CN101963700B - Short light collecting distance two-piece type f theta lens of laser scanning device - Google Patents

Abstract

The invention relates to a short light collecting distance two-piece type f theta lens of a laser scanning device, which is used for a laser scanning device with a polygonal rotating mirror. In a main scanning direction of a scanning center shaft, a first lens has positive diopter, a second lens has negative diopter, wherein the first lens is provided with a first optical surface and a second optical surface, the second lens is provided with a third optical surface and a fourth optical surface; the concave surfaces of the first optical surface, the second optical surface and the third first optical surface are arranged on the side of the polygonal rotating mirror; and the fourth optical surface is provided with inflexion points, and the convex surface of the fourth optical surface is positioned on the side of the polygonal rotating mirror on the scanning center shaft. The short light collecting distance two-piece type f theta lens satisfies an optical condition that tan (beta) is not less than 0.4557 and is not more than 0.7265, wherein the beta is a maximum and effective window angle. By the arrangement of the first lens and the second lens of the short light collecting distance two-piece type f theta lens, the distance between the polygonal rotating mirror and an imaging surface can be effectively shortened in order to achieve the specific purpose of reducing the volume of the laser scanning device.

Description

The short condensation distance two-slice type f theta eyeglass of laser scanning device

Technical field

The present invention relates to a kind of short condensation distance two-slice type f theta eyeglass of laser scanning device; More particularly; Relate to a kind of be used to have polygonal rotating mirror laser scanning device (Laserscanning unit) of (polygon mirror), have short condensation distance to reduce the two-chip type f theta lens of laser scanning device volume.

Background technology

The used laser scanning device LSU (LaserScanning Unit) of laser beam printer LBP (Laser Beam Print) is to utilize the scanning motion (laser beam scanning) of a high speed rotating polygonal mirror (polygon mirror) to control laser beam, like U.S. Pat 7 at present; 079,171, US6,377; 293, US6; 295,116, or of Taiwan patent 198966.Its principle is summarized as follows: utilize semiconductor laser give off laser beam (laser beam); Earlier via a collimating mirror (collimator); Form parallel beam again via an aperture (aperture); And parallel beam is again through behind the cylindrical mirror (cylindrical lens), focuses on and forms a wire (line image), is projected on the high speed rotating polygonal mirror (polygon mirror) again; And evenly being provided with polygonal mirror (reflection mirror) on the polygonal rotating mirror continuously, it is positioned at or approaches on the focal position of above-mentioned wire imaging (line image).Projecting direction by polygonal rotating mirror control laser beam; When continuous plural catoptron during at high speed rotating; Can be projected to laser beam on the catoptron along the parallel direction of direction of scanning (X axle) with on same angular velocity (angular velocity) deflective reflector to the f θ linear sweep eyeglass; And f θ linear sweep eyeglass is arranged at the polygonal rotating mirror side, can be single-piece lens structure (single-element scanning lens) or is two formula lens structures.The function of this f θ linear sweep eyeglass is to make the laser beam of injecting the f Theta lens via the mirror reflects on the polygonal mirror can scanning ray be focused into a circle (or ellipse) luminous point and be incident upon a light receiving surface (photosensitive drums photoreceptor drum; Be imaging surface) on, and the requirement of reaching linear sweep (scanning linearity), use like U.S. Pat 4; 707; 085, US6,757,088 or Jap.P. JP2004-294713 etc.Yet traditional f θ linear sweep eyeglass still has following point:

During (1), owing to the polygonal rotating mirror reflection lasering beam; The scanning center's axle that is projected to the laser beam on the catoptron of each polygonal rotating mirror is not the central rotating shaft over against polygonal rotating mirror; So that when design f θ linear sweep eyeglass, need consider deviation (reflection deviation) problem that leaves of polygonal rotating mirror simultaneously.The optics correction method that uses sub scanning direction in the conventional art is with the method for the optics revisal of revising main scanning direction, like U.S. Pat 5,111, and 219, US5,136,418, the technology that disclosed such as Jap.P. JP2756125.But can suitably revise via the optics correction method of sub scanning direction for making, then need long focal length, and cause the problem that increases the laser scanning device overall volume from the axle deviation.

(2), be to make the diameter of the luminous point of scanning ray on photosensitive drums of f θ linear sweep eyeglass can meet the operating specification requirement; On conventional art, the normal eyeglass with long focal length that uses is so that image quality is preferable; Even use catoptron to extend into the distance of picture; Like U.S. Pat 2002/0063939 or use the three-member type eyeglass such as U.S. Pat 2002/0030158, US5,086,350 and Jap.P. JP63-172217.Or use the difficult diffraction eyeglass of making (diffraction lens), like U.S. Pat 2001/0009470, US5,838,480 etc.More or use two formula eyeglasses with point of inflexion (inflection point), like U.S. Pat 5,111,219, US7,057,781, US6,919,993 and use single-piece eyeglass such as Jap.P. JP04-50908 with point of inflexion.

(3), for being applicable to the use of miniprinter; And one of classic method that is adopted when dwindling the laser scanning device volume is for shortening the image-forming range on the photosensitive drums; Like U.S. Pat 7,130, in 096; Use restriction effective scanning distance (effective scanning range) and the method for image optics, to shorten the image-forming range on the photosensitive drums and to eliminate ghost phenomenon (ghost image) apart from (optical length) ratio.And for example U.S. Pat 6,324, in 015, use the distance (claim optically focused apart from) of restriction polygonal rotating mirror to photosensitive drums and the focal length ratio (d/f) of f Theta lens, shortening its distance, but are that 100mm is an example with the focal length, and optically focused is apart from being about 200mm.U.S. Pat 6; 933; The two-chip type f theta lens that is disclosed in 961; Adopt asymmetric (asymmetric optical surface) optical surface, make two f Theta lens optical axises on main scanning direction or sub scanning direction, produce off normal (axis deviate from main-scanning or sub-scanning) and can dwindle the optically focused distance.For satisfying the consumer to the compact demand of laser scanning device; For having short condensation distance (like laser printer with A4; And optically focused apart from need less than 150mm) and on main sweep and sub scanning direction; Can effectively revise optical distortion, improve quality of scanning and the short condensation distance two-slice type f theta eyeglass that improves resolution, real is user's active demand.

Summary of the invention

The object of the present invention is to provide a kind of short condensation distance two-slice type f theta eyeglass of laser scanning device; Be used to have the laser scanning device of polygonal rotating mirror; Two-chip type f theta lens is started at by polygonal rotating mirror in regular turn; Be provided with one first eyeglass and second eyeglass, wherein first eyeglass has first optical surface and second optical surface, and second eyeglass has the 3rd optical surface and the 4th optical surface.This short condensation distance two-slice type f theta eyeglass is characterised in that each optical surface of two-chip type f theta lens is aspheric surface at main scanning direction.Be positioned on the main scanning direction of scanning center's axle, first eyeglass is the meniscus eyeglass with positive diopter, and second eyeglass is for having negative dioptric eyeglass.The concave surface of first, second optical surface of first eyeglass and the 3rd optical surface of second eyeglass is towards the polygonal rotating mirror side.The 4th optical surface of second eyeglass has the point of inflexion and its convex surface towards the polygonal rotating mirror side; Mainly in order to the homogenising scanning ray on main scanning direction and sub scanning direction; Because of the shifted scanning central shaft causes formed imaging deviation on photosensitive drums; And can the scanning ray correction be concentrated on the object, and can the effect of the desired linear sweep of laser scanning device be reached in scanning ray correctly imaging on object that polygonal rotating mirror reflected.

Another object of the present invention is to provide a kind of short condensation distance two-slice type f theta eyeglass of laser scanning device, have short condensation distance, can reach volume that dwindles laser scanning device and purpose with good imaging effect.Because of satisfying the condition of 0.4557≤tan (β)≤0.7265; Wherein β is maximum valid window angle (maximum angle of effective window); Make polygonal rotating mirror laser light reflected Shu Jing short condensation distance two-slice type f theta eyeglass thus; Can make scanning ray under shorter focusing distance, still can meet the requirement that is incident upon luminous point on the object (spot) area, and reach the purpose that reduces the laser scanning device volume.

A purpose more of the present invention is to provide a kind of short condensation distance two-slice type f theta eyeglass of laser scanning device; The modifying factor that can distort scanning ray departs from scanning center's axle; And cause skew to increase at main scanning direction and sub scanning direction; Make the luminous point that images in photosensitive drums produce the problem of distortion, and make each imaging luminous point size be able to homogenising, improve the effect of separating picture element amount (resolution quality) and reach.

Therefore; The short condensation distance two-slice type f theta eyeglass of laser scanning device of the present invention is applicable to laser scanning apparatus, by the catoptron on the polygonal rotating mirror that is arranged in the laser scanning device; The laser beam reflection of light emitted is become scanning ray, on object, to form images.As far as laser printer; This object is generally photosensitive drums (drum); That is, the laser beam that luminous point to be formed images can go out by light emitted, form scanning ray via the scanning mirror of polygonal rotating mirror after; This scanning ray in addition behind angle correction and the position, can form luminous point (spot) via short condensation distance two-slice type f theta eyeglass of the present invention again on photosensitive drums.Owing to scribble photosensitizer on the photosensitive drums, be used to respond to carbon dust and make it be gathered in paper, thus, just can data be printed.

Description of drawings

Fig. 1 is the synoptic diagram of the optical path of two-chip type f theta lens of the present invention;

Fig. 2 is the synoptic diagram through the optical path of the scanning ray of first eyeglass and second eyeglass;

Fig. 3 is the part enlarged diagram of explanation the 4th optical surface point of inflexion;

Fig. 4 is the synoptic diagram of the spot areas of how much luminous points on the explanation photosensitive drums;

Fig. 5 is maximum valid window synoptic diagram;

Fig. 6 is the optical path figure of various embodiments of the present invention;

Fig. 7 is the big logotype of the luminous point of diverse location on object of first embodiment;

Fig. 8 is the luminous point distribution plan on the first embodiment photosensitive drums;

Fig. 9 is the big logotype of the luminous point of diverse location on object of second embodiment;

Figure 10 is the luminous point distribution plan on the second embodiment photosensitive drums;

Figure 11 is the big logotype of the luminous point of diverse location on object of the 3rd embodiment;

Figure 12 is the luminous point distribution plan on the 3rd embodiment photosensitive drums;

Figure 13 is the big logotype of the luminous point of diverse location on object of the 4th embodiment;

Figure 14 is the luminous point distribution plan on the 4th embodiment photosensitive drums;

Figure 15 is the big logotype of the luminous point of diverse location on object of the 5th embodiment;

Figure 16 is the luminous point distribution plan on the 5th embodiment photosensitive drums;

Figure 17 is the big logotype of the luminous point of diverse location on object of the 6th embodiment; And

Figure 18 is the luminous point distribution plan on the 6th embodiment photosensitive drums.

Embodiment

Please with reference to Fig. 1, be the synoptic diagram of the optical path of the short condensation distance two-slice type f theta eyeglass of laser scanning device of the present invention.The short condensation distance two-slice type f theta eyeglass of laser scanning device of the present invention comprises first eyeglass 131 with the first optical surface 131a and second optical surface 131b; Second eyeglass 132 with having the 3rd optical surface 132a and the 4th optical surface 132b is applicable to laser scanning device.Among the figure, laser scanning device mainly comprises LASER Light Source 11, polygonal rotating mirror 10, cylindrical mirror 16, and in order to the object of sensitization, in the drawings, object is implemented with photosensitive drums (drum) 15.The light beam 111 that LASER Light Source 11 is produced projects on the polygonal rotating mirror 10 through behind the cylindrical mirror 16.And polygonal rotating mirror 10 has a plurality of reflecting optics (in the drawings, being five reflecting optics), and each face reflecting optics is that rotating shaft is rotated with the central rotating shaft of polygonal rotating mirror 10, and light beam 111 is reflected into scanning ray 113a, 113b and 113c.What wherein scanning ray 113a, 113b, the 113c projection on directions X was claimed is sub scanning direction (subscanning direction); What the projection on the Y direction was claimed is main scanning direction (main scanningdirection); Scanning ray 113c and 113b are after the 4th optical surface 132b of second eyeglass penetrates; On photosensitive drums 15, form high order end (left end) and low order end (right end) respectively, the distance between these two ends is valid window 3 (effective window) distance, and is as shown in Figure 2; Can carbon dust heat be needed on the paper at the interior luminous point 2 of valid window 3 distances, and the original data are printed.

Please with reference to Fig. 1 and Fig. 2, wherein Fig. 2 is the optical path figure through the scanning ray of first eyeglass and second eyeglass.When LASER Light Source 11 begins to give off laser beam 111; Be reflected into scanning ray via polygonal rotating mirror 10; When scanning ray is reflected by the first optical surface 131a of first eyeglass 131 and the second optical surface 131b during through first eyeglass 131, it is the scanning ray of linear relationship with the time with the time that the distance that polygonal rotating mirror 10 is reflected becomes the scanning ray of nonlinear relationship to convert distance to.After scanning ray is through first eyeglass 131 and second eyeglass 132; Optical property by the first optical surface 131a, the second optical surface 131b, the 3rd optical surface 132a, the 4th optical surface 132b; Scanning ray is focused on the photosensitive drums 15, and on photosensitive drums 15, form the luminous point (Spot) 2 of row.Wherein, d ₀For cylindrical mirror 16 at the optical surface of polygonal rotating mirror 10 minor increment (on figure, showing), d along laser beam center to polygonal rotating mirror 10 catoptrons ₁Be the spacing of polygonal rotating mirror 10 to first optical surface 131a, d ₂Be the spacing of first optical surface 131a to the second optical surface 131b, d ₃Be the spacing of the second optical surface 131b to the, three optical surface 132a, d ₄Be the spacing of the 3rd optical surface 132a to the four optical surface 132b, d ₅Be the spacing of the 4th optical surface 132b to photosensitive drums 15, R ₁Be the radius-of-curvature (Curvature) of the first optical surface 131a, R ₂Be the radius-of-curvature of the second optical surface 131b, R ₃Be the radius-of-curvature of the 3rd optical surface 132a, R ₄It is the radius-of-curvature of the 4th optical surface 132b.

The 4th optical surface 132b is on main scanning direction, and is for having the optical surface of the point of inflexion, as shown in Figure 3; On scanning center's axle; Its convex surface is towards polygonal rotating mirror 10 sides, after leaving scanning center's beam warp and crossing point of inflexion P, then becomes its concave surface towards polygonal rotating mirror 10 sides.

Please with reference to Fig. 4, for after scanning ray is incident upon on the photosensitive drums, the synoptic diagram that spot areas (spot area) changes with the difference of launching position.After scanning ray 113a sees through first eyeglass 131 and second eyeglass 132 along main scanning direction; Be incident upon 15 last times of photosensitive drums; Because of the angle that is incident in first eyeglass 131 and second eyeglass 132 is zero; So the deviation ratio that on main scanning direction, is produced is minimum, its luminous point 2a that images on the photosensitive drums 15 has a similar circular external shape.When scanning ray 113b and 113c see through first eyeglass 131 and second eyeglass, 132 backs and be incident upon 15 last times of photosensitive drums; Non-vanishing because of being incident in first eyeglass 131 and second eyeglass 132 and the formed angle of scanning center's axle; So on main scanning direction, will produce deviation ratio, be big than the formed luminous point of scanning ray 113a and cause the projected length on main scanning direction; This kind situation can take place at sub scanning direction too, departs from the scanning ray 113b of scanning ray 113a, and the formed luminous point of 113c also will be bigger.So the luminous point 2b and the 2c that image on the photosensitive drums 15 are one type of ellipse, and the area of 2b, 2c is greater than 2a.Among the figure; Sa0 and Sb0 are the luminous point of scanning ray on polygonal rotating mirror 10 reflectings surface at root mean square radius (Root means square of spot size radius on target), Sa and the Sb of main scanning direction (Y direction) and sub scanning direction (directions X) the root mean square radius for size directions X of luminous point on object and Y direction; Smax, Y are that arbitrary luminous point is at the maximum radius of main scanning direction.

Please refer to Fig. 5, for scanning ray is incident upon valid window and the synoptic diagram of maximum valid window angle (effective window angle) β on the photosensitive drums 15.Penetrate the 4th optical surface 132b of second eyeglass 132 as high order end scanning ray 113c after, this scanning ray 113c be parallel to the included angle of straight line of scanning center's axle, be the maximal value at valid window angle.For reaching the purpose of the volume that dwindles laser scanning device, can promptly shorten optically focused apart from realizing by the image-forming range that shortens spinning polygonal mirror 10 to photosensitive drums 15.For shortening the optically focused distance; Remove the materials used optical design key elements such as (refractive index, Abbe numbers) of optical characteristics, first eyeglass 131 and second eyeglass 132 of four optical surfaces that can change first eyeglass 131 and second eyeglass 132; To shorten optically focused outside (d1+d2+d3+d4+d5), also can improve the numerical value of maximum valid window angle β in addition, the opening angle of scanning is increased; Relation between the distance of the maximum valid window angle β and second eyeglass 132 to the photosensitive drums 15 is suc as formula shown in (1); When strengthening the β value, under fixing valid window, can effectively shorten y _aValue.

$\mathrm{\β}={\tan }^{-1}\left(\frac{y_b}{y_a}\right)---\left(1\right)$

Wherein, y _aOn main scanning direction (Y direction), least significant end scanning ray (high order end scanning ray 113c or low order end scanning ray 113b) outgoing is parallel to the distance of scanning center's axle to photosensitive drums 15 imaging surfaces, y in the 4th optical surface 132b of second eyeglass 132 _bBe the sub scanning direction directions X

The distance of least significant end scanning ray (high order end scanning ray 113c or low order end scanning ray 113b) outgoing in the 4th optical surface 132b of second eyeglass 132 to photosensitive drums 15 imaging surfaces.

In sum; Short condensation distance two-slice type f theta eyeglass of the present invention can the scanning ray of polygonal rotating mirror 10 reflection be distorted (distortion) revise, and the nonlinear relationship of time-angular velocity that each projected light is positioned at the spacing of object changes into the linear relationship of time-distance; At main scanning direction and sub scanning direction; Scanning ray is in sub scanning direction (directions X) each angle with the beam radius process f Theta lens of main scanning direction (Y direction); Can on imaging surface, produce uniform spot; Remove the resolution that meets demand can be provided, and can effectively shorten the optically focused distance, to reduce the volume of laser scanning device.

For reaching above-mentioned effect; Short condensation distance two-slice type f theta eyeglass of the present invention is at the first optical surface 131a of first eyeglass 131 or the 3rd optical surface 132a or the 4th optical surface 132b of the second optical surface 132a and second eyeglass 132; On main scanning direction (Y) direction or sub scanning direction (directions X); Can use the design of sphere curved surface or non-spherical surface, if use the non-spherical surface design, its non-spherical surface is with following surface equation formula:

1: horizontal picture surface equation formula (Anamorphic equation

$Z=\frac{\left(\mathrm{Cx}\right)X^2+\left(\mathrm{Cy}\right){\mathrm{<figure-callout\; id="2"\; label="Y"\; filenames="H2009101596497E00021.png"\; state="\{\{state\}\}">Y</figure-callout>}}^2}{1+\sqrt{1-(1+\mathrm{Kx}){\left(\mathrm{Cx}\right)}^2{X}^2-(1+\mathrm{Ky}){\left(\mathrm{Cy}\right)}^2{\mathrm{<figure-callout\; id="2"\; label="Y"\; filenames="H2009101596497E00021.png"\; state="\{\{state\}\}">Y</figure-callout>}}^2}}+A_R{[(1-A_P)X^2+(1+A_P)Y^2]}^2+$

$B_R{[(1-B_P)X^2+(1+B_P)Y^2]}^3+C_R{[(1-C_P)X^2+(1+C_P)Y^2]}^4+$

$D_R{[(1-D_P)X^2+(1+D_P)Y^2]}^5---\left(2\right)$

Wherein, Z be on the eyeglass any point with the distance (SAG) in scanning center's direction of principal axis to 0 section; C _xWith C _yBe respectively the curvature (curvature) of directions X and Y direction; K _xWith K _yBe respectively the circular cone coefficient (Conic coefficient) of directions X and Y direction; A _R, B _R, C _RWith D _RBe respectively the circular cone deformation coefficient (deformation from the conic) with ten powers four times, six times, for eight times of rotation symmetry (rotationally symmetric portion); A _P, B _P, C _PWith D _PBe respectively the circular cone deformation coefficient (deformation from the conic) of four times, six times, eight times, ten times powers of non-rotation symmetry (non-rotationally symmetric components); Work as C _x=C _y, K _x=K _yAnd A _P=B _p=C _p=D _p=0, then be reduced to single aspheric surface.

2: ring is as surface equation formula (Torical equation)

$Z=\mathrm{Zy}+\frac{\left(\mathrm{Cxy}\right){\mathrm{<figure-callout\; id="2"\; label="X"\; filenames="H2009101596497E00021.png"\; state="\{\{state\}\}">X</figure-callout>}}^2}{1+\sqrt{1-{\left(\mathrm{Cxy}\right)}^2{\mathrm{<figure-callout\; id="2"\; label="X"\; filenames="H2009101596497E00021.png"\; state="\{\{state\}\}">X</figure-callout>}}^2}}$ $\mathrm{Cxy}=\frac{1}{(1/\mathrm{Cx})-\mathrm{Zy}}$

$\mathrm{Zy}=\frac{\left(\mathrm{Cy}\right){\mathrm{<figure-callout\; id="2"\; label="Y"\; filenames="H2009101596497E00021.png"\; state="\{\{state\}\}">Y</figure-callout>}}^2}{1+\sqrt{1-(1+\mathrm{Ky}){\left(\mathrm{Cy}\right)}^2{\mathrm{<figure-callout\; id="2"\; label="Y"\; filenames="H2009101596497E00021.png"\; state="\{\{state\}\}">Y</figure-callout>}}^2}}+B_4{Y}^4+B_6{Y}^6+B_8{Y}^8+B_{10}{Y}^{10}---\left(3\right)$

Wherein, Z be on the eyeglass any point with the distance (SAG) in scanning center's direction of principal axis to 0 section; C _yWith C _xThe curvature (curvature) of difference Y direction and directions X; K _yCircular cone coefficient (Conic coefficient) for the Y direction; B ₄, B ₆, B ₈With B ₁₀It is the coefficient (4th～10th order coefficients) of four times, six times, eight times, ten times powers.

For making scanning ray sweep velocity such as on the imaging surface on the object, keep, for example, in two identical time intervals, the spacing of keeping two luminous points equates; Short condensation distance two-slice type f theta eyeglass of the present invention can be with scanning ray 113a between the scanning ray 113b; Carry out the correction of scanning ray emergence angle by first eyeglass 131 and second eyeglass 132; Make two scanning rays in the identical time interval, after the shooting angle correction, the distance of two luminous points that on the photosensitive drums 15 of imaging, form equates; Promptly be imaged on the luminous point size homogenising (being limited to meets in the scope of resolution requirement) on the photosensitive drums 15, to obtain best parsing effect.

