JPH11109269A - Multibeam scanning optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multibeam scanning optical device almost uniformizing the distribution of a light quantity on a surface to be scanned and obtaining an image with high quality. SOLUTION: In this optical device, plural light beams transmitted from a light source means 2 having plural light emitting parts are introduced to a deflecting means 4, plural light beams deflected/reflected by the deflecting means are introduced to a surface to be scanned 6 through an image forming optical system 5 and the surface to be scanned 6 is simultaneously scanned with the plural light beams. In this case, a light quantity adjusting means 1 having the spectral transmissivity characteristic of P polarization, in which transmissivity in a wavelength shorter than the wavelength of the light source is higher than that of the wavelength of light source and transmissivity in a wavelength longer than the wavelength of the light source is lower than that, is provided in an optical path between the light source means 2 and the surface to be scanned 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-beam scanning optical device, and more particularly to providing a light amount adjusting means in an optical path or on each deflecting surface of an optical deflector so that a light amount distribution on a surface to be scanned is substantially constant. The present invention relates to a multi-beam scanning optical device which can obtain a high-quality image and is suitable for a device such as a laser beam printer (LBP) or a digital copying machine having an electrophotographic process.

[0002]

2. Description of the Related Art Conventionally, in a multi-beam scanning optical device such as a laser beam printer or the like, a plurality of light beams emitted from a light source means (multi-laser) having a plurality of light-emitting portions are modulated by, for example, a rotating polygon mirror (polygon mirror). )
The light is deflected periodically by an optical deflector composed of an optical deflector and converged in the form of a spot on a photosensitive recording medium (photosensitive drum) surface by an imaging optical system (fθ lens system) having fθ characteristics. Image recording is performed by light scanning simultaneously with a light beam.

FIG. 6 is a schematic view of a main part of a conventional multi-beam optical scanning optical device. In the figure, a plurality of light beams emitted from the multi-laser (light source means) 62 after being modulated are converted into substantially parallel light beams by a collimator lens constituting one element of the condensing optical system 63, and are predetermined only within the sub-scan section. Incident on a cylindrical lens which also constitutes one element of the condensing optical system 63 having the refractive power of Of the plurality of 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 is converged and formed as a substantially linear image on the deflecting surface 64a of the optical deflector 64 composed of a polygon mirror. The imaging optical system having different power reflection angle by the deflecting surface 64a of the optical deflector 64 a plurality of light beams deflected reflected in the range of (= incident angle) theta ₁ through? ₂ in the main scanning direction and the subscanning direction (Fθ lens) 65 to guide the light onto a photosensitive drum surface 66 as a surface to be scanned, and rotate the optical deflector 64 in the direction of arrow A, thereby forming the photosensitive drum surface 6.
The image information is recorded by simultaneously performing optical scanning on arrow 6 in the direction of arrow B (main scanning direction) with a plurality of light beams. Although the figure shows two light beams from the multi laser 62, only one light beam is shown in FIG.

In FIG. 1, P ₀ is an axial image point, P ₁ ,
P ₂ is an off-axis image point, and O is a deflection point (reflection point) O on the deflection surface of the optical deflector. The plane formed by the straight lines OP ₁ and OP ₂ is referred to as a scanning plane or a main scanning plane, and a plane perpendicular thereto is referred to as a sub-scanning plane.

FIG. 7 is an enlarged explanatory view of the multi-laser shown in FIG. The multi-laser 62 in the figure has a so-called active layer 23 manufactured by a semiconductor process between the upper and lower substrate materials 21 and 22 as shown in the figure, for example, as disclosed in Japanese Patent Publication No. 60-33019. The active layer 23 has two light emitting points 24 and 25. The multi-laser 62 is arranged such that a straight line connecting the two light-emitting points 24 and 25 is inclined by a small angle ε with respect to the main scanning plane.

In addition, this type of multi-beam scanning optical device has the following features: (a) an optical path between a polygon mirror and an fθ lens;
(B) Alternatively, a flat glass (not shown) is provided in the optical path between the fθ lens and the photosensitive drum surface.
(A) Prevention of dust and dust from entering the polygon mirror, or preventing noise from the drive system of the polygon mirror from leaking into the surroundings, and (b) preventing dust and dust from entering the fθ lens. ing. In this case, both surfaces of the flat glass are coated with an anti-reflection coating to prevent loss of light amount, flare light, ghost and the like.

