JPH06202021A - Laser printer device - Google Patents

Abstract

(57) [Summary] [Object] The present invention effectively obtains a high resolution in the sub-scanning direction in a laser printer device without changing the moving speed of the photoconductor. [Structure] A plurality of laser elements are used as a light source for forming one laser spot necessary for writing, and the peak position of the laser spot is shifted by combining the outputs of the plurality of laser elements to scan in the scanning direction on the photoconductor. By increasing the resolution in the sub-scanning direction that is orthogonal to the, it is possible to effectively obtain a high resolution in the sub-scanning direction without changing the moving speed of the photoconductor, and while forming an image. Moreover, the resolution can be changed, and thus an output image which is much smoother than the conventional one can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser printer device, and is particularly applicable to a device for obtaining a smooth output image with a laser beam.

[0002]

2. Description of the Related Art Conventionally, as a laser printer, a laser beam emitted from a laser light source is bent and shaken in a predetermined direction by a reflection mirror such as a galvanometer mirror or a polygon mirror, and is shaken on a photosensitive drum through a condenser lens such as an fθ lens. There is one that is configured to perform scanning and imaging in the cylindrical direction.

[0003]

By the way, as the resolution of such a laser printer, the resolution in the main scanning direction, that is, the lateral direction of the screen is not determined by a mechanical element because the movement of the laser beam is continuous. It is determined only by electrical factors.

In this case, the electrical element is the timing of writing, and if the spot D0 of the laser is sufficiently small as shown in FIG. 5, the more the time intervals T ₁ and T _{2 of} writing are, the more dots D0 are hit. Can be, Figure 5 (A)
The resolution of FIG. 5B is higher than that of FIG. If the writing interval T of the dot D0 is lengthened or shortened while writing an image, it is possible to continuously change the resolution.

Next, the resolution in the sub-scanning direction, that is, the vertical direction of the screen is determined by mechanical elements. That is, the resolution is determined by the distance the photosensitive drum rotates to write the next line after writing one line, that is, the feed pitch of the photosensitive drum.

Therefore, in order to change the resolution in the sub-scanning direction, as shown in FIG.
The feed pitches P ₁ to P _{2 in} FIG.
The resolution has been improved by changing to.

Actually, as shown in FIG. 7, the pitches P ₁ and P ₂ are in the middle of writing one screen (FIG. 7A).
However, this causes uneven rotation of the photosensitive drum, which causes uneven development, resulting in deterioration of image quality.

Assuming that development unevenness can be ignored, FIG.
(B) and 7 even constitute a mechanically to vary the pitch P _1, P ₂ as in writing (C), the pitch P ₁ of the previous line in the middle of one line,
The narrowing of P ₂ cannot be done because the photosensitive drum is reversed. Therefore, in the middle of one line, pitch P
Only change in the direction of widening ₁ and P ₂ can be given.

However, in order to increase the resolution in the sub-scanning direction by changing the rotation speed of the photosensitive drum in this way, in addition to the deterioration of the image quality due to the uneven development as described above, the printing speed is lowered, or the photosensitive drum The rotation control has a problem that the mechanical structure becomes complicated and the laser printer itself becomes large in size, which is still insufficient for practical use.

The present invention has been made in consideration of the above points, and an object thereof is to propose a laser printer device which can effectively obtain a high resolution in the sub-scanning direction without changing the moving speed of the photosensitive member. .

[0011]

In order to solve the above problems, according to the present invention, in a laser printer device 1 that scans a laser beam on a photosensitive member 11 to print predetermined information, a laser spot 1 required for writing. A plurality of laser elements are used as the light sources 4 forming the individual pieces, and the peak positions of the laser spots are shifted by combining the outputs of the plurality of laser elements to obtain a resolution in the sub-scanning direction orthogonal to the scanning direction on the photoconductor 11. I tried to raise it.

Further, according to the present invention, a laser printer which arranges a plurality of laser beams in a direction orthogonal to the scanning direction on the photoconductor and scans the plurality of laser beams on the photoconductor 11 to print predetermined information. In the apparatus 1, a plurality of laser elements are used as the light source 4 forming one laser spot required for writing, and the peak position of the laser spot is shifted by combining the outputs of the plurality of laser elements. The resolution is increased in the sub-scanning direction orthogonal to the scanning direction of.

