JPH0621776B2 - Image clarity measurement method - Google Patents

Description

The present invention relates to a method for measuring the image clarity of a painted surface of a vehicle body panel or the like, or a surface of glass, plastic, rubber or the like.

[Conventional technology]

Conventionally, the surface of various samples as described above (hereinafter referred to as "measured surface")
As a method of measuring the image clarity, a panel on which a large number of characters of different sizes, which are generally used for visual acuity tests, are arranged and printed, is opposed to the surface to be measured.
A method was used in which the inspector visually inspected the characters, etc., and judged the clearness by determining the size of the characters, etc. that could be read.

[Problems to be solved by the invention]

However, in the above-described measurement method, the measurement results may be different depending on various conditions such as the illuminance at the time of inspection, the color of the sample, the positional relationship between the inspection panel and the sample and the inspector's eyes, the inspector's eyesight and fatigue. There was a problem that it was different and only a very rough judgment could be made.

In addition, various inspections tend to be automated, and there is a demand to automate the measurement of image clarity.

The present invention solves such a problem and can always measure the image clarity of the surface to be measured with high accuracy without being affected by the measurement conditions as described above, and the image clarity measurement method can be easily automated. The purpose is to provide.

[Means for solving problems]

In order to solve the above object, the present invention provides a slit light source.
From (2), project one slit light (Ls) on the surface to be measured (1a), and the reflected slit light (Ls') is the slit light (Ls) and the detection lines (3a, 4a) are orthogonal to each other. The line sensor (3, 4) is detected by the two line sensors (3, 4) which are arranged in parallel with each other at a distance as described above.
Sliding light (Ls) without changing the distance and inclination with respect to a)
Of the reflection slit light (Ls') detected by the two line sensors (3, 4) by relatively moving in parallel to the width direction of the slit light or the direction orthogonal to the slit light (Ls). The image clarity of the surface to be measured (1a) is measured by comparing

[Work]

When the slit light is projected and reflected on the surface to be measured, the reflected slit light is slightly swung in the slit width direction due to fine irregularities on the surface to be measured, which causes undulation.

Therefore, while the detection line is detected by the two line sensors arranged in parallel with each other at intervals so that the detection line is orthogonal to the undulating reflection slit light, the two line sensors are detected with respect to the surface to be measured. When the slit light is moved in parallel in the width direction of the slit light or in the direction orthogonal to the slit light without changing the distance and the inclination, the light receiving position of the reflected slit light detected by the two line sensors changes.

It was confirmed by experiments that this difference in the light receiving position, that is, the width of the undulation of the reflected slit light, corresponds extremely well to the degree of the image clarity, so by comparing the difference in the light receiving position, the image clarity of the measured surface Can be asked.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory diagram of a sharpness measuring method showing an embodiment of the present invention.

The slit light source 2 for generating the laser slit light Ls and the two line sensors 3 and 4 are attached to a measuring device for measuring the image clarity of the measured surface 1a such as the painted surface of the panel 1 at a predetermined angle as shown in the figure. The slit light source 2 projects the reflected slit light Ls' of the single slit light Ls projected onto the surface 1a to be measured, and the detection lines 3a and 4a by the light receiving element arrays respectively change the reflected slit light Ls' into the reflected slit light Ls'. The detection is performed by the first and second line sensors 3 and 4 which are arranged in parallel with each other at intervals so as to be orthogonal to each other. This line sensor 3, 4
A photodiode array, a CCD line sensor, or the like is used as this.

By doing so, the minute unevenness of the measured surface 1a onto which the slit light Ls is projected causes the undulations shown in the images on the line sensors 3 and 4 due to the reflected slit light Ls' (the broken line indicates the line sensor 3). , 4, assuming a screen on the same surface as 4). This waviness becomes larger as the image clarity of the surface 1a to be measured becomes worse.

Therefore, the first by the line sensor 3 and the peak position x ₁ of the video output signal VS ₁ and the peak position x ₂ of the video output signal VS ₂ of the second line sensor 4 is no longer generally equal, slit light generator 2 and the measuring device provided with the first and second line sensors 3 and 4 are moved in parallel relative to the surface to be measured 1a without changing the distance and the inclination (in the width direction of the laser slit light Ls or orthogonal thereto). The amount of change in the difference between x ₁ and x ₂ when scanning the surface 1a
The poorer the sharpness of the image, the larger it becomes.

In this embodiment, the data showing the freshness is provided with the variation amount of the difference | x ₁ −x ₂ | between the x ₁ and the x ₂ .

FIG. 2 is a block diagram showing an example of a signal processing circuit for measuring the image clarity, and two binary circuits corresponding to the first and second line sensors 3 and 4, respectively. 5 and 6, counter circuits 7 and 8, and light receiving position calculation circuits 9 and 10, a subtraction circuit 11, and a calculation unit 12,
The calculation result is displayed on the display unit 13, and the measurement result transmission unit 1
The measurement result is also transmitted to a remote place by the method of 4.

The operation of this signal processing circuit will be described with reference to FIGS.

Output from the first line sensor 3 in sequence, FIG. 3 (a)
For example, a video output signal V of 1024 bits as shown in
S ₁ is compared with the reference level Vr by the binarization circuit 5 to obtain the binarized video signal Dv ₁ as shown in FIG. 2B, and the counter circuit 7 produces the binarized video signal Dv 1.
_The number of bits T ₁ from the rising of ₁ to the number of bits Ta from the rising to the falling of 1 are counted by the read clock pulse of the first line sensor 3.

From the count values T ₁ and Ta, the light receiving position calculation circuit 9 reflects the reflected slit light L of FIG. 1 by the first line sensor 3.
The light receiving position x ₁ of s ′ is obtained by the calculation of x ₁ = T ₁ + Ta / 2.

On the other hand, FIG. 4 sequentially outputting from the second line sensor 4.
Similarly, the video output signal VS ₂ shown in (a) is also converted into a binary video signal Dv ₂ as shown in FIG. The number of bits T ₂ from the falling of the binarized video signal Dv ₂ and the number of bits Tb from the rising to the falling are counted, and the light receiving position arithmetic circuit 10 calculates x ₂ = T ₂ from the count values T ₂ and Tb.
+ Tb / 2 is calculated to obtain the reflected slit light Ls'.
The light receiving position x _{2 of} is calculated.

When x ₁ and x ₂ are sequentially obtained in this manner while scanning the measuring device with respect to the surface to be measured 1a, the results are shown in FIG.
It changes as shown by the solid line in (a) and (b).

The subtraction circuit 11 sequentially calculates the difference | x ₁ −x ₂ between x ₁ and x ₂ and inputs it to the calculation unit 12. The _| x 1 -x _{2 |} varies as shown in FIG. 5 (c).

In this case, one of the first and second line sensors 3, 4 may vibrate because one of the measuring device and the surface to be measured 1a vibrates during scanning.
Even if the light receiving position of the reflected slit light Ls' due to the change occurs, and x ₁ and x ₂ change as shown by the dotted lines in FIGS. 5 (a) and 5 (b), The shown value of | x ₁ −x ₂ | is hardly affected by the value.

The calculation unit 12 stores N values of this | x ₁ −x ₂ | and averages them. Value of each | x ₁ −x ₂ | stored and its average value Difference Root mean square value (shown in Fig. 5 (d)) To calculate.

This value of σ corresponds very well to the value of the sharpness that has been conventionally used as shown in FIG.
The value of may be displayed as it is on the display unit 13. In that case, the smaller the displayed value, the better the sharpness,
The larger the value, the poorer the sharpness.

Alternatively, a sharpness conversion table as shown in FIG. 6 may be stored in advance, and a numerical value obtained by converting σ into the freshness by the table may be displayed on the display unit 13.

When the functions of the light receiving position calculation circuits 9 and 10, the subtraction circuit 11 and the calculation unit 12 in FIG. 2 are performed by using the microcomputer, the microcomputer is configured according to the flow chart shown in FIG. Just run it.

In FIG. 7, xi is the difference | x ₁ between x ₁ and x ₂ at each scanning time point.
−x ₂ |, and ▲ ▼ is the average value of N times, Δxi
Is the deviation of each xi from the average value {circle around (1)}, and other symbols and arithmetic expressions are the same as those in the embodiment described above with reference to FIGS.

As described above, by operating the image clarity measuring method of the present invention, the slit light is projected onto the surface to be measured, and the size of the "waviness" caused by the partial deflection of the reflected slit light is affected. Taking into account the fact that it is proportional to the size of the unevenness of the measurement surface, the size of the unevenness of the measured surface, that is, the sharpness Can be measured.

Further, since the line sensor is moved in parallel with respect to the surface to be measured, it is possible to reduce the influence of vibration during measurement.

[Effects of the Invention] As described above, according to the image clarity measuring method of the present invention, the slit light is projected onto the surface to be measured, and the light receiving position of the reflected slit light having undulations reflected by the two line sensors. The image clarity can be measured by detecting and comparing the difference between the respective light receiving positions.

[Brief description of drawings]

FIG. 1 is an explanatory view of a sharpness measuring method showing an embodiment of the present invention, and FIG. 2 is a signal processing circuit for obtaining data indicating the sharpness from a video output signal by the two line sensors. 3 to 5 are various waveform charts for explaining the operation of the signal processing circuit of FIG. 2, and FIG. 6 is a relationship between the mean square value σ obtained by calculation and the sharpness. FIG. 7 is a flow chart showing the operation when various calculations in FIG. 2 are performed using the microcomputer. 1 ... Panel, 1a ... Measured surface 2 ... Slit light beam, 3 ... First line sensor, 4 ... Second line sensor, 5,6 ... Binarization circuit 7,8 ... Counter circuit 9, 10 ... Receiving position calculation circuit, 11 ... Subtraction circuit 12 ... Calculation section

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP 61-93934 (JP, A) JP 62-233710 (JP, A) JP 62-112003 (JP, A)

Claims (1)

[Claims] 1. A slit light source (2) projects a single line of slit light (Ls) onto a surface to be measured (1a), and the reflected slit light (Ls)
s ′) is detected by two line sensors (3, 4) arranged in parallel with each other with a space so that the slit light (Ls) and the detection lines (3a, 4a) are orthogonal to each other, (3, 4) is relatively translated with respect to the surface to be measured (1a) in the width direction of the slit light (Ls) or in the direction orthogonal to the slit light (Ls) without changing the distance and the inclination. , Measuring the sharpness of the surface to be measured (1a) by comparing the difference in the light receiving positions of the reflection slit light (Ls ′) detected by the two line sensors (3, 4). Characteristic sharpness measurement method.