JPH0555855B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an exposure control device for controlling the exposure amount of an exposure lamp used in an electronic copying machine capable of fine multi-step magnification change, such as in 1% increments.

[Technical background of the invention and its problems]

Conventionally, the most common means for switching the exposure amount in, for example, an electronic copying machine is to switch the voltage applied to an exposure lamp. The switching is performed by switching the reference voltage of an applied voltage stabilizing circuit (hereinafter referred to as a lamp regulator) of the exposure lamp. By the way, in a lamp regulator that has a function to automatically control the voltage applied to an exposure lamp to an optimum value according to the density of the original (hereinafter referred to as the automatic exposure function), the amount of light reflected from the original is detected by a light receiving element such as a photodiode. In many cases, the reference voltage is automatically controlled according to the amount of light received. In such a device, there are always variations in the sensitivity of the light-receiving element and the optical system, so an adjustment volume is required to absorb these variations. Also, when the operator manually sets the applied voltage of the exposure lamp,
There are always variations in the sensitivity of the photoreceptor drum,
Moreover, since they change over time, an adjustment volume is required to correct them. moreover,
In an electronic copying machine having multiple variable magnification functions, the optical system is different for each variable magnification, so a volume corresponding to the number of variable magnifications is required. Further, as the number of magnifications increases, the adjustment becomes extremely complicated, and this adjustment is especially impossible in electronic copying machines that perform fine multi-step magnification changes such as in 1% increments.

FIG. 1 schematically shows an example of such an exposure control device (lamp regulator), in which an exposure lamp 3 is connected to a commercial AC power source 1 via a bidirectional thyristor (triax) 2. Ru. Further, a feedback transformer 4 is connected to the exposure lamp 3. This feedback transformer 4 outputs a voltage corresponding to the voltage across the exposure lamp 3 when the triax 2 is turned on. The output voltage of this feedback transformer 4 is supplied to a waveform shaping circuit 5. The waveform shaping circuit 5 shapes the output of the feedback transformer 4 into a voltage corresponding to the effective value voltage of the exposure lamp 3 and outputs it. Here, the feedback transformer 4 and the waveform shaping circuit 5 constitute a voltage generating circuit 6 that generates a voltage corresponding to the voltage applied to the exposure lamp 3.
The output voltage of the waveform shaping circuit 5 is supplied to a comparator, for example, a differential amplifier 7, and the outputs of the general setting circuit 8 and the limiter circuit 9 are also supplied to the differential amplifier 7. The general setting circuit 8 is supplied via a switch 12 with the output of the automatic exposure voltage control circuit 10 or the manual setting circuit 11 corresponding to the amount of light from the exposure lamp 3 reflected by the original 16. Here, the general setting circuit 8, limiter circuit 9, automatic exposure voltage control circuit 10, manual exposure voltage setting circuit 11, and switch 12 constitute a reference voltage generation circuit 13. This reference voltage generating circuit 13 is controlled by a CPU (central processing unit) 15. The output of the differential amplifier 7 is then supplied to the trigger pulse generation circuit 14, and the timing of generating the trigger pulse is controlled. The output of this trigger pulse generation circuit 14 triggers the tri-attack 2.
The conduction angle of the feedback transformer 4 is controlled, and the output voltage of the feedback transformer 4 is similarly changed. Therefore, even if the voltage of the AC power supply 1 changes, the voltage applied to the exposure lamp 3 can be kept constant.

FIG. 2a shows an example of the configuration of the reference voltage generation circuit 13 in FIG. This shows the case where it has. In the figure, parts corresponding to those in the block diagram of FIG. 1 are given the same reference numerals. That is, resistors 37, 17, 18, and 19 are connected in series between the DC power supply terminal 36 and the ground, and the connection point between the resistors 37 and 17 is connected to the non-inverting input terminal (+) of the operational amplifier 20.
A photoelectric converter such as a photodiode 21 is connected between the inverting input terminal (-) and the non-inverting input terminal (+) of the operational amplifier 20 for receiving reflected light from the original.
is connected, and its output terminal is connected to a semiconductor switch (for example, TC 4052BP manufactured by Tokyo Shibaura Electric Co., Ltd.)1.
2 to the non-inverting input terminal (+) of the operational amplifier 23
It is also connected to the non-inverting input terminal (-) via the switch 24 ₁ , the variable resistor 25 ₁ and the resistor 26 ₁ . The series circuit of the switch 24 ₁ , the variable resistor 25 ₁ and the resistor 26 ₁ includes a series circuit consisting of the switch 24 ₂ , the variable resistor 25 ₂ and the resistor 26 ₂ , the switch 24 ₃ , the variable resistor 25 ₃ and the resistor 2
A _series circuit consisting of a switch 24 ₄ , a variable resistor 25 ₄ , and a resistor 26 ₄ are connected in parallel. A variable resistor 27 is connected in parallel to the resistor 18, and a voltage corresponding to a change in the resistance value of the resistor 27 is applied to the operational amplifier 23 via the switch 12.
is supplied to the non-inverting input terminal (+) of The output of the operational amplifier 23 is connected to the differential amplifier 7 via a resistor 28, and also connected to a switch 29 ₁ and a variable resistor 3.
0 ₁ and 31 ₁ to the inverting input terminal (-). This series circuit consisting of switch 29 ₁ , variable resistor 30 ₁ and resistor 31 _{1 includes switch 29 1 , variable resistor 30 1} and resistor 31 1 .
9 ₂ , a series circuit consisting of a variable resistor 30 ₂ and a resistor 31 ₂ , a series circuit consisting of a switch 29 ₃ , a variable resistor 30 ₃ and a resistor 31 ₃ , a series circuit consisting of a switch 29 ₄ , a variable resistor 30 ₄ and a resistor 31 ₄ . connected in parallel. Further, the inverting input terminal (-) of the operational amplifier 23 is grounded via a resistor 32. Further, the emitter and collector of a PNP transistor 33 are connected between the differential amplifier 7 side of the resistor 28 and the ground, and the base of this transistor 33 is connected to a resistor connected in series between the power supply terminal 36 and the ground. It is connected to the connection point between 34 and 35.

In the above configuration, the operational amplifier 20 is for setting the automatic exposure voltage, and the light receiving current generated in the photodiode 21 connected between its non-inverting input terminal (+) and inverting input terminal (-) The semi-fixed resistor 25 selected by the switch 24 from
A voltage obtained by subtracting the voltage drop caused by the resistor 26 and the resistor 26 is output. For example, in the case of a high-density document 16, the amount of light received by the photodiode 21 is small, so the light-receiving current is also small, and the output voltage of the operational amplifier 20 becomes slightly larger, increasing the exposure voltage. As a result, the copy density becomes slightly lighter and a proper copy can be obtained. On the other hand, in the case of a document 16 with a low density, the situation is completely opposite to that described above, and the exposure voltage decreases, the copy density increases, and a proper copy can be obtained. Further, in the manual exposure voltage setting circuit 11, the DC voltage applied to the DC power supply terminal 36 is controlled by the resistors 37, 17,
18, 19 and variable resistor 27, the resistance-divided value is output. The outputs of the automatic exposure voltage control circuit 10 and the manual exposure voltage control circuit 11 are selected by the semiconductor switch 12 and amplified by the general setting circuit 8, and this voltage becomes the reference voltage.

By the way, the variable resistors 30 ₁ to 30 ₄ are used to compensate for variations between individual machines (for example, variations in the sensitivity of photosensitive drums, variations in the optical system, etc.) and differences in the optical system for each copying magnification. The resistors 25 ₁ to 25 ₄ are used to correct variations in the photodiode 21 and differences in the optical system for each copying magnification.

However, in the above-mentioned apparatus, as the number of variable magnification functions increases, the number of volumes corresponding to the number increases, and the adjustment becomes very complicated. Moreover, when changing the magnification in multiple steps in small steps such as 1% steps, the volume would increase innumerably, making it impossible to achieve this.