[0013]

A plurality of laser elements are used as the light source 4 for forming one laser spot required for writing, and the peak position of the laser spot is shifted by combining the outputs of the plurality of laser elements. By increasing the resolution in the sub-scanning direction orthogonal to the scanning direction, the resolution in the sub-scanning direction can be effectively increased without changing the moving speed of the photoconductor 11, and an image is formed. The resolution can be changed even in the middle, and thus an output image much smoother than the conventional one can be obtained.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a laser printer according to the present invention as a whole, and a video controller 2 and a DC controller 3 are arranged between the apparatus and an external device, and the writing optical system 4 is controlled by the DC controller 3. The desired data can be printed.

The hexahedron which is emitted under the control of the DC controller 3 and emitted from the laser diode in the laser unit 5 passes through the collimator lens 6 and the cylindrical lens 7 and then rotates in accordance with the scanner motor 7. The spot is connected on the photosensitive drum 11 by the image forming lens 9 and the reflecting mirror 10 which are reflected by the mirror 8.

With the rotation of the hexahedral mirror 8, the position of the spot moves from the point A to the point B on the photosensitive drum 11, thereby drawing one scanning line. Here, rotate the photosensitive drum 11 in the direction of arrow a in the figure,
By drawing lines one by one, one image called an electrostatic latent image is formed on the photosensitive drum 11. This latent image is visualized by a developing device (not shown), further transferred to paper and fixed, and then output.

Here, in the case of this embodiment, a so-called multi-beam laser element in which laser elements are integrated on one chip is used as a laser unit to turn on a plurality of lasers at the same time and appropriately control the respective powers. By doing so, the peak of the combined output is shifted to an arbitrary position in the laser array.

That is, as shown in FIG.
When two lasers are arranged side by side, if only the laser A is turned on, the peak of the laser output is naturally right above the laser A as shown in FIG. 2 (A), and as shown in FIG. 2 (B). If only the laser B is turned on, the output peak is right above the laser B.

Therefore, if the lasers A and B are turned on at the same intensity at the same time, the peak of the laser output can be located at the center of the lasers A and B, as shown in FIG. Further, the peak of the laser output can be shifted to any position between the lasers A and B by changing the intensity ratio of the laser A and the laser B.

However, in this case, the arrangement interval must be sufficiently narrow with respect to the energy spread of each laser. This condition changes depending on the shape of the energy distribution of the laser. For example, when the laser energy is a Gaussian distribution, the relationship between the energy half-value width E ₅₀ and the laser interval P is
The following formula

[Equation 1] Need to be satisfied.

In practice, the laser printer 1 uses two beams, and the laser unit 4 uses a laser element with one chip and two beams. The laser array is arranged in the sub-scanning direction, that is, the vertical direction of the screen. Furthermore, this laser printer 1 has 2
It is configured to draw one line by combining the beams.

In this case, the output of each beam is usually set so that the peak of the combined beam is at the center of the two beams. The operation of the laser printer 1 is the same as that of general one except that the writing is performed by the synthetic beam. As a result, in this laser printer 1, the resolution in the sub-scanning direction can be changed by electrical control.

That is, as shown in FIG.
As shown in (A), writing is continued with the peak of the combined beam at the center position PC, but when it is desired to narrow the gap with the previous line, the intensity of the upper beam as shown in FIG. 3 (B). The intensity of the beam on the lower side is lowered and the intensity of the lower beam is shifted to shift the peak of the combined beam to the upper position PU, thereby obtaining the same effect as reducing the pitch in the sub-scanning direction.

On the contrary, when it is desired to widen the distance from the previous line, the intensity of the upper beam is decreased and the intensity of the lower beam is increased as shown in FIG. The effect is similar to that obtained by shifting to the lower position and increasing the pitch in the sub-scanning direction.