[0007]

The above-mentioned conventional multi-beam scanning optical device has the following problems.

Since the plane of polarization (oscillation plane of polarized light) of the light beam is parallel to the active layer, the plane of polarization is inclined by a small angle ε with respect to the main scanning plane as shown by arrow C in FIG. ing. However, since the small angle ε is small, the polarization state of the plurality of light beams when entering the fθ lens is almost P-polarized. The transmittance of the P-polarized light increases from the incident angle of 0 ° to the Brewster angle (about 55 ° to 60 °) due to Fresnel reflection, so that the off-axis image point P ₁ (and the axial image point P ₀₎ The light amount at the outer image point P ₂ ) tends to increase.

If the fθ lens is formed of a glass lens, it is possible to reduce the reflectance by applying an antireflection coating. However, if the fθ lens is formed of a plastic lens, it is difficult to apply a coating. The off-axis light amount tends to increase.

Since the fθ lens has a positive power in the main scanning plane, the edge at the peripheral portion is shorter than that at the center of the lens, that is, the off-axis optical path is shorter than the on-axis optical path in the fθ lens. The internal absorption of the fθ lens is smaller off-axis,
Again, the off-axis light amount on the surface to be scanned tends to increase.

For example, when the scanning angle (2θ ₂ -2θ ₁ ) is 60 °
In this case, the off-axis light amount is a ratio (off-axis / on-axis) compared to the on-axis light amount due to the Fresnel reflection and the internal absorption of the fθ lens.
T ′ = 1.05 to 1.15.

According to the present invention, light amount adjusting means having appropriate spectral transmittance characteristics or spectral reflectance characteristics is provided in the optical path or on each deflecting surface of the optical deflector so that the light amount distribution on the surface to be scanned is substantially uniform. With such a configuration, it is an object of the present invention to provide a multi-beam scanning optical device capable of easily obtaining a high-quality image.

[0013]

According to the present invention, there is provided a multi-beam scanning optical apparatus comprising: (1) guiding a plurality of light beams emitted from a light source having a plurality of light-emitting portions to a deflecting means, and deflecting the plurality of light beams by the deflecting means; A multi-laser scanning optical apparatus that guides a plurality of reflected light beams onto a surface to be scanned through an imaging optical system and simultaneously scans the surface to be scanned with a plurality of light beams. In the optical path between the light source and the surface to be scanned, the spectral transmittance characteristic of P-polarized light is such that the transmittance at the wavelength of the light source is higher at the wavelength shorter than the wavelength of the light source, and the transmittance is lower at the longer wavelength. It is characterized in that light amount adjusting means having the same is provided.

In particular, (1-1) the spectral transmittance characteristic of the P-polarized light of the light amount adjusting means is such that the transmittance with respect to the light source wavelength is lower in the off-axis beam than in the on-axis beam; The adjusting means is formed by applying an optical multilayer film on the substrate member, or (1-3) that the light amount adjusting means is attached to the frame so that the outer periphery thereof is in close contact, and the like. Features.

(2) A plurality of light beams emitted from the light source means having a plurality of light emitting portions are guided to the deflecting means, and the plurality of light beams deflected and reflected by the deflecting means are received via the imaging optical system. In a multi-beam scanning optical device that guides light on a scanning surface and simultaneously scans the surface to be scanned with a plurality of light beams, each of the deflecting surfaces of the deflecting means has a spectral reflectance characteristic of P-polarized light at a light source wavelength. It is characterized in that light amount adjusting means having a characteristic that the reflectance at wavelengths before and after the light source wavelength is lower than the reflectance is provided.

(2-1) The spectral transmittance characteristic of the P-polarized light of the light amount adjusting means is such that the reflectance with respect to the wavelength of the light source is lower in the off-axis beam than in the on-axis beam; The means is characterized in that an optical multilayer film is formed on the deflection surface of the deflection means.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view of a main part of a first embodiment of the present invention.

In FIG. 1, reference numeral 2 denotes a light source means (multi-laser) having a plurality of light-emitting portions, which is manufactured by a semiconductor process between upper and lower substrate members 21 and 22 as shown in FIG. In this active layer 23, there are two light emitting points 24 and 25.
The multi-laser 2 is arranged such that a straight line connecting the two light-emitting points 24 and 25 is inclined by a small angle ε with respect to the main scanning plane.

