JP2006139844A - Optical pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup device in which the quantity of light injected into a monitor element for monitoring the quantity of light of a laser light source is stabilized with respect to wavelength variation of the light source. <P>SOLUTION: The optical pickup device includes a laser light source that emits light for irradiating an optical disk, a light-receiving element that receives light reflected on the optical disk, a monitor element for monitoring the quantity of light emitted by the light source, a first optical element that exists in the optical path, starting from the light source to the optical disk, for guiding a part of the light from the light source to the monitor element and guiding the rest to the optical disk, and a second optical element that exists in the optical path, starting from the first optical element to the monitor element. When the quantity of light guided to the monitor element by the first optical element is changed due to the wavelength variation of the light source, the second optical element corrects the change in the light quantity. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical pickup device that controls the output of a light source using a monitor element. More specifically, the present invention relates to an optical pickup device that corrects a change in light amount due to a wavelength variation of light incident on a monitor element.

Conventionally, as this type of optical pickup device, for example, those described in Patent Documents 1 to 5 are known.
JP 2004-39163 A JP-A-8-315400 Japanese Patent Laid-Open No. 2001-23218 JP 2004-110909 A JP 2004-164681 A

  10 and 11 are configuration diagrams of a conventional optical pickup device corresponding to DVD reproduction and CD recording.

  Reference numerals 1 and 2 denote a first light receiving / emitting unit (laser light source and light receiving element) and a second light receiving / emitting unit (same as above) each including a semiconductor laser element and a photodetector, 3 a beam splitter, 4 a collimating lens, and 5 a stand The upper mirror, 6 is an objective lens, 7 is an optical disk, 8 is a front monitor element, 9 is an aperture limit, and 10 is a half-wave plate.

  The optical disk 7 corresponds to DVD and CD having different substrate thicknesses. The first light emitting / receiving unit 1 is for reproducing a DVD, and the second light emitting / receiving unit 2 is for recording, reproducing and erasing a CD.

  The beam splitter 3 has two prisms bonded together, and a wavelength selection film 3a is provided on the bonding surface. The wavelength selective film 3a has different transmittance / reflectance at the wavelengths of the two light beams for DVD and CD, and selectively transmits or reflects each light beam. For example, most of the light beam for DVD is transmitted, while most of the light beam for CD is reflected.

  The light beam 11 emitted from the first light emitting / receiving unit 1 has a plane of polarization rotated by 90 ° by the half-wave plate 10, enters the beam splitter 3 as S-polarized light, is reflected by the wavelength selection film 3 a, and is collimated. 4 makes it substantially parallel. The substantially parallel light beam 11 is focused on the optical disk 7 (in this case, DVD) by the objective lens 5. Then, the light is reflected by the optical disk 7, passes through the objective lens 5 and the collimating lens 4, is reflected by the beam splitter 3, and returns to the first light emitting / receiving unit 1. The returned light beam 11 is guided to the light receiving element in the first light receiving and emitting unit 1.

  The light beam 12 emitted from the second light emitting / receiving unit 2 enters the beam splitter 3 with P-polarized light, passes through the wavelength selection film 3 a of the beam splitter 3, and becomes substantially parallel by the collimating lens 4. The substantially parallel light beam 12 is focused on the optical disc 7 (in this case, CD) by the objective lens 5. Then, it is reflected by the optical disc 7, passes through the beam splitter 3 through the objective lens 5 and the collimating lens 4, returns to the second light receiving / emitting unit 2, and is guided to the light receiving element in the second light receiving / emitting unit 2.

  The wavelength selection film 3a of the beam splitter 3 transmits most of the light beam 12 from the second light emitting / receiving unit 2, but reflects a part (about 10%). The reflected light 13 is focused by the aperture limit 9 and enters the front monitor element 8.

  The front monitor element 8 outputs an electrical signal corresponding to the amount of light of the incident light beam 13. Since the electric signal output from the front monitor element 8 and the light amount of the light beam collected on the optical disc 7 are in a substantially proportional relationship, the light beam condensed on the optical disc 7 is referred to the electric signal output. The drive current of the semiconductor laser element in the second light emitting / receiving unit 2 is controlled so as to have an appropriate intensity.

