JPH0527717U - Scanning optics - Google Patents

Abstract

(57) [Abstract] [Purpose] A scan lens can be miniaturized and a manufacturing cost can be reduced, and a writing or reading start position of a scanned medium can be accurately determined. [Structure] The scanning lens 4 is composed of a first lens group 4a having a negative focal length as a whole and a second lens group 4b having a positive focal length as a whole, and a light receiving system reflects light rays reflected from the deflector 2. Since the first lens group 4a is configured to enter the light receiving element 6 without passing through the second lens group 4b after passing through the first lens group 4a, the scanning lens can be downsized and accurate writing and reading start position can be confirmed.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a scanning optical system used for writing in a laser beam printer, a facsimile, etc., and reading in a fax machine, an image scanner, etc., and particularly, downsizing the scanning lens and determining an accurate writing start position or reading start position. The present invention relates to a scanning optical system that can be used.

[0002]

[Prior Art]

 In laser beam printers, facsimiles, bar code readers, image scanners, etc., writing and reading are performed while scanning the light flux by the scanning optical system. FIG. 2 is a plan view showing the arrangement of the scanning optical system 101 of the conventional laser beam printer. The scanning optical system 101 includes a light source 102, a deflector 103, an fθ lens 104, a photosensitive drum 105 that is a medium to be scanned, and a light receiving element 106. The processing circuit 108 sends a signal representing an image to be printed by the laser beam printer to the light source 102, and the light source 102 optically modulates and outputs the laser beam 110 to the deflector 103. The light source 102 is composed of, for example, a semiconductor laser oscillator and a lens.

The deflector 103 has a flat reflecting surface on the outer peripheral surface of a prism whose cross section at right angles to the axis 120 is, for example, a regular polygon such as a regular hexagon, and which is uniform in the axial direction. It is normal to the axis. The deflector 103 is rotated about the axis at a constant speed in a direction indicated by an arrow 114, and reflects the laser beam 110 from the light source 102 in a direction in which it is displaced at a constant angular velocity. The laser beam reflected by the deflector 103 is incident on the fθ lens 104 made of glass or plastic. Although this fθ lens is described as a single lens, it may be composed of a plurality of lenses. The fθ lens 104 causes the laser beam from the deflector 103 to form a point image on the right cylindrical photosensitive drum 105, and the point imaged laser beam is directed to the photosensitive drum 105 in a direction indicated by an arrow mark 113. It is formed and arranged so as to be scanned at a constant speed. The light receiving element 106 is on the opposite side (right side in FIG. 2) to the direction indicated by the arrow 113 from the optical path to the irradiation position of the laser beam 115 on the photosensitive drum 105, that is, the writing start position. It is arranged on the optical path between the lens 104 and the photosensitive drum 105. The light receiving element 106 receives the laser beam 111 reflected by the deflector 103 and refracted and transmitted through the fθ lens 104 in order to align the writing position of the scanning lines sequentially scanned on the photosensitive drum 105, and photoelectrically converts the laser beam 111. The signal is output to the processing circuit 108.

The operation of the scanning optical system 101 will be described below. The processing circuit 108 outputs a signal representing one image line in synchronization with a signal output by the light receiving element 106 receiving the laser beam 111. The light source 102 performs optical modulation according to this signal and outputs a laser beam 110. The laser beam 110 is reflected by the deflector 103 and forms an image on the photosensitive drum 105 via the fθ lens 104. Since the deflector 103 rotates at a constant rotation speed, the direction of the laser beam reflected by the deflector 103 changes at a constant angular velocity, and the fθ lens 104 causes the laser beam on the photosensitive drum 105 to move. And the photosensitive drum 105 is scanned at a constant speed. The laser beam irradiates the photosensitive drum 105 while scanning in the direction indicated by arrow 113. With the rotation of the deflector 103, the laser beam 110 is sequentially reflected by the reflecting surfaces 130 to 135 of the deflector 103, and the laser beam 111 reflected by each surface is sequentially received by the light receiving element 106. .. The light receiving element 106 gives a signal to the processing circuit 108. Based on this signal, the writing position of the scanning line is adjusted. After that, the above-mentioned operation is repeated. In this way, the laser beam is repeatedly imaged line by line on the photosensitive drum 105 to form an electrostatic latent image. The electrostatic latent image is visualized as a toner image by a magnetic brush developing device (not shown) or the like. This toner image is transferred and fixed on a printing paper or the like to print.

