JPS60123967A - Analog multiplier circuit - Google Patents

Abstract

PURPOSE:To simplify the constitution and reduce the cost of an analog multiplier circuit, by supplying an input analog signal to the reference voltage input terminal of an digital-to-analog converter and a digital signal to be multiplied to the digital signal input terminal of the converter. CONSTITUTION:Correcting value information read out from a ROM10 is introduced to the digital signal input terminal of a D/A converter 20 and, at the same time, an analog signal IS before multiplication correction is introduced to the full scal adjustment terminal BI of the converter 20. An analog output signal corresponding to the value which is equal to the analog signal IS multiplied by the correcting value information is outputted from the output terminal OUT of an output arithmetic amplifier OP as a corrected analog signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a digital correction method predetermined for an analog signal, such as a multiplication circuit used for shading correction in an optical information reading device, for example. The present invention relates to an improvement in a multiplication circuit that multiplies signals and outputs the multiplication result as a corrected analog signal.

[Technical background of the invention]

In general, in optical information reading devices such as the facsimile reading device Le, the illumination of the light source and the amount of light passing through the optical system such as the lens change depending on the position, and the light receiving characteristics of the optical sensor such as the solid-state sensor vary depending on the distance between the elements. Since there are variations in the values, it is necessary to correct these to obtain a positionally uniform read signal. To avoid this, conventional countermeasures have been taken, such as installing a received light amount correction member called a shading plate in the light receiving path to the optical sensor, or correcting the output signal by varying the load resistance of the optical sensor for each element. However, as a correction means that has received attention in recent years, there is a method that corrects the output signal of an optical sensor by multiplying it by a preset correction coefficient. 1st
The figure shows an example of its configuration. This circuit first converts the photodetection signal obtained from each element of the optical sensor into a digital signal using an analog-to-digital conversion circuit (A/D) 1.
Read-only memo with this digitized signal! I (
Rou) The digital multiplier 3 multiplies the correction coefficient information written in z, and the multiplication result is converted into a digital analog signal by the digital-to-analog conversion circuit (D/A) 4 to produce the corrected signal. The device is configured to obtain a photodetection signal. With this type of circuit, it is possible to compensate for positional non-uniformity in the illumination intensity of the light source and the optical system's original slippage, as well as for each light-receiving element. It has the advantage of being able to perform good correction.

[Problems with the Background Art] However, such conventional circuits first convert the analog signal output of the optical sensor into a digital signal, and then convert it back to an analog signal after multiplication. Since it requires a D/A 11 conversion circuit 4 and generally uses an expensive and complicated digital multiplier, it has the disadvantage that the configuration is extremely complicated and expensive.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an inexpensive analog multiplication circuit with a simple configuration.

[Summary of the invention]

In order to achieve the above object, the present invention provides a digital-to-analog conversion circuit that converts an input digital signal into an analog signal according to a standard voltage, and inputs an input analog signal to a standard voltage input terminal of the digital-to-analog conversion circuit. At the same time, a digital signal to be multiplied is supplied to the digital signal input terminal, and an analog signal corresponding to the multiplication value of the input analog signal and the digital signal is obtained from the analog signal output terminal. This eliminates the need for a D conversion circuit or an expensive digital multiplier.

[Embodiments of the invention]

FIG. 2 is a circuit configuration diagram of a multiplication circuit in an embodiment of the present invention, and 10 in the figure is a read-only memory (Rou).
, 2o indicate digital-to-analog conversion circuits (D/A 9-conversion circuits), respectively. The ROIJ 70 stores, for example, shading correction values of an optical information reading device as multiplication information as 16 6-bit digital reports. It is designed to read out.

On the other hand, the D/A conversion circuit 20 converts a 6-bit (inari code) digital signal into an analog output voltage signal Kf, and has a so-called full scale adjustment terminal BI for specifying a reference voltage at the time of conversion. In addition, V-, V
+ indicates the power supply voltage, input terminal, V/U indicates the bipolar/unipolar switching input terminal, "Skill" indicates the current addition input <111^, and SL indicates the output voltage range (full scale range) setting terminal.

