CN201199285Y - Two-piece type f theta lens of micro-electromechanical laser scanning device - Google Patents

Abstract

The utility model relates to a two-piece type f theta lens of a micro electro mechanical laser scanning device, which is provided with a first lens and a second lens, wherein the first lens and the second lens are both crescent lenses, and the concave surface of each lens is arranged at the side of a micro electro mechanical reflector; the first lens is provided with a first optical surface and a second optical surface and mainly converts scanning light spots in a scanning relation of a nonlinear relation between the reflection angle of the micro-electromechanical reflector and time into scanning light spots with linear distance and time; the second lens has a third optical surface and a fourth optical surface, and mainly corrects and condenses the scanning light of the first lens on the target object, and the first lens and the second lens both meet specific optical conditions.

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 mirror used to correct a simple harmonic motion to produce a sinusoidal angle change with time to achieve The two-piece fθ lens of the MEMS laser scanning device for the linear scanning effect required by the laser 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 (polygon mirror) to control the scanning action of the laser beam (laser beam scanning), such as the US Patent US7079171, US6377293, US6295116, or as described in Chinese Taiwan patent I198966. The principle is briefly described as follows: use a semiconductor laser to emit a laser beam (laser beam), first pass through a collimator (collimator), and then pass through an aperture (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 of the sub scanning direction (sub scanning direction) can be parallelly focused along the parallel direction of the X axis of the main scanning direction (main scanning direction) to form a line image, and then Projected onto a high-speed rotating polygonal mirror, and 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 the continuous multiple mirrors rotate at high speed, the laser beam incident on a mirror can be directed at the same angular velocity (angular velocity) along the direction parallel to the main scanning direction (X axis). ) is deflected and reflected 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 the fθ linear scanning mirror is to focus the laser beam that is reflected by the reflector on the polygon mirror and enter the fθ mirror into an elliptical light spot and project it on a photoreceptor drum (i.e., the imaging surface) , and meet the requirement of scanning linearity. However, the existing conventional 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 needs to have the function of high-speed rotation (such as 40,000 rpm), and the precision requirements are high, so that the Y-axis width of the mirror surface of the reflective surface on the general polygon mirror is extremely thin, so that the existing conventional LSU needs to be added. A cylindrical lens, so that the laser beam can be focused into a line (a point on the Y axis) through the cylindrical lens and then projected on the reflector of the polygon mirror, which increases the purchase and assembly process.

(3) The conventional multi-faceted mirror must rotate at a high speed (such as 40000 rpm), so that the rotation noise is relatively increased, and it takes a long time for the polygon mirror to start to work, thereby increasing the waiting time after starting up.

(4) In the assembly structure of the existing conventional LSU, the central axis of the laser beam projected to the polygonal mirror is not directly facing the central axis of rotation of the polygonal mirror, so that when designing the matching fθ lens, it is necessary to consider the polygonal mirror at the same time The problem of off-axis deviation (deviation) relatively increases the troubles in the design and manufacture of the fθ lens.

In recent years, in order to improve the problems of the existing conventional LSU assembly structure, an oscillating (oscillatory) micro-electromechanical mirror (MEMS mirror) has been developed on the market to replace the existing conventional polygonal mirror to control the laser beam scanning. . Micro-electromechanical mirrors are torsion oscillators with a reflective layer on the surface, which can reflect light and scan by oscillating the reflective layer. It will be used in imaging systems and scanners in the future ) or a laser scanning unit (LSU) of a laser printer (laser printer), its scanning efficiency (Scanning efficiency) will be higher than that of a traditional rotating polygonal mirror. For example, US Pat. No. 6,844,951 and US Pat. No. 6,956,597 generate at least one driving signal whose driving frequency approaches the resonant frequency of a plurality of micro-electromechanical mirrors, and drive the micro-electromechanical mirrors with a driving signal to generate a scanning path; or For example, China Taiwan patent TW M253133, which uses a micro-electromechanical mirror to replace the existing conventional rotating polygonal mirror between the collimating mirror and the fθ mirror in an LSU module structure, so as to control the projection direction of the laser beam; others Technologies disclosed in US Pat. No. 7,064,876, US Pat. No. 7,184,187, US Pat. The micro-electromechanical mirror has the advantages of small components, fast rotation speed and low manufacturing cost. However, since the micro-electromechanical mirror will perform a simple harmonic motion after receiving a voltage drive, and the mode of the simple harmonic motion is a sinusoidal relationship between time and angular velocity, and projected on the micro-electromechanical mirror, after reflection The relationship between reflection angle θ and time t is:

θ(t) = θ _s sin(2π f t) (1)

Where: f is the scanning frequency of the MEMS mirror; θ _s is the maximum single-sided scanning angle of the laser beam after passing through the MEMS mirror.

Therefore, at the same time interval Δt, the corresponding reflection angle changes are not the same and are decreasing, which is a sinusoidal relationship 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 the time is a nonlinear relationship; when the reflected light is projected on the target at different angles When , due to the relationship of different angles, the distances of the light spots generated at the same time interval are not the same.

Since the angle variation of the micro-electromechanical mirror at the peak and trough of the sine wave will increase or decrease with time, it is different from the known polygonal mirror that rotates at a constant angular velocity. On the laser scanning unit (LSU) of the mirror, it will not be able to correct the angular variation of the micro-electromechanical mirror whose swing is sinusoidal with time, resulting in the non-equal-speed scanning phenomenon of the laser beam projected on the imaging surface, and the Causes imaging deviation on the imaging surface. Therefore, the laser scanning device composed of micro-electro-mechanical mirrors, referred to as micro-electro-mechanical laser scanning device (MEMS LSU), has the characteristic that after the laser light is scanned by the micro-electro-mechanical mirror, it forms scanning light at different angles at the same time, so the development It will be an urgent need to use the fθ lens used in the MEMS laser scanning device to correct the scanning light so that the image can be correctly imaged on the target object.

