JPH0587522A - Signal-detection device - Google Patents

Abstract

PURPOSE:To prevent malfunction of an object-detection device due to noise. CONSTITUTION:An output of a sensor 2 which detects an object is converted to a binary signal indicating whether the object exists or not, is input to a shift register 5 which is shifted by a certain clock, and then it is determined that the object exists when the number of data indicating that the object exists among parallel outputs of the shift register exceeds a specified number, thus enabling it to be judged whether the object exists or not with a certain width of confirmation time for improved resistance against noise.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an output signal detecting device for a sensor or the like in an object position detecting device or the like using a photo sensor or the like.

[0002]

2. Description of the Related Art In order to detect the position of an object using a photo sensor, the photo sensor is arranged along the passage of the object,
It is detected that an object blocks light from entering the photo sensor. Conventionally, in order to avoid malfunction due to noise from the photo sensor output, even if the photo sensor output reaches the level of the object, it is not immediately determined that the object is present, and the signal level of the object continues for a certain time or longer, for example, for several 100 μs to several ms. After confirming that it was done, it was determined that there was an object.

According to the above-mentioned configuration, if the photosensor output temporarily becomes the level of no object due to noise during the confirmation time from the time when the photosensor output becomes the level of the object, the initial confirmation time is broken. The confirmation time starts from the moment the noise disappears. For this reason, when there is a lot of noise, although the object already exists, the time point at which it is determined that there is an object gradually shifts, causing a malfunction of the device. On the contrary, if the confirmation time is shortened to avoid such a malfunction, the output of the photosensor will be at the level of the object existing for a longer time than the confirmation time due to noise or the like, and the risk of misidentifying the existence of the object increases.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to avoid erroneous determination due to noise or the like as described above when detecting an object position by a photo sensor.

[0005]

Means for Solving the Problems A fixed value corresponding to the output of a photosensor or the like which is above or below a judgment level is input to a shift register which can be shifted by a fixed clock pulse, and a parallel output of this shift register is used to output a signal indicating that an object exists. When the number of recorded bits is above or below a certain value, it is determined that there is an object.

[0006]

Now, assuming that the value corresponding to the existence of an object in the output of the photosensor is 1, and the value corresponding to the absence is 0, and this data is written in the shift register which is shifted by the clock of a constant cycle, the bit of the shift register is changed. When the number is n, the parallel output of the shift register represents a record of the output state of the photosensor from the present time to the past n clocks. If there is no noise and there is an object, the parallel output of the shift register is 1 for all n digits. If noise of 2 clock pulse width is entered within the confirmation time, the parallel output of the shift register is n-2 1 and 0.
Is 2. Therefore, when the number of 1 is more than one, it is determined that an object exists. The confirmation time is updated at the cycle of the clock pulse of the shift register regardless of the noise or the rise and fall of the photosensor output, so even if noise enters the middle, the confirmation is delayed. Disappear.

[0007]

FIG. 1 shows an embodiment of the present invention. In the figure, 1 is an object to be detected, 2 is a photo sensor, 3 is a light source, and the object 1 passes between the photo sensor 2 and the light source 3. 4 is a comparator for comparing the photo sensor output with a reference level,
When it is below the reference level, the signal "1" is output. Reference numeral 5 is an 8-bit shift register, which is shifted by the clock of 1 ms period output from the clock pulse generator 6 and reads the output of the comparator 4. Therefore, the register 5 always holds the output state of the photo sensor 3 for the past 8 ms from the present time. The parallel output of the register 5 is input to the determination circuit 7, and some of the bits of the shift register 5 whose output is 1 are counted. If the number is equal to or more than the reference value, the determination circuit 7 determines that an object exists. Is transmitted.

The above-mentioned determination is performed every 1 ms. The determination can be performed by software using a computer, but can also be performed by hardware, and an example of the determination circuit is shown in FIG. Each bit output of the shift register 5 is an AND circuit A1.
Is input to the counter C through A8. AND circuit A
In 1 to A8, the output of each bit of the shift register R is input as a gate pulse. The shift register is a ring register, and "1" is written in the first digit when the apparatus is started, and thereafter, the data of "1" is circulated in the register. The shift register R is shifted by a clock having a period of 1/8 of 1 ms, and the contents of the register 5 are rewritten once during 1 ms, and the AND gate A1
Open A8 in order. Then, the outputs of A1 to A8 are sequentially input to the counter C, so that the counter C is 1 m.
This means that the number of "1" bits in the shift register 5 is counted every s period. This count value is the reference number 6 in the comparator K.
When the count value is 6 or more, the comparator K outputs a signal that an object is present. Reference numeral 8 is a reference clock generator whose frequency is divided by 1/8 by the clock pulse generator 6 and is applied to the register 5 as a shift pulse.

[0009]

The effect of the present invention will be described with reference to FIG. In this figure, A is the output of the comparator 4 (comparing the output of the photo sensor with the reference level), and the high level is the detection signal of the presence of an object. In the figure, one graduation on the time axis is ms, and there was noise for two graduations three graduations after the object detection signal was output. In the case of the present invention, the count output of the counter K becomes 6 after 8 graduation time, that is, 8 ms from the time t, and at the time of T, the signal of the existence of the object is transmitted. In the conventional example, the confirmation time is broken at the time t ', and the confirmation time is restarted from the time d,
The determination of the existence of an object is delayed as compared with the present invention. The present invention eliminates such a delay.

[Brief description of drawings]

FIG. 1 is an overall circuit diagram of an embodiment of the present invention.

FIG. 2 is a circuit diagram of the determination circuit described above.

FIG. 3 is a diagram for explaining the effects of the present invention. 1 Object 2 Photosensor 5 Shift register 7 Judgment circuit

Claims (1)

[Claims] The sensor output is binarized according to the presence / absence of a signal and input to a shift register that is shifted with a constant clock, and when the number of signals present in the shift register parallel output is greater than or equal to a predetermined number, the signal is present. A signal detecting device, characterized in that a judging means is provided.