JPH04243368A - Picture recording device - Google Patents

Abstract

PURPOSE:To realize the picture recorder able to suppress secular density fluctuation resulting from an ambient temperature without need of any special adjustment. CONSTITUTION:For example, a laser light source 4 whose oscillating wavelength with respect to a temperature change has a positive tilt and a photosensitive film 8 whose spectrum sensitivity with respect to an incident wavelength has a positive tilt are combined, while a laser beam is subjected to intensity modulation by using an AOM 5 having a negative temperature characteristic to scan a photosensitive film. A diffraction efficiency is reduced as temperature rises and the light reaching the photosensitive film is reduced, but the oscillating wavelength of the laser is extended to increase the sensitivity of the photosensitive film, then the changes are cancelled together thereby suppressing density fluctuation.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an acousto-optic modulator (hereinafter referred to as
Regarding image recording devices that record images by intensity-modulating light from a light source using an AOM (AOM) and irradiating a photosensitive material with the modulated light, it is particularly useful for recording detailed shading information such as hard copy devices for medical images. The present invention relates to an image recording device that needs to record accurately.

0002

[Prior Art] AOM uses ultrasonic compression waves to cause periodic changes in the refractive index in a medium, and modulates light passing through the medium by diffracting it. Diffraction efficiency (first-order diffracted light/0
(secondary light) is proportional to acoustic power and inversely proportional to wavelength. A laser printer utilizes this relationship to drive an AOM based on an image density signal and irradiates a photosensitive material (photosensitive film, photosensitive drum, etc.) with laser modulated light to record an image. A semiconductor laser is generally used as a light source for a laser printer.

0003

[Problem to be solved by the invention] Laser light source, AOM,
The characteristics of each photosensitive material vary depending on the ambient temperature.
As a result, density fluctuations occur in the recorded image over time. Therefore, countermeasures against this fluctuation are necessary, and examples of conventional countermeasures include JP-A No. 61-53630 and JP-A No. 61-5.
There is one described in 6339.

The technique described in JP-A-61-53630 inserts a filter on the optical path with a transmittance that corrects the spectral characteristics of the semiconductor light source and the spectral sensitivity of the photosensitive material to keep the exposure amount constant. (Conventional example ■). Furthermore, the technology described in JP-A No. 61-56339 (prior art example (■)) allows the center wavelength of fluctuations in the maximum wavelength of the emission spectrum of the light source to almost match the maximum wavelength of spectral sensitivity of the light-sensitive material, and also allows the emission intensity to vary depending on temperature. This is to suppress fluctuations.

However, according to the study conducted by the inventor of the present application, it has become clear that the technique described in the above-mentioned publication has the following problems. That is, in the conventional example (2), it is difficult to manufacture a filter having a transmittance that keeps the exposure amount constant. In the case of a glass filter, the spectral characteristics are determined by the amount of ions added, and it is particularly difficult to realize a double or triple curve. Furthermore, the Wratten filter is not weather resistant, and when changing the photosensitive material, it is necessary to remake the filter, which is troublesome.

Furthermore, in the case of conventional example (2), in order to match the maximum emission spectrum of the light source with the maximum sensitivity of the photosensitive material, the light source or the photosensitive material must be selected, and there is no versatility.

The present invention has been made in view of the problems of the prior art, and its purpose is to provide an image recording device that can suppress temporal density fluctuations caused by environmental temperature without requiring special adjustment. Our goal is to provide the following.

[0008]

[Means for Solving the Problems] The image recording apparatus of the present invention is characterized in that an AOM is used in combination with a diffraction efficiency and a temperature coefficient having opposite signs to the sensitivity wavelength and temperature coefficient of the photosensitive material used. That is.

[0009]

[Operation] When the environmental temperature fluctuates, the sensitivity of the photosensitive material and the diffraction efficiency of the AOM cancel out the fluctuations by changing the characteristics in opposite directions, thereby automatically suppressing the density change.

0010

Embodiments Next, embodiments of the present invention will be described with reference to the drawings.

Example 1 (1) Structure of a medical laser imager (FIG. 1) A medical laser imager transmits a light beam (primary modulated laser beam) modulated based on an input image signal to a photosensitive material film (hereinafter simply referred to as a photosensitive material). A two-dimensional image 9 is recorded on the photosensitive film 8 by scanning the photosensitive film 8 on the photosensitive film 8 and at the same time precisely transporting the photosensitive film 8 in a direction perpendicular to the scanning light (in the direction indicated by the upward arrow in the figure). Then, the photosensitive film is developed to reproduce the image. In this embodiment, a semiconductor laser 4 is used as a light source, and as a mechanism for modulating the AOM 5, a look-up table type signal correction circuit 1 for processing a predetermined signal on an input digital image signal, and a D/A Converter 2 and AOM driver 3
has been established. Further, a deflection mirror (polygon mirror) 6 and an Fθ lens 7 are provided in order to scan the photosensitive sheet with laser light.

(2) Characteristics of the laser light source 4, AOM 5 (including driver 3), and photosensitive film 8 (FIGS. 2, 3, and 4)
) The diffraction efficiency of the AOM5 (including the characteristics of the crystal and driver 3) has a negative slope with respect to temperature as shown in FIG. 2, and as the temperature increases from T1 to T2, the diffraction efficiency (relative value) decreases to 0. 2 Decrease. Further, the wavelength of the output light from the semiconductor laser 4 has a positive slope with respect to temperature (increases by about 0.3 nm/° C.) as shown in FIG. Therefore, when the temperature increases from T1 to T2, the wavelength increases from λa to λb. Further, the photosensitive film 8 has a mountain-shaped sensitivity curve as shown in FIG. 4, with the range A having a positive slope and the range B having a negative slope. The temperature T of the semiconductor laser 4 mentioned above
The wavelength variation width λa-λb for 1 to T2 matches the wavelength width W in FIG. That is, λ1=λa, and λ2
=λb, and the output wavelength of the semiconductor laser 4 is set to, for example, the wavelength λ1. From a general point of view, it is normal to set the oscillation wavelength to the wavelength λ2 at which the sensitivity of the film is maximum, but in this example, in anticipation of fluctuations due to temperature rise, the oscillation wavelength is intentionally set to a wavelength λ1 slightly lower than λ2. We are on the same wavelength.

(3) Density Fluctuation Suppression Operation When the temperature rises (T1→T2), the diffraction efficiency of the AOM decreases (0.8→0.6), and the amount of light reaching the photosensitive film 8 decreases. However, since the wavelength of the semiconductor laser 4 increases (λa→λb), the relative sensitivity of the photosensitive film 8 increases (λ1→λ2). As a result, the decrease in diffraction efficiency and the increase in sensitivity of the photosensitive film 8 cancel each other out, and fluctuations due to temperature are sufficiently suppressed.

(4) Example of trial calculation of fluctuation suppression effect The diffraction efficiency of the AOM has a negative slope as shown in FIG. 5, and the slope α is Δ
n/ΔT=−0.4%/°C (actually measured value). Furthermore, the wavelength temperature characteristic of a semiconductor laser (AlGaAs) has a positive slope as shown in Fig. 6, and the slope β is Δλ/
ΔT=0.3 nm/°C. In addition, the spectral sensitivity of the photosensitive sheet has a substantially positive slope as shown in FIG.
The slope γ in the wavelength range of 00 nm to 820 nm is
+1.0%/nm.

[0015] The fluctuation is calculated using α, β, and γ. β,
From γ, the fluctuation of the semiconductor laser and photosensitive sheet is (0.3
nm/℃)×(+1.0%/nm)=0.3%/
It is ℃. On the other hand, the variation in diffraction efficiency of AOM is -0.4%
/℃, so in total ((β×γ)×α=1.003
×0.999 =0.999), -0.1
This means that the fluctuation can be reduced to %/℃.

Example 2 FIG. 8 is a diagram showing the configuration of a second embodiment of the present invention.

The feature of this embodiment is that two semiconductor laser light sources 4a and 4b with different output wavelengths are prepared, and the light source to be used is selected by switching the switch SW1 as appropriate depending on the characteristics of the photosensitive films 8a and 8b used. It is used to switch. This expands the range of usable photosensitive film properties and improves its versatility.

Although the above description has been made using a medical laser imager as an example, the present invention can be used in general laser recording devices such as laser printers. Furthermore, in the above embodiment, the sensitivity of the photosensitive film has a positive slope with respect to temperature, and the diffraction efficiency of the AOM has a negative slope, but the same effect can be obtained even if the respective slopes are reversed. It will be done.

[0019]

As described above, the present invention suppresses fluctuations by utilizing changes in the characteristics of the constituent elements with opposite signs with respect to temperature, so that the following effects can be obtained. (1) Image density fluctuations due to wavelength fluctuations of the light source can be compensated for without any additional equipment or special adjustments, and deterioration of image quality can be prevented. (2) The device configuration is simple. (3) It requires no additional cost and is easy to implement. (4) With these, a highly accurate and highly reliable image recording device can be provided.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the main part configuration of a first embodiment of an image recording apparatus of the present invention.

FIG. 2 is a diagram showing an example of variation characteristics of diffraction efficiency with respect to temperature of an AOM.

FIG. 3 is a diagram showing an example of the fluctuation characteristics of the oscillation wavelength with respect to the temperature of the semiconductor laser light source.

FIG. 4 is a diagram showing an example of the spectral characteristics of a photosensitive film.

FIG. 5 is a diagram showing an example of variation characteristics of diffraction efficiency for trial calculation of the effects of the example.

FIG. 6 is a diagram showing an example of the fluctuation characteristics of the oscillation wavelength for trial calculation of the effects of the embodiment.

FIG. 7 is a diagram showing an example of spectral characteristics for trial calculation of the effects of the example.

FIG. 8 is a diagram showing the main part configuration of a second embodiment of the image recording apparatus of the present invention.

[Explanation of symbols]

1 Lookup table type signal correction circuit 2
D/A converter 3 AOM driver 4 (4a, 4b) Laser light source 5 AOM modulator 6 Deflection mirror 7 Fθ lens 8 (8a, 8b) Photosensitive film 9 Recorded image

Claims (4)

[Claims] 1. An image recording apparatus that modulates light from a light source with an acousto-optic modulator and records an image by irradiating the modulated light onto a photosensitive material, wherein the diffraction efficiency of the acousto-optic modulator is It has a negative slope with respect to temperature, and as the temperature rises, the diffraction efficiency decreases and the amount of light reaching the photosensitive material decreases.The sensitivity characteristic curve of the photosensitive material has a characteristic that depends on the wavelength of the incident light. There is a region with a positive slope in which photosensitivity increases with respect to an increase in temperature, and the output wavelength of the light source has a positive slope with respect to temperature, and the output wavelength increases as the temperature increases An image recording apparatus characterized in that the wavelength of the output light in a normal operating state is set to a wavelength within a region of the photosensitive material having a positive slope. 2. The image recording apparatus according to claim 1, comprising a plurality of light sources having different output wavelengths, and switching the light source to be used according to the characteristics of the photosensitive material used. 3. An image recording device that records an image by modulating light from a light source with an acousto-optic modulator and irradiating the modulated light onto a photosensitive material, wherein the diffraction efficiency of the acousto-optic modulator is It has a positive slope with respect to temperature, and as the temperature rises, the diffraction efficiency increases and the amount of light reaching the photosensitive material increases.The sensitivity characteristic curve of the photosensitive material has a characteristic that depends on the wavelength of the incident light. There is a region with a negative slope in which the photosensitivity decreases as the temperature increases, and the output wavelength of the light source has a positive slope with respect to temperature, and the output wavelength increases as the temperature rises. An image recording apparatus characterized in that the wavelength of the output light in a normal operating state is set to a wavelength within a region of the photosensitive material having a negative slope. 4. The image recording apparatus according to claim 3, comprising a plurality of light sources having different output wavelengths, and switching the light source to be used according to the characteristics of the photosensitive material used.