It can be seen that the above-mentioned existing micro-electro-mechanical laser scanning device obviously still has inconveniences and defects in structure and use, and needs to be further improved urgently. In order to solve the above-mentioned problems, the relevant manufacturers have tried their best to find a solution, but no suitable design has been developed for a long time, and the general products do not have a suitable structure to solve the above-mentioned problems. urgent problem to be solved. Therefore, how to create a two-piece fθ lens of a MEMS laser scanning device with a new structure is one of the current important research and development topics, and it has also become a goal that the industry needs to improve.

In view of the defects existing in the above-mentioned existing micro-electromechanical laser scanning devices, the inventor, based on years of rich practical experience and professional knowledge in the design and manufacture of such products, and in conjunction with the application of academic principles, actively researches and innovates in order to create a The two-piece fθ lens of the micro-electro-mechanical laser scanning device with a new structure can improve the general existing micro-electro-mechanical laser scanning device and make it more practical. Through continuous research, design, and after repeated trial samples and improvements, the utility model with practical value is finally created.

Contents of the invention

The purpose of this utility model is to overcome the defects existing in the existing MEMS laser scanning device, and provide a two-piece fθ lens of a MEMS laser scanning device with a new structure. The technical problem to be solved is to make the two pieces The formula fθ mirror is counted from the microelectromechanical mirror, and is sequentially composed of a first mirror with a crescent shape and a concave surface on the side of the microelectromechanical mirror and a second mirror with a crescent shape and a concave surface on the side of the microelectromechanical mirror, The scanning light reflected by the micro-electromechanical mirror can be correctly imaged on the target object, and the linear scanning effect required by the laser scanning device can be achieved, which is very suitable for practical use.

Another purpose of the present utility model is to provide a two-piece fθ lens of a micro-electro-mechanical laser scanning device with a new structure. The technical problem to be solved is to reduce the area of the spot (spot) projected on the target object. , and can achieve the effect of improving the resolution, which is more suitable for practical use.

Another object of the present invention is to provide a new type of micro-electro-mechanical laser scanning device with a two-piece fθ lens. The technical problem to be solved is to make it possible to correct the distortion caused by the deviation of the scanning light from the optical axis during the main scanning. The increase in the offset of the scanning direction and the sub-scanning direction will cause the light spot imaged on the photosensitive drum to be deformed into an ellipse-like problem, and the size of each imaging light spot can be uniformed, so that the effect of improving the resolution quality can be achieved, so that it is more Suitable for practical use.

The purpose of this utility model and its technical solution are to adopt the following technical solutions to achieve. The two-piece fθ lens of a MEMS laser scanning device proposed according to the utility model is suitable for the MEMS laser scanning device. The MEMS laser scanning device includes at least one light source for emitting light beams, which swing left and right by resonance A micro-electromechanical reflective mirror that reflects the light beam emitted by the light source into scanning light, and a photosensitive target; wherein, the two-piece fθ lens includes: counting from the micro-electromechanical reflective mirror, it is composed of a new A first lens with a crescent shape and a concave surface on the side of the MEMS reflector and a second lens with a crescent shape and a concave surface on the side of the MEMS reflector, wherein: the first lens has a first An optical surface and a second optical surface, which convert the scanning light spots reflected by the micro-electromechanical mirror with a nonlinear relationship between angle and time into scanning light spots with a linear relationship between distance and time; the second lens , has a third optical surface and a fourth optical surface, which corrects and focuses the scanning light of the first lens on the target object; and reflects the micro-electromechanical mirror through the two-piece fθ lens The scanning light forms an image on the target object in the main scanning direction and the sub scanning direction.

The purpose of the utility model and the solution to its technical problems can also be further realized by adopting the following technical measures.

The aforementioned two-piece fθ lens of the MEMS laser scanning device further satisfies the following conditions in the main scanning direction:

$<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.7</span>}<span\; class="notranslate">\; <</span>\frac{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="3"\; label="d"\; filenames="Y200820009450E00291.png,Y200820009450E00301.png"\; state="\{\{state\}\}">d</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="4"\; label="d"\; filenames="Y200820009450E00291.png"\; state="\{\{state\}\}">d</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 5</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; Y</span>}}}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 0</span>}$

$\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; <</span>\frac{{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 5</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; Y</span>}}}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 0.6</span>}$

Wherein, f _(1)Y is the focal length of the first lens in the main scanning direction, f _(2)Y is the focal length of the second lens in the main scanning direction, d ₃ is the first lens of θ=0° The distance from the optical surface on the object side of the target to the optical surface on the microelectromechanical mirror side of the second lens, _d4 is the thickness of the second lens at θ=0°, and _d5 is the target object side of the second lens at θ=0° The distance from the optical surface to the target object.

The two-piece fθ lens of the aforementioned MEMS laser scanning device further satisfies the following conditions:

in the main scanning direction to meet the

$\mathrm{<span\; class="notranslate">\; 0.05</span>}<span\; class="notranslate">\; <</span><span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; (</span>\frac{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; Y</span>}}}<span\; class="notranslate">\; +</span>\frac{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; Y</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span><span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 0.5</span>}$

Satisfied in the sub-scanning direction

$\mathrm{<span\; class="notranslate">\; 0.1</span>}<span\; class="notranslate">\; <</span><span\; class="notranslate">\; |</span><span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}\mathrm{<span\; class="notranslate">\; x</span>}}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; x</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}\mathrm{<span\; class="notranslate">\; x</span>}}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}\mathrm{<span\; class="notranslate">\; x</span>}}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 10.0</span>}$

Wherein, f _(1)Y and f _(1)X are the focal lengths of the first lens in the main scanning direction and the sub-scanning direction, and f _(2)Y and f _(2)X are the focal lengths of the second lens in the main scanning direction direction and the focal length of the sub-scanning direction, f _s is the composite focal length of the two-piece fθ lens, R _ix is the radius of curvature of the i-th optical surface in the X direction; R _ix is the curvature radius of the i-th optical surface in the X direction; nd1 and nd2 is the refractive index of the first lens and the second lens.

