CN201293873Y - Two-piece type f theta lens of micro-electromechanical laser scanning device - Google Patents

Abstract

A two-piece f theta lens of micro-electromechanical laser scanning device is prepared as setting the first lens to be a biconvex lens and the second lens to be a biconcave lens, forming the first lens to be two optical surfaces, forming at least one optical surface to be aspheric surface in main scanning direction, forming the second lens to be two optical surfaces, forming at least one optical surface to be aspheric surface in main scanning direction, converting scanning light spot whose angle and time are non-linear relation reflected by micro-electromechanical reflector to scanning light spot whose distance and time are linear relation and correcting light spot on object, setting the first lens and the second lens to meet specific optical condition for achieving linear scanning effect and high resolution scanning purpose.

Description

Two-piece fθ mirror of MEMS laser scanning device

technical field

The utility model relates to a two-piece fθ lens of a micro-electromechanical laser scanning device, in particular to a micro-electromechanical reflector used to correct a simple harmonic motion to produce a sinusoidal angle change with time to realize laser scanning. The two-piece fθ mirror for the linear scanning effect required by the scanning device.

Background technique

At present, the laser scanning device LSU (Laser Scanning Unit) used in the laser beam printer LBP (Laser Beam Print) uses a high-speed rotating polygon mirror to control the scanning action of the laser beam (laser beam scanning). US7079171, US6377293, US6295116, or as described in Taiwan Patent I198966. The principle is briefly described as follows: use a semiconductor laser to emit a laser beam, first pass through a collimator, and then pass through an aperture to form a parallel beam, and the parallel beam passes through a cylindrical mirror ( After the cylindrical lens), the width on the Y-axis in the sub-scanning direction (sub scanning direction) can be parallelly focused along the parallel direction of the X-axis in the main scanning direction (mainscanning direction) to form a line image (line image), and then projected On a high-speed rotating polygonal mirror, the polygonal mirror is evenly and continuously provided with multiple mirrors, which are just at or close to the focus position of the above-mentioned line image. The projection direction of the laser beam is controlled by the polygon mirror. When a plurality of continuous mirrors rotate at high speed, the laser beam incident on a mirror can be directed at the same rotational angular velocity (angular) along the parallel direction of the main scanning direction (X axis). velocity) is deflected to a fθ linear scanning lens, and the fθ linear scanning lens is arranged beside the polygon mirror, which can be a single-element scanning lens or a two-element lens structure. The function of this fθ linear scanning lens is to focus the laser beam that is reflected by the reflector on the polygon mirror and enter the fθ lens into an elliptical light spot and project it on a photoreceptor drum (i.e. imaging surface), and Achieving linear scanning (scanning linearity) requirements. However, the prior art laser scanning device LSU has the following problems in use:

(1) The production of the rotating polygonal mirror is difficult and expensive, which relatively increases the production cost of the LSU.

(2) The polygon mirror must have the function of high-speed rotation (such as 40,000 rpm), and the precision requirement is high, so that the Y-axis width of the mirror surface of the reflection surface on the general polygon mirror is extremely thin, so that an additional LSU is required in the prior art. A cylindrical lens enables the laser beam to be focused into a line (a point on the Y axis) through the cylindrical lens and then projected on the reflector of the polygonal mirror, which increases the cost of components and the assembly process.

(3) The polygon mirrors in the prior art must rotate at high speed (such as 40,000 r/min), which increases the rotation noise relatively, and it takes a long time for the polygon mirror to start to work, which increases the waiting time after starting up.

(4) In the assembly structure of the LSU in the prior art, the central axis of the laser beam projected onto the polygon mirror is not directly facing the central axis of rotation of the polygon mirror, so that when designing the matching fθ lens, it is necessary to consider the separation of the polygon mirror at the same time. The problem of off axis deviation relatively increases the trouble in the design and production of fθ lenses.

In recent years, in order to improve the problems of the LSU assembly structure in the prior art, an oscillating MEMS mirror (MEMS mirror) has been developed on the market to replace the polygonal mirror in the prior art to control the laser beam. scanning. Micro-electromechanical mirrors are torque oscillators (torsion oscillators), with a reflective layer attached to the surface, which can oscillate and swing the reflective layer to reflect light and scan. It will be used in imaging systems, scanners ( scanner) or laser printer (laser printer) laser scanning unit (laser scanning unit, referred to as LSU), its scanning efficiency (Scanningefficiency) will be higher than the traditional rotating polygonal mirror. Such as U.S. Patent No. 6,844,951, U.S. Pat. No. 6,956,597 (generating at least one driving signal, its driving frequency approaches the resonant frequency of a plurality of MEMS mirrors, and drives the MEMS mirrors with a driving signal to generate a scanning path), US7 ,064,876, US7,184,187, US7,190,499, US2006/0113393; or as Taiwan patent TW M253133, between the collimating mirror and the fθ mirror in an LSU module structure, a micro-electromechanical mirror is used to replace the rotating type of the prior art Polygonal mirror, thereby controlling the projection direction of the laser beam; or such as Japanese patent JP2006-201350, etc. The micro-electromechanical mirror has the advantages of small components, fast rotation speed and low manufacturing cost. However, because the micro-electromechanical mirror will perform a simple harmonic motion (harmonic motion) after receiving a voltage drive, and the mode of this simple harmonic motion is that time and angular velocity have a sinusoidal relationship, and projected on the micro-electromechanical mirror, it is reflected The relationship between the reflection angle θ and time t is:

θ(t) = θ _s sin(2π f t) (1)

Among them: f is the scanning frequency of the MEMS mirror; θ _s is the maximum unilateral scanning angle of the laser beam after passing through the MEMS mirror.