By the way, in an optical system in which the magnification m is changed by changing only the object-image distance and the lens-image distance with the same lens, if the voltage applied to the exposure lamp is constant, the image forming surface, that is, the drum surface It is generally known that the illuminance ratio of is inversely proportional to (1+m) ² . Further, the exposure amount on the drum surface is obtained by multiplying the illuminance by the image width and dividing by the circumferential speed of the drum. Here, in an electronic copying machine in which the peripheral speed of the drum is constant and the image width is constant, the amount of exposure on the drum surface is proportional to the illuminance. However, as the reduction ratio increases, the image width is no longer constant, so the relationship between the voltage that should be applied to the exposure lamp and the copying magnification in order to obtain a constant image density for a certain original density is as shown in Figure 2b, for example. become. As you can see, this characteristic can be approximated by a nearly straight line, but it tends to saturate at higher reduction ratios, so if you draw the closest straight line, you can use the most frequently used 1x copy setting. My body feels tight. Furthermore, if the optimum exposure is obtained at the same magnification, the exposure will be greatly distorted at other copying magnifications.

[Purpose of the invention]

This invention was made in view of the above circumstances,
The purpose of this is to be able to change the magnification in multiple steps, such as in 1% increments, and to obtain the optimum exposure amount at the most frequently used magnification, and also when using other magnifications when enlarging or reducing. Another object of the present invention is to provide an exposure control device that can obtain a substantially optimal exposure amount.

[Summary of the invention]

This invention relates to an exposure control device for controlling the exposure amount of an exposure lamp, which is used for image exposure using an exposure lamp, and enlargement or reduction corresponding to fine multi-step magnification in 1% increments. Changes in magnification during enlargement so that the voltage applied to the exposure lamp at a specific magnification and the voltage applied to the exposure lamp at the same magnification lie on the first straight line and the first extended line obtained by connecting the voltage applied to the exposure lamp at a specific magnification. On the other hand, a second straight line and a second line are obtained by linearly changing the voltage applied to the exposure lamp and connecting the voltage applied to the exposure lamp at a specific magnification during reduction and the voltage applied to the exposure lamp at the same magnification. 2, the voltage applied to the exposure lamp is changed linearly with respect to the change in magnification during reduction.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 3 corresponds to the automatic exposure control circuit 10 in FIG. 1. In FIG. 3, reference numeral 47 denotes an automatic exposure reference voltage generator, which generates a reference voltage _v1 , and is composed of, for example, a differential amplifier. Reference numeral 48 denotes a photoelectric converter, such as a photodiode, which receives reflected light from the original, and is configured to allow a light receiving current ip to flow therethrough. 49 is an arithmetic circuit, which is connected to the photodiode 48 from the reference voltage _v1.
Three types of values proportional to the light receiving current ip, that is, values corresponding to equal magnification (v ₂ ), enlargement (v ₃ ), and reduction (v ₄ ), are determined, and are expressed, for example, as follows.

v ₂ = v ₁ − ipR ₁ v ₃ = v ₁ − ipR ₂ v ₄ = v ₁ − ipR ₃ However, R ₁ , R ₂ , and R ₃ are variables, and R ₂ < R ₁ <
The relationship is R ₃ . This is because it has been confirmed that the larger the copying magnification is, the larger the light receiving current ip of the photodiode 48 is.

50 is a semiconductor switch (for example, TC 4053BP manufactured by Tokyo Shibaura Electric Co., Ltd.), which is switched by a signal specified by an operation panel (not shown) supplied from the CPU 15 during enlargement or reduction. 51 is a digital attenuator, which receives an output signal for equal magnification supplied from the arithmetic circuit 49 via a buffer 53, an output signal for enlargement supplied via the semiconductor switch 50 and the buffer 53, and an output signal for reduction. and a 6-bit code signal (BD) according to the copy magnification supplied from the CPU 15.
It outputs a signal (v ₆ ) according to the following, for example:

When enlarging: v ₆ = v ₁ − ip {R ₁ − (R ₁ − R ₂ ) (BD/
2 ⁿ )} When reducing: v ₆ = v ₁ − ip {R ₁ + (R ₃ − R ₁ ) (BD/
2 ⁿ )} (BD is an integer from 0 to (2 ⁿ -1)) The digital attenuator 51 is composed of an n-bit (6-bit) ladder resistance type, as shown in FIG. 4, for example. semiconductor switch 5
4 ₁ - 54 ₆ , resistors 55 ₁ - 55 ₇ and resistors 56 ₁ -
56 ₅ . The semiconductor switches 54 ₁ to 54 ₆ are, for example, TC 4053BP manufactured by Tokyo Shibaura Electric Co., Ltd., and each of them is constituted by two changeover switches, one of which is always on and the other is always off. These switch select bit data (decimal number) according to the copy magnification supplied from the CPU 15.
It is now possible to switch with BD. Above resistance 55 _{1
.about.55.sub.7} and the resistance values of the resistors _56.sub.1 to _56.sub.5 have a relationship of, for example, 2:1 (2R:R).

52 is an arithmetic circuit which performs arithmetic operations on the output signal (v ₆ ) from the digital attenuator 51 and the reference voltage (v ₁ ) and outputs a signal (v ₇ ). revealed.

When enlarged: v ₇ = v ₁ − ip {R ₁ − (R ₁ − R ₂ ) (BD/
2 ⁿ )・A When reduced by ₁ : v ₇ = v ₁ − ip {R ₁ + (R ₃ − R ₁ ) (BD/
2 ⁿ )・A ₁ Therefore, if the coefficient A ₁ is fixed or has no final stage (corresponding to A ₁ = 1), and at the same magnification (BD = 0),
Adjust R ₁ , and at a certain magnification of magnification, adjust R ₂ ,
At a specific magnification of reduction, adjust R ₃ or fix R ₁ , adjust the coefficient A ₁ at the same magnification (BD = 0), and adjust the resistance value R ₂ at a specific magnification. ,
By adjusting _R3 at a specific reduction magnification,
Control in fine multi-step magnification changes, such as in 1% increments, becomes possible.

Therefore, when R ₁ is fixed and the coefficient A ₁ ≧1, the configuration is as shown in FIG. 5. In this case, the arithmetic circuit 49 includes, for example, a differential amplifier 69 that outputs a signal corresponding to the light-receiving current of the photodiode 48, resistors 63 and 64, and a variable resistor 65.
66. Also, Batsuhua 5
3 is composed of operational amplifiers 71 and 72. Furthermore, the arithmetic circuit 52 is composed of an operational amplifier 73 that calculates the output voltage v ₆ from the digital attenuator 51 and the output voltage supplied from the automatic exposure reference voltage generation circuit 47 via the resistor 67. The output voltage of this operational amplifier 73 is supplied to its inverting input terminal via a variable resistor 68.

Note that in the above configuration, the resistors 63, 64, 6
The resistance values of variable resistors 65, 66, and 68 correspond to R1, R2, and R3, respectively, and the resistance values of variable resistors 65, 66, and 68 correspond to
Corresponds to VR1, VR2, VR3, variable resistor 65,
66 connection points and respective variable resistors 65, 66
The resistance values between the sliders correspond to VR1' and VR2'.

Therefore, the voltages v ₂ , v ₃ , v ₄ at each part are expressed by the following equations.

v ₂ = v ₁ − ip {R ₂ + (1 + R ₂ / R ₁ ) VR1} v ₃ = v ₁ − ip {R ₂ + (1 + R ₂ / R ₁ ) (VR1 − VR1')} v ₄ = v ₁ -ip {R ₂ + (1 + R ₂ /R ₁ ) (VR1 + VR2')} As a result, the voltage v ₂ is applied to the digital attenuator 5 via the buffer consisting of the operational amplifier 72.
1, the voltages v ₂ and v ₃ are selected by a switch 50 and are applied to a digital attenuator 5 through a buffer consisting of an operational amplifier 71.
1 signal input. The output of this digital attenuator 51 is amplified by an amount proportional to the light receiving current ip subtracted from the reference voltage v ₁ by an arithmetic circuit 52, and outputs a voltage v ₇ expressed by the following equation.