The two-piece fθ lens of the aforementioned micro-electromechanical laser scanning device, wherein the ratio of the maximum light spot to the minimum light spot size of the light spot satisfies:

$\mathrm{<span\; class="notranslate">\; 0.2</span>}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; \&delta;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; min</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; max</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; )</span>}$

Wherein, S _a and S _b are the lengths of any light spot formed by scanning light on the photosensitive drum in the main scanning direction and the sub-scanning direction, and δ is the ratio of the smallest light spot to the largest light spot on a photosensitive drum.

The two-piece fθ lens of the aforementioned micro-electromechanical laser scanning device, wherein the ratio of the maximum light spot on the target and the ratio of the minimum light spot on the target satisfies respectively:

${\mathrm{<span\; class="notranslate">\; \&eta;</span>}}_{\mathrm{<span\; class="notranslate">\; max</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; max</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; )</span>}{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="0"\; label="S\; b"\; filenames="Y200820009450E00291.png"\; state="\{\{state\}\}">S</figure-callout></span><figure-callout\; id="0"\; label="S\; b"\; filenames="Y200820009450E00291.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 0.25</span>}$

${\mathrm{<span\; class="notranslate">\; \&eta;</span>}}_{\mathrm{<span\; class="notranslate">\; min</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; min</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; )</span>}{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="0"\; label="S\; b"\; filenames="Y200820009450E00291.png"\; state="\{\{state\}\}">S</figure-callout></span><figure-callout\; id="0"\; label="S\; b"\; filenames="Y200820009450E00291.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 0.05</span>}$

Wherein, S _a0 and S _b0 are the lengths of the light spot of the scanning light on the reflecting surface of the micro-electromechanical mirror in the main scanning direction and the sub-scanning direction, and S _a and S _b are the lengths formed by the scanning light on the photosensitive drum. The length of any light point in the main scanning direction and the sub-scanning direction, η _max is the ratio of the maximum light point on the target through scanning the light point of the scanning light on the reflective surface of the micro-electromechanical mirror, and η _min is the ratio of the maximum light point on the target The ratio of the light spot of the scanning light on the reflective surface of the micro-electromechanical mirror to the minimum light spot on the target object after scanning.

Compared with the prior art, the utility model has obvious advantages and beneficial effects. As can be seen from the above technical solutions, the main technical contents of the utility model are as follows:

In order to achieve the above purpose, the utility model provides a two-piece fθ lens of a micro-electromechanical laser scanning device, which is suitable for at least one light source that emits a laser beam, and reflects the laser beam emitted by the light source into a scanning light by resonating left and right swings. MEMS mirror to image on the target object; for laser printers (ie 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, and passes through the micro The electromechanical mirror scans left and right, and the microelectromechanical mirror reflects the laser beam to form a scanning light. After the scanning light passes through the two-piece fθ mirror of the utility model to correct the angle and position, it forms a spot on the photosensitive drum. There is a photosensitizer, which can sense the accumulation of toner on the paper, so that the data can be printed out.

In addition, in order to achieve the above purpose, the utility model also provides a two-piece fθ lens, including a first lens and a second lens in order from the micro-electromechanical mirror, wherein the first lens has a first The optical surface and a second optical surface mainly correct the non-constant-rate scanning phenomenon in which the distance between the light spots on the imaging surface of the micro-electromechanical mirror in simple harmonic motion decreases or increases with time to constant-rate scanning. , so that the projection of the laser beam on the imaging surface is scanned at a constant rate. The second lens has a third optical surface and a fourth optical surface, which are mainly used to even out the imaging deviation on the photosensitive drum caused by the deviation of the optical axis of the scanning light in the main scanning direction and the sub-scanning direction. The scanning light of a mirror is corrected to focus on the target object.

By means of the above technical solution, the two-piece fθ lens of the MEMS laser scanning device of the utility model has at least the following advantages and beneficial effects:

1. In the utility model, the two-piece fθ mirror is counted from the microelectromechanical reflector, followed by a crescent-shaped first lens with a concave surface on the microelectromechanical reflector side and a crescent-shaped concave surface on the microelectromechanical reflector. The second lens on the side of the mirror can correctly image the scanning light reflected by the micro-electromechanical mirror on the target object, and can achieve the linear scanning effect required by the laser scanning device, which is very suitable for practical use.

2. The utility model can achieve the effect of improving the resolution by reducing the area of the spot projected on the target object, so that it is more suitable for practical use.

3. The utility model can effectively distort and correct the problem that the deviation in the main scanning direction and the sub-scanning direction increases due to the deviation of the scanning light from the optical axis, so that the light spot imaged on the photosensitive drum is deformed into a similar ellipse, and each The size of the imaging light spot can be uniformed, and the effect of improving the resolution quality can be achieved, so that it is more suitable for practical use.

To sum up, the utility model relates to a two-piece fθ lens of a micro-electromechanical laser scanning device, which has a first lens and a second lens, both of which are crescent-shaped and the concave surface is on the side of the micro-electromechanical mirror. Consists of lenses; wherein, the first lens has a first optical surface and a second optical surface, mainly converting the scanning light spot of the scanning relationship between the angle and the time nonlinear relationship reflected by the micro-electromechanical mirror A scanning light spot whose distance and time are linear; the second lens has a third optical surface and a fourth optical surface, mainly for correcting and focusing the scanning light of the first lens on the target object, and Both the first lens and the second lens meet specific optical conditions, and through the arrangement of the first lens and the second lens, the purpose and effect of linear scanning effect and high-resolution scanning can be achieved. The utility model has the above-mentioned many advantages and practical value, it has great improvement no matter in product structure or function, has remarkable progress in technology, and has produced easy-to-use and practical effect, and compared with the existing micro-electromechanical The laser scanning device has enhanced outstanding functions, so it is more suitable for practical use, and it is a novel, progressive and practical new design.