Therefore, at the same time interval Δt, the corresponding reflection angle system changes sinusoidally with time, that is, at the same time interval Δt, the reflection angle changes as: Δθ(t)=θ _s (sin( 2π·f·t ₁ )-sin(2π·f·t ₂ )), and has a nonlinear relationship with time, that is, when the reflected light is projected on the target at different angles, it will be generated within the same time interval The spot distance intervals are not uniform and may increase or decrease over time.

For example, when the swing angle of the micro-electromechanical mirror is at the peak and trough of the sine wave, the angle change will increase or decrease with time, which is different from the polygonal mirror in the prior art that rotates at a constant angular velocity. The laser scanning unit (LSU) of the micro-electromechanical mirror uses the fθ lens of the prior art, which will not be able to correct the angular variation produced by the micro-electromechanical mirror, resulting in non-equal-speed scanning of the laser beam projected on the imaging surface However, an imaging deviation on the imaging plane occurs. Therefore, the laser scanning device composed of micro-electro-mechanical mirrors is referred to as micro-electro-mechanical laser scanning device (MEMS LSU). Therefore, it will be urgently needed to develop fθ mirrors that can be used in MEMS laser scanning devices to modify the scanning light so that images can be correctly imaged on the target.

Utility model content

The purpose of the utility model is to provide a two-piece fθ lens of a micro-electromechanical laser scanning device. The two-piece fθ lens is counted sequentially from the micro-electromechanical reflector, and consists of a double-convex first lens and a double-concave first lens. Composed of two mirrors, the scanning light reflected by the micro-electromechanical mirror can be correctly imaged on the target object, so as to realize the linear scanning effect required by the laser scanning device.

Another object of the present invention is to provide a two-piece fθ mirror of a micro-electromechanical laser scanning device, which is used to reduce the area of the spot projected on the target object, thereby achieving the effect of improving resolution.

Another object of the present utility model is to provide a two-piece fθ lens of a micro-electromechanical laser scanning device, which can correct the distortion due to the deviation of the scanning light from the optical axis, resulting in an increase in the offset in the main scanning direction and the sub-scanning direction, so that the imaging The light spot of the photosensitive drum is deformed into an elliptical shape, and the size of each imaging light spot can be uniformed, thereby achieving the effect of improving the resolution quality.

Therefore, the two-piece fθ mirror of the micro-electromechanical laser scanning device of the present utility model is suitable for at least one micro-electromechanical reflector that will reflect the laser beam emitted by the light source into scanning light by resonating left and right swings of the light source emitting the laser beam, so as to Imaging on the target object; for laser printers, the target object is often a photosensitive drum (drum), that is, the light spot to be imaged emits a laser beam through the light source, scans left and right through the MEMS mirror, and the MEMS mirror reflects the laser light The beam forms scanning light, and the scanning light passes through the two-piece fθ lens of the utility model to correct the angle and position, and then forms a spot on the photosensitive drum. Since the photosensitive drum is coated with a photosensitizer, it can sense the carbon powder and make it gather on the on paper so that the data can be printed out.

The two-piece fθ lens of the present utility model includes a first lens and a second lens sequentially counted from the micro-electromechanical reflector, wherein the first lens has a first optical surface and a second optical surface, and the first optical surface At least one optical surface in the main scanning direction with the second optical surface is composed of an aspheric surface, and the micro-electromechanical mirror mainly exhibits simple harmonic motion. The equal-rate scanning phenomenon is corrected to equal-rate scanning, so that the projection of the laser beam on the imaging surface is scanned at an equal rate. The second lens has a third optical surface and a fourth optical surface. At least one optical surface of the third optical surface and the fourth optical surface in the main scanning direction is composed of an aspheric surface, which is mainly used to homogenize the scanning light in the main scanning direction. Direction and sub-scanning direction cause imaging deviation on the photosensitive drum due to the deviation of the optical axis, and correct the scanning light of the first lens to focus on the target object.

The utility model can at least achieve the following effects:

(1) By the setting of the two-piece type fθ mirror of the present utility model, the micro-electro-mechanical reflector that is simple harmonic motion can be changed from the non-equal rate scanning phenomenon that decreases or increases progressively with time on the imaging surface, It is corrected to scan at a constant rate, so that the projection of the laser beam on the imaging surface is scanned at a constant rate, so that the distance between two adjacent light spots formed on the target object is equal.

(2) Through the arrangement of the two-piece fθ lens of the present invention, distortion correction can be performed on the scanning light in the main scanning direction and the sub-scanning direction, so that the light spot focused on the imaging target can be reduced.

(3) Through the arrangement of the two-piece fθ lens of the present invention, the distortion correction can be performed on the scanning light in the main scanning direction and the sub-scanning direction, so that the size of the light spot imaged on the target object can be uniformed.

Description of drawings

Fig. 1 is the schematic diagram of the optical path of the two-piece fθ eyeglass of the present utility model;

Fig. 2 is a relation diagram of scanning angle θ and time t of a microelectromechanical mirror;

Fig. 3 is an optical path diagram and a symbol explanatory diagram of the scanning light passing through the first lens and the second lens;

Fig. 4 is a schematic diagram of the change of the area of the light spot with the different projection positions after the scanning light is projected on the photosensitive drum;

Fig. 5 is a relationship diagram between the Gaussian distribution of the light beam and the light intensity;

Fig. 6 is an optical path diagram of an embodiment of the scanning light passing through the first lens and the second lens of the present utility model;

Fig. 7 is a schematic diagram of light spots of the first embodiment;

Fig. 8 is a schematic diagram of light spots of the second embodiment;

Fig. 9 is a schematic diagram of light spots of the third embodiment; and

Fig. 10 is a schematic diagram of light spots of the fourth embodiment.