Reference numeral 3 denotes a condensing optical system, which has a collimator lens for converting a plurality of light beams (light beams) emitted from the light source means 2 into substantially parallel light beams, and has a predetermined refractive power only in the sub-scan section. And a cylindrical lens. The cylindrical lens forms a plurality of light beams, which have passed through the collimator lens, as substantially linear images on a deflecting surface 4a of an optical deflector 4 described later in a sub-scanning cross section.

Reference numeral 4 denotes an optical deflector as a deflecting means, which is constituted by, for example, a rotating polygon mirror (polygon mirror), and is rotated at a constant speed in the direction of arrow A by a driving means (not shown) such as a motor.

Reference numeral 1 denotes an optical filter as light amount adjusting means, which is disposed in an optical path between the light deflector 4 and the photosensitive drum surface 6, and has an optical multilayer film formed on a substrate member (flat glass). It is formed. In this optical filter 1, the spectral transmittance characteristic of P-polarized light is higher at a light source wavelength (wavelength of a light beam emitted from the light source means 2) at a light source wavelength (wavelength of a light beam emitted from the light source means 2). Is set so that the transmittance becomes low. This optical filter 1
Is different between the on-axis beam and the off-axis beam, the spectral transmittance distribution of the optical filter 1 is different between the on-axis beam and the off-axis beam. In this embodiment, as described later, the transmittance of a light source for a single wavelength is set lower for an off-axis beam than for an on-axis beam. The optical filter 1 is attached to a frame (not shown) so that its outer periphery is in close contact with the frame, and is used as a means for separating the space before and after the optical filter 1.

Reference numeral 5 denotes an image forming optical system, which comprises an fθ lens having fθ characteristics, and receives a light beam based on image information deflected and reflected by the deflecting surface 4a of the optical deflector 4 as a surface to be scanned (image surface). An image is formed on the drum surface 6. fθ
The lens 5 is formed from a single plastic lens (or glass lens). The photosensitive drum surface 6 is embodied by a known electrophotographic process.

P ₀ is an on-axis image point, P ₁ and P ₂ are off-axis image points, and O is a deflection point (reflection point) on the deflection surface of the optical deflector. The surface formed by the straight lines OP ₁ and OP ₂ is a scanning surface,
Alternatively, the main scanning plane, and a plane perpendicular thereto is referred to as a sub-scanning plane.

In the present embodiment, a plurality of light beams (light beams) emitted from the light source means (multi-laser) 2 after being modulated.
Is converted into a substantially parallel light beam by a collimator lens constituting one element of the condensing optical system 3, and is converted into a cylindrical lens having a predetermined refractive power only in the sub-scanning cross section constituting one element of the condensing optical system 3. It is incident. Of the plurality of 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 is converged and formed as an almost linear image on the deflection surface 4a of the optical deflector 4. And the optical deflector 4
A plurality of light beams deflected and reflected by the deflecting surface 4a in the range of the reflection angle (= incident angle) θ _{1 to} θ ₂ pass through the optical filter 1,
Light is guided onto a photosensitive drum surface 6 as a surface to be scanned through an imaging optical system (fθ lens) 5 having different powers in the main scanning direction and the sub-scanning direction, and the optical deflector 4 is moved in the direction of arrow A. By rotating, the photosensitive drum surface 6 is simultaneously optically scanned in the direction of arrow B (main scanning direction) with a plurality of light beams to record image information. Although the figure shows two light beams from the multi-laser 2, only one light beam is shown in FIG.

The multi-laser 2 has a so-called active layer 23 manufactured by a semiconductor process between the upper and lower substrate members 21 and 22 as described above.
4 and 25, and are arranged such that a straight line connecting the two light emitting points 24 and 25 is inclined by a small angle ε with respect to the main scanning plane. For this reason, the polarization plane of the light beam (polarization vibration plane)
Is almost parallel to the main scanning plane (strictly, inclined by a small angle ε) as shown by an arrow C in the figure, so that almost all of the light enters the optical filter 1 and the fθ lens 5 with P-polarized light. lens 5 has a higher off-axis transmittance than the on-axis transmittance as described above. The ratio of the off-axis transmittance to the on-axis (off-axis /
(On the axis) is defined as t ′ (> 1). The ratio t 'is about 1.05 to 1.15 as described above.

