CN201345004Y - Two-piece type f theta lens of micro-electromechanical laser scanning device - Google Patents

Abstract

The utility model discloses a two formula f theta lenses of micro-electromechanical laser scanning device, wherein first lens constitute for biconvex type lens, the second lens is crescent and the concave surface is in the micro-electromechanical speculum side, wherein first lens has two optical surfaces, it constitutes for the aspheric surface to have an optical surface at the main scanning direction at least, the second lens has two optical surfaces, it constitutes for the aspheric surface to have an optical surface at the main scanning direction at least, the effect of first lens and second lens mainly converts the angle of micro-electromechanical speculum and time to the scanning light spot of nonlinear relation into the scanning light spot that distance and time are linear relation, and revise on the object of spotlight, and first lens and second lens all satisfy specific optical condition, in order to reach the purpose of linear scanning effect and high resolution scanning.

Description

The two-chip type f theta lens of MEMS laser scanning device

Technical field

The utility model relates to a kind of two-chip type f theta lens of MEMS laser scanning device, relate in particular in order to correction and be the mems mirror of simple harmonic characteristic motion and produce the angle variable quantity that becomes sine relation in time, to reach the two-chip type f theta lens of the desired linear sweep effect of laser scanning device.

Background technology

The present employed laser scanning device of laser printer LBP (Laser Beam Print) (LSU:Laser Scanning Unit), utilize the scanning motion (1aser beam scanning) of polygonal mirror (polygon mirror) to control laser beam of high speed rotating, as U.S. Pat 7079171, US6377293, US6295116, or as described in the patent I198966 of Taiwan.The following summary of its principle: utilize semiconductor laser give off laser beam (laser beam), earlier via collimating mirror (collimator), form parallel beam again via an aperture (aperture), and parallel beam passes through cylindrical mirror (cylindrical lens) afterwards again, can be at the width on the Y-axis of sub scanning direction (sub scanning direction) along the parallel focusing of parallel direction of the X-axis of main scanning direction (main scanningdirection) and form linear image (line image), be projected to again on the polygonal mirror of high speed rotating, and evenly being provided with polygonal mirror on the polygonal mirror continuously, it just is positioned at or approaches the focal position of above-mentioned linear image (line image).Projecting direction by polygonal mirror control laser beam, when continuous a plurality of catoptrons during at high speed rotating can be incident upon on the catoptron laser beam along the parallel direction of main scanning direction (X-axis) with identical tarnsition velocity (angular velocity) deflective reflector to f θ linear sweep eyeglass, and f θ linear sweep eyeglass is arranged at the polygonal 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 be focused into elliptical spot and be incident upon light receiving surface (photoreceptor drum, be imaging surface) on, and reach the requirement of linear sweep (scanning linearity).Yet can there be following point in existing laser scanning device (LSU) in the use:

(1), the manufacture difficulty height and the price of rotary multi mirror be not low, increases the cost of manufacture of LSU relatively.

(2), polygonal mirror must possess high speed rotating (as 40000 rev/mins) function, precision requirement is high again, so that the minute surface Y-axis width of reflecting surface as thin as a wafer on the general polygonal mirror, make and all need set up cylindrical mirror (cylindrical lens) among the existing LSU, so that increase member cost and assembling operation flow process so that laser beam can be focused into line (becoming a bit on the Y-axis) through cylindrical mirror and be incident upon on the catoptron of polygonal mirror again.

(3), existing polygonal mirror must high speed rotating (as 40000 rev/mins), cause Rotation Noise and improve relatively, and polygonal mirror must expend the long period from starting to working speed, increases the stand-by period after the start.

(4), in the package assembly of existing LSU, the laser beam central shaft that is projected to the polygonal mirror catoptron is not the central rotating shaft over against polygonal mirror, so that when the f Theta lens that design matches, need consider simultaneously polygonal mirror from axle deviation (offaxis deviation) problem, increase the design of f Theta lens relatively and make to go up trouble.

In recent years since,, developed the mems mirror (MEMS mirror) of a kind of swing type (oscillatory) at present on the market, control laser beam flying in order to replace existing polygonal mirror in order to improve the problem of existing LSU package assembly.Mems mirror is torque oscillation device (torsion oscillators), has reflector layer on its top layer, can be by vibration swing reflector layer, the light reflection is scanned, to can be applicable to laser scanning device (the laser scanning unit of imaging system (imaging system), scanner (scanner) or laser printer (laser printer) future, be called for short LSU), its scan efficiency (Scanning efficiency) can be higher than traditional polygonal rotating mirror.As U.S. Pat 6,844,951, US6,956,597, produce at least one drive signal, the resonant frequency of a plurality of mems mirrors of its driving frequency convergence, and with the drive mems mirror to produce scanning pattern, similarly to also have U.S. Pat 7,064,876, US7,184,187, US7,190,499, US2006/0113393; Or as Taiwan patent TW M253133, it between collimating mirror and the f Theta lens, utilizes mems mirror to replace existing rotary multi mirror, with the projecting direction of control laser beam in the LSU modular structure; Or as Jap.P. JP 2006-201350 etc.This mems mirror has that assembly is little, and velocity of rotation is fast, advantage of low manufacturing cost.Yet because mems mirror, after receiving driven, will do simple harmonic motion, and the mode of this simple harmonic motion (harmonicmotion) is that time and angular velocity are sine relation, and be projeced into mems mirror, its after reflection reflection angle θ and the pass of time t be:

θ(t)＝θ _s·sin(2π·f·t)(1)

Wherein: f is the sweep frequency of mems mirror; θ _sFor laser beam behind mems mirror, the scanning angle of monolateral maximum.

Therefore, Δ t under the identical time interval, pairing reflection angle become sine function (Sinusoidal) to change with the time, and promptly when identical time interval Δ t, reflection angle is changed to: Δ θ (t)=θ _s(sin (2 π ft ₁)-sin (2 π ft ₂)), and be nonlinear relationship with the time, promptly when the light of this reflection is incident upon object with different angles, the spot distance that is produced in the identical time interval is at interval and inequality and increasing or decreasing in time.

For example, when the pendulum angle of mems mirror is positioned at sinusoidal wave crest and trough, angle variable quantity is increasing or decreasing in time, different with the mode of motion that existing polygonal mirror becomes constant angular velocity to rotate, if use existing f Theta lens on the laser scanning device with mems mirror (LSU), can't revise the angle variable quantity that mems mirror produces, and cause the laser light velocity that is incident upon on the imaging surface will produce speed scanning phenomenon such as non-and produce the imaging deviation that is positioned on the imaging surface.Therefore, for the laser scanning device that mems mirror constituted, abbreviate MEMS laser scanning device (MEMSLSU) as, its characteristic is that laser beam is via after the mems mirror scanning, form the not equal angular scanning ray of constant duration, therefore development can be used in the f Theta lens of MEMS laser scanning device to revise scanning ray, make can be on object correct imaging, disclose use polynomial surface (polynomial surface) as U.S. Pat 7,184187 and carry out angle variable quantity at main scanning direction; But because lasing aperture and nonideal minimum circle, and its cross section is flat-shaped ellipse, only by the main scanning direction correction, still difficulty reaches accuracy requirement; Therefore development can be revised the f Theta lens of scanning ray simultaneously at main sweep and sub scanning direction, will become urgently required.

The utility model content

The purpose of this utility model is to provide a kind of two-chip type f theta lens of MEMS laser scanning device, this two-chip type f theta lens is started in regular turn from mems mirror, first eyeglass is constituted by lenticular eyeglass, second eyeglass is constituted at the eyeglass of mems mirror side by crescent and concave surface, can be with the correct imaging on object of scanning ray that mems mirror reflected, and reach the desired linear sweep effect of laser scanning device.

Another purpose of the present utility model is to provide a kind of two-chip type f theta lens of MEMS laser scanning device, in order to dwindling the area of the luminous point (spot) that is incident upon on the object, and reaches the effect that improves resolution.

Another purpose of the present utility model is to provide a kind of two-chip type f theta lens of MEMS laser scanning device, the modifying factor that can distort scanning ray departs from optical axis, and cause skew to increase at main scanning direction and sub scanning direction, make the luminous point that images in photosensitive drums be deformed into similar oval-shaped problem, and make each imaging luminous point size be able to homogenising, promote the effect of separating picture element amount (resolution quality) and reach.

Therefore, the two-chip type f theta lens of the utility model MEMS laser scanning device, be applicable to the light source that comprises at least one emission of lasering beam, swinging with resonance becomes the laser beam reflection of light emitted the mems mirror of scanning ray, with imaging on object; For laser printer, this object often is a photosensitive drums (drum), that is, treat that the luminous point of imaging gives off laser beam via light source, via scanning about mems mirror, the mems mirror reflection lasering beam forms scanning ray, scanning ray via two-chip type f theta lens angle correction of the present utility model and position after, on photosensitive drums, form luminous point (spot), because photosensitive drums scribbles photosensitizer, can respond to carbon dust it is gathered on the paper, so data can be printed.

Two-chip type f theta lens of the present utility model comprises first eyeglass and second eyeglass of starting in regular turn from mems mirror, wherein first eyeglass has first optical surface and second optical surface, first optical surface and second optical surface, having an optical surface at least at main scanning direction is aspheric surface, mainly will carry out the mems mirror of simple harmonic motion, the speed scanning phenomenon such as non-of successively decreasing by originally increasing in time or increasing progressively at imaging surface glazing dot spacing, speed scanning such as be modified to, make speed such as the projection work scanning of laser beam at imaging surface.Second eyeglass has the 3rd optical surface and the 4th optical surface, the 3rd optical surface and the 4th optical surface, having an optical surface at least at main scanning direction is aspheric surface, it is poor mainly in photosensitive drums on to be formed into kine bias at main scanning direction and sub scanning direction because of the skew optical axis causes in order to the homogenising scanning ray, and the scanning ray correction of first eyeglass is concentrated on the object.

Description of drawings

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

Fig. 2 is the graph of a relation of mems mirror scanning angle θ and time t;

Fig. 3 is optical path figure and the symbol description figure by the scanning ray of first eyeglass and second eyeglass;

Fig. 4 is for after scanning ray is incident upon on the photosensitive drums, the synoptic diagram that spot areas changes with the difference of launching position;

Fig. 5 is the graph of a relation of the Gaussian distribution and the light intensity of light beam;

Fig. 6 is the optical path figure of the utility model by the scanning ray embodiment of first eyeglass and second eyeglass;

Fig. 7 is the luminous point synoptic diagram of first embodiment;

Fig. 8 is the luminous point synoptic diagram of second embodiment;

Fig. 9 is the luminous point synoptic diagram of the 3rd embodiment;

Figure 10 is the luminous point synoptic diagram of the 4th embodiment; And

Figure 11 is the luminous point synoptic diagram of the 5th embodiment.

[primary clustering symbol description]

10: mems mirror; 11: LASER Light Source;

111: light beam;

113a, 113b, 113c, 114a, 114b, 115a, 115b: scanning ray;

131: the first eyeglasses; 132: the second eyeglasses;

14a, 14b: photoelectric sensor; 15: photosensitive drums;

16: cylindrical mirror; 2,2a, 2b, 2c: luminous point;

3: the effective scanning window.

Embodiment

With reference to Fig. 1, be the optical path synoptic diagram of the two-chip type f theta lens of the utility model MEMS laser scanning device.The two-chip type f theta lens of the utility model MEMS laser scanning device comprises first eyeglass 131 with the first optical surface 131a and second optical surface 131b, with second eyeglass 132, to be applicable to MEMS laser scanning device with the 3rd optical surface 132a and the 4th optical surface 132b.Among the figure, MEMS laser scanning device mainly comprises LASER Light Source 11, mems mirror 10, cylindrical mirror 16, two photoelectric sensor 14a, 14b, and in order to the object of sensitization.In the drawings, object is to implement with photosensitive drums (drum) 15.The light beam 111 that LASER Light Source 11 is produced projects on the mems mirror 10 by behind the cylindrical mirror 16.And the mode that mems mirror 10 swings with resonance is reflected into scanning ray 113a, 113b, 113c, 114a, 114b, 115a, 115b with light beam 111. Wherein scanning ray 113a, 113b, 113c, 114a, 114b, 115a, 115b are referred to as sub scanning direction (subscanning direction) in the projection of directions X, projection in the Y direction is referred to as main scanning direction (main scanningdirection), and mems mirror 10 scanning angles are θ _c

With reference to Fig. 1 and Fig. 2, wherein Fig. 2 is the graph of a relation of mems mirror scanning angle θ and time t.Because mems mirror 10 does simple harmonic motion, its movement angle is sinusoidal variations in time, so the ejaculation angle of scanning ray and time are nonlinear relationship.Crest a-a ' as shown and trough b-b ', its pendulum angle is significantly less than wave band a-b and a '-b ', and the unequal phenomenon of this angular velocity causes scanning ray to produce the imaging deviation easily on photosensitive drums 15.Therefore, photoelectric sensor 14a, 14b are arranged within mems mirror 10 maximum scans angle ± θ c, and its angle is ± θ p that laser beam is begun to be reflected by mems mirror 10 by the crest place of Fig. 2, is equivalent to the scanning ray 115a of Fig. 1 this moment; When photoelectric sensor 14a detected scanning light beam, expression mems mirror 10 swung to+θ p angle, was equivalent to the scanning ray 114a of Fig. 1 this moment; When mems mirror 10 scanning angles change as during a point of Fig. 2, are equivalent to scanning ray 113a position at this moment; LASER Light Source 11 will be driven and give off laser beam 111 this moment, and when being scanned up to the b point of Fig. 2, be equivalent to this moment (being equivalent to ± the interior laser beam of being sent by LASER Light Source 11 111 of θ n angle) till the scanning ray 113b position; When mems mirror 10 produces counter shaking, as being driven by LASER Light Source 11 in wave band a '-b ' time and beginning to give off laser beam 111; So finish one-period.

With reference to Fig. 1 and Fig. 3, wherein Fig. 3 is the optical path figure by the scanning ray of first eyeglass and second eyeglass.Wherein, ± θ n is the effective scanning angle, when the rotational angle of mems mirror 10 enter ± during θ n, LASER Light Source 11 begins to give off laser beam 111, be reflected into scanning ray via mems mirror 10, when scanning ray is reflected by the first optical surface 131a of first eyeglass 131 and the second optical surface 131b during by first eyeglass 131, it is the scanning ray of linear relationship with the time with the time that the distance that mems mirror 10 is reflected becomes the scanning ray of nonlinear relationship to convert distance to.After scanning ray is by 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 a luminous point (Spot) 2 that is listed as.On photosensitive drums 15, two farthest the spacing of luminous point 2 be called effective scanning window 3.Wherein, d ₁Spacing, d for mems mirror 10 to first optical surface 131a ₂Be spacing, the d of first optical surface 131a to the second optical surface 131b ₃Be spacing, the d of the second optical surface 131b to the, three optical surface 132a ₄Be spacing, the d of the 3rd optical surface 132a to the four optical surface 132b ₅Be spacing, the R of the 4th optical surface 132b to photosensitive drums 15 ₁Be radius-of-curvature (Curvature), the R of the first optical surface 131a ₂Be radius-of-curvature, the R of the second optical surface 131b ₃Be radius-of-curvature, the R of the 3rd optical surface 132a ₄It is the radius-of-curvature of the 4th optical surface 132b.

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.When scanning ray 113a is incident upon photosensitive drums 15 after optical axis direction sees through first eyeglass 131 and second eyeglass 132, because of the angle that is incident in first eyeglass 131 and second eyeglass 132 is zero, so in the deviation ratio that main scanning direction produced is zero, therefore the luminous point 2a that images on the photosensitive drums 15 is similar circle.When scanning ray 113b and 113c see through first eyeglass 131 and second eyeglass, 132 backs and when being incident upon photosensitive drums 15, non-vanishing because of being incident in first eyeglass 131 and second eyeglass 132 and the formed angle of optical axis, so non-vanishing in the deviation ratio that main scanning direction produced, be big and cause projected length than the formed luminous point of scanning ray 113a at main scanning direction; This situation is also identical at sub scanning direction, departs from the formed luminous point of scanning ray of scanning ray 113a, also will be bigger; So the luminous point 2b, the 2c that image on the photosensitive drums 15 are similar ellipse, and the area of 2b, 2c is greater than 2a.Wherein, S _A0With S _B0Be the luminous point of scanning ray on mems mirror 10 reflectings surface length, G at main scanning direction (Y direction) and sub scanning direction (directions X) _aWith G _bFor the Gaussian beam (Gaussian Beams) of scanning ray is 13.5% to be in the beam radius of Y direction and directions X in light intensity, as shown in Figure 5, only shown the beam radius of Y direction among Fig. 5.

Vertical the above, the scanning ray that two-chip type f theta lens of the present utility model can be reflected mems mirror 10, with the scanning ray of Gaussian beam distort (distortion) revise, and the relation of time-angular velocity is changed into the relation of time-distance.Scanning ray is exaggerated through the f Theta lens at the light beam of main scanning direction (Y direction) with sub scanning direction (directions X), produces luminous point on imaging surface, so that the resolution that meets demand to be provided.

For reaching above-mentioned effect, the utility model two-chip type f theta lens 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 131b and second eyeglass 132, at main scanning direction or sub scanning direction, can use the design of sphere curved surface or non-spherical surface, if use the non-spherical surface design, its non-spherical surface satisfies following surface equation formula:

1: horizontal picture surface equation formula (Anamorphic equation)

$Z=\frac{\left(\mathrm{Cx}\right)X^2+\left(\mathrm{Cy}\right){\mathrm{<figure-callout\; id="2"\; label="Y"\; filenames="Y20082013885500261.png,Y20082013885500271.png"\; state="\{\{state\}\}">Y</figure-callout>}}^2}{1+\sqrt{1-(1+\mathrm{Kx}){\left(\mathrm{Cx}\right)}^2{X}^2-(1+\mathrm{Ky}){\left(\mathrm{Cy}\right)}^2{\mathrm{<figure-callout\; id="2"\; label="Y"\; filenames="Y20082013885500261.png,Y20082013885500271.png"\; state="\{\{state\}\}">Y</figure-callout>}}^2}}+A_R{[(1-A_p){\mathrm{<figure-callout\; id="2"\; label="X"\; filenames="Y20082013885500261.png,Y20082013885500271.png"\; state="\{\{state\}\}">X</figure-callout>}}^2+(1+A_P)Y^2]}^2+$

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

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

Wherein, Z be on the eyeglass any point with the distance (SAG) of optical axis direction to the initial point 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 (deformationfrom the conic) with ten powers four times, six times, for eight times of rotation symmetry (rotationallysymmetric 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-rotating symmetry (non-rotationallysymmetric components); Work as C _x=C _y, K _x=K _yAnd A _P=B _p=C _p=D _p, then be reduced to single aspheric surface at=0 o'clock.

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

$Z=\mathrm{Zy}+\frac{\left(\mathrm{Cxy}\right){\mathrm{<figure-callout\; id="2"\; label="X"\; filenames="Y20082013885500261.png,Y20082013885500271.png"\; state="\{\{state\}\}">X</figure-callout>}}^2}{1+\sqrt{1-{\left(\mathrm{Cxy}\right)}^2{\mathrm{<figure-callout\; id="2"\; label="X"\; filenames="Y20082013885500261.png,Y20082013885500271.png"\; state="\{\{state\}\}">X</figure-callout>}}^2}}$

$\mathrm{Cxy}=\frac{1}{(1/\mathrm{Cx})-\mathrm{Zy}}$

$\mathrm{Zy}=\frac{\left(\mathrm{Cy}\right){\mathrm{<figure-callout\; id="2"\; label="Y"\; filenames="Y20082013885500261.png,Y20082013885500271.png"\; state="\{\{state\}\}">Y</figure-callout>}}^2}{1+\sqrt{1-(1+\mathrm{Ky}){\left(\mathrm{Cy}\right)}^2{\mathrm{<figure-callout\; id="2"\; label="Y"\; filenames="Y20082013885500261.png,Y20082013885500271.png"\; state="\{\{state\}\}">Y</figure-callout>}}^2}}+B_4{\mathrm{<figure-callout\; id="4"\; label="Y"\; filenames="Y20082013885500261.png"\; state="\{\{state\}\}">Y</figure-callout>}}^4+B_6{\mathrm{<figure-callout\; id="6"\; label="Y"\; filenames="Y20082013885500261.png"\; state="\{\{state\}\}">Y</figure-callout>}}^6+B_8{Y}^8+B_{10}{Y}^{10}---\left(3\right)$

Wherein, Z be on the eyeglass any point with the distance (SAG) of optical axis direction to the initial point section; C _yWith C _yThe curvature (curvature) of difference Y direction and directions X; K _yCircular cone coefficient (Coniccoefficient) for the Y direction; B ₄, B ₆, B ₈With B ₁₀Be respectively the coefficient (4th～10thorder coefficients deformation from the conic) of four times, six times, eight times, ten times powers; Work as C _x=C _yAnd K _y=A _P=B _p=C _p=D _p, then be reduced to single sphere at=0 o'clock.

For making scanning ray sweep velocity such as keep on the imaging surface on the object, for example, in two identical time intervals, the spacing of keeping two luminous points equates; Two-chip type f theta lens of the present utility model can be with scanning ray 113a to the light 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 form on the photosensitive drums 15 of imaging equates.Further, after laser beam 111 is via mems mirror 10 reflections, its Gaussian beam radius G _aWith G _bBigger, if after the distance of this scanning ray through mems mirror 10 and photosensitive drums 15, Gaussian beam radius G _aWith G _bTo be bigger, do not meet practical resolution requirement; Two-chip type f theta lens of the present utility model further can form Ga and the less Gaussian beam of Gb to the light between the scanning ray 113b with the scanning ray 113a of mems mirror 10 reflection, makes the less luminous point of generation on the photosensitive drums 15 of the image formation by rays after the focusing; Moreover two-chip type f theta lens of the present utility model more can be with the luminous point size homogenising (being limited in the scope that meets resolution requirement) that is imaged on the photosensitive drums 15, to obtain best parsing effect.

Two-chip type f theta lens of the present utility model comprises, start in regular turn from mems mirror 10, be first eyeglass 131 and second eyeglass 132, to be lenticular eyeglass and second eyeglass 132 be the crescent and concave surface eyeglass in the mems mirror side with first eyeglass 131, wherein first eyeglass 131 has the first optical surface 131a and the second optical surface 131b, with the scanning ray luminous point of the angle of mems mirror 10 reflection and time nonlinear relationship convert to apart from the time be the scanning ray luminous point of linear relationship; Wherein second eyeglass 132 has the 3rd optical surface 132a and the 4th optical surface 132b, and the scanning ray correction of first eyeglass 131 is concentrated on the object; By of scanning ray in photosensitive drums 15 on the imaging of this two-chip type f theta lens with mems mirror 10 reflections; Wherein, the first optical surface 131a, the second optical surface 131b, the 3rd optical surface 132a and the 4th optical surface 132b have at least one to be optical surface that aspheric surface constituted at main scanning direction, and 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 optical surface that aspheric surface constituted or the optical surface that all uses sphere and constituted at sub scanning direction at sub scanning direction.Further, on first eyeglass 131 and second eyeglass 132 constitute, on optical effect, two-chip type f theta lens of the present utility model, further satisfy the condition of formula (4)～formula (5) at main scanning direction:

$0.1<\frac{{\mathrm{<figure-callout\; id="3"\; label="d"\; filenames="Y20082013885500261.png,Y20082013885500271.png"\; state="\{\{state\}\}">d</figure-callout>}}_3+{\mathrm{<figure-callout\; id="4"\; label="d"\; filenames="Y20082013885500261.png"\; state="\{\{state\}\}">d</figure-callout>}}_4+d_5}{f_{\left(1\right)Y}}<0.6---\left(4\right)$

$-0.4<\frac{d_5}{f_{\left(2\right)Y}}<-0.02---\left(5\right)$

Or, satisfy formula (6) at main scanning direction

$0.1<|f_{\mathrm{sY}}\&CenterDot;(\frac{(n_{d1}-1)}{f_{\left(1\right)y}}+\frac{(n_{d2}-1)}{f_{\left(2\right)y}})|<1.2---\left(6\right)$

And satisfy formula (7) at sub scanning direction

$0.086<|(\frac{1}{R_{1x}}-\frac{1}{R_{2x}})+(\frac{1}{R_{3x}}-\frac{1}{R_{4x}})f_{\mathrm{sX}}|<1.0---\left(7\right)$

Wherein, f _{(1) Y}Be focal length, the f of first eyeglass 131 at main scanning direction _{(2) Y}Be focal length, the d of second eyeglass 132 at main scanning direction ₃Distance, the d of first eyeglass, 131 object side optical surface to the second eyeglasses, 132 mems mirrors, 10 side optical surfaces during for θ=0 ° ₄Thickness, the d of second eyeglass 132 during for θ=0 ° ₅Second eyeglass, 132 object side optical surfaces are to the distance of object, f during for θ=0 ° _SxBe compound focal length (combination focal length), the f of two-chip type f theta lens at sub scanning direction _SYBe compound focal length, the R of two-chip type f theta lens at main scanning direction _IxThe i optical surface is in the radius-of-curvature of sub scanning direction; R _IyBe the radius-of-curvature of i optical surface at main scanning direction; n _D1With n _D2It is the refractive index (refraction index) of first eyeglass 131 and second eyeglass 132.

Moreover the formed luminous point homogeneity of two-chip type f theta lens of the present utility model can be represented with the maximal value of the beam size of scanning ray on photosensitive drums 15 and the ratio delta of minimum value, promptly satisfies formula (8):

$0.4<\mathrm{\&delta;}=\frac{\min (S_b\&CenterDot;S_a)}{\max (S_b\&CenterDot;S_a)}---\left(8\right)$

Further, the formed resolution of two-chip type f theta lens of the present utility model can be used η _MaxFor the luminous point of scanning ray on mems mirror 10 reflectings surface through the scanning peaked ratio of luminous point and η on photosensitive drums 15 _MinFor the luminous point of scanning ray on mems mirror 10 reflectings surface through the ratio of scanning luminous point minimum value on photosensitive drums 15 for expression, can satisfy formula (9) and formula (10),

${\mathrm{\&eta;}}_{\max }=\frac{\max (S_b\&CenterDot;S_a)}{({\mathrm{<figure-callout\; id="0"\; label="S\; b"\; filenames="Y20082013885500261.png"\; state="\{\{state\}\}">S</figure-callout>}}_b\&CenterDot;S_{a0})}<0.10---\left(9\right)$