The above description is only an overview of the technical solutions of the present utility model. In order to better understand the technical means of the present utility model, it can be implemented according to the contents of the description, and in order to make the above-mentioned and other purposes, features and advantages of the present utility model better It is obvious and easy to understand. The preferred embodiments are specifically cited below, together with the accompanying drawings, and detailed descriptions are as follows.

Description of drawings

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.

Fig. 2 is a graph showing the relationship between scanning angle θ and time t of a MEMS mirror.

FIG. 3 is an optical path diagram and symbol explanatory diagram of scanning light passing through the first mirror and the second mirror.

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 an optical path diagram of the first preferred embodiment of the utility model.

Fig. 6 is a schematic diagram of light spots of the first preferred embodiment of the present invention.

Fig. 7 is an optical path diagram of the second preferred embodiment of the present invention.

Fig. 8 is a schematic diagram of light spots of the second preferred embodiment of the present invention.

Fig. 9 is an optical path diagram of the third preferred embodiment of the present invention.

Fig. 10 is a schematic diagram of light spots of the third preferred embodiment of the present invention.

Fig. 11 is an optical path diagram of the fourth preferred embodiment of the present invention.

Fig. 12 is a schematic diagram of light spots of the fourth preferred embodiment of the present invention.

10: photosensitive drum 11: laser light source

111: beam of light 113a, 113b, 113c: scanning light

114a, 114b: scanning light 115a, 115b: scanning light

131: First lens 132: Second lens

14a, 14b: Photoelectric sensor 15: Photosensitive drum

16: Cylindrical mirror 2, 2a, 2b, 2c: Light spot

3: Effective scanning window

5: 0.1mm analytical circle (Geometrical Spot)

7: 0.1mm analytical circle (Geometrical Spot)

9: 0.1mm analytical circle (Geometrical Spot)

11: 0.1mm analytical circle (Geometrical Spot)

6a, 6b, 6c, 6d: light spots 6e, 6f, 6g, 6h: light spots

8a, 8b, 8c, 8d, 8e: light spots 8f, 8g, 8h, 8i, 8j: light spots

10a, 10b, 10c, 10d, 10e: Light spots 10f, 10g, 10h, 10i, 10j: Light spots

12a, 12b, 12c, 12d, 12e: light spots 12f, 12g, 12h, 12i, 12j: light spots

Detailed ways

In order to further explain the technical means and effects that the utility model takes to achieve the predetermined utility model purpose, below in conjunction with the accompanying drawings and preferred embodiments, the two-piece fθ lens of the micro-electromechanical laser scanning device proposed according to the utility model will be described below. Specific embodiments, structures, features and effects thereof are described in detail below.

The aforementioned and other technical contents, features and effects of the present utility model will be clearly presented in the following detailed description of preferred embodiments with reference to the drawings. Through the description of the specific implementation, one can get a deeper and more specific understanding of the technical means and effects of the utility model to achieve the intended purpose, but the attached drawings are only for reference and description, and are not used to explain the present invention. Utility models are restricted.

Please refer to FIG. 1 , which 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 preferred embodiment of the present utility model includes a first lens 131 with a first optical surface 131a and a second optical surface 131b, and a third optical lens with a third optical surface. The surface 132a and the second lens 132 of a fourth optical surface 132b are 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 target is implemented with 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 , 114 a , 114 b , 115 a , and 115 b in a resonant swinging manner. Wherein, the projection of the scanning rays 113a, 113b, 114a, 114b, 115a, 115b in the X direction is called the sub scanning direction (sub scanning direction), the projection in the Y direction is called the main scanning direction (mains scanning direction), and The scanning angle of the MEMS mirror 10 is θc.

Because the microelectromechanical mirror 10 is in a simple harmonic motion, its motion angle is a sinusoidal change with time, as shown in Figure 2, which is a diagram of the relationship between the scanning angle θ and time t of a microelectromechanical mirror, so the scanning light The injection angle and time have a nonlinear relationship. As shown in the illustration, the wave peak a-a' and wave trough bb', the swing angle is obviously smaller than the wave band 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. The laser beam 111 is reflected by the microelectromechanical mirror 10 from the peak of FIG. It is equivalent to the scanning light 115a of Fig. 1; when the photoelectric sensor 14a detects the scanning light, it means that the MEMS mirror 10 is swinging to +θp angle, which is equivalent to the scanning light 114a of Fig. 1; When the electromechanical mirror 10 scans point a in Fig. 2 of angle change, it is equivalent to the position of scanning light 113a at this moment; at this time, the laser light source 11 is controlled to start emitting laser beam 111, and when scanning to point b in Fig. 2, it is equivalent to The position of the scanning light 113b is reached (the laser light source 11 emits the laser beam 111 within the corresponding ±θn angle); when the micro-electromechanical mirror 10 bounces, the laser light source 11 is also controlled to start emitting the laser beam in the band a'-b' 111; thus complete a cycle.