In such a scanning optical system 101, a laser beam is imaged on the photosensitive drum 105 by the fθ lens 104, but the light receiving element 106 physically scans the photosensitive drum 105 or the like because of its size and shape. In many cases, they cannot be installed on the same surface of the medium, and they are usually installed closer to the fθ lens 104 than the photosensitive drum 105 as shown in FIG. Therefore, because the relationship between the object point and the image point is not satisfied, the laser beam 111 is not imaged on the light receiving element 106, and the light receiving element 106 receives the laser beam 111 having a considerably wide area. .. Therefore, the light receiving element 106 outputs a signal having instability, which causes an error in the writing start position of the photosensitive drum 105. When such an error occurs, the writing start position meanders, and the printed image is distorted or grainy, and a clear image cannot be obtained.

As one means for solving such a problem, a scanning optical system 101a is shown in FIG. In the scanning optical system 101a, the laser beam 111 is reflected by the reflecting mirror 107 and received by the light receiving element 106a. In this scanning optical system 101a, the distance from the reflecting mirror 107 to the light receiving element 106a is set to be equal to the distance shown by a virtual line 116 from the reflecting mirror 107 to the surface of the photosensitive drum 105. Therefore, the laser beam 112 is imaged on the light receiving element 106a, and the light receiving element 106a can output a stable signal.

[0007]

[Problems to be solved by the device]

 However, the error in the angle of the reflecting mirror 107 is doubled in the traveling direction of the laser beam 112 due to the principle of optical leverage. Due to this, the optical axis of the reflecting mirror 107 is aligned, that is, the laser beam 111 passing through the optical path to be received by the light receiving element 106a is correctly reflected by the reflecting mirror 107, and the laser beam 112 is reflected by the light receiving element 106a. High precision is required for adjustment to receive light. For this reason, the scanning optical system 101a requires fine adjustment of the reflecting mirror 107, and such adjustment must be performed individually at the time of assembly, which significantly hinders the efficiency of production.

As described above, the conventional techniques have problems such as non-uniform writing start positions of the photosensitive drums 105 or the necessity of delicate adjustment of the reflecting mirror 107. Further, in the conventional scanning optical system, since the laser beam is distributed to the light receiving element side, the diameter of the scanning lens is increased correspondingly, the size of the entire apparatus is increased and the cost is increased. The object of the present invention is to solve such technical problems, to downsize the scanning lens and the scanning optical device, and to accurately set the writing or reading start position of the medium to be scanned. It is to provide a scanning optical system that can be determined and is easy to adjust at low cost.

[0009]

[Means for Solving the Problems]

 That is, in this invention, a light source, a deflector, and a scanning lens are arranged, and the light emitted from the light source is imaged on a medium to be scanned through the deflector and the scanning lens in this order, and scanning is performed in order. In addition, a light receiving system including a light receiving means is provided between the deflector and the medium to be scanned, the light reflected by the deflector is received, and writing or reading of the medium to be scanned is performed in synchronization with its output. In the scanning optical system for performing the above, the scanning lens is arranged on the deflector side and has a negative first focal length, and the second lens group is disposed on the scanned medium side and has a positive focal length. And a lens group, and the light receiving system is configured such that the light transmitted through the first lens group is directed to the light receiving means without entering the second lens group.

[0010]

[Action]

 The scanning optical system of the present invention comprises a first lens group which has a negative focal length as a whole and which constitutes a scanning lens, and a second lens group which has a positive focal length as a whole. Light that has not passed through the second lens group after passing through it enters the light receiving element and outputs a signal. Further, by arranging the condenser lens in front of the light receiving element, the common relation is more matched, and the light receiving element outputs a more stable signal.

[0011]

【Example】

 An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a scanning optical system according to the present invention. The scanning optical system includes a light source 1, a deflector 2, and a light from the light source 1 directed toward a photosensitive drum (not shown) which is a medium to be scanned. It includes a cylindrical mirror 3 that reflects light, a scanning lens 4, a condenser lens 5, and a light receiving element 6. In the figure, reference numeral 7 is a collimator lens, 8 is a cylindrical lens, 9 is a mirror, and 10 is a signal processing means. The light source 1 is adapted to cause light to enter the deflector 2 via a collimator lens 7, a cylindrical lens 8 and a mirror 9. In this embodiment, a semiconductor laser (LD) is used as the light source 1. .. Here, the collimator lens 7 forms divergent light emitted from the semiconductor laser into normal light, and the cylindrical lens 8 forms a line image in the vicinity of the deflective reflection surface of the deflector 2. .. The deflector 2 reflects the light from the light source 1 toward the cylindrical mirror 3 via the scanning lens 4, and in this embodiment, a hexagonal prism-shaped polygon mirror is used.

