Coherent light generators – Particular temperature control
Reexamination Certificate
2001-06-05
2003-09-30
Ip, Paul (Department: 2828)
Coherent light generators
Particular temperature control
C372S036000
Reexamination Certificate
active
06628683
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor laser device which can reduce variations in the wavelength of light emitted from a semiconductor laser element.
2. Description of the Related Art
As shown in
FIG. 7
, a conventional semiconductor laser device
100
is provided with a semiconductor laser element
102
and a light detecting element
104
. The semiconductor laser element
102
emits a light beam L
1
(hereinafter called “emitted light L
1
” when appropriate) toward a photosensitive material. The light detecting element
104
detects a light beam L
2
(hereinafter called “detected light L
2
” when appropriate) which is emitted separately from the semiconductor laser element
102
in order to detect the amount of light of the emitted light L
1
.
At the semiconductor laser device
100
, in order to suppress variations in the emitted light L
1
which is emitted from the semiconductor laser element
102
, so-called auto power control (APC) is utilized in which the driving circuit of the semiconductor laser element
102
is controlled such that the light amount of the detected light L
2
detected at the light detecting element
104
is made constant.
Because the sensitivity of the light detecting element
104
varies due to the temperature thereof, the detected light L
2
cannot be detected accurately, and accurate AP control cannot be carried out. Further, due to the variations in the temperature of the semiconductor laser element
102
itself, the wavelength of the detected light L
2
emitted from the semiconductor laser element
102
varies, and accurate AP control cannot be carried out.
In order to overcome the aforementioned problems, in the conventional semiconductor laser device
100
, the semiconductor laser element
102
and the light detecting element
104
are mounted to a thermally conductive material
108
which contacts a heat generating element
106
, such that the respective temperatures of the semiconductor laser element
102
and the light detecting element
104
are regulated. However, the light detecting element
104
does not actually detect the output light L
1
which is illuminated onto the photosensitive material, and detects the detected light L
2
which is separate therefrom. Therefore, in this case as well, accurate AP control cannot be carried out.
SUMMARY OF THE INVENTION
In view of the aforementioned, an object of the present invention is to provide a semiconductor laser device which can carry out accurate AP control by directly detecting output light which is illuminated onto a photosensitive material.
A first aspect of the present invention is a semiconductor laser device comprising: an emitting device which emits a light beam which is illuminated onto a photosensitive material; a light-amount detecting device which detects an amount of light of the light beam which is illuminated onto the photosensitive material; a single or plural temperature-adjusting devices which adjust a temperature of the emitting device and a temperature of the light-amount detecting device to constant temperatures; and a control device which controls the amount of light of the light beam emitted from the emitting device, on the basis of the amount of light of the light beam detected by the light-amount detecting device.
Next, the operation of the semiconductor laser device of the first aspect of the present invention will be described.
The emitting device which emits a light beam is provided at the semiconductor laser device. The light beam emitted from the emitting device is illuminated onto a photosensitive material, and the photosensitive material is exposed. The amount of light of the light beam emitted from the emitting device is detected at the light-amount detecting device. On the basis of the amount of light of the light beam detected at the light-amount detecting device, the control device controls the amount of light of the light beam emitted from the emitting device (so-called AP control).
Here, the respective temperatures of the emitting device and the light-amount detecting device are adjusted to constant temperatures by the temperature-adjusting device. Thus, effects due to the temperature characteristics of the emitting device and the light-amount detecting device can be avoided. Namely, although the emitting ability of the emitting device and the detecting ability of the light-amount detecting device vary due to changes in temperature, the emitting ability and detecting ability can be kept constant by adjusting the temperatures of the emitting device and the light-amount detecting device to constant temperatures. Further, the wavelength of the light beam is stabilized. As a result, AP control can be carried out accurately.
In the present invention, the light beam which is illuminated onto the photosensitive material is directly detected by the light-amount detecting device. Thus, AP control can be carried out more accurately than in a case, such as that of the prior art, in which a light beam, which is other than the light beam illuminated onto the photosensitive material, is detected. Namely, in the present invention, in addition to avoiding effects due to temperature, AP control can be improved by directly detecting the light beam illuminated onto the photosensitive material.
In the semiconductor laser device of the first aspect of the present invention, preferably, the temperatures of the emitting device and the light-amount detecting device are adjusted by a single temperature-adjusting device.
In the semiconductor laser device of the first aspect of the present invention, preferably, the emitting device and the light-amount detecting device are mounted to a temperature-regulating block whose temperature is adjusted by a single temperature-adjusting device.
Next, the operation of the above-described semiconductor laser device will be described.
In the present invention, preferably, the emitting device and the light-amount detecting device are mounted to a temperature-regulating block whose temperature is adjusted by a single temperature-adjusting device. In this way, the respective temperatures of the emitting device and the light-amount detecting device can be adjusted.
Here, by providing a single temperature-adjusting device, the temperatures of the emitting device and the light-amount detecting device can be adjusted by a single temperature-adjusting device. As a result, as compared with a case in which plural temperature-adjusting devices are provided, no errors between respective temperature-adjusting devices arise, and adjustment of the temperatures of the emitting device and the light-amount detecting device is easy. Further, by using a single temperature-adjusting device, the number of parts and the number of assembly processes is reduced by that much, and fabrication of the semiconductor laser device is easy.
In the semiconductor laser device of the first aspect, more preferably, the light beam is reflected by a reflection coated optical member for beam reshaping and is detected by the light-amount detecting device.
Next, operation of the above-described semiconductor laser device will be described.
Preferably, the light beam is reflected by a reflection coated optical member for beam reshaping and is detected by the light-amount detecting device. Therefore, a reshaped light beam can be detected. Thus, because the light beam is detected in a reshaped state by the light-amount detecting device, the amount of light of the light beam can be detected accurately, and AP control can be carried out accurately.
An optical member where portion of the light beam passes and another portion of the light beam reflects may be provided in the semiconductor laser device of the first aspect of the present invention for illuminating the reflected light beam onto the photosensitive material and detecting the passed light beam through the optical member with the light-amount detecting device.
In the semiconductor laser device of the first aspect of the present invention, more preferably, a temperatur
Ip Paul
Nguyen Dung
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