Then, the A/A conversion circuit 20 inputs the correction value information read from the ROVLIO to the digital signal input terminal (6 bits), and inputs the analog signal IS before multiplication correction to the full scale adjustment terminal BI. introduced,
An analog output signal corresponding to the value obtained by multiplying the analog signal Is by the correction value information is outputted from the output terminal OUT of the output operational amplifier OP as an analog signal of Sodehigo.

With such a configuration, the correction value information corresponding to the position 11η of the optical sensor is sequentially output from the ROM 10 in synchronization with the scanning control operation of the optical sensor →
/A conversion circuit 20 digital signal input terminal M3B.

2nd, 3rdl 4t, h l 5tb l LS
When the correction value information is converted to an analog value, it is converted as if it were converted into an analog value according to the magnitude of the light reception output signal (analog signal) of the sensor S supplied to the full scale adjustment terminal BI. A coefficient is assigned, and as a result, an analog signal corresponding to the multiplication value of the received light output signal IS and the digital correction value information is output from the output terminal OUT of the output operational amplifier OP. . Therefore, in order to uniformize the illuminance of the light source, the positional non-uniformity of the amount of light passing through the optical system, and the non-uniformity of the light-receiving characteristics between each element of the optical sensor, the correction value information is If it is set in advance and stored in the ROM, the light receiving output of the optical sensor can be corrected for each light receiving element and made uniform overall. In other words, analog signals can be updated and updated in exactly the same way as the circuit shown in FIG.

Moreover, in this embodiment, since the D/A conversion circuit 2θ is configured to operate as if it were a multiplier, it is possible to eliminate the need for an A/D conversion circuit or a digital multiplier with a complicated configuration. As a result, the 4/+4 configuration of the circuit can be greatly simplified and an inexpensive circuit can be provided.

Note that the present invention is not limited to the above embodiments,
For example, it can be used not only to correct the received light output of an optical sensor, but also to correct the detected output of a pressure sensor or other sensors, and even when simply multiplying an analog signal and a digital signal. can also be applied. As an application example of the present invention, an analog signal is supplied to the quasi-voltage input terminal of an A/D conversion circuit, and the quasi-analog signals are multiplied by each other to obtain the result as a digital signal. Good too.

〔Effect of the invention〕

As described in detail above, the present invention provides a digital-to-analog conversion circuit that converts a reference voltage IEK, that is, an input digital signal, into an analog signal, and supplies an input analog signal to the input terminal of the digital-to-analog conversion circuit. At the same time, a digital signal to be multiplied by A is supplied to the digital signal input terminal, and an analog signal corresponding to the multiplication value of the analog signal and the digital signal is obtained from the analog signal output terminal. .

Therefore, according to the present invention, it is possible to provide an analog multiplication circuit with a simple configuration and low cost.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a conventional multiplication circuit;
The figure is a circuit configuration diagram of a multiplication circuit in one embodiment of the present invention. 10...ROIJ, 20...D/A conversion circuit.

Claims (2)

[Claims] (1) In an analog multiplier circuit that multiplies an input analog signal by an input digital signal and outputs the multiplication result as an analog signal, specify the reference voltage of the digital-to-analog conversion circuit that converts the digital signal input into an analog signal according to the reference voltage. The input analog signal is supplied to a terminal of the terminal, the input digital signal is supplied to a digital signal input terminal of the digital-to-analog conversion circuit, and the input analog signal and the input signal are input from the analog signal output terminal of the digital-to-analog conversion circuit. An analog multiplication circuit characterized in that it outputs an analog signal corresponding to a multiplied value with a digital signal. (2) The input analog signal is supplied from an optical sensor of the facsimile reading device, and the input digital signal is supplied from a read-only memory that stores correction value information for the optical sensor. An analog multiplication circuit according to claim (1), characterized in that: