JPH0522168B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a display circuit, and particularly to a level detection circuit that displays an analog input signal by the amount of light.

(2) Background of the Technology Devices using optical sensors, such as barcode readers, use display devices that display whether or not the sensor has correctly detected a specific level.
This is for displaying to the user whether or not the sensor is operating, and is an effective display for the user. These displays are used not only in the above-mentioned barcode reader but also in various devices such as optical detection switches.

(3) Prior Art and Problems Conventionally, most of the above-mentioned displays have used light emitting diodes or lamps. FIG. 1 shows a circuit diagram of the conventional display device.

The output of sensor S is input to amplifier AMP and amplified. The amplified signal is input from the amplifier AMP and added to the positive phase input of the comparator CMP. On the other hand, since the reference voltage Vref is input to the negative phase input of the comparator CMP, the output of the comparator CMP becomes a high level when the output voltage of the amplifier AMP is higher than the reference voltage Vref, and becomes a low level when it is lower. comparator
Since the output of the CMP is input to the display element whose one end is grounded, the display element D emits light when the output is at a high level, and does not emit light when the output is at a low level. Light emitting diodes, lamps, etc. are used as these display elements.

Furthermore, the output of the comparator CMP is outputted from the output terminal OUT as a level detection signal.

In the conventional method described above, the display element emits light when the voltage generated by the sensor S exceeds a specific level, and does not emit light when the voltage does not reach the specific level. In other words, a binary display is performed.

Since this conventional display only indicates whether light is emitted or not, it cannot indicate how the sensor should be moved to obtain the best reading in, for example, a bar code reader.

Furthermore, the same applies to opposing type optical detection switches, which need to be installed so that the maximum amount of light from the light emitting section enters the light receiving sensor. However, in conventional circuits, it is not possible to determine the maximum amount of incident light depending on whether the display element is turned on or off, and it is necessary to measure it using another measuring device at the time of installation.

(4) Purpose of the Invention The present invention is intended to solve the above-mentioned problems, and its purpose is to emit light in response to a level above a specific level, and further to emit light in response to a level above a certain level, and to emit light in response to a level above a specific level. An object of the present invention is to provide a level circuit in which the amount of light emitted from a display element changes.

(5) Structure of the Invention The present invention is characterized by a sensor that converts physical changes in the external world into electrical quantities, an amplifier that linearly amplifies the strength of the output of the sensor, and the output voltage and reference of the amplifier. A comparator that compares a specific voltage as a voltage, a display element that is driven while changing the amount of light with a drive signal based on the output of the amplifier, and a switch element that switches the display element. The switch element is controlled in accordance with changes in the output to cause the display element to emit or not emit light, and when the display element is emitting light, the amount of light emitted is proportional to the change in the detection output of the sensor. The level detection circuit is characterized in that the level detection circuit is capable of changing depending on the level.

(6) Examples of the invention The present invention will be described in detail below using the drawings.

FIG. 2 is a circuit diagram of an embodiment of the present invention.
The sensor S is an element that converts an external physical change into an electrical quantity, such as a photodiode. The output of that sensor S is applied to an amplifier AMP.
The output of the amplifier AMP is input to one terminal of the display element D via the driver DV and also to the comparator.
Adds to CMP positive phase input. The reference voltage Vref is input to the negative phase input of the comparator CMP. The output of the comparator CMP is applied to the drive input of the electronic switch SW to drive the switch. Furthermore, the output of the comparator CMP is input to a device (not shown) as a level detection signal. The other end of the display element D is grounded via an electronic switch SW.

The output of sensor S is input to amplifier AMP and amplified. Although it varies depending on the output voltage of the sensor S, for example, when converting a small amount of light into electricity, an amplifier AMP with a large amplification degree is required. The output of this amplifier AMP is added to the positive phase input of the comparator CMP, and is compared with the reference voltage Vref in the comparator CMP. When the output voltage of the amplifier AMP is higher than the reference voltage Vref, the output of the comparator CMP becomes high level and turns on the electronic switch SW. On the other hand, the output of the amplifier AMP is input to the driver DV, where it is converted to a voltage level that drives the display element and input to the display element. Since the other end of the display element is grounded via the electronic switch SW, the amplifier AMP is connected to the reference voltage Vref as described above.
When the output voltage is high, the electronic switch SW is turned on to display on the display element D that the detection level of the sensor S is higher than a specific level. And vice versa
When the output of AMP is lower than Vref, SW is off, so display element D does not display anything. That is, for example, if the display element D is a light emitting diode, it will not emit light. The present invention changes the amount of light from a light emitting diode, for example, when the amount of light is above a certain level. i.e. amplifier
AMP, driver DV is the amplification amount and driver with linearity, and the amplifier is
When the output of the AMP is high, the display device D emits light in an amount proportional to the output of the sensor S.

