JPH0777405A - Photoelectric object sensor - Google Patents

Abstract

PURPOSE:To provide a photoelectric object sensor not affected by the surface reflection factor. CONSTITUTION:This photoelectric object sensor is provided with a light emitting means 1, a light receiving means 6, a variable amplifying means 10, a processing means 12, and a control means 14. The light emitting means 1 projects the incidence light 2 to a prescribed monitor region. The light receiving means 6 receives the reflected light 7 returning from the monitor region and outputs an electric signal corresponding to the light quantity. The variable amplifying means 10 amplifies the electric signal at a given gain and outputs a defection signal. The processing means 12 processes the detection signal and outputs the position information of an object existing in the monitor region. The control means 14 adjusts the gain of the variable amplifying means 10 according to the preset distance range. The variable amplifying means 10 outputs a saturated detection signal when the object exists within the preset distance range in the monitor region, and it outputs a nonsaturated detection signal when the object exists outside the preset distance range.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a photoelectric object sensor. More specifically, the present invention relates to a technique for detecting the position of an object existing in a surveillance area. In addition, the present invention relates to a technique for identifying whether an object is a moving human body or an article in a stationary state.

[0002]

2. Description of the Related Art A conventional photoelectric object sensor is generally composed of a light emitting element, a light receiving element, an amplifier, a microcomputer and the like. The light emitting element projects incident light onto a predetermined monitoring area. The light receiving element receives the reflected light returning from the monitoring area and outputs an electric signal according to the amount of light. The amplifier amplifies the electric signal with a predetermined gain and outputs a detection signal.
The microcomputer processes the detection signal and outputs the position information of the object existing in the monitoring area.

[0003]

Conventionally, in order to detect the presence or absence or the position of an object, a predetermined threshold value is set and the detection signals are compared. The predetermined threshold value is set based on, for example, the detection signal level of the reflected light returning from the monitoring area background. There is no particular problem in detecting an object located at a relatively long distance, but in the case of detecting an object located at a short distance, the amount of reflected light fluctuates greatly due to the difference in surface reflectance. Therefore, the level of the detection signal also greatly changes, and there is a possibility that erroneous detection may occur in the determination method using a fixed threshold value. Further, since the detection signal level is not constant due to the difference in reflectance, it is originally difficult to set an appropriate threshold level.

[0004]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, the present invention provides a photoelectric object sensor capable of always stable object detection without being affected by the surface reflectance of the object to be detected. The purpose is to provide. The following measures have been taken in order to achieve this object. That is, the photoelectric object sensor according to the present invention includes a light emitting means, a light receiving means, a variable amplifying means, and a processing means as basic constituent elements. Further, as a feature of the present invention, the control means for the variable amplification means is included. The light emitting means projects incident light onto a predetermined monitoring area. The light receiving means receives the reflected light returning from the monitoring area and outputs an electric signal according to the amount of light. The variable amplification means amplifies the electric signal with a given gain and outputs a detection signal. The processing means processes the detection signal and outputs position information of an object existing in the monitoring area. The control means adjusts the gain of the variable amplification means according to a preset distance range. According to this gain adjustment, the variable amplification means outputs a saturation detection signal when the object is within the distance range in the monitoring area, and outputs a non-saturation signal when the object is outside the distance range. The processing means discriminates the saturation detection signal and the non-saturation detection signal to obtain the position information of the object.

Further, when the saturation detection signal output from the variable amplification means determines that the object is within the distance range, the control means prevents the detection signal output from the variable amplification means from being saturated. The gain is switched and adjusted. On the other hand, the processing means identifies the object based on the newly output non-saturation detection signal according to the presence / absence of its time variation.

[0006]

According to the present invention, the gain of the variable amplifying means is adjusted according to the preset distance range. By setting this gain to a high value, the detection signal output from the variable amplification means always reaches the saturation level even if an object having a low surface reflectance enters the range of the monitoring area.
The processing means can determine that the object exists at a position within the distance range by identifying the saturation level. Therefore, position information can always be stably obtained without depending on the surface reflectance of the object, and erroneous detection can be prevented. Furthermore, it is possible to determine whether the object is a moving human body or a stationary object by readjusting the gain. That is, the gain of the variable amplification means is reduced to the non-saturation level, and the detection signal is processed again. If the level of the non-saturation detection signal fluctuates within a certain period of time, it can be identified as a moving human body, and conversely, if there is no level fluctuation within a certain period of time, it can be identified as a stationary article. The photoelectric object sensor having such an action can be utilized in various fields of application.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing a specific configuration example of a photoelectric object sensor according to the present invention. As shown in the figure, the photoelectric object sensor includes a light emitting means 1 and projects incident light 2 onto a predetermined monitoring area in front. In this example, the light emitting means 1 comprises a light projecting lens 3, a light emitting element 4, and a drive circuit 5. The drive circuit 5 drives the light emitting element 4 including an LED or the like by high frequency modulation. The light emitted from the light emitting element 4 is focused into a beam by the light projecting lens 3, and the incident light 2 is projected toward the front monitoring area. Further, it is provided with a light receiving means 6 and receives the reflected light 7 returning from the monitoring area and outputs an electric signal according to the amount of the light. In this example, the light emitting means 6 is composed of a condenser lens 8 and a light receiving element 9 composed of a photodiode, a phototransistor or the like.

