JPH0423988B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Background of the Invention] The present invention relates to an image output method in a laser output device, and more specifically, uses one image data (bit data) to print two types of images, positive and negative, on a photosensitive material. The present invention relates to an image output method for outputting images with uniform quality.

[Problems with Prior Art] In various laser output devices (thermal printers, electrostatic printers, laser phototypesetting machines, etc.), images are generally output in a positive state. On the other hand, since there is a desire to output images in negative format, there are some output devices that can select and output either positive or negative based on instructions from an operator. However, most of these devices do not require high image quality. Therefore, for example, when outputting a negative image using a laser output device, the beam diameter is not changed, but the same bit data as for the positive image is used, and the black and white images are simply inverted and output. It is.

If a high-quality image is not required, the above method is fine, but if you need to output high-quality text/images that require a resolution of several tens of lines/mm or more, the above method can be used as follows. There are various problems.

Figure 2 shows an example of outputting a straight line at an angle of 45° to the main scanning direction in positive (Figure 2 A) and negative (Figure 2 B), such as the horizontal part of the kanji ``大'' (Figure 2). This is a diagram. In Figure 2, the scanning line pitch is P,
The diameter of beam B is d. When outputting 45° straight lines as positive, in order for the straight lines to connect, d≧√
It is necessary to be 2P. In FIG. 2A, the diameter of beam B is set to d=√2P. Figure 2 (b) shows the case where the scanning line pitch and beam diameter are the same as in the case of positive output in Figure 2 (a), and the output is simply turned off and off when the beam is positive. . As you can see from the figure, if you simply invert the on-off state of the beam and output it using common bit data and the same beam diameter in the positive case, the straight line of the negative image will become discontinuous. This means that the image quality of negatives and positives will not be consistent. In addition, if the amount of light of the beam is slightly higher than the appropriate amount of light for the photosensitive material used, or depending on the developing conditions, when outputting as a positive, the joint between the dots of the beam may appear as shown by 9 in Figure 2C. The surrounding area may be exposed to black due to the effect of halation, and as a result, the straight line may become smooth. On the other hand, in the case of negatives, the effect is opposite to this, and the second
As shown in FIG. 2, the portion indicated as 10 becomes black, which may further encourage the straight lines of the negative to become discontinuous.

One possible way to solve the above problem is to keep the beam diameter the same for both negative and positive images, and to prevent discontinuous images by changing the on/off position of the beam. , With this method, bit data cannot be used in common. That is, both the positive bit data and the negative bit data must be stored in the storage device, which has the disadvantage that the amount of storage is doubled.

[Object of the Invention] The present invention has been made based on the above points, and is a laser output device that outputs characters/images in both positive and negative formats. The purpose is to provide an image output method that outputs images, and its feature is that it scans the photosensitive material with a laser beam and outputs characters and images from one image data as either a positive image or a negative image. In the image output method,
A beam diameter converter is provided in the optical path, and the beam diameter converter converts the beam diameter on the photosensitive material when outputting a positive image to d≧√2P (d: beam diameter, P: scanning line pitch) when outputting a negative image. This is to convert the image so that P<d<√2P, expose and scan the photosensitive material, and record the negative and positive images with the same quality.

[Structure of the invention] Hereinafter, the present invention will be explained in detail using the drawings.

As mentioned above, when outputting both positive and negative images using the same bit data, the beam diameter on the photosensitive material is: For positive: d≧√2P For negative: P<d<√2P It must be.

Therefore, in the present invention, a means for changing the beam diameter between positive and negative cases is provided in the optical path, and an image is output with the optimum beam diameter for each case.

FIG. 1 is a diagram showing an embodiment of the present invention, in which 1 is a laser light source, 2 is an AOM (acousto-optic modulator), 3 is a collimator lens, 4 is a beam diameter conversion lens, 5 is a beam expander, and 6 is a A polygon mirror, 7 an f-theta lens, and 8 a photosensitive material. The beam diameter conversion lens 4 is used to change the beam diameter between positive and negative images. In the example shown in FIG.
The beam diameter is optimized by switching between the negative beam diameter conversion lens 4B (1.2 times the scanning line pitch) and the negative beam diameter conversion lens 4B (1.2 times the scanning line pitch). This beam conversion lens is
Since the magnification is low, about 1 to 2 times, it is possible to use an inexpensive configuration of two plano-concave and plano-convex lenses. The optical system is configured as described above, and the beam expander 5
If the beam diameter on the photosensitive material when the beam diameter conversion lens 4 is not inserted into the optical path is set to be about the same as the scanning line pitch, then the beam diameter conversion lens 4 can be inserted. The optimum beam diameter can be obtained by

By doing the above, it is possible to output both negative and positive images with uniform quality using the same bit data.

In addition to the above embodiments, for example, the beam expander 5 can be configured to have a magnification of 10 to 20 without using a beam diameter conversion lens.
It is also possible to use a system in which the beam diameter is changed directly as a zoom lens with a magnification of about 2 times, or by inserting a slit into the optical path to change the beam diameter.

Furthermore, the beam diameter conversion described above can be used not only when switching between positive and negative, but also as a means for subtly changing the design of a font by changing the line width of characters when outputting characters, for example.

[Effects of the Invention] The present invention has been described in detail above, but according to the present invention, the beam diameter can be simply changed using the same bit data without having to store bit data for positive and negative images respectively. This has the effect that both positive and negative images can be output with the same quality just by

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing a state in which the same diagonal lines are output for positive and negative images. 1... Laser light source, 2... AOM, 3... Collimator lens, 4... Beam diameter conversion lens, 5...
...beam expander, 6...polygon mirror,
7... f-theta lens, 8... photosensitive material.

Claims (1)

[Claims] 1. In an image output method in which a photosensitive material is exposed and scanned with a laser beam and characters/images are output as either a positive image or a negative image from one image data, a beam diameter converting means is provided in the optical path. The beam diameter converting means converts the beam diameter on the photosensitive material to d≧√2P (d: beam diameter, P: scanning line pitch) when outputting a positive image, and P<d<√2P when outputting a negative image. An image output method that records an image by exposing and scanning a photosensitive material.