  As the wavelength selection film 3a, an optical thin film having a substantially constant reflection / transmission efficiency in the vicinity of the wavelengths of the two light beams for DVD and CD is used. However, although it is substantially constant, the reflection / transmission efficiency still varies by several percent with respect to the wavelength (within the wavelength variation range of the light source). For this reason, when the wavelength of the light beam emitted from the semiconductor laser element in the second light receiving and emitting unit 2 fluctuates due to a temperature rise or the like, the wavelength selection film 3a is reflected / transmitted even if the amount of the emitted light is constant. The amount of light beam varies, and the amount of light incident on the front monitor element 8 varies. Although the change amount of the light amount due to this fluctuation is small, the change rate of the light amount incident on the front monitor element 8 is large, and as a result, the output adjustment of the semiconductor laser element is greatly affected. For example, when the transmission efficiency of the wavelength selection film 3a is changed from 97% to 96% and the reflection efficiency is changed from 2.5% to 3.5% due to the wavelength variation of the semiconductor laser element, the amount of light to the optical disc 7 is slightly increased. However, since the amount of light incident on the front monitor element 8 increases by 40%, the output of the semiconductor laser element in the second light emitting / receiving unit 2 is greatly reduced.

  In this way, an optical element that guides a part of the light from the light source to the monitor element even though the actual light amount of the light source does not change due to a change in the wavelength of the light emitted from the light source due to a temperature rise or the like. Depending on the characteristics (for example, transmission efficiency and reflection efficiency) of the mirror (eg, mirror and beam splitter), the amount of light guided to the monitor element varies. As a result, there is a problem that accurate recording and reproduction cannot be performed.

  In order to solve the above problems, according to the present invention, a laser light source that emits light for irradiating an optical disc, a light receiving element that receives light reflected on the optical disc, and an amount of light emitted by the light source A monitor element for monitoring, a first optical element that exists in the optical path from the light source to the optical disk and that directs a part of the light from the light source to the monitor element, and guides the rest to the optical disk, and from the first optical element to the monitor element And a second optical element existing in the optical path of the optical pickup device, and the second optical element corrects the change in the amount of light when the amount of light guided to the monitor element by the first optical element changes due to wavelength variation of the light source. Provided.

  “Correcting the change in the amount of light” means reducing (compensating) the rate of change of the amount of light guided to the monitor element due to the wavelength variation of the light source. The change rate of the light quantity is expressed by the formula ((maximum light quantity within the wavelength fluctuation range of the light source) − (minimum light quantity within the wavelength fluctuation range of the light source)) / (minimum light quantity within the wavelength fluctuation range of the light source). The Preferably, the change rate of the light amount is 80% or less, more preferably 70% or less, more preferably 60% or less, and still more preferably 50% or less, when only the first optical element is installed, by installing the second optical element. Is done.

  When the amount of light guided to the monitor element by the first optical element is larger on the short wavelength side than on the long wavelength side within the wavelength variation range of the light source, the second optical element is shorter than on the long wavelength side. It is composed of an optical element having a small transmission efficiency on the wavelength side. Conversely, when the amount of light guided to the monitor element by the first optical element is smaller on the short wavelength side than on the long wavelength side within the wavelength variation range of the light source, the second optical element is on the long wavelength side. Compared with an optical element having a large transmission efficiency on the short wavelength side. Here, the transmission efficiency refers to a ratio of outgoing light (light used as incident light to the monitor element such as reflected light, transmitted light, and diffracted light) with respect to the amount of incident light.

  The second optical element is preferably composed of an optical thin film.

The optical thin film used for the second optical element is composed of a multilayer film in which two or more kinds of dielectric films are alternately stacked. Dielectrics that can be used for the optical thin film are known in the art, and examples include TiO ₂ , SiO ₂ , MgF ₂ , and ZnS. The thickness and the number of layers of the multilayer film are selected so that desired optical characteristics can be obtained. For example, if the thickness is such that the phase of the light reflected from the front and back surfaces of the layer is shifted by a wavelength / 2, the reflected light cancels each other, and reflection of the wavelength light at the layer is suppressed. If the thickness is such that the phases of the light reflected from the back surface overlap, the reflection efficiency of the wavelength light at the layer increases. A method known in the art, for example, a vapor deposition method or a sputtering method can be used for laminating the dielectrics. The dielectric multilayer film is formed so that the tensile stress or compressive stress generated in each dielectric layer is canceled as a whole.

  When the second optical element is an optical thin film, preferably the first optical element is also an optical thin film (for example, a mirror film, a wavelength selection film in a beam splitter), and is configured as a mirror (for example, a rising mirror). Alternatively, it may be configured as a beam splitter for separating the forward return path, or for separating / combining the optical paths of two or more light beams.

  In one embodiment of the apparatus of the present invention, the first optical element is a first optical thin film that reflects part of the light to the monitor element and transmits the rest to the optical disc, and the second optical element is the first optical element. The optical pickup device is a second optical thin film that transmits light from the optical element to the monitor element. In the present embodiment, when the reflection efficiency of the first optical thin film is smaller on the longer wavelength side than on the shorter wavelength side within the wavelength variation range of the light source, the amount of light guided to the monitor element by the first optical element changes. Since the transmission efficiency of the second optical thin film is larger on the long wavelength side than on the short wavelength side, the change in the amount of light is corrected. On the contrary, when the reflection efficiency of the first optical thin film is larger on the long wavelength side than on the short wavelength side, the change in light quantity is corrected by the fact that the transmission efficiency of the second optical thin film is smaller on the long wavelength side than on the short wavelength side. Is done.

  In another embodiment of the apparatus of the present invention, the first optical element is a first optical thin film that transmits a part of the light to the monitor element and reflects the rest to the optical disk, and the second optical element is the first optical element. The optical pickup device is a second optical thin film that transmits light from the optical element to the monitor element. In the present embodiment, when the transmission efficiency of the first optical thin film is smaller on the longer wavelength side than on the shorter wavelength side within the wavelength variation range of the light source, the amount of light guided to the monitor element by the first optical element changes. Since the transmission efficiency of the second optical thin film is larger on the long wavelength side than on the short wavelength side, the change in the amount of light is corrected. Conversely, when the transmission efficiency of the first optical thin film is larger on the long wavelength side than on the short wavelength side, the light quantity change is corrected by the fact that the transmission efficiency of the second optical thin film is smaller on the long wavelength side than on the short wavelength side. Is done.

  According to still another embodiment of the apparatus of the present invention, the first optical element is a first optical thin film that reflects part of the light to the monitor element and transmits the rest to the optical disk, and the second optical element is the first optical element. It is an optical pickup device which is a second optical thin film that reflects light from one optical element to a monitor element. In the present embodiment, when the reflection efficiency of the first optical thin film is smaller on the longer wavelength side than on the shorter wavelength side within the wavelength variation range of the light source, the amount of light guided to the monitor element by the first optical element changes. Since the reflection efficiency of the second optical thin film is larger on the long wavelength side than on the short wavelength side, the change in the amount of light is corrected. Conversely, when the reflection efficiency of the first optical thin film is larger on the long wavelength side than on the short wavelength side, the change in light quantity is corrected by the fact that the reflection efficiency of the second optical thin film is smaller on the long wavelength side than on the short wavelength side. Is done.

  In yet another embodiment of the apparatus of the present invention, the first optical element is a first optical thin film that transmits part of the light to the monitor element and reflects the rest to the optical disc, wherein the second optical element is the first optical element. It is an optical pickup device which is a second optical thin film that reflects light from one optical element to a monitor element. In the present embodiment, when the transmission efficiency of the first optical thin film is smaller on the longer wavelength side than on the shorter wavelength side within the wavelength variation range of the light source, the amount of light guided to the monitor element by the first optical element changes. Since the reflection efficiency of the second optical thin film is larger on the long wavelength side than on the short wavelength side, the change in the amount of light is corrected. Conversely, when the transmission efficiency of the first optical thin film is larger on the long wavelength side than on the short wavelength side, the change in light quantity is corrected by the fact that the reflection efficiency of the second optical thin film is smaller on the long wavelength side than on the short wavelength side. Is done.

The first optical element and the second optical element may be optical thin films having the same composition. The optical thin film that can be used as the first optical element and the second optical element is composed of two or more kinds of dielectric multilayer films as in the optical thin film used for the second optical element, but includes TiO ₂ and SiO ₂ . A configuration with a combination of The thickness and the number of layers can be selected so that desired optical properties can be obtained.

In one embodiment, the optical thin film having the same composition transmits most of light incident at an incident angle θ ₁ (for example, 45 °) at the wavelength of the laser light used as the light source, and the rest An optical thin film that reflects and changes the amount of reflected light due to wavelength fluctuations of incident light, and further changes the amount of light by transmitting the reflected light at an incident angle θ ₂ (for example, 0 °). is there. Here, “most” means 80% or more, preferably 85% or more, more preferably 90% or more, and still more preferably 95% or more. The wavelength of the laser light varies depending on the scene of use. The wavelength of the laser beam used as the light source of the optical pickup device is known in the art. For example, in the current commercial product standard, it is 770 to 830 nm for CD and 630 to 690 nm for DVD. It is. In the following examples, the optical pickup device of the present invention was designed by selecting wavelengths of 770 to 800 nm for CD and 650 to 670 nm for DVD, but there is no intention to limit to these. In the optical thin film of the present embodiment, the reflection efficiency at the incident angle θ ₁ is small on the long wavelength side compared to the short wavelength side, and the transmission efficiency at the incident angle θ ₂ is large on the long wavelength side compared to the short wavelength side, Conversely, the change in the amount of light is corrected by the fact that the reflection efficiency at the incident angle θ ₁ is larger on the long wavelength side than on the short wavelength side and the transmission efficiency at the incident angle θ ₂ is smaller on the long wavelength side than on the short wavelength side. .

Another embodiment of an optical thin film of the same composition reflects most of the incident light at the incident angle θ ₁ (eg, 45 °) at the wavelength of the laser light used as the light source, and transmits the remaining light. An optical thin film in which the amount of transmitted light changes due to a change in wavelength of the optical thin film, and the change in the amount of light is corrected by further reflecting the transmitted light at an incident angle θ ₂ (for example, 45 °). In the optical thin film of the present embodiment, the transmission efficiency of the incident angle θ ₁ is small on the long wavelength side compared to the short wavelength side, and the reflection efficiency of the incident angle θ ₂ is large on the long wavelength side compared to the short wavelength side, Inversely, the transmission efficiency at the incident angle θ ₁ is larger on the longer wavelength side than on the short wavelength side, and the reflection efficiency at the incident angle θ ₂ is smaller on the long wavelength side than on the short wavelength side, thereby correcting the change in light amount. .

Yet another embodiment of an optical thin film of the same composition reflects most of the incident light at the incident angle θ ₁ (eg, 45 °) at the wavelength of the laser light used as the light source, transmits the rest, and enters It is an optical thin film in which the amount of transmitted light changes due to the wavelength variation of light, and the optical thin film in which the change in the amount of light is corrected by further transmitting the transmitted light at an incident angle θ ₂ (for example, 0 °). In the optical thin film of the present embodiment, the transmission efficiency at the incident angle θ ₁ is small on the long wavelength side compared to the short wavelength side, and the transmission efficiency at the incident angle θ ₂ is large on the long wavelength side compared to the short wavelength side, Conversely, the change in the amount of light is corrected by the fact that the transmission efficiency at the incident angle θ ₁ is larger on the long wavelength side than on the short wavelength side and the transmission efficiency at the incident angle θ ₂ is smaller on the long wavelength side than on the short wavelength side. .

  The first optical element and the second optical element may be integrated into one member. For example, when the first optical element is a wavelength selective film of a beam splitter, the second optical element may be provided on the surface from which light guided to the monitor element through the wavelength selective film is transmitted or emitted from the prism. Good. Alternatively, when the first optical element is a mirror film of a rising mirror, the second optical element may be provided on a surface on the rising mirror through which light that passes through the mirror film and is guided to the monitor element passes. Good.

  The second optical element may be a diffractive element. In this case, the grating pitch and groove depth are appropriately set so that the change in the amount of light guided to the monitor element by the first optical element due to the wavelength variation of the light source can be corrected using the change in the diffraction angle and the diffraction efficiency due to the wavelength. design.

  According to the present invention, there is provided an optical pickup device capable of stably controlling a light beam focused on an optical disk even when the wavelength of the light beam emitted from the semiconductor laser element is fluctuated due to a change in ambient temperature or the like. It becomes possible to do. In addition, when an optical thin film is used as the light quantity correction element (second optical element), the optical pickup apparatus of the present invention does not require a large space in the apparatus for this element. When the optical element (first optical element; for example, a rising mirror or a beam splitter) already used in the conventional optical pickup apparatus is integrated into one member, the size and / or component layout of the apparatus is conventional. Since there is almost no need to change the design, it can be manufactured compactly at low cost without requiring major changes in design.

  The optical pickup device of the present invention will be described below with reference to the drawings.

  1 and 2 are configuration diagrams of one embodiment of an optical pickup device of the present invention.

  Reference numerals 1 and 2 denote first and second light emitting / receiving units (laser light source and light receiving element) each including a semiconductor laser element and a photodetector, 3 a beam splitter, 4 a collimating lens, 5 a rising mirror, and 6 an objective lens , 7 is an optical disk, 8 is a front monitor element, 9 is an aperture limit, and 10 is a half-wave plate.

  The optical disk 7 corresponds to DVD and CD having different substrate thicknesses, the first light receiving / emitting unit 1 is for reproducing a DVD, and the second light emitting / receiving unit 2 is for recording, reproducing and erasing a CD. .

  The beam splitter 3 includes a wavelength selection film 3a as a first optical element and a correction film (compensation film) 3b as a second optical element. The correction film 3b is provided on the optical path from the wavelength selection film to the front monitor element. The correction film 3b has a transmission characteristic opposite to the reflectance variation due to the wavelength of the wavelength selection film 3a. That is, when the reflectance of the wavelength selective film 3a is larger on the long wavelength side than on the short wavelength side, the transmittance of the correction film 3b is smaller on the long wavelength side than on the short wavelength side (of course, the wavelength selective film 3a The magnitude relationship between the reflectance and the transmittance of the correction film 3b may be reversed between the short wavelength side and the long wavelength side).

  The light beam 11 emitted from the first light emitting / receiving unit 1 has a plane of polarization rotated by 90 ° by the half-wave plate 10, enters the beam splitter 3 as S-polarized light, is reflected by the wavelength selection film 3 a, and is collimated. 4 makes it substantially parallel. The substantially parallel light beam 11 is focused on the optical disk 7 (in this case, DVD) by the objective lens 5. Then, the light is reflected by the optical disk 7, passes through the objective lens 5 and the collimating lens 4, is reflected by the beam splitter 3, and returns to the first light emitting / receiving unit 1. The returned light beam 11 is guided to the light receiving element in the first light receiving and emitting unit 1.

  The light beam 12 emitted from the second light emitting / receiving unit 2 is incident on the beam splitter 3 with P-polarized light, is incident on the wavelength selection film 3 a of the beam splitter 3 at 45 °, is transmitted through the film, and is collimated by the collimating lens 4. It becomes almost parallel. The light beam 9 which has become substantially parallel is condensed on the optical disk 7 (in this case, CD) by the objective lens 5. Then, the light is reflected by the optical disc 7, passes through the objective lens 5 and the collimating lens 4, passes through the beam splitter 3, returns to the second light receiving / emitting unit 2, and is guided to the light receiving element in the second light receiving / emitting unit 2.

  The wavelength selection film 3a of the beam splitter 3 has a function of selectively transmitting and reflecting the light beam according to the wavelength of the above-described light beam, and simultaneously transmits a part of the light beam 13 of the light beam 12 from the second light emitting / receiving unit 2. Reflect. The reflected light 13 enters the correction film 3 b at 0 °, and after passing through the film, the light beam is narrowed by the aperture limit 9 and is incident on the front monitor element 8.

  The front monitor element 8 outputs an electrical signal corresponding to the amount of light of the incident light beam 13. Since the electrical signal output from the front monitor element 8 and the light beam collected on the optical disc 7 are in a substantially proportional relationship, the light beam condensed on the optical disc 7 with reference to the electrical signal output has an appropriate intensity. Thus, the drive current of the semiconductor laser element in the second light emitting / receiving unit 2 is controlled.

  In the wavelength selection film 3a, the reflectivity (only a few percent) varies depending on the wavelength within the wavelength variation range of the laser light emitted from the semiconductor laser element, so the wavelength of the semiconductor laser element varies due to a temperature change or the like. Then, the amount of light guided to the front monitor element 8 by the wavelength selection film 3a changes. However, since the correction film 3b provided on the optical path has a characteristic opposite to the reflectance variation due to the wavelength of the wavelength selection film 3a as described above, the light emitted from the semiconductor laser element is reflected by the wavelength selection film 3a and the wavelength selection film 3a. The transmission efficiency until the light enters the front monitor element through the correction film 3b changes less with respect to the wavelength variation than before the correction film 3b is inserted, and enters the front monitor element 8 even if the wavelength of the semiconductor laser element fluctuates. The light intensity is stable. In other words, the correction film 3b corrects a change caused by wavelength variation of the light source in the amount of light guided to the monitor element by the wavelength selection film 3a.

  In another embodiment of the optical pickup device of the present invention, the transmitted light of the mirror film 5a as the first optical element of the rising mirror 5 is reflected by the correction film (compensation film) 5b as the second optical element, and the front monitor is used. The light is made incident on the element (FIG. 10) or transmitted through the correction film 5b and made incident on the front monitor element (FIG. 11). In this case, the correction film 5b is provided to face the mirror film 5a. The correction film 5b may be provided as a single member on the surface of the rising mirror 5 that faces the mirror film 5a.

  When the optical thin film having the same configuration is used as the mirror film 5a and the correction film 5b, the incident angle to the mirror film and the incident angle to the correction film may be changed.

  There may be a case where the wavelength dependence of the diffraction grating is used without using the second optical element as an optical thin film. In this case, the grating pitch and groove depth are appropriately designed, and the diffraction angle change and diffraction efficiency change depending on the wavelength are used.

  In the above embodiment, DVD playback and CD recording have been described as examples. However, the present invention can be similarly applied to DVD recording, BD of next-generation optical disc, HD-DVD, and the like.

  In the pickup device of the present invention shown in FIGS. 1 and 2, an optical thin film having the same configuration as that of the wavelength selection film 3a is used as the correction film 3b. The film configuration is shown in FIG.

  This optical thin film has an optical characteristic that works as a correction film when the reflected light is transmitted at an incident angle of 0 ° with respect to the light reflected and incident at an incident angle of 45 ° using the film as a wavelength selection film. FIG. 4 shows the reflectance and transmittance of 45 ° incident light of this optical thin film. Since the light incident and reflected on this film at 45 ° is guided to the front monitor element, the reflection efficiency is enlarged for the wavelength variation range of the light beam of the second light emitting / receiving unit 2 and shown in FIG.

  As shown in FIG. 5, the reflectance of the wavelength selection film 3a varies depending on the wavelength, and the amount of light guided to the front monitor element 8 varies when the wavelength of the semiconductor laser element varies with temperature or the like.

  The transmission efficiency at 0 ° incidence of the same optical thin film is shown in FIG. This transmission characteristic is used as the correction film 3b.

  FIG. 7 shows the incident light on the front monitor element when the optical thin film is used only as the wavelength selection film 3a and no correction film is provided, and when the optical thin film is used as the wavelength selection film 3a and the correction film 3b. Indicates the amount of light. At this time, the light beam 12 from the second light emitting / receiving unit 2 is incident on the optical thin film serving as the wavelength selection film 3a by 45 ° and reflected to enter the front monitor element, or the light reflected from the wavelength selection film 3a. Enters the optical thin film as the correction film 3b at 0 °, passes therethrough, and enters the front monitor element.

  As shown in FIG. 7, when the light beam emitted from the semiconductor laser element 2 fluctuates between 775 nm and 800 nm, the amount of light reflected from the wavelength selection film 3a and incident on the front monitor element 10 is 2.5 to 3.5. However, the amount of light incident on the front monitor element 8 after passing through the correction film 3b after being reflected by the wavelength selection film 3a changes only from 2.1 to 2.4. (14%), the change in the light amount is corrected (the change rate of the light amount is reduced to 40% or less before the correction).

  Thus, in the optical pickup device of the present invention, the amount of light incident on the front monitor element 8 is stabilized with respect to the wavelength variation of the semiconductor laser element.

  In the above embodiment, the wavelength selection film 3a and the correction film 3b are made of optical thin films having the same composition, but the correction film 3b has a characteristic that is opposite to the reflectance variation due to the wavelength of the wavelength selection film 3a. If it is possible to correct the change due to the wavelength variation of the light source of the light amount guided to the front monitor element by the wavelength selection film 3a, it is not necessary to have the same composition as the wavelength selection film 3a.

  The above embodiments and examples are described as examples for facilitating the understanding of the present invention, and the present invention is limited to the specific configurations and arrangements described in this specification or the accompanying drawings. It should be noted that it is not limited. Those skilled in the art will recognize that the specific configurations, means, methods, and apparatus described herein can be replaced with many others known in the art without departing from the spirit and scope of the present invention. Should be understood and easily recognized.

  For example, the present invention can be generally applied when it is necessary to monitor the amount of laser light emitted from a light source in order to achieve accurate measurement in a measurement system that uses laser light. Applications are expected when the size of the device is limited or when manufacturing at low cost is required.

  In this case, the measuring device has a laser light source that emits light for irradiating the measurement object, a light receiving element that receives light reflected by the measurement object, and a monitor for monitoring the amount of light emitted from the light source. A first optical element that is present in the optical path from the light source to the measurement object and that directs a part of the light from the light source to the monitor element and guides the remainder to the measurement object; and from the first optical element to the monitor element A second optical element existing in the optical path, and the second optical element corrects the change in the amount of light when the amount of light guided to the monitor element by the first optical element changes due to wavelength variation of the light source. .

1 is a structural diagram (top view) of an embodiment of an optical pickup device of the present invention. It is a side view of the optical pick-up apparatus shown in FIG. 4 is a table showing one example of a film configuration of an optical thin film that can be used as a wavelength selection film (first optical element) and a correction film (second optical element) in the optical pickup device of the present invention. FIG. 4 is a graph showing reflection efficiency and transmission efficiency at 45 ° incidence of the optical thin film whose film configuration is shown in FIG. 3. In the optical pickup device of the present invention, this wavelength characteristic is used as a wavelength selection film (first optical element). It is the figure which expanded the reflection efficiency shown in FIG. 4 in the fluctuation range of a laser beam wavelength. It is a graph which shows the transmission efficiency at the time of 0 degree incidence of the optical thin film which showed the film | membrane structure in FIG. In the pickup device of the present invention, this transmission characteristic is used as a correction film (second optical element). In the optical pickup device, when the optical thin film whose film configuration is shown in FIG. 3 is used only as a wavelength selection film and no correction film is provided (conventional device), and when used as a wavelength selection film and a correction film (device of the present invention) These are graphs comparing the amount of light incident on the front monitor element within the fluctuation range of the laser light wavelength. It is a block diagram of another embodiment of the optical pick-up apparatus of this invention. In this configuration, light that has passed through the mirror film of the rising mirror is reflected by the correction film and is incident on the front monitor element. It is a block diagram of further another embodiment of the optical pickup of the present invention. In this configuration, light that has passed through the mirror film of the rising mirror passes through the correction film and enters the front monitor element. It is a structural view (top view) of a conventional optical pickup device. It is a side view of the optical pick-up apparatus shown in FIG.

Explanation of symbols

1 First light emitting / receiving unit (laser light source and light receiving element)
2 Second light emitting / receiving unit (laser light source and light receiving element)
3 Beam splitter 3a Wavelength selection film formed on the beam splitter 3b Correction film (compensation film) formed on the beam splitter
4 Collimating lens 5 Rising mirror 5a Mirror film formed on the rising mirror 5b Correction film (compensation film) formed on the rising mirror
6 Objective lens 7 Optical disk 8 Front monitor element 9 Aperture limit 10 1/2 wavelength plate

Claims (6)

A laser light source that emits light for irradiating an optical disk, a light receiving element that receives light reflected on the optical disk, a monitor element for monitoring the amount of light emitted from the light source, and an optical path from the light source to the optical disk A first optical element that guides part of the light from the light source to the monitor element and guides the rest to the optical disc, and a second optical element that exists in the optical path from the first optical element to the monitor element,
An optical pickup device in which a second optical element corrects a change in the amount of light when the amount of light guided to the monitor element by the first optical element changes due to wavelength variation of the light source. The optical pickup device according to claim 1, wherein the first optical element and the second optical element are optical thin films. The second optical element is an optical thin film that reflects or transmits light from the first optical element to the monitor element, and the reflection or transmission efficiency is changed according to the wavelength variation of the light source. Optical pickup device. The optical pickup device according to claim 1, wherein the first optical element and the second optical element are optical thin films having the same composition. The optical pickup device according to claim 1, wherein the first optical element and the second optical element are integrated into one member. The optical pickup device according to claim 1, wherein the second optical element is a diffraction element.

Images