.9” and “0.9 to 1.0” is “51”, respectively. Here are two peaks.

Subsequently, the gain A and the offset B are calculated based on the maximum value V _MAX and the minimum value V _MIN of the luminance values. As described above, the average value of the maximum value V _MAX and the minimum value V _MIN of the luminance value is the offset B, and the half of the difference between the maximum value V _MAX and the minimum value V _MIN is the gain A. That is, as shown in FIG. 6, the intermediate value between the two peaks is offset B, and half of the width of the two peaks is gain A.

The proportionality constant K can be determined based on the gain A and the offset B obtained in this way [see the above formula (3)].
According to this embodiment, the labor of calibration as in the first embodiment can be omitted, and the measurement time can be further shortened.

In addition, it is not limited to the description content of the said embodiment, For example, you may implement as follows. Of course, other application examples and modification examples not illustrated below are also possible.

(A) In the above embodiment, the three-dimensional measuring device is embodied as the substrate inspection device 1 that measures the height of the cream solder printed and formed on the printed circuit board 2. You may embody the structure which measures the height of other things, such as the solder bump made and the electronic component mounted on the board | substrate.

(B) In the above embodiment, the grating for converting the light from the light source 4a into a striped light pattern is constituted by the liquid crystal grating 4b, and the phase of the light pattern is shifted by switching this. It has a configuration. For example, the grating member may be transferred by a transfer unit such as a piezo actuator to shift the phase of the light pattern.

(C) In the above-described embodiment, the height measurement is performed based on two types of image data captured under two types of light patterns whose phases are different by 180 ° in actual measurement. Instead of this, for example, the height may be measured based on two kinds of image data captured under two kinds of light patterns whose phases are different by 90 °. In such a case, by using the above formulas (23) and (27), the light values at the respective coordinates are obtained using the luminance values V ₀ and V _{1 at} the respective coordinates on the two kinds of image data and the known proportionality constant K. The phase angle θ of the pattern can be calculated.

Of course, in addition to this, other configurations may be adopted as long as the relations of the above formulas (1), (2), and (3) are satisfied. As a general formula for obtaining the phase angle θ, the above formula (9) is given as an example [see [Equation 9]].

(D) In the first embodiment, the calibration is performed based on the four types of image data captured under the four types of light patterns whose phases are different by 90 °. For example, calibration may be performed based on three types of image data captured under three types of light patterns having different phases.

Also, when performing calibration, a configuration may be adopted in which the luminance of the light source is changed and the calibration is performed a plurality of times. With this configuration, the dark current (offset) C of the camera 5 as shown in the following formula (28) can be obtained.

A = KB + C (28)
However, A: Gain, B: Offset, C: Dark current (offset) of the camera, K: Proportional constant.

Alternatively, the relationship between the gain A and the offset B is not obtained as an equation, but by creating a numerical table or table data that represents the relationship between the gain A and the offset B, the gain A can be gained from the offset B or the offset B. You may comprise so that A can be calculated | required. Furthermore, the relationship between the gain A and the offset B may be obtained using a measurement result or the like separately performed instead of the calibration.

(E) In the second embodiment described above, the proportionality constant K and the like are obtained for all the pixels of the image data based on the two types of image data captured under two types of light patterns that are 180 degrees out of phase. ing.

However, the present invention is not limited to this. For example, the proportional constant K or the like may be obtained based on two types of image data captured under two types of light patterns whose phases are different by 90 °. Further, the proportional constant K or the like may be obtained not in all pixels of the image data but in a part of the image data such as the periphery of the measured coordinates.

DESCRIPTION OF SYMBOLS 1 ... Board | substrate inspection apparatus, 2 ... Printed circuit board, 4 ... Illuminating device, 4a ... Light source, 4b ... Liquid crystal lattice, 5 ... Camera, 6 ... Control apparatus, 24 ... Image data storage means, 25 ... Calibration data storage means, 26 ... phase data storage means, V ₀ , V ₁ , V ₂ , V ₃ ... luminance value, A ... gain, B ... offset, K ... proportional constant.

Claims

A light source that emits predetermined light, and a grating that converts the light from the light source into a light pattern having a striped light intensity distribution, and an irradiation unit that can irradiate at least the object to be measured with the light pattern;
Phase control means for controlling the transfer or switching of the grating and capable of changing the phase of the light pattern irradiated from the irradiation means in a plurality of ways;
Imaging means capable of imaging reflected light from the object to be measured irradiated with the light pattern;
Image processing means capable of performing three-dimensional measurement of the object to be measured based on image data picked up by the image pickup means;
The image processing means includes
The relationship between the gain and offset of the light pattern determined by predetermined imaging conditions;
By using the gain or offset value of the light pattern related to the measured coordinates determined from the luminance value of the measured coordinates on the image data,
A three-dimensional measuring apparatus characterized in that height measurement of the measured coordinates can be performed by a phase shift method based on two kinds of image data picked up under the light pattern whose phase is changed in two ways.
2. The three-dimensional measuring apparatus according to claim 1, wherein the relationship between the gain and the offset is a relationship in which the gain and the offset are uniquely determined.
2. The three-dimensional measuring apparatus according to claim 1, wherein the gain and the offset are in a proportional relationship between the gain and the offset.
When the luminance value of each pixel of the two types of image data when the relative phase relationship of the light pattern having the two phase changes is set to 0 and γ, respectively, is V 0 and V 1 ,
The image processing means includes
The three-dimensional measuring apparatus according to claim 1, wherein a phase angle θ satisfying a relationship of the following formulas (1), (2), and (3) is obtained, and the height measurement is performed based on the phase angle θ. .
V 0 = Asinθ + B (1)
V 1 = Asin (θ + γ) + B (2)
A = KB (3)
However, γ ≠ 0, A: gain, B: offset, K: proportional constant.
The three-dimensional measuring apparatus according to claim 4, wherein γ = 180 °.
The three-dimensional measuring apparatus according to claim 4, wherein γ = 90 °.
7. The three-dimensional measuring apparatus according to claim 1, further comprising a storage unit that stores a relationship between the gain and offset of the light pattern calculated based on a calibration result or a measurement result separately performed in advance. .
7. The relationship between the gain and offset of the light pattern is obtained based on two types of image data captured under the light pattern whose phase has been changed in the two ways. The three-dimensional measuring apparatus described.
A light source that emits predetermined light, and a grating that converts the light from the light source into a light pattern having a striped light intensity distribution, and an irradiation unit that can irradiate at least the object to be measured with the light pattern;
Phase control means for controlling the transfer or switching of the grating and capable of changing the phase of the light pattern irradiated from the irradiation means in a plurality of ways;
A three-dimensional measurement method performed by a three-dimensional measurement apparatus including an imaging unit capable of imaging reflected light from the measurement object irradiated with the light pattern,
A relationship acquisition step of obtaining a relationship between gain and offset of the light pattern determined by a predetermined imaging condition based on a measurement result obtained by calibration or separately;
An image acquisition step of acquiring two types of image data imaged under the light pattern that has undergone two phase changes;
Using the relationship between the gain and offset of the light pattern obtained in the relationship acquisition step and the gain or offset value of the light pattern related to the measured coordinate determined from the luminance value of the measured coordinate on the image data. And a measuring step of measuring the height of the measured coordinates by a phase shift method based on the two types of image data.