${\mathrm{\&eta;}}_{\min }=\frac{\min (S_b\&CenterDot;S_a)}{({\mathrm{<figure-callout\; id="0"\; label="S\; b"\; filenames="Y20082013885500261.png"\; state="\{\{state\}\}">S</figure-callout>}}_b\&CenterDot;S_{a0})}<0.10---\left(10\right)$

Wherein, S _aWith S _bAny luminous point that forms for scanning ray on the photosensitive drums 15 is that ratio, the η of smallest spot and maximum luminous point is the ratio of luminous point on the luminous point of scanning ray on mems mirror 10 reflectings surface and the photosensitive drums 15 on the photosensitive drums 15 at length, the δ of Y direction and directions X; S _A0With S _B0Be the luminous point of scanning ray on mems mirror 10 reflectings surface length at main scanning direction and sub scanning direction.

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

The following embodiment that is disclosed of the utility model explains at the main composition assembly of the two-chip type f theta lens of the utility model MEMS laser scanning device, though therefore the following embodiment that is disclosed of the utility model is applied in the MEMS laser scanning device, but with regard to generally having MEMS laser scanning device, except the two-chip type f theta lens that the utility model disclosed, other structure still belongs to general technique known, therefore the personage who generally is familiar with this technology in the art understands, the constituent components of the two-chip type f theta lens of MEMS laser scanning device that the utility model discloses is not restricted to the following example structure that discloses, just each constituent components of the two-chip type f theta lens of this MEMS laser scanning device is to carry out many changes, revise, even the equivalence change, for example: the radius-of-curvature design of first eyeglass 131 and second eyeglass 132 or the design of face type, material is selected for use, spacing adjustment etc. does not limit.

＜the first embodiment 〉

First eyeglass 131 of the two-chip type f theta lens of present embodiment and one second eyeglass 132, wherein to be lenticular eyeglass, second eyeglass 132 be the crescent and concave surface eyeglass in the mems mirror side with first eyeglass 131, the 3rd optical surface 132a and the 4th optical surface 132b of the first optical surface 131a of first eyeglass 131 and the second optical surface 131b, second eyeglass 132 are aspheric surface, and use formula (2) is carried out the aspheric surface design.Its optical characteristics and aspheric surface parameter such as table one and table two.

The f θ optical characteristics of table one, first embodiment

^*The expression aspheric surface

The optical surface aspheric surface parameter of table two, first embodiment

Two-chip type f theta lens through being constituted thus, f _{(1) Y}=248.747, f _{(2) Y}=-256.151, f _SX=28.301, f _SY=3349.652 (mm), scanning ray can be converted to distance is the scanning ray luminous point of linear relationship with the time, and with luminous point S on the mems mirror 10 _A0=14.19 (μ m), S _B0=3109.99 (μ m) scanning becomes scanning ray, in photosensitive drums 15 enterprising line focusings, forms less luminous point 6, and satisfies the condition of formula (4)～formula (10), as table three; On the photosensitive drums 15 with the Gaussian beam diameter (μ m) of central shaft Z axle, as table four at the luminous point of Y direction distance center axle Y distance (mm); And the luminous point distribution plan of present embodiment as shown in Figure 7.

Table three, first embodiment table that satisfies condition

The maximal value of luminous point Gaussian beam diameter on table four, the first embodiment photosensitive drums

＜the second embodiment 〉

First eyeglass 131 of the two-chip type f theta lens of present embodiment and second eyeglass 132, wherein to be lenticular eyeglass, second eyeglass 132 be the crescent and concave surface eyeglass in the mems mirror side with first eyeglass 131, the 3rd optical surface 132a and the 4th optical surface 132b of the first optical surface 131a of first eyeglass 131 and the second optical surface 131b, second eyeglass 132 are aspheric surface, and use formula (2) is carried out the aspheric surface design.Its optical characteristics and aspheric surface parameter such as table five and table six.

The f θ optical characteristics of table five, second embodiment

^*The expression aspheric surface

The optical surface aspheric surface parameter of table six, second embodiment

Two-chip type f theta lens through being constituted thus, f _{(1) Y}=199.250, f _{(2) Y}=-207.231, f _SX=29.556, f _SY=1482.761 (mm), scanning ray can be converted to distance is the scanning ray luminous point of linear relationship with the time, and with luminous point S on the mems mirror 10 _A0=14.19 (μ m), S _B0=3109.99 (μ m) scanning becomes scanning ray, in photosensitive drums 15 enterprising line focusings, forms less luminous point 8, and satisfies the condition of (4)～formula (10), as table seven; On the photosensitive drums 15 with the Gaussian beam diameter (μ m) of central shaft Z axle, as table eight at the luminous point of Y direction distance center axle Y distance (mm); And the luminous point distribution plan of present embodiment as shown in Figure 8.

Table seven, second embodiment table that satisfies condition

The maximal value of luminous point Gaussian beam diameter on table eight, the second embodiment photosensitive drums

＜the three embodiment 〉

First eyeglass 131 of the two-chip type f theta lens of present embodiment and second eyeglass 132, wherein to be lenticular eyeglass, second eyeglass 132 be the crescent and concave surface eyeglass in the mems mirror side with first eyeglass 131, first optical surface 131a of first eyeglass 131 and the 4th optical surface 132b of second eyeglass 132 are aspheric surface, and use formula (3) is carried out the aspheric surface design; Second optical surface 131b of first eyeglass 131 and the 3rd optical surface 132a of second eyeglass 132 are aspheric surface, and use formula (2) is carried out the aspheric surface design.Its optical characteristics and aspheric surface parameter such as table nine and table ten.

