JPS6214794B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a CCD (charge coupled device)
and photoelectric switches using semiconductor image sensors such as BBD (Bucket Brigade Device).

This semiconductor image sensor has a large number of photosensitive elements, each of which is sequentially scanned by a scanning pulse, and pulse signals corresponding to the brightness and darkness of each photosensitive element are sequentially read out. Therefore, the size of the detected object can be determined by counting the number of pulse signals corresponding to the shadow part of the detected object, and the detection field of view can be limited by counting only pulse signals within a certain range. can. However, such a pulse counting method requires a counting circuit, making the circuit configuration complicated.

The present invention is intended to solve these problems, and the first object of the invention is to provide a photoelectric switch that can determine the size of an object to be detected with a simpler configuration without requiring a counting circuit. It's about doing.

A second object of the invention is to provide a photoelectric switch that can change the detection field of view with a simpler configuration.

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, the area between the light source 1 that projects parallel light rays and the condensing lens 3 is the detection area, and if the object to be detected 2 is present here,
The shadow is reduced and the semiconductor image sensor 11
The image is projected onto a large number of photosensitive elements arranged in one row. The brightness and darkness of each photosensitive element is determined by the second
By applying a scanning pulse φ as shown in the figure, the data are sequentially read out in series. This scanning pulse φ is continuously sent from a fixed frequency oscillator 21 to the semiconductor image sensor 11 as shown in FIG.
Until ED (see FIG. 3), each element is sequentially scanned by a number of scanning pulses corresponding to the number of elements, and the bright and dark states are read out. This read signal passes through the AC amplification circuit 12 and becomes a continuous pulse signal as shown in FIG. 3A. The scan activation pulse ST is obtained from the Q output terminal of a D flip-flop 23, with the output of oscillator 21 applied to the trigger terminal and the output of oscillator 22 applied to the set terminal. Therefore, it depends on the frequency of the oscillator 22, but this oscillator 22 is a frequency variable type, and by adjusting the variable resistor, the frequency is changed, and as a result, the scanning starting pulse
It is possible to change the ST cycle.

The amplified signal read out from the semiconductor image sensor 11 corresponds to the brightness and darkness of each element, with a high pulse corresponding to "bright" and remaining low when "dark" (Fig. 4A). reference). This signal passes through the binarization circuit 13 and is converted into a pulse-like binarized signal as shown in FIG. (See Figure 4C). When the frequency of φ is constant, the number of elements in the dark state is the output of this D flip-flop 14 (the fourth
This corresponds to the time when the voltage (C) in the diagram becomes "L".

By the way, the output level of the semiconductor image sensor 11 is changed according to the amount of incident light, and "H" is output from the binarization circuit.
It is necessary to adjust the level at which the pulse occurs.
By changing the sensitivity of the semiconductor image sensor 11, its output level can be changed. This sensitivity corresponds to the intensity of light within one readout period x irradiation time, that is, it is proportional to the readout period for each element. The size of the object to be detected cannot be determined by determining the time during which the output is "L". Therefore, the period of φ is kept constant, and only the period of the scan activation pulse ST is changed (by changing this period, the irradiation time also changes, so the sensitivity changes). That is, the reason why the oscillator 22 is of a variable frequency type is to adjust the sensitivity.

The output of the D flip-flop 14 is sent to a timer circuit 31 for size discrimination. This timer circuit 31 is triggered when the input changes from "H" to "L", and produces an "H" output for a time set to a desired value (see D in Figure 5 A and B). . The output of this timer circuit 31 is applied to the output line of the D flip-flop 14 via a diode 32, so that
While the output of the timer circuit 31 is "H", the "L" output is not sent to the next timer circuit 17. Note that the circuit including the resistor 15 and capacitor 16 inserted into this output line is a circuit that delays the timer circuit 31 to some extent so that the above-mentioned prohibition is effective in accordance with the response of the timer circuit 31. The timer circuit 17 is for output, and when an “L” input is received, it becomes “H” for a certain period of time.
This produces an output of

As shown in Figure 5 A, the detected object is small and D
If the "L" time of the output C of the flip-flop 14 is shorter than the time set by the timer circuit 31, the input of the timer circuit 17 remains "H", so the output of the timer circuit 17 remains "L". (See Figure 5, E and F). On the other hand, if the object to be detected is large and the time that the D flip-flop 14 is at "L" is longer than the set time of the timer circuit 31, the timer circuit 31 will time-up as shown in FIG. After that, the input of the timer circuit 17 suddenly becomes "L", so that the timer circuit 17 outputs "H" (see FIG. 5, B, E and F).