Short condensation distance two-slice type f theta eyeglass of the present invention comprises; Start at by polygonal rotating mirror 10; Have first eyeglass 131 and second eyeglass 132, wherein first eyeglass 131 has the first optical surface 131a and the second optical surface 131b, and second eyeglass 132 has the 3rd optical surface 131a and the 4th optical surface 131b.On the main scanning direction of scanning center's axle; First eyeglass is that crescent eyeglass with positive diopter, second eyeglass are for having negative dioptric eyeglass; The concave surface of first, second, third optical surface (131a, 131b, 132a) is towards polygonal rotating mirror 10 sides; The 4th optical surface 132b has the point of inflexion and its convex surface towards polygonal rotating mirror side 10; Can convert the scanning ray luminous point that the angle of each scanning ray of polygonal rotating mirror 10 reflection and time are nonlinear relationship to distance and linear scanning ray luminous point of time, and after the correction optical distortion, focus on the object.Wherein, the first optical surface 131a, the second optical surface 131b, the 3rd optical surface 132a and the 4th optical surface 132b are aspheric optical surface on main scanning direction.In addition, the first optical surface 131a, the second optical surface 131b, the 3rd optical surface 132a and the 4th optical surface 132b can have at least one to be the optical surface that aspheric surface constituted at sub scanning direction.Further, in the optical design of first eyeglass 131 and second eyeglass 132, two-chip type f theta lens of the present invention, further satisfy the condition with following formula (4) and formula (5) in airspace and maximum valid window angle β:

$0.6\&le;\frac{d_1+d_3+d_5}{f_s}\&le;2.0---\left(4\right)$

0.4557≤tan(β)≤0.7265 (5)

Further satisfy the condition of formula (6) at main scanning direction:

$0.22\&le;f_s\&CenterDot;(\frac{(n_{d1}-1)}{f_{\left(1\right)Y}}+\frac{(n_{d2}-1)}{f_{\left(2\right)Y}})\&le;1.2---\left(6\right)$

Satisfy the condition of formula (7) at sub scanning direction:

$-2.82\&le;f_s\&CenterDot;(\frac{(n_{d1}-1)}{f_{\left(1\right)X}}+\frac{(n_{d2}-1)}{f_{\left(2\right)X}})\&le;-0.31---\left(7\right)$

Wherein, d ₁Be the distance of 10 reflecting surface to the first eyeglasses of polygonal rotating mirror on scanning center's axle, 131 polygonal rotating mirror side optical surfaces, d ₃Be the distance of first eyeglass, 131 object side optical surface to the second eyeglasses, 132 polygonal rotating mirrors, 10 side optical surfaces on scanning center's axle, d ₅Be the distance of second eyeglass, 132 object side optical surface to objects on scanning center's axle, f _sBe the compound focal length of two-chip type f theta lens, β is maximum valid window angle, f _{(1) Y}Be the focal length of first eyeglass 131 at main scanning direction, f _{(2) Y}Be the focal length of second eyeglass 132 at main scanning direction, f _{(1) X}Be the focal length of first eyeglass 131 at sub scanning direction, f _{(2) X}Be the focal length of second eyeglass 132 at sub scanning direction, n _D1With n _D2Be respectively the refractive index of first eyeglass 131 and second eyeglass 132.

Moreover the formed luminous point size of two-chip type f theta lens of the present invention can be used η _MaxWith η _MinRatio represent η wherein _MaxGeometry luminous points and scanning how much peaked ratios of luminous point on photosensitive drums 15, η for scanning ray on polygonal rotating mirror 10 reflectings surface _MinBe the geometry luminous points of scanning ray on polygonal rotating mirror 10 reflectings surface and the ratio of scanning how much luminous point minimum value on photosensitive drums 15.η _MaxWith η _MinSatisfy condition respectively with following formula (8) and (9),

${\mathrm{\&eta;}}_{\max }=\frac{\max (S_b\&CenterDot;S_a)}{({\mathrm{<figure-callout\; id="0"\; label="S\; b"\; filenames="H2009101596497E00081.png,H2009101596497E00101.png"\; state="\{\{state\}\}">S</figure-callout>}}_b\&CenterDot;S_{a0})}\&le;0.05---\left(8\right)$

${\mathrm{\&eta;}}_{\min }=\frac{\min (S_b\&CenterDot;S_a)}{({\mathrm{<figure-callout\; id="0"\; label="S\; b"\; filenames="H2009101596497E00081.png,H2009101596497E00101.png"\; state="\{\{state\}\}">S</figure-callout>}}_b\&CenterDot;S_{a0})}\&le;0.005---\left(9\right)$

Wherein, S _aWith S _bBe respectively the root mean square radius of any luminous point of scanning ray formation on the photosensitive drums 15 at sub scanning direction and main scanning direction; δ is the ratio of smallest spot and maximum luminous point on the photosensitive drums 15, and η is the ratio of luminous point on luminous point and the photosensitive drums 15 of scanning ray on polygonal rotating mirror 10 reflectings surface; S _A0With S _B0For the luminous point of scanning ray on polygonal rotating mirror 10 reflectings surface respectively at the root mean square radius of sub scanning direction and main scanning direction.

