JP7594264B2 - 3D shape measuring device - Google Patents

Description

The present invention relates to a three-dimensional shape measurement device that uses the phase shift method.

Three-dimensional shape measuring devices using the phase shift method are known as devices for measuring the three-dimensional shape of an object without contact. In these three-dimensional shape measuring devices, a sinusoidally varying stripe pattern is projected onto the surface of the object by a projection unit and then photographed by an imaging unit, and the phase of the stripe pattern is sequentially shifted by a predetermined angle (e.g., π/2 or 2π/3) to obtain a set of photographed images (e.g., four or three). The set of photographed images is then processed to measure the three-dimensional shape of the object.

Here, the projection unit may be, for example, one that uses a projector as described in Patent Document 1, or one that uses a stripe pattern forming optical element that forms a stripe pattern by passing light from a number of light sources arranged in a row as described in Patent Document 2. Compared to the former, the latter is capable of high-speed projection of a phase-shifted stripe pattern, and also allows for lower power consumption and miniaturization.

JP 2008-281491 A JP 2011-242178 A

However, in the case of a device using multiple light sources as described in Patent Document 2, there are many cases where differences in the changes in the characteristics of the light sources occur between the light sources due to changes in the usage environment (for example, temperature changes while measuring multiple objects sequentially). Therefore, if differences occur between the light sources in the changes in the radiant intensity of the light, the errors in the measurement of the three-dimensional shape will increase.

The present invention was made in consideration of the above circumstances, and its purpose is to provide a three-dimensional shape measurement device that uses a plurality of light sources arranged in a row in a projection device and a stripe pattern forming optical element that passes the light from the light sources in a stripe pattern, which can prevent large errors in the measurement of three-dimensional shapes even if differences occur between the light sources in the changes in characteristics of the light sources due to changes in the usage environment.

In order to achieve the above-mentioned object, a three-dimensional shape measuring device according to an embodiment of the present invention comprises a projection control unit, a projection unit which has a plurality of light sources arranged in a row, each of whose lighting and light radiation intensity is controlled by the projection control unit, and a stripe pattern forming optical element which passes the light from the light sources in a stripe pattern, and which projects a stripe pattern onto an article, the phase of which is shifted by a predetermined angle sequentially by sequentially lighting each of the plurality of light sources, a photographing unit which photographs the article onto which each of the stripe patterns is projected to obtain a set of photographed images, and a three-dimensional shape measurement processing unit which performs image processing of the set of photographed images and has an illuminance sensor attached to the light source side in a peripheral portion of the stripe pattern forming optical element, and which detects changes in the light radiation intensity of each of the plurality of light sources from the illuminance detected by the illuminance sensor during sequential measurement of a number of the articles, and adjusts the light radiation intensity of each of the plurality of light sources so that it falls within a reference range , thereby measuring the three-dimensional shape of the article .

The three-dimensional shape measurement device of the present invention makes it possible to prevent errors in the measurement of three-dimensional shapes from becoming large even if differences in the changes in the characteristics of the light sources occur between the light sources due to changes in the usage environment.

1 is a plan view showing an outline of a three-dimensional shape measuring apparatus according to an embodiment of the present invention. 4 is a waveform diagram showing a simplified timing of projection and photography of the three-dimensional shape measuring device of the above embodiment. FIG. 1A shows the components that make up the projection unit in the above-mentioned three-dimensional shape measuring device, where (a) is a front view of multiple light sources, and (b) is a front view of a projection unit case that houses multiple light sources and a stripe pattern forming optical element. 4 is a circuit diagram of a plurality of light sources of a projection unit in the three-dimensional shape measuring device according to the embodiment of the present invention. 11A and 11B are planar cross-sectional views taken horizontally near the vertical center of a stripe pattern forming optical element in the above-mentioned three-dimensional shape measuring device, in which (a) is an example in which a plurality of transparent parts are formed in a regular stripe pattern, and (b) is an example in which a plurality of cylindrical lenses are formed in a regular pattern. 4 is a photograph showing an example of a set of images captured by the three-dimensional shape measuring device of the same embodiment; FIG. 13 is a plan view showing an outline of a modified example of the three-dimensional shape measuring device of the above. FIG. 13 is a front view of a projection unit case that houses a plurality of light sources and a stripe pattern forming optical element in a modified example of the three-dimensional shape measuring device of the above embodiment. 2 is a block diagram showing a three-dimensional shape measurement processing unit of the three-dimensional shape measuring device implemented by a computer. FIG.

