JP2832055B2 - Auxiliary lighting device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an auxiliary illumination device for providing a pattern image reflected by an object to, for example, a focus detection device incorporating a camera.

[Conventional technology]

In an autofocus camera or the like, even when the object to be measured has low brightness or low contrast, a subject auxiliary lighting device has been conventionally proposed in order to enable distance measurement.
For example, there is JP-A-62-247312.

However, if the projected pattern image is close to the periodic pattern, erroneous distance measurement is likely to occur, and the frequency range of the pattern is inappropriate for detection when zooming the target lens or replacing a lens with a different focal length. Costs, dimensions,
There is a possibility that extremely heavy load such as wasting of light amount may be imposed.

[Problems to be Solved by the Invention] An object of the present invention is to propose an apparatus in which the projection contrast of a light projection pattern is high and the utilization efficiency of a light source is high.

Another object is to form a light projection pattern having a complicated illuminance distribution with a simple configuration.

[Means for solving the problem]

As clearly shown in the embodiments described below, the present invention provides an auxiliary lighting device for providing a pattern image reflected by a target object to a focus detection unit, in which a plurality of stripe-shaped different patterns extending in the same direction are formed. It is characterized by comprising a light emitting means for simultaneously illuminating, and a light projecting lens having a plurality of optical axes for projecting the different patterns illuminated by the light emitting means so as to overlap each other on the target object.

〔Example〕

FIG. 7 shows a configuration in a case where the illumination device for distance measurement according to the present invention is employed in a known single-lens reflex camera.

In FIG. 7, 1 is a camera body, 2 is an objective lens 3
Lens barrel for holding the lens movably in the optical axis direction, a movable half mirror 4 for dividing the object light into a distance measuring system and a finder system, 5 a pentaprism, 6 a finder system together with an eyepiece 7 A focusing glass 8 is a movable mirror for guiding a light beam to a focus detection device 9. Reference numeral 10 denotes an auxiliary lighting device for distance measurement, which will be described later as an embodiment, which can be either built into a camera or detachable.

 First, an example of the periphery of the focus detection device will be described.

FIG. 8 shows a perspective view. Reference numeral 42 denotes a perforated field mask, which has long sides in the horizontal direction in the figure and has rectangular apertures arranged side by side, and is arranged, for example, in the vicinity of the planned imaging plane of the objective lens 3 in FIG. 43 is a filter that blocks light having a longer wavelength than near-infrared light. Reference numeral 50 denotes a split field lens, which is arranged slightly shifted from a predetermined image forming plane of the objective lens. The split field lens 50 includes lens portions 50c, 50d, and 50e having different optical functions, and these portions are formed by changing a design value of one or both of a lens thickness and a radius of curvature of a lens surface. When each lens portion is formed separately, it can be made of a material having a different refractive index.

51 and 53 form a re-imaging lens unit with a two-hole stop 52 interposed therebetween, and the convex lens 51 converts incident light into a state close to parallel light (optical action is described in JP-B-62-33564). 2 in which two convex lenses 53a and 53b are arranged and joined.
Two image forming lenses are formed. The above-described two-hole aperture 52 has vertically long elliptical apertures 52a and 52b arranged in the horizontal direction in the drawing.

54 is a concave lens for correcting curvature of field, a photoelectric conversion device
It is arranged on a transparent plastic package 56 containing 55. Although the split field lens 50, the convex lens 51 and the concave lens 54 of the re-imaging lens unit are shaped vertically long, each is a rotationally symmetric spherical lens system.

The light beams passing through the apertures 42b... 42f of the perforated field mask 42 pass through the lens portions 50c, 50d, and 50e of the divided field lens 50, and are respectively placed on a photoelectric conversion device 56 having three pairs of pixel rows (not shown). Is formed.

Two field mask images are formed side by side in one opening of the porous field mask 42 by the action of the aperture openings 52a and 52b and the lens portions 53a and 53b, and the position of the object image with respect to the predetermined image plane (object The secondary image of the object inside moves in the directions of the arrows A and B in association with the degree of lens focus). Therefore, since the relative intervals of the light amount distributions for the paired secondary images are detected based on the photoelectric conversion output, the focus state of the objective lens can be known at a plurality of distance measurement positions. That is, each pixel row of this focus detection device performs a focus detection of a so-called image shift method.

FIG. 9 is a diagram showing three distance measurement visual field positions of the focus detection device corresponding to the finder visual field. In the figure, 101 is a viewfinder field, and 102 to 104 are distance measurement fields. Here, the pixel rows of the photoelectric conversion device 56 are arranged in the long side direction of the distance measurement field of view, and have sensitivity to a luminance distribution in this direction, for example, a horizontal line.

1 and 2 are views for explaining the configuration of the illumination device for distance measurement. 1 (a) and 1 (b) are a side view and a top view of a lighting device for distance measurement, and FIG. 1 (c) is a front view of a light projecting lens which is a component thereof. In the figure, reference numeral 105 denotes an LED which emits light having a wavelength used for distance measurement, for example, 700 nm, 10
6 is a transparent package holding the LED 105, 107 is a pattern film on which a stripe-shaped light emitting pattern is formed, 108
Is a light projecting lens for guiding the LE light together with the dome 109 onto the object to be measured. The light projecting lens 108 has five lens units 108a, 108
b, 108c, 108d, and 108e and a holding unit 108f, and are configured to effectively illuminate the distance measurement target in the three distance measurement fields of the focus detection device described above. The lens units 108a and 108b constitute an on-axis illumination system, and the lenses 108c and 108d constitute an off-axis illumination system. FIG. 2 is a view for explaining the light projection pattern of the pattern film 107. At the center, there are pattern portions 107a, 107b and 107c in which stripe-shaped light transmitting portions and non-transmitting portions are alternately arranged. Pattern part 107a, 10
7b and 107c are distributions in which the spatial frequency region is stepwise different, 107a is a relatively high frequency pattern, 107c is a high frequency pattern, and 107b is an intermediate pattern that can include both. . Since this pattern film is usually made of a rib film or the like, it is a black and white pattern having no intermediate density.

Next, the operation of the lighting device having the above configuration will be described in the third.
This will be described with reference to FIGS. FIGS. 3A and 3B are diagrams for explaining the behavior of the light beam of the LED light, in which the power of the lens is replaced by an arrow. The directions in the figure correspond to FIGS. 1 (a) and 1 (b), respectively. In the figure, reference numeral 110 denotes equivalently the combined power of the dome 109 and the lens part 108e of the light projecting lens 108, 111 denotes its optical axis, and 112, 113, 122, and 123 denote the lens parts 108a, 108, respectively.
b, 108c, and 108d are optical axes. Note that reference numeral 114 denotes an object to be measured.

On-axis illumination system consisting of lens parts 108a and 108b and 108c and 108d
In both the off-axis illumination system, the light emitted from the LED 105 illuminates the object to be measured through the dome and the projection lens. At this time, a pattern film 107 having a white and black stripe pattern is arranged in the optical path, and forms an illuminance distribution on the object to be measured. The higher the contrast of the illuminance distribution, the better the distance measurement system. Therefore, the powers of the dome and the light projecting lens are adjusted so that the pattern film and the object to be measured have an almost image-forming relationship. Further, since the lens portions 108a and 108b of the light projecting lens 108 constituting the on-axis illumination system are eccentric in the vertical direction in FIG.
Since the points 112 and 113 are located above and below the optical axis 111, the points 115 and 116 of the pattern film are projected so as to overlap a point 118 on the object to be measured. At this point 115
Is in the center of the low frequency pattern portion 107a shown in FIG.
Point 116 is located at the center of high-frequency pattern portion 107c.
This is a point determined to enhance the use efficiency of each LED as described later. On the distance measurement target 114, these patterns are combined to form a complicated illuminance distribution, thereby preventing erroneous distance measurement. On the other hand, the lens unit 1 of the projection lens 108
Since the optical axes 122 and 123 of the luminous flux passing through 08c and 108d are eccentric in the vertical direction in the drawing of FIG. 3B, the point 117 on the pattern film 107 is measured as two off-axis points. Projected onto the object 114 to enable a wide range of illumination,
Point 117 is a point located at the center of the pattern film area 107b.

FIG. 4 and FIG. 5 show the above-described projection relationship in correspondence with the field of view of a 35 mm single-lens reflex camera.

FIG. 4 shows an example when the focal length of the taking lens 3 is approximately 100 mm, and FIG. 5 shows an example when the focal length is 35 mm. In the figure, 119
Indicates that the pattern portions 107a and 107c are the lens portions 108 of the projection lens 108.
a, a composite image projected on the on-axis distance measurement target 114 through 108b, 120 is an image in which the pattern portion 107b is projected off-axis through the lens portion 108c, 121 is a pattern portion 107b is the lens portion 108
This is an image projected off-axis through d. As described above, the size of the pattern image with respect to the finder field changes due to the difference in the focal length, but the three images 119, 120, and 121 continue to form a horizontally long illumination area as a whole, and the focus is independent of the focal length of the photographing lens. Three distance measurement fields 102, 10 of the detection device
It is configured such that a pattern is always projected in 3, 104. The image 119 has three levels of illuminance, which are indicated by a black background, a satin finish, and a white background.

In the above, the projection relation of the pattern has been mainly described. Next, the illuminance distribution will be described. First, since the on-axis image 119 formed by the lens portions 108a and 108b of the light projecting lens 108 is a composite image of the pattern portions 107a and 107c, the point 11 located at the center of each pattern
Focusing on the luminous flux passing through the lenses 5 and 116 and entering the lens portions 108a and 108b, as shown in FIG.
Emitted from the center of D105. Therefore, considering the illuminance distribution of the image, there is a brightest area including a point 118 conjugate with points 115 and 116, and an area around which the LED light does not effectively pass through the light projecting lens and becomes darker outward. It is formed. Furthermore, since the light emitted from the LED does not pass through the light projecting lenses 108a and 108b, the outside is an area where no light reaches at all. When such an illuminance distribution is superimposed on the optical axis 111, it can be seen that the two light amount centers and the optical axis 111 coincide on the object to be measured, and that an effective on-axis illumination system is obtained. In a camera lighting device, the virtual distance of the object to be measured is about 3 m, so that the angle at which the light beams emitted from the two lens units intersect on the axis is very small. Therefore, even if the distance of the object to be measured changes, it can be considered that the two illumination areas are practically overlapped.

The images 120 and 121 formed by the lens portions 108c and 108d of the light projecting lens 108 have an illuminance distribution centered on the light amount of the images of the points 124 and 125 shown in FIG. .

Here, let us consider the use efficiency of LED light. In this type of lighting device, the effective light emitting surface of the LED is one surface on the side of the light projecting lens, and in this example, FIGS. 1 (a), (b), 3 (a),
This is 105a shown in FIG. The light emitting surface 105a may be considered as a substantially perfect diffusion surface, and the utilization efficiency of the LED light is determined by how many light beams that go out in various directions are caught by the light projecting lens and guided to the object to be measured. In addition, the smaller the area of the required light emitting surface, the better in terms of technology and cost. In order to capture this thick light beam, it is conceivable to increase the numerical aperture of the projection system to make it brighter.
It is difficult to achieve both the focus on the pattern film and the requirement to reduce the size of the LED unless the values are matched. In this example, a light projecting lens with multiple optical axes is used to project different areas on the pattern film onto the object to be measured, thereby capturing light rays emitted at an angle greatly inclined from the LED light emitting surface. I have. As a result, it is possible to guide the luminous flux, which was not used conventionally, to the object to be measured.
It is possible to measure an object having a lower contrast.

Further, as a secondary effect of effectively using the light beam emitted obliquely from the light emitting surface 105a, an off-axis illumination system is configured using the light beam emitted almost straight from the light emitting surface 105a in the cross section of FIG. 3 (a). doing.

FIG. 6 is a diagram showing a pair of sensor array outputs in the focus detection device in the state shown in FIG. In FIG. 4, the same pattern is included in each of the distance measurement fields 102, 103, and 104, and the sensor output in this case is the same for the three pairs of sensor arrays. As described above, the pattern image 119 is a combination of two projection patterns having different frequency spectra, and the illuminance has approximately three levels. That is, the black level A, the intermediate level B due to either one of the lens portions 108a and 108b, and the high level C due to the light from both the lens portions 108a and 108b, which are not exposed to light. As a result, the projection pattern in consideration of the illuminance becomes extremely complicated, and a pattern with synchronization is hardly incident on the sensor. In general, an image shift type focus detection device is not good at periodic patterns, and sometimes outputs a focus signal with an image phase that is incorrect for one cycle. In this way, erroneous distance measurement is greatly reduced.

Furthermore, the fourth factor that the magnification at which the sensor captures the projected pattern image changes depending on the focal length of the taking lens.
This is shown using FIG. 5 and FIG. This means that if the frequency of the projection pattern is set in a specific narrow range, distance measurement cannot be performed depending on the focal length of the photographing lens. In other words, even if a high-frequency pattern is viewed through a short focus lens, the pattern is not reproduced as an output due to the limitation of the resolution of the sensor, or if a low frequency pattern is viewed through a long focus lens, a part of the pattern is enlarged, resulting in extremely low contrast. And so on. According to the present example, since two projection patterns having different frequency spectra are superimposed, such a problem does not occur, and the distance can be measured by photographing lenses having various focal lengths. In addition, since each projection pattern can be a high contrast pattern having no intermediate density, it can be easily manufactured and the cost can be reduced.

[Other embodiments]

FIGS. 10 to 12 show a second embodiment according to the present invention, in which the illumination area is limited to only the axis and the four lenses are modified to illuminate the same area on the object to be measured. . No.
In FIGS. 10 and 11, the numbers obtained by adding 1000 to the numbers in FIGS. 1 and 3 have almost the same action except for 1108c and 1108d.

The projection images formed by the lens units 1108c and 1108d are formed by overlapping the pattern unit 107b shown in FIG. 2 with a horizontal shift, and the projection image is formed by the same lens unit 1108 as shown in the first embodiment.
a, 1108b are further superimposed. As a result, for example, as shown in FIG. 12, the output of the focus detection device has an even higher illuminance level than in the first embodiment, and the rate of occurrence of a periodic pattern in the distance measurement field is further reduced.

In addition to the configuration described above, similar effects can be obtained in the following modifications.

(1) Print the light projection pattern on the LED package.
(2) The light projecting lens is a reflecting mirror. (3) The light projecting lens is a Fresnel lens. And so on.

〔The invention's effect〕

 As described above, the present invention has the following effects.

(1) Even a light beam emitted at a large angle with respect to the optical axis by the LED can be effectively guided to the object to be measured, and the utilization efficiency of the LED light is high.

Moreover, this is achieved without lowering the contrast of the projection pattern.

(2) A projection pattern having a complicated illuminance distribution can be formed, and erroneous distance measurement is prevented.

(3) By superimposing projection patterns having different spatial frequency spectra, it is possible to cope with photographing lenses having various focal lengths.

(4) Since the area of the light emitting portion of the LED is small, it is inexpensive.

[Brief description of the drawings]

1 (a) is a side view of the lighting device according to the present invention, FIG. 1 (b) is a top view of the lighting device according to the present invention, FIG. 1 (c) is a front view of the light projecting lens, and FIG. FIGS. 3 (a) and 3 (b) are optical path diagrams of an illuminating device, FIG. 4 is an explanatory diagram showing a relationship between a projection pattern and a field of view of a single-lens reflex camera, and FIG. FIG. 6 is an explanatory diagram showing a relationship with a field of view of a single-lens reflex camera, FIG. 6 is an explanatory diagram showing an example of a sensor output, FIG. 7 is a cross-sectional view of a single-lens reflex camera, FIG. FIG. 9 is an explanatory diagram showing the relationship between the viewfinder field and the distance measurement field of view, FIG. 10 (a) is a side view of the lighting device, FIG. 10 (b) is a top view of the lighting device, and FIG. 11 (a) and (b) are optical path diagrams of a lighting device, and FIG. 12 is an example of a sensor output. FIG. In the figure, 105 is a light source, 107 is a pattern film, 108 is a light projecting lens, 109 is a dome-shaped lens, 108a and 108b are on-axis light projecting lenses, 108c and 108d are off-axis light projecting lenses, and 107a is low. The frequency pattern 107c is a high frequency pattern.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-247312 (JP, A) JP-A-1-288717 (JP, A) JP-A-1-235911 (JP, A) JP-A-63-1987 32509 (JP, A) JP-A-62-191835 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02B 7/28 G03B 3/00

Claims (3)

(57) [Claims] An auxiliary lighting device for providing a pattern image reflected by a target object to a focus detecting means, a light emitting means for simultaneously illuminating a plurality of different stripe-shaped patterns extending in the same direction, and an illumination by the light emitting means. An auxiliary lighting device, comprising: a light projecting lens having a plurality of optical axes for projecting the plurality of patterns thus formed on the target object so as to overlap each other. 2. The auxiliary lighting device according to claim 1, wherein said light projecting lens is configured such that a brightness distribution is emphasized in a projection pattern. 3. The auxiliary lighting device according to claim 1, wherein said different patterns have different frequency ranges.