Description of main component symbols:

10: MEMS mirror;

11: Laser light source;

111: light beam;

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

131: first lens;

132: second lens;

14a, 14b: photoelectric sensors;

15: photosensitive drum;

16: Cylindrical mirror;

2, 2a, 2b, 2c: light spots; and

3: Effective scanning window

Detailed ways

Referring to FIG. 1 , FIG. 1 is a schematic diagram of the optical path of the two-piece fθ lens of the MEMS laser scanning device of the present invention. The two-piece fθ lens of the MEMS laser scanning device of the present utility model includes a first lens 131 with a first optical surface 131a and a second optical surface 131b, and a second lens with a third optical surface 132a and a fourth optical surface 132b. The lens 132 is suitable for a MEMS laser scanning device. In the figure, the MEMS laser scanning device mainly includes a laser light source 11, a MEMS mirror 10, a cylindrical mirror 16, two photoelectric sensors 14a, 14b, and a photosensitive target. In the figure, the object is implemented using a photosensitive drum (drum) 15 . The light beam 111 generated by the laser light source 11 passes through the cylindrical mirror 16 and is projected onto the MEMS mirror 10 . The MEMS mirror 10 reflects the light beam 111 into scanning light rays 113 a , 113 b , 113 c , 114 a , 114 b , 115 a , and 115 b in a left-right resonant manner. Wherein the projection of the scanning rays 113a, 113b, 113c, 114a, 114b, 115a, 115b in the X direction is called the sub scanning direction (sub scanning direction), and the projection in the Y direction is called the main scanning direction (main scanning direction), And the scanning angle of the MEMS mirror 10 is θc.

Referring to FIG. 1 and FIG. 2 , FIG. 2 is a graph showing the relation between scanning angle θ and time t of the MEMS mirror. Since the micro-electromechanical mirror 10 is in simple harmonic motion, its motion angle changes sinusoidally with time, so the outgoing angle of the scanning light has a nonlinear relationship with time. As shown in the illustration, the wave peaks a-a' and wave troughs bb', their swing angles are obviously smaller than the wave bands a-b and a'-b', and this phenomenon of uneven angular velocity is likely to cause imaging deviation of the scanning light on the photosensitive drum 15 . Therefore, the photoelectric sensors 14a, 14b are arranged within ±θc of the maximum scanning angle of the microelectromechanical mirror 10, and the included angle is ±θp, and the laser beam is reflected by the microelectromechanical mirror 10 from the peak of FIG. In the scanning light 115a of Fig. 1; when the photoelectric sensor 14a detects the scanning beam, it means that the MEMS mirror 10 swings to +θp angle, which is equivalent to the scanning light 114a of Fig. 1; when the MEMS mirror 10 scans When the angle changes as point a in Figure 2, it is equivalent to the position of scanning light 113b; at this time, the laser light source 11 will be driven to emit laser beam 111, and when scanning to point b in Figure 2, it is equivalent to scanning light 113c position (equivalent to the laser beam 111 emitted by the laser light source 11 within the angle of ±θn); when the micro-electromechanical mirror 10 produces reverse vibration, such as being driven by the laser light source 11 in the band a'-b', it starts to emit Laser beam 111; thus completing one cycle.

Referring to FIG. 1 and FIG. 3 , FIG. 3 is an optical path diagram of the scanning light passing through the first lens and the second lens. Among them, ±θn is the effective scanning angle. When the rotation angle of the MEMS mirror 10 enters ±θn, the laser light source 11 starts to emit the laser beam 111, which is reflected by the MEMS mirror 10 as scanning light. When the scanning light passes through the first lens 131 is refracted by the first optical surface 131a and the second optical surface 131b of the first mirror 131, and the scanning light reflected by the micro-electromechanical mirror 10, which has a nonlinear relationship between the distance and time, is converted into a scanning light with a linear relationship between distance and time. light. When the scanning light passes through the first lens 131 and the second lens 132, the scanning light is focused on the photosensitive drum through the optical properties of the first optical surface 131a, the second optical surface 131b, the third optical surface 132a, and the fourth optical surface 132b. 15, and form a column of light spots (Spot) 2 on the photosensitive drum 15. On the photosensitive drum 15 , the distance between the two furthest light spots 2 is called the effective scanning window 3 . Wherein, _d1 is the distance between the MEMS mirror 10 and the first optical surface 131a, _d2 is the distance between the first optical surface 131a and the second optical surface 131b, _d3 is the distance between the second optical surface 131b and the third optical surface 132a _d4 is the distance from the third optical surface 132a to the fourth optical surface 132b, _d5 is the distance from the fourth optical surface 132b to the photosensitive drum 15, _R1 is the radius of curvature (Curvature) of the first optical surface 131a, R ₂ is the radius of curvature of the second optical surface 131b, R ₃ is the radius of curvature of the third optical surface 132a, and R ₄ is the radius of curvature of the fourth optical surface 132b.

Referring to FIG. 4 , FIG. 4 is a schematic diagram showing how the spot area changes with different projection positions after the scanning light is projected on the photosensitive drum. When the scanning light 113a passes through the first lens 131 and the second lens 132 along the optical axis direction and then projects on the photosensitive drum 15, because the angle incident on the first lens 131 and the second lens 132 is zero, so in the main scanning direction The resulting deflection rate is zero, so the light spot 2a imaged on the photosensitive drum 15 is a kind of circle. When the scanning light rays 113b and 113c pass through the first lens 131 and the second lens 132 and then project on the photosensitive drum 15, because the angle formed between the first lens 131 and the second lens 132 and the optical axis is not zero, Therefore, the offset rate generated in the main scanning direction is not zero, and the projection length in the main scanning direction is larger than the light spot formed by the scanning light 113a; this situation is also the same in the sub-scanning direction, which deviates from the scanning of the scanning light 113a The light spots formed by the light rays will also be relatively large; therefore, the light spots 2b, 2c imaged on the photosensitive drum 15 are a type of ellipse, and the areas of 2b, 2c are larger than 2a. Among them, 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 10 in the main scanning direction (Y direction) and the sub-scanning direction (X direction), and G _a and G _b are the Gaussian values of the scanning light. Gaussian beams (Gaussian beams) are beam radii in the Y direction and X direction when the light intensity is 13.5%, as shown in FIG. 5 , and only the description of the beam radius in the Y direction is shown in FIG. 5 .