In this way, by simply changing the set time of the timer circuit 31, a detected object of any size can be determined.

In Figure 6, the scan starting pulse ST is sent to the timer circuit 4.
1 to delay the desired time (see Fig. 7G), and further delay the desired time by the timer circuit 42 (see Fig. 7H).
), this is further inverted by an inverter 43 (see FIG. 7I), and is sent to the input of the timer circuit 17 via a diode 44. The other configurations are the same as in FIG. 2, and the same parts are given the same numbers. Therefore, this inverter 43
While the output I of is “H”, the D flip-flop 14
The timer circuit 17 is not triggered even if the output C of the inverter 43 is "L", and the timer circuit 17 is triggered by the "L" output of the D flip-flop 14 when the output of the inverter 43 is "L".

Therefore, by changing the time settings of the timer circuits 41 and 42, the detection field of view can be set arbitrarily.

As explained above, according to the first invention, the period of the scanning pulse is fixed and processed by the timer circuit without providing a counting circuit for counting the pulse output from the semiconductor image sensor. This makes the circuit configuration extremely simple, and by varying the period of the scan activation pulse, sensitivity can be easily set according to the amount of incident light.
Then, by simply changing the set time of the timer circuit, it is possible to discriminate a detected object of any size.

Further, according to the second invention, the circuit configuration is simplified as in the first invention, and the sensitivity can be easily set, and the detection field of view can be arbitrarily set using the timer circuit.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view showing the positional relationship of a light source, an object to be detected, a condensing lens, and a semiconductor image sensor according to an embodiment of the present invention, FIG. 2 is a circuit diagram of the embodiment, and FIG. 4, 5A and 5B are time charts for explaining the operation of the circuit in FIG. 2, FIG. 6 is a circuit diagram of another embodiment, and FIG.
This is a time chart for explaining the operation of the circuit shown in the figure. 1... Light source, 2... Object to be detected, 3... Condenser lens,
DESCRIPTION OF SYMBOLS 11... Semiconductor image sensor, 12... AC amplification circuit, 13... Binarization circuit, 14, 23... D flip-flop, 17, 31, 41, 42... Timer circuit, 21, 22... Oscillator.

Claims (1)

[Claims] 1. A semiconductor image sensor having a light source and a large number of photosensitive elements arranged so that light from the light source enters through a detection area, and sequentially scanning each photosensitive element of the semiconductor image sensor. ,
a fixed frequency oscillator that generates a scanning pulse for reading out a pulse signal according to a bright/dark state; a variable frequency oscillator that generates a scanning activation pulse that determines a readout cycle of the semiconductor image sensor; A photoelectric switch comprising a flip-flop that converts a pulse signal generated by the flip-flop into a rectangular wave, and a timer circuit that delays the rectangular wave output of the flip-flop by an arbitrary time and inhibits the rectangular wave output while the delayed output is occurring. 2. A semiconductor image sensor having a light source and a plurality of photosensitive elements arranged such that light from the light source enters through a detection area, sequentially scanning each photosensitive element of the semiconductor image sensor,
a fixed frequency oscillator that generates a scanning pulse for reading out a pulse signal according to a bright/dark state; a variable frequency oscillator that generates a scanning activation pulse that determines a readout cycle of the semiconductor image sensor; a flip-flop that converts the pulse signal into a rectangular wave; and a gate signal that receives the scan activation pulse and allows the rectangular wave output of the flip-flop to pass only for a desired time after a desired time from the scan activation pulse. A photoelectric switch equipped with a timer circuit that generates electricity.