The f θ optical characteristics of table nine, the 3rd embodiment

^*The expression aspheric surface

The optical surface aspheric surface parameter of table ten, the 3rd embodiment

Two-chip type f theta lens through being constituted thus, f _{(1) Y}=29.477, f _{(2) Y}=-197.425, f _SX=27.634, f _SY=-2795.472 (mm), scanning ray can be converted to distance is the scanning ray luminous point of linear relationship with the time, and with luminous point S on the mems mirror 10 _A0=14.19 (μ m), S _B0=3109.99 (μ m) scanning becomes scanning ray, in photosensitive drums 15 enterprising line focusings, forms less luminous point 10, and satisfies the condition of (4)～formula (10), as table ten one; On the photosensitive drums 15 with the Gaussian beam diameter (μ m) of central shaft Z axle, as table ten two at the luminous point of Y direction distance center axle Y distance (mm); The luminous point distribution plan of present embodiment as shown in Figure 9.

Table ten the one, the 3rd embodiment table that satisfies condition

The maximal value of luminous point Gaussian beam diameter on table ten the two, the 3rd embodiment photosensitive drums

＜the four embodiment 〉

First eyeglass 131 of the two-chip type f theta lens of present embodiment and second eyeglass 132, wherein to be lenticular eyeglass, second eyeglass 132 be the crescent and concave surface eyeglass in the mems mirror side with first eyeglass 131, the 3rd optical surface 132a and the 4th optical surface 132b of the first optical surface 131a of first eyeglass 131 and the second optical surface 131b, second eyeglass 132 are aspheric surface, and use formula (2) is carried out the aspheric surface design.Its optical characteristics and aspheric surface parameter such as table ten three and table ten four.

The f θ optical characteristics of table ten the three, the 4th embodiment

^*The expression aspheric surface

The optical surface aspheric surface parameter of table ten the four, the 4th embodiment

Two-chip type f theta lens through being constituted thus, f _{(1) Y}=190.790, f _{(2) Y}=-231.568, f _SX=28.33, f _SY=834.13 (mm), scanning ray can be converted to distance is the scanning ray luminous point of linear relationship with the time, and with luminous point S on the mems mirror 10 _A0=14.19 (μ m), S _B0=3109.99 (μ m) scanning becomes scanning ray, in photosensitive drums 15 enterprising line focusings, forms less luminous point 12, and satisfies the condition of formula (4)～formula (10), as table ten five; On the photosensitive drums 15 with the Gaussian beam diameter (μ m) of central shaft Z axle, as table ten six at the luminous point of Y direction distance center axle Y distance (mm); And the luminous point distribution plan of present embodiment as shown in figure 10.

Table ten the five, the 4th embodiment table that satisfies condition

The maximal value of luminous point Gaussian beam diameter on table ten the six, the 4th embodiment photosensitive drums

＜the five embodiment 〉

First eyeglass 131 of the two-chip type f theta lens of present embodiment and second eyeglass 132, wherein to be lenticular eyeglass, second eyeglass 132 be the crescent and concave surface eyeglass in the mems mirror side with first eyeglass 131, the 3rd optical surface 132a and the 4th optical surface 132b of the first optical surface 131a of first eyeglass 131 and the second optical surface 131b, second eyeglass 132 are aspheric surface, and use formula (2) is carried out the aspheric surface design.Its optical characteristics and aspheric surface parameter such as table ten seven and table ten eight.

The f θ optical characteristics of table ten the seven, the 5th embodiment

^*The expression aspheric surface

The optical surface aspheric surface parameter of table ten the eight, the 5th embodiment

Two-chip type f theta lens through being constituted thus, f _{(1) Y}=115.57, f _{(2) Y}=-1099.047, f _SX=21.265, f _SY=128.663 (mm), scanning ray can be converted to distance is the scanning ray luminous point of linear relationship with the time, and with luminous point S on the mems mirror 10 _A0=14.19 (μ m), S _B0=3109.99 (μ m) scanning becomes scanning ray, in photosensitive drums 15 enterprising line focusings, forms less luminous point 12, and satisfies the condition of formula (4)～formula (10), as table ten nine; On the photosensitive drums 15 with the Gaussian beam diameter (μ m) of central shaft Z axle, as table two ten at the luminous point of Y direction distance center axle Y distance (mm); And the luminous point distribution plan of present embodiment as shown in figure 11.

Table ten the nine, the 5th embodiment table that satisfies condition

The maximal value of luminous point Gaussian beam diameter on table two the ten, the 5th embodiment photosensitive drums

By the above embodiments explanation, the utility model can reach following effect at least:

(1) setting by two-chip type f theta lens of the present utility model, the speed scanning phenomenon such as non-that the mems mirror that carries out simple harmonic motion can be successively decreased by increasing in time originally or increases progressively at imaging surface glazing dot spacing, 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 luminous point spacings that form on the object and equate.

(2) by the setting of two-chip type f theta lens of the present utility model, can distort and revise scanning ray at main scanning direction and sub scanning direction, the luminous point on the object that focuses on imaging is dwindled.

(3) by the setting of two-chip type f theta lens of the present utility model, can distort and revise scanning ray at main scanning direction and sub scanning direction, make the luminous point size homogenising that is imaged on the object.