In this way, in the laser printer 1, since the pitch in the sub-scanning direction can be changed only by the electric control, it is possible to prevent the problem of uneven development such as in the case of mechanically changing the pitch. Furthermore, even during writing, you can change the pitch at any position. Thus, the output image can be made smoother.

For example, as shown in FIG. 4, in an output image of a normal printer, when an obliquely drawn line is enlarged,
As shown in FIG. 4 (A), jagged edges occur. In practice, this cannot be avoided with a normal laser printer, but when the pitch in the sub-scanning direction is electrically changed as in this embodiment, the end portion as shown in FIG. By changing the pitch of and hitting extra dots, a smoother output can be obtained as a whole.

According to the above construction, the laser unit 4 uses a laser device of one chip and two beams for emitting the laser beam in the sub-scanning direction, and one scanning line is drawn by combining two beams, and By changing the laser output of the beam arbitrarily, the peak position of the laser spot can be shifted in the sub-scanning direction, and the resolution in the sub-scanning direction can be increased. This makes it possible to simplify the rotation speed of the photosensitive drum. With this, it is possible to effectively obtain a high resolution in the sub-scanning direction, and it is possible to change the resolution even while an image is being formed, and thus it is possible to obtain an output image that is much smoother than in the past. The laser printer 4 can be realized.

In the above embodiment, a laser device with one chip and two beams was used as the laser unit.
Even with three or more beams, the same effect as that of the above-described embodiment can be realized. In this case, the more the number of beams is increased, the wider the variable range of shift can be made.

In the above embodiment, the present invention is applied to a laser printer which draws one scanning line at a time.
The present invention is not limited to this, and can be applied to a so-called multi-beam printer that draws a plurality of scanning lines at one time.

[0031]

As described above, according to the present invention, a plurality of laser elements are used as a light source for forming one laser spot required for writing, and the laser spots are combined by combining the outputs of the plurality of laser elements. Shift the peak position,
By increasing the resolution in the sub-scanning direction orthogonal to the scanning direction on the photoconductor, a high resolution in the sub-scanning direction can be effectively obtained without changing the moving speed of the photoconductor, and an image can be displayed. The resolution can be changed even during formation, and thus a laser printer device that obtains an output image that is much smoother than in the past can be realized.

[Brief description of drawings]

FIG. 1 is an optical system diagram showing an embodiment of a laser printer device according to the present invention.

FIG. 2 is a schematic diagram for explaining the principle of peak shift due to laser light combination.

FIG. 3 is a schematic diagram for explaining a peak shift by combining two beams.

FIG. 4 is a schematic diagram showing print output by the laser printer of FIG.

FIG. 5 is a schematic diagram for explaining a resolution in a main scanning direction.

FIG. 6 is a schematic diagram for explaining the resolution in the sub-scanning direction.

FIG. 7 is a schematic diagram showing a case where the feed pitch of the photosensitive drum is changed.

[Explanation of symbols]

1 ... Laser printer, 2 ... Video controller, 3
...... DC controller, 4 ... Laser unit, 5 ...
Collimator lens, 6 ... Cylindrical lens, 7 ...
... Skiyan motor, 8 ... hexahedral mirror, 9 ... imaging lens, 10 ... reflection mirror, 11 ... photosensitive drum.

Claims (2)

[Claims] 1. A laser printer apparatus for scanning a photosensitive member with laser light to print predetermined information, wherein a plurality of laser elements are used as a light source for forming one laser spot required for writing, and the plurality of laser elements are used. A laser printer apparatus characterized in that the peak position of the laser spot is shifted by combining the outputs of the elements to increase the resolution in the sub-scanning direction orthogonal to the scanning direction on the photoconductor. 2. A laser printer which prints predetermined information by arranging a plurality of laser beams in a direction orthogonal to a scanning direction on a photoconductor and scanning the plurality of laser beams on the photoconductor. A plurality of laser elements are used as a light source for forming one laser spot necessary for the laser spot, and the peak position of the laser spot is shifted by combining the outputs of the plurality of laser elements, so that the laser spot is orthogonal to the scanning direction on the photoconductor. A laser printer device characterized by increasing the resolution in the sub-scanning direction.