The photoelectric object sensor further comprises a variable amplifying means 10, which amplifies the electric signal with a given gain and outputs a detection signal. In this example, this variable amplification means 1
Reference numeral 0 is composed of an operational amplifier 11 and a plurality of gain adjusting resistors connected between its input and output terminals. In addition,
The input terminal of the operational amplifier 11 is connected to the output terminal of the light emitting element 9 via a capacitor and a resistor, and the external noise is removed by receiving only the high frequency modulation component excluding the DC component contained in the electric signal. . Further, the processing means 12 is provided to process the detection signal and output the position information of the object existing in the monitoring area. In this example, the processing means 12 is composed of a microcomputer and receives a detection signal from the operational amplifier 11 via the A / D converter 13.

A control means 14 is provided as a feature of the present invention, and the gain of the variable amplification means 10 is adjusted according to a preset distance range. The variable amplifying means 10 thus adjusted in gain outputs a saturation detection signal when the object is within the set distance range in the monitoring area, and outputs a non-saturation detection signal when the object is outside the set distance range. Thereby, the processing means 12 can obtain the position information of the object. In this example, the control means 14 is composed of a switching transistor 15 connected in series to a plurality of resistors provided for gain adjustment. Each switching transistor 15 is a field effect type, its source terminal is connected to the input terminal of the operational amplifier 11, its drain terminal is connected to the corresponding gain adjusting resistor, and its gate electrode is the control of the microcomputer constituting the processing means 12. It is connected to the terminal.
This microcomputer controls switching of one or more specific switching transistors 15 according to the input set distance range information so that a desired gain can be set. For example, the gain adjustment is performed so that the detection signal reaches the saturation level even if the surface reflectance of the object located within the set distance range is a low value of about 9%.

Further, when the saturation detection signal output from the variable amplification means 10 determines that the object is within the set distance range, the control means 14 outputs from the variable amplification means 10 based on the switching signal from the microcomputer. The gain is switched to a lower one and adjusted so that the detected signal is not saturated. After that, the microcomputer discriminates whether the object is a human body or an article based on the non-saturation detection signal newly output from the variable amplification means 10 according to the presence or absence of the time fluctuation. The light receiving means 6 incorporated in the photoelectric object sensor according to the present invention has extremely high sensitivity, and the level of the non-saturation detection signal fluctuates sensitively even when the human body moves, for example, by 1 cm. On the other hand, the level of the non-saturation detection signal does not fluctuate over time because the stationary article does not move.

Next, an application example of the photoelectric object sensor according to the present invention will be described with reference to FIG. In this example, the photoelectric object sensor is mounted on an automobile and is used for automatic control of a vehicle air conditioner. However, it goes without saying that the application range of the photoelectric object sensor according to the present invention is not limited to this. The photoelectric object sensor 21 is embedded in the door on the passenger seat 22 side. Passenger seat 22 and driver seat 2
The incident light 24 is projected toward the monitoring area including 3. In this example, the set distance range is determined from the door on the passenger seat side to the center of the passenger seat. Therefore, the photoelectric object sensor 21 outputs a saturation detection signal when the object is located within this set distance range. With this setting, the presence or absence of the driver and the assistant is automatically determined, and the air conditioner switching control is executed. For example, when it is determined that there is a person in the passenger seat 22, the air conditioner on the passenger seat side is driven,
On the contrary, when the assistant is absent, the operation of the air conditioner is stopped.

Next, the operation of the automatic air conditioner control system shown in FIG. 2 will be described in detail with reference to the flowcharts of FIGS. 3 and 4. First, the key lock is turned on in step S1. That is, the driver accesses the door on the driver's side from the outside of the automobile. Next, in step S2, in response to this key lock closing operation, the photoelectric object sensor starts operating to read the background portion. In the setting of FIG. 2, the background portion is the inner surface of the door on the driver's seat 23 side. The reflected light from the inner surface of the door is received, a background detection signal is generated, and the background data B corresponding to the level is created by the microcomputer. Next, in step S3, it is determined whether the air conditioner switch has been turned on. The air conditioner switch is not always turned on depending on the ambient temperature situation and the like. The on-vehicle air conditioner enters the standby state when the air conditioner switch is turned on.

