JPH04189568A - Semiconductor laser exposure recorder - Google Patents

Abstract

PURPOSE:To minimize a load on a device to improve an efficiency by a method wherein a resolving power and the number of gradation steps per dot at the time of exposure recording are specified for conducting a recording control. CONSTITUTION:A visual resolution limit and a gradation discriminating capability from a distance of distinct vision are generally known to be 508 dot/inch and 256 gradation steps, respectively. However, these values are maximum thresholds independent of each other, and it is considered that there is no need for meeting the above requirements at the same time. As apparently shown in a figure, where a resolving power is 600 dot/inch or more and a gradation step number is 48 or more, an image quality cannot be improved to a great extent if the resiolving power and the gradation step number are further increased. Therefore, when a resolving power is at least 500 dot/inch and a gradation step number per dot is at least 32 at the time of exposure recording, a high image quality can be obtained with relatively small gradation step number and low resolving power. Therefore, a load on hardware can be reduced, and a recorder of a small-scale and low-cost construction can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a semiconductor laser exposure recording device that uses a semiconductor laser as a light source, scans the laser light emitted from the light source, and performs exposure recording on a photoreceptor. be.

[Prior Art] As is conventionally known, when outputting an image, sufficient image quality can be obtained if the image is output with the number of gradations and resolution that satisfy human visual characteristics.

- Numerically, the visual resolution limit at clear vision distance is said to be 10 cycles/mm (20 dots/mm, 508 dots/inch), and the gradation discrimination ability is said to be 256 gradations.

Therefore, in order to obtain high-quality images, conventional semiconductor laser exposure recording apparatuses adopt a hardware configuration whose ultimate goal is to satisfy the above conditions.

Problem 1 to be solved by the invention However, in the above conventional example, while satisfying the above-mentioned visual characteristics, that is, 10 cycles/mm per pixel.
The image must be output while maintaining the resolution of 256 gradations and controlling the number of 256 gradations for each pixel.

Generally, in a semiconductor laser, it is difficult to control the optical pressure intensity to any desired value, and the output is usually controlled using two values of 0N10FF. At this time, in order to satisfy the above-mentioned conditions, a small resolution (at least 160 cycles/mm) is required, and large-scale and expensive hardware is required.

On the other hand, a technique called pulse width modulation (PWM), which is a method of obtaining gradations by controlling the drive time of a semiconductor laser, is known. In this case, a resolution of approximately 0.2 μm in spatial coordinates is required to satisfy the above conditions, and as with the previous method, large-scale and expensive hardware is required to implement this. There was a drawback.

Furthermore, if an image is compressed with an arbitrary resolution and number of gradations that have not yet been optimized in a region where the above-mentioned visual characteristics cannot be satisfied, there is a drawback that the image quality is significantly impaired.

Therefore, in view of the above-mentioned points, an object of the present invention is to reduce the load on the device as much as possible by combining the optimal number of gradations and resolution in order to obtain high-quality images when scanning and exposing images using a semiconductor laser. It is an object of the present invention to provide a semiconductor laser exposure recording device that can suppress and efficiently output output.

[Means for Solving the Problems] The present invention is a semiconductor laser exposure recording device that uses a semiconductor laser as a light source and scans a laser beam emitted from the light source to perform exposure recording on a photoreceptor. The resolution is 500 dots per inch (500 dots/inch) or more, and the number of gradation steps per dot is 32.
It is equipped with means for performing recording control that is greater than or equal to the value.

Here, it is preferable that the number of gradation steps per one dot is 128 or less.

[Function] According to the present invention, by pressing the image with the optimal resolution and number of gradations, the image is output while at least satisfying the range of resolution 500 dots/inch or more and number of gradations 32 or more. By doing so, it is possible to output high-quality images while suppressing the size and cost of the hardware required for the device.

Furthermore, in order to obtain a device that can output high-quality images while actively suppressing the size and price of the hardware required for the device, it is preferable to limit the number of gradations to 128 or less.

[Embodiments] - Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

The inventor of the present invention uses a semiconductor laser as a light source to
In order to develop a relatively small-scale and inexpensive semiconductor laser exposure recording device that scans the laser light emitted from this light source to record exposure on a photoconductor and print the image, we decided to replace it with a conventional multilevel printer. In order to reduce the number of gradations and resolution that were required, we determined the relationship between image quality and (number of gradations, resolution).

