JPH0455871A - Stray light preventing structure for lens array - Google Patents

Abstract

PURPOSE:To prevent stray light in a lens array and to improve the performance of the lens array by forming the light shielding part of incident and exiting surfaces of an irregular reflection surface. CONSTITUTION:In the image-formation optical system lens array (eccentric system lens array) 10 provided with the incident surface 10a and the exiting surface 10b, the light shielding part 2 of the surfaces 10a and 10b in which refraction is not required is formed of the irregular reflection surface. Since the part 2 in which the refraction is not required is formed of the irregular reflection surface, a light beam which is to pass through the part 2 is irregularly reflected and the unnecessary light beam is cut, then the stray light is prevented, an image-formation state is made more excellent and the performance of the lens array 10 is improved.

Description

[Detailed Description of the Invention] [Summary] Regarding the stray light prevention structure of an imaging optical system lens array such as an eccentric lens array, the purpose of this invention is to improve the performance of the lens array. In the imaging optical system lens array, a light-shielding portion of the incident surface and the exit surface that does not require refraction is formed of a diffusely reflecting surface.

[Industrial Field of Application] The present invention relates to a structure for preventing stray light in an imaging optical system lens array such as an eccentric lens array.

In recent years, exposure optical systems for forming latent images in facsimiles and electrophotographic printers are equipped with lens arrays, but there is a demand for cost reduction. For this reason, attempts have been made to use plastic lenses and use decentered lens arrays, but in decentered lens arrays, it is necessary to block light rays other than specific incident light and outgoing light.

[Conventional technology]

Conventional decentered lens arrays have surfaces on which light rays can strike in addition to the areas that should originally enter and exit the lens.

[Problem to be Solved by the Invention] However, it is difficult to hide this portion with a holder for holding the lens array, and when a light ray passes through this surface, it is refracted, which adversely affects the imaging state.

Therefore, stray light is generated and cannot be focused on a single point on the image plane, resulting in a plurality of focus points, resulting in a problem of deterioration of lens performance.

An object of the present invention is to provide a stray light prevention structure for a lens array that can improve the performance of the lens array.

[Means to solve the problem]

In order to achieve the above object, in the present invention, in an imaging optical system lens array having an entrance surface and an exit surface, a light-shielding portion that does not require refraction of the entrance surface and exit surface is
The structure is made of a diffusely reflecting surface.

[For production]

Since the light-shielding portion that does not require refraction (does not require entrance or exit of light rays) is formed of a diffusely reflecting surface, light rays that attempt to pass through the light-shielding portion are diffusely reflected. Therefore, unnecessary light rays are cut, stray light is prevented, and the imaging condition is improved. In other words, it is possible to improve the performance of the lens array.

[Example〕 The invention will now be described in detail in conjunction with the drawings.

FIG. 1 is a front view of the eccentric lens array lO of this example, in which 1 is a plurality of light transmitting parts held by the lens holder 3, 2 is the entrance surface 10a and the exit surface 10b of the lens array 100, This is a portion that does not require refraction, that is, a light shielding portion other than the light transmitting portion 1.

The action of the eccentric lens array 10 is as shown in FIG.
Light that enters the light transmitting portion 1 from the incident surface 10a side hits the internal reflecting surfaces 4, 5.6 and is reflected as shown by the arrow line, and exits from the light transmitting portion 1 on the exit surface 10b side.

The light-shielding portion 2 of the exit surface of this lens array 0 is formed of a diffusely reflecting surface formed by roughening or the like.

Therefore, light rays attempting to pass through the light-shielding portion 2 are diffusely reflected, unnecessary light rays are canted, stray light is prevented, and the imaging condition is improved. In other words, it is possible to improve the performance of the lens array.

Next, an application example of the lens array IO will be shown.

FIG. 3 is a side view showing the main structure of an electrophotographic blink to which the lens array 10 is applied, and FIG. 4 is a perspective view of the same.
11 is an LED array, and 12 is a photosensitive drum.

The light emitted from each LED 11a of the LED array 1 and incident on the light transmitting portion 1 of the entrance surface 10a is transmitted to the exit surface 10b.
The light is emitted from the light transmitting portion 1 and forms an image on the photosensitive drum 12, and an electrostatic latent image is formed on the photosensitive drum 12, which has been uniformly charged in the previous process.

In the next step, this latent image is developed by a developing device (not shown) into a toner image, and this toner image is transferred to a recording paper that is conveyed close to the photosensitive drum 2 by a transfer device (not shown). The transferred toner image is then fixed by a fixing device to become a recorded image.

On the other hand, the light rays (the shaded area in FIG. 3) that enter the light-shielding portion 2 of the entrance surface 10a from each LED 11a are diffusely reflected as described above. Therefore, stray light is prevented and the imaging condition is improved.

〔Effect of the invention〕

As described above, according to the present invention, stray light in the lens array can be prevented by forming the light-blocking portion of the light exit surface with a diffusely reflecting surface. This can be widely applied not only to eccentric lens arrays but to all lens array systems, and greatly contributes to improving the performance of lens arrays.

[Brief explanation of the drawing]

Fig. 1 is a front view of an eccentric lens array according to an embodiment of the present invention, Fig. 2 is an explanatory diagram of the operation of the eccentric lens array, and Fig. 3 is a diagram showing the main points of an electrophotographic printer to which the lens array is applied. FIG. 4 is a perspective view showing the main structure of an electrophotographic printer to which a lens array is applied. In the figure, 2 is a light shielding part, 10 is an eccentric lens array, and 10a is an incident surface , 10b is an output surface. 10 Eccentric lens array 10a entrance surface (10b exit surface) Front view of the eccentric lens array according to the embodiment of the present invention Explanatory diagram of the operation of the eccentric lens array Fig. 2 Electrophotograph to which the lens array according to the embodiment of the present invention is applied Side view showing the structure of the main parts of the printer Figure 3 Figure 4

Claims (1)

[Claims] In an imaging optical system lens array having an entrance surface (10a) and an exit surface (10b), of the entrance surface (10a) and the exit surface (10b), a light-shielding portion that does not require refraction ( 2) A structure for preventing stray light in a lens array, characterized in that the structure is formed of a diffusely reflecting surface.