In summary, the two-piece fθ mirror of the present utility model can correct the scanning light reflected by the MEMS mirror 10, that is, the scanning light of the Gaussian beam, and convert the time-angular velocity relationship into Time-distance relationship. The light beams of the scanning light in the main scanning direction (Y direction) and the sub scanning direction (X direction) are amplified to generate light spots on the imaging surface to provide a required resolution.

In order to achieve the above-mentioned effect, the second optical surface 131a or the second optical surface 132a of the first optical surface 131 and the third optical surface 132a or the fourth optical surface 132b of the second optical surface 132 of the two-piece type fθ eyeglass of the present utility model, on the The main scanning direction or sub-scanning direction can be designed with a spherical surface or an aspheric surface. If an aspheric surface is used for design, the aspheric surface is the following surface equation:

1: Anamorphic equation

$\mathrm{<span\; class="notranslate">\; Z</span>}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; Cx</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; Cy</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="Y"\; filenames="Y20082020788700231.png,Y20082020788700241.png"\; state="\{\{state\}\}">Y</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\sqrt{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; Cx</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; Ky</span>}<span\; class="notranslate">\; )</span>{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; Cy</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="Y"\; filenames="Y20082020788700231.png,Y20082020788700241.png"\; state="\{\{state\}\}">Y</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; R</span>}}{<span\; class="notranslate">\; [</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; Y</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ]</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>$

${\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; R</span>}}{<span\; class="notranslate">\; [</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; Y</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ]</span>}^{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; R</span>}}{<span\; class="notranslate">\; [</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; Y</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ]</span>}^{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>$

${\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; R</span>}}{<span\; class="notranslate">\; [</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; Y</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ]</span>}^{\mathrm{<span\; class="notranslate">\; 5</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Among them, Z is the distance from any point on the lens to the tangent plane of the origin in the direction of the optical axis (SAG); C _x and _Cy are the curvatures in the X direction and Y direction respectively; K _x and _Ky are the X direction and Y direction respectively The conic coefficient of the direction; A _R , B _R , C _R and _DR are the four, six, eight and ten power conic deformation coefficients (deformation from the conic) of the rotationally symmetrical portion, respectively ; A _P , B _P , C _P and D _P are respectively the deformation foom the conic of the fourth, sixth, eighth and tenth powers of the non-rotationallysymmetric components; when C _x =C _y , K _x =K _y and A _P =B _p =C _p =D _p =0, simplifying to a single aspherical surface.

2: Toric equation

$\mathrm{<span\; class="notranslate">\; Z</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; Zy</span>}<span\; class="notranslate">\; +</span>\frac{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; Cxy</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\sqrt{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; Cxy</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}$

$\mathrm{<span\; class="notranslate">\; Cxy</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; Cx</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; Zy</span>}}$

$\mathrm{<span\; class="notranslate">\; Zy</span>}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; Cy</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="Y"\; filenames="Y20082020788700231.png,Y20082020788700241.png"\; state="\{\{state\}\}">Y</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\sqrt{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; Ky</span>}<span\; class="notranslate">\; )</span>{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; Cy</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="Y"\; filenames="Y20082020788700231.png,Y20082020788700241.png"\; state="\{\{state\}\}">Y</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="4"\; label="Y"\; filenames="Y20082020788700231.png"\; state="\{\{state\}\}">Y</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; 6</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="6"\; label="Y"\; filenames="Y20082020788700231.png"\; state="\{\{state\}\}">Y</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 6</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; 8</span>}}{\mathrm{<span\; class="notranslate">\; Y</span>}}^{\mathrm{<span\; class="notranslate">\; 8</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; 10</span>}}{\mathrm{<span\; class="notranslate">\; Y</span>}}^{\mathrm{<span\; class="notranslate">\; 10</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

Among them, Z is the distance (SAG) from any point on the lens to the origin tangent plane from the optical axis direction; C _y and C _x are the curvatures (curvature) in the Y direction and X direction respectively; _Ky is the conic coefficient in the Y direction (Coniccoefficient); B ₄ , B ₆ , B ₈ and B ₁₀ are conic deformation coefficients (4th to 10th order coefficients) (deformation from the conic) of the 4th, 6th, 8th, and 10th powers; when C _x = Cy _and K When _y =A _P =B _p =C _p =D _p =0, it is simplified to a single spherical surface.

In order to enable the scanning light to maintain equal scanning speeds on the imaging surface of the target object, for example, in two identical time intervals, the spacing between the two light spots is maintained to be equal; the two-piece fθ lens of the present invention can The light between the scanning light 113a and the scanning light 113b passes through the first lens 131 and the second lens 132 to correct the outgoing angle of the scanning light, so that the two scanning light at the same time interval, after the correction of the outgoing angle, will be displayed on the photosensitive image of the image. The distances between the two light spots formed on the drum 15 are equal. Furthermore, when the laser beam 111 is reflected by the MEMS reflector 10, its Gaussian beam radius Ga and Gb are larger, if the scanning light passes through the distance between the MEMS reflector 10 and the photosensitive drum 15, the Gaussian beam radius Ga and Gb will be larger, which does not meet the practical resolution requirements; the two-piece fθ mirror of the present invention can further form the light between the scanning light 113a and the scanning light 113b reflected by the micro-electromechanical mirror 10 to form a Gaussian beam with smaller Ga and Gb , then focus and produce smaller light spots on the photosensitive drum 15 of imaging; moreover, the two-piece type fθ lens of the present utility model can be imaged on the light spot size homogenization (limited to a photosensitive drum 15) on the photosensitive drum 15 within the range that meets the resolution requirements), in order to obtain the best resolution effect.

