JPS6410806B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image recording and display device using light sources arranged in an array, such as a semiconductor array laser, and particularly to a compact optical system including tilt correction.

2. Description of the Related Art Image recording and display devices using a single light source have been well known. FIG. 1 is a diagram showing one embodiment of the present invention, in which, for example, an emitted/divergent beam from a semiconductor laser 1 is collimated by a condenser lens 2 and made incident on one surface of a rotating polygon mirror 3. The reflected/deflected light from the rotating polygonal mirror is imaged and scanned onto a scanning surface 5 by an imaging lens 4 such as a θ lens. By modulating the semiconductor laser, a desired image can be obtained on the scanned surface.

By using an array of light sources in such a device, various advantages arise. Here, the array-shaped light source is, for example, semiconductor lasers 1a, 1b, 1c that can be driven and modulated independently, as shown in FIG.
It refers to a structure in which the are arranged in a row. The use of such an array light source has the following advantages compared to the case of using only one light source.

1. High speed because multiple scanning lines can be recorded and displayed simultaneously.

2. Therefore, the speed of rotating polygon mirrors, galvers, etc. may be slow.

3. Also, the power of the semiconductor laser may be low,
It is advantageous against deterioration.

For the above reasons, it is very effective to use an array light source.

However, when an array light source is used with a conventional optical system as it is, the following drawbacks occur.

FIG. 3 explains this, and the semiconductor laser 1 is made up of three arrays 1a, 1b, and 1c.

The beams emitted from each of the semiconductor lasers 1a, 1b, and 1c oscillate so as to have a maximum intensity distribution in the normal direction perpendicular to the end face thereof. Collimator lens 2
In the case of collimation, only the beam of the semiconductor laser 1b on the optical axis runs parallel to the optical axis, and the semiconductor lasers 1a and 1c located off the optical axis are collimated at a finite angle with the optical axis. The angle θ shown in this figure defines the focal length of the collimator lens as f
Letting the pitch of the light source array be θ=n/f (rad). (where n is the number of arrays) This invention relates to an image recording and display device using a semiconductor laser, and particularly to a compact optical system including tilt correction.

2. Description of the Related Art Image recording and display devices using a single light source have been well known. FIG. 1 is a diagram showing one embodiment of the present invention, in which, for example, an emitted/divergent beam from a semiconductor laser 1 is collimated by a condenser lens 2 and made incident on one surface of a rotating polygon mirror 3. The reflected/deflected light from the rotating polygonal mirror is imaged and scanned onto a scanning surface 5 by an imaging lens 4 such as a θ lens. By modulating the semiconductor laser, a desired image can be obtained on the scanned surface.

By using an array of light sources in such a device, various advantages arise. Here, the array-shaped light source is, for example, semiconductor lasers 1a, 1b, 1c that can be driven and modulated independently, as shown in FIG.
It refers to a structure in which the are arranged in a row. The use of such an array light source has the following advantages compared to the case of using only one light source.

1. High speed because multiple scanning lines can be recorded and displayed simultaneously.

2. Therefore, the speed of rotating polygon mirrors, galvers, etc. may be slow.

3. Also, the power of the semiconductor laser may be low,
It is advantageous against deterioration.

For the above reasons, it is very effective to use an array light source.

However, when an array light source is used with a conventional optical system as it is, the following drawbacks occur.

FIG. 3 explains this, and the semiconductor laser 1 is made up of three arrays 1a, 1b, and 1c.

The beams emitted from each of the semiconductor lasers 1a, 1b, and 1c oscillate so as to have a maximum intensity distribution in the normal direction perpendicular to the end face thereof. Collimator lens 2
In the case of collimation, only the beam of the semiconductor laser 1b on the optical axis runs parallel to the optical axis, and the semiconductor lasers 1a and 1c located off the optical axis are collimated at a finite angle with the optical axis. The angle θ shown in this figure defines the focal length of the collimator lens as f
Letting the pitch of the light source array be θ=nl/f (rad). (where n is the number of arrays) When semiconductor lasers are arrayed, it is said that the limit is about 0.1 mm due to heat dissipation, manufacturing technology, etc., and it is difficult to make the size smaller than this. If the focal length of the collimator lens is f=10 mm and the number of arrays is n=8, then θ=8×0.1/10=0.08 (rad) (=4.6°). Here, the focal position θ of the collimator lens
If the distance to the rotating polygon mirror is d, then the spread △ on the reflecting surface of the rotating polygon mirror is △=d・θ=100×0.08=8 mm when d=100 mm, which cannot be ignored. The phenomenon based on this cause is
For example, as shown in Figure 4, an array light source (1a, 1
If b, 1c, and 1d are arranged parallel to the main scanning direction or almost parallel to the main scanning direction, as shown in FIG. becomes.

