JPH0660805B2 - Transparent film edge detector - Google Patents

Description

TECHNICAL FIELD The present invention relates to a transparent film edge detecting device for optically detecting the position of an edge of a transparent film.

<Prior Art> On a line for producing a transparent film, an apparatus for accurately detecting the position of the strip-shaped transparent film may be used.

In the case of optically detecting the position of such a transparent film, conventionally, a transparent film is sandwiched between a light emitter on one side and a light receiver on the other side so as to oppose the light to the edge position of the transparent film. The detection is performed by capturing the received light signal that changes according to the ratio of the light that passes through the transparent film.

<Problems to be Solved by the Invention> However, since the transparent film has a small light attenuation rate when the detection light passes through, it is possible to use light having a wavelength having a large light absorption rate in the transparent film or to use a polarizing filter. The difference in the amount of light passing through the transparent film and the amount of light not passing through the transparent film is increased so that the edge of the transparent film can be accurately detected.However, the difference in the amount of light can be large for a certain transparent film. However, there is a problem that the difference in light amount cannot be obtained with respect to another transparent film at all, and there is a demand for a versatile edge detector capable of accurately detecting the edge position of various transparent films.

<Means for Solving Problems> The present invention has been made to solve the above problems, and provides an edge detecting device for a transparent film capable of accurately detecting the edge position of the transparent film. Yes, it is configured as follows.

That is, the transparent film edge detection device of the present invention is
An image camera with a built-in one-dimensional image sensor that is installed diagonally to the transparent film and displays an image including the edges of the transparent film, and a light source and image that emits light obliquely to the transparent film and toward the image camera. A control circuit that scans the image sensor of the camera and outputs an image signal with a level difference at the edge position of the transparent film, a differential circuit that inputs the image signal and performs second-order differentiation, and a zero-cross point of the differential signal corresponding to the edge position. And a counter for counting the time from the rise of the image signal to the zero-cross point.

<Example> Hereinafter, an example of the present invention is described based on a drawing.

FIG. 1 is a block diagram of an edge detecting device for detecting the edge position of, for example, a long belt-shaped transparent synthetic resin film (hereinafter referred to as transparent film 1), and FIG. 2 and FIG. 3 are layout diagrams of the image camera 2. Is shown.

A one-dimensional image sensor 3 in which photodiode arrays are arranged in one row is provided in the image camera 2, and an edge portion (side end portion on one side) of the transparent film 1 via a lens 4.
The image camera is installed so that the image of the image is displayed on the image sensor 3, and the width direction of the transparent film 1 is located along the longitudinal direction of the image sensor 3.

Further, this image camera 2 is installed so as to have an angle of inclination α with respect to the longitudinal direction of the plane of the transparent film 1 so as to capture the image of the transparent film 1 from obliquely above. The light source 4 is arranged on the opposite side. The light source 5 is located on the light receiving axis of the image camera 2, and the angle of the light source 5 with respect to the transparent film when projecting toward the image camera 2 is also α, and the light source 5 has a shape long in the width direction of the transparent film 1. It is said.

The inclination angle α of the image camera 2 with respect to the transparent film 1 is set to be smaller as the transparency of the transparent film 1 is higher and larger as the transparency thereof is lower, and 10 to 30 degrees is suitable for a general transparent polyethylene film. Is.

Reference numeral 10 denotes a control circuit of the image sensor 3, which scans the photodiode array of the image sensor 3 at regular time intervals, and outputs the time-series image signal input by filtering and waveform shaping. To synchronize with the clock pulse signal, the clock pulse signal is sent to the gate circuit and the zero-cross detection circuit, which will be described later.

The output side of the control circuit 10 has a differentiating circuit 1 for performing second derivative.
1 is connected, and the gate circuit 1 is provided on the output side of the differentiating circuit 11.
2 is connected, and the gate circuit 12 is configured to open a gate by making a gate signal of a timing for passing only a signal corresponding to the edge position of the transparent film 1 in the image signal input from the control circuit 10.

A zero-cross detection circuit 13 is connected to the output side of the gate circuit 12, and the zero-cross detection circuit 13 detects the zero-cross point of the differential waveform sent via the gate circuit 12, and at the rising zero-cross point in synchronization with the rising edge of the image signal. It outputs a falling high level signal.

Reference numeral 14 is a gate circuit connected to the output side of the zero-cross detection circuit 13, which inputs the clock pulse signal sent from the control circuit 10 and uses the high-level signal from the zero-cross detection circuit 13 as a gate signal to open the gate for a high level. During this period, the clock pulse signal is output. Gate circuit 14
A counter 15 is connected to the output side of, and the counter counts the number of clock pulse signals input, that is, the time, and this numerical value indicates the edge position of the transparent film 1.

Reference numeral 16 is a D / A converter, 17 is a buffer circuit, both connected to the output side of the counter 15, and the D / A converter 1
The output side of 6 is connected to an analog input device for adjusting the position of the transparent film 1, for example, and the output side of the buffer circuit 17 is connected to a position adjusting device using a recorder or a pulse motor.

