JPH11194288A - Light beam exit lens system and optical scanning device using the same - Google Patents

Abstract

(57) Abstract: A light beam capable of performing a small, high-definition optical scan by forming a light beam emission lens system with less aberration and using the light beam emission lens system in an optical scanning device. An emission lens system and an optical scanning device using the same. SOLUTION: In a light beam emitting lens system 101 for converting a state of a light beam emitted from a light source means 1 to another state by a biconvex single lens 4, the focal length of the biconvex single lens is f, and the biconvex single lens is The curvature radii of the entrance and exit lens surfaces are R1 and R2, respectively, and the distance from the lens surface on the exit-side optical axis of the biconvex single lens to the imaging point of the exit light beam is SK.
When the numerical aperture of the light beam exit lens system is NA,
−0.09 <(R1 + R2) / (R1 × R2) <− 0.
01−0.11 <f / SK <0.11NA <0.1
The three conditions must be satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light beam emitting lens system and an optical scanning device using the same, and more particularly, to a rotating polygon mirror which converts a light beam (light beam) which has been light-modulated and emitted from a light source means via a biconvex single lens. After the light is deflected and reflected by an optical deflector comprising a scanning lens system (fθ lens) having fθ characteristics, the surface to be scanned is optically scanned to record image information. It is suitable for devices such as laser beam printers and digital copiers.

[0002]

2. Description of the Related Art Conventionally, a laser beam printer (LB) has been used.
In an optical scanning device such as P), a divergent light beam (light beam) which is light-modulated and emitted from a light source means composed of, for example, a semiconductor laser is converted into a substantially parallel light beam by a collimator lens in accordance with an image signal. An aperture (aperture) disposed in the vicinity restricts the light amount to a predetermined value with a predetermined beam width, and makes the light amount enter a cylindrical lens. Then, of the substantially parallel light beams incident on the cylindrical lens, the light beams are emitted as they are in the state of substantially parallel light beams in the main scanning section. In the sub-scan section, the light converges and forms a substantially linear image on the deflection surface of the optical deflector composed of a polygon mirror. A light flux based on the image information deflected and reflected by the deflecting surface of the optical deflector is guided through a scanning lens system (fθ lens) having fθ characteristics onto a photosensitive drum surface as a surface to be scanned. Is rotated in a predetermined direction, thereby optically scanning the photosensitive drum surface in the main scanning direction at a substantially constant speed linear motion to record image information.

A light beam emission lens system used in this type of optical scanning apparatus uses a semiconductor laser as a light source, converts a divergent light beam emitted from the semiconductor laser into a substantially parallel light beam by a collimator lens, and converts the divergent light beam into a substantially parallel light beam. Light is emitted with a predetermined beam width and a predetermined amount of light by an aperture disposed in the vicinity.

Such a light beam emitting lens system is disclosed in, for example, Japanese Patent Application Laid-Open No. 60-112412 and Japanese Patent Application Laid-Open No. 7-174.
Various proposals have been made in, for example, Japanese Patent Publication No. 997. JP-A-60-
Japanese Patent Publication No. 121412 discloses an aspherical collimator lens using a biconvex single lens having an aspheric exit surface. Japanese Patent Application Laid-Open No. 7-174997 discloses a collimating lens using a plano-convex single lens whose exit surface is a convex spherical surface.

[0005]

However, when the light beam exit lens system is composed of a plano-convex single lens having a convex spherical surface, the light beam exit lens system is required to have a predetermined positive refractive power. There is a problem that the radius of curvature of the convex single lens becomes too large, and mass processing cannot be performed in lens manufacturing, particularly in a polishing step. In the case of manufacturing by molding, there is also a molding problem that it is difficult to accurately form a flat surface.

When the light beam exit lens system is composed of an aspherical biconvex single lens, the material of the biconvex single lens must be glass in consideration of environmental stability. There is a problem that it is more difficult to manufacture a lens easily than to manufacture a spherical lens.

A first object of the present invention is to provide a light beam exit lens system having a simple configuration with less aberration by appropriately configuring a light beam exit lens system having a biconvex single lens having a spherical surface.

A second object of the present invention is to provide a small-sized optical scanning device capable of performing high-definition optical scanning by using the above-mentioned light beam emitting lens system in an optical scanning device.

[0009]

According to the present invention, there is provided a light beam emitting lens system for: (1) a light beam emitting lens system for converting a state of a light beam emitted from a light source means into another state by a biconvex single lens. The focal length of the biconvex single lens is f, the radii of curvature of the entrance and exit lens surfaces of the biconvex single lens are R1 and R2, respectively, and the biconvex single lens exits from the lens surface on the optical axis of the exit side of the biconvex single lens. Assuming that the distance of the light beam to the imaging point is SK and the numerical aperture of the light beam exit lens system is NA, -0.09 <(R1 + R2) / (R1 * R2) <-0.
It is characterized by satisfying the following condition: 01−0.11 <f / SK <0.11 NA <0.13

In particular, (1-1) when the refractive index of the material of the biconvex single lens is n, the condition that 1.59 <n <1.85 is satisfied.

According to the present invention, there is provided an optical scanning device comprising:
(1-1) using the light beam emission lens system according to any one of (1) to (3), a light beam emitted from the light beam emission lens system is a line elongated in the main scanning direction on a deflection surface of a deflection unit via a cylindrical lens. When the light beam deflected and reflected by the deflecting means is formed into a spot on a surface to be scanned via a scanning lens system and the light beam is scanned on the surface to be scanned, the light beam is emitted. When the distance between the lens surface on the optical axis of the exit side of the lens system on the optical axis and the deflecting surface of the deflecting means is CP, and the distance between the deflecting surface of the deflecting means and the surface to be scanned is PD, -0.05 < It is characterized by satisfying the condition of (CP + PD) / SK <0.90.

(3) The main scanning of the light beam emitted from the light beam emitting lens system for converting the state of the light beam emitted from the light source means to another state by a biconvex single lens through the cylindrical lens on the deflection surface of the deflection means. Image in the form of a long line in the direction, the light beam deflected and reflected by the deflecting means is imaged in the form of a spot on the surface to be scanned via a scanning lens system,
In an optical scanning device that optically scans the surface to be scanned, the focal length of the biconvex single lens is f, and the radii of curvature of the entrance and exit lens surfaces of the biconvex single lens are R1 and R2, respectively. The distance from the lens surface on the optical axis on the exit side of the convex single lens to the imaging point of the emitted light beam is SK, the numerical aperture of the light beam exit lens system is NA, and the refractive index of the material of the biconvex single lens is n. Where CP is the distance between the lens surface on the optical axis on the exit side of the biconvex single lens and the deflecting surface of the deflecting means, and PD is the distance between the deflecting surface of the deflecting means and the surface to be scanned. 0.09 <(R1 + R2) / (R1 × R2) <− 0.
01-0.11 <f / SK <0.11 NA <0.13 1.59 <n <1.85-0.05 <(CP + PD) / SK <0.90 I have.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view of a main portion of a first embodiment when a light beam emitting lens system according to the present invention is used in an optical scanning device, and is developed in the optical axis direction of a main scanning section. ing. FIG. 2 is a schematic view of a main part showing the periphery of the light beam exit lens system shown in FIG.

In FIG. 1, reference numeral 1 denotes a light source means, which is composed of, for example, a semiconductor laser. Reference numeral 2 denotes a cover glass, and reference numeral 3 denotes an aperture (aperture stop) for limiting a passing light beam (light beam) to a predetermined light amount with a predetermined beam width. Reference numeral 4 denotes a biconvex single lens whose both lens surfaces are convex and spherical, and converts a divergent light beam emitted from the light source means 1 into a convergent light beam or a substantially parallel light beam. Reference numeral 4a denotes an entrance-side lens surface (incident surface) of the biconvex single lens 4, and 4b denotes an exit-side lens surface (exit surface) of the biconvex single lens 4.

Each element of the light source means 1, the cover glass 2, the aperture 3, and the biconvex single lens 4 constitutes one element of the light beam emission lens system 101.

Reference numeral 5 denotes a cylindrical lens which has a predetermined refracting power in the sub-scanning direction, and converts a light beam passing through the light beam exit lens system 101 into a vicinity of a deflecting surface of an optical deflector to be described later in a sub-scanning section. The image is formed almost as a line image. 6
Reference numeral denotes an optical deflector as a deflecting means, which is, for example, a rotating polygon mirror (polygon mirror), and is rotated at a constant speed in a predetermined direction by a driving means (not shown) such as a motor. Reference numeral 6a denotes a deflecting surface (polygon reflecting surface) of the optical deflector 6. Reference numeral 201 denotes a scanning lens system which includes a single scanning lens (fθ lens) 7 having fθ characteristics, and an optical deflector 6
The light flux based on the image information deflected and reflected by the deflecting surface 6a is formed into a spot image on the photosensitive drum surface 8 as the surface to be scanned, and the tilt of the deflecting surface 6a of the optical deflector 6 is corrected. .

