JP2000249951A - Laser beam exposure device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate interference noise, generated at the time of irradiation, with no sensitivity loss without restricting the incidence angel of a laser light by obtaining at least one laser light having wavelength meeting a specific expression for the wavelength of an arbitrary laser light without fall when an incident and a reflected light beam have an overlapping part. SOLUTION: A photosensitive material surface is irradiated with plural single- mode laser light beams at the same place. When the light beams made incident on the photosensitive material surface overlap with a light beam reflected by the reverse surface of the base of the photosensitive material, at least one laser light has the wavelength λ2 meeting the expression 4*d*|n1/λ1-ν2/λ2|=m is always present among the plural single-mode laser light beams for the wavelength λ1 that an arbitrary laser light among the single-mode light beams has. In the expression, (d) is the thickness of the base, n1 the refractive index of the base to the wavelength λ1, n2 the refractive index of the base to the wavelength λ2, and (m) an odd number.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser beam exposure apparatus and, more particularly, to a laser beam exposure apparatus which irradiates a plurality of laser beams onto a photosensitive material surface to expose an image on the photosensitive material surface. .

[0002]

2. Description of the Related Art Conventionally, a laser beam having a predetermined wavelength is radiated on a photosensitive material surface and is exposed by scanning along a main scanning direction and a sub-scanning direction to form a desired image. Is being done.

Recently, from the viewpoint of environmental measures, the amount of silver contained in the light-sensitive material has tended to be reduced. In order to maintain the maximum optical density, emulsion particles in the light-sensitive material have been reduced to fine particles. It is becoming more and more. In recent years, heat development processing systems that do not require the dissolution and removal of silver halide have also emerged, but highly transparent photosensitive materials are used for the photosensitive materials used in such heat development processing systems. ing. By the way, it is known that when an image is exposed and formed by irradiating a laser beam onto such a photosensitive material surface, a spiral bright and dark fringe pattern (interference noise) is generated on the photosensitive material surface. This interference noise is caused by the light beam of the laser beam incident on the photosensitive material surface and the light beam transmitted through the photosensitive material, reflected on the back surface of the support of the photosensitive material, and returned to the photosensitive material surface. It is caused by overlapping. In order to eliminate such interference noise, various means have conventionally been studied.
For example, by irradiating a laser beam obliquely on the photosensitive material surface, a light beam incident on the photosensitive material surface, and the light beam transmits through the photosensitive material, is reflected on the back surface of the support of the photosensitive material, and is reflected on the photosensitive material surface. A technique for eliminating the occurrence of interference noise by eliminating the overlap with the returned light beam (Japanese Patent Application Laid-Open No. Hei 8-272050), a technique for obliquely entering a laser beam onto the surface of the photosensitive material, and a halogen technique. Japanese Patent Application Laid-Open Nos. Hei 9-304877 and Hei 10 to prevent interference noise from being generated by a combination with a photosensitive material in which silver halide particle diameter, matting agent arrangement, absorbance at the exposure wavelength, and the like are specified.
-20440, and JP-A-10-197974).

However, when the laser beam is obliquely incident on the surface of the photosensitive material as described above, the support of the photosensitive material is easily affected by flapping, shearing, curling, and the like. Since the incident position of the light changes, there is a problem that the stability of the transport system must be highly secured.

[0005] Also, the silver halide grain size, the amount of silver added,
By the combination of a photosensitive material that defines the absorbance and the like, and a laser beam composed of longitudinal multimode, many interference fringes with different light and dark pitches are formed, and by superimposing and averaging them, the interference fringes are made difficult to see, Techniques for removing interference noise have been proposed (Japanese Patent Application Laid-Open Nos. 8-212521 and 9-304869).

However, in order to form many interference fringes having different light and dark pitches, many wavelengths having a wide wavelength distribution are used. Therefore, there is a problem of so-called sensitivity loss in which a wavelength deviates from the sensitivity distribution peak of the photosensitive material. Yes, a larger amount of light is required to obtain the required sensitivity. For this reason, if the measures are taken by increasing the power of the laser light or increasing the number of lasers, the cost will increase, and the adjustment of each laser will be complicated.