Please refer to FIG. 3 , which is an optical path diagram and symbol explanatory 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 reflector 10 enters ±θn, the laser light source 11 starts to emit the laser beam 111 to be scanned, which is reflected by the MEMS reflector 10 into scanning light, and the scanning light Can pass through the first mirror 131 and be refracted by the first optical surface and the second optical surface of the first mirror 131, and convert the scanning light reflected by the micro-electromechanical mirror 10 into a linear distance and time. relational scanning rays. And, after passing through the first lens 131 and the second lens 132, through the first optical surface, the second optical surface, the third optical surface, the fourth optical surface and each optical surface of the first lens 131 and the second lens 132 The focusing effect formed by the spacing of the scanning light is focused on the photosensitive drum 15, and a column of light spots (Spot) 2 is formed on the photosensitive drum 15, and projected on the photosensitive drum 15, the distance between the two farthest spots 2 It is called effective scanning window 3. Wherein, d1 is the distance from the MEMS mirror 10 to the first optical surface, d2 is the distance from the first optical surface to the second optical surface, d3 is the distance from the second optical surface to the third optical surface, and d4 is the distance from the third optical surface surface to the fourth optical surface, d5 is the distance from the fourth optical surface to the photosensitive drum 15, R1 is the curvature radius (Curvature) of the first optical surface, R2 is the curvature radius of the second optical surface, R3 is the third optical surface The radius of curvature of the surface and R4 are the radius of curvature of the fourth optical surface.

Please refer to FIG. 4 , which 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. After the scanning light is projected on the photosensitive drum, the schematic diagram of the light spot area changing with the different projecting positions. 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, since the angle incident on the first lens 131 and the second lens 132 is zero, in the main scanning direction The deflection rate is zero, so the light spot 2a imaged on the photosensitive drum 15 is a type of circle. When the scanning rays 113b and 113c pass through the first lens 131 and the second lens 132 and are projected on the photosensitive drum 15, since the angle formed by the first lens 131 and the second lens 132 and the optical axis is not zero, therefore The offset rate in the main scanning direction is not zero, so that the projected length in the main scanning direction is larger than the light spot formed by the scanning light 111a; The formed light spots will also be larger; therefore, the light spots 2b, 2c imaged on the photosensitive drum 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 _scanning light spots on the reflection surface of the micro-electromechanical mirror in the main scanning direction (Y direction) and the sub-scanning direction (X direction); The length of any light point formed by the aiming line in the Y direction and the X direction. The two-piece fθ lens of the utility model can correct the size of the light spot through the distortion of the fθ lens in the main scanning direction, so that the size of the light spot can be controlled within a limited range. The distortion correction of the lens keeps the spot size within a limited range. Through the distortion correction of the optical surfaces of the two-piece fθ lens of the present invention, the first lens 131 and the second lens 132 in the main scanning direction and the sub-scanning direction, the size distribution of each light spot (the ratio of the maximum light spot to the minimum light spot) can be made , and controlled within an appropriate range, can provide a consistent resolution.

In order to achieve the above effects, the two-piece fθ lens of the present invention can use a spherical curved surface or an aspheric curved surface on the first optical surface or the second optical surface of the first lens and the third optical surface or the fourth optical surface of the second lens. For the design, if an aspheric surface is used for the design, the aspheric surface is designed according to the following 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="Y200820009450E00291.png,Y200820009450E00301.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="Y200820009450E00291.png,Y200820009450E00301.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 (SAG) from any point on the lens to the tangent plane at point 0 in the direction of the optical axis; C _x and _Cy are the curvatures in the X direction and Y direction respectively; K _x and Ky are the curvatures in the X direction and the _Y direction respectively. Conic coefficient in the Y direction; A _R , B _R , C _R and _DR are the four, six, eight and ten power conic deformation coefficients (deformation from the conic); A _P , B _P , C _P and D _P are respectively non-rotationally symmetric (non-rotationally symmetric components) conic deformation coefficients (deformation from the conic ); when C _x ＝C _y , K _x ＝K _y and A _P ＝B _p ＝C _p ＝D _p ＝0, it is simplified to a single aspheric 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="Y200820009450E00291.png,Y200820009450E00301.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="Y200820009450E00291.png,Y200820009450E00301.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="Y200820009450E00291.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="Y200820009450E00291.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">\; <figure-callout\; id="8"\; label="Y"\; filenames="Y200820009450E00351.png"\; state="\{\{state\}\}">Y</figure-callout></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 from any point on the lens in the direction of the optical axis to the tangent plane at point 0 (SAG); 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 the coefficient deformation from the conic of the 4th, 6th, 8th, and 10th powers); when C _x ＝C _y and K _y ＝A _P ＝B _p ＝C _p =D _p =0 simplifies to a single spherical surface.

In order to make the scanning speed of the scanning light imaging on the target object be an equal rate, at two identical time intervals, the distance between the two light spots is equal; the two-piece fθ lens of the utility model can connect the scanning light 113a to the scanning light Between 113b, the first lens 131 and the second lens 132 are used 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, form two images on the photosensitive drum 15 of the image. The light spots are equidistant from each other. Furthermore, when the laser beam 111 is reflected by the MEMS reflector 10, its light spot is larger. If the scanning light passes through the distance between the MEMS reflector 10 and the photosensitive drum 15, the light spot will be larger, which is not practical. Resolution requirements; the two-piece fθ lens of the utility model can further focus the scanning light 113a reflected by the micro-electromechanical mirror 10 to the scanning light 113b on the photosensitive drum 15 for imaging to form a smaller light spot; Or, the two-piece fθ lens of the present utility model can even the size of the light spot imaged on the photosensitive drum 15 (limited to a range that meets the resolution requirements), so as to obtain the best resolution.