For making the present invention clear and definite more full and accurate, enumerate preferred embodiment and cooperate following diagram, details are as follows with structure of the present invention and technical characterictic thereof:

The embodiment that is disclosed below the present invention; Be the explanation of being done to the main composition assembly of the short condensation distance two-slice type f theta eyeglass of laser scanning device of the present invention, the embodiment that is disclosed below therefore can be applicable to have in the laser scanning device of polygonal rotating mirror.But with regard to general laser scanning device, except disclosed two-chip type f theta lens, other structure can be known for having common knowledge the knowledgeable in the technical field under the present invention.The constituent components of the two-chip type f theta lens of disclosed laser scanning device is not limited to the following example structure that discloses, and just each constituent components of the two-chip type f theta lens of laser scanning device can change, revise even the equivalence change.For example: the radius-of-curvature design of first eyeglass 131 and second eyeglass 132, material are selected for use, spacing adjustment etc. do not limit by the following example.And for ease of explaining and compare that following embodiment all adopts the luminous point of scanning ray on the polygonal rotating mirror 10 to be respectively S at the root mean square radius of directions X and Y direction respectively _A0=47.89 (μ m) and S _B0The design of=641.49 (μ m), but not as limit.

< first embodiment >

The short condensation distance two-slice type f theta eyeglass of present embodiment is aspheric surface at second optical surface 131b of first eyeglass 131 and the 3rd optical surface 132a of second eyeglass 132, the curved surface of its optical surface of aspheric surface formulae design of use formula (2).On main scanning direction, be aspheric surface at first optical surface 131a of first eyeglass 131 and the 4th optical surface 132b of second eyeglass 132, the curved surface of its optical surface of aspheric surface formulae design of use formula (3).Its optical characteristics and aspheric surface parameter such as table one and table two, index path is as shown in Figure 6, and the point of inflexion of the 4th optical surface 132b is positioned at ψ=2.33 °.

Table one: the f θ optical characteristics of first embodiment

^*The expression aspheric surface

Table two: the optical surface aspheric surface parameter of first embodiment

The optical surface of the short condensation distance two-slice type f theta eyeglass that warp constitutes thus, f _{(1) Y}=88.111, f _{(2) Y}=-502.724, f _{(1) X}=-9.844, f _{(2) X}=24.685 (mm), its y _a=85.00, y _b=50.44 (mm), making maximal window bicker β=30.68 ° can become scanning ray with spot scan on the polygonal rotating mirror 10; In photosensitive drums 15 enterprising line focusings; Form less luminous point, and satisfy the condition of formula (4)～(7) and formula (8)～(9), shown in table three.On the photosensitive drums 15 with how much spot diameters (μ m) of the axle Z of scanning center axle, like table four at the luminous point of Y direction range sweep central shaft Y distance (mm); And the luminous point distribution plan of present embodiment and luminous point size shape figure are like Fig. 7 and shown in Figure 8.

Table three: first embodiment table that satisfies condition

Table four: luminous point maximum radius and root mean square radius table on the first embodiment photosensitive drums

< second embodiment >

The short condensation distance two-slice type f theta eyeglass of present embodiment is aspheric surface at second optical surface 131b of first eyeglass 131 and the 3rd optical surface 132a of second eyeglass 132, the curved surface of its optical surface of aspheric surface formulae design of use formula (2).On main scanning direction, be aspheric surface at first optical surface 131a of first eyeglass 131 and the 4th optical surface 132b of second eyeglass 132, the curved surface of its optical surface of aspheric surface formulae design of use formula (3).Its optical characteristics and aspheric surface parameter shown in table five and table six, index path such as Fig. 6, the point of inflexion of the 4th optical surface 132b is positioned at ψ=8.21 °.

Table five: the f θ optical characteristics of second embodiment

^*The expression aspheric surface

Table six: the optical surface aspheric surface parameter of second embodiment

The optical surface of the short condensation distance two-slice type f theta eyeglass that warp constitutes thus, f _{(1) Y}=84.264, f _{(2) Y}=-335.022, f _{(1) X}=-7.838, f _{(2) X}=26.919 (mm), its y _a=82.0, y _b=43.0 (mm), making maximal window bicker β=27.67 ° can become scanning ray with spot scan on the polygonal rotating mirror 10, in photosensitive drums 15 enterprising line focusings, forms less luminous point, and satisfies formula (4)～(7) and formula (8)～(9), shown in table seven.On the photosensitive drums 15 with how much spot diameters (μ m) of the axle Z of scanning center axle, shown in table eight at the luminous point of Y direction range sweep central shaft Y distance (mm).And the luminous point distribution plan of present embodiment and luminous point size shape figure are like Fig. 9 and shown in Figure 10.

Table seven: second embodiment table that satisfies condition

Table eight: luminous point maximum radius and root mean square radius table on the second embodiment photosensitive drums

< the 3rd embodiment >

The short condensation distance two-slice type f theta eyeglass of present embodiment is aspheric surface at second optical surface 131b of first eyeglass 131 and the 3rd optical surface 132a of second eyeglass 132, the curved surface of its optical surface of aspheric surface formulae design of use formula (2).Main scanning direction at the 4th optical surface 132b of the first optical surface 131a of first eyeglass 131 and second eyeglass 132 is aspheric surface, the curved surface of its optical surface of aspheric surface formulae design of use formula (3).Its optical characteristics and aspheric surface parameter such as table nine and table ten, index path is as shown in Figure 6, and the point of inflexion of the 4th optical surface 132b is positioned at ψ=6.57 °.

Table nine: the f θ optical characteristics of the 3rd embodiment

^*The expression aspheric surface

Table ten: the optical surface aspheric surface parameter of the 3rd embodiment

The optical surface of the short condensation distance two-slice type f theta eyeglass that warp constitutes thus, f _{(1) Y}=83.522, f _{(2) Y}=-357.438, f _{(1) X}=-12.477, f _{(2) X}=-357.434 (mm), its y _a=85.0 (mm), y _b=42.474 (mm), making maximal window bicker β=28.74 ° can become scanning ray with spot scan on the polygonal rotating mirror 10, in photosensitive drums 15 enterprising line focusings, forms less luminous point, and satisfies formula (4)～(7) and formula (8)～(9), shown in table ten one.On the photosensitive drums 15 with how much spot diameters (μ m) of the axle Z of scanning center axle, like table ten two at the luminous point of Y direction range sweep central shaft Y distance (mm); And the luminous point distribution plan of present embodiment and luminous point size shape figure are like Figure 11 and shown in Figure 12.

One: the three embodiment of table ten table that satisfies condition

Luminous point maximum radius and root mean square radius table on two: the three embodiment photosensitive drums of table ten

< the 4th embodiment >

The short condensation distance two-slice type f theta eyeglass of present embodiment is aspheric surface at second optical surface 131b of first eyeglass 131 and the 3rd optical surface 132a of second eyeglass 132, the curved surface of its optical surface of aspheric surface formulae design of use formula (2).Be aspheric surface at first optical surface 131a of first eyeglass 131 and the 4th optical surface 132b of second eyeglass 132 at main scanning direction, use the curved surface of formula (3) as its optical surface of aspheric surface formulae design.Its optical characteristics and aspheric surface parameter such as table ten three and table ten four, index path is as shown in Figure 6, and the point of inflexion of the 4th optical surface 132b is positioned at ψ=6.569 °.

The f θ optical characteristics of three: the four embodiment of table ten

^*The expression aspheric surface

The optical surface aspheric surface parameter of four: the four embodiment of table ten

The optical surface of the short condensation distance two-slice type f theta eyeglass that warp constitutes thus, f _{(1) Y}=133.630, f _{(2) Y}=-5116.737, f _{(1) X}=-0.445, f _{(2) X}=20.124 (mm), its y _a=85.0 (mm), y _b=42.474 (mm), making maximal window bicker β=26.55 ° can become scanning ray with spot scan on the polygonal rotating mirror 10, in photosensitive drums 15 enterprising line focusings, forms less luminous point 6, and satisfies formula (4)～(7) and formula (8)～(9), shown in table ten five.On the photosensitive drums 15 with how much spot diameters (μ m) of the axle Z of scanning center axle, shown in table ten six at the luminous point of Y direction range sweep central shaft Y distance (mm).And the luminous point distribution plan of present embodiment and luminous point size shape figure are like Figure 13 and shown in Figure 14.

Five: the four embodiment of table ten table that satisfies condition

Luminous point maximum radius and root mean square radius table on six: the four embodiment photosensitive drums of table ten

< the 5th embodiment >

The short condensation distance two-slice type f theta eyeglass of present embodiment is aspheric surface at second optical surface 131b of first eyeglass 131 and the 3rd optical surface 132a of second eyeglass 132, uses the curved surface of formula (2) as its optical surface of aspheric surface formulae design.The 4th optical surface 132b at first eyeglass, 131 first optical surface 131a, second eyeglass 132 is aspheric surface at main scanning direction, the curved surface of its optical surface of aspheric surface formulae design of use formula (3).Its optical characteristics and aspheric surface parameter such as table ten seven and table ten eight, index path is as shown in Figure 6, and the point of inflexion of the 4th optical surface 132b is positioned at ψ=2.04 °.

The f θ optical characteristics of seven: the five embodiment of table ten

^*The expression aspheric surface

The optical surface aspheric surface parameter of eight: the five embodiment of table ten

The optical surface of the short condensation distance two-slice type f theta eyeglass that warp is constituted thus, f _{(1) Y}=99.246, f _{(2) Y}=-1228.670, f _{(1) X}=-10.704, f _{(2) X}=106.623 (mm), its y _a=85.0, y _b=48.607 (mm); Make and maximal window bicker β=29.763 ° can spot scan on the polygonal rotating mirror 10 be become scanning ray, in photosensitive drums 15 enterprising line focusings; Form less luminous point; And satisfy formula (4)～(7) and formula (8)～(9), shown in table ten nine, on the photosensitive drums 15 with how much spot diameters (μ m) of the axle Z of scanning center axle, like table two ten at the luminous point of Y direction range sweep central shaft Y distance (mm); And the luminous point distribution plan of present embodiment and luminous point size shape figure are like Figure 15 and shown in Figure 16.

Nine: the five embodiment of table ten table that satisfies condition

Luminous point maximum radius and root mean square radius table on ten: the five embodiment photosensitive drums of table two

< the 6th embodiment >

The short condensation distance two-slice type f theta eyeglass of present embodiment is aspheric surface at second optical surface 131b of first eyeglass 131 and the 3rd optical surface 132a of second eyeglass 132, the curved surface of its optical surface of aspheric surface formulae design of use formula (2).Be aspheric surface, the curved surface of its optical surface of aspheric surface formulae design of use formula (3) at the first optical surface 131a of first eyeglass 131, the main scanning direction of second eyeglass 132 the 4th optical surface 132b.Its optical characteristics and aspheric surface parameter such as table two 11 and table two 12, index path is as shown in Figure 6, and the point of inflexion of the 4th optical surface 132b is positioned at ψ=6.30 °.

Table two 11: the f θ optical characteristics of the 6th embodiment

^*The expression aspheric surface

Table two 12: the optical surface aspheric surface parameter of the 6th embodiment

The optical surface of the short condensation distance two-slice type f theta eyeglass that warp constitutes thus, f _{(1) Y}=82.522, f _{(2) Y}=-300.994, f _{(1) X}=-8.349, f _{(2) X}=21.894 (mm), its y _a=82.3, y _b=49.273 (mm), making maximal window bicker β=30.908 ° can become scanning ray with spot scan on the polygonal rotating mirror 10; In photosensitive drums 15 enterprising line focusings; Form less luminous point, and satisfy formula (4)～(7) and formula (8)～(9), shown in table two 13.On the photosensitive drums 15 with how much spot diameters (μ m) of the axle Z of scanning center axle, shown in table two 14 at the luminous point of Y direction range sweep central shaft Y distance (mm).And the luminous point distribution plan of present embodiment and luminous point size shape figure are like Figure 17 and shown in Figure 180.