The following describes an embodiment of the present invention. As shown in FIG. 1, a three-dimensional shape measuring device 1 according to an embodiment of the present invention includes a projection control unit 2, a projection unit 3, an image capturing unit 4, and a three-dimensional shape measurement processing unit 5. The three-dimensional shape measuring device 1 measures the three-dimensional shape of an object M using a phase shift method. Note that the solid lines (and dashed lines) with arrows between each unit in FIG. 1 (and FIG. 7) are schematic representations of each control signal, etc.

The projection control unit 2 controls the illumination and light emission intensity of each of the multiple light sources 31A, 31B, 31C, and 31D of the projection unit 3, which will be described later. The number of light sources is not particularly limited, but can be four or three, for example. In this embodiment, the number of light sources is four unless otherwise specified.

In detail, as shown in FIG. 2, the multiple light sources 31A, 31B, 31C, and 31D are sequentially supplied with currents I _A , I _B , I _C , and I _D (see FIG. 4 ) during a projection period Ta synchronized with a synchronization signal SY to emit light. The projection period Ta has a preset length. A PWM pulse current can be used to supply the current. The PWM period Tb has a preset length. The PWM pulse widths Tc _A , Tc _B , Tc _C , and Tc _D can be controlled for each of the light sources 31A, 31B, 31C, and 31D, and the wider the width, the higher the light emission intensity, and the narrower the width, the lower the light emission intensity. The projection period Ta is synchronized with an exposure period Td (signal EX in FIG. 2 indicates the timing of exposure) in the image capture unit 4. In addition, in FIG. 2, the period Tb and the pulse widths _TcA , _TcB , _TcC , and _TcD are shown enlarged for ease of understanding.

The projection unit 3 has multiple (four in this embodiment) light sources 31A, 31B, 31C, and 31D and a stripe pattern forming optical element 32. The multiple light sources 31A, 31B, 31C, and 31D and the stripe pattern forming optical element 32 can be housed in a projection unit case 33.

The light sources 31A, 31B, 31C, and 31D are arranged in a row (horizontally). Each of the light sources 31A, 31B, 31C, and 31D can be composed of a plurality of light-emitting elements 310 (six in this embodiment) arranged in a row in the vertical direction, as shown in FIG. 3(a). The light-emitting elements 310 are connected in parallel or series, or in a combination thereof, in terms of the circuit. For example, as shown in FIG. 4, all of the light sources 31A, 31B, 31C, and 31D can be connected in series.

In FIG. 4, reference numeral 311 denotes a resistor for limiting current. Reference numerals 31Aa, 31Ba, 31Ca, and 31Da denote current inflow terminals, and reference numerals 31Ab, 31Bb, 31Cb, and 31Db denote current outflow terminals. It is possible to combine multiple current inflow terminals 31Aa, 31Ba, 31Ca, and 31Da and current outflow terminals 31Ab, 31Bb, 31Cb, and 31Db into one common terminal.

The stripe pattern forming optical element 32 passes light from the multiple light sources 31A, 31B, 31C, and 31D in a stripe pattern. As shown in FIG. 3B and FIG. 5A, the stripe pattern forming optical element 32 has multiple transparent portions 32a formed in a regular striped (grid) pattern. The multiple transparent portions 32a pass light from the multiple light sources 31A, 31B, 31C, and 31D. The portions other than the multiple transparent portions 32a are shielding portions 32b that do not transmit light. In this embodiment, the stripe pattern forming optical element 32 is disposed close to the rear of the front surface of the projection unit case 33, and an opening 33a is formed in the front surface of the projection unit case 33. The light that passes through the multiple transparent portions 32a of the stripe pattern forming optical element 32 is radiated to the outside of the projection unit 3 through the opening 33a. In addition, in Figures 3(b) and 5(a) (and Figure 8), the shielded portion 32b of the stripe pattern forming optical element 32 is painted black to make it easier to understand.

In addition to the stripe pattern forming optical element 32 having a plurality of transparent portions 32a formed in a regular stripe pattern, it is also possible to use one having a plurality of cylindrical lenses 32c formed in a regular pattern as shown in FIG. 5(b). Each of the plurality of cylindrical lenses 32c is a convex lens that refracts and focuses light and radiates it to the outside. As a result, the light that passes through this stripe pattern forming optical element 32 becomes a stripe pattern. In a stripe pattern forming optical element 32 having such cylindrical lenses 32c formed therein, all light is transmitted, so the amount of light radiated can be increased.

In this type of projection unit 3, multiple light sources 31A, 31B, 31C, 31D are sequentially turned on to project stripe patterns P1, P2, P3, P4 onto the object M, the phase of which is sequentially shifted by a predetermined angle. The stripe patterns P1, P2, P3, P4 emitted from the projection unit 3 have light radiation intensity that changes in a sinusoidal manner. In this embodiment, the predetermined angle of the phase shift is π/2. If there are three light sources, the angle becomes 2π/3.

The projection unit 3 operates by simply sequentially lighting up multiple light sources 31A, 31B, 31C, and 31D, allowing for high-speed projection of a phase-shifted stripe pattern and enabling low power consumption and compact size. This compact size allows the projection unit 3, together with the image capture unit 4 described below, to be easily housed in a single housing 1a, as shown in Figure 1. Note that in Figure 1, the projection control unit 2 and 3D shape measurement processing unit 5, which are not housed in the housing 1a, are shown in block diagram form.

The photographing unit 4 photographs the object M onto which each of the stripe patterns P1, P2, P3, and P4 is projected, to obtain a set of photographed images as shown in Figs. 6(a) to (d). If the background of the object M (for example, the platform M' on which the object M is placed) is flat, each of the stripe patterns P1, P2, P3, and P4 projected onto the background will have a certain regularity. Each of the stripe patterns P1, P2, P3, and P4 projected onto the object M (a gable-shaped object in Figs. 6(a) to (d)) will be distorted. In this embodiment, there are four photographed images in one set. If there are three light sources, there will be three photographed images.

The three-dimensional shape measurement processing unit 5 performs image processing on the set of captured images. In the three-dimensional shape measurement processing unit 5, the distortion of each of the stripe patterns P1, P2, P3, and P4 projected onto the item M is phase analyzed, thereby measuring the three-dimensional shape of the item M.

The three-dimensional shape measurement processing unit 5 also detects changes in the radiation intensity of the light from each of the multiple light sources 31A, 31B, 31C, and 31D.

In detail, the three-dimensional shape measurement processing unit 5 can detect the change in the light emission intensity of each of the multiple light sources 31A, 31B, 31C, and 31D from the brightness of a predetermined position of each of the captured images in a set of captured images. For example, the predetermined position can be a part of the background of the item M (e.g., the platform M' on which the item M is placed) that is not affected by the item M (i.e., regardless of the presence or absence of the item M) (e.g., the part surrounded by squares indicated by symbols p1, p2, p3, and p4 in FIG. 6).

Alternatively, as shown in Figs. 7 and 8, the three-dimensional shape measurement processing unit 5 has an illuminance sensor 51, and can detect changes in the light radiation intensity of each of the multiple light sources 31A, 31B, 31C, and 31D from the illuminance detected by the illuminance sensor 51. For example, the illuminance sensor 51 can be attached to the light source side in a peripheral portion (part of the shielding portion 32b) such as the upper or lower portion of the stripe pattern forming optical element 32, although this is not particularly limited (see Figs. 7 and 8).

When the three-dimensional shape measurement processing unit 5 detects a change in the radiation intensity of each of the multiple light sources 31A, 31B, 31C, and 31D, it prevents large errors in the measurement of the three-dimensional shape of the item M in the following manner.

That is, the three-dimensional shape measurement processing unit 5 adjusts the light radiation intensity of each of the multiple light sources 31A, 31B, 31C, and 31D via the projection control unit 2 (see the dashed line with an arrow from the three-dimensional shape measurement processing unit 5 to the projection control unit 2 in Figures 1 and 7). For example, when the light radiation intensity of the light sources 31A, 31B, 31C, and 31D decreases during sequential measurement of a large number of objects M and the degree of decrease differs between the light sources, the light radiation intensity of each of the multiple light sources 31A, 31B, 31C, and 31D can be adjusted to fall within a reference range. The reference range is a range that is determined in advance at the time of calibration or the like, and may be the same for the multiple light sources 31A, 31B, 31C, and 31D, or may be a different range if brightness correction is performed during image processing in the three-dimensional shape measurement processing unit 5. The reference range may be determined by absolute values or by relative values between the light sources.

Alternatively, the 3D shape measurement processing unit 5 can adjust the exposure time (length of exposure period Td in FIG. 2), aperture value, or gain in the imaging unit 4 (see the dashed line with an arrow pointing from the 3D shape measurement processing unit 5 to the imaging unit 4 in FIG. 1 and FIG. 7).

Alternatively, the 3D shape measurement processing unit 5 can also adjust (correct) the brightness of a set of captured images.

Specifically, the three-dimensional shape measurement processing unit 5 can be realized by a computer that is composed of a CPU 5a, a program memory 5b, a work memory 5c, an input/output interface 5d (input/output terminals are omitted in FIG. 9), etc., as shown in FIG. 9. The program memory 5b can store an image processing program 5ba that performs image processing, and a detection adjustment program 5bb that detects changes in the radiation intensity of each of the multiple light sources 31A, 31B, 31C, and 31D and adjusts them as described above.

In this way, the three-dimensional shape measuring device 1 can prevent large errors in the measurement of the three-dimensional shape of the object M even if differences occur in the changes in the characteristics of the light sources 31A, 31B, 31C, and 31D due to changes in the usage environment (for example, temperature changes during sequential measurement of multiple objects M).

The above describes a three-dimensional shape measuring device according to an embodiment of the present invention, but the present invention is not limited to the embodiment described, and various design modifications are possible within the scope of the matters described in the claims.

REFERENCE SIGNS LIST 1 Three-dimensional shape measuring device 1a Housing 2 Projection control unit 3 Projection unit 31A, 31B, 31C, 31D Light source 31Aa, 31Ba, 31Ca, 31Da Current inflow terminal 31Ab, 31Bb, 31Cb, 31Db Current outflow terminal 310 Light emitting element 311 Resistor 32 Stripe pattern forming optical element 32a Transmitting portion 32b Shielding portion 32c Cylindrical lens 33 Projection unit case 4 Imaging unit 5 Three-dimensional shape measurement processing unit 5a CPU
5b Program memory 5ba Image processing program 5bb Detection adjustment program 5c Work memory 5d Input/output interface 51 Illuminance sensor EX Signal indicating timing of exposure I _A , I _B , I _C , I _D Current flowing through light source M Article M' Stand P1, P2, P3, P4 Stripe pattern p1, p2, p3, p4 Part of captured image showing stripe pattern SY Synchronization signal Ta Projection period Tb PWM period Tc _A , Tc _B , Tc _C , Tc _D PWM pulse width Td Exposure period

Claims (1)

A projection control unit;
a projection unit having a plurality of light sources arranged in a row, each of which is controlled by the projection control unit in terms of its lighting and light radiation intensity, and a stripe pattern forming optical element that passes the light from the light sources in a stripe pattern, and which projects a stripe pattern onto an article, the phase of which is shifted by a predetermined angle by sequentially lighting each of the plurality of light sources;
an imaging unit that captures an image of the object onto which each of the stripe patterns is projected to obtain a set of captured images;
a three-dimensional shape measurement processing unit that performs image processing on the set of captured images, and has an illuminance sensor attached to the light source side in a peripheral portion of the stripe pattern forming optical element, and detects a change in the radiant intensity of light from each of the plurality of light sources from the illuminance detected by the illuminance sensor during sequential measurement of the multiple objects , and adjusts the radiant intensity of light from each of the plurality of light sources so that it falls within a reference range ;
and measuring a three-dimensional shape of the object .

Images