Next, the operation of the edge detecting device having the above configuration will be described.

The image camera 2 receives light from the light source 5 and projects an image of the edge of the transparent film 1 on the image sensor 3. At this time, the light from the light source 5 which forms the image of the transparent film 1 enters the transparent film 1 at an inclination angle α and passes therethrough,
When the light enters the transparent film 1, the reflectance of the surface is large, and the amount of transmitted light is reduced, so that the image of the transparent film 1 appears considerably darker than a portion where there is no object.

In this way, even with a transparent film, the image is clearly reflected as a shadow on the image sensor 3, and the position of the edge is also clearly shown. At this time, the control circuit 10 scans the image sensor 3 at regular intervals, thereby filtering and waveform-shaping the input time-series image signal to obtain an image signal a as shown in FIG. 4 for each scan. Output.

In this image signal a, the high level portion in the first half is a portion without a transparent film, the middle level portion in the latter half is a transparent film portion, and the edge position of the transparent film 1 is clearly defined by the level difference between the high level portion and the middle level portion. Shown.

The image signal a is sent to the differentiating circuit 11 to be secondarily differentiated, and the differential signal b is sent to the gate circuit 12. The differential signal b has differential waveforms at the first rising portion, the falling portion indicating the edge position, and the final falling portion for one image signal, and the differential signal b is sent to the gate circuit 12.

Then, the gate circuit 12 creates a gate signal c based on the clock signal from the control circuit 10 at the timing of passing only the central differential waveform indicating the edge position, opens the gate, and outputs the differential signal d indicating the edge position. The differential signal d is sent to the zero-cross detection circuit 13, and the zero-cross detection circuit 13 detects the zero-cross point of the differential signal d and rises in synchronization with the rising edge of the image signal a and a high-level signal e that falls at the zero-cross point. Is output.

This high level signal e is input to the gate circuit 14 as a gate signal, the gate circuit 14 opens the gate only during the high level signal e, and outputs the clock pulse signal f from the control circuit 10 during the high level signal e. The number of clock pulse signals g for one time output from the gate circuit 14, that is, the time indicates the edge signal of the transparent film 1. This clock pulse signal g is sent to the counter 15 and counted, and each scanning of the count 15 is performed. The count value of is
It is sent to the A converter 16 and the buffer circuit 17.

When the transparent film 1 is a strip-shaped film and runs in a space between rolls (not shown) to prevent the transparent film 1 from meandering, the edge detection device is used. Or the output of the buffer circuit 17 is sent to the control device as a control signal, and feed back control is performed so as to keep the edge position of the transparent film constant. On the other hand, the output of the buffer circuit 17 can be displayed or recorded as a numerical value without being connected to a display or a recorder.

<Effect of the Invention> As described above, according to the edge detecting device of the present invention, the image camera is obliquely arranged so that the light receiving axis is inclined with respect to the plane of the transparent film, and the light source is provided on the opposite side of the transparent film. Since it is placed on the light receiving axis, the light from the light source obliquely enters the transparent film, so the reflectance on the surface becomes large and the amount of light passing through the transparent film decreases, so that the portion containing the edges of the transparent film is reduced. It can be projected on the image sensor as a clear shadow.

Therefore, even if the transparent film is very thin and its transparency is very high, the level difference indicating the edge position in the image signal from the image sensor can be increased, and the edge of various transparent films can be increased. The position can be detected accurately and stably. Further, by deriving the zero-crossing point of the image signal after second-order differentiation, a signal indicating the edge position can be obtained with a relatively simple circuit.

Further, since the position of the edge can be quantitatively output as the count value of the counter, it can be used for feeding control of the transparent film, and the edge position of the transparent film can be accurately fed back.

[Brief description of drawings]

1 shows an embodiment of the present invention, FIG. 1 is a block diagram of an edge detection device, FIG. 2 is a side view showing the arrangement of an image camera,
FIG. 3 is a front view of the same, and FIG. 4 is a waveform diagram of a signal output from each circuit of the detection device. 1 ... Transparent film, 2 ... Image camera, 3 ... Image sensor, 5 ... Light source, 10 ... Control circuit, 11 ... Differentiation circuit, 13 ... Zero cross detection circuit, 15 ... Counter.

Claims (1)

[Claims] 1. An image camera having a one-dimensional image sensor installed obliquely with respect to a transparent film and displaying an image including edges of the transparent film; A light source for projecting light, a control circuit for scanning the image sensor and outputting an image signal having a level difference at the edge position of the transparent film, and a differentiating circuit for second-order differentiation of the image signal, An edge detecting device for a transparent film, comprising: a zero-cross detecting circuit for detecting a zero-cross point of a differential signal corresponding to an edge position; and a counter for counting the time from the rising of the image signal to the zero-cross point. .