The two-piece fθ mirror of the present utility model comprises, counting from the micro-electromechanical reflector 10 in sequence, it is a first mirror 131 and a second mirror 132, both of which are made of biconvex mirrors, wherein the first mirror 131 has a first The optical surface 131a and the second optical surface 131b convert the scanning light spots whose angle and time reflected by the micro-electromechanical mirror 10 have a nonlinear relationship to the scanning light spots whose distance and time are linear; wherein, the second lens 132 With the third optical surface 132a and the fourth optical surface 132b, the scanning light of the first mirror 131 is corrected and focused on the target object; the scanning light reflected by the micro-electromechanical mirror 10 is sent to the photosensitive drum 15 through the two-piece fθ mirror Upper imaging; Wherein, the first optical surface 131a, the second optical surface 131b, the third optical surface 132a and the fourth optical surface 132b have at least one optical surface formed of an aspheric surface in the main scanning direction, the first optical surface 131a, The second optical surface 131b, the third optical surface 132a, and the fourth optical surface 132b may have at least one optical surface composed of an aspheric surface in the sub-scanning direction or all optical surfaces composed of spherical surfaces in the sub-scanning direction. Furthermore, in terms of the composition of the first lens 131 and the second lens 132, and in terms of optical effects, the two-piece fθ lens of the present invention further satisfies the conditions of formulas (4) to (5) in the main scanning direction:

$\mathrm{<span\; class="notranslate">\; 1.6</span>}<span\; class="notranslate">\; <</span>\frac{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="3"\; label="d"\; filenames="Y20082020788700231.png,Y20082020788700241.png"\; state="\{\{state\}\}">d</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="4"\; label="d"\; filenames="Y20082020788700231.png"\; state="\{\{state\}\}">d</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 5</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; Y</span>}}}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 2.5</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

$<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.2</span>}<span\; class="notranslate">\; <</span>\frac{{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 5</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; Y</span>}}}<span\; class="notranslate">\; <</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1.0</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

Or satisfy formula (6) in the main scanning direction

$\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; .</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; <</span><span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; s\; Y</span>}}<span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; (</span>\frac{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}}}<span\; class="notranslate">\; +</span>\frac{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span><span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 0.4</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

And satisfy formula (7) in the sub-scanning direction

$\mathrm{<span\; class="notranslate">\; 0.8</span>}<span\; class="notranslate">\; <</span><span\; class="notranslate">\; |</span><span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}\mathrm{<span\; class="notranslate">\; x</span>}}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; x</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}\mathrm{<span\; class="notranslate">\; x</span>}}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}\mathrm{<span\; class="notranslate">\; x</span>}}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; sX</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 1.6</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

Wherein, f _(1)Y is the focal length of the first mirror 131 in the main scanning direction, f _(2)Y is the focal length of the second mirror 132 in the main scanning direction, d ₃ is the first mirror 131 target object when θ=0° The distance from the side optical surface to the side optical surface of the second mirror 132 MEMS reflector 10, d ₄ is the thickness of the second mirror 132 when θ=0°, d ₅ is the second mirror 132 target object side optical surface when θ=0° The distance to the target, f _sx is the composite focal length of the two-piece fθ lens in the sub-scanning direction, f _s Y is the composite focal length of the two-piece fθ lens in the main scanning direction, R _ix is the i-th optical The radius of curvature of the _surface in the _sub -scanning direction; R _iy is the radius of curvature of the i-th optical surface in the main scanning direction;

Furthermore, the uniformity of the light spot formed by the two-piece type fθ lens of the present invention can be expressed by the ratio δ of the maximum value and the minimum value of the beam size of the scanning light on the photosensitive drum 15, which satisfies the formula (8):

$\mathrm{<span\; class="notranslate">\; 0.8</span>}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; \&delta;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; min</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; max</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

Furthermore, the resolution formed by the two-piece type fθ eyeglasses of the present utility model can use η _max to be the ratio of the maximum value of the light spot on the photosensitive drum 15 through scanning the light spot of the scanning light on the microelectromechanical reflector 10 reflective surface and η _min is represented by the ratio of the light point of scanning light on the photosensitive drum 15 for the light spot of scanning light on the microelectromechanical reflector 10 reflection surface, and can satisfy formula (9) and (10),

${\mathrm{<span\; class="notranslate">\; \&eta;</span>}}_{\mathrm{<span\; class="notranslate">\; max</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; max</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; )</span>}{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="0"\; label="S\; b"\; filenames="Y20082020788700221.png,Y20082020788700231.png"\; state="\{\{state\}\}">S</figure-callout></span><figure-callout\; id="0"\; label="S\; b"\; filenames="Y20082020788700221.png,Y20082020788700231.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 0.10</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 9</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; \&eta;</span>}}_{\mathrm{<span\; class="notranslate">\; min</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; min</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; )</span>}{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="0"\; label="S\; b"\; filenames="Y20082020788700221.png,Y20082020788700231.png"\; state="\{\{state\}\}">S</figure-callout></span><figure-callout\; id="0"\; label="S\; b"\; filenames="Y20082020788700221.png,Y20082020788700231.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 0.10</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 10</span>}<span\; class="notranslate">\; )</span>$

Wherein, Sa and Sb are the lengths of any spot formed by scanning light on the photosensitive drum 15 in the Y direction and the X direction, δ is the ratio of the minimum spot to the maximum spot on the photosensitive drum 15, and η is the microelectromechanical mirror 10 The ratio of the light spot on the reflective surface for scanning light to the light spot on the photosensitive drum 15; S _a0 and S _b0 are the lengths of the light spot for scanning light on the reflective surface of the MEMS mirror 10 in the main scanning direction and the sub-scanning direction.

