JPH0369043B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to improving the measurement accuracy of an optical outer diameter measuring device using a self-scanning one-dimensional photodiode array (hereinafter referred to as an image sensor).

B. Prior Art FIG. 1 shows an example of the principle of an optical outer diameter measuring device that optically measures the outer diameter of an object and the width of a tape using an image sensor. In the figure, 1 is an image sensor, 2 is a light projector that irradiates parallel light toward the image sensor 1, and 3 is an object placed between the image sensor 1 and the light projector 2. This optical outer diameter measuring device measures an object 3 projected onto an image sensor 1.
The outer diameter of the object 3 is determined by measuring the length of the shadow of the object 3 using the image sensor 1.

By the way, a state in which the image sensor 1 receives incident light and outputs it as an electrical signal will be explained as follows.

FIG. 2 shows a simplified internal structure of the image sensor 1, where 4 is a photo array that converts incident light into an electrical signal, and 5a and 5b are placed on both sides of the photo array 4, and the odd and even numbers of the photo array 4 are respectively arranged. A shift register that extracts electrical signals from the second element in parallel and outputs serial outputs Vout1 and Vout2 in synchronization with shift register clock signals φ1 and φ2, 6
a, 6b are the photo array 4 and the shift register 5a,
transfer gates 7a and 7b, which are respectively disposed between the transfer gates 5b and 7a and 7b and open only when the transfer gate clock signal φTG is generated;
are leakage current discharge channels, and 8a and 8b are output gates.

The operation of the above configuration will be explained with reference to the timing chart shown in FIG.

The light projector 2 continuously irradiates parallel light beams L towards the image sensor 1 (direct current lighting). As a result, charges are accumulated in each element of the photoarray 4 in accordance with the irradiation amount. That is, charges are accumulated except for the part blocked by the object 3 and turned into a shadow. When the transfer gate clock signal .phi.TG is generated, the transfer gates 6a and 6b are momentarily opened and the charges are transferred to the shift registers 5a and 5b. At this time, the data stored in the shift registers 5a and 5b, that is, a data string consisting of a series of "1" or "0" (at this stage, it is an analog quantity, and in reality, after being output from the image sensor, it is ” and “0” are determined.) represent the respective lengths of the illuminated portion and the shadowed portion. This data string is output as a pulse train OUT from output gates 8a and 8b in response to shift register clock signals φ1φ2. Note that the reason why the elements of the photo array 4 are divided into odd numbered columns and even numbered columns and the outputs are taken out is to speed up the data transfer time, etc. The separated outputs out1 and out2 are then combined to form one pulse train OUT. By distinguishing this pulse train OUT into "1" and "0" at a predetermined threshold, and measuring the time width T of the continuous "0" part b sandwiched between the continuous "1" parts a and a. The outer diameter of the object 3 can be known accurately.

However, in the conventional structure described above, the object 3 is
The disadvantage is that measurement errors occur when the sensor moves or vibrates. As a result of various experiments, the inventor of the present invention found that the cause of this is the characteristic of the image sensor 1, that is, the characteristic that the charge accumulated in the photoarray 4 remains for a certain period of time in approximately proportion to the product of illuminance and irradiation time. Ta. In other words, if an object vibrates while being irradiated with light,
The width of the light irradiation part or the light blocking part changes by that amount, and this causes a measurement error.

Furthermore, since the shift registers 5a, 5b, output buffer amplifier, etc. that make up the image sensor 1 are lined up with the photoarray 4 that detects light, when light is incident, a voltage is generated at the PN junction due to the photoelectric effect. There was a problem in that the signal changed when output was taken out, causing measurement errors.

C. Purpose of the Invention The present invention provides an optical outer diameter measuring device in which the light from a projector is blocked by an object to be measured, and the length of the blocked portion is measured using an image sensor. Also, it does not cause measurement errors, and it is possible to
The purpose of this invention is to provide a measurement method that can prevent measurement errors caused by light irradiating the PN junction.

D. Structure of the Invention The present invention is an optical system that places an object to be measured between a light emitter and a receiver, projects a light shadow generated by blocking light from the emitter onto the light receiver, and measures the outer diameter of the object using the output signal. In the external diameter measuring device, a solid-state light emitting element is used as the light source of the emitter, a photo array for photoelectric conversion and a shift register for signal extraction are combined in parallel in the receiver, and a self-scanning one-dimensional photo sensor with a built-in buffer amplifier for output is used. Using a diode array, the pulsed light emission of the solid-state light emitting device, the clearing operation of the shift register performed by skipping a predetermined number of bits or more, the parallel transfer of the accumulated charge of the photo array to the shift register, and the shift output of the shift register are performed in this order and mutually. The outer diameter of the object is measured by measuring the width of the portion of the output pulse train that corresponds to the shadow.

E Example The present invention is characterized in that a solid-state light emitting element, which is a light source of a floodlight, generates pulses.
When applying this method to an actual image sensor (self-scanning one-dimensional photodiode array), there are additional issues that must be considered.