In this embodiment, the divergent light beam emitted from the semiconductor laser 1 is limited to a predetermined light amount with a predetermined beam width by the aperture 3, and is converted into a substantially parallel light beam (or convergent light beam) by the biconvex single lens 4. The light enters the cylindrical lens 5. The luminous flux incident on the cylindrical lens 5 is emitted as it is in the main scanning section. In the sub-scan section, the light converges and is formed on the deflection surface 6a of the optical deflector 6 as a substantially linear image (a linear image elongated in the main scanning direction). The light beam deflected and reflected by the deflecting surface 6a of the optical deflector 6 is guided to the photosensitive drum surface 8 via the scanning lens 7, and the optical deflector 6 is rotated in a predetermined direction, thereby causing the photosensitive drum surface to rotate. 8 is optically scanned in the main scanning direction at a substantially constant speed linear motion. Thus, an image is recorded on the photosensitive drum surface 8 as a recording medium.

The light beam exit lens system 101 in the present embodiment has the biconvex single lens 4 having a spherical surface as described above, the focal length of the biconvex single lens 4 is f, and the incident side of the biconvex single lens 4 is The curvature radii of the exit-side lens surfaces 4a and 4b are R1 and R2, respectively, and the distance from the lens surface 4b on the exit-side optical axis of the biconvex single lens 4 to the imaging point Q of the exit light beam is S.
K, where NA is the numerical aperture of the light beam exit lens system 101, −0.09 <(R1 + R2) / (R1 × R2) <− 0.01 (1) −0.11 <f / SK < 0.11 ‥ (2) NA <0.13 ‥ (3)

Assuming that the refractive index of the material of the biconvex single lens 4 is n, the condition 1.59 <n <1.85８５ (4) is satisfied.

Further, the distance between the lens surface 4b on the optical axis on the exit side of the biconvex single lens 4 and the deflection surface 6a of the optical deflector 6 is CP,
The distance between the deflecting surface 6a of the optical deflector 6 and the surface 8 to be scanned is PD
In this case, the condition of -0.05 <(CP + PD) / SK <0.90 (5) is satisfied.

In this embodiment, the lens of the light beam exit lens system 101 is constituted by a biconvex single lens 4 having a spherical surface, so that a predetermined positive refracting power is provided by two lenses as compared with a conventional plano-convex single lens. Since the surfaces are shared, the radius of curvature R of the spherical surface can be reduced, and a large amount of processing can be performed in lens manufacturing, particularly in the polishing step, and the lens can be easily manufactured. In addition, since the spherical surface has a biconvex shape, good surface accuracy can be obtained even in molding.

Next, the technical meaning of each conditional expression of the present invention will be described.

Conditional expression (1) relates to the shape of the biconvex single lens 4. If the lower limit of conditional expression (1) is exceeded, the radius of curvature R1 of the entrance surface 4a of the biconvex single lens 4 becomes extremely loose, the radius of curvature R2 of the exit surface 4b becomes tight, and a large amount of the exit surface 4b is processed in the polishing step. Is difficult and the cost is high. It is more desirable to set the lower limit of conditional expression (1) to -0.08.

Regarding the upper limit of conditional expression (1), when the value of conditional expression (1) is 0, R1 = −R2,
When it is a so-called symmetric lens, and when the value is 0 near the symmetric lens, it is difficult to discriminate between the entrance surface 4a and the exit surface 4b of the biconvex single lens 4, a strict check step is required in assembling work, and lens management Costs are high. Therefore, the upper limit is-
It is not good to approach 0 from 0.01.

Further, in a plane perpendicular to the optical axis of the biconvex single lens 4, for example, when there are a plurality of light sources which are arranged so as to be shifted from the optical axis of the biconvex single lens 4, or due to a manufacturing error or the like, In a plane perpendicular to the optical axis of the biconvex single lens 4, coma occurs when the relative position between the optical axis of the biconvex single lens 4 and the light source is displaced. Exceeds the upper limit of the light source means 1
If the convex shape is sharp on the side, the coma aberration becomes large, which is not good.