In order to make the utility model more definite and detailed, enumerate the preferred embodiment and coordinate the following diagrams, the structure of the utility model and its technical characteristics are described in detail as follows:

The following embodiments of the present invention are described for the main components of the two-piece fθ lens of the micro-electromechanical laser scanning device of the present invention. Therefore, the following embodiments of the present invention are applied to a Among the micro-electro-mechanical laser scanning devices, as far as the general micro-electro-mechanical laser scanning device is concerned, except for the two-piece fθ lens disclosed in the utility model, other structures belong to the known technology, so those skilled in the art should understand that the utility model The components of the two-piece fθ lens of the disclosed MEMS laser scanning device are not limited to the structure of the embodiments disclosed below, that is, the components of the two-piece fθ lens of the MEMS laser scanning device can be modified in many ways. Changes, modifications, or even equivalent changes, such as: radius of curvature design or surface design, material selection, distance adjustment, etc. of the first lens 131 and the second lens 132 are not limited.

<First embodiment>

Refer to FIG. 3 and FIG. 6 , wherein FIG. 6 is an optical path diagram of an embodiment of the scanning light passing through the first lens and the second lens of the present invention. The first lens 131 and a second lens 132 of the two-piece type fθ lens of the present embodiment, wherein the first lens 131a is a biconvex lens, wherein the second lens 132 is formed by a pair of concave lenses, the first lens 131 The first optical surface 131a and the second optical surface 131b of the second lens 132, the third optical surface 132a and the fourth optical surface 132b of the second lens 132 are all aspheric surfaces, and formula (2) is used to design the aspheric surface formula. Its optical properties and aspheric parameters are shown in Table 1 and Table 2.

Table 1. The fθ optical characteristics of the first embodiment

Optical surface Radius of curvature (mm) (curvature) dThickness (mm) (thickness) n _dRefractive index (refraction index) MEMS reflective surface R0 0.00 26.23 1 Lens 1 (lens1) 1.491757 R1 (horizontal surface) R1x ^* -123.97 15.00 R1y ^* 275.33 R2 (horizontal surface) R2x ^* -30.25 11.45 R2y ^* -39.80 Lens 2 (lens2) 1.491757 R3 (horizontal surface) R3x ^* 36.03 8.53

R3y ^* -127.80 R4 (horizontal surface) R4x ^* -92.40 109.50 R4y ^* 82.47 Photosensitive drum (drum) R5 0.00 0.00 ^* Denotes aspherical

Table 2. Optical surface aspherical parameters of the first embodiment

Through the two-piece fθ lens, f _(1)Y = 67.05, f _(2)Y = -93.76, f _sX = 32.257, f _sY = 147 (mm), the scanning light can be converted into distance and time It is a linear scanning light spot, and scanning light spot S _a0 =19.434 (μm), S _b0 =3972.24 (μm) on the micro-electromechanical mirror 10 becomes scanning light, which is focused on the photosensitive drum 15 to form a smaller Light spot 6, and satisfy the condition of formula (4) ~ formula (10), as Table 3; Gaussian beam diameter (μm) of the light spot of the light spot distance (mm) from the central axis Y on the photosensitive drum with the central axis Z axis in the Y direction ), as shown in Table 4; and the light point distribution diagram of this embodiment is shown in Figure 7. In the figure, the diameter of the unit circle is 0.05mm.

Table three, the first embodiment satisfies the condition table

Table 4. The maximum value of the Gaussian beam diameter of the light spot on the photosensitive drum of the first embodiment

Y -107.500 -98.223 -89.648 -71.924 -53.905 -35.870 -17.906 0.000 Max(2Ga, 2Gb) 4.42E-03 3.42E-03 4.84E-03 4.79E-03 4.41E-03 4.12E-03 3.39E-03 2.66E-03

<Second Embodiment>

The first lens 131 and a second lens 132 of the two-piece type fθ lens of the present embodiment, wherein the first lens 131 is a biconvex lens, wherein the second lens 132 is formed by a pair of concave lenses, the first lens 131 The first optical surface 131a and the second optical surface 131b of the second lens 132, the third optical surface 132a of the second lens 132, and the fourth optical surface 132b of the second lens 132 are all aspheric surfaces, and the formula (2) is used to design aspheric surfaces. Its optical characteristics and aspherical parameters are shown in Table 5 and Table 6.

Table five, fθ optical characteristics of the second embodiment

Optical surface Radius of curvature (mm) (curvature) dThickness (mm) (thickness) n _dRefractive index (refraction index) MEMS reflective surface R0 0.00 18.58 1 Lens 1 (lens 1) 1.491757 R1 (horizontal surface) R1x ^* 235.60 15.00 R1y ^* -1411.53 R2 (horizontal surface) R2x ^* -29.04 9.25 R2y ^* -31.08 Lens 2 (lens 2) 1.491757 R3 (horizontal surface) R3x ^* 32.84 11.55 R3y ^* -101.85 R4 (horizontal surface) R4x ^* -73.84 110.20 R4y ^* -7.53 Photosensitive drum (drum) R5 0.00 0.00

^* Denotes aspherical

Table 6. The aspherical parameters of the optical surface of the second embodiment

Through the two-piece fθ lens, f _(1)Y = 60.299, f _(2)Y = -80.169, f _sX = 27.399, f _sY = 145.725 (mm), the scanning light can be converted into distance and time It is a linear scanning light spot, and scanning light spot S _a0 =19.434 (μm), S _b0 =3972.24 (μm) on the micro-electromechanical mirror 10 becomes scanning light, which is focused on the photosensitive drum 15 to form a smaller Light spot 8, and satisfy the condition of (4) ~ formula (10), as table seven; On the photosensitive drum 15, the Gaussian beam diameter (μm) of the light spot distance (mm) from the central axis Y distance (mm) with the central axis Z axis ), as shown in Table 8; and the spot distribution diagram of the present embodiment is as shown in Figure 8. In the figure, the diameter of the unit circle is 0.05mm.