When the vehicle-mounted air conditioner is in the standby state, the object is checked in the following step S4. That is, the photoelectric object sensor 21 receives the reflected light from the monitoring area and outputs a detection signal according to the amount of received light, and the built-in microcomputer generates object data R according to the level of the detection signal. In this object check, it is determined whether the background data B sampled previously and the object data R are not equal. When some object is present in the monitoring area that penetrates the passenger seat 22 and the driver seat 23, the background data B and the object data R are necessarily not equal. Therefore, it is determined in step S5 that there is an object. At this point, no information about the position of the object has been obtained yet. In other words, it is not specified whether the object is on the passenger seat 22 side or on the driving 23 side. In addition, it is not specified whether the object is a human body or an article. In particular, on the passenger seat 22 side, articles may be placed instead of the human body.

Next, in step S6, it is determined whether the previously sampled object data R is at the saturation level.
When the saturation level is not reached, the object intervening in the monitoring area is regarded as outside the set distance range that covers the passenger seat 22. Therefore, in step S7, it is determined that the human body is located on the driver's seat side. The object located in the driver's seat is automatically regarded as a human body. On the other hand, step S
When the determination result of 6 is the non-saturation level, it is determined in step S8 that the object is located on the passenger seat side.

In this case, the process proceeds to step S9, and the gain of the variable amplifier incorporated in the photoelectric object sensor is adjusted. Specifically, the gain is switched to a lower value so that the detection signal output from the variable amplifier is not saturated. Next, in step S10 of FIG. 4, sampling is performed again to obtain object data. This sampling is repeated at predetermined time intervals. During this time, the microcomputer determines whether the object data is constant. If the object data fluctuates, the process proceeds to step S11 and it is determined that the human body is placed on the passenger seat side. Therefore, in this case, the air conditioner on the passenger side is turned on in step S12. At the same time, the air conditioner on the driver's side is also turned on. On the other hand, when it is determined that the object data has not changed, the process proceeds to step S13, and the object located on the passenger seat side is regarded as a stationary article. Therefore, in step S14, the air conditioner on the passenger side is turned off. In the above description, when setting the saturated region and the non-saturated region, the gain of the variable amplifier is manually adjusted. However, instead of this, a desired gain may be set by performing a calculation process by a microcomputer based on the background data.

Finally, FIG. 5 shows a modification of the air conditioner automatic control system shown in FIG. In this modified example, the photoelectric object sensor 21 is arranged at the center of the front-side vehicle interior ceiling, and the incident light 24 is projected along a monitoring area that penetrates the passenger seat 22. In this case, the set distance range is determined by a predetermined distance from the back of the passenger seat 22. According to this arrangement, the presence or absence of an object or the position of the passenger seat 22 can be detected regardless of the driver's seat 23, and it can also be detected whether the object is a human body or an article.

[0017]

As described above, according to the present invention, the gain of the variable amplifying means is adjusted in accordance with the preset distance range, and when the object is saturated within the set distance range in the monitoring area. The position information of the object is obtained by outputting the detection signal and outputting the unsaturated detection signal when the object is out of the set distance range. Therefore, the object can be stably detected without depending on the surface reflectance of the object, and the malfunction can be prevented. Further, by performing the gain adjustment again and lowering the detection signal to the non-saturation level, it is possible to distinguish between the article and the human body, so that there is an effect that the range of use is expanded.

[Brief description of drawings]

FIG. 1 is a block diagram showing a specific example of a photoelectric object sensor according to the present invention.

FIG. 2 is an explanatory diagram showing an application example of the photoelectric object sensor shown in FIG.

FIG. 3 is a flowchart for explaining the operation of the application example shown in FIG.

FIG. 4 is a flowchart for explaining the same operation.

5 is an explanatory diagram showing a modification of the application example shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 light emitting means 2 incident light 6 light receiving means 7 reflected light 10 variable amplification means 12 processing means 14 control means

Claims (2)

[Claims] 1. A light emitting means for projecting incident light to a predetermined monitoring area, a light receiving means for receiving reflected light returning from the monitoring area and outputting an electric signal according to the amount of the light, and providing the electric signal. A photoelectric object sensor comprising variable amplification means for amplifying a detected signal and outputting a detection signal, and processing means for processing the detection signal and outputting position information of an object existing in a monitoring area, which is preset. Control means for adjusting the gain of the variable amplifying means in accordance with the specified distance range, and outputs a saturation detection signal when the object is within the distance range in the monitoring area while the object is outside the distance range. A photoelectric object sensor characterized by obtaining position information of an object by outputting a non-saturation detection signal. 2. When it is determined that the object is within the distance range by the saturation detection signal output from the variable amplification means,
The control means switches and adjusts the gain so that the detection signal output from the variable amplification means is not saturated, and the processing means is based on the newly output non-saturation detection signal and determines whether or not the object changes depending on the time variation. 2. The photoelectric object sensor according to claim 1, wherein