FIG. 2 is an explanatory diagram showing the spectral transmittance characteristics of the optical filter 1 according to this embodiment.

In the figure, T ₀ is an incident angle of P-polarized light of 0 °.
, T ₁ is the incident angle 2θ ₂ -2θ
It is a spectral transmittance characteristic with respect to ₀ (= 2θ ₀ -2θ ₁ ). The transmittance of P-polarized light at the light source wavelength lambda ₀ to be used is T ₀ At _{t 0, T 1 (= T} 2) in t ₁ (= t _2).

The axial beam O-P ₀ in Fig. 1 at an incident angle of 0 ° to the optical filter 1, the off-axis beam O-P ₁ at an incident angle 2θ ₀ -2θ _1, the off-axis beam O- P ₂ is incident at an incident angle of 2θ ₂ -2θ ₀ .

[0029] Thus P axial beam O-P ₀ of the polarized light passes through the optical filter 1 in the transmittance t ₀ from FIG. 2, the off-axis beam O-P _1, O-P ₂ respectively t ₁ of the P-polarized light, The light is transmitted at t ₂ , and as a result, the light amount of the off-axis beam is lower than that of the on-axis beam by t ₁ / t ₀ (= t ₂ / t ₀ ).

In this embodiment, each element is set so that t ₁ / t ₀ × t ′ ≒ 1 (= t ₂ / t ₀ × t ′ ≒ 1). As a result, the on-axis image point P ₀ and the off-axis image points P ₁ and P ₂ on the surface 6 to be scanned have substantially the same light amount, and the light amount distribution on the surface 6 to be scanned can be made substantially uniform.

Specifically, as an example of a multilayer film configuration of the optical filter 1, a glass + TiO ₂ (314 nm) + SiO ₂ (189 nm) + TiO _{2 is} formed on a glass substrate in this order from the glass substrate side.
₂ (314 nm) + SiO ₂ (189 nm) + TiO ₂ (314 nm) + S
By applying iO ₂ (57 nm) to both surfaces, for a light source wavelength of 780 nm, t ₀ = 0.983 (for an incident angle of 0 °) and t ₁ =
0.897 (for an incident angle of 30 °), and t ₁ / t ₀ = 0.92. At this time, the spectral transmittance characteristic λ ₀ = 780 nm
The dT / dλ (change rate) in the vicinity is −0.0 / nm per 10 nm.
02.

The optical filter 1 according to the present embodiment
Is attached to the frame body (not shown) in close contact with the frame as described above, thereby preventing invasion of dust and dirt into the polygon mirror 4 side. Furthermore, the driving sound of the polygon motor is contained.

The same effect as described above can be obtained even if the optical filter 1 is tilted by a small angle with respect to the optical axis in the sub-scanning plane in order to prevent return light to the multi-laser 2. Alternatively, the optical filter 1 may be extended closer to the polygon mirror 4 and extended to the rear side, and may be disposed across the optical path connecting the condensing optical system 3 and the polygon mirror 4. Thereby, the sealing performance can be further improved.

When a folding mirror, another filter, or the like is provided in the optical path, all of these optical elements are used as an image forming optical system (fθ lens) to calculate a light amount distribution on the surface to be scanned. What is necessary is just to set the spectral transmittance characteristic of the optical filter 1 so that the optical filter 1 cancels.

As described above, in this embodiment, as described above, in the optical path between the light deflector 4 and the surface 6 to be scanned, the spectral transmittance characteristic of P-polarized light is different from that of the light source at the wavelength of the light source. By providing the optical filter 1 having a high transmittance at a wavelength shorter than the wavelength and a low transmittance at a longer wavelength, the light amount distribution on the surface 6 to be scanned can be made substantially uniform. Easy to get.

FIG. 3 is a schematic view of a main part of a second embodiment of the present invention. In the figure, the same elements as those shown in FIG. 1 are denoted by the same reference numerals.

The present embodiment differs from the first embodiment in that an optical filter 11 is provided in the optical path between the fθ lens 5 and the surface 6 to be scanned, and the angle at which the off-axis beam enters the optical filter 11 is determined. This is set smaller than in the first embodiment. Other configurations and optical functions are substantially the same as those of the first embodiment, and thus the same effects are obtained.

