JPS59105634A - Device for adjusting exposure - Google Patents

Abstract

PURPOSE:To simplify the adjusting process and improve the productivity of an exposure adjusting device, by installing a voltage generating circuit, photodetector, automatic exposure voltage control circuit, amplifier, differential amplifier, and light emission control circuit. CONSTITUTION:The output of a manual setting circuit is impressed upon the noninverted input terminal of an operational amplifier OP1 and the inverted input terminal is connected with the output of the operational amplifier OP1. The output of the operational amplifier OP1 is connected with the noninverted input terminal of another operational amplifier OP2. The noninverted input terminal of the operational amplifier OP2 is connected with the inverted input terminal of the operational amplifier OP2 through a photodiode PD (connecting an anode to the noninverted input terminal) which acts as a photodetector and with the output terminal of an operational amplifier OP3 through resistances R1 and R2. The inverted input terminal of the operational amplifier OP2 is connected with the noninverted input terminal of the operational amplifier OP3 through a resistance R3 and variable resistance VR1. Moreover, the output of the operational amplifier OP2 is also connected with the noninverted input terminal of the operational amplifier OP3. The inverted input terminal of the amplifier OP3 is connected with the connecting point of the resistance R1 and R2 and its output is inputted into a DC amplifier 8.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an exposure amount adjustment device applied to an image forming apparatus, such as an electronic copying machine.

[Technical background of the invention and its problems]

In conventional electronic copying machines and the like, the amount of exposure is adjusted by switching the voltage applied to the exposure light source. That is, the exposure amount is adjusted by switching the reference voltage of a voltage stabilizing circuit (hereinafter referred to as a lamp regulator) of the exposure power source. The lamp regulator has a function of automatically controlling the exposure voltage to an optimal value according to the density of the original (hereinafter referred to as an automatic exposure device), which detects the amount of light reflected from the original using a light receiving element such as a photodiode, A method has been used in which the reference voltage is automatically controlled according to the amount of light received.

However, in this type of circuit configuration, there are always variations in the sensitivity of the light-receiving element and the optical system, so it is necessary to make adjustments using a volume or the like in order to absorb the variations. However, recent electronic copying machines require a multi-magnification function, and the optical system is different for each magnification, so a volume is also required to compensate for this, which is very complicated and reduces productivity. There was a problem with it being bad.

Here, the above problem will be explained in detail using FIG. 1 and FIG. 2.

FIG. 1 is a circuit diagram of a conventional exposure amount adjusting device, in which an exposure power source 2 is connected to a commercial AC power source 1 via a bidirectional thyristor 6. As shown in FIG.

A voltage proportional to the voltage across the exposure power source is formed in the pseudo load circuit 4, and the waveform shaping circuit 6 converts the voltage into a DC voltage approximately proportional to the effective value of the exposure light source voltage. This DC voltage is compared and amplified with a reference voltage by the differential amplifier 7, and the trigger pulse generation circuit 5 generates a trigger pulse synchronized with the power supply frequency by the output of the differential amplifier. The conduction angle of the bidirectional thyristor 6 is controlled by this trigger pulse, and even if the commercial AC power source fluctuates, the voltage of the exposure power source is kept constant. A block 14 surrounded by a broken line is a reference voltage generation circuit.

The portion excluding the commercial power source 1 and the exposure power source 2 is referred to as voltage setting means.

Figure 2 has an automatic exposure function and has four copy magnification modes (
2 is a circuit diagram of a specific example of a reference voltage generating circuit 14 in a jH'e amount adjusting device for an electronic copying machine equipped with, for example, equal magnification, one stage of enlargement, and two stages of reduction. In the figure, 29.40 is a semiconductor switch that is switched depending on the copy magnification mode, and 10.
is a semiconductor switch for switching between automatic exposure and manual setting.

These semiconductor switches are, for example, Toshiba's CMO5I.
CTC4Q5'lBP can be used. The operational amplifier 46 is for setting the automatic exposure voltage, and the photodiode 20 is for receiving reflected light from the original, and the amount of light received differs depending on the density of the original, and the light receiving current also differs. The operational amplifier 46 outputs a voltage obtained by subtracting the light-receiving current of the photodiode 20 and the voltage drop due to the resistor and semi-fixed resistors (for example, 21 and 22) from its positive phase input voltage. Therefore, in the case of a high-density original, the amount of light received by the photodiode 20 is small, so the light-receiving current is also small, the output voltage of the operational amplifier 46 becomes slightly larger, and the exposure voltage also rises. As a result, the copy density becomes slightly lower and a proper copy can be obtained. Furthermore, for a low-density original, the development that is completely opposite to that described above occurs, so the exposure voltage is lowered and a proper copy can be obtained. On the other hand, the manual setting circuit 12 consists of resistors 16, 17, 18, 19 and a volume 60 on the control panel.
The voltage obtained by dividing the voltage supplied by these resistors is
This is the output voltage of the manual setting circuit 12. The output voltage of the operational amplifier 46, that is, the output voltage of the automatic exposure voltage control circuit 11 and the output voltage of the manual setting circuit 12, is connected to the semiconductor switch 1.
The voltage selected at 0 and amplified by the DC amplifier 8 becomes the reference voltage.

By the way, the volumes 33, 35, 37, and 39 are for correcting variations between individual machines (for example, variations in sensitivity of photosensitive drums, variations in 9-element systems, etc.) and differences in optical systems for each copying magnification. Volumes 22, 24, 26.
This is to correct variations in the 28f'i photodiode 20 and differences in optical systems for each copying magnification. However, although the differences in the optical system for each copying magnification are relatively regular, the circuit configuration shown in Figure 2 has the disadvantage that the same adjustment must be made for each copying magnification. was there.

[Object of the Invention] The present invention has been made based on the above-mentioned circumstances, and it is an object of the present invention to provide an exposure amount adjustment device that can simplify the adjustment process and improve productivity.

[Summary of the invention]

In order to achieve the above object, the present invention provides an image forming apparatus in which a document is irradiated with an exposure lamp, and the original obtained at that time is guided to a photoreceptor to expose 19 images. a voltage generation circuit that generates a voltage corresponding to the original, a photodetector that detects light from the document and converts it into an electrical signal, and a photodetector that converts a predetermined amount of electricity into an amount of electricity that is proportional to the signal from the photodetector. Automatic N consisting of a circuit to reduce the amount and a circuit to amplify the amount
A photovoltage control circuit, an amplifier for amplifying the output of the automatic exposure voltage control circuit, and comparing and amplifying the output of the amplifier and the output of the voltage generation circuit [Embodiment of the Invention] The present invention includes a basic block The diagram is similar to Figure 1, but
The feature is that the self-wJB source voltage control circuit therein has a basic configuration as shown in FIG.

FIG. 6 shows the basic configuration of the automatic fog light voltage control circuit. In the figure, the output of the manual setting circuit described above is applied to the non-inverting input terminal of the operational amplifier OP1, and the inverting input terminal is connected to the output of the operational amplifier OP1. The output of the operational amplifier OP1 is connected to the non-inverting input terminal of the operational amplifier OF2. The non-inverting input terminal of this operational amplifier OP2 is connected to a photodiode PD as a photodetector.
(the anode is connected to the non-inverting input terminal) and the operational amplifier 0/) 3 via the inverting input terminal and resistors R1 and R2.
Connected to the output terminal of the The inverting input terminal of the operational amplifier OP2 is connected to the non-inverting input terminal of the operational amplifier OP2 via a resistor R3 and an oJ variable resistor VR1. Further, the blade of the operational amplifier OP2 is also connected to the non-inverting input terminal of the operational amplifier oP6. The inverting input terminal of the operational amplifier OP5 is connected to the connection point between the resistors R1 and R2, and its output is input to the DC amplifier 8 described above. This circuit is functionally an amplifier that generates a predetermined voltage V1. Pl, a subtraction amplifier □P2 that subtracts a voltage proportional to the cutting edge of the photodetector PD from this predetermined voltage Vl, and an amplifier oP6 that amplifies the subtraction result.
It is composed of the following.

Next, the operation f of the automatic exposure voltage control circuit will be explained.

In FIG. 3, operational amplifiers OF 1 , OF2 , O
Let the output voltage of F2 be VltV2*Vs, the light receiving current of photodiode pD be Ip, and the current flowing through resistor R1 be II. At this time, since the operational amplifier OF2 has exactly the same function as the operational amplifier 46 in FIG. 2 described above, the output voltage V2 of the operational amplifier OP2 is as follows.
It is expressed by the following formula.

V2 = VI IP (R5 + VR1) ...
...(1) This output voltage V2 is the operational amplifier OP
5 is applied to the non-inverting input terminal. Here, due to the characteristics of the operational amplifier, the non-inverting input potential and the inverting input potential should be equal, so the inverting input potential of the operational amplifier 07)3 also becomes v2. Therefore, the current Il flowing through R1
is expressed by the following equation.

11=(VI V2)/R1・・・・・・・・・(2
) Also, since the human power impedance of the operational amplifier is infinite, this current I! flows directly to the resistor R2 side. Therefore, the output voltage V3 of the operational amplifier OP5 is expressed by the following equation.

Vs ”” V2 1 t ” R2・・・・・・・・・
・(3) and above (7) Type 3 Niyo! 11, Val'j, Vt
, IP, R1, R2, R').

It is expressed by the following equation using VR1f.

Vs = Vt IP ・(R6+VR1) ・(R
1+R2)/7?1 ・'・”(4) Therefore, the resistance R
1 or R2 for each copying magnification, it is possible to correct differences in the optical system for each copying magnification. This example is explained in the fourth example.
As shown in the figure. In the figure, it is assumed that the 3Nth resistor R2 is formed by connecting four stages of resistors R2α to R2d, each having a different resistance value, in parallel.

Suitable selection is made using semiconductor switches SW1 to SW4. Furthermore, variations in photodiode pD can be adjusted by volume VR1. As described above, this embodiment circuit requires only one volumetric switch and one semiconductor switch, and has a relatively simple configuration that simplifies the adjustment process and improves productivity without increasing costs. I can figure it out.

As another example, as shown in FIG. 5, the resistors R1f in FIG. 4 each have a different resistance value.
-R1d are connected in four stages in parallel, and semiconductor switches SF5 to SWs are provided.

Also, as shown in Figure 6, connect two resistors continuously and connect them to four resistors.
It is also possible to arrange the stages in parallel and provide semiconductor switches SFα to 5IVd for switching at the connection points of each continuous connection. Also, as shown in FIG. 7, in place of the resistor R3 and the volume VR1 in FIG. 6, a resistor R6t1. ~R3d to 4
A semiconductor switch SIP'e-5IVh is provided to connect the stages in parallel and switch each resistor.

The resistor R2 and the volume VR1 may be connected in series. It should be noted that recent electronic copying machines are capable of copying at multiple magnifications (for example, full size, enlarged 1
4-stage switching configuration in FIGS. 4 to 7 of the present invention may be increased according to the number of stages.

〔Effect of the invention〕

As described in detail above, according to the present invention, the circuit is simpler than the conventional device, and there is no increase in cost, and the adjustment process can be simplified and productivity can be improved. equipment can be provided.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a conventional device, Fig. 2 is a specific circuit diagram of a reference voltage generation circuit of a conventional device with a multi-magnification function, and Fig. 6 is an automatic exposure voltage control used in the device of the present invention. A basic circuit diagram of the circuit, FIG. 4 is a circuit diagram of one embodiment of the automatic exposure voltage control circuit used in the apparatus of the present invention, and FIGS. 5 to 7 are other implementations of the automatic exposure voltage control circuit of the present invention. FIG. 3 is an example circuit diagram. 2... Source for exposure yC, 11... Automatic exposure voltage control circuit, 12... Manual setting circuit, 14...
Reference voltage generation circuit, 15...DC current, OPl,
OF2. OF2...Operation amplifier, PD...Photodiode. Figure 5 Figure 6

Claims (2)

[Claims] (1) In an image forming apparatus # that exposes an image by irradiating an original with an exposure lamp and guiding the source obtained at that time to a photoreceptor, a voltage corresponding to the voltage applied to the exposure 5e rung is generated. a voltage generation circuit, a photodetection device that detects the source from the original and converts it into an electrical signal, a circuit that reduces an amount of electricity proportional to the signal from the photodetection device from a predetermined amount of electricity, and the reduction. an automatic exposure voltage control circuit consisting of a 4+f circuit that amplifies the amount;
an amplifier that amplifies the output of the automatic voltage control circuit, a differential amplifier that compares and amplifies the output of the amplifier and the output of the voltage generation circuit, and the exposure according to the output signal of the differential amplifier. An exposure amount adjustment device comprising: a control circuit for controlling light emission of a lamp. (2) In the automatic exposure voltage control circuit, the amount to be subtracted from the predetermined amount of electricity and the amplification amount of the amplifying circuit are changed by switching for each exposure magnification of an image forming apparatus having a multi-magnification function. Claim 1:
Dew M as described in section 1. Amount adjustment device.