The two-piece fθ mirror of the present utility model comprises, counting from the MEMS reflector 10 in sequence, a first mirror 131 and a second mirror 132, both of which are crescent-shaped and whose concave surface is on the MEMS reflector side. The first mirror 131 has a first optical surface and a second optical surface, and converts the scanning light spot reflected by the micro-electromechanical mirror 10 with a nonlinear relationship between angle and time into a scanning light spot with a linear relationship between distance and time. point; wherein, the second lens 132 has a third optical surface and a fourth optical surface, and corrects and focuses the scanning light of the first lens 131 on the target object; the micro-electromechanical mirror 10 The reflected scanning light is imaged on the photosensitive drum 15; wherein, the first optical surface, the second optical surface, the third optical surface and the fourth optical surface have at least one optical surface composed of an aspheric surface in the main scanning direction, At least one of the first optical surface, the second optical surface, the third optical surface and the fourth optical surface is an aspheric surface 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 formula (4) and formula (5) in the main scanning direction:

$<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.7</span>}<span\; class="notranslate">\; <</span>\frac{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="3"\; label="d"\; filenames="Y200820009450E00291.png,Y200820009450E00301.png"\; state="\{\{state\}\}">d</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="4"\; label="d"\; filenames="Y200820009450E00291.png"\; state="\{\{state\}\}">d</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 5</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; Y</span>}}}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

$\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; <</span>\frac{{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 5</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; Y</span>}}}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 0.6</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

Alternatively, satisfy equation (6) in the main scanning direction

$\mathrm{<span\; class="notranslate">\; 0.05</span>}<span\; class="notranslate">\; <</span><span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; (</span>\frac{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; Y</span>}}}<span\; class="notranslate">\; +</span>\frac{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; Y</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span><span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 0.5</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

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

$\mathrm{<span\; class="notranslate">\; 0.1</span>}<span\; class="notranslate">\; <</span><span\; class="notranslate">\; |</span><span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}\mathrm{<span\; class="notranslate">\; x</span>}}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; x</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}\mathrm{<span\; class="notranslate">\; x</span>}}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}\mathrm{<span\; class="notranslate">\; x</span>}}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 10.0</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

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, and _d3 is θ=0° on the target side of the first mirror 131 The distance from the optical surface to the second mirror 132 microelectromechanical reflector side optical surface, d ₄ is θ=0 ° second lens thickness, d ₅ is the distance from the θ=0 ° second lens object side optical surface to the target object, f _(1)X is the focal length of the first lens in the sub-scanning direction, f _(2)X is the focal length of the second lens in the sub-scanning direction, f _s is the combined focal length of the two-piece fθ lens, R _ix The curvature radius of the i-th optical surface in the X direction; R _ix is the curvature radius of the i-th optical surface in the X direction; n _d1 and n _d2 are the refraction indexes of the first lens and the second lens.

Furthermore, the uniformity of the light spot formed by the two-piece fθ lens of the present invention can be represented by the ratio δ of the maximum light spot to the minimum light spot size, which satisfies formula (8):

$\mathrm{<span\; class="notranslate">\; 0.2</span>}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; \&delta;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; min</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; max</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

Furthermore, the resolution formed by the two-piece fθ eyeglass of the present utility model can use η _max to be the ratio of the maximum light spot on the photosensitive drum 15 through scanning the light spot of the scanning light on the reflection surface of the microelectromechanical mirror 10 (Ratio of scanning light of maximum spot) and η _min are represented by the ratio (Ratio of scanning light of minimum spot) of the light spot of the scanning light on the microelectromechanical mirror 10 reflective surface scanned on the target object, It can satisfy formulas (9) and (10),

${\mathrm{<span\; class="notranslate">\; \&eta;</span>}}_{\mathrm{<span\; class="notranslate">\; max</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; max</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; )</span>}{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="0"\; label="S\; b"\; filenames="Y200820009450E00291.png"\; state="\{\{state\}\}">S</figure-callout></span><figure-callout\; id="0"\; label="S\; b"\; filenames="Y200820009450E00291.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 0.25</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 9</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; \&eta;</span>}}_{\mathrm{<span\; class="notranslate">\; min</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; min</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; )</span>}{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="0"\; label="S\; b"\; filenames="Y200820009450E00291.png"\; state="\{\{state\}\}">S</figure-callout></span><figure-callout\; id="0"\; label="S\; b"\; filenames="Y200820009450E00291.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 0.05</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 10</span>}<span\; class="notranslate">\; )</span>$

Among them, S _a and S _b are the lengths of any light spot formed by the scanning light on the photosensitive drum in the main scanning direction and the sub-scanning direction, and δ is the ratio of the smallest light spot to the largest light spot on the photosensitive drum; S _a0 and S _b0 is the length of the light spot of the scanning light on the reflecting surface of the micro-electromechanical mirror in the main scanning direction and the sub-scanning direction.

In order to make the utility model more clear and detailed, the preferred embodiments are listed hereby and cooperate with the following diagrams, and the structure and technical characteristics of the utility model are described in detail as follows:

The following embodiments of the utility model are described for the main components of the two-piece fθ lens of the micro-electromechanical laser scanning device of the utility model, so although the embodiments of the utility model disclosed below are applied to a micro In the electromechanical laser scanning device, but as far as the general microelectromechanical laser scanning device is concerned, except for the two-piece fθ mirror disclosed by the utility model, other structures belong to the technology notified by ordinary technical personnel, so it is generally familiar in this field Those skilled in the art understand that the constituent elements of the two-piece fθ lens of the MEMS laser scanning device disclosed in the utility model are not limited to the structure of the embodiment disclosed below, that is, the MEMS laser scanning device The constituent elements of the two-piece fθ lens can be changed, modified, or even equivalently changed, such as: the curvature radius design or surface design, material selection, and spacing adjustment of the first lens and the second lens. not limited.

<First embodiment>

The first lens and a second lens of the two-piece type fθ lens of the present embodiment are both crescent-shaped lenses with a concave surface on the side of the micro-electromechanical mirror. The four optical surfaces are aspherical surfaces, and formula (2) is used to design aspheric surface formulas; the second optical surface of the first lens and the third optical surface of the second lens are aspherical surfaces, and formula (2) is used to design aspheric surface formulas . Its optical characteristics and aspheric parameters are shown in Table 1 and Table 2 below.