One of them is the timing of pulse emission, data transfer from the photo array to the shift register, and take-out of the data string from the shift register, and errors will occur if the characteristics of the image sensor are not taken into account.

Another problem is that when pulsed light is emitted, the amount of light irradiated is much smaller than when continuous light is emitted, making it impossible to make the image sensor output a sufficient amount.

Regarding the former of the above problems, timing settings as described later can be made to enable highly accurate detection, and regarding the latter, an optical measuring device (patent application No. 57 −39860)
By adopting this optical system, it is possible to irradiate the image sensor with sufficient light.

First, the timing of pulse emission from the projector 2, data transfer from the photo array 4 to the shift registers 5a and 5b, and data extraction from the shift registers 5a and 5b will be explained.

As shown in FIG. 2, the image sensor 1 has a photo array 4 and shift registers 5a, 5b electrically separated by transfer gates 6a, 6b.
The timing of pulse emission is determined by the shift register 5a,
In principle, it is thought that there will be no problem even if it is performed while data is being retrieved from 5b. However, in reality, if pulsed light emission is performed during the data outputs out1 and out2, the waveform of the pulsed light emission will be superimposed on the output, causing measurement errors. This is a buffer amplifier in the image sensor 1 (output part built into the IC chip of the image sensor) by pulsed light emission.
It is presumed that a voltage is generated in the PN junction due to the photoelectric effect. Furthermore, once the data output is taken out from the shift registers 5a, 5b and all the stored contents of the shift register constituent elements become "0", the accumulated charges generated in the photo array 4 due to pulsed light emission are immediately transferred to the shift registers 5a, 5b. It seems that there is no problem even if it is. However, in reality, measurement errors may occur with this method. The cause of this is that the shift register 5 was once cleared to “0”.
It is estimated that part of the memory contents of a and 5b change to a level (analog voltage) higher than the "1" level or clear level due to pulsed light emission, and this is superimposed with the data transferred from the photo array 4. be done.

Therefore, in the embodiment of the present invention, the occurrence of the above-mentioned error is avoided by performing pulse emission, data transfer from the photo array 4 to the shift registers 5a and 5b, and data extraction from the shift registers 5a and 5b at the timing shown in FIG. It is now possible to detect lost items with high accuracy.

The timing chart shown in FIG. 4 will be explained next.

After the light source of the projector 2 issues a pulse LP with a time width of, for example, 90 .mu.s, shift register clock signals .phi.1 and .phi.2 are supplied for the number of bits or more of the shift registers 5a and 5b to perform idle feeding. As a result, even if the shift registers 5a and 5b store a "1" level due to pulsed light emission or a level (analog voltage) higher than the clear level, the potentials are all at the clear level. Here, the photoarray 4 stores data representing the length of the light shielding of the object 3 at the time of the pulsed light emission LP. Next, the transfer gate clock signal φTG is supplied once to the transfer gates 6a and 6b. As a result, the charges accumulated in the photoarray 4 are transferred to the shift registers 5a and 5b. Thereafter, by supplying shift register clock signals φ1 and φ2 to shift registers 5a and 5b, a pulse train OUT is outputted from shift registers 5a and 5b through output gates 8a and 8b. Then, distinguish this pulse train OUT into “1” and “0” at a predetermined threshold value, and measure the time width T of the continuous “0” portion b sandwiched between the continuous “1” portions a and a. Therefore, the outer diameter of the object 3 can be accurately known.

By emitting pulse light and driving the image sensor 1 at the above timing, it is possible to prevent the waveform of pulse light emission from appearing in the output and to prevent erroneous memories caused by pulse light emission in shift registers 5a and 5b from being mixed into the output. This enables highly accurate measurements.

Next, an optical system that compensates for the decrease in the amount of light irradiated to the image sensor 1 due to changing continuous light emission (DC lighting) to pulsed light emission will be described with reference to FIGS. 5 to 7.

In the figure, 9 is a solid-state light emitting element as a light source,
For example, an LED, 10 a rod lens, and 11 a lens constitute the projector 2. Next 12
1 is a cylindrical lens, 1 is an image sensor, and the above constitutes a light receiver 13. Note 3
is an object.

Here, the solid-state light emitting element 9 uses, for example, an infrared LED with sharp directivity. Infrared LEDs exhibit the peak sensitivity in the spectral characteristics of the image sensor 1, so they can be measured efficiently, and their directivity is sharp, so there is less scattering in the direction perpendicular to the arrangement of the photo array 4 of the image sensor 1, and the light can be efficiently transferred to the photo array. 4 can be irradiated. Further, although not shown, if an infrared passing filter is inserted in front of the image sensor 1 or in front of the cylindrical lens 12, it is possible to reduce the influence of ambient light caused by the fluorescent light.

Here, the rod lens 10 is a solid-state light emitting element.
It is used to collect and uniformize the light from the LED 9 at the same time, and is used in the present invention for the following reasons.