The above only is a preferred embodiment of the present utility model, only is illustrative for the utility model, and nonrestrictive; Those skilled in the art should be appreciated that in the spirit and scope that the utility model claim is limited can carry out many changes to it, revise, even the equivalence change, but all will fall in the protection domain of the present utility model.

Claims (5)

1. A two-piece fθ lens for a MEMS laser scanning device, the two-piece fθ lens is suitable for a MEMS laser scanning device, and the MEMS laser scanning device includes at least one light source for emitting a light beam, which swings left and right with resonance Reflecting the light beam emitted by the light source into a micro-electromechanical mirror for scanning light, and a photosensitive target, it is characterized in that the two-piece fθ mirror includes, counting from the micro-electromechanical mirror in sequence, the first biconvex A lens and a crescent-shaped second lens with a concave surface on the micro-electromechanical mirror side, wherein the first lens has a first optical surface and a second optical surface, and the first optical surface and the second optical surface are in the main scanning direction At least one optical surface is an aspheric surface, so as to convert the scanning light spot whose angle and time reflected by the micro-electromechanical mirror have a nonlinear relationship into a scanning light spot whose distance and time are linear; wherein the second The lens has a third optical surface and a fourth optical surface, and at least one optical surface of the third optical surface and the fourth optical surface is an aspherical surface in the main scanning direction, so as to correct and condense the scanning light of the first lens On the target object; the scanning light reflected by the micro-electromechanical mirror is imaged on the target object through the two fθ mirrors. 2. The two-piece fθ lens of the MEMS laser scanning device according to claim 1, wherein the following conditions are further satisfied in the main scanning direction: $\mathrm{<span\; class="notranslate">\; 0.1</span>}<span\; class="notranslate">\; <</span>\frac{{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 5</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; Y</span>}}}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 0.6</span>}$ $<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; .</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; <</span>\frac{{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 5</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; Y</span>}}}<span\; class="notranslate">\; <</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; .</span>\mathrm{<span\; class="notranslate">\; 02</span>}<span\; class="notranslate">\; ;</span>$ Wherein, f _(1)Y is the focal length of the first mirror in the main scanning direction, f _(2)Y is the focal length of the second mirror in the main scanning direction, and _d3 is the focal length of the first lens when θ=0°. The distance from the optical surface on the target object side of the lens to the optical surface on the MEMS mirror side of the second lens, _d4 is the thickness of the second lens when θ=0°, and _d5 is the second lens when θ=0° The distance from the optical surface on the target side to the target. 3. The two-piece fθ lens of the MEMS laser scanning device according to claim 1, wherein the following conditions are further satisfied: in the main scanning direction to meet the $\mathrm{<span\; class="notranslate">\; 0.1</span>}<span\; class="notranslate">\; <</span><span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; s\; Y</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\frac{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}}}<span\; class="notranslate">\; +</span>\frac{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span><span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 1.2</span>}$ Satisfied in the sub-scanning direction $\mathrm{<span\; class="notranslate">\; 0.086</span>}<span\; class="notranslate">\; <</span><span\; class="notranslate">\; |</span><span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}\mathrm{<span\; class="notranslate">\; x</span>}}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; x</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}\mathrm{<span\; class="notranslate">\; x</span>}}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}\mathrm{<span\; class="notranslate">\; x</span>}}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; sX</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 1.0</span>}<span\; class="notranslate">\; ;</span>$ Wherein, f _(1)Y and f _(2)Y are the focal lengths of the first mirror and the second mirror in the main scanning direction, f _sx is the composite focal length of the two-piece fθ mirror in the sub-scanning direction, f _sY is the composite focal length of the two-piece fθ lens in the main scanning direction, R _ix is the curvature radius of the i-th optical surface in the sub-scanning direction; n _d1 and n _d2 are the refractive indices of the first lens and the second lens, respectively . 4. The two-piece fθ lens of the MEMS laser scanning device according to claim 1, wherein the ratio of the size of the smallest light spot to the largest light spot formed on the target satisfies: $\mathrm{<span\; class="notranslate">\; 0.4</span>}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; \&delta;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; min</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; max</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; )</span>}$ Wherein, S _a and S _b are the lengths of any light spot formed by the scanning light on the target object in the main scanning direction and the sub-scanning direction, and δ is the minimum light spot and the maximum light spot on the target object. point ratio. 5. The two-piece fθ lens of the MEMS laser scanning device according to claim 1, characterized in that the ratio of the maximum light spot formed on the target object to the minimum light spot formed on the target object The ratio of points satisfies respectively: ${\mathrm{<span\; class="notranslate">\; \&eta;</span>}}_{\mathrm{<span\; class="notranslate">\; max</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; max</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; )</span>}{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 0.10</span>}$ ${\mathrm{<span\; class="notranslate">\; \&eta;</span>}}_{\mathrm{<span\; class="notranslate">\; min</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; min</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; )</span>}{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 0.10</span>}<span\; class="notranslate">\; ;</span>$ Wherein, S _a0 and S _b0 are the lengths of the light spot of the scanning light on the reflection surface of the micro-electromechanical mirror in the main scanning direction and the sub-scanning direction, and S _a and S _b are any light spot formed by the scanning light The length in the main scanning direction and the sub-scanning direction, η _max is the ratio of the maximum light spot formed on the target by scanning the light spot of the scanning light on the reflecting surface of the micro-electromechanical mirror, and η _min is The ratio of the smallest light spot formed on the object by scanning the light spot of the scanning light on the reflection surface of the micro-electromechanical mirror.

Images