The light beam exit lens system 1 of the present embodiment
In condition 01, since a light beam close to a substantially parallel light beam is emitted as in conditional expression (2), it is better to have a stronger convergence effect on the exit surface 4b to satisfactorily correct spherical aberration. When the convergence of the exit surface 4b is weakened by approaching the symmetric lens beyond the upper limit of the above, it is difficult to satisfactorily correct the spherical aberration, which is not good. In order to discriminate between the entrance surface 4a and the exit surface 4b and to properly correct coma and spherical aberration, it is more desirable to set the upper limit of conditional expression (1) to -0.0.
It is good to set to 2.

That is, it is preferable to set the numerical range of the conditional expression (1) as follows: -0.08 <(R1 + R2) / (R1 × R2) <-0.02 (1a)

Conditional expression (2) satisfies the light beam exit lens system 10
1. The degree of convergence of the light beam emitted by 1
Is expressed in comparison with the focal length f. 1 when a substantially parallel light beam is emitted from the light beam emission lens system 101
/ SK = 0 and f / SK = 0. When a divergent light beam is emitted, SK <0, and f / SK becomes a negative value. When a convergent light beam is emitted, SK> 0 and f /
SK has a positive value.

The light beam exit lens system 101 emits a light beam having a degree of convergence within the range from the lower limit (-0.11) to the upper limit (0.11) of the conditional expression (2). When f / SK = 0 when another optical system is combined with the exit side of the light beam exit lens system 101 to form another apparatus, the other error due to the position error of the other optical system in the optical axis direction. The focus position of the entire device does not change. However, if the lower limit value or the upper limit value of the conditional expression (2) is exceeded, a change in the focus position of the other apparatus as a whole due to a position error of the other optical system in the optical axis direction is undesirably large.

Conditional expression (3) satisfies the light beam exit lens system 10
It relates to a numerical aperture NA of 1. If the numerical aperture NA increases beyond the upper limit of conditional expression (3), spherical aberration increases. To correct this, it is necessary to configure a plurality of lens systems or introduce an aspherical surface. This is not good because a light beam emission lens system having a simple configuration cannot be obtained. More preferably, setting the upper limit of conditional expression (3) to 0.10 not only reduces the spherical aberration but also reduces the change in aberration due to manufacturing errors. Further, when the numerical aperture NA is reduced, the amount of emitted light decreases and the distance between the light source means 1 and the biconvex single lens 4 increases, so that it is more desirable to set the lower limit of conditional expression (3) to 0.0.
It is good to set so that it does not exceed 4.

That is, the numerical range of the conditional expression (3) is preferably set as follows: 0.04 <NA <0.10 (3a).

Condition (4) relates to the refractive index of the material of the biconvex single lens 4. If the refractive index of the material is lower than the lower limit value of the conditional expression (4), the radius of curvature of the lens surface for giving the biconvex single lens 4 a predetermined refractive power becomes tight, and the spherical aberration deteriorates. This is not good because the radius of curvature of the surface is too tight, and mass processing is difficult in the polishing process, which increases the cost. If the refractive index of the material becomes higher than the upper limit value of the conditional expression (4), the lens material becomes expensive, and it becomes impossible to obtain a light beam emission lens system having a simple configuration, which is not good.

Conditional expression (5) represents the distance CP between the exit surface 4b on the optical axis of the biconvex single lens 4 and the deflection surface 6a of the optical deflector 6, and
The relationship between the distance PD between the exit surface 4b on the optical axis of the biconvex single lens 4 and the imaging point Q of the exit light beam with respect to the distance PD between the deflection surface 6a and the surface 8 to be scanned is shown. .

The distance PD between the deflecting surface 6a and the surface 8 to be scanned is one of numerical values specifically representing the size of the entire apparatus.
As a method of reducing the interval PD, it is conceivable to increase the degree of convergence of the light beam emitted from the light beam emission lens system 101, that is, increase 1 / SK. This principle will be described with reference to FIGS. FIG.
3A and 3B are schematic diagrams (schematic diagrams) of main parts when developed in the optical axis direction of the main scanning section. FIG. 3A shows that a substantially parallel light beam is emitted from the light beam emission lens system 102 (1 / S
3B shows a case where a convergent light beam is emitted from the light beam exit lens system 103 (1 / SK> 0). 3A and 3B, FIG.
The same elements as those shown in FIG.