On the other hand, a laser beam having a predetermined wavelength is irradiated on the surface of the photosensitive material, and the photosensitive material is scanned in the main scanning direction and the sub-scanning direction to perform exposure, thereby forming a desired image. In the apparatus, the same laser beam diameter is used irrespective of changes in the density and color of an image to be formed by exposure.

However, in an image formed by exposure, there are portions where the change in image density and color is small, such as a solid image, and conversely, portions where the change in image density and color are large. In general,
Exposure of a portion having a small change in image density and color tends to cause unevenness, so it is desirable to perform exposure using a laser beam having a relatively large beam diameter. If a portion having a large color change is exposed, the resolution of the image deteriorates. Therefore, if you try to expose using a laser beam with a small beam diameter,
Conversely, the uniformity of the portion where the change in image density and color is small is inferior and unevenness is apt to occur. Conventionally, it has been difficult to expose and form an image satisfying both at the same time.

[0009]

DISCLOSURE OF THE INVENTION The present invention has been made in view of such a conventional situation.
Provided is a laser beam exposure apparatus capable of removing interference noise generated when irradiating a laser beam onto a photosensitive material surface without restricting an incident angle of the laser beam on the photosensitive material surface and further reducing sensitivity. It is in.

It is another object of the present invention to provide a laser beam exposure apparatus which can always perform exposure under conditions that match the density and color change of an image to be formed by exposure.

[0011]

According to the first aspect of the present invention,
A laser beam exposure apparatus for exposing an image on a photosensitive material surface by irradiating the photosensitive material surface with a plurality of laser lights, wherein the laser light comprises a single mode laser light, and the plurality of single mode laser lights The light-sensitive material surface is irradiated by irradiating the light-sensitive material at the same position on the light-sensitive material surface, and is transmitted through the light-sensitive material surface and the light-sensitive material surface at the same irradiated position, and is reflected by the back surface of the photosensitive material support. When there is a portion where the light beam returning to the above has an overlapping portion, the wavelength λ1 of any one of the plurality of single mode laser lights has
In contrast, there is provided a laser beam exposure apparatus characterized in that at least one laser beam having a wavelength λ2 satisfying the following formula (A) is always included in the plurality of single mode laser beams.

[0012]

Equation (A) 4 * d * | n1 / λ1-n2 / λ2 | = m (where d is the thickness of the support, n1 is the refractive index of the support for wavelength λ1, and n2 is the wavelength for wavelength λ2. The refractive index of the support, m is an odd number.) The invention according to claim 2, wherein the plurality of single mode laser beams are combined to irradiate the same spot on the surface of the photosensitive material. Item 4. A laser beam exposure apparatus according to Item 1.

According to a third aspect of the present invention, the plurality of single mode laser beams are combined using a condenser lens, a half-wave plate, and a deflecting beam splitter. It is a beam exposure apparatus.

The invention according to claim 4 is characterized in that the sum of the light amounts of the laser light distributed to the wavelength λ1 is equal to the sum of the light amounts of the laser light distributed to the wavelength λ2.
4. A laser beam exposure apparatus according to any one of claims 1 to 3.

The invention according to claim 5 is characterized in that a laser chip temperature control is used to make a predetermined difference between the wavelength λ1 and the wavelength λ2. Laser beam exposure apparatus.

The invention according to claim 6 is characterized in that, among the plurality of single mode laser lights, the emission timing of the laser lights of wavelengths λ1 and λ2 is switched at a speed higher than a predetermined spatial frequency of the exposure image. Claims 1 to 5
A laser beam exposure apparatus according to any one of the above.

According to a seventh aspect of the present invention, the light emission timing of each of the laser beams having the wavelengths λ1 and λ2 is switched by one line or a plurality of lines along the main scanning direction with respect to the sub-scanning direction. 7. A laser beam exposure apparatus according to claim 6, wherein:

According to an eighth aspect of the present invention, the light emission timing of each of the laser beams of the wavelengths λ1 and λ2 is switched by one pixel or a plurality of pixels along the main scanning direction for exposure. Item 7. A laser beam exposure apparatus according to Item 6.

According to a ninth aspect of the present invention, there is provided a laser beam exposure apparatus for exposing an image on a photosensitive material surface by irradiating the photosensitive material surface with a plurality of laser lights, wherein the plurality of laser lights are irradiated on the photosensitive material surface. While irradiating the same spot or adjacent spot on the surface, each laser beam has a different beam diameter according to the spatial frequency of the image, and only the laser beam having the beam diameter according to the spatial frequency of the image is selected. And a laser beam exposure apparatus characterized in that the exposure is performed.

According to a tenth aspect of the present invention, a laser beam having a small beam diameter is used for a portion where the spatial frequency of the image is small, and a beam diameter is largely changed for a portion where the spatial frequency of the image is large. 10. The laser beam exposure apparatus according to claim 9, wherein the laser beam is used.

[0021]

Embodiments of the present invention will be described below.

The laser beam exposure apparatus according to the present invention comprises:
It has a plurality of laser diodes for irradiating a laser beam onto the surface of the photosensitive material.

When irradiating the laser beam emitted from the plurality of laser diodes onto the surface of the photosensitive material, the laser beam is applied to the same portion on the surface of the photosensitive material. The light beams transmitted through the material surface and reflected by the back surface of the support of the photosensitive material overlap with the light beams returned to the photosensitive material surface and interfere with each other, thereby causing interference noise on the photosensitive material surface.

In order to remove such interference noise, for a wavelength λ1 of an arbitrary laser beam among the plurality of laser beams applied to the same portion on the photosensitive material surface,
A wavelength λ satisfying the following equation (A) in the plurality of laser beams.
At least one laser beam having 2 is always provided.

[0025]

Equation (A) 4 * d * | n1 / λ1-n2 / λ2 | = m where d is the thickness of the support, n1 is the refractive index of the support for wavelength λ1, and n2 is the support for wavelength λ2. The refractive index of the body, m, is odd.

The above equation is derived from the optical path phase difference of the laser beam irradiated on the photosensitive material surface. The optical path phase difference of the laser light will be described with reference to FIG.
Reference numeral 00 denotes a photosensitive material support having a thickness d. A photosensitive material is layered on the support 100.
Since it is extremely thin compared to 0, it is not shown for convenience. The light beam A incident on the photosensitive material surface at point A1 is refracted when passing through the photosensitive material surface, is reflected at point C1 on the back surface of the support 100, and reaches point A1 'on the photosensitive material surface. This A
At the point 1 ', it interferes with the light irradiating on the photosensitive material surface.

Now, assuming that the refractive index of the support 100 with respect to the wavelength λ1 is n1, the optical path difference Δ1 at this time is:

[0028]

(Equation 4)

## EQU1 ## here,

[0030]

(Equation 5)

Therefore,

[0032]

(Equation 6)

Therefore, the optical path difference Δ1 is

[0034]

Δ1 = 2 * n1 * d / cosβ1-2 * d * tanβ1 * sin
α1. Here, since sinα1 = n1 * sinβ1 (Snell's law), the optical path difference Δ1 is

[0035]

８1 = 2 * n1 * d * cosβ1

Accordingly, the optical path phase difference δ1 of the laser beam having the wavelength λ1 is obtained as follows.

[0037]

Δ1 = 2 * π / λ1 * 2 * n1 * d * cosβ1 ± π (I) Next, similarly, when the laser beam has a wavelength λ2 different from the wavelength λ1, support for the wavelength λ2 is performed. Body 100
Is n2, the optical path phase difference δ2 at this time is as follows.

[0038]

Δ2 = 2 * π / λ2 * 2 * n2 * d * cosβ1 ± π (II) Therefore, when the absolute value Δδ of the difference between the optical path phase differences of the lights of the two wavelengths λ1 and λ2 is calculated as From (I)-(II) |

[0039]

Δδ = | δ1-δ2 | = 4 * π * d * | n1 * cosβ1 / λ1-n2 * cosβ2 / λ2 | (III) Here, the incident beam on the photosensitive material surface and the support 100 In order to obtain the widest scanning range in a state where the return beams reflected from the back surface of the laser beam overlap, the central incident angle is set to 90 °.
Degrees (normal incidence).

Therefore, cos β1 = cos β2 = 0, and (I
The formula II) is as follows.

[0041]

Δδ = 4 * π * d * | n1 / λ1-n2 / λ2 | (IV) Here, when the difference Δδ = mπ (m: odd number) in the optical path phase difference between the two lights, The light and dark pattern of the interference fringes due to the light of the wavelength is reversed, and the interference noise is removed.

Therefore, by irradiating the laser light having the wavelength λ1 with the wavelength λ2 satisfying the above formula (A) to the same portion on the photosensitive material surface, Thus, it is possible to remove interference noise generated on the photosensitive material surface.

The arbitrary laser beam is a laser beam arbitrarily selected from a plurality of laser beams, and the laser beam exposure apparatus according to the present invention has an arbitrary laser beam among the plurality of laser beams. It is sufficient that at least one laser beam having a wavelength (wavelength λ2) that satisfies the above formula (A) with respect to the wavelength (wavelength λ1).

Therefore, when there are three laser beams,
With respect to the wavelength λ1 of any one of the laser lights, the remaining two laser lights may both have the wavelength λ2, or if there are four laser lights,
The remaining three laser beams may all have the wavelength λ2 with respect to the wavelength λ1 of any one of the laser beams.

The arbitrary laser light is not necessarily limited to one of the plurality of laser lights, but may be two or more. For example, when there are three laser beams, both laser beams may be arbitrary laser beams having a wavelength λ1, or when four laser beams exist, two or three of them are used. Together with the wavelength λ
Any laser light having 1 may be used. in this case,
The remaining one or two laser beams have a wavelength λ2 satisfying the above formula (A).

As described above, the above equation (A) shows the relationship between the wavelength of an arbitrary laser beam and the wavelength of another laser beam. The wavelengths that a plurality of laser beams should have are limited to two types. It does not do. Therefore, for example, when there are four laser beams, one laser beam has the wavelength λa, and the wavelength of one of the remaining three laser beams satisfies the above formula (A) with respect to the wavelength λa.
And one of the remaining two laser beams has another wavelength λc, and the other one has another wavelength that satisfies the above formula (A) with respect to the other wavelength λc. λ
You may make it have d. In this case, if the laser light having the wavelength λa is an arbitrary laser light, the above formula (A) is included in the plurality of laser lights with respect to the wavelength λa.
There is a laser beam having a wavelength λb that satisfies the following relationship, and if a laser beam having a wavelength λc is an arbitrary laser beam, among a plurality of laser beams, the above formula for the wavelength λc is obtained. This means that there is a laser beam having a wavelength λd that satisfies the relationship (A).

That is, when one or a plurality of laser beams having a specific wavelength are arbitrarily extracted and selected from the plurality of laser beams, and the selected laser beam is an arbitrary laser beam, the arbitrary laser beam is At least one laser beam having a wavelength that satisfies the relationship of the above formula (A) exists for the wavelength of the laser beam.

In the laser beam exposure apparatus according to the present invention, in order to eliminate the interference noise, the wavelength of any one of the plurality of laser beams is set so as to satisfy the above expression (A). Although the wavelength of the other laser beam is shifted, the effect of removing interference noise can be obtained by slightly shifting this wavelength.

Incidentally, the thickness d of the support is 180 μm, the refractive index n1 = n2 = 1.5, and the wavelength λ1 of an arbitrary laser beam
= 0.83 μm and m = 1, the wavelength λ
2 = 0.8306 μm. That is, the wavelength λ1 and the wavelength λ
2 is 0.6 nm, and the interference noise can be removed with a very small difference. Here, the refractive index is n
The reason for setting 1 = n2 is that the problem of the occurrence of sensitivity loss is particularly considered. That is, the refractive index of the support slightly varies depending on the wavelength of the laser beam, but in order to prevent the occurrence of sensitivity loss, the wavelength λ2 is preferably as close as possible to the wavelength λ1. Therefore, the refractive index n2 at the wavelength λ2 is considered to be substantially equal to the refractive index n1 at the wavelength λ1, and the wavelength λ2 as close as possible to the wavelength λ1 is derived.

The laser beam used in the present invention is a single mode laser beam. Since the wavelength distribution of the longitudinal multi-mode laser light is wide (several nm or more), some of the light is shifted from the peak of the sensitivity distribution of the photosensitive material, and the sensitivity loss is large. On the other hand, in the case of the single mode laser light, the interference noise can be removed with an extremely small wavelength having a wavelength difference of 1 nm or less as described above, so that the problem of sensitivity loss does not occur.

As described above, each of the plurality of single mode laser beams is distributed to the wavelength λ1 or the wavelength λ2 whose wavelength satisfies the above equation (A). It is preferable that the sum of the light amounts of the divided laser lights is equal to the sum of the light amounts of the laser lights distributed to the wavelength λ2. By making the sum of the light amounts of the laser beams of the respective wavelengths equal, the light and dark intensities of the interference noise generated on the photosensitive material surface substantially match, so that the effect of removing the interference noise can be further enhanced.

To make a predetermined difference such that at least one laser beam has a wavelength λ2 satisfying the above formula (A) with respect to a wavelength λ1 of an arbitrary laser beam among a plurality of single mode laser beams. Although various means can be adopted, it is particularly preferable to control the temperature by controlling the temperature of the laser chip that emits the laser light.

The temperature control of the laser chip can be performed by providing a temperature control means such as a heater or a cooler for each laser chip and appropriately controlling the set temperature of the laser chip by the temperature control means.
In general, since the wavelength characteristics of a laser chip change with temperature, it is possible to control the wavelength of the laser chip very easily by using the temperature control of the laser chip, and to easily set the wavelength λ2 with respect to the wavelength λ1. Can be.

The plurality of laser beams are applied to the same location on the surface of the photosensitive material. To irradiate the same location on the surface of the photosensitive material, a plurality of laser beams must be combined. Means for irradiating the same location on the surface of the photosensitive material, a means for individually irradiating a plurality of laser beams to the same location on the surface of the photosensitive material, or the like.

FIG. 2 shows a multiplexing optical system in which laser beams emitted from two laser diodes 11 and 12 are multiplexed to irradiate the same spot on the photosensitive material surface 20.

The laser beam L11 emitted from one of the laser diodes 11 passes through the condenser lens 11a to the laser beam L11.
/ 2 wavelength plate 30. The half-wave plate 30 is an element that rotates the plane of polarization of the laser light, converts the S-polarized light emitted from the laser diode 11 into P-polarized light, and makes it enter a polarization beam splitter 40 disposed on the optical path.

The laser beam L12 emitted from the other laser diode 12 similarly enters the polarization beam splitter 40 via the condenser lens 12a.

The polarization beam splitter 40 is an optical element that transmits P-polarized light and reflects S-polarized light in the 90-degree direction. The laser beam L11 is transmitted, and the S-polarized laser beam L12 from the laser diode 12 is reflected in a 90-degree direction, so that both laser beams L11,
L12 is multiplexed.

The laser beam L (11 + 12) multiplexed through the polarization beam splitter 40 is reflected by the effective reflection surface of the polygon mirror 50 rotating at a predetermined speed in a predetermined direction, and is irradiated on the photosensitive material surface 20. You. The laser light L (11 + 12) irradiated onto the photosensitive material surface 20 is scanned along the main scanning direction on the photosensitive material surface 20 along with the rotation of the polygon mirror 50, and is transported along the photosensitive material surface 20. Is scanned in the sub-scanning direction.

As described above, the multiplexing optical system is connected to the condenser lens 11a.
And 12a, the half-wave plate 30, and the polarizing beam splitter 40 are preferable because the optical system can be made compact.

FIG. 3 shows four laser diodes 13,
The figure shows a case where laser beams respectively emitted from 14, 15, and 16 are individually irradiated to the same portion on the photosensitive material surface 20.

That is, each of the laser diodes 13, 14,
Laser light L13, L emitted from 15 and 16 respectively
14, L15 and L16 are condenser lenses 13a, 14a and 1 respectively.
The light enters the same polygon mirror 50 individually via 5a and 16a, is reflected on its effective reflection surface, and is irradiated on the photosensitive material surface 20. The polygon mirror 50 is rotated at a predetermined speed in a fixed direction, so that the laser beams L13 to L16 are scanned along the main scanning direction on the photosensitive material surface 20. It will be applied to the spot.

When irradiating a plurality of laser beams individually to the same spot on the photosensitive material surface 20, as shown in FIG. 4, a plurality (two in the illustrated example) of laser diodes 17 are used.
And 18 are reflected by the individually provided polygon mirrors 50a and 50b via condensing lenses 17a and 18a, respectively, to irradiate the same spot on the photosensitive material surface 20. You may make it.

In the embodiment described above, a plurality of single-mode laser beams having a wavelength satisfying the above formula (A) are applied to the same portion on the surface of the photosensitive material, but as described below. The light emission timing of the laser light having the wavelength λ1 and the wavelength λ2 that satisfies the above formula (A) among a plurality of single mode laser lights is switched at a speed higher than a predetermined spatial frequency of the exposure image to irradiate the photosensitive material surface. It can also be done.

The predetermined spatial frequency is so fine that interference fringes are hardly recognized when an image exposed and formed on the surface of the photosensitive material is visually observed. The light emission timing of each laser beam of the wavelength λ1 and the wavelength λ2 that satisfies the above condition is switched. Therefore,
In a plurality of single mode laser beams, the above formula (A)
By switching the emission timings of the laser beams having the wavelengths λ1 and λ2 satisfying the above conditions at a speed higher than a predetermined spatial frequency of the exposure image, the interference noise generated on the photosensitive material surface can be made almost inconspicuous. In particular, according to this embodiment, when viewed with individual laser beams, the lighting time is shorter than that which is always turned on, so that the amount of heat generated by the laser chip can be suppressed accordingly. Therefore, the temperature of the laser chip can be easily controlled, the tolerance for the environmental temperature can be increased, and the effect of improving the life of the laser chip can be obtained.

FIGS. 5 and 6 show that the wavelength λ1 and the wavelength λ of the single-mode laser
FIG. 9 is an explanatory diagram illustrating a state in which the emission timing of the laser light of No. 2 is switched and emitted at a speed equal to or higher than a predetermined spatial frequency of the exposure image.

In order to switch the emission timing of each laser beam, it is necessary to switch the emission timing of each laser beam in the main scanning direction (horizontal direction in the drawing) with respect to the sub-scanning direction (vertical direction in the drawing) (FIG. 5A).
Or when switching every plural lines (FIG. 5B),
There is a case where switching is performed every one pixel (FIG. 6A) or every plural pixels (FIG. 6B) along the main scanning direction.

Whether the emission timing of a plurality of single mode laser beams is switched for each line, for each of a plurality of lines, for each pixel, or for each of a plurality of pixels depends on the spatial frequency of the image to be formed by exposure. It is determined appropriately depending on the situation. Further, the number of lines when switching every plural lines or the number of pixels when switching every plural pixels is appropriately determined according to the spatial frequency of an image to be formed by exposure. In FIGS. 5 and 6, L
B1 and LB2 are wavelengths λ1 (LB
1) and two laser beams having a wavelength λ2 (LB2) when irradiated on the photosensitive material surface 20, respectively.

Referring to FIG. 5 (a), a case in which switching is performed for each line along the main scanning direction with respect to the sub-scanning direction will be described. Scanning is performed along the scanning direction to form a first line along the main scanning direction. At this time, only one of the two laser beams (for example, only the laser beam having the wavelength λ1) is turned on to irradiate the photosensitive material surface 20 with the beam LB1. Next, the photosensitive material is moved in the sub-scanning direction as the photosensitive material is conveyed, and a second line is formed. In the second line, only the laser beam not lit in the first line (wavelength λ2 Only laser light with
To light the beam LB on the photosensitive material surface 20.
2 and scan in the main scanning direction. Thereafter, the operation of switching the emission timing of the laser light for each line along the main scanning direction in the sub-scanning direction is sequentially repeated to expose and form an image on the photosensitive material surface 20.

FIG. 5B is a diagram in which the emission timing of laser light is switched every three lines along the main scanning direction with respect to the sub-scanning direction, and along the main scanning direction with respect to the sub-scanning direction. The operation of switching the emission timings of the two laser beams is repeated sequentially in the same manner as described above for every three lines to form an image on the photosensitive material surface 20 by exposure.

As described above, when the emission timings of a plurality of single mode laser beams are switched for each line or every plurality of lines along the main scanning direction with respect to the sub-scanning direction, a change in density in the sub-scanning direction is problematic. In the case of such an image, the effect of reducing density unevenness due to interference noise in the sub-scanning direction is preferable.

Next, a case in which switching is performed for each pixel along the main scanning direction will be described with reference to FIG. 2
When scanning two laser beams along the main scanning direction on the photosensitive material surface 20, the emission timings of the two laser beams are sequentially switched along the main scanning direction. That is, as shown in the figure, only one of the two laser beams (for example, only the laser beam having the wavelength λ1) is turned on, the beam LB1 is irradiated on the photosensitive material surface 20, and exposure for one pixel is performed. When exposing a pixel adjacent to the beam LB1 along the scanning direction, only the other laser beam (wavelength λ2
(Only the laser beam having the above) is irradiated, and the beam LB2 is irradiated onto the photosensitive material surface 20. As described above, the switching operation of the laser light emission timing is sequentially switched for each pixel along the main scanning direction, so that the photosensitive material surface 2 is switched.
The image is formed by exposing the image on the surface 0. FIG. 6B is a diagram in which the emission timing of the laser light is switched every three pixels along the main scanning direction, and every three pixels along the main scanning direction.
In the same manner as described above, the operation of switching the emission timing of the two laser beams is sequentially repeated to expose and form an image on the photosensitive material surface 20.

As described above, when the emission timings of the plurality of single mode laser beams are switched for each pixel or for a plurality of pixels along the main scanning direction,
This is preferable for an image in which a change in density in both the sub-scanning directions poses a problem, because it has the effect of reducing density unevenness due to interference noise in both scanning directions.

Next, a preferred embodiment of the laser beam exposure apparatus is used when the image to be formed by exposure includes a portion having a small change in image density and color and a portion having a large change in image density and color. The form will be described.

In such a laser beam exposure apparatus, an image is exposed on the photosensitive material surface by irradiating a plurality of laser lights to the same location or adjacent locations on the photosensitive material surface. Each laser beam has a different beam diameter according to the spatial frequency of the image to be formed, and only the laser beam having the beam diameter according to the spatial frequency of the image is selected and exposed.

In order to change the beam diameter of a plurality of laser beams so as to differ according to the spatial frequency of an image to be formed by exposure, for example, a set of a laser and a condenser lens is moved in the optical axis direction, Only, or by moving only the condenser lens in the optical axis direction.

When an image is formed by exposure using such a laser beam exposure apparatus, the beam diameter is reduced at a portion where the spatial frequency of the image to be exposed and formed is small, that is, at a place where the change in image density and color is small like a solid image. Irradiate the photosensitive material surface using a laser beam that has been greatly changed,
Conversely, in a portion where the spatial frequency is large, that is, where the change in image density, color, and the like is large, the light is irradiated onto the surface of the photosensitive material using a laser beam whose beam diameter is changed small.

By exposing a portion of an image having a small spatial frequency using a laser beam having a large beam diameter, uniformity of a solid image can be improved, and image unevenness can be eliminated. By exposing a large portion using a laser beam having a small beam diameter, an effect of improving the resolution of an image is obtained, and it is possible to achieve both improvement in uniformity of an image and improvement in resolution. Therefore, there is an effect that the exposure can be always performed under the condition that matches the density and color change of the image to be formed by exposure.

[0079]

According to the first to eighth aspects of the present invention, when the laser light is irradiated onto the surface of the photosensitive material without restricting the incident angle of the laser light on the surface of the photosensitive material and without causing a loss in sensitivity. Can be eliminated.

According to the invention of claims 9 and 10,
Exposure can always be performed under conditions that match changes in the density and color of an image to be formed by exposure.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating an optical path phase difference of a laser beam irradiated on a photosensitive material surface.

FIG. 2 is an explanatory diagram showing a multiplexing optical system in which laser beams emitted from two laser diodes are multiplexed to irradiate the same spot on a photosensitive material surface.

FIG. 3 is an explanatory diagram showing a case where laser beams respectively emitted from four laser diodes are individually irradiated on the same portion on a photosensitive material surface.

FIG. 4 is an explanatory diagram showing a case where laser beams emitted from two laser diodes are individually irradiated on the same portion on the surface of a photosensitive material.

FIG. 5 (a) is a diagram illustrating a plurality of single mode laser beams, in which the emission timing of the laser beams having the wavelengths λ1 and λ2 is switched with respect to the sub-scanning direction for each line along the main scanning direction. FIG. 3B is a diagram illustrating a state in which the emission timings of the laser beams of the wavelengths λ1 and λ2 of the plurality of single mode laser beams are set for each of a plurality of lines along the main scanning direction with respect to the sub-scanning direction. FIG. 4 is an explanatory diagram for explaining a state in which irradiation is performed by switching to FIG.

FIG. 6A is a diagram illustrating a state in which, among a plurality of single-mode laser lights, emission timings of laser lights having wavelengths λ1 and λ2 are switched for each pixel along a main scanning direction and irradiated. FIG. 3B is an explanatory diagram illustrating a state in which, among a plurality of single mode laser lights, the emission timings of the laser lights of the wavelengths λ1 and λ2 are switched for each of a plurality of pixels along the main scanning direction and irradiated.

[Explanation of symbols]

 11-18 Laser diode 20 Photosensitive material surface 30 1/2 wavelength plate 40 Polarizing beam splitter 50 Polygon mirror 100 Support

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H016 AC00 2H045 AA01 AA54 BA22 BA24 BA32 CA92 CB41

Claims (10)

[Claims] 1. A laser beam exposure apparatus for exposing an image on a photosensitive material surface by irradiating the surface of the photosensitive material with a plurality of laser lights, wherein the laser light comprises a single mode laser light, While irradiating the same place on the photosensitive material surface with a single mode laser beam,
The light beam incident on the photosensitive material surface at the same irradiation location has a portion where the light beam transmitted through the photosensitive material surface and reflected by the back surface of the support of the photosensitive material and returned to the photosensitive material surface overlaps. In the state, the laser light having a wavelength λ2 that satisfies the following formula (A) in the plurality of single-mode laser lights with respect to the wavelength λ1 of any one of the plurality of single-mode laser lights. A laser beam exposure apparatus having at least one. Formula (A) 4 * d * | n1 / λ1-n2 / λ2 | = m (where d is the thickness of the support, n1 is the refractive index of the support for wavelength λ1, and n2 is the wavelength for wavelength λ2. (The refractive index of the support, m is an odd number.) 2. A laser beam exposure apparatus according to claim 1, wherein said plurality of single mode laser beams are combined to irradiate the same spot on the surface of a photosensitive material. 3. The method according to claim 1, wherein the plurality of single mode laser beams are
3. The laser beam exposure apparatus according to claim 2, wherein the multiplexing is performed using a condenser lens, a half-wave plate, and a deflection beam splitter. 4. The laser beam according to claim 1, wherein the sum of the light amounts of the laser light distributed to the wavelength λ1 is equal to the sum of the light amounts of the laser light distributed to the wavelength λ2. Exposure equipment. 5. The laser beam exposure apparatus according to claim 1, wherein a predetermined difference between the wavelength λ1 and the wavelength λ2 is provided by controlling the temperature of a laser chip. 6. The method according to claim 1, wherein the emission timing of the laser light having the wavelength λ1 and the wavelength λ2 among the plurality of single mode laser lights is switched at a speed higher than a predetermined spatial frequency of the exposure image. 5. The laser beam exposure apparatus according to any one of 5. 7. The method according to claim 1, wherein the light emission timing of each of the laser beams having the wavelengths .lambda.1 and .lambda.2 is switched by one line or a plurality of lines along the main scanning direction with respect to the sub-scanning direction. Item 7. A laser beam exposure apparatus according to Item 6. 8. The laser beam according to claim 6, wherein the light emission timing of each of the laser beams of the wavelengths λ1 and λ2 is changed by one pixel or a plurality of pixels along the main scanning direction for exposure. Exposure equipment. 9. A laser beam exposure apparatus for exposing an image on a surface of a photosensitive material by irradiating the surface of the photosensitive material with a plurality of laser beams, wherein the plurality of laser beams are irradiated at the same position or on the surface of the photosensitive material. While irradiating to an adjacent portion, each laser beam has a different beam diameter according to the spatial frequency of the image, and only the laser beam having a beam diameter according to the spatial frequency of the image is selected and exposed. Characteristic laser beam exposure equipment. 10. The portion where the spatial frequency of the image is low,
10. The laser beam exposure apparatus according to claim 9, wherein a laser beam having a small beam diameter is used, and a laser beam having a large beam diameter is used in a portion where the spatial frequency of the image is large.