Table 1. The fθ optical characteristics of the first embodiment

Table two, the optical surface aspherical parameters of the first embodiment

Its optical path diagram of the optical surface of the two-piece type fθ eyeglass formed through this is as shown in Figure 5, which is the optical path diagram of the first preferred embodiment of the present utility model, f _(1)Y =152.84, f _(2)Y =-132.768 can convert the scanning light into a scanning light spot whose distance and time are linear, and scan the light spot S _a0 =154.6, S _b0 =3587.48 on the micro-electromechanical mirror 10 to become a scanning light, which is carried out on the photosensitive drum 15 Focus to form a smaller light spot 6, and satisfy the conditions of formula (4) to formula (10), as shown in Table 3; the distribution of the light spot size from the central axis 5 to the left side of the scanning window 3 is: light spot 4a (central axis), 4b-4j (the leftmost side of the scanning window 3), as shown in FIG. 6, is a schematic diagram of light spots in the first preferred embodiment of the present invention. In addition, the right side and the left side of the scanning window 3 are symmetrically the same.

Table three, the first embodiment satisfies the condition table

<Second Embodiment>

The first lens and a second lens of the two-piece type fθ lens in this embodiment are both crescent-shaped lenses with a concave surface on the side of the micro-electromechanical mirror. The first optical surface of the first lens is an aspherical surface, and the use formula (3) design for the aspheric surface formula; be the aspherical surface at the second optical surface of the first eyeglass and the third learning surface of the second eyeglass, use formula (2) to be the aspheric surface formula design; the 4th learning surface of the second eyeglass is for the sphere. Its optical characteristics and aspheric parameters are shown in Table 4 and Table 5 below.

Table 4. The fθ optical characteristics of the second embodiment

fs=155.0 optical surface Radius of curvature (mm) dThickness (mm) nd refractive index (optical surface) (curvature) (thickness) (refraction index) MEMS reflective surface R0 0.000000 35.00 1 lens 1 1.533 R1(Y Toroid) Rlx* -31.195065 8.00 R1y* -66.689255 R2 (Anamorphic) R2x* -11.537224 15.00 R2y* -59.430437 lens 2 1.533 R3 (Anamorphic) R3x* 138.084983 8.00 R3y* -380.314932 R4(Y Toroid) R4x 291.593710 73.86 R4 -406.695465 Photosensitive drum (drum) R5 0.000000 0.00 ^* Denotes aspherical

Table five, the optical surface aspherical parameters of the second embodiment

Its optical path diagram of the optical surface of the two-piece type fθ eyeglass formed through this is as shown in Figure 7, which is the optical path diagram of the second preferred embodiment of the present utility model, f _(1)Y =750.157, f _(2)Y =-12420.515 can convert the scanning light into a scanning light spot whose distance and time are linear, and scan the light spot S _a0 =14.27, S _b0 =3027.158 on the micro-electromechanical mirror 10 to become a scanning light, which is carried out on the photosensitive drum 15 Focus to form a smaller light spot 8, and satisfy the conditions of (4) ~ formula (10), as shown in Table 3; the distribution of the light spot size from the central axis 7 to the left side of the scanning window 3 is: light spot 5a ( central axis), 5b-5j (the leftmost side of the scanning window 3), as shown in FIG. 8 , is a schematic diagram of light spots in the second preferred embodiment of the present invention. In addition, the right side and the left side of the scanning window 3 are symmetrically the same.

Table six, the second embodiment satisfies the condition table

<Third embodiment>

The first lens and a second lens of the two-piece type fθ lens of the present embodiment are all crescent-shaped and the lens whose concave surface is on the side of the micro-electromechanical mirror is formed, and the first optical surface of the first lens and the fourth lens of the second lens are The optical surface is a spherical surface in the sub-scanning direction; the second optical surface of the first eyeglass and the third optical surface of the second eyeglass are aspherical surfaces, and the formula (2) is used to design the aspheric surface formula; the first optical surface of the first eyeglass and the third optical surface of the second eyeglass The fourth optical surface of the second lens is an aspheric surface in the main scanning direction, and the formula (3) is used to design the aspheric surface formula. Its optical characteristics and aspheric parameters are shown in Table 7 and Table 8 below.

Table seven, fθ optical characteristics of the third embodiment

Table eight, the optical surface aspherical parameters of the third embodiment

Its optical path diagram of the optical surface of the formed two-piece fθ eyeglass is as shown in Figure 9, which is the optical path diagram of the third preferred embodiment of the present utility model, f _(1)Y =4831.254, f _(2)Y = -559.613 can convert the scanning light into a scanning light spot whose distance and time are linear, and scan the light spot S _a0 =14.488, S _b0 =2800.64 on the micro-electromechanical mirror 10 into scanning light, and focus on the photosensitive drum 15 , form a smaller light spot 10, and satisfy the conditions of (4) ~ formula (10), as shown in Table 3; the distribution of the light spot size from the central axis 9 to the left side of the scanning window 3 is: light spot 6a (center axis), 6b-6j (the leftmost side of the scanning window 3), as shown in Figure 10, is a schematic diagram of the light spot of the third preferred embodiment of the present invention. In addition, the right side and the left side of the scanning window 3 are symmetrically the same.

Table nine, the third embodiment satisfies the condition table

<Fourth Embodiment>

The first lens and a second lens of the two-piece type fθ lens of the present embodiment are all crescent-shaped and the lens whose concave surface is on the side of the micro-electromechanical mirror is formed. The first optical surface of the first lens, the fourth lens of the second lens The optical surface is an aspheric surface, and the formula (3) is used to design the aspheric surface formula; the second optical surface of the first lens and the third optical surface of the second lens are aspheric surfaces, and the formula (2) is used to design the aspheric surface formula. Its optical properties and aspheric parameters are shown in Table 10 and Table 11 below.