Based on the above relationship, the relationship between the resolution and the number of gradations necessary to output a satisfactory image quality is determined, and by applying it to a semiconductor laser exposure recording device, it is possible to create a relatively small-scale and inexpensive device. However, we were able to obtain a device that outputs high-quality images.

Next, the principle of the present invention will be explained, and a semiconductor laser exposure recording apparatus implemented based on the present principle will be described.

When handling images, how much resolution and number of gradations are required are important issues. - Numerically, the visual resolution limit at clear vision distance is 10 cycles/am (20 dots/+n+
n, 508 dots/inch), and the gradation discrimination ability is said to be 256 gradations. Therefore, it is clear that if the above-described resolution and number of gradations are simultaneously satisfied, a high-quality image that satisfies the visual characteristics can be obtained.

However, the number of gradations and the resolution are independent maximum threshold values, and it is considered that there is no need for both to be satisfied at the same time.

In order to find the truly necessary resolution and number of gradations based on the above assumptions, the inventor of the present invention newly proposed (resolution).

The relationship between the number of gradations) and image quality was reexamined, and the relationships shown in FIGS. 1 and 2 were obtained.

In FIG. 1, the horizontal axis shows the number of gradations, and the vertical axis shows the image quality. The solid line in the figure is for an image output at a resolution of 600 dots/inch, the dotted line is for an image at a resolution of 900 dots/inch, and the broken line is for the number of gradations and image quality for an image at a resolution of 1,200 dots/inch. Indicates the relationship between each. As is clear from Figure 1, resolution 6
If the number of gradations is 0.00 dots/inch or more and the number of gradations is 48 or more, the image quality will not improve significantly even if the resolution and number of gradations are increased beyond these values. That is, resolution 600
In the area near dots/inch and 48 gradations,
The image quality has already reached saturation, and the evaluation values in that area are generally "good."

In other words, based on this result, the resolution is 600 dots/
An image output in inches and 48 gradations is considered to be a high-quality image that already satisfies visual characteristics.

On the other hand, line images such as characters are composed of binary values, and the visual resolution of such images has clearly reached its resolution limit.
Differences can be seen between images output at a resolution of 500 dots/inch or less and images output at a resolution higher than 500 dots/inch. This relationship is shown in FIG.

Furthermore, for images output at a resolution of 500 dots/inch or higher, there is no discernible difference in image quality depending on the resolution.

In other words, for line images, the resolution is 500 dots/
Images output in inches or larger already satisfy visual characteristics and are considered to be high-quality images.

As mentioned above, as shown in Figures 1 and 2, the necessary conditions for obtaining a high-quality image are that the image must be output with a resolution of 500 dots/inch or higher and a range of gradation values of 32 or higher. is shown as the condition.

On the other hand, in a region where the above-mentioned requirements are met, even if the number of gradations and resolution are improved, the effect of improving image quality is not expected to be that great. This is shown in Figures 1 and 2.
It is clear from the figure that the contribution of the number of gradations to the image quality is significantly smaller, especially when the area near the 128 gradation value is one boundary. In other words, in the area below the 128 gradation value, Outputting an image is shown as one sufficient condition for obtaining a high-quality image.

From the above experiments and considerations, the inventor of the present invention has developed a semiconductor laser that satisfies visual characteristics and outputs high-quality images based on the newly discovered relationship between image quality and (number of gradations per resolution). The present invention discloses a semiconductor laser exposure recording device characterized in that the resolution during exposure recording is 500 dots/inch or more, and the number of gradation steps per dot is 32 or more. .

Furthermore, in addition to the above conditions, as a semiconductor laser exposure recording device that efficiently satisfies visual characteristics and outputs high-quality images,
This invention discloses a semiconductor laser exposure recording apparatus characterized in that the number of gradation steps per dot is 128 or less.