In FIGS. 3A and 3B, reference numerals 17 and 27 denote scanning lenses, respectively. Note that the focal length of the scanning lens 27 is Sf. L is the distance from the exit surface (14b, 24b) on the optical axis of the biconvex single lens (14, 24) to the scanning lens (17, 27), SD
A and SDB are the distances from the scanning lens (17, 27) to the surface 8 to be scanned.

As is clear from FIGS. 3A and 3B, the distances SDA and SDB satisfy SDA> SDB, and the convergence of the light beam of the light beam exit lens system is increased, that is, 1 / SK.
The size of the entire apparatus can be reduced by increasing. Further, as shown in FIG.
/ SK> 0 even when a convergent light beam is emitted.
7 with Sf 'longer than Sf, SDB = SD
Since it is also possible to set A, the refracting power of the scanning lens can be weakened by increasing the degree of convergence of the light beam of the light beam exit lens system, that is, by increasing 1 / SK. Therefore, the scanning lens can be manufactured with a small thickness, leaving a minimum edge thickness, and easily and accurately.

If the lower limit value of conditional expression (5) is exceeded, the degree of convergence of the light beam of the light beam exit lens system 101 will decrease, making it difficult to reduce the size of the entire apparatus, or increasing the refractive power of the scanning lens 7. It is necessary to increase the thickness while leaving the edge thickness, which makes it difficult to manufacture the scanning lens 7 accurately and simply, which is not good. More preferably, a convergent light beam is emitted from the light beam emission lens system 101, and the lower limit value of conditional expression (5) is preferably set to 0.10.

On the other hand, if the convergence of the light beam of the light beam exit lens system 101 becomes too high beyond the upper limit value of the conditional expression (5), the light spot on the surface 8 to be scanned 8 due to the position error of the light deflector 6. Is not good because the deviation of the imaging position becomes large, and high-definition optical scanning becomes impossible. It is more desirable to set the upper limit of conditional expression (5) to 0.80.

That is, the numerical range of the conditional expression (5) may be set as follows: 0.10 <(CP + PD) / SK <0.80 (5a)

Although the scanning lens system in this embodiment is constituted by a single lens, it may be constituted by a plurality of lenses.

Next, Numerical Examples 1 to 3 of the present invention will be described. 4 to 6 are spherical aberration diagrams of Numerical Examples 1 to 3 of the present invention, respectively. Table 1 shows the relationship between the above-described conditional expressions and various numerical values in the numerical examples.

In the numerical examples 1-3, the light source wavelength λ = 780 nm, the thickness of the cover glass = 0.25 mm, the refractive index of the cover glass = 1.50875 d1 = the distance from the light source to the aperture d2 = the biconvex from the aperture Distance d3 from the entrance surface on the optical axis of the single-lens single lens to the exit surface SK = Distance from the exit surface on the optical axis of the single-convex single lens to the image point Distance n = refractive index of biconvex single lens R1 = radius of curvature of entrance surface of biconvex single lens R2 = radius of curvature of exit surface of biconvex single lens NA = numerical aperture of light beam exit lens system CP = biconvex single lens S1 = Distance from front principal point H of scanning lens to deflection surface HH ′ = Distance from front principal point H of scanning lens to rear principal point H ′ on optical axis S2 = Is the back principal point H 'of the scanning lens The focal length PD = -S1 + HH '+ S2 in the main scanning direction distance W = effective scanning width Sf = scanning lens to the scanned surface.

Numerical Example 1 d1 = 24.727 SK = 421.5 d2 = 0.500 CP = 75.1 d3 = 2.000 S1 = −35.7 R1 = 182.212 HH ′ = 4.8 R2 = -2.831 S2 = 133.4 W = 206.0 Sf = 239.8 Numerical Example 2 d1 = 33.459 SK = 1352.2 d2 = 0.800 CP = 110.2 d3 = 2.000 S1 = -45.2 R1 = 178.475 HH '= 7.7 R2 =-30.430 S2 = 204.7 W = 310.0 Sf = 251.1 Numerical Example 3 d1 = 14.388 SK = 287. 7 d2 = 0.300 CP = 38.5 d3 = 2.000 S1 = -7.4 R1 = 182.212 HH '= 3.9 R2 = -12.404 S2 = 131.2 W = 06.0 Sf = 304.8

[0044]

[Table 1]

[0045]

According to the first aspect of the present invention, by appropriately configuring the light beam exit lens system having the biconvex single lens having a spherical surface as described above, a light beam exit lens system having a simple configuration with less aberration is provided. Can be achieved.

According to the second aspect of the present invention, as described above, by using the above-mentioned light beam emission lens system for an optical scanning device, it is possible to achieve an optical scanning device capable of performing a small and high-definition optical scanning. .

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a main part of a first embodiment when a light beam exit lens system according to the present invention is used in an optical scanning device.

FIG. 2 is a schematic diagram of a main part showing a periphery of a light beam exit lens system of FIG. 1;

FIG. 3 is a schematic diagram of a main part when the first embodiment of the present invention is developed in the optical axis direction of a main scanning section.

FIG. 4 is a spherical aberration diagram according to Numerical Example 1 of the present invention.

FIG. 5 is a spherical aberration diagram according to Numerical Example 2 of the present invention.

FIG. 6 is a spherical aberration diagram according to Numerical Example 3 of the present invention.

[Explanation of symbols]

 Reference Signs List 1 light source means 2 cover glass 3 aperture 4 biconvex single lens 4a entrance surface 4b emission surface 5 cylindrical lens 6 deflection means (optical deflector) 6a deflection surface 7 scanning lens 8 scanned surface 101 light beam emission lens system 201 scanning lens system

Claims (4)

[Claims] 1. A light beam emission lens system for converting the state of a light beam emitted from a light source means into another state by a biconvex single lens, wherein the focal length of the biconvex single lens is f, and the incidence of the biconvex single lens is The radii of curvature of the lens surfaces on the exit side and the exit side are R1 and R2 respectively, the distance from the lens surface on the optical axis on the exit side of the biconvex single lens to the imaging point of the exit light beam is SK, and the light beam exit lens system Where NA is the numerical aperture of −0.09 <(R1 + R2) / (R1 × R2) <− 0.
A light beam exit lens system satisfying the following condition: 01-0.11 <f / SK <0.11 NA <0.13 2. The light beam exit lens system according to claim 1, wherein a condition of 1.59 <n <1.85 is satisfied, where n is a refractive index of a material of the biconvex single lens. 3. A light beam emitted from the light beam emission lens system according to claim 1, wherein a light beam emitted from the light beam emission lens system is main-scanned on a deflection surface of a deflection unit via a cylindrical lens. When a light beam deflected and reflected by the deflecting means is formed as a spot on a surface to be scanned through a scanning lens system to optically scan the surface to be scanned. When the distance between the lens surface on the optical axis on the exit side of the light beam exit lens system and the deflecting surface of the deflecting means is CP, and the distance between the deflecting surface of the deflecting means and the surface to be scanned is PD, An optical scanning device which satisfies a condition of -0.05 <(CP + PD) / SK <0.90. 4. A light beam emitted from a light beam emitting lens system for converting a state of a light beam emitted from a light source means to another state by a biconvex single lens through a cylindrical lens on a deflection surface of a deflection means in a main scanning direction. Optical scanning for forming a linear image on the surface to be scanned, forming a light beam deflected and reflected by the deflecting means into a spot on the surface to be scanned through a scanning lens system, and optically scanning the surface to be scanned. In the apparatus, the focal length of the biconvex single lens is f, the radii of curvature of the entrance and exit lens surfaces of the biconvex single lens are R1 and R2, respectively, on the optical axis of the exit side of the biconvex single lens. The distance from the lens surface to the imaging point of the emitted light beam is SK, the numerical aperture of the light beam exit lens system is NA, the refractive index of the material of the biconvex single lens is n, and the light on the exit side of the biconvex single lens is The distance between the lens surface on the axis and the deflection surface of the deflection means is CP, When the distance between the deflecting surface and the scanned surface of the deflecting means and the PD, -0.09 <(R1 + R2) / (R1 × R2) <- 0.
01−0.11 <f / SK <0.11 NA <0.13 1.59 <n <1.85−0.05 <(CP + PD) / SK <0.90 Optical scanning device.