JPH0143689Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a laser recording device capable of color recording on photosensitive materials and the like.

[Technical background] In laser recording devices that record images by scanning a laser beam, instead of recording data using a conventional single-wavelength laser, multi-wavelength lasers or single-wavelength lasers are used. The development of a device that can record in color using multiple different types of recording materials is awaited.

FIG. 1 is a diagram showing an optical system of a conventional data recording apparatus using a single wavelength laser. 1 is a laser light source, 2 is an AOM (acousto-optic modulator), 3 is a lens, 4 is a polygon mirror, 5 is an f-θ lens,
6 is a mirror, 7 is a cylindrical lens, and 8 is a photosensitive material. The laser emitted from laser light source 1 is
Modulated by AOM. The laser modulated by the AOM 2 passes through a lens 3, is reflected by a rotating polygon mirror 4, and is deflected. The deflected laser is f
The light passes through the -θ lens 5 and is reflected by the mirror 6, and is recorded by exposing the photosensitive material 8 through the cylindrical lens 7.

However, when creating a laser recording device capable of color recording, it is impossible to apply the above optical system as it is because of the following drawbacks.

First, in order to perform color recording, the wavelengths of the three primary colors λ ₁ , red laser, green laser, and blue laser are usually used.
A color image is recorded on a photosensitive material pixel by pixel using a laser that can emit λ ₂ and λ ₃ , and each pixel is recorded using only one of the three primary colors based on color information. It is something.

FIG. 2 is a diagram explaining chromatic aberration.
R, G, and B indicate red light, green light, and blue light, respectively. As is well known, when the wavelength λ differs, the refractive index of the glass differs.
The three primary color lights of wavelengths λ ₁ , λ ₂ , and λ ₃ emitted from a point have different focal lengths for the same lens as shown in FIG. 2 (this is called longitudinal chromatic aberration). Especially when recording the laser emitted from the f-theta lens on a photosensitive material,
The above-mentioned longitudinal chromatic aberration becomes a problem, and if the photosensitive material 8 is irradiated through the mirror 6 and the cylindrical lens 7 without any correction, even if the laser with wavelength λ ₁ is focused on the photosensitive material 8, λ ₂ and λ ₃ become out of focus, the amount of light per unit area decreases, and the beam diameter changes.

[Purpose of the present invention] The present invention has been developed based on the above points, and its characteristics include a light source section that emits a laser beam, a modulation section that modulates the laser beam, and a deflection section that deflects the laser beam. , an f-theta lens, a recording member,
In the laser recording device, a first mirror that reflects only the laser beam with a wavelength of λ ₃ and a first mirror that reflects only the laser beam with a wavelength of λ ₂ are provided in the optical path between the f-θ lens and the recording member. a second mirror, a third mirror that reflects the laser of wavelength λ ₁ , and wavelengths λ ₃ , λ ₂ , reflected by the first to third mirrors;
A cylindrical lens is provided so that the laser beam of λ ₁ is focused on one point on the recording member.

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

FIG. 3 is a diagram showing an embodiment of the present invention, and is an enlarged view of portions corresponding to the f-theta lens 5, mirror 6, cylindrical lens 7, and photosensitive material 8 in FIG. 1. 9 is a dichroic mirror, 9-1 is a dichroic mirror that reflects only the laser of wavelength λ ₃ and transmits laser of other wavelengths, and 9-2 is a dichroic mirror that reflects only the laser of wavelength λ ₂ . Mirror 9-3 is a dichroic mirror that reflects only the laser beam of wavelength _λ1 , and 10 is a color photosensitive material.

The shorter the wavelength λ, the larger the refractive index and therefore the shorter focal length, and the longer the wavelength λ, the lower the refractive index and therefore the longer focal length. Therefore, the red laser (wavelength λ ₁ ), which has the longest wavelength of the three primary colors, has the longest focal length, and the blue laser (wavelength λ ₃ ) has the shortest focal length.

Therefore, in this invention, as shown in Fig. 3, f-θ
Dichroic mirrors 9-1 to 3 and a cylindrical lens 7 are installed in the optical path so that the focal point of each laser beam is located on the photosensitive material 10. That is, the dichroic mirror 9-
1 is installed at a position where the optical path ABEH is equal to the focal length of the laser of wavelength λ ₃ in the f-θ lens 5. Next, the dichroic mirror 9-2 is installed at a position such that the optical path ACFH is equal to the focal length of the laser of wavelength λ ₂ in the f-θ lens 5. Similarly, the dichroic mirror 9-3 is placed at a position such that the optical path ADGH is equal to the focal length of the laser of wavelength λ ₁ in the f-θ lens 5. As a result, two dichroic mirrors 9-
2 to 3 are installed at the same angle with respect to the dichroic mirror 9-1 at positions a ₁ and a ₂ apart, respectively. A cylindrical lens 7 is placed in the optical path so that the reflected beams from the three dichroic mirrors 9 are irradiated onto one point on the photosensitive material 10.

Next, the recording operation will be explained. For example, the wavelength λ ₁
Assume that the red laser is modulated by the AOM 2, reflected by the polygon mirror 4, and incident on the dichroic mirror 9 via the f-theta lens 5. The dichroic mirror 9-1 transmits the red laser of wavelength λ ₁ without reflecting it, and passes through the dichroic mirror 9-2.
incident on . The red laser beam also passes through the dichroic mirror 9-2, and is first reflected by the dichroic mirror 9-3, taking the optical path of ADGH to expose and record the photosensitive material 10. Next, when a green laser with a wavelength of λ ₂ is incident, the optical path of the ACFH is taken and recorded. A blue laser with wavelength λ ₃ takes the optical path of ABEH and records it. In this way, an optical system optimal for laser color recording can be created.

The present invention has been explained above, but the present invention is
In addition to multi-wavelength lasers that contain the three primary colors, there are also color recording methods that use one single wavelength laser that can emit any of the three primary colors, red, green, and blue, as well as color recording using other methods. It can also be applied to laser light sources for Furthermore, although a photosensitive material was used as the recording member in the above embodiments, the present invention is not limited to this and can be implemented using other recording members.

[Effects of the invention] The invention has been explained in detail above.According to the invention, a dichroic mirror is provided to correct chromatic aberration, and each of the three primary color lasers reflected by the dichroic mirror is exposed to light. By providing a cylindrical lens to expose the same point on the material, it is possible to focus on a single point even when using an f-theta lens whose longitudinal chromatic aberration is not completely corrected, resulting in high quality color. It has become possible to provide a laser recording device that can perform recording, and its effects are significant.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the optical system of a conventional data recording device using single wavelength data, Figure 2 is a diagram explaining chromatic aberration, and Figure 3 is a diagram explaining an embodiment of the optical system of the present invention. It is. DESCRIPTION OF SYMBOLS 1... Laser light source, 2... AOM, 4... Polygon mirror, 5... f-theta lens, 7... Cylindrical lens, 8... Photosensitive material, 9... Dichroic mirror, 10... Photosensitive material.

Claims (1)

[Claims for Utility Model Registration] A light source unit that emits a laser beam, a modulation unit that modulates the laser beam, a deflection unit that deflects the laser beam, and f-
In a laser recording device having a θ lens and a recording member, a first lens that reflects only a laser beam having a wavelength of λ ₃ is provided in an optical path between the f-θ lens and the recording member.
and a second mirror that reflects only the laser at wavelength λ ₂ .
a third mirror that reflects the laser beam with wavelength λ ₁ , and the laser beams with wavelengths λ ₃ , λ ₂ , and λ ₁ reflected by the first to third mirrors converge at one point on the recording member. A laser recording device characterized in that it is provided with a cylindrical lens that makes it possible to