Therefore, the reflected light amount distribution of each of the beams 7a, 7b, and 7c collimated by the collimator lens 2 with respect to the rotation angle θ of the rotating polygon mirror 3 becomes as shown in FIG. 6, and the rotation angle effectively used for scanning. part of
2θ ₀ is much narrower than when there is only one light source.

In order to solve this problem, it is necessary to increase the diameter of the rotating polygon mirror, which makes the rotating polygon mirror vulnerable to high-speed rotation, and requires a motor with a large driving force. Moreover, the cost also increases and the size increases. Figure 4B
As shown in FIG.
If d is arranged perpendicular to the main scanning direction, the diameter of the rotating polygon mirror may be the same as in the case of one mirror, but the thickness must be adjusted so that the beam spread on the reflecting surface is distributed in the direction of the rotation axis. A thick rotating polygon mirror is required, and a motor with a large driving force is also required, which is disadvantageous for increasing speed, resulting in increased costs and a larger device.

An object of the present invention is to provide a scanning optical system that can reduce the size of the deflector even when an array light source is used, has a low manufacturing cost, and can correct the influence of the tilting of the deflection surface of the deflector or the rotation axis. Our goal is to provide the following.

A scanning optical system according to the present invention includes a light source section including a plurality of light sources arranged in an array, a collimating section that collimates the plurality of light beams from the light source section, and a collimating section that deflects the light beam from the collimating section in a predetermined direction. a deflection section for scanning, a surface to be scanned simultaneously by a plurality of light beams deflected by the deflection section, a first anamorphic optical member disposed between the collimating section and the deflection section, and a surface for scanning between the deflection section and the surface to be scanned. and a second anamorphic optical member disposed therebetween. In a plane parallel to the deflection scanning plane formed by the light beam scanned by the deflection section, the position of the pupil of the first anamorphic optical member on the deflection section side or the position optically conjugate with the pupil is: By being located near the deflection surface of the deflection section, the deflection surface of the deflection section may be small even though a plurality of light beams are deflected simultaneously. Furthermore, the first anamorphic optical member allows the light beam from the light source section to enter the deflection surface of the deflection section in a substantially parallel light beam state in a plane parallel to the deflection scanning surface, and In a plane perpendicular to the plane, the beam is made incident in such a manner that an image is formed on the deflection plane of the deflection section. Therefore, each light beam from the light source section is formed into a linear image on the deflection surface of the deflection section in a direction parallel to the deflection scanning surface. This linearly imaged beam is imaged onto the scanned surface by the second anamorphic optical member in a good spot condition. At this time, in a plane parallel to the deflection scanning plane, the second anamorphic optical member keeps the deflection surface of the deflection section and the scanned surface in an optically conjugate position, so there is no effect due to the tilting of the deflection section. Corrected.

In the scanning optical system according to the present invention, when the light source is a semiconductor laser, the first anamorphic optical member preferably includes a collimator lens that collimates the light beam from the light source section, and a collimator lens that collimates the light beam from the light source section. It consists of a cylindrical lens that converges the component of the parallel light beam from the meter lens in a plane perpendicular to the deflection scanning plane. The present invention will be described in detail below with reference to the drawings.

7A and 7B are diagrams showing an embodiment of the scanning optical system according to the present invention, where A is a plan view and B is a side view. In FIG. 7A, 11 is a light source section of a semiconductor laser in which a plurality of light sources are arranged in an array, and a light emitting surface 12 of each light beam is one focal plane of a collimator lens 13a constituting an anamorphic optical system 13. It is arranged in The light beam emitted from the semiconductor laser is collimated by a collimator lens 13a, passes through a cylindrical lens 13b, and then enters a rotating polygon mirror 14. Rotating polygon mirror 14
The reflected beam is imaged onto the photosensitive drum 16 by the imaging lens 15.

In the scanning optical system according to the present invention, the deflection scanning plane where the beam is deflected by the rotating polygon mirror, that is, the seventh
In the plane shown in Figure A, a collimator lens 13 is used to collimate the light beam from the array light source.
The position of the pupil on the rotating polygon mirror side of a or a position optically conjugate with the pupil position is located very close to the reflective surface 14b of the rotating polygon mirror 14. In other words, the collimator lens and the light source section are installed so that each principal ray of the luminous flux from each light emitting point of the array light source is parallel to the optical axis of the collimator lens 13a, and It is provided so that the reflective surface 14b of the rotating polygon mirror 14 is located nearby. With such a configuration, no matter how many light source arrays are added, the spread of the light beam on the reflective surface of the deflector remains the same as when the number of light source arrays is one.

Furthermore, as shown in FIG. 7B, the cylindrical lens 13b has power in a cross section perpendicular to the deflection scanning plane, and directs the beam of the array laser onto the reflecting surface 14b of the rotating polygon mirror 14. The image is formed linearly in a direction perpendicular to the rotation axis 14a. This is for the purpose of optically correcting image pitch unevenness caused by the inclination of the reflecting surface of a rotating polygon mirror, as disclosed in, for example, Japanese Patent Publication No. 52-28666.

That is, in the present invention, the reflecting surface 14 of the rotating polygon mirror
In the deflection scanning plane, the position b is near the focal position of the collimator lens, while in the plane orthogonal to the deflection scanning plane, the position b is near the focal position of the collimator lens 13.
This corresponds to the focal position of b.

The imaging lens 15 is also an anamorphic optical system, and in the deflection scanning plane, the reflection surface 14
The parallel beam reflected by b is imaged on the photosensitive drum 16, and in a plane orthogonal to the deflection scanning plane, the reflecting surface 14b and the surface of the photosensitive drum 16 are placed in an optically conjugate positional relationship. It is something to tighten.

As described above, the present invention makes it possible to reduce the size of the rotating polygon mirror, increase the speed of the rotating polygon mirror, and also correct pitch irregularities caused by the tilt of the surface of the rotating polygon mirror.

However, in actual implementation, when it is desired to make the focal length fa of the cylindrical lens 13b larger than the focal length fc of the collimator lens, its arrangement becomes a problem. The present invention also makes such a case possible.

FIGS. 8A and 8B and FIGS. 9A and 9B are diagrams explaining this matter. In Figure 8 A and B, the focal length fa of the cylindrical lens is the focal length of the collimator lens.
fc, the cylindrical lens 13b is smaller than the collimator lens 1 as shown in FIG. 8A.
3a and the reflective surface 14b of the rotating polygon mirror 14, the focal position of the collimator lens and the focal position of the cylindrical lens 13b can be substantially matched. Incidentally, FIG. 8B is a diagram showing the optical path within the deflection scanning plane, and shows the principal rays 17a and 1 from each light source section.
Only 7b and 17c are shown.

On the other hand, the focal length fa of the cylindrical lens is
There are cases where you want to make the focal length longer than the collimator lens. FIGS. 9A and 9B show the configuration in such a case, and by dividing the cylindrical lens 13b into two groups into a convex cylindrical lens 13c and a concave cylindrical lens 13d, the main plane can be positioned on the light source side. As shown in FIG. 9A, the cylindrical lens 13b can be placed between the collimator lens 13a and the rotating polygon mirror 14. Here, FIG. 9B shows an optical path diagram within the deflection scanning plane, and the principal rays 18a, 18b, 18
Only c is shown. Developing the above, the following can be said as shown in Figures 10A and B.

(1) When the collimator lens and the cylindrical lens are considered as a condensing lens 19 as one unit, as shown in FIG. The surface 14b is conjugate.

(2) As shown in Figure 10B, in the cross-sectional direction perpendicular to (1), the infinite object point and the reflecting surface 14 of the rotating polygon mirror
b is conjugate.

If a condensing lens that satisfies the above two functions is considered and designed, it can be used as a tilt correction optical system (incidence side thereof) using an array laser. By thinking in this way, the 9th
It becomes unnecessary to collimate the light exiting the lens 13a as shown in FIG. A, and the degree of freedom increases. This simplifies lens design, and allows the entire lens to be used as a condenser lens to defofocus and adjust focus.

As described above, the present invention uses an array laser to reduce the size and speed, and eliminates pitch unevenness caused by the surface tilt of the deflector, and has excellent effects with a simple configuration.

[Brief explanation of drawings]

Figure 1 is a schematic diagram showing a conventional scanning optical system, Figure 2 is a schematic diagram showing a conventional scanning optical system.
The figure shows an example of an array-shaped semiconductor laser, and Figures 3, 4, A, B, 5, and 6 show examples of an array-shaped light source in a conventional scanning optical system. Diagrams to explain the inconvenience, Figure 7 A and B
8A and 9B are diagrams showing an embodiment of the scanning optical system according to the present invention, and FIGS. FIGS. 10A and 10B are diagrams for explaining the optical arrangement relationship between the light source section and the deflection section of the scanning optical system according to the present invention. 11... Semiconductor laser array, 12... Light emitting surface, 13... Anamorphic optical system, 13a...
Collimator lens, 13b... Cylindrical lens, 14... Rotating polygon mirror, 15... Imaging lens, 16... Photosensitive drum.

Claims (1)

[Claims] 1. A light source section consisting of a plurality of light sources arranged in an array, a collimating section that collimates the light beam from the light source section, a deflection section that deflects the light flux from the collimation section in a predetermined direction, and the collimating section and the deflection section. In between, the light beam from the collimating section is made to enter the deflecting surface of the deflecting section in a parallel beam state in a plane that includes the optical axis of the collimating section and is parallel to the deflection scanning plane of the deflecting section; An anamorphic optical member is disposed in a plane that includes the optical axis of the collimating section and is perpendicular to the deflection scanning surface of the deflecting section, and that focuses the light beam from the collimating section on the deflecting surface of the deflecting section. A scanning optical system having an array light source, characterized in that a position of a pupil within a deflection scanning plane of the deflection unit is on the deflection plane of the deflection unit.