Table ten, fθ optical characteristics of the fourth embodiment

Table eleven, the optical surface aspherical parameters of the fourth embodiment

The optical path diagram of the optical surface of the two-piece fθ lens formed through this is shown in FIG. 11 , which is the optical path diagram of the fourth preferred embodiment of the present invention. f _(1)Y =199.885, f _(2)Y =-162.471 can convert the scanning light into a scanning light point whose distance and time are linear, and make the light point S _a0 =14.374, S _b0 on the microelectromechanical mirror 10 =2917.652 scanning becomes scanning light, focuses on the photosensitive drum 15 to form a smaller spot 12, and satisfies the conditions of (4) ~ formula (10), as shown in Table 3; the size of the spot is from central axis 11 to The distribution on the left side of the scanning window 3 is: light spots 7a (central axis), 7b-7j (the leftmost side of the scanning window 3), as shown in FIG. 12 , which is a schematic diagram of light spots in the fourth preferred embodiment of the present invention. In addition, the right side and the left side of the scanning window 3 are symmetrically identical.

Table twelve, the fourth embodiment satisfies the condition table

Illuminated by the above-mentioned embodiments, the utility model can at least achieve the following effects:

1. With the arrangement of the two-piece fθ lens of the present utility model, the spot spacing of the micro-electromechanical mirror in simple harmonic motion on the imaging surface can be changed from the non-equal-speed scanning phenomenon that decreases or increases with time, and can be corrected. For constant speed scanning, the projection of the laser beam on the imaging surface is scanned at a constant speed, so that the distance between two adjacent light spots formed on the target object is equal.

2. With the arrangement of the two-piece fθ lens of the present invention, the distortion can be corrected to scan the 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. With the arrangement of the two-piece fθ lens of the present invention, the distortion can be corrected to scan the 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 are only preferred embodiments of the present utility model, and do not limit the utility model in any form. Although the utility model has been disclosed as above with preferred embodiments, it is not intended to limit the utility model. Any Those who are familiar with this profession, without departing from the scope of the technical solution of the present utility model, can use the technical content disclosed above to make some changes or modify equivalent embodiments with equivalent changes, but all without departing from the technical solution of the utility model Any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the utility model still belong to the scope of the technical solution of the utility model.

Claims (6)

1. the two-chip type f theta lens of a MEMS laser scanning device, be applicable to MEMS laser scanning device, described MEMS laser scanning device comprises a light source in order to the emission light beam at least, swinging with resonance becomes the beam reflection of light emitted mems mirror, and the object in order to sensitization of scanning ray; It is characterized in that described two-chip type f theta lens comprises: start at by described mems mirror, in regular turn by one crescent and concave surface at one first eyeglass of described mems mirror side, and one crescent and concave surface constitute at one second eyeglass of mems mirror side, wherein:

Described first eyeglass has one first optical surface and one second optical surface, be scanning ray luminous point with the angle of described mems mirror reflection and time nonlinear relationship convert to apart from the time be the scanning ray luminous point of linear relationship;

Described second eyeglass has one the 3rd optical surface and one the 4th optical surface, is that the scanning ray correction with described first eyeglass is concentrated on the described object;

By described two-chip type f theta lens, the scanning ray of described mems mirror reflection is retouched direction and sub scanning direction imaging on described object at a main Sweep.

2. the two-chip type f theta lens of MEMS laser scanning device according to claim 1 is characterized in that described main scanning direction further satisfies following condition:

$-0.7<\frac{d_3+d_4+d_5}{f_{\left(1\right)Y}}<0$

$0<\frac{d_5}{f_{\left(2\right)Y}}<0.6$

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

3. the two-chip type f theta lens of MEMS laser scanning device according to claim 1 is characterized in that described main scanning direction and described sub scanning direction further satisfy following condition:

Described main scanning direction satisfies

$0.05<\left|f_s(\frac{(n_{d1}-1)}{f_{\left(1\right)Y}}+\frac{(n_{d2}-1)}{f_{\left(2\right)Y}})\right|<0.5$

Described sub scanning direction satisfies

$0.1<|(\frac{1}{R_{1x}}-\frac{1}{R_{2x}})+(\frac{1}{R_{3x}}-\frac{1}{R_{4x}})f_s|<10.0$

Wherein, f _{(1) Y}With f _{(1) X}Be the focal length of described first eyeglass at described main scanning direction and described sub scanning direction, f _{(2) Y}With f _{(2) X}Be the focal length of described second eyeglass at described main scanning direction and described sub scanning direction, f _sBe the compound focal length of two-chip type f theta lens, R _IxThe i optical surface is in the radius-of-curvature of directions X; R _IxBe the radius-of-curvature of i optical surface at directions X; n _D1With n _D2Refractive index for described first eyeglass and described second eyeglass.

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

$0.2<\mathrm{\&delta;}=\frac{\min (S_b\&CenterDot;S_a)}{\max (S_b\&CenterDot;S_a)}$

Wherein, S _aWith S _bFor scanning any luminous point that light forms length at described main scanning direction and described sub scanning direction on the described object, δ is the ratio of smallest spot and maximum luminous point on the described object.

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

${\mathrm{\&eta;}}_{\max }=\frac{\max (S_b\&CenterDot;S_a)}{(S_{b0}\&CenterDot;S_{a0})}<0.25$

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

Wherein, S _A0With S _B0For scanning the length of the luminous point of light at described main scanning direction and described sub scanning direction, S on the described mems mirror reflecting surface _aWith S _bFor scanning any luminous point that light forms length, η on the described object at described main scanning direction and described sub scanning direction _MaxBe the luminous point that scans light on the described mems mirror reflecting surface ratio, η through scanning maximum luminous point on described object _MinBe the luminous point that scans light on the described mems mirror reflecting surface ratio through scanning smallest spot on described object.

6. according to the two-chip type f theta lens of each described MEMS laser scanning device of claim 1 to 5, it is characterized in that described object is a photosensitive drums.

Images