Table two 13: the 6th embodiment table that satisfies condition

Table two 14: luminous point maximum radius and root mean square radius table on the 6th embodiment photosensitive drums

By the above embodiments explanation, the present invention can reach following effect at least:

(1) by the setting of short condensation distance two-slice type f theta eyeglass of the present invention; Can be with polygonal rotating mirror in speed such as imaging surface glazing dot spacing is non-scanning phenomenon; Speed scanning such as be modified to; Make laser beam in the scanning of the speed such as projection work of imaging surface, make to image in the two adjacent spot spacings that form on the object and equate.

(2) by the setting of short condensation distance two-slice type f theta eyeglass of the present invention, can distort and revise at main scanning direction and sub scanning direction scanning ray, make the luminous point on the object that focuses on imaging be able to dwindle.

(3) by the setting of short condensation distance two-slice type f theta eyeglass of the present invention, can distort and revise at main scanning direction and sub scanning direction scanning ray, make the luminous point size homogenising that is imaged on the object.

(4) by the setting of short condensation distance two-slice type f theta eyeglass of the present invention, can effectively shorten the optically focused distance, make the volume of laser scanning device be able to reduce, reach the requirement of miniaturization.

The above is merely preferred embodiment of the present invention, only is illustrative for the purpose of the present invention, and nonrestrictive; Those skilled in the art is understood, and in spirit that claim of the present invention limited and scope, can carry out many changes to it, revise, even equivalence changes, but all will fall in protection scope of the present invention.

Claims (4)

1. short condensation distance two-slice type f theta eyeglass, it is applicable to laser scanning device, this laser scanning device comprise at least one be used for emission of lasering beam light source, be used for becoming the polygonal rotating mirror and of scanning ray to be used for the object of sensitization laser beam flying; This two-chip type f theta lens has one first eyeglass and one second eyeglass; And start in regular turn by this polygonal rotating mirror; This first eyeglass is that meniscus has one first optical surface and one second optical surface; This second eyeglass has one the 3rd optical surface and one the 4th optical surface, it is characterized in that: this two-chip type f theta lens is on the main scanning direction of scanning center's axle, and this first eyeglass is that tool positive diopter, this second eyeglass are the negative diopter of tool; The concave surface of this first optical surface, this second optical surface and the 3rd optical surface is towards the polygonal rotating mirror side, the 4th optical surface have the point of inflexion and on scanning center's axle its convex surface for towards the polygonal rotating mirror side; This first optical surface, this second optical surface, the 3rd optical surface and the 4th optical surface are aspheric surface at main scanning direction, and satisfy following condition:

$0.6\&le;\frac{d_1+d_3+d_5}{f_s}\&le;2.0;$

0.4557≤tan(β)≤0.7265；

Wherein, d ₁Distance, d for the polygonal rotating mirror side optical surface of reflecting surface to this first eyeglass of this polygonal rotating mirror on scanning center's axle ₃For distance, the d5 of this polygonal rotating mirror side optical surface of this object side optical surface to this second eyeglass of this first eyeglass on scanning center's axle is distance, the f of this second eyeglass object side optical surface to this object on scanning center's axle _sBe the compound focal length of this two-chip type f theta lens, β penetrates the scanning ray and the angle that is parallel to the straight line of scanning center's axle behind the 4th optical surface of this second eyeglass for the high order end scanning ray.

2. short condensation distance two-slice type f theta eyeglass as claimed in claim 1 is characterized in that, on main scanning direction, further satisfies following condition:

$0.22\&le;f_s\&CenterDot;(\frac{(n_{d1}-1)}{f_{\left(1\right)Y}}+\frac{(n_{d2}-1)}{f_{\left(2\right)Y}})\&le;1.2;$

Wherein, f _{(1) Y}Be focal length, the f of this first eyeglass at main scanning direction _{(2) Y}Be focal length, the f of this second eyeglass at main scanning direction _sCompound focal length, n for two-chip type f theta lens _D1With n _D2Refractive index for this first eyeglass and this second eyeglass.

3. short condensation distance two-slice type f theta eyeglass as claimed in claim 1 is characterized in that, further satisfies following condition at sub scanning direction:

$-2.82\&le;f_s\&CenterDot;(\frac{(n_{d1}-1)}{f_{\left(1\right)X}}+\frac{(n_{d2}-1)}{f_{\left(2\right)X}})\&le;-0.31;$

Wherein, f _{(1) X}Be focal length, the f of this first eyeglass at sub scanning direction _{(2) X}Be focal length, the f of this second eyeglass at sub scanning direction _sCompound focal length, n for this two-chip type f theta lens _D1With n _D2Refractive index for this first eyeglass and this second eyeglass.

4. short condensation distance two-slice type f theta eyeglass as claimed in claim 1 is characterized in that, the ratio of maximum luminous point satisfies respectively with the ratio of smallest spot on this object on this object:

${\mathrm{\&eta;}}_{\max }=\frac{\max (S_b\&CenterDot;S_a)}{(S_{b0}\&CenterDot;S_{a0})}\&le;0.05;$

${\mathrm{\&eta;}}_{\min }=\frac{\min (S_b\&CenterDot;S_a)}{(S_{b0}\&CenterDot;S_{a0})}\&le;0.005;$

Wherein, S _A0With S _B0Be the luminous point of scanning ray on the polygonal mirror reflecting surface of this rotation root mean square radius, S at sub scanning direction and main scanning direction _aWith S _bAny luminous point that forms for scanning ray on the reflecting surface of this polygonal rotating mirror is at root mean square radius, the η of sub scanning direction and main scanning direction _MaxBe the luminous point of scanning ray on this polygonal rotating mirror reflecting surface and ratio, the η of scanning maximum luminous point on this object _MinBe the luminous point of scanning ray on this polygonal rotating mirror reflecting surface and the ratio of scanning smallest spot on this object.

Images