Optical system device

Abstract

The purpose of the present invention is to provide an optical system device capable of detecting abnormality such as breakage of an optical element. This optical system device is formed so as to comprise: an optical element 1 comprising a first surface 11 and a second surface 12, and having a functional surface that exerts an optical function on at least one of the first surface 11 and the second surface 12; a housing part 2 that forms a housing 20 together with the optical element 1; a main light irradiation unit 3 disposed in the housing 20 and having a light source for irradiating the first surface 11 of the optical element 1 with main light; a sub-light irradiation unit 4 having a light source for irradiating the optical element 1 with sub-light having a wavelength different from that of the main light; and a light detection means 5 for detecting light transmitted through or reflected by the optical element 1.

Description

optical system equipment

[0001] The present invention relates to an optical system device.

[0002] In recent years, three-dimensional measurement sensors using the time-of-flight (TOF) method have been adopted in mobile devices, cars, robots, etc. This method measures the distance to an object from the time it takes for light irradiated from a light source onto the object to be reflected and return. If the light from the light source is irradiated uniformly over a predetermined area of ​​the object, the distance at each irradiated point can be measured, and the three-dimensional structure of the object can be detected.

[0003] The optical system device comprises an irradiation unit that irradiates light, an optical element that controls the light from the irradiation unit to a predetermined light distribution, a camera unit that detects light reflected from each point on the object, and a calculation unit that calculates the distance to the object from the signal received by the camera unit.

[0004] The optical element used is a microlens array that irradiates diffused light or dot light by devising a lens arrangement (see, for example, Patent Documents 1 and 2). The illumination unit, camera unit, and calculation unit use existing VCSELs, CMOS imagers, CPUs, etc.

[0005] Furthermore, in such optical devices, when the light from the irradiating section is strong, such as in the case of a VCSEL, if the light is irradiated directly onto the eyes, there is a risk of blindness or other problems, so the device is packaged to prevent the light from leaking directly to the outside.

[0006] Patent Publication No. 2006-500621 International Publication No. 2023 / 26987

[0007] However, even if the optical device is packaged, there is a risk that light from the irradiating unit may leak outside if the optical element is damaged, deformed, peeled off, or otherwise abnormal. In particular, when the optical device is used as a sensor for eye tracking, which detects the position of a person's pupils and tracks what the person is looking at in real time, detecting abnormalities in the optical element is an essential issue.

[0008] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an optical system device that can detect abnormalities such as breakage of optical elements.

[0009] In order to achieve the above object, the optical system device of the present invention is characterized by comprising: an optical element consisting of a first surface and a second surface, and having a functional surface on at least one of the first surface and the second surface that exhibits an optical function; a housing portion that forms a housing together with the optical element; a main light irradiation portion that is arranged within the housing and has a light source that irradiates the first surface of the optical element with main light; a secondary light irradiation portion that has a light source that irradiates the optical element with secondary light of a wavelength different from the main light; and a light detection means that detects light transmitted through or reflected by the optical element.

[0010] Here, the secondary light irradiating section may irradiate the secondary light onto the first surface or the second surface of the optical element.

[0011] The optical element may further include a light-shielding portion on the first or second surface that transmits the primary light and blocks the secondary light. In this case, it is preferable that the secondary light irradiating portion irradiates the first surface of the optical element with secondary light that is visible light.

[0012] The light detecting means may detect light that has propagated between the first surface and the second surface of the optical element.

[0013] The optical element may have a waveguide layer on the first surface or the second surface, through which at least one of the primary light and the secondary light propagates, and the light detecting means may detect the light propagated through the waveguide layer.

[0014] The light detecting means may transmit the main light and may be disposed on the optical axis of the main light irradiating section.