The size of the light emitting source of the LED 9, which is a solid state light emitting device, is several meters in diameter, and in order to create uniform parallel light, the light must be focused on a single point. Since the image sensor 1 measures the length of the object 3 only in the width direction, it is sufficient to use the rod lens 10 to create a linear light source that diffuses light only in that direction.
Furthermore, the rod lens 10 serves to make the light intensity distribution uniform. Figure 7 is a diagram showing the light intensity distribution of the LED 9, which is a solid-state light emitting device, with the horizontal axis representing the beam angle and the vertical axis representing the light intensity. B shows the light intensity distribution when the rod lens 10 is inserted. As is clear from the figure, A, that is, when the rod lens 10 is not inserted, is a solid-state light emitting device.
Since the light at the center of the LED 9 is stronger than at the periphery, detection sensitivity varies depending on the position, resulting in poor measurement accuracy. However, when B, that is, the rod lens 10 is inserted, the maximum light intensity decreases, but the light intensity distribution becomes uniform, so that stable measurement is possible regardless of the position of the detection sensitivity.

Next, the lens 11 is for collimating the light diffused by the rod lens 10.
0 is separated by the focal length of the lens 11.

Next, the cylindrical lens 12 is necessary for the following reasons.

The light having information on the outer diameter of the object 3 is transmitted through a rod lens 10.
Light in a direction perpendicular to this direction does not contain information. Therefore, the cylindrical lens 12 focuses light on the photo array 4 only in a direction perpendicular to the direction in which the light from the rod lens 10 is diffused. Then, it is possible to effectively utilize only the amount of light without losing information on the outer diameter of the object 3 and to increase detection sensitivity. Note that the photo array 4 of the image sensor 1 is a rod lens 1.
Arrange them in the direction in which light is diffused at 0.

Thus, the projector 2 and the receiver 13 are arranged to face each other with the object 3 in between. Light from the LED 9, which is a solid-state light emitting element, is focused by a rod lens 10 and then uniformly diffused. After the diffused light is changed into parallel light by the lens 11, it irradiates the object 3 and is guided to the cylindrical lens 12. Here, the light having information on the outer diameter of the object 3 is light in the arrangement direction of the photo array 4, and the light that does not include information on the outer diameter of the object 3 and perpendicular to the arrangement direction of the photo array 4 is imaged by the cylindrical lens 12. The light is focused on the sensor 1. That is, only the amount of light is effectively used without losing information about the outer diameter of the object 3. Next, the image sensor 1 converts the light intensity distribution projected onto the photo array 4 into an electrical signal, and processes this signal as described above to measure the outer diameter of the object 3 to be determined.

Note that although the above embodiment employs an optical system that emits parallel light rays and projects the shadow of the object onto the image sensor 1, the optical system is not limited to this example. For example, although not shown, a floodlight is placed behind the object 3,
The image of the object 3 may be formed on the image sensor 1 by a lens placed in front.

Furthermore, the device of the present invention can also be used to measure the width of wide tapes or cloths, and to detect the presence or absence of meandering in a running strip. In these cases, the optical outer diameter measuring device of the present invention is installed so as to sandwich both ends or one end thereof, and the position of the end of the light shielding portion is measured.

E. Effects of the Invention The present invention is an optical outer diameter measuring device using an image sensor (self-scanning one-dimensional photodiode array), in which a solid-state light emitting element, which is a light source of a projector, emits pulse light to a predetermined value while clearing a shift register. Since the output is taken out at the timing of
By eliminating errors caused by the photoelectric effect of the junction, highly accurate and reliable outer diameter measurement becomes possible.

[Brief explanation of drawings]

Figure 1 is a diagram showing the principle of the optical outer diameter measuring device.
FIG. 2 is a schematic diagram of the internal configuration of the image sensor, FIG. 3 is a diagram showing the operation timing of a conventional optical outer diameter measuring device, and FIG. 4 is a diagram showing the operation timing of an embodiment of the device of the present invention. 5 and 6 are a front view and a plan view showing an optical system according to an embodiment of the present invention,
FIG. 7 is a light intensity distribution diagram showing the effect of a rod lens. 1...Self-scanning one-dimensional photodiode array (image sensor), 2...Floodlight, 3...Object, 4...
Photo array, 9...Solid light emitting device (light source), LP...
Waveform of pulsed light emission.

Claims (1)

[Claims of Claims] 1. An optical method in which an object to be measured is placed between a light emitter and a receiver, the shadow of the light produced by blocking the light from the emitter is projected onto the receiver, and the outer diameter of the object is measured based on the output signal. In the outer diameter measuring device, a solid-state light emitting element is used as the light source of the emitter, a photo array for photoelectric conversion and a shift register for signal extraction are combined in parallel in the receiver, and a self-scanning one-dimensional photodiode with a built-in buffer amplifier for output is used. Using an array, the pulsed light emission of the solid-state light emitting device, the clearing operation of the shift register performed by skipping a predetermined number of bits or more, the parallel transfer of the accumulated charge of the photoarray to the shift register, and the shift output of the shift register are performed in this order and mutually. An optical outer diameter measuring device that measures the outer diameter of an object by measuring the width of a portion corresponding to the shadow of an output pulse train at timings that do not overlap.