FIG. 3 is a characteristic curve diagram showing the relationship between the output of the sensor S and the output of the display element, that is, the amount of light emitted when a light emitting diode is used, for example, in the conventional example and the embodiment of the present invention. Curve 1 shows the conventional display only at a specific level, Curve 2 shows the display output proportional to the sensor output, and Curve 3 shows the display output according to the embodiment of the present invention. As is clear from curve 3, according to the embodiment of the present invention, when the voltage exceeds a certain level, the displayed output increases in proportion to the output voltage of the sensor S, and when it is below that level, the displayed output becomes zero. . In FIG. 3, curves 2 and 3 also indicate that when the sensor output exceeds a specific value, the displayed output remains constant, which means the maximum value of the displayed output. This maximum value is determined by the maximum output of the display element D or the maximum drive of the driver D.

FIG. 4 is a circuit diagram showing an example of application of the present invention to an optical detection switch. The optical detection switch consists of a light emitting part and a light receiving part, and the light receiving part has the structure shown in FIG. Note that the electronic switch SW in FIG. 2 is a transistor Tr, and the display element D is a light emitting diode LED. The light emitting section T of the optical detection switch is, for example, a light emitting element such as an infrared lamp, and the emitted light is turned into a beam by a lens or the like and is irradiated onto the sensor S of the light receiving section.
When the sensor S is illuminated by the light emitted from the light emitting section T, the output of the sensor S becomes large and is amplified by the AMP and input to the comparator CMP, so that the output of the comparator CMP becomes high level. Its output is a transistor Tr
The transistor Tr is turned on because it is input to the base of the transistor Tr.

As a result, the LED emits light according to the output of the driver DV. The light emission of the LED is proportional to the output of the driver DV.
Both DV outputs a voltage proportional to the input, so
When the sensor S is irradiated with more than a certain amount of light,
LEDs emit light in proportion to the amount of irradiation. The optical detection switch outputs a high level to the output terminal OUT as a detection signal when, for example, infrared rays emitted from the light emitting section T are blocked by a moving object such as an object. This detection switch detects that the light is blocked when the amount of infrared light emitted decreases, so the light emitted from the light emitting part T is transmitted to the sensor S.
It is desirable to install it so that the maximum input is possible.
In the case of the present invention, since the LED emits light in proportion to the amount of light incident on the sensor S, it is sufficient to install it at the point where the LED emits the most light, and no other measuring device is required.

(7) Effects of the Invention As detailed above, according to the present invention, a light emitting element is started with a sufficient amount of light to overcome the brightness of the surroundings in which the display element is placed. Therefore, there is no possibility that the luminescent display will be overwhelmed by the brightness of the surroundings and the display of the display element will not be recognized or misidentified. Also,
When the display element is emitting light, the amount of light emitted is proportional to the change in the detection output of the sensor, so it can be seen with what margin the sensor is detecting. As a result, for example, it becomes possible to easily install a detection switch or the like at an optimal position without using a special measuring device or the like for measuring the amount of light received when installing an optical detection switch or the like. In addition, the user can find the best way to handle the sensor in a barcode reader, etc., such as how to tilt the sensor, by visually checking the amount of light emitted by the LED, etc.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram of a conventional display device, FIG. 2 is a circuit configuration diagram of an embodiment of the present invention, FIG. 3 is a characteristic curve diagram showing the relationship between sensor output and display output, and FIG. 4 is a diagram of the circuit configuration of an embodiment of the present invention. The circuit configuration diagrams of optical sensors applied to the implementation are shown respectively. S...Sensor, AMP...Amplifier, CMP...Comparator, D...Display element, SW...Electronic switch,
DV...driver, Tr...transistor.

Claims (1)

[Claims] 1. A sensor that converts physical changes in the external world into electrical quantities, an amplifier that linearly amplifies the strength of the output of the sensor, and an output voltage of the amplifier and a specific voltage that serves as a reference voltage. A comparator for comparison, a display element driven while changing the amount of light by a drive signal based on the output of the amplifier, and a switch element responsible for switching the display element. A switch element is controlled to cause the display element to emit or not emit light, and when the display element is emitting light, the amount of light emitted can change in proportion to a change in the detection output of the sensor. A level detection circuit characterized by: 2. The level detection circuit according to claim 1, wherein the switch element is a transistor, and the output of the comparator is input to the base of the transistor. 3. The level detection circuit according to claim 1 or 2, wherein the sensor is a photodiode.