Table seven, the second embodiment satisfies the condition table

Table 8. The maximum value of the Gaussian beam diameter of the light spot on the photosensitive drum of the second embodiment

Y -107.545 -98.226 -89.602 -71.765 -53.660 -35.621 -17.750 0.000 Max(2Ga, 2Gb) 1.40E-02 1.49E-02 1.99E-02 3.27E-03 9.30E-03 2.04E-02 2.15E-02 8.17E-03

<Third embodiment>

The first lens 131 and a second lens 132 of the two-piece type fθ lens of the present embodiment, wherein the first lens 131 is a biconvex lens, wherein the second lens 132 is formed by a pair of concave lenses, the first lens 131 The first optical surface 131a and the second optical surface 131b of the second lens 132, the third optical surface 132a of the second lens 132, and the fourth optical surface 132b of the second lens 132 are all aspheric surfaces, and the formula (2) is used to design aspheric surfaces. Its optical characteristics and aspheric parameters are shown in Table 9 and Table 10.

Table 9. The fθ optical characteristics of the third embodiment

Optical surface Radius of curvature (mm) (curvature) dThickness (mm) (thickness) n _dRefractive index (refraction index) MEMS reflective surface R0 0.00 25.30 1 Lens 1 (lens 1) 1.527 R1 (horizontal surface) R1x ^* -129.15 12.84 R1y ^* 307.34 R2 (horizontal surface) R2x ^* -29.48 12.63 R2y ^* -39.22 Lens 2 (lens 2) 1.527 R3 (horizontal surface) R3x ^* 34.60 6.80 R3y ^* -128.29 R4 (horizontal surface) R4x ^* -91.52 108.56

R4y ^* 80.87 Photosensitive drum (drum) R5 0.00 0.00 ^* Denotes aspherical

Table 10. The aspherical parameters of the optical surface of the third embodiment

Through the two-piece fθ lens, f _(1)Y = 66.828, f _(2)Y = -93.029, f _sX = 31.634, f _sY = 146.296 (mm), the scanning light can be converted into distance and time It is a linear scanning light spot, and scanning light spot S _a0 =19.434 (μm), S _b0 =3972.24 (μm) on the micro-electromechanical mirror 10 becomes scanning light, which is focused on the photosensitive drum 15 to form a smaller There are 10 light spots, and the conditions of (4) to formula (10) are satisfied, as shown in Table 11; the Gaussian beam diameter (μm) of the light spot on the photosensitive drum with the center axis Z axis in the Y direction and the distance (mm) from the center axis Y ), as shown in Table 12; the spot distribution diagram of the present embodiment is as shown in Figure 9. In the figure, the diameter of the unit circle is 0.05 mm.

Table eleven, the third embodiment satisfies the condition table

Table 12, the maximum value of the Gaussian beam diameter of the light spot on the photosensitive drum of the third embodiment

Y -108.012 -98.457 -89.700 -71.761 -53.680 -35.677 -17.799 0.000 Max(2Ga, 2Gb) 5.57E-03 7.53E-03 1.01E-02 1.39E-02 1.27E-02 6.20E-03 7.21E-03 7.90E-03

<Fourth Embodiment>

The first lens 131 and a second lens 132 of the two-piece type fθ lens of the present embodiment, wherein the first lens 131 is a biconvex lens, wherein the second lens 132 is formed by a pair of concave lenses, the first lens 131 The first optical surface 131a and the second optical surface 131b of the second optical surface 131b, the third optical surface 132a of the second lens 132 are aspheric surfaces, use formula (2) to be aspheric surface formula design; (3) Designed for the aspheric formula. Its optical properties and aspheric parameters are shown in Table 13 and Table 14.

Table 13. The fθ optical characteristics of the fourth embodiment

Optical surface Radius of curvature (mm) (curvature) dThickness (mm) (thickness) n _dRefractive index (refraction index) MEMS reflective surface R0 0.00 27.07 1 Lens 1 (lens 1) 1.52528 R1 (horizontal surface) R1x ^* -124.92 15.00 R1y ^* 268.85 R2 (horizontal surface) R2x ^* -30.37 11.92 R2y ^* -39.70 Lens 2 (lens 2) 1.52528 R3 (horizontal surface) R3x ^* 36.01 8.00 R3y ^* -124.55 R4 (Y ring image surface) R4x -93.35 110.02 R4y ^* 83.27 Photosensitive drum (drum) R5 0.00 0.00 ^* Denotes aspherical

Table 14. Optical surface aspherical parameters of the fourth embodiment

Through the two-piece fθ lens, f _(1)Y = 67.743, f _(2)Y = -94.854, f _sX = 32.864, f _sY = 147.91 (mm), the scanning light can be converted into distance and time It is a linear scanning light spot, and scanning light spot S _a0 =19.434 (μm), S _b0 =3972.24 (μm) on the micro-electromechanical mirror 10 becomes scanning light, which is focused on the photosensitive drum 15 to form a smaller There are 12 light spots, and the conditions of (4) to formula (10) are met, as shown in Table 15; Gaussian beam diameter (μm) of the light spot on the photosensitive drum with the central axis Z axis in the Y direction and the distance (mm) from the central axis Y ), as shown in Table 16; and the spot distribution diagram of the present embodiment is as shown in Figure 10. In the figure, the diameter of the unit circle is 0.05mm.

Table 15, the fourth embodiment satisfies the condition table

Table 16, the maximum value of the Gaussian beam diameter of the light spot on the photosensitive drum of the fourth embodiment

Y -107.545 -98.226 -89.602 -71.765 -53.660 -35.621 -17.750 0.000 Max(2Ga, 2Gb) 4.58E-03 3.66E-03 4.84E-03 4.59E-03 3.16E-03 3.62E-03 3.32E-03 2.50E-03

Illustrate by above-mentioned embodiment, the utility model can reach following effect at least:

(1) By the setting of the two-piece type fθ mirror of the present utility model, the micro-electro-mechanical reflector that is simple harmonic motion can be changed from the non-equal rate scanning phenomenon that decreases or increases progressively with time on the imaging surface, It is corrected to scan at a constant rate, so that the projection of the laser beam on the imaging surface is scanned at a constant rate, so that the distance between two adjacent light spots formed on the target object is equal.

(2) Through the arrangement of the two-piece fθ lens of the present invention, distortion correction can be performed on the scanning light in the main scanning direction and the sub-scanning direction, so that the light spot focused on the imaging target can be reduced.

(3) Through the arrangement of the two-piece fθ lens of the present invention, the distortion correction can be performed on the scanning light in the main scanning direction and the sub-scanning direction, so that the size of the light spot imaged on the target object can be uniformed.

The above descriptions are only preferred embodiments of the present utility model, and are only illustrative of the present utility model, rather than restrictive; those skilled in the art should understand that within the spirit and scope defined by the claims of the present utility model Many changes, modifications, and even equivalent changes can be made to it, but all will fall within the protection scope of the present utility model.

Claims (5)

1, a kind of two-chip type f theta lens of MEMS laser scanning device, it is applicable to a MEMS laser scanning device, and this MEMS laser scanning device comprises a light source in order to the emission light beam, at least and swings in order to resonance and the beam reflection of light emitted is become mems mirror, and the object in order to sensitization of scanning ray; It is characterized in that this two-chip type f theta lens comprises, start in regular turn by this mems mirror, constituted by lenticular first eyeglass and second eyeglass of a double concave, wherein this first eyeglass has one first optical surface and one second optical surface, this first optical surface and this second optical surface have at least an optical surface to be constituted by aspheric surface at main scanning direction, with the scanning ray luminous point of the angle of this mems mirror reflection and time nonlinear relationship convert to apart from the time be the scanning ray luminous point of linear relationship; Wherein this second eyeglass has one the 3rd optical surface and one the 4th optical surface, and the 3rd optical surface and the 4th optical surface have at least an optical surface to be constituted by aspheric surface at main scanning direction, and the scanning ray correction of this first eyeglass is concentrated on this object; By of scanning ray on this object the imaging of this two-chip type f theta lens with this mems mirror reflection.

2, the two-chip type f theta lens of MEMS laser scanning device as claimed in claim 1 is characterized in that further satisfying following condition at main scanning direction:

$1.6<\frac{d_3+d_4+d_5}{f_{\left(1\right)Y}}<2.5;$

$-2.0<\frac{d_5}{f_{\left(2\right)Y}}<-1.0,$

Wherein, f _{(1) Y}Be the focal length of this first eyeglass at main scanning direction, f _{(2) Y}Be the focal length of this second eyeglass at main scanning direction, d ₃This first eyeglass object side optical surface is to the distance of this second eyeglass mems mirror side optical surface, d during for θ=0 ° ₄Be this second lens thickness, d ₅This second eyeglass object side optical surface is to the distance of this object during for θ=0 °.

3, the two-chip type f theta lens of MEMS laser scanning device as claimed in claim 1 is characterized in that further satisfying following condition:

Satisfy at main scanning direction $0.2<|f_{\mathrm{sY}}\&CenterDot;(\frac{(n_{d1}-1)}{f_{\left(1\right)y}}+\frac{(n_{d2}-1)}{f_{\left(2\right)y}})|<0.4,$

Satisfy at sub scanning direction $0.8<|(\frac{1}{R_{1x}}-\frac{1}{R_{2x}})+(\frac{1}{R_{3x}}-\frac{1}{R_{4x}})f_{\mathrm{sX}}|<1.6$

Wherein, f _{(1) Y}With f _{(2) Y}Be respectively this first eyeglass and this second eyeglass focal length, f at main scanning direction _SXBe the compound focal length of two-chip type f theta lens at sub scanning direction, f _SYBe the compound focal length of two-chip type f theta lens at main scanning direction, R _IxBe the radius-of-curvature of i optical surface at sub scanning direction, n _D1With n _D2Be respectively the refractive index of this first eyeglass and this second eyeglass.

4, the two-chip type f theta lens of MEMS laser scanning device as claimed in claim 1 is characterized in that the ratio of maximum luminous point and smallest spot size on this object satisfies:

$0.8<\mathrm{\&delta;}=\frac{\min (S_b\&CenterDot;S_a)}{\max (S_b\&CenterDot;S_a)},$

Wherein, S _aWith S _bBe respectively any luminous point that scanning ray on this object forms length at main scanning direction and sub scanning direction, δ is the ratio of smallest spot and maximum luminous point on this object.

5, the two-chip type f theta lens of MEMS laser scanning device as claimed in claim 1 is characterized in that the ratio of maximum luminous point on this object and the ratio of smallest spot on this object satisfy respectively:

${\mathrm{\&eta;}}_{\max }=\frac{\max (S_b\&CenterDot;S_a)}{(S_{b0}\&CenterDot;S_{a0})}<0.10;$

${\mathrm{\&eta;}}_{\min }=\frac{\min (S_b\&CenterDot;S_a)}{(S_{b0}\&CenterDot;S_{a0})}<0.10,$

Wherein, S _A0With S _B0Be respectively the length of the luminous point of scanning ray on this mems mirror reflecting surface, S at main scanning direction and sub scanning direction _aWith S _bBe respectively the length of any luminous point of scanning ray formation on this object, η at main scanning direction and sub scanning direction _MaxBe the luminous point of scanning ray on this mems mirror reflecting surface ratio, η through scanning maximum luminous point on this object _MinBe the luminous point of scanning ray on this mems mirror reflecting surface ratio through scanning smallest spot on this object.

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