When expanding v ₇ = v ₁ − ip {R ₂ + (1 + R ₂ / R ₁ ) VR1 − (1 + R
₂ /R ₁ ) VR1′ (BD/2 ⁶ )} (1 + VR3 / R3) When reducing v ₇ = v ₁ −ip {R ₂ + (1 + R ₂ /R ₁ ) VR1 + (1 + R
₂ /R ₁ ) VR2' (BD/2 ⁶ )} (1 + VR3/R3) where BD is an integer from 0 to 2 ⁶ -1. Here, the resistance values R1, R2, R3, VR1, and VR2 are fixed quantities, and the resistance Since the values VR1', VR2', and VR3' are variable amounts, adjust the resistance value VR3 when the magnification is the same (BD = 0), adjust the resistance value VR1' when expanding, and adjust the resistance value VR2' when scaling down. By doing so, as shown in FIG. 6, the amount proportional to the light-receiving current ip subtracted from the reference voltage _v1 can be changed so as to be on a polygonal line with respect to the copying magnification.

Note that in the above example, the resistance value R ₁ is fixed and the coefficient
This was the case where A ₁ ≧1, but it is not limited to this and can be performed in the same way in other cases as well. For example, when the coefficient _A1 is "1", the automatic exposure control circuit 10 operates as shown in FIG.
9a, and the arithmetic circuit 52 has been deleted. When the coefficient A ₁ is fixed and smaller than 1, the automatic exposure control circuit 10 converts the reference voltage v ₁ into a resistor at the output terminal of the digital attenuator 51, as shown in FIG. 80. Further, when the coefficient _A1 is fixed and larger than "1", the automatic exposure control circuit 10 uses the arithmetic circuit 49a of FIG. 7, as shown in FIG. 9, and the arithmetic circuit 52 of FIG. 82 and an operational amplifier 83. Furthermore, the resistance value R ₁ is fixed and the coefficient A ₁ is "1".
If it is smaller, the automatic exposure control circuit 10
As shown in the figure, the arithmetic circuit 52a shown in FIG. 9 is replaced with an arithmetic circuit 52b consisting of a resistor 84 and a variable resistor 85. Further, when the resistance value R ₁ is fixed and the coefficient A ₁ is smaller than "1", the automatic exposure control circuit 10 connects the arithmetic circuit 52 of FIG. 5 from the resistor 84 and the variable resistor 85 as shown in FIG. The configuration has been changed to an arithmetic circuit 52b.

Also, as in the example above, the resistance value R ₁ is fixed,
When the coefficient A ₁ ≧1, the same operation can be performed even if the arithmetic circuit 49a is used as shown in FIG.

Note that in the above embodiment, the automatic exposure control circuit 10
Although the case has been described in which the implementation is performed using a general setting circuit, the implementation is not limited to this, and the implementation may be performed using a comprehensive setting circuit. In this case, the general setting circuit 12
It is configured as shown in the figure. i.e. 100
is an arithmetic circuit that amplifies or divides the voltage supplied from the automatic exposure voltage control circuit 10 or the manual exposure voltage setting circuit 11 via the switch 12 into three voltage outputs, that is, equal magnification (v ₁₀ ),
This is to find values corresponding to expansion (v ₁₁ ) and contraction (v ₁₂ ), and can be expressed, for example, as follows.

v ₁₀ = A ₂ v ₉ v ₁₁ = A ₃ v ₉ v ₁₂ = A ₄ v ₉ (Each coefficient has the relationship A ₃ > A ₂ > A ₄ ) However, voltage v ₉ is the output from switch 12 It is voltage. Reference numeral 101 denotes a semiconductor switch, which is switched by a signal specified by an operation panel (not shown) supplied from the CPU 15 during enlargement or reduction. 102 is a ladder resistance type digital attenuator, which outputs the same output voltage supplied from the arithmetic circuit 100 via the buffer 103, and the output voltage of the semiconductor switch 1.
01 and an output voltage for enlargement supplied via the buffer 103, an output voltage for reduction supplied through the buffer 103, and 6 according to the copy magnification supplied from the CPU 15.
It outputs an output voltage (v ₁₄ ) according to the bit code signal (BD), and is expressed, for example, as follows.

When enlarging: v ₁₄ = {A ₂ + (A ₃ − A ₂ ) (BD/2 ⁿ )}・v ₉ When reducing: v ₁₄ = {A ₂ − (A ₂ − A ₄ ) (BD/2 ⁿ ) }・v ₉ 104 is an arithmetic circuit that amplifies or divides the output voltage (v ₁₄ ) from the digital attenuator 102 and outputs an output voltage (v ₁₅ ),
For example, it is expressed as follows.

When enlarging: v ₁₅ = A ₅ · {A ₂ + (A ₃ − A ₂ ) (BD / 2 ⁿ )} · v
₉ When reduced: v ₁₅ = A ₅・{A ₂ − (A ₂ − A ₄ ) (BD/2 ⁿ )}・v
₉ Therefore, the coefficient A ₅ in the arithmetic circuit 104
is fixed or there is no arithmetic circuit 104 (coefficient
A ₅ = 1), by adjusting the coefficient A ₂ at the same magnification (BD = 0), by adjusting the coefficient A ₃ at the time of enlargement, and by adjusting the coefficient A ₄ at the time of reduction, as shown in Figure 5. It is now possible to control stepless magnification. Also, if the coefficient A ₂ is fixed, at the same magnification (BD
= 0), adjust _{the coefficient A 3 when} enlarging, and adjust the coefficient A ₄ when reducing.

Examples of the general setting circuit 12 are shown in FIGS. 14 to 25 depending on the conditions of each coefficient.

Further, in the above embodiment, the voltage selected depending on whether to enlarge or reduce is used as the signal input of the digital attenuator, but the invention is not limited to this. It may also be possible to switch between the two. Furthermore, digital attenuators are not limited to the ladder type;
It may also be constructed using a weighted resistance type or resistance division.

〔Effect of the invention〕

As detailed above, according to the present invention, it is possible to perform fine multi-step magnification changes such as in 1% increments, and to obtain the optimum exposure amount at the same magnification, which is the most frequently used magnification, and also when enlarging or reducing. It is possible to provide an exposure control device that can obtain a substantially optimal exposure amount even at other magnifications.

[Brief explanation of the drawing]

Figure 1 is a diagram schematically showing the overall configuration of an exposure control device, Figure 2a is an electric circuit diagram showing an example of the configuration of a conventional reference voltage generation circuit, and Figure 2b is a diagram showing the copying magnification and exposure lamp application. The diagrams showing the relationship with voltage, FIGS. 3 to 12, show an embodiment of the present invention.
Figure 3 is a block diagram schematically showing the configuration of the automatic exposure voltage control circuit, Figure 4 is an electric circuit diagram showing the configuration of the digital attenuator, and Figure 6 is proportional to the copying magnification and the light receiving current subtracted from the reference voltage. Figures 5 and 7 to 12 are electric circuit diagrams showing the configuration of the automatic exposure voltage control circuit in detail, and Figure 13 shows the overall settings in another embodiment. 14 to 25 are electrical circuit diagrams illustrating the configuration of FIG. 13 in detail. 3...Exposure lamp, 8...General setting circuit, 9...
... Limiter circuit, 10 ... Automatic exposure voltage control circuit, 11 ... Manual exposure voltage setting circuit, 12 ... Semiconductor switch, 13 ... Reference voltage generation circuit, 15
...CPU, 47...Automatic exposure reference voltage generator,
48...Photodiode, 49, 52...Arithmetic circuit, 50...Semiconductor switch, 51...Digital attenuator, 53...Buffer.

Claims (1)

[Scope of Claims] 1. A document that exposes an image by irradiating the document with an exposure lamp and guiding light from the document to an image carrier, and has a function of enlarging and reducing the exposed image on the document. In an exposure control device that controls the exposure amount of an exposure lamp used, a first straight line obtained by connecting a voltage applied to the exposure lamp at a specific magnification during enlargement and a voltage applied to the exposure lamp at the same magnification; The voltage applied to the exposure lamp is changed linearly with respect to the change in magnification during enlargement, so that the voltage applied to the exposure lamp at a specific magnification during reduction is on an extension line of The voltage applied to the exposure lamp was configured to vary linearly with respect to the change in magnification during reduction so that the voltage applied to the exposure lamp was on the second straight line and the second extended line obtained by connecting the voltage applied to the exposure lamp. An exposure control device characterized by: