JPH087489B2 - Copier with variable magnification function - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Field of Use> The present invention relates to a copying machine having a variable magnification function, and more specifically, it remains on the outer peripheral edge of a photoconductor during variable magnification copying, especially during reduction copying. The present invention relates to a copying machine having a variable power function, which is capable of effectively removing electric charges.

<Prior Art> Conventionally, in response to a demand for improved usability, a copying machine capable of performing variable magnification copying has been provided and widely spread.

In such a copying machine, an electrostatic latent image having a width wider than that of the original is formed on the photoconductor if enlargement copying is performed. Therefore, the electrostatic latent image is uniformly formed on the photoconductor by the charger. The electric charge does not remain as it is, and there is no inconvenience such as waste of toner and contamination of the inside of the copying machine main body due to excessive toner adhesion. On the other hand, if reduction copying is to be performed, an electrostatic latent image having a width narrower than that of the original is only formed on the photoconductor, and no reflected light is radiated to the peripheral portion of the photoconductor. Remains as it is, and excess toner adheres to the residual charge portion, resulting in waste of toner, contamination of the inside of the copying machine main body, and the like. Therefore, in order to eliminate such inconvenience,
By installing a plurality of blank lamps corresponding to each reduction ratio between the charging charger and the developing device and turning on only a predetermined blank lamp corresponding to the reduction ratio, an electrostatic latent image during reduction copying The extra charge does not remain outside.

<Problems to be Solved by the Invention> In the copying machine having the above configuration, a large number of blank lamps must be attached in correspondence with each set reduction ratio, and the configuration becomes complicated and There is an inconvenience that it is necessary to increase the mounting accuracy and the manufacturing is difficult.

In particular, recently, a large number of copiers having a so-called zoom function have been provided in which a fine scaling factor can be selected. For such a copier, a blank lamp corresponding to each scaling factor is provided. Is extremely difficult to form, and a considerably small light-emitting body itself must be used, which is expensive as a whole.

<Objects of the Invention> The present invention has been made in view of the above problems, and provides a copying machine having a variable magnification function, which can simplify the structure of the blank lamp and does not need to increase the mounting accuracy. Is intended.

<Means for Solving the Problems> To achieve the above object, the copying machine of the present invention is
A white reflecting portion having a width wider than that of the maximum size original that can be copied is formed, and a blank lamp for eliminating charges in the peripheral portion of the photoconductor is provided, and the width W of the white reflecting portion is L × ( M _X / M _MIN ) ^{1 / n} ＞ W ≧ L × (M _X / M
_MIN ) ^{1 / (n + 1)} and the interval Si between the partition walls of the blank lamp is W ^{n + 1-i} × Z _MIN / L
^{n + 1-i} ≧ Si ≧ L ⁱ × Z _MAX / W ⁱ is set (where L is the maximum original document width that can be copied, and M _X is the maximum original image on the photoconductor). The scaling factor that can be printed in the forming area Z _MAX , M _MIN is the minimum scaling factor, Z _MIN is the minimum image forming region of the photoconductor when a document of the maximum width is printed with the minimum scaling factor, and n is (I is a natural number of n or less).

<Function> As a result of earnest studies by the present inventor, by forming the white reflecting portion wider than the original of the maximum size, the excess light on the photoconductor is lost by the reflected light from the peripheral portion of the white reflecting portion. I found that it can be done. Then, based on this knowledge, by appropriately setting the width of the white reflecting portion, no blank lamp is required for a reduction ratio in a considerable range, and even for reduction ratios below the reduction ratio. ,
It has been found that only a limited number of blank lamps can dissipate the excess charge on the photoreceptor.

The present invention has been made on the basis of the above findings, and by adopting the above configuration, the maximum original document width L can be formed on the photoconductor at a magnification slightly smaller than the magnification at which the maximum image forming area Z _MAX can be imaged. When forming an electrostatic latent image, it is possible to eliminate all unnecessary charges outside the electrostatic latent image by the reflected light from the white reflection portion, and the electrostatic latent image is reflected by the reflected light from the white reflection portion. When an electrostatic latent image is formed on the photoconductor with a scaling factor that does not allow unwanted external charges to be erased over the entire area, erase the charges in the range that cannot be eliminated by a blank lamp. It is possible to eliminate all the unnecessary charges of.

Then, the blank lamp is controlled in the number of sections to be lit in accordance with the scaling ratio, that is, in correspondence with the width of the range in which the electric charge can be lost by the reflected light from the white reflecting portion, and corresponds to the document. It is possible to eliminate the electric charges in unnecessary portions without adversely affecting the electrostatic latent image.

<Examples> Hereinafter, detailed description will be given with reference to the accompanying drawings illustrating examples.

FIG. 3 shows a copying machine in which the optical system moves.
FIG. 3 is a schematic view of a main part, which clearly shows an internal mechanism of a photoconductor drum as a photoconductor.

Reference numeral (1) is an original placing table located on the upper surface of the copying machine main body (11), and at a predetermined position below the original placing table, a light source (21), reflecting mirrors (22) (23) (24), a lens (25), and Reflector (2
The optical system (2) composed of 6) is provided, and the light source (21) and the reflecting mirrors (22), (23) and (24) are moved in the direction of arrow A to sequentially scan and expose the original (D). be able to. Then, the light source (21) and the flat reflecting mirror (22).
Move in unison with each other, and the plane reflecting mirrors (23, 24) also move in unison, so that the moving speed of the former is twice that of the latter. Then, below the optical system (2), the photosensitive drum (31) that rotates in the direction of arrow B for each copying operation, the charger (33), the blank lamp (38), the developing device (34), It has a copy processing section (3) composed of a transfer charger (35), a separation charger (36), and a cleaner (37), and is uniformly charged by a charging charger (33) so that the photosensitive drum (31) An electrostatic latent image is formed by irradiating the surface with light reflected from the document (D), and the electrostatic latent image is visualized as a toner image by the developing device (34), and the toner image is formed by the transfer charger (35). Can be transferred onto a copy paper (P). The copy paper feeding unit (4) includes a paper feed roller (41), a paper feed path (42), a registration roller (43), a conveyor belt (44), and a fixing device (4).
5) and a discharge roller (46). By driving the paper feeding roller (41), the paper feeding cassette (1
The copy paper (P) is fed one by one from 2), and the copy paper (P) is conveyed by the registration roller (43) in synchronization with the photoconductor drum (31), and the copy paper (P) after the toner image transfer is performed. ),
The transfer belt (44) conveys the toner image to the fixing device (45) to fix the toner image, and the discharge roller (46) discharges the copy paper (P) onto the tray (13). Reference numeral (10) is a document retainer mounted so as to cover the upper surface of the document placing table (1) so as to be vertically rotatable by a hinge mechanism or the like (not shown).

Figure 2 shows the photoconductor drum (31) and blank lamp (38).
FIG. 3 is a diagram showing the relationship between the light emitting body (38b) made up of LEDs and the like in the area surrounded by the partition wall (38a), and the light from the light emitting body (38b) is transferred to the photosensitive drum (3).
The surface of 1) can be irradiated. The partition wall (38a) regulates the irradiation range of the light emitter (38b). It is preferable to attach the partition wall (38a) also to the outermost side because it is possible to prevent the reflected light from other portions from irradiating the surface of the photoconductor drum (31), but it is not always necessary to attach it. Absent. Further, a blank lamp (not shown) is also attached to a portion corresponding to the central portion of the photoconductor drum (31), and unnecessary charges before and after the electrostatic latent image can be erased.

Then, as shown in FIG. 1, the document placing table (1) and the document retainer (10) are formed wider than the maximum size document (for example, A4 size) by a predetermined width 2W1.

FIG. 1A is a diagram illustrating a state in which an electrostatic latent image is formed, and shows a state in which only two compartments for accommodating a blank lamp are used (corresponding to FIG. 2A).

In the figure, the reflected light from the document (D) on the document table (1) is applied to the photosensitive drum (31), and
Light reflected from the peripheral edge of the document retainer (10), which serves as a white reflector, is also applied to the photosensitive drum (31). Then, the blank lamp (3
8) is attached and the blank lamp (38) is turned on so that the electric charge in the peripheral portion of the photosensitive drum (31) can be eliminated.

More specifically, in the figure, W is the width of the white reflecting portion, L is the maximum width of the copyable original, Z _MAX is the maximum image forming area of the photosensitive drum (31), and M _MIN is Z _MIN is the minimum scaling ratio, Z _MIN is the minimum image forming area when a document with the maximum width is printed on the photoconductor drum (31) with the minimum scaling ratio M _MIN , and M _X is the maximum image formation for the document with the maximum width. A magnification ratio that can be imprinted on the area Z _MAX , S is the interval between the partition walls of the pair of blank lamps (38), and M _X1 is the maximum width of the original document that is imprinted on the area corresponding to the interval S. It is a variable magnification that can be included.

Of the above values, L, Z _MAX , M _X , and M _MIN are values that have already been determined at the time of designing the copying machine, and are based on these values in order to eliminate unnecessary charges. Therefore, it is necessary to calculate the values of W and S.

First, as shown in FIG. 1 AI, by establishing a relationship of W × M _MIN = L × M _X1 = S W × M _X1 = L × M _X = Z _MAX among the above values, M _{When the} magnification is larger than _X1, only the reflected light from the white reflecting portion is used. When the magnification is smaller than M _X1 , the reflected light from the white reflecting portion and the light from the blank lamp (38) cause electrostatic discharge. It is possible to eliminate unnecessary charges outside the portion of the latent image corresponding to the original.

Since M _X1 = L × M _X / W and W = L × M _X1 / M _MIN are obtained from the above two formulas, M _X1 = (M _X × M _MIN ) ^{While 1/2} is obtained, W = L (M _X / M _MIN ) ^1/2 is obtained. When M _X1 takes the above value, the electrostatic latent image of the document having the maximum document width L is formed in the area corresponding to the interval S between the partition walls of the blank lamp (38). As can be understood from FIG. 1A, the electrostatic latent image of the document having the maximum document width L is formed in a region wider than the interval S if the magnification is larger than the value of M _X1. If the scaling factor is smaller than the value of M _X1 , the area is formed with a width narrower than the interval S. That is, the above M _X1
The value of is a scaling factor that satisfies the condition that unnecessary charges can be removed only by the reflected light from the white reflector without making the blank lamp (38) emit light when obtaining a copy of the document with the maximum width. Is the minimum value of. Therefore, the scaling factor M _X1 that can remove unnecessary charges without using a blank lamp can take the following allowable range values.

M _X > M _X1 ≧ (M _X × M _MIN ) ^1/2 On the other hand, when the width W of the white reflection portion takes the above value, the minimum magnification ratio M _X1 from the white reflection portion satisfying the above condition is satisfied. Light can be guided to the maximum image forming area Z _MAX without excess or deficiency. When the width W is smaller than the above value, when the magnification ratio is M _X1 , it becomes impossible to remove unnecessary charges on the edge portion of the photoconductor drum 31 by the reflected light from the white reflecting portion. That is, the above-mentioned value of W is the minimum value for removing the unnecessary charges only by the reflected light from the white reflecting portion. Width W is
Obviously, a value larger than the minimum value can be taken, but when using the blank lamp (38), Z _MAS -S> 0 can be considered as one of the conditions.

From FIG. 1A, Z _MAX = L × M _X and S = W × M
_{Since MIN} , L · M _X −W · M _MIN > 0 ∴ L (M _X / M _MIN )> W. That is, the width W can take a value within the following allowable range.

The value of S when L (M _X / M _MIN )> W ≧ L (M _X / M _MIN ) ^1/2 W has the minimum value is as follows.

S = W · M _MIN = L (M _X × M _MIN ) ^1/2 Then, based on the above-mentioned allowable range, the interval S also has an allowable range (S11 ≧ S1 ≧ S12).

That is, as shown in FIG. 1AII, if the minimum value of W is W _MIN and the actual value of W is W _MIN + d, then S11 is S11 = (W _MIN + d) M _MIN = (W _MIN + D) × Z _MIN / L, and S12 is S12 = M _X ′ × L = {Z _MAX / (W _MIN + d)} × L (where M _X ′ is W _MIN + d projected on the maximum image forming area) Therefore, the allowable range of the interval S is (W _MIN + d) Z _MIN / L ≧ S ≧ {Z _MAX / (W _MIN + d)}
L, that is, W × Z _MIN / L ≧ S ≧ (Z _MAX / W) L.

As is clear from the above description, for the width W of the white reflecting portion, a value within the above-mentioned allowable range is selected, and the spacing S between the partition walls (38a) of the pair of blank lamps (38) is also: By selecting a value within the above-mentioned allowable range, it is possible to eliminate the electric charge of the unnecessary portion based on the reflected light from the white reflecting portion and the light from the blank lamp (38). That is, since the space S may be selected within the above-mentioned allowable range based on the width W, the mounting accuracy of the partition wall (38a) does not have to be improved so much and is actually used in this state. It is possible to surely completely eliminate the electric charge in the unnecessary portion without being affected by the size of the original document and the scaling ratio, and it is possible to improve the obtained image quality.

FIG. 1B is a diagram for explaining a state in which an electrostatic latent image is formed, and shows a state in which only four compartments for accommodating a blank lamp are used (corresponding to FIG. 2B).

Also in this case, the allowable range of the width W of the white reflecting portion, the distance between the outermost blank lamps (the distance between the inner partition walls), and the most It is possible to obtain the allowable range of the interval between the blank lamps located inward (the interval between the inner partition walls).

In the above case, as shown in FIG. 1B, W × M _MIN = L × M _X2 = S2 W × M _X2 = L × M _X1 = S1 W × M _X1 = L × M _X = Z _MAX By providing a relationship, when the magnification is larger than M _X1 , only the reflected light from the white reflecting portion is used, and when the magnification is smaller than M _X1 and larger than M _X2 , the reflected light from the white reflecting portion is provided. , And the light from the outer blank lamp (38), and the light reflected from the white reflector in the case of a magnification smaller than M _X2 , and the light from all the blank lamps (38). It is possible to eliminate unnecessary charges outside the image.

Then, from the above three equations, M _X1 = L × M _X / W W = L × M _X1 / M _X2 M _X2 = W × M _MIN / L is obtained. Then, W = L (M _X1 / M _MIN ) ^1/2 is obtained from the latter two formulas, and by substituting into the previous formula, M _X1 = (M _X ² × M _MIN ) ^1/3 is obtained. .

Next, from the above formulas W × M _X2 = L × M _X1 and M _X1 = L × M _X / W, the relation of W = L (M _X / M _X2 ) ^1/2 can be obtained. And based on the above formula M _X2 = W × M _MIN / L, M _X2 = (M _X × M
_MIN ² ) ^1/3 is obtained.

Therefore, based on the above M _X1 and M _X2 , W = L
(M _X / M _MIN ) ^1/3 can be obtained.

It is understood from the same consideration as in the case of FIG. 1A that these values are respective minimum values, and for M _X1 , (M _X × M _MIN ) ^1/2 > M _X1 ≧ (M _X ² x M _MIN ) ^1/3 ,
For M _X2 , (M _X ² × M _MIN ) ^1/3 > M _X2 ≧ (M _X ×
For M _MIN ² ) ^1/3 and W, L (M _X / M _MIN ) ^1/2 > W ≧
The allowable range is L (M _X / M _MIN ) ^1/3 . This is because when the upper limit is exceeded, unnecessary charges outside the electrostatic latent image can be eliminated without providing a pair of inner blank lamps (38).

When the scaling factors M _X1 and M _X2 take their respective minimum values
The values of S1 and S2 are as follows.

S1 = L × M _X1 = L (M _X ² × M _MIN ) ^1/3 S2 = L × M _X2 = L (M _X × M _MIN ² ) ^1/3 Then, based on the above allowable range, the above interval There is an allowable range for S1 and S2 (S11 ≧ S1 ≧ S12, S21 ≧ S2 ≧ S2
2) It will be.

That is, as shown in FIG. 1BII, if the minimum value of W is W _MIN and the actual value of W is W _MIN + d, then S21 is S21 = (W _MIN + d) M _MIN = (W _MIN + D) × Z _MIN / L, and S11 is S11 = S21 × (W _MIN + d) / L = (W _MIN + d) ² × Z _MIN / L
² , S12 is S12 = {Z _MAX / (W _MIN + d)} × L, and S22 is S22 = S12 × L / (W _MIN + d) = {Z _MAX / (W _MIN +
Since d) ² } × L ² , the allowable range of the intervals S1 and S2 is (W _MIN + d) ² Z _MIN / L ² ≧ S1 ≧ {Z _MAX / (W _MIN +
d)} L, (W _MIN + d) × Z _MIN / L ≧ S2 ≧ {Z _MAX /
(W _MIN + d) ² } × L ² That is, W ² × Z _MIN / L ² ≧ S 1 ≧ (Z _MAX / W) × L, W × Z
_MIN / L ≧ S2 ≧ (Z _MAX / W ² ) × L ² .