[0015] The optical system may further include a determination means for determining an abnormality of the optical element based on a change in the amount of light detected by the light detection means. In this case, the determination means may determine an abnormality of the optical element from a change in the amount of the secondary light detected by the light detection means. The determination means may also determine an abnormality of the optical element from a change in the amount of the primary light detected by the light detection means. The determination means may also determine an abnormality of the optical element from a change in the integrated value of the amount of the secondary light detected by the light detection means. The determination means may also determine an abnormality of the optical element from a change in the integrated value of the amount of the primary light detected by the light detection means. The determination means may also determine an abnormality of the optical element from a change in the ratio of the amount of light of the primary light to the amount of the secondary light detected by the light detection means.

[0016] The determination means may determine an abnormality in the main light irradiating unit from a change in the light intensity of the main light detected by the light detection means. The determination means may determine an abnormality in the main light irradiating unit from a change in the integrated value of the light intensity of the main light detected by the light detection means. The determination means may determine an abnormality in the main light irradiating unit from a change in the ratio of the light intensities of the main light and the secondary light detected by the light detection means.

[0017] The optical system may further comprise a main light irradiator disconnecting means for disconnecting a lighting circuit for a light source of the main light irradiator when the determining means determines that the optical element is abnormal.

[0018] The optical system device of the present invention can easily detect abnormalities in optical elements by utilizing the light from the secondary light irradiating section.

[0019] FIG. 1 is a schematic cross-sectional view showing an optical system device of the present invention in which a light detection means is inside a housing; FIG. 2 is a schematic cross-sectional view showing an optical system device of the present invention in which a light detection means is outside a housing; FIG. 3 is a schematic cross-sectional view showing an optical system device of the present invention in which a light detection means detects light that has propagated inside an optical element; FIG. 4 is a schematic cross-sectional view showing an optical system device of the present invention in which a light detection means detects light that has propagated inside a waveguiding layer; and FIG. 5 is a schematic cross-sectional view showing an optical system device of the present invention in which a light detection means is on the optical axis of a main light irradiation part.

[0020] The optical system device of the present invention will be described below. As shown in Figures 1 to 5, the optical system device of the present invention is mainly composed of an optical element 1, a housing 2, a main light irradiating section 3 that irradiates main light, a secondary light irradiating section 4 that irradiates secondary light, and a light detecting means 5 that detects light. The optical system device can detect abnormalities in the optical element 1. Here, in this specification, abnormalities in the optical element 1 refer to those that cause leakage of main light to the outside of the housing 20, such as breakage, deformation, or peeling of the optical element 1.

[0021] As shown in FIG. 1 , the optical element 1 comprises a first surface 11 and a second surface 12, and at least one of the first surface 11 and the second surface 12 has a functional surface that exhibits an optical function. The functional surface is preferably formed on the first surface side. The functional surface may be any surface that can control the main light from the main light irradiation unit 3 and irradiate a predetermined area. For example, the functional surface may be one that controls the transmitted main light to form a dot pattern or one that forms diffused light. An example of the functional surface is a concave-convex shape such as a microlens array.

[0022] Furthermore, the optical element 1 may be provided with a light-shielding portion 8 on the first surface 11 or the second surface 12 that transmits the primary light and blocks the secondary light. This makes it possible to prevent the secondary light from passing through the optical element 1 and leaking. The light-shielding portion 8 may be a band-pass filter or the like that transmits the primary light and blocks the secondary light.

[0023] As shown in FIG. 1 , the housing 2 constitutes a housing together with the optical element 1. The housing contains at least the main light irradiator 3 and is configured to prevent light from the main light irradiator 3 from leaking directly to the outside. The housing may also contain the secondary light irradiator 4, the light detection means 5, etc. The housing is configured so that the first surface 11 of the optical element 1 faces the inside of the housing and the second surface 12 faces the outside of the housing. The shape of the housing 2 may be any shape as long as it can contain the main light irradiator 3, the secondary light irradiator 4, the light detection means 5, etc. For example, it may be formed into a bottomed cylindrical shape with an opening that can be closed by the optical element 1. The main light irradiator 3, the secondary light irradiator 4, the light detection means 5, etc. can be fixed to the bottom of the housing 2. The bottom may be flat, or may have a concave groove formed therein so that the main light irradiator 3, the secondary light irradiator 4, the light detection means 5, etc. can be embedded. The fixing method may be a general method such as fixing the main light irradiation unit 3, the sub light irradiation unit 4, the light detection means 5, etc. to the bottom with adhesive. The housing 2 may be made of a well-known material, but preferably is made of a material that is less susceptible to deformation due to the surrounding environment. The housing 2 may be formed as a single unit or may be composed of multiple members.

[0024] The main light irradiating unit 3 includes a light source that irradiates the first surface 11 of the optical element 1 with main light. Therefore, the main light irradiating unit 3 is disposed inside the housing. The main light irradiating unit 3 may be any type of unit that includes a light source that irradiates the optical element 1 with main light of a predetermined wavelength. The main light irradiating unit 3 may include a single light source or multiple light sources. Alternatively, multiple light sources may be formed by passing light from a single light source through an aperture having multiple small holes. When the irradiating unit is configured with multiple light sources, it is preferable that the light sources are formed on the same plane. The surface from which light is emitted by the irradiating unit 1 is referred to as the irradiating surface. A specific example of the irradiating unit 1 is a VCSEL (Vertical Cavity Surface Emitting Laser), which is expected to achieve high output with low power consumption. VCSELs include single-emitter VCSELs, which have one light source 10 that can irradiate light perpendicular to the light-emitting surface, and multi-emitter VCSELs, which have multiple light sources 10.

[0025] The secondary light irradiator 4 has a light source that irradiates the optical element 1 with secondary light having a wavelength different from that of the primary light. The secondary light irradiator 4 may be any light source that irradiates the optical element 1 with secondary light having a wavelength different from that of the primary light. However, considering eye safety, it is preferable that the secondary light irradiator 4 irradiates visible light or secondary light having a wavelength longer than that of visible light. The secondary light irradiator 4 may have a single light source or multiple light sources. A specific example of the secondary light irradiator 4 is an LED (Light Emitting Diode), which is expected to consume little power. The secondary light irradiator 4 may irradiate the secondary light onto either the first surface 11 or the second surface 12 of the optical element 1. The secondary light irradiator 4 may be disposed inside the housing, as shown in FIGS. 1( a) and 2(a), or outside the housing, as shown in FIGS. 1( a) and 2(b). When the secondary light irradiation unit 4 is arranged on the outside of the housing, a member that serves as a waveguide through which the secondary light of the secondary light irradiation unit 4 can propagate can be arranged, for example, on the second surface 12 side of the optical element 1, and the light that propagates through the waveguide can be irradiated onto the second surface 12 of the optical element 1.

[0026] When the above-mentioned light-shielding portion 8 is provided on the first surface 11 or the second surface 12 of the optical element 1, it is preferable to place the secondary light irradiating portion 4, which irradiates the secondary light, which is visible light, inside the housing. With this configuration, if an abnormality such as breakage occurs in the optical element 1, visible light will leak from the optical element. Therefore, there is an advantage that the presence or absence of an abnormality in the optical element 1 can be detected not only by the light detecting means 5 but also by visually checking the leaked visible light.

[0027] The light detection means 5 detects light transmitted through or reflected by the optical element 1. The light detection means 5 may be any means capable of detecting light transmitted through or reflected by the optical element 1. For example, a photodiode capable of detecting a change in the amount of light as a change in current may be used. The light detection means 5 may be one that detects only the secondary light, or one that detects both the primary and secondary light. Furthermore, depending on the configuration of the optical system device, even one that detects only the primary light may be able to detect an abnormality in the optical element.

[0028] The light detection means 5 may be disposed inside the housing as shown in FIG. 1 , or outside the housing as shown in FIG. 2 . When the light detection means 5 is disposed inside the housing, it is disposed so as not to interfere with the irradiation of the optical element 1 with the primary light from the primary light irradiator 3. When the light detection means 5 is disposed outside the housing, it is disposed in a position so as not to interfere with the primary light from the primary light irradiator 3 being controlled by the optical element 1 and irradiated to a predetermined area. In this case, for example, a member serving as a waveguide through which the primary light and secondary light can propagate may be disposed on the second surface 12 of the optical element 1, and the light detection means 5 may detect the light propagated through the waveguide. The light detection means 5 may also be transparent to the primary light. In this case, the light detection means 5 detects the secondary light. In this case, the light detection means 5 may be disposed on the optical axis of the primary light irradiator 3 as shown in FIG. 3 . This allows reliable detection even if an abnormality such as breakage occurs in the optical element 1 on the optical axis of the primary light irradiator 3.

[0029] When the auxiliary light irradiating unit 4 is arranged on the inside of the housing, the light detecting means 5 is arranged on the inside of the housing to detect the auxiliary light reflected by the optical element 1, as shown in FIG. 1( a), and the light detecting means 5 is arranged on the outside of the housing to detect the auxiliary light transmitted through the optical element 1, as shown in FIG. 2( a). When the auxiliary light irradiating unit 4 is arranged on the outside of the housing, the light detecting means 5 is arranged on the inside of the housing to detect the auxiliary light transmitted through the optical element 1, as shown in FIG. 1( b), and the light detecting means 5 is arranged on the outside of the housing to detect the auxiliary light reflected by the optical element 1, as shown in FIG. 2( b). It is also possible to arrange the light detecting means 5 on both the inside and outside of the housing. In this case, regardless of whether the auxiliary light irradiating unit 4 is arranged on the inside or outside of the housing, both the auxiliary light transmitted through the optical element 1 and the auxiliary light reflected by the optical element 1 can be detected.

[0030] The light detection means 5 can also be configured to detect the main light from the main light irradiator 3. When the light detection means 5 is arranged inside the housing, the light detection means 5 can detect the main light from the main light irradiator 3 that has been reflected by the optical element 1. When the light detection means 5 is arranged outside the housing, the light detection means 5 can detect the main light from the main light irradiator 3 that has passed through the optical element 1. When the light detection means 5 is arranged both inside and outside the housing, it can detect both the main light that has passed through the optical element 1 and the main light that has been reflected by the optical element 1.

[0031] The light detection means 5 can also be configured to detect both the main light from the main light irradiating unit 3 and the secondary light from the secondary light irradiating unit 4. This makes it possible to detect the ratio of the light intensity of the main light to the secondary light and its changes.

[0032] Furthermore, as shown in FIG. 4 , the light detection means 5 may detect light propagated between the first surface 11 and the second surface 12 of the optical element 1. In this case, the light detection means 5 may detect the propagated primary light, the secondary light, or both the primary light and the secondary light. Furthermore, the propagation of light within the optical element 1 can be facilitated by coating the surface of the optical element 1 with a material having a higher refractive index than the material of the optical element 1 or by forming a concave-convex pattern such as a diffraction grating or prism at a predetermined location on the surface of the optical element 1. The light detection means 5 may be disposed on a side surface connecting the first surface 11 and the second surface 12 of the optical element 1. Alternatively, the light detection means 5 may be disposed on the first surface 11 or the second surface 12 of the optical element 1. In this case, a concave-convex pattern such as a diffraction grating or prism that diffracts or reflects light to the outside may be formed on the first surface 11 or the second surface 12 of the optical element 1 so that the light propagated within the optical element 1 can be extracted, and the light detection means 5 may be disposed at this position.

[0033] 5, the optical element 1 may also have a waveguide layer formed on the first surface 11 or the second surface 12, which allows at least one of the primary light and the secondary light to propagate therein. The light detecting means 5 is configured to detect light that has propagated through the waveguide layer. The light detecting means 5 may be disposed on a side surface of the waveguide layer. Alternatively, the light detecting means 5 may be disposed on the surface of the waveguide layer. In this case, a concave-convex pattern such as a diffraction grating or prism that diffracts or reflects light to the outside may be formed on the surface of the waveguide layer, so that the light that has propagated through the waveguide layer can be extracted, and the light detecting means 5 may be disposed at this position.

[0034] The optical system device of the present invention may further include a determination means 6 that determines whether there is an abnormality in the optical element 1 based on a change in the amount of light detected by the light detection means 5. The determination means 5 may be any means that can determine whether there is an abnormality in the optical element 1. For example, a CPU that can perform calculations and data processing based on changes in the amount of light detected by the light detection means 5, or a processing unit such as a computer using such a CPU, may be used.

[0035] The determination means 5 may use any method as long as it can determine an abnormality in the optical element 1. For example, the determination means may determine an abnormality in the optical element 1 from a change in the amount of secondary light or its integrated value detected by the light detection means 5, or a change in the ratio of the amount of primary light to the amount of secondary light. The change may be an increase or a decrease.

[0036] For example, consider a case where an abnormality such as breakage occurs in the optical element 1, causing an increase in the amount of secondary light transmitted through the optical element 1 and a decrease in the amount of reflected secondary light. At this time, if the light detection means 5 detects reflected secondary light by the optical element 1, the amount of secondary light decreases. On the other hand, if the light detection means 5 detects transmitted secondary light by the optical element 1, the amount of secondary light increases. Therefore, the determination means 5 can determine an abnormality in the optical element 1 from the decrease or increase in the amount of secondary light. The determination means 5 may, for example, determine a threshold value such as a minimum or maximum value for the amount of secondary light in advance, and determine that there is an abnormality in the optical element 1 if the threshold value is exceeded.

[0037] If the light detection means 5 detects the main light, the determination means can also determine an abnormality in the optical element 1 from a change in the amount of the main light detected by the light detection means 5. For example, consider a case where an abnormality such as breakage occurs in the optical element 1, causing an increase in the amount of the main light passing through the optical element 1 and a decrease in the amount of the reflected secondary light. At this time, if the light detection means 5 detects the reflected light of the main light by the optical element 1, the amount of the main light decreases. On the other hand, if the light detection means 5 detects the transmitted light of the main light by the optical element 1, the amount of the main light increases. Therefore, the determination means 5 can determine an abnormality in the optical element 1 from the decrease or increase in the amount of the main light. For example, the determination means 5 may determine a threshold value, such as a minimum or maximum value of the amount of the main light, in advance, and determine that an abnormality exists in the optical element 1 if the amount of the main light exceeds the threshold value.

[0038] Furthermore, there may be cases where an abnormality such as breakage of the optical element 1 is minor and the change in the light intensity is small. In such cases, it may be impossible to determine whether the optical element 1 is abnormal based solely on the change in the light intensity of the secondary light detected by the light detection means 5. Therefore, the determination means may determine whether the optical element 1 is abnormal based on a change in the integrated value of the light intensity of the secondary light detected by the light detection means 5. For example, consider a case where an abnormality such as breakage occurs in the optical element 1, causing an increase in the amount of secondary light transmitted through the optical element 1 and a decrease in the amount of reflected secondary light. At this time, if the light detection means 5 detects the secondary light reflected by the optical element 1, the integrated value of the light intensity of the secondary light decreases. On the other hand, if the light detection means 5 detects the secondary light transmitted by the optical element 1, the integrated value of the light intensity of the secondary light increases. Therefore, the determination means 5 can determine whether the optical element 1 is abnormal based on a decrease or increase in the integrated value of the light intensity of the secondary light. For example, the determination means 5 may determine a threshold value, such as a minimum or maximum value, of the integrated value of the light intensity of the secondary light in advance, and determine that the optical element 1 is abnormal if the threshold value is exceeded. This allows the determination means to determine even minor abnormalities in the optical element 1. The integrated value is expressed as the product of the amount of light and time, and this time can be set arbitrarily. However, the longer the time, the more easily minor abnormalities in the optical element 1 can be determined, but the longer it takes to make the determination. Conversely, the shorter the time, the quicker the determination can be made, but it becomes more difficult to determine minor abnormalities. Therefore, the time must be set appropriately depending on the application of the optical device. In consideration of eye protection, it is preferable that this time be at least equal to or shorter than the time that will not cause visual impairment even if the light from the main light irradiating unit 3 is directly irradiated onto the eyes.

[0039] If the light detection means 5 detects the main light, the determination means can also determine an abnormality in the optical element 1 from a change in the integrated value of the light intensity of the main light detected by the light detection means 5. For example, consider a case where an abnormality such as breakage occurs in the optical element 1, causing an increase in the amount of main light passing through the optical element 1 and a decrease in the amount of reflected secondary light. At this time, if the light detection means 5 detects the reflected light of the main light from the optical element 1, the integrated value of the light intensity of the main light decreases. On the other hand, if the light detection means 5 detects the transmitted light of the main light from the optical element 1, the integrated value of the light intensity of the main light increases. Therefore, the determination means 5 can determine an abnormality in the optical element 1 from a decrease or increase in the integrated value of the light intensity of the main light. For example, the determination means 5 may determine a threshold value, such as a minimum or maximum value, of the integrated value of the light intensity of the main light in advance, and determine that an abnormality exists in the optical element 1 if the integrated value exceeds the threshold value. This allows the determination means to determine even minor abnormalities in the optical element 1. The integrated value is expressed as the product of the light intensity and time, but the time can be determined arbitrarily. However, the longer the time, the easier it is to detect minor abnormalities in the optical element 1, but the longer it takes to make the determination. Conversely, the shorter the time, the quicker it is to make the determination, but the more difficult it becomes to detect minor abnormalities. Therefore, it is necessary to set the time appropriately depending on the application of the optical device. In consideration of eye protection, it is preferable that the time be at least equal to or shorter than the time that will not cause visual impairment even if the light from the main light irradiator 3 is directly irradiated onto the eyes.

[0040] The determination means can also determine an abnormality in the optical element 1 from a change in the ratio of the light intensity of the primary light to the secondary light detected by the light detection means 5. The determination means 5 may, for example, determine in advance a threshold value such as a minimum or maximum value for the ratio B / A of the light intensity B of the secondary light to the light intensity A of the primary light, and determine that there is an abnormality in the optical element 1 when the ratio exceeds the threshold value. In this way, the determination means can determine an abnormality in the optical element 1.

[0041] The determination means can also determine an abnormality in the main light irradiating unit 3 based on a change in the amount of primary light or its integrated value detected by the light detection means 5, or a change in the ratio of the amount of primary light to the amount of secondary light. The change may be an increase or a decrease. In this specification, an abnormality in the main light irradiating unit 3 refers to deterioration or a malfunction of the main light irradiating unit 3. For example, if the amount of light in the main light irradiating unit 3 decreases due to deterioration, the amount of primary light and its integrated value detected by the light detection means 5 will decrease. The ratio B / A of secondary light to primary light will also decrease. Therefore, the determination means 5 can determine deterioration of the main light irradiating unit 3 based on a decrease in the amount of light or its integrated value, a decrease in the ratio B / A of secondary light to primary light, or the like. The determination means 5 may, for example, determine thresholds in advance for the amount of primary light, its integrated value, the minimum and maximum values ​​of the ratio B / A of secondary light to primary light, etc., and determine that an abnormality exists in the main light irradiating unit 3 if the values ​​exceed these thresholds.

[0042] The optical system device of the present invention may further include a main light irradiator disconnection means that disconnects the lighting circuit of the light source of the main light irradiator 3 when the determination means determines that there is an abnormality in the optical element 1. This allows the lighting of the main light irradiator to be stopped quickly when an abnormality is determined in the optical element 1, thereby preventing risks such as blindness. The lighting circuit may be disconnected in any way as long as it can stop the lighting of the light source of the main light irradiator 3, and may, for example, be disconnected electrically using software or physically by destroying the lighting circuit.

[0043] REFERENCE SIGNS LIST 1 Optical element 2 Housing 3 Main light irradiating section 4 Sub-light irradiating section 5 Light detecting means 6 Determining means 8 Light blocking section 11 First surface 12 Second surface 20 Housing

Claims

1. An optical system device comprising: an optical element consisting of a first surface and a second surface, with at least one of the first surface and the second surface having a functional surface that exhibits an optical function; a housing section that forms a housing together with the optical element; a main light irradiation section that is arranged within the housing and has a light source that irradiates the first surface of the optical element with main light; a secondary light irradiation section that has a light source that irradiates the optical element with secondary light of a wavelength different from the main light; and light detection means that detects light transmitted through or reflected by the optical element.

2. The optical system device according to claim 1, wherein the optical element has a light-shielding portion on the first surface or the second surface that transmits the primary light and blocks the secondary light.

3. The optical system according to claim 2, wherein the secondary light irradiating section irradiates the first surface of the optical element with secondary light that is visible light.

4. The optical system according to claim 2, wherein said secondary light irradiating section irradiates the secondary light onto the second surface of said optical element.

5. An optical system according to claim 1, wherein said light detecting means detects light that has propagated between the first surface and the second surface of said optical element.

6. An optical system device according to claim 1, characterized in that the optical element has a waveguide layer on the first surface or the second surface that propagates at least one of the primary light and the secondary light therein, and the light detection means detects the light that has propagated inside the waveguide layer.

7. An optical system according to claim 1, wherein said light detecting means transmits said main light and is disposed on the optical axis of said main light irradiating section.

8. An optical system according to any one of claims 1 to 7, further comprising a determination means for determining whether or not the optical element is abnormal based on a change in the amount of light detected by the light detection means.

9. An optical system according to claim 8, wherein said determining means determines whether or not there is an abnormality in said optical element based on a change in the amount of said secondary light detected by said light detecting means.

10. An optical system according to claim 8, wherein said determining means determines whether or not there is an abnormality in said optical element based on a change in the amount of said principal light detected by said light detecting means.

11. An optical system according to claim 8, wherein said determining means determines whether or not there is an abnormality in said optical element based on a change in the integrated value of the amount of light of said secondary light detected by said light detecting means.

12. An optical system according to claim 8, wherein said determining means determines whether or not there is an abnormality in said optical element based on a change in the integrated value of the amount of light of said principal light detected by said light detecting means.

13. An optical system according to claim 8, wherein said determining means determines whether or not there is an abnormality in said optical element based on a change in the ratio of the amount of light of said primary light to that of said secondary light detected by said light detecting means.

14. An optical system according to claim 8, wherein said determining means determines whether or not there is an abnormality in said main light irradiating section based on a change in the amount of main light detected by said light detecting means.

15. An optical system according to claim 8, wherein said determining means determines whether or not there is an abnormality in said main light irradiating section based on a change in the integrated value of the amount of main light detected by said light detecting means.

16. An optical system according to claim 8, wherein said determining means determines whether or not there is an abnormality in said main light irradiating section based on a change in the ratio of the amount of light of said main light to that of said secondary light detected by said light detecting means.

17. An optical system according to claim 8, further comprising main light irradiation unit disconnection means for disconnecting a lighting circuit for a light source of said main light irradiation unit when said determination means determines that said optical element is abnormal.

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