The cylindrical mirror 3 is arranged such that the deflecting reflection surface of the deflector 2 and the photosensitive drum surface are optically in common, and the light beam on the photosensitive drum surface in the sub-scanning direction due to the surface tilt of the deflector 2 The light beam is incident on the photosensitive drum. Incidentally, a predetermined area on the photosensitive drum where this light beam is incident is given a predetermined potential in the same manner as in a normal dry copying machine, that is, by a corona discharge by a charger, etc., and an electrostatic latent image formed by this is applied. It is designed to make a visible image by rubbing a magnetic brush of a developing device. The scanning lens 4 is disposed on the deflector 2 side and has a first negative lens lens group 4a as a whole, and the cylindrical lens 3 (scanned medium) side is a second lens lens having a positive positive focal length as a whole. And the group 4b. The first and second lens groups may each be composed of a plurality of lenses. The light receiving system includes a first lens group 4a, a condenser lens 5, and a light receiving element 6. The first lens group 4a takes out a part of the light reflected by the deflector 2 directly to the outside without passing through the second lens group 4b and emits it to the light receiving element 6, and writing or reading is performed. It is designed to be used to obtain information as timing alignment when positioning at the time. In this case, the spread light is incident on the light receiving element 6, but there is no practical problem. Further, it is preferable to dispose the condenser lens 5 between the first lens group 4a and the light receiving element 6 because the common relation is matched and a more stable signal can be output. The condensing lens 5 is composed of a convex lens provided at a predetermined position on the optical path of the light beam from the first lens group 4a toward the light receiving element 6, and is adapted to form a point image on the surface of the light receiving element 6. There is.

The light-receiving element 6 outputs a signal corresponding to the light intensity by photoelectric conversion when light from the light source 1 is incident, and outputs the signal to the signal processing means 10. There is. The signal processing means 10 outputs to the light source 1 a signal for printing information corresponding to one image line in synchronization with the rising edge of the signal output from the light receiving element 6 that receives the light from the light source 1. The light source 1, which receives this signal, modulates light according to the signal and outputs a light beam. In the configuration of the present invention, the second lens group 4b is not used in the light receiving system regardless of the presence or absence of the condenser lens 5, so that the outer diameter of the second lens group 4b can be reduced.

[0014]

[Effect of the device]

 As described above, according to the scanning optical system of the present invention, a part of the light beam from the light source after passing through the first lens group is made incident on the light receiving element without being made incident on the second lens group. With this configuration, the scanning lens can be downsized, the device can be downsized, and the manufacturing cost can be reduced. Furthermore, if a condenser lens is used for the light receiving system, the light from the light source is imaged on the light receiving element through a part of the scanning lens, and it responds / synchronizes with the signal output by being photoelectrically converted by the light receiving element. Since the timing of the start operation of writing or reading is adjusted, accurate writing and reading can be performed.

[Brief description of drawings]

FIG. 1 is a plan view showing the arrangement of a scanning optical system according to the present invention.

FIG. 2 is a plan view showing the arrangement of a conventional scanning optical system.

FIG. 3 is a plan view showing the arrangement of another conventional scanning optical system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 light source 2 deflector 4 scanning lens 4a first lens group 4b second lens group 5 condenser lens 6 light receiving element

Claims (1)

[Scope of utility model registration request] 1. A light source, a deflector, and a scanning lens are provided, and light emitted from the light source is imaged on a medium to be scanned through the deflector and the scanning lens in this order, and is sequentially scanned. A scan for forming a light receiving system having a light receiving means between the deflector and the medium to be scanned, receiving the light reflected by the deflector, and writing or reading the medium to be scanned in synchronization with the output thereof. In the optical system, a first lens group having a negative focal length as a whole, wherein the scanning lens is disposed on the deflector side, and a second lens group having a positive focal length as a whole, disposed on the scanned medium side. The scanning optical system is characterized in that the light receiving system is configured such that the light transmitted through the first lens group is directed to the light receiving means without entering the second lens group.