As is clear from the above description, for the width W of the white reflecting portion, a value within the above-mentioned allowable range is selected, and the intervals S1 and S2 between the partition walls (38a) of the two pairs of blank lamps (38) are selected. Also, by selecting a value within the above allowable range,
Light reflected from white reflector and blank lamp (38)
It is possible to eliminate the electric charge of the unnecessary portion on the basis of the light from the. That is, the space S may be selected within the above-mentioned allowable range based on the width W, and therefore the mounting accuracy of the partition wall (38a) does not have to be improved so much.
It is possible to surely completely eliminate the electric charge in the unnecessary portion without being affected by the size of the original used and the scaling ratio, and it is possible to improve the obtained image quality.

FIG. 1C is a diagram for explaining a state in which an electrostatic latent image is formed, and shows a state in which only six compartments containing a blank lamp are used (corresponding to FIG. 2C).

Also in this case, the allowable range of the width W of the white reflecting portion and the distance between the blank lamps located at the outermost sides (the distance between the inner partition walls) are substantially the same as in the case of FIGS. 1A and 1B above. It is possible to obtain the permissible range of the space between the innermost blank lamps (the space between the inner partition walls) and the space between the blank lamps located in the middle (the space between the inner partition walls).

In the above case, as shown in FIG. 1 CI, W × M _MIN = L × M _X3 = S3 W × M _X3 = L × M _X2 = S2 W × M _X2 = L × M _X1 = S1 W × by having a relationship _{M X1 = L × M X =} Z MAX, only by reflected light from the white reflective portion in the case of M _X1 greater magnification, less than M _X1, and M _X2 greater magnification In the case of, the reflected light from the white reflector and the outermost blank lamp (3
8) and also smaller than M _X2 and M _X3
In the case of a larger magnification, the reflected light from the white reflector,
And by the light from the blank lamps (38) other than the innermost one, and by the light reflected from the white reflecting part and the light from all the blank lamps (38) in the case of a scaling factor smaller than M _X3. It is possible to eliminate unnecessary charges outside the latent image.

Then, from the above four equations, M _X3 = W × M _MIN / L M _X2 = W ² × M _MIN / L ² M _X1 = W ³ × M _MIN / L ³ W ⁴ = L ⁴ × M _X / M _MIN Is obtained.

Therefore, from the above formula, W = L (M _X / M _MIN ) ^1/4 is obtained, and by sequentially substituting it into the previous formula, M _X1 = (M _X ³ × M _MIN ) ^1/4 M _X2 = ( M _X ² × M _MIN ² ) ^1/4 M _X3 = (M _X × M _MIN ³ ) ^1/4 is obtained.

It is understood that these values are the respective minimum values from the same consideration as in the case of FIG. 1A, and for W,
The allowable range is L (M _X / M _MIN ) ^1/3 > W ≧ L (M _X / M _MIN ) ^1/4 . This is because if the upper limit value is exceeded, unnecessary charges outside the electrostatic latent image can be eliminated without providing the innermost pair of blank lamps (38).

The values of S1, S2 and S3 when the scaling factors M _X1 , M _X2 and M _X3 take the minimum values are as follows.

S1 = L × M _X1 = L (M _X ³ × M _MIN ) ^1/4 S2 = L × M _X2 = L (M _X ² × M _MIN ² ) ^1/4 S3 = L × M _X3 = L (M _X × M _MIN ³ ) ^1/4 And, based on the above allowable range, the above intervals S1, S2, S3
Also has an allowable range (S11 ≧ S1 ≧ S12, S21 ≧ S2 ≧
S22, S31 ≧ S3 ≧ S32).