That is, in the same figure, reference numeral 11 denotes an optical filter as a light amount adjusting means, which is disposed in the optical path between the fθ lens 5 and the surface 6 to be scanned. The spectral transmittance characteristic of is set so that the transmittance at a wavelength shorter than the light source wavelength is higher than the transmittance at the light source wavelength, and the transmittance is lower at a longer wavelength, and the transmittance of the light source at a single wavelength. Is set lower for the off-axis beam than for the on-axis beam.

In the first embodiment, the off-axis beam OP ₁
6 of the incident angle on the optical filter 1 but was 2θ ₀ -2θ _1, reduce the angle of incidence of the optical filter 11 from 2θ ₀ -2θ ₁ in this embodiment of the (2θ ₀ -2θ ₁
70%) (off-axis beam OP
₂ is the same. ). This is because the fθ lens 5 has a negative distortion. For this reason, dT / dλ (change rate) of the spectral transmittance characteristic of the optical filter 11 is set to be larger in absolute value than in the first embodiment.

Specifically, as an example of a multilayer film configuration of the optical filter 11, a glass + TiO ₂ (300 nm) + SiO ₂ (180 nm) + TiO ₂ is sequentially formed on a glass substrate from the glass substrate side.
₂ (300 nm) + SiO ₂ (180 nm) + TiO ₂ (300 nm) + S
By applying iO ₂ (180 nm) + TiO ₂ (300 nm) + SiO ₂ (54 nm) on both sides, the light source wavelength 780 nm
t ₀ = 0.904 (for an incident angle of 0 °), t ₁ = 0.
801 (for an incident angle of 20 °), and t ₁ / t ₀ = 0.89. At this time, the spectral transmittance characteristic λ ₀ = 780 nm
The dT / dλ (change rate) in the vicinity is −0.0 / nm per 10 nm.
08.

The optical filter 1 according to the present embodiment
As described above, reference numeral 1 is attached to the frame (not shown) so that its outer periphery is in close contact with the frame, thereby preventing invasion of dust and dirt into the fθ lens 5.

FIG. 4 is a schematic view of a main part of a third embodiment of the present invention. In the figure, the same elements as those shown in FIG. 1 are denoted by the same reference numerals.

In the figure, reference numeral 41 denotes light amount adjusting means.
An optical multilayer film is formed on each deflection surface of the optical deflector 40. The light amount limiting means 41 is set so that the spectral reflectance characteristic of the P-polarized light is lower at the wavelengths before and after the light source wavelength than at the light source wavelength.
Since the incident angle of the light beam incident on the light quantity adjusting means 41 differs between the on-axis beam and the off-axis beam, the spectral reflectance distribution of the light quantity adjusting means 41 differs between the on-axis beam and the off-axis beam. In the present embodiment, as will be described later, the reflectance of a light source for a single wavelength is set lower for an off-axis beam than for an on-axis beam.

FIG. 5 shows the light amount adjusting means 4 according to this embodiment.
FIG. 4 is an explanatory diagram showing a spectral reflectance characteristic of No. 1;

In the figure, R ₀ is the incident angle θ ₀ of P-polarized light.
, And R ₁ and R ₂ are spectral reflectance characteristics with respect to incident angles θ ₁ and θ ₂ of P-polarized light, respectively. The reflectance of P-polarized light at the light source wavelength lambda ₀ to be used in the R ₀ r _0,
R ₁ (R ₂ ) is r ₁ (r ₂ ). Note that r ₁ ≒ r ₂
It is.

Therefore, the P-polarized on-axis beam OP ₀ is reflected on the deflecting surface at a reflectance r ₀ as shown in FIG. 5, and the P-polarized off-axis beams OP ₁ and OP ₂ are r ₁ , respectively. reflected by the r _2,
As a result, the light quantity of the off-axis beam is lower than that of the on-axis beam by r ₁ / r ₀ (= r ₂ / r ₀ ).

In the present embodiment, each element is set so that r ₁ / r ₀ × t ′ ≒ 1 (= r ₂ / r ₀ × t ′ ≒ 1). Accordingly, the on-axis image point P ₀ and the off-axis image points P ₁ and P ₂ on the surface to be scanned have substantially the same light amount, and the light amount distribution on the surface to be scanned can be made substantially uniform.

As described above, in this embodiment, as described above, the spectral reflectance characteristic of the P-polarized light on each deflection surface of the optical deflector 4 is different from the reflectance at the light source wavelength by the wavelengths before and after the light source wavelength. By applying an optical multilayer film so that the reflectance of
It is possible to make the light amount distribution on the scanned surface 6 substantially uniform,
This makes it easy to obtain a high-quality image.

The light amount adjusting means used in the first or second embodiment may be combined with the light amount adjusting means used in the third embodiment.

In each embodiment, the multi-beam scanning optical device has been described. However, the present invention can be applied to a single-beam scanning optical device.

[0051]

According to the present invention, light amount adjusting means having appropriate spectral transmittance characteristics or spectral reflectance characteristics as described above is provided in the optical path or on each deflecting surface of the optical deflector, and the light amount adjusting means is provided on the surface to be scanned. By configuring the light quantity distribution to be substantially uniform, it is possible to achieve a multi-beam scanning optical device capable of obtaining a high-quality image.

Further, according to the present invention, the same effect as that of the conventional dustproof glass can be provided by supporting the optical filter disposed in the optical path to improve the sealing property, and the image quality can be improved with the same number of parts. In addition, it is possible to achieve a multi-beam scanning optical device that has improved durability due to hermeticity, is strong in measures against dust and dust, and can contribute to quality improvement.

[Brief description of the drawings]

FIG. 1 is a schematic view of a main part of a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a spectral transmittance characteristic of the optical filter according to the first embodiment of the present invention.

FIG. 3 is a schematic diagram of a main part of a second embodiment of the present invention.

FIG. 4 is a schematic diagram of a main part of a third embodiment of the present invention.

FIG. 5 is an explanatory diagram showing spectral reflectance characteristics of a deflecting surface of an optical deflector according to a third embodiment of the present invention.

FIG. 6 is a schematic view of a main part of a conventional multi-beam scanning optical device.

FIG. 7 is an enlarged explanatory view of a multi laser.

[Explanation of symbols]

 Reference Signs List 1, 1 Light amount adjusting means (optical filter) 2 Light source means (multi laser) 3 Condensing optical system 4, 40 Deflection means (optical deflector) 5 Imaging optical system (fθ lens system) 6 Scanned surface (photosensitive drum surface) 41) Light intensity adjusting means (optical multilayer film)

Claims (7)

[Claims] 1. A plurality of light beams emitted from a light source having a plurality of light emitting units are guided to a deflecting unit, and the plurality of light beams deflected and reflected by the deflecting unit are scanned by an imaging optical system. In a multi-laser scanning optical apparatus for guiding light on a surface and simultaneously scanning the surface to be scanned with a plurality of light beams, a spectral transmittance of P-polarized light is provided in an optical path between the light source means and the surface to be scanned. A multi-beam scanning optical device comprising a light amount adjusting means having characteristics such that the transmittance is high at a wavelength shorter than the light source wavelength and low at a long wavelength. . 2. The multi-beam scanning optical apparatus according to claim 1, wherein the spectral transmittance characteristic of the P-polarized light of the light amount adjusting means is such that the transmittance with respect to the light source wavelength is lower in an off-axis beam than in an on-axis beam. . 3. The multi-beam scanning optical device according to claim 1, wherein said light amount adjusting means is formed by applying an optical multilayer film on a substrate member. 4. The multi-beam scanning optical device according to claim 1, wherein said light amount adjusting means is attached to a frame so that its outer periphery is in close contact with said frame. 5. A plurality of light beams emitted from a light source having a plurality of light-emitting portions are guided to a deflecting means, and the plurality of light beams deflected and reflected by the deflecting means are scanned by an imaging optical system. In a multi-beam scanning optical device for guiding light on a surface and simultaneously scanning the surface to be scanned with a plurality of light beams, the spectral reflectance characteristic of P-polarized light at each light source wavelength is reflected at each deflection surface of the deflection means. A multi-beam scanning optical apparatus, comprising: a light amount adjusting unit having a characteristic that reflectance at wavelengths before and after the light source wavelength is lower than the reflectance. 6. The multi-beam scanning optical device according to claim 5, wherein the spectral transmittance characteristic of the P-polarized light of the light amount adjusting means is such that the reflectance with respect to the light source wavelength is lower in an off-axis beam than in an on-axis beam. . 7. The multi-beam scanning optical device according to claim 5, wherein said light amount adjusting means is formed by applying an optical multilayer film on a deflecting surface of said deflecting means.