Optical recording head

Details Optical recording head Optical recording head

1998-11-05

2001-06-19

Tran, Thang V. (Department: 2752)

Dynamic information storage or retrieval

Specific detail of information handling portion of system

Radiation beam modification of or by storage medium

C369S112240, C369S125000, C369S112250

Reexamination Certificate

active

06249502

ABSTRACT:

This application is based on application Nos. 9-306089 and 9-315043 filed in Japan, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical recording head, and more particularly to an optical recording head which has an optical valve element array made of PLZT, LC or the like or a self-emitting element array composed of LEDs and records an image (latent image) on a recording medium such as a photosensitive material and an electrophotographic photoreceptor.
2. Description of Prior Art
As a device for drawing an image (latent image) on a photographic paper or film made of a silver-halide sensitive material or an electrophotographic photoreceptor, an optical recording device which comprises a plurality of optical valve elements using PLZT arranged in a line and controls the optical valve elements to be on or off individually is generally known.
In this type of optical recording device, a two-dimensional image is drawn on a photosensitive material by projecting light, which passed through a plurality of optical valve elements arranged in a line (in a main-scanning direction), onto the photosensitive material and moving the photosensitive material in a sub-scanning direction. In the optical recording device, a great exposure is an indispensable condition for achieving high-speed drawing.
In order to satisfy the condition, the present inventor aimed at providing an integrator on the light emitting side of an optical fiber array for converting light from a light source into a line of light. The area of the light emitting end face of the integrator is made equal to the cross sectional area of the optical fiber array.
As for drawing of a color image using a color photographic paper, there is a known method in which lights of three primary colors are successively projected while switching colors by means of, for example, a color wheel located between a light source and an optical fiber array. The color wheel has R, G, B filters placed at equal intervals around its rotation axis, and is driven to rotate so that switching of the R, G, B filters is executed in synchronization with drawing of one line of each of the three primary colors. The diameter of such a color wheel is substantially proportional to the area of the light incident end face of the optical fiber array.
By the way, as the speed of drawing increases, the cycle of switching the R, G, B filters becomes shorter. This means that the rotation speed of the color wheel needs to be increased. In general, in order to rotate the wheel at a high speed, it is advantageous to decrease the diameter of the wheel. This means that the area of the light incident end face of the optical fiber array becomes smaller, and the illuminating area on the optical valve elements is in turn reduced, due to the above-mentioned proportional relationship. Consequently, higher accuracy is required in positioning the optical valve elements. However, the positioning accuracy requirement can be eased by setting the cross sectional area of the integrator to be greater than the area of the light emitting end face of the optical fiber array. In this case, however, the exposure on the photosensitive material is lowered, and the primary object, namely high-speed drawing, can not be achieved.
Meanwhile, in order to draw a color image at a high speed, Japanese Laid-Open Publication No. 6-347925 proposes a printer provided with three optical recording heads. In such a printer, the three optical recording heads are arranged in a sub-scanning direction, and a so-called tandem system in which an image is composed/recorded by exposing a recording medium (photographic paper) transported in a plane direction successively with an introduction of a predetermined time lag. When exposure is performed by a single head while successively switching the three primary colors B, G, R, the exposure of each color with respect to each pixel is inevitably reduced to one third because of switching. The structure using three heads does not cause such a reduction in exposure, thereby achieving high-speed drawing.
However, with the tandem system, it is difficult to accurately transport the photographic paper in a plane direction through a region where the three recording heads are arranged. More specifically, the exposure points of the B, G, R lights on the recording medium do not coincide with each other due to variations in transport speed of the photographic paper, a zigzag movement of the photographic paper or stretching of the photographic paper itself, resulting in color deviation or running. Moreover, in order to provide images of high quality with this kind of optical recording device, it is preferred to measure the quantity of light of each optical valve element and adjust the quantity of light according to the measured value. However, in the three-head structure of the tandem system, since three calibrators are required, the cost is increased.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an optical recording head which efficiently transmits light to increase the exposure and is suited for high-speed drawing of a color image and a light source device for such an optical recording head.
Another object of the present invention is to provide an optical recording device capable of composing/recording an image accurately on a recording medium by using a plurality of optical recording heads, without requiring more than one calibrator.
In order to achieve the above objects, an optical recording head according to the present invention comprises a light source, an optical fiber array, an integrator, a first optical element disposed in the light incident end section of the integrator, an optical valve array and a second optical element array.
In the optical recording head, light from the light source is emitted linearly through the optical fiber array, and unevenness in distribution of an intensity of the light is reduced by the integrator. Then, the lights are incident to the optical valve array. The first optical element disposed in the light incident end section of the integrator has a function of decreasing the divergent angle &thgr;
1
of light emergent from the optical fiber array, so that the light is emergent from the integrator at a divergent angle &thgr;
1
′ smaller than the divergent angle &thgr;
1
. The optical valve array modulates light by switching each optical valve element between on and off according to image information. The modulated light is focused on a photosensitive material by the second optical element.
Thus, according to the present invention, since the first optical element disposed in the light incident section of the integrator reduces the divergent angle of light emergent from the optical fiber array, divergence of light emergent from the integrator can be suppressed, and the light can be efficiently used to illuminate the optical valve elements. Therefore, even when the intensity of light emitted from the optical fiber array is small, it is possible to prevent lowering of the exposure on the photosensitive material and deterioration of performance of high-speed drawing. Besides, there is no need to decrease the cross sectional area of the integrator according to the cross sectional area of the optical fiber array, thereby ensuring the freedom in designing the optical valve array, etc.
Moreover, in the optical recording head of the present invention, it is preferred to compose the integrator of two mirrors arranged in parallel to each other, use a rod lens as the first optical element and sandwich the rod lens between the two mirrors. By placing the rod lens between the two mirrors, it is possible to maintain the interval of the two mirrors accurately.
Furthermore, an optical recording device according to the present invention comprises: a plurality of optical recording heads for switching on and off a number of optical elements arranged in a main scanning direction according to image data; relay-use imaging optical element a

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