FIG. 3 shows an apparatus diagram showing an embodiment of a semiconductor laser exposure recording apparatus that satisfies the above conditions. In Fig. 3, 1 is a semiconductor laser, 2 is a collimator lens, 3 is a rotating polygon mirror,
4 is a rotating polygon mirror drive motor, 5 is a scanning lens system, 6 is a photosensitive recording medium or a drum that supports the photosensitive recording medium, and 7 is a semiconductor laser drive control device that drives the semiconductor laser 1 based on image data.

Next, the operation of one embodiment of the present invention will be explained.

In the semiconductor laser drive control device 7, the drive time of one dot is modulated and controlled based on the input image data, and based on this, the semiconductor laser 1 emits laser light with the drive time modulated. This qualitative relationship is shown in FIG.

The laser beam passes through a collimator lens 2, is deflected by a rotating polygon mirror 3, passes through a scanning lens system 5, and reaches a photosensitive recording medium 6.
The image is then scanned and exposed at a predetermined resolution and recorded.

In this example, the above-mentioned image quality and (number of gradations per resolution)
Based on this relationship, the driving time of the semiconductor laser is adjusted so that 64 time widths are selected within the time corresponding to one dot pitch, and the resolution is adjusted to be 600 dots/inch.

The photosensitive recording medium 6 used in this embodiment is visualized by information light and heat, and is composed of photosensitive silver halide, an organic silver salt, a reducing agent, and a binder, and if necessary, a developing aid. A composition containing an antifoggant, an antistatic agent, etc. is provided in a layer on a support such as paper, plastic, or metal.

Alternatively, the photosensitive recording medium 6 is visualized by information light and heat, and further forms a polymerized image by light, and includes photosensitive silver halide, an organic silver salt, a reducing agent, a polymerizable polymer precursor, and a photopolymerizable polymer. A composition consisting of an initiator and a binder, to which a developing aid, an antifogging agent, an antistatic agent, a coloring agent, etc. are added as necessary, and is provided in a layer on a support such as paper, plastic, or metal. , -layer or multiple layers. Furthermore,
A protective layer may be provided thereon. The shape of the photosensitive recording medium may be flat, cylindrical, roll, etc., but is not particularly limited.

Next, other embodiments will be described.

In the above embodiment, it was shown that one dot gradation was obtained by modulating and controlling the drive time of the semiconductor laser.
As a method of obtaining dot gradation, it is also possible to modulate the intensity of the semiconductor laser. Figure 5 shows this qualitative relationship.

[Effects of the Invention] As explained above, in the present invention, in order to obtain high-quality images, the resolution limit of visual characteristics (10 cycles/mm) is achieved by setting the optimal relationship between resolution and the number of gradations. It is possible to obtain high-quality images with a relatively small number of gradations and resolution even without satisfying the gradation discrimination capability limit (256 gradations), and it is a small-scale and inexpensive device that reduces the load on hardware. A semiconductor laser exposure recording apparatus having the following configuration can be obtained.

[Brief explanation of the drawing]

Figure 1 is a diagram of the relationship between image quality and the number of gradations per resolution for Victorian images, Figure 2 is a diagram of the relationship between image quality and resolution for line images consisting of characters, etc., Figure 3 is a semiconductor laser to which the present invention is applied. FIG. 4 is a qualitative diagram showing pulse width modulation driving of a semiconductor laser; FIG. 5 is a qualitative diagram showing pulse intensity modulation driving of a semiconductor laser. DESCRIPTION OF SYMBOLS 1... Semiconductor laser, 2... Collimator lens, 3... Rotating polygon mirror, 4... Rotating polygon mirror drive motor, 5... Scanning lens system, 6... Photosensitive recording medium or photosensitive recording a drum supporting the body; 7... semiconductor laser drive control device; Figure 3 Figure 5

Claims (1)

[Scope of Claims] 1) A semiconductor laser exposure recording device that uses a semiconductor laser as a light source and scans a laser beam emitted from the light source to perform exposure recording on a photoreceptor, wherein the resolution during exposure recording is 2. 1. A semiconductor laser exposure recording apparatus, characterized in that it is equipped with means for controlling recording so that the number of gradation steps per dot is 500 dots per 54 cm (500 dots/inch) or more and the number of gradation steps per dot is 32 or more. 2) The semiconductor laser exposure recording apparatus according to claim 1, wherein the number of gradation steps per dot is 128 or less.