That is, as shown in FIG. 1CII, if the minimum value of W is W _MIN and the actual value of W is W _MIN + d, then S31 is S31 = (W _MIN + d) M _MIN = (W _MIN + D) × Z _MIN / L, and the above S21 is S21 = S31 × (W _MIN + d) / L = (W _MIN + d) ² × Z _MIN / L
² , and the above S11 is S11 = S21 × (W _MIN + d) / L = (W _MIN + d) ³ × Z _MIN / L
³ , the above S12 becomes S12 = M _X × L = {W _MAX / (W _MIN + d)} × L,
The above S22 is S22 = S12 × L / (W _MIN + d) = {Z _MAX / (W _MIN +
d) ² } × L ² , and the above S32 is S32 = S22 × L / (W _MIN + d) = {Z _MAX / (W _MIN +
Since d) ³ } × L ³ , the allowable range of the intervals S1, S2, S3 is (W _MIN + d) ³ Z _MIN / L ³ ≧ S1 ≧ {Z _MAX / (W _MIN +
d)} L, (W _MIN + d) ² × Z _MIN / L ² ≧ S 2 ≧ {Z _MAX / (W _MIN +
d) ² } × L ² (W _MIN + d) × Z _MIN / L ≧ S3 ≧ {Z _MAX / (W _MIN + d)
³ } × L ³ That is, W ³ × Z _MIN / L ³ ≧ S 1 ≧ (Z _MAX / W) × L, W ² × Z
_MIN / L ² ≧ S 2 ≧ (Z _MAX / W ² ) × L ² , W × Z _MIN / L ≧ S 3 ≧
(Z _MAX / W ³ ) × L ³ .

As is clear from the above description, for the width W of the white reflection portion, a value within the above-mentioned allowable range is selected, and the intervals S1, S2, between the partition walls (38a) of the three pairs of blank lamps (38) are selected. S3
Also, by selecting a value within the above-mentioned allowable range, it is possible to eliminate the electric charge of the unnecessary portion based on the reflected light from the white reflecting portion and the light from the blank lamp (38). That is, the space S may be selected within the above-mentioned allowable range based on the width W, so that the partition wall (38a)
It is not necessary to improve the mounting accuracy of the so much, and in this state, it is possible to completely eliminate the electric charge of the unnecessary portion without being influenced by the size of the original document actually used and the scaling ratio. The image quality of the image can be improved.

In the above description, only the case where six blank lamp compartments are used has been described, but the present invention can be easily applied to the case where eight or more blank lamp compartments are used. When 2n (where n is a natural number) compartments are used, the width W of the white reflective portion is L (M _X / M _MIN ) ^{1 / n} > W ≧ L (M _X / M _MIN ) ^{1 / ( n + 1)} , and the interval Si between the partition walls of each pair of blank lamps (where i is a natural number less than or equal to n) is W ^{n + 1-i.}
× ZMIN / L ^{n + 1-i} ≧ Si ≧ L ⁱ × Z _MAX / W ⁱ can be selected so that the size of the original document and the scaling factor are not affected In addition, the electric charge of the unnecessary portion can be completely eliminated, and the obtained image quality can be improved.

<Effect of the Invention> As described above, according to the present invention, the white reflective portion larger than the original of the maximum size that can be copied is formed to eliminate the electric charge on the surface of the photoconductor in the predetermined range corresponding to the variable magnification of copying. Therefore, it is possible to surely eliminate the electric charge of the unnecessary portion without setting the range where the electric charge is erased by the blank lamp very strictly. Therefore, it is not necessary to raise the accuracy of mounting the blank lamp too much. It has a unique effect that can be simplified.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a state in which an electrostatic latent image is formed, FIG. 2 is a diagram showing a relationship between a photosensitive drum and a blank lamp, and FIG. 3 is a schematic diagram illustrating an internal mechanism of a copying machine. (1) …… Original platen, (10) …… Document holder, (31)…
… Photosensitive drum as photoconductor, (38) …… Blank lamp, (D) …… Original, (P) …… Copy paper

Claims (1)

[Claims] 1. An original document on a document table is exposed to form an electrostatic latent image on a photoconductor, the electrostatic latent image is visualized as a toner image, and then transferred onto a copy sheet to form an original document. In a copier designed to obtain a corresponding copy, a white reflection part wider than the maximum size original that can be copied is formed, and a blank lamp for eliminating charges at the peripheral part of the photoconductor is provided. And the width W of the white reflection part is L
× (M _X / M _MIN ) ^{1 / n} > W ≧ L × (M _X / M _MIN ) ^{1 / (n + 1)} and the interval Si between the partition walls of the blank lamp is W ^{n + 1-i} × Z _MIN / L ^{n + 1-i} ≧ Si ≧ L ⁱ × Z _MAX ^/ W ⁱ (where L is the maximum document width that can be copied and M _X is The maximum width of the original is the maximum image forming area Z of the photoconductor.
_The scaling factor that can be printed on _MAX , M _MIN is the minimum scaling factor, Z _MIN is the minimum image forming area of the photoconductor when a document of maximum width is printed with the minimum scaling factor, and n is the blank lamp. The number of sections, and i is a natural number less than or equal to n).