JPH07128018A - Binarization method - Google Patents

Abstract

PURPOSE:To provide a high-precision measuring method utilizing a binarization processing method which is easily effected by the quantity of surrounding light in the measurement of shape and dimensions using a CCD linear image sensor. CONSTITUTION:The title method consists of a circuit for detecting the quantity of surrounding environmental light by operating an integration circuit 3 with a switching input timing generation circuit 2 in synchronization with the scanning of a CCD linear sensor output 1 and a sample/hold circuit 4 for retaining the integration value and using it as a reference of the binarization threshold and the CCD linear sensor output 1 is binary-coded in reference to the threshold.

Description

Detailed Description of the Invention

[0001]

[Industrial application] When measuring the shape and size using a CCD linear image sensor, changes in the state of the optical system such as dirt on the lens, changes in the amount of light due to air pollution such as smoke and fog, ambient light, etc. The objective is to develop a high-precision measurement method that uses a binarization method that is not easily affected by the amount of ambient light.

[0002]

2. Description of the Related Art For example, let us consider a case where the product shape and dimensions of the same product number are repeatedly measured. First, the threshold voltage value when the analog output voltage of the sensor is binarized is initially set by the measurer according to the light source light amount, the ambient light amount, and the like. Then, the amount of change in the ambient light amount is estimated based on the magnitude of the variation in the data obtained by actually performing the measurement several times, and the data is used to determine the binarization threshold value. That is, the binarization threshold value is determined by the ambient light amount data up to the previous measurement. Also,
Binarization methods that determine the threshold value in real time are also implemented. They use one or more sensors to measure the amount of ambient light and use the data obtained there, in addition to those for shape and size measurement. It is used to determine the binarization threshold.

[0003]

However, the shape,
With a measurement system that uses only one sensor for dimension measurement, it is difficult to determine the binarized threshold value in real time, so it is difficult to improve the accuracy of the measurement data. Also, in order to realize threshold value determination in real time, the surrounding environment is individually determined. If the light quantity measuring sensor is used, the system becomes large and the cost further increases. When a single sensor for this dimension measurement and ambient light quantity measurement is used, first the sensor scan for dimension measurement is performed so that only the ambient light quantity is detected without an object to be measured and the threshold value is determined based on that data. Is required twice or more, and there is a time lag between when the amount of ambient light is detected and when the dimension of the measurement object is measured, so that the threshold setting is not accurate and the real-time property is impaired. The dimensions will also be incorrect. Next, when each dedicated sensor for ambient light measurement and dimension measurement is provided, the threshold is determined by the data obtained by the ambient light measurement sensor, and in the system used for dimension measurement,
It is necessary to synchronize the timings of two or more sensors used to improve the measurement accuracy, and if the timings deviate from each other, the measurement accuracy will decrease, and adding multiple sensors like this will increase the system size and cost. It has drawbacks. In view of such drawbacks, the present invention provides a high-precision measurement method using a binarization processing method that is not easily affected by ambient light quantity changes such as light source light quantity change and ambient light with only one sensor. To aim.

[0004]

SUMMARY OF THE INVENTION The present invention is a measuring method for irradiating an image sensor with light from a light source through an object to be measured, and measuring the external dimensions by the length of the shadow of the object to be detected projected on the image sensor. As shown in FIG. 1, the CCD linear sensor output 1 will be described with reference to the drawings.
A circuit for activating the integration circuit 3 by the switch input timing generation circuit 2 in synchronism with the scanning of 1 to detect the ambient light quantity, and a sample hold circuit 4 for holding this integration value and using it as a reference of a binarization threshold value. The CCD linear sensor output 1 is binarized using this as a threshold value.

[Action]

The features of the present invention are (1). The point that the binarization threshold value is determined in real time, and the ambient light amount data necessary for the binarization threshold value determination is measured by the shape and dimension measurement sensor instead of the newly installed sensor. (2). For each CCD linear sensor scan, a binarization threshold value adapted to the ambient light amount at that time is determined, and the CCD linear sensor analog output obtained by that scan is binarized by the threshold value determined by the scan. Point to do. The point is that the above two points were realized at the same time. The operation of the above configuration will be described with reference to the time charts shown in FIGS. 2 and 3, and the operation of FIG. 1 will be described.
First, CCD linear sensor output 1 (a in the waveform of FIG. 2)
Switch input timing generation circuit 2 in synchronization with the scanning of
The integration circuit 3 (waveform c in FIG. 2) is operated by (waveform b in FIG. 2) to detect the amount of ambient light. The integrated value (waveform c) obtained here is held by the sample hold circuit 4 (waveform d) and used as a reference for the binarization threshold value. The sample-hold circuit 4 holds the integrated value (waveform d) until the next sample signal arrives, and binarizes the CCD linear sensor output 1 as a reference value of the threshold value of the binarizing circuit 5. With the above output, a waveform e showing a highly accurate product dimension can be obtained.

[0006]

EXAMPLE In order to verify the effectiveness of the invented principle, a dimension measurement experiment was conducted in comparison with a measurement system in which an optical system and a circuit were actually constructed and a binarized threshold value was fixed. In this experiment,
As shown in FIG. 3, first, a binary output is used to generate a pulse at the rising and falling edges of this binary output. Then, the CCD sensor pixel count value at that time was transferred to a computer, the count value was converted into the size of the measurement object, and the dimension was measured. As a result, the effectiveness of this system as a highly accurate dimension measurement method was confirmed. In the method of fixing the threshold value, the measured value obtained without the manual adjustment of the threshold value greatly changes when the light amount of the light source changes.
On the other hand, in this system, almost constant measurement values were obtained even when the light source quantity changed. This is because the binarization threshold value is automatically changed in accordance with the change in the light amount of the light source, indicating that the circuit added this time is effectively functioning. Further, by combining with a method such as interpolating data between pixels to obtain pixels in a sub-pixel manner, it is possible to perform measurement with higher accuracy.

[0007]

As an effect of using the present invention, a slight change in the light quantity due to the life of the light source and the amount of ambient light which is considered to have affected the measured value in the conventional measuring system (such as lighting of the room in which the system is installed) ), It is possible to ignore the effect of the binarization threshold value for each scan of the CCD linear sensor. In addition, the ambient light amount can be detected within about 5% of the entire pixel, and when a CCD linear sensor is conventionally used for measurement, electrical noise is disliked and effective use of the unused portion can be achieved. It became a thing. Furthermore, the binarization enables real-time measurement, downsizing of the system, and cost reduction.

[0008]

[Brief description of drawings]

FIG. 1 is a block diagram of the system of the present invention.

FIG. 2 is a time chart diagram of the present invention.

3 is a composite view of the time chart diagram of FIG. 2. FIG.

[0009]

[Explanation of symbols]

 1 CCD linear sensor output 2 Switch input timing generation circuit 3 Integration circuit 4 Sample hold circuit 5 Binarization circuit a Waveform of CCD linear sensor output 1 Waveform of switch input timing generation circuit 2 Waveform of integration circuit 3 d of integrated value Waveform e Waveform showing product dimensions

Claims (1)

[Claims] 1. A method of irradiating an image sensor with light from a light source through an object to be measured and measuring an external dimension by the length of a shadow of the object to be detected projected on the image sensor, the timing being synchronized with scanning of the sensor. From the circuit that operates the integration circuit by the generation circuit to detect the total amount of light received by the sensor based on the light from the light source and ambient light, and the sample and hold circuit that holds this integrated value and uses it as the reference for the binarization threshold. The binarization method is characterized